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Developments in Power Systems Protection, 2012. DPSP 2012. 11th International Conference on

Date 23-26 April 2012

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Displaying Results 1 - 75 of 144
  • Front cover

    Publication Year: 2012 , Page(s): c1
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  • Table of contents

    Publication Year: 2012 , Page(s): 1 - 12
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  • The directional reactive power undervoltage protection — A protection concept for connecting decentralized renewable energy sources

    Publication Year: 2012 , Page(s): 1 - 5
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (522 KB)  

    With their increasing number, it is getting important that decentralized and renewable energy sources are supporting the stabilization of the system voltage after short voltage dropouts. Often, in the past, these generators were disconnected during network faults. This is not adequate anymore, as it would lead to a loss of a considerable amount of feed-in power. However, if the generators stay connected, it must be ensured that they are not receiving reactive power, as this would lead to a collapse of the grid. In Germany, a number of legal requirements and grid codes are regulating the connection of such generators. These documents also stipulate the use of Directional Reactive Power Undervoltage Protection (Q→& U< protection) that would disconnect such energy sources if they received reactive power during faults on the network. This paper gives an overview about the legal documents and an introduction to the protection function mentioned above. The basic principle of the Q→& U< protection is explained by means of its requirement specifications. Furthermore, the paper will show up standardized test methods evaluating the Q→& U< protection. It will describe how to test the releasing functions, the reactive power direction determination and also all binary inputs and outputs that are necessary for the protection function. View full abstract»

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  • Distributed energy resources — Testing issues

    Publication Year: 2012 , Page(s): 1 - 5
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (554 KB)  

    Decentralized Energy Resources (DER) and especially wind farms became a challenge for protection, automation and control in the grids. Transmission system operators as well as distribution system operators require tests of Loss of Mains and other decoupling protection functions. In some countries certification of these functions is required. The units are equipped with a huge amount of internal protection functions as well as controls. This requires tests during commissioning or in service. This paper figures out main strategies and approaches for protection and explains testing using current examples. It is focussing on developments in Germany with a huge amount of wind farms but also covers regulations and methods from other countries. An outlook summarizes the issues and proposes future steps. View full abstract»

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  • Voltage control of distribution networks with distributed generation

    Publication Year: 2012 , Page(s): 1 - 6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (149 KB)  

    Effective voltage control is essential for the satisfactory operation of distribution networks. The increased connection of distributed generation to existing distribution networks challenges the current methods of controlling network voltages. Network voltage is primarily controlled by changing tap position of the primary transformers. The transformer secondary voltage will be automatically increased at times of high demand to compensate the voltage load drop. The experience of distribution network operators is that it can be difficult in practice to apply load drop compensation to primary substations with multiple feeders of disparate load profiles. The resultant compromise setting often results in a high network voltage, which may restrict the export from distributed generation connected to that substation. This paper presents an innovative solution to overcome this problem. In this method of voltage control, optimized compensation voltage is achieved using local current and voltage quantities based on feeder models. The effectiveness of the method is validated by comparison with traditional AVC control scheme. The results show that the new voltage control method allows an appropriate voltage level at substation that both complies with the statutory limits and leave more margins for connection of distributed generation. View full abstract»

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  • Demonstration of energy management system for smart grids

    Publication Year: 2012 , Page(s): 1 - 6
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    The increasing integration of distributed and renewable energy sources into the electrical power network presents challenges for the operation and management of the network. New techniques are required to ensure the effective management of the balance between supply and demand, and the proper maintenance of voltage stability and power quality in the network. A new energy management system, designed specifically for the management of smart grids, is described, and its operation in conjunction with energy storage systems is explored. Large scale demonstration systems have been implemented in order to study and prove the new techniques, the configurations and results of which are recorded. The experience gained from the demonstration systems will result in improvements to the new techniques and consequent benefits for the future management of electrical networks. View full abstract»

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  • Smart Grids rely on relays

    Publication Year: 2012 , Page(s): 1 - 4
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    The quest for intelligent, so called Smart Grid technology is seen by many as the key to future exploitation of renewable energy sources and the inclusion on the Grid of home grown generation from micro CHP systems. But, as Keith Hamilton, Group Managing Director of PBSI Group Limited explains, the prerequisite for the establishment of Smart Grids relies on a significant investment in equipment as humble as protection relays. View full abstract»

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  • Voltage control on unbalanced LV networks using tap changing transformers

    Publication Year: 2012 , Page(s): 1 - 6
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (293 KB)  

    This paper investigates how an on-load tap changer (OLTC) can be used to regulate the unbalanced three-phase voltages when single phase unbalanced loads are connected to a radial LV distribution feeder. An overview of current voltage regulation technologies for distribution network is presented. Two voltage regulation strategies are developed to eliminate the effect of the unbalanced single phase loads and provide a balanced three-phase supply for the downstream loads. In PSCAD, these two strategies are modelled and examined in several scenarios, based on which, a comparison between their performances is given. View full abstract»

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  • Communication networks for domestic photovoltaic based microgrid protection

    Publication Year: 2012 , Page(s): 1 - 6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (402 KB)  

    Domestic photovoltaic (PV) based microgrid refers to a distributed group of small solar PV systems installed at each household in a residential area. The distributed systems may be integrated to form a meshed microgrid structure which can operate in both islanded and grid-connected modes. Grid-connected microgrids of domestic solar PV systems can supplement energy needs of homeowners. They are a potentially viable option for implementing demand side management programs for curbing peak demand. Nevertheless, PV based microgrids like other microgrid technologies are notorious of destabilising the national grid when running in grid-connected mode. They introduce current transient problems, voltage and frequency mismatch, etc. Hence solid control and protection scheme is necessary. The backbone of any control and protection scheme is a communication network. Thus the principal aim of this paper is to investigate feasibility of using wireless fidelity (Wi-Fi) for a metropolitan area network (MAN) of intelligent electronic devices (IEDs) used in meshed network architecture of a microgrid. Supervisory control and data acquisition applications were traditionally based on powerline carrier (PLC) networks. Due to the meshed structure of the proposed network, this approach would dearly complicate the network as devices such as signal traps and PLC modules would need to be installed on the many buses of the network. Thus a wireless network such as Wi-Fi is a flexible and simpler solution. As an added advantage, Wi-Fi will allow fault location identification through use of triangulation methods. However, issues such as security and interference proneness of the Wi-Fi protocol need to be considered. View full abstract»

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  • An efficient dynamic control of modern renewable distributed generators for intentional islanding operation

    Publication Year: 2012 , Page(s): 1 - 6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (807 KB)  

    This paper presents a new power controller for inverter-based renewable power generators, which is based on direct power control of active and reactive power. The controller included fast PLL and ROCOF units in order to function in both grid-connection and islanding operations. The controller's performance was tested by detailed computer simulation of a 2MVA renewable power generator with a DC-link energy storage bank. Application tests were carried out within a 20kV primary feeder in parallel with a 0.91MVA diesel generator for different control-modes, in both grid-connection and intentional islanding operations. Transient performance tests, when transferring from grid-connection to islanding and back to grid-connection, demonstrated a seamless effect of control-mode transfer on the distribution network. View full abstract»

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  • New type of protection and control method for smart distribution grid

    Publication Year: 2012 , Page(s): 1 - 5
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (214 KB)  

    Considering future smart distribution grid (SDG), the protection and control technology of traditional distribution networks is facing new opportunities and challenges. This paper proposes a Multi-Agent System (MAS) based protection and control method for smart distribution grid. The MAS is consist of intelligent distributed terminal (IDT), control master and communication network. Each IDT is regarded as single agent. By information interaction, the IDT is able to fulfill protection, fault location, fault isolation, network reconfiguration, power supply restoration and diagnosis functions. The first part of this paper introduces the structure of SDG, the structure of IDT and the structure of MAS. The second part discusses in detail the new protection method, fault isolation method and supply restoration strategy. In the new protection scheme, the combination of current differential protection and fast current protection is used as main protection. The protection algorithm and operation logic among different agents are analyzed in detail. To evaluate the proposed protection method, the EMTDC based simulation is carried out, which includes modeling of 10kV distribution network with distributed generation (DG), faults simulation on the model and results analysis. The simulation results show that the new protection method is feasible, and the new protection algorithm is correct. The simulation related content is reported in the last part of this paper. View full abstract»

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  • A transmission utility's experience to date with feeder unit protection systems

    Publication Year: 2012 , Page(s): 1 - 6
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    This paper investigates a number of design, operation and lifetime management experiences of feeder unit protection systems installed on National Grid Electricity Transmission (NGET) UK networks. The paper will consider the policy, application design and operational experiences under the following categories in particular since the move to numeric protection: Policy and application design SDH communication networks Operational experience to date Maintenance and post commissioning support Application of future current differential protection Future IEC61850 application GPS synchronised feeder current differential protection has been installed on NGET UK networks since early 2000. This paper highlights a number of problems and solutions of this type of protection, particularly NGET's experiences in the performance of GPS receivers. Finally NGET's application policy for future installation of feeder unit protection is also discussed. View full abstract»

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  • A transmission utility's experience to date with transformer protection systems

    Publication Year: 2012 , Page(s): 1 - 6
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    This paper investigates a number of design, operation and lifetime management experiences of transformer protection systems installed on National Grid Electricity Transmission (NGET) networks. The paper will consider the policy, application design and operational experiences under the following categories particularly since the move to numeric protection: Policy and application design Operational experience to date A bespoke transformer protection scheme solution Maintenance and post commissioning support Examples of protection mal-operations during transformer energisation are discussed in the paper. A bespoke transformer overall protection scheme is presented for application of the scheme on a transformer banked with a long cable circuit (> 5km). View full abstract»

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  • IEC 61850 testing in edition 2 — A systematisation

    Publication Year: 2012 , Page(s): 1 - 4
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (289 KB)  

    Since IEC 61850 became the widely used standard for substation communication with a lot of implementations. Testing is an important issue. The standard in its current version covers some possibilities and approaches for testing in general and for measures of performance. Nevertheless some issues came out which needed to be clarified with the new edition of the standard. Edition 2 will be available in 2012 and offers much more possibilities and sophisticated details. Due to the huge amount of prospects and different places where testing can located and marked systematization might be helpful. Test bits, test quality, test indications, test mode and test behavior will be practically explained. Ongoing projects with the usage of Sampled Values and GOOSE raise other questions. Distinguishing between "real" and "simulated" signals is a requirement, the possibilities for that will be described in this paper as well. The standard tries to summarize all these issues in a quite complex table with additional remarks. The paper looks beyond this table and explains possible scenarios for testing client-server-communication for SCADA purposes as well as GOOSE and Sampled Values. Experiences in current implementations will be presented as well as an outlook on advanced concepts to be used in substations according to IEC 61850 Edition 2. View full abstract»

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  • IEC60255–121: The new standard for type-testing distance relays: Are the proposed tests feasible and is it worth the effort?

    Publication Year: 2012 , Page(s): 1 - 5
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (190 KB)  

    The paper presents a brief overview of the standard IEC60255–121 and focusses on the challenges and advantages of using transient simulation for assessing protective relays. The importance of the use of statistical methods to investigate the behaviour of algorithms is discussed. Finally a new solution for performing these kinds of tests is introduced. View full abstract»

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  • High-resistance grounding fault detection and location in DC railway system

    Publication Year: 2012 , Page(s): 1 - 5
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (222 KB)  

    Locating high-resistance grounding faults poses a tough and challenging problem for the safety of DC railway systems. High-resistance grounding fault current isn't sufficient to trigger switches, which may expand the accident or turn into potential hazards. In order to overcome the limits of the existing methods (such as signal injecting method, resistance method and so), developing a novel fault approach by using both the feeding current and voltage to detect and locate the high-resistance grounding fault in DC railway traction system is necessary. The simulation results prove that the exact fault location can be accurately predicted in this way. Through comparison of several different analysis methods, this paper concludes that with the digital signal processing the location can be executed more precisely. Extensive simulations with diverse fault conditions are performed to verify the means. View full abstract»

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  • Operation and design of a protection relay for transformer condition monitoring

    Publication Year: 2012 , Page(s): 1 - 6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (197 KB)  

    Transformers are critical to the successful operation of the electrical power systems. Their reliability and availability is therefore key to flawless and optimum power generation and transmission. Effective condition monitoring is essential to evaluate transformer performance and safe operating conditions. Over the past few years many stand-alone devices have been developed for transformer condition monitoring. However, modern protection relays can offer an economic solution for condition monitoring as well as providing the required protection functionality and integration into the control system. This paper describes the operation and design of a transformer protection relay that includes many of the common transformer condition monitoring features required. The paper also discusses the standard ancillary features of the protection relay such as the flexible industry standard communications options, such as IEC 61850 over Ethernet, allowing easy integration in the network control system and programmable scheme logic providing easy logic customization as well as the user friendly event and disturbance recording features that can help diagnosing faults. View full abstract»

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  • Network rail and IEC 61850, a user's perspective of the standard

    Publication Year: 2012 , Page(s): 1 - 5
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    IEC 61850 is a standard that is now gaining pace within the Electrical Supply Industry and one that is under scrutiny by Network Rail. One of the key advantages offered by IEC 61850 is interoperability based on the fact a standard communications interface is implemented between substation devices. This allows the manufacturer to diversify specific functionality whilst allowing communication with other devices. View full abstract»

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  • Assessment of transformer relay algorithms and settings in laboratory using transient simulation data

    Publication Year: 2012 , Page(s): 1 - 6
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    This paper presents an analysis of the main operating conditions that may lead to inappropriate differential protection operation. These conditions were simulated using the Alternative Transients Program (ATP) and the model of a real system. The saturable transformer was the main component of the ATP/EMTP simulations. The saturation and hysteresis effects are represented by a non-linear model of the magnetizing inductance. The results of several ATP/EMTP simulations of normal and fault conditions were converted into COMTRADE format files. These files were used to verify the performance of relays in low-voltage laboratory tests, using various relay settings. View full abstract»

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  • Overall differential protection for pump storage power plant with tapped-delta design of the unit transformer

    Publication Year: 2012 , Page(s): 1 - 6
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    Every pump storage hydro power plant has at least three different operating modes of the synchronous machine which can cause possible challenges during the design of the plant protection scheme. These three operating modes are generating mode, pumping mode and machine starting into pumping mode. The main differences between the generating and pumping operating modes are changes in direction of the synchronous machine rotation and change of direction (i.e. sign) of the active power flow. This rotation direction change is achieved by so-called phase reversal disconnect switches. These disconnect switches simply swap two phases in pumping mode in order to reverse the phase sequence to the synchronous machine. However, the physical location of the phase reversal disconnect switches can be crucial for proper design of some protection functions (e.g. overall differential protection 87O) for the generator/motor-transformer unit. For this particular installation, phase reversal disconnect switches 89G and 89P are located in-between the low-voltage bushings of the unit transformer and the synchronous machine (see Figure 1 for more details), thus within the protection zones of the overall differential relay 87O. Machine starting into pumping mode of operation is specific for every pump storage power plant. In this particular station, machine is started as an asynchronous motor by using direct-on line starting method with reduced voltage. Voltage reduction is obtained by a special design of the unit transformer. So-called tapped-delta design, of the unit transformer secondary delta winding, is used (see Figure 2). View full abstract»

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  • New algorithm for determination of faulty feeder in distribution network

    Publication Year: 2012 , Page(s): 1 - 6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (326 KB)  

    This paper presents a novel approach designed for centralize substation level protection to determine the faulty feeder in a distribution network In opposite to phase-to-earth faults in the transmission networks (HV), which neutral points are solidly earthed, fault-loops in a fault-to-earth case in MV distribution networks have big impedance. Additionally during the earth-fault the transient component which provides very fast information about the disturbance in the system appears. Such signals consist of different frequency components, which result from charging or discharging of the network capacitances. From all of this reasons, detection of earth-fault and determination of a faulty feeder at a bus-bar with many outgoing feeders arises serious problems. In this paper a new approach which utilized a polarity changes between fundamental frequency component of zero sequence current and a voltage directly after the fault inception is presented. The described algorithm is designed for centralize substation level protection and therefore utilized the zero sequence bus-bar voltage and residual currents from all feeders. Provided simulation experiments in ATP/EMTP software package confirms the effectiveness of the proposed technique for selection a faulty feeder during phase-to-earth fault in different networks (directly or solidly earthed; network earthed through impedance; isolated network), and under different fault scenarios — different fault inception angles, including random mechanism and higher fault resistances. View full abstract»

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  • Development of stability protection framework in Oman electricity transmission system

    Publication Year: 2012 , Page(s): 1 - 6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (705 KB)  

    This paper discusses potential extreme scenarios which could result in unstable conditions on the main interconnected electricity transmission system of Oman. Case studies on loss-of-stability scenarios between different parts of the network are examined. The objectives of the study are to identify possible locations of the electrical centre of swing and to develop an approach for controllable system splitting. A controllable splitting approach has been proposed and sensitivity analysis has been utilised to identify potential locations for controllable system splitting. In the final recommendations, trade-off considerations should compare the introduction of a system-wide out-of-step protection framework and its associated potential complications versus alternatives (e.g. improved protection performance). View full abstract»

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  • Novel unit protective relaying techniques for teed circuit based on sequential overlapping derivative transform

    Publication Year: 2012 , Page(s): 1 - 6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (236 KB)  

    This paper presents a novel protective concept for EHV Three-terminal transmission line, teed circuit. The proposed protective relaying techniques use the fourth sequential overlapping derivative, SOD, concept at all line terminals. The SOD signals represent the transient components initiated due to fault occurrence. Such signals are free of both dc and fundamental components. Two protective relaying techniques are proposed here. The first applies the SOD to current signals only at all relay locations. As soon as these signals exceed a predetermined threshold limit, a discriminator compares their polarities to determine whether the fault is internal or external. The comparison is done by examining the polarities similarity/dissimilarity at the three terminals. The other applies the SOD to both current and voltage signals. The multiplier of the produced transient components is used as a relaying signal. Polarity of the initial change of such relaying signal is an indicator of fault direction. Negative polarity indicate forward fault direction while positive polarity indicate backward fault direction. Exchanging data between relaying stations using a suitable communication channel enable us to discriminate between internal and external faults and send a tripping signal to the prober circuit breakers. Testing and evaluation of the proposed protective techniques has been performed with fault data obtained from comprehensive ATP simulations. The simulation results confirmed that the proposed techniques have high reliability for internal faults and do not mal-operate for external faults and load switching conditions. The suggested techniques overcome most problems facing the other protective techniques such as synchronization between the three relaying stations, CT saturation compensation. Also they are not affected by the distributed shunt capacitance of the long line and they offer very simple detection method that can easily be practically implemented. View full abstract»

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  • Application of a subharmonic protection relay

    Publication Year: 2012 , Page(s): 1 - 6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (559 KB)  

    With the increased use of renewable wind energy, wind farms are being built in remote areas, often far from load centers. The required long transmission lines are often constructed with series capacitive compensation to electrically shorten the lines. Events in the transmission system can cause interactions between the series capacitors and the system's inherent impedance which can result in sub-synchronous resonance frequencies. Modern wind turbine systems use advanced electronic control and converter systems which can generate harmonics and inter harmonics. Mechanical system interactions (tower-toblade) can also generate sub-harmonics. Wind generator speeds vary continuously depending on the availability of wind at any particular time. This particular operating characteristic of wind farms introduces the challenge of predicting when and how much harmonics and sub-harmonics are being introduced to the power system. Synchronous generators are often built with shaft torsional modes that are in the same range as system sub-synchronous resonance frequencies. These torsional modes can interact with transmission network resonances to produce damaging oscillations that can damage generators and transformers, and cause damage at points of common coupling in the electrical grid. This paper discusses an engineering process that can be followed for the application of a new sub-synchronous relay that provides protection for transmission lines, particularly those with serial compensation and wind farm interconnections, and how it can be used together with digital fault recorders to monitor the power system to determine the existence of sub-synchronous resonance phenomenon. Moreover, it gives the reader criteria to determine if the levels of SSR obtained by means of DFRs are considered critical. The paper goes further, providing possible settings for the sub-harmonic protection relay including the protection elements associated to sub-harmonics as well as providing overcurrent- and other protection functions. View full abstract»

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  • A novel distance protection algorithm in frequency domain based on parameter identification

    Publication Year: 2012 , Page(s): 1 - 6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (250 KB)  

    In this paper, a novel distance protection algorithm in frequency domain is introduced. Based on the R-L model of transmission lines, this algorithm is derived from the linear equations which are obtained in fault condition network and O-module network for single-phase-to-earth fault. Considering that transformers usually ground directly in high voltage power systems, a linear equation with three coefficients is deduced based on the inductive O-sequence system impedance. Theoretical analysis and simulation results prove that the algorithm is accurate when faults happen at the remote terminal and it will get a positive fault distance error when faults happen around the remote terminal. This phenomenon shows that the algorithm effectively prevents overreach action of distance relays. Meanwhile, this algorithm has a high ability of anti-resistance and is expected to form a new distance protection. View full abstract»

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  • Synchrophasors — Can we use them for protection?

    Publication Year: 2012 , Page(s): 1 - 6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (474 KB)  

    The paper describes the concept of synchrophasors and the introduction of synchrophasors for protection applications in IEEE PC37.118.1 and then discusses different substation and transmission line protection applications. Requirements for reporting rate, time synchronization and communications architecture are discussed. Testing of protection systems based on PMUs is described at the end of the paper. View full abstract»

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  • A novel algorithm for differential protection of untransposed transmission line using synchronized measurements

    Publication Year: 2012 , Page(s): 1 - 4
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (702 KB)  

    Although there has been a practice of transposition of transmission lines, most of the real life EHV/UHV lines are untransposed. The distance protection of such lines becomes very complicated. With the advent of Global Positioning System (GPS) and Fiber optics technology, current differential protection can be a better choice for such lines. This paper proposes current differential protection scheme for protection of untransposed transmission lines based on equivalent-π line model. The proposed differential relay basically works on difference of currents in series branch (computed) from equivalent-π line model. As the measurements are time synchronized, the performance of relay is immune to line charging current. The analysis has been carried out in phase coordinates. ATP/EMTP programs have been used to simulate system disturbance and algorithm is implemented MATLAB. The result shows the efficacy and robustness of proposed algorithm. View full abstract»

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  • Out of step detection using synchronized swing impedance and resistance measurement

    Publication Year: 2012 , Page(s): 1 - 4
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (285 KB)  

    Distance relays used for transmission line protection can mal-operate on power swing. This paper presents protection schemes for out of step detection based on synchronized phasor measurement. Voltages and currents at both the ends of a transmission line are used to derive the parameters required for designing these schemes. The proposed schemes can distinguish stable and unstable power swing and can prohibit tripping of distance relays on stable power swings. The schemes are also compared with conventional power swing detection schemes. Simulations are carried out on single machine infinite bus system (SMIB) using PSCAD. View full abstract»

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  • Effect of fault resistance and grid short circuit MVA on impedance seen by distance relays on lines fed from wind turbine generating units (WTGU)

    Publication Year: 2012 , Page(s): 1 - 6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (375 KB)  

    This paper deals with line protection challenges experienced in system having substantial wind generation penetration. Two types of WTGU: Doubly Fed (DFIG) and Squirrel Cage (SCIG) Induction Generators are simulated and connected to grid with single circuit transmission line. The paper summarizes analytical investigations carried out on the impedance seen by distance relays by varying fault resistances and grid short circuit MVA, for the protection of such transmission lines during faults. The results are also compared with systems having conventional synchronous machine connected to the grid. View full abstract»

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  • Directional relays for distribution networks with Distributed Generation

    Publication Year: 2012 , Page(s): 1 - 6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (275 KB)  

    Due to its current limitation, Inverter-interfaced Distributed Generation (IIDG) is supposed to have little impact on protection system of distribution networks. However, in case of high power IIDG, the situation could be changed. This paper aims to show situations in which IIDG could provoke false tripping to overcurrent protections along distribution feeders. Proposed solution is to provide directional function to these protections. This function is based on local algorithms and does not require voltage sensors (to reduce the cost). Another part of this work is to implement the method of symmetrical components in grid with presence of IIDG. View full abstract»

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  • Assessment of the reliability of loss of mains protection incorporating satellite communications

    Publication Year: 2012 , Page(s): 1 - 6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (353 KB)  

    This paper builds upon the earlier research which proposed the use of satellite communication media to achieve improved performance of the Loss-Of-Mains (LOM) protection by eliminating nuisance tripping and ensuring reliable islanding detection. The focus of this paper is the practical development of the laboratory based trial of the satellite based LOM protection and the experimental assessment of the performance of such protection scheme. View full abstract»

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  • Impact of synthetic inertia from wind power on the protection/control schemes of future power systems: Simulation study

    Publication Year: 2012 , Page(s): 1 - 6
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (382 KB)  

    Future power systems face several challenges; one of them is the use of high power converters that decouple new energy sources from the AC power grid. This decreases the total system inertia affecting its ability to overcome system frequency's disturbances. The wind power industry has created a controller to enable inertial response on wind turbines generators: Artificial, Emulated, Simulated, or Synthetic Inertial. This paper deals with issues related to the synthetic inertia of wind turbines based on full-converters and their effect on the frequency protection/control schemes during the recovery period after system frequency disturbances happen. The main contribution of this paper is to demonstrate (based on simulations) the recovery period of under-frequency transients on future power systems which integrate wind turbines with synthetic inertia capability not completely avoid worse scenarios in terms of under-frequency load shedding. The extra power delivered from a wind turbine during frequency disturbances can substantially reduce the rate of change of frequency providing time for the active governors to respond. However, synthetic inertia might not completely avoid under-frequency load shedding. View full abstract»

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  • A multi-state model for assessing the impact of insufficient Wide-area Situational Awareness

    Publication Year: 2012 , Page(s): 1 - 6
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (280 KB)  

    Wide-area Situational Awareness (WASA) is of key importance in power system operators' decision-making. Lack of WASA can set in motion cascading failures, or contribute to the development of a blackout. Inadequate WASA was actually identified as one of the major causes of several blackouts in the last decade. A variety of factors in a power system control centre can affect the formation of WASA, especially during emergencies. This paper discusses the main sources of WASA errors and explores the effect of these errors on operators' response to an electrical disturbance. For this purpose, a multi-state model based on Markov modeling is developed to examine the impact of insufficient WASA on the probability of catastrophic blackouts. The proposed model is illustrated using the IEEE 24-bus Reliability Test System. View full abstract»

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  • Wide-Area Situational Awareness (WASA) system based upon international standards

    Publication Year: 2012 , Page(s): 1 - 6
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (292 KB)  

    Recently the importance of Wide-Area Situational Awareness (WASA) has increased as it can form the basis for power system stabilisation systems or be part of a smart grid. The standardisation of communication interfaces with the ability to integrate many kinds of sub systems becomes increasingly important in enabling the build of a standard WASA system. In Japan, Wide Area Monitoring, Protection and Control (WAMPAC) systems for power system stabilisation, which are a form of WASA system, have been applied for many years and significant experience has been gained in the application of this technology. We have conducted a review of our WAMPAC systems and international standards, and identified the standards that are important to WASA systems. Finally, we introduce a proposed system configuration for a WASA system based upon the international standards identified and a WASA evaluation system which we have developed. View full abstract»

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  • Wide-area measurements to improve system models and system operation

    Publication Year: 2012 , Page(s): 1 - 5
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (258 KB)  

    This paper presents collected events to demonstrate the use of synchrophasor data to update and improve system models and system operation. Examples are given of responses to events captured using wide-area synchrophasor measurements. Phase angle, frequency, and voltage responses are displayed with discussion of the events, synchrophasor data views, and insights to be gained from the different data types. This paper advances the understanding of wide-area measurement systems, which provide the newest development in system monitoring. View full abstract»

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  • Using a real time digital simulator with phasor measurement unit technology

    Publication Year: 2012 , Page(s): 1 - 6
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (317 KB)  

    Testing of Phasor Measurement Units (PMU devices) is necessary for any PMU application, be it a simple visualization and archiving system or a more complex set of real-time system operations tools. PMUs are available from virtually every manufacturer of protection and monitoring equipment. They are often implemented as embedded functions within relays or disturbance recorders. This paper describes the development of time synchronization hardware and a PMU software model for use on a Real Time Digital Simulator (RTDS®) View full abstract»

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  • Improvements to transformer differential protection — Design and test experience

    Publication Year: 2012 , Page(s): 1 - 6
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (713 KB)  

    Transformer differential protection schemes normally use multi slope characteristics to provide stability during CT saturation with 2nd harmonic restraint or blocking for inrush conditions. This paper presents new algorithms that have been developed to improve the performance of the differential protection. Extensive testing has been used to demonstrate that the transient bias algorithm can reduce the CT requirements for transformer differential protection. Testing has also shown that the new CT saturation and no gap detection algorithms improve the tripping time for internal faults with CT saturation. View full abstract»

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  • Enhancing differential protection stability during CT saturation with Transient Bias

    Publication Year: 2012 , Page(s): 1 - 4
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (153 KB)  

    The paper describes a Transient Bias technique designed to overcome the effects of Current Transformer (CT) saturation, which might severely affect the behaviour of a protection system. This Transient Biasing, as the name implies, is only active during transient conditions in the power system, and it decays quickly once the transients disappear. A complementary algorithm for fast detection of external faults is proposed, which prevents the Transient Bias feature from increasing the differential protection operating time in case of internal faults. The operation of current differential protection with Transient Bias is checked using Simulink® models of the relay and current transformer. In addition, the paper reviews the results of RTDS® tests carried out with actual current differential relays and provides detailed information on CT requirements testing method adopted by Alstom Grid. View full abstract»

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  • Experience with accumulated phase angle drift measurement for islanding detection

    Publication Year: 2012 , Page(s): 1 - 6
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (311 KB)  

    Distributed generation is increasingly likely to play a major role in electricity supply systems as recognition is made of its low carbon credentials. However, the integration of these units at distribution voltages is a major challenge for utilities. One particular issue is that generators may, unintentionally, continue to supply local demand when areas of the network are isolated from the main system. Reliably detecting this condition is regarded by many as an ongoing challenge as existing methods are not entirely satisfactory. This paper proposes a novel method based on accumulated phase angle drift that provides inherently enhanced stability without unduly sacrificing sensitivity. It is passive and thus requires no additional invasive hardware. Transient simulations have been used to demonstrate its performance [1]. The current paper presents further validation of the PAD method performance resulting from the field trial of a relay connected on the 38kV network at the interface to a 25MW windfarm in Ireland and also supplemented by the results of an on-going laboratory trial at the University of Strathclyde (UoS). View full abstract»

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  • Impact of IEC 61850 on the engineering of protection schemes

    Publication Year: 2012 , Page(s): 1 - 6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (218 KB)  

    The requirements for improvements in the efficiency and quality of protection schemes at the transmission and distribution level of the electric power systems highlights the need for development of new methods and tools that can help the industry achieve these goals. The paper describes an object-oriented engineering process for the development and implementation of protection schemes, the IEC 61850 Substation Configuration Language (SCL) and the different types of files that it defines and the engineering process based on this concept and the use of different standard files to achieve different engineering tasks. View full abstract»

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  • Currents sensors for advanced integration of protection, control, and metering functions

    Publication Year: 2012 , Page(s): 1 - 6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (739 KB)  

    The new generation of current sensors, such as Rogowski coils, have performance characteristics that can improve design and operation of modern power systems. This paper presents novel solutions that integrate protection, control, and metering functions for power transformers and cables by sharing signals from the same Rogowski coils. View full abstract»

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  • When existing recommendations for PST protection can let you down

    Publication Year: 2012 , Page(s): 1 - 6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (894 KB)  

    The paper will present implemented protection scheme on two, symmetrical, double core design Phase Shifting Transformers (PST) [6], each rated at 600MVA, 400kV, 866A, 50Hz, ±40° with in total 64 tap positions (32 advance and 32 retard). Thus, every individual tap introduce phase angle shift of 1,25°. The used PST protection scheme follows the protection recommendations published by IEEE [1]. It shall be noted that this IEEE recommendation is mainly based on information available in reference [2]. However during execution of this project new challenges were faced due to following reasons: • Slightly different construction of PST • Numerical differential relays are used instead of electro-mechanical ones originally suggested in [1,2] Due to these differences this paper will: • Indicate at which statements IEEE publication [1] is wrong due to slightly different PST design • Provide design and setting guidelines for 87P and 87S functions when modern numerical transformer differential protection is used View full abstract»

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  • High frequency fault location method for transmission lines based on artificial neural network and genetic algorithm using current signals only

    Publication Year: 2012 , Page(s): 1 - 6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (580 KB)  

    The present transmission systems are rapidly changing principally due to an increasing demand for better utilisation of existing lines resulting in lower transient stability limits, and also due to an increase in the complexity of the networks with small-scale distributed generation being connected into the existing networks. The current protection/fault location techniques are not conducive to such networks. This paper investigates a novel fault location method based on current signals only and utilising Artificial Intelligence technology. Importantly, the robustness and sensitivity of the technique developed is presented through an extensive series of studies and results when applied to complex power networks. View full abstract»

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  • Supervised shutdown algorithm for an offshore wind power plant to meet the required ramp rate of a grid code in a storm-driven situation

    Publication Year: 2012 , Page(s): 1 - 5
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (196 KB)  

    This paper proposes a supervised shutdown algorithm for an off-shore wind power plant (WPP) to meet a required rampdown rate of a grid code in a storm-driven situation. The algorithm determines the number of wind generators (WGs) to shutdown simultaneously by considering the required ramp-down rate of a WG without using a brake. Based on the wind direction and speed measured at a wind mast (WM), wind arrival times from a WM to each WG are calculated. Then, a sequence of WGs is generated in the order of wind arrival time and subsequently a group sequence is generated. The shutdown end time of each group is determined as the minimum wind arrival time in the group whilst the shutdown start time is determined by subtracting the duration of the shutdown from the end time. If the shutdown start/end times of adjacent groups are overlapped, the start/end times of the preceding group are re-scheduled by considering the overlapped time. The performance of the algorithm is verified under various storm conditions. The results indicate that the algorithm can shut down the WPP without exceeding the required ramp rate in a grid code. View full abstract»

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  • New concept of power based pole slip protection for dispersed generators in Smart Grid environment

    Publication Year: 2012 , Page(s): 1 - 6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (379 KB)  

    The paper presents a new pole slipping protection method that combines high efficiency of pole slip detection and sensitivity to many sources of potential pole slipping. To simplify the setup process the adaptive settings are calculated continuously. The new adaptive method utilizes active and reactive power measurements on machine terminals to ascertain that the synchronous machine is committed to pole slips. In doing so, it offers the capability of detecting pole slips even before it occurs (predictive features). During the method investigation the main efforts have been focused on the development of new protection techniques, which should ensure better (faster and more selective than currently known) detection of loss of synchronism in a synchronous machine. In the article a new approach to pole slipping protection and exemplary results are presented. The method has been successfully tested with utilization of data from simulation as well as signals from the laboratory of real synchronous machines. View full abstract»

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  • A new multi-criteria fuzzy logic transformer inrush restraint algorithm

    Publication Year: 2012 , Page(s): 1 - 6
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (306 KB)  

    This paper presents a new multi-criteria stabilization algorithm of transformer differential protection. Proposed scheme bases on new criteria signals and appropriate operation thresholds. New algorithm employs fuzzy reasoning technique for better discrimination of inrush conditions. The developed stabilization algorithm has been tested with ATP-EMTP generated signals, proving to be reliable and much more sensitive than standard stabilization algorithms with crisp settings. View full abstract»

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  • A new method to identify inrush current by composite calculation

    Publication Year: 2012 , Page(s): 1 - 5
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (275 KB)  

    This paper reviews the characteristics of inrush current and analyses its causes. The development of digital substation and the concept of integrated protection are also outlined. The paper studies different models to simulate several kinds of inrush and internal short-circuit fault. Through these models, the new composite algorithm is analysed in order to verify the reliability and sensitivity of the new method. By comparing the action situation of traditional inrush restrain principle and the new composite method, the new method owns better identification reliability. View full abstract»

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  • IEC 61850 communications based transmission line protection

    Publication Year: 2012 , Page(s): 1 - 6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (362 KB)  

    IEC 61850 is the new standard for communications in substations that defines a new generation of protection applications based on high speed peer-to-peer communications between different substation devices. Accelerated protection schemes use permissive or blocking signals exchanged between relays at the two or more ends of the protected transmission line in order to provide fast fault clearing for any fault type or location. The paper discusses the different possible implementations of such schemes in substations with IEC 61850 and compares the expected performance of IEC GOOSE based solutions with the conventional hard wired schemes. A directional comparison protection scheme is used as an example. The requirements and methods for testing of such schemes are described at the end of the paper. View full abstract»

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  • Use of IEC61850 in a 400kV cable monitoring system

    Publication Year: 2012 , Page(s): 1 - 5
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (404 KB)  

    The project to install new cables in the Woodhead Tunnel forming part of National Grid's (NGET) 400kV transmission system running across the Pennines, requires a state of the art cable monitoring and protection system. The availability of IEC61850 offers the opportunity to provide a simple but effective system in an early long haul application. View full abstract»

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  • Electric traction system rationalisation via Integrated Protection and Control IEC 61850 extended station bus solution

    Publication Year: 2012 , Page(s): 1 - 6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (283 KB)  

    This paper describes how increased functionality of the Network Rail Integrated Protection and Control (IPC) extended IEC 61850 station bus solution unlocks the ability to rationalise the electrification system design, and hence achieve a substantial reduction in primary plant requirements when delivering the new railway electrification schemes committed by the Government. View full abstract»

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  • Development of process bus for busbar protection and voltage selection scheme

    Publication Year: 2012 , Page(s): 1 - 5
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (836 KB)  

    Busbar protection is described for a bus with current inputs for up to 32 bays. For busbar protection with IEDs and MUs using IEC61850–9–2 process bus, communication traffic jams are the main concern, due to transferring 80 samples/cycle data from all bay MUs to IED via 100BASE-FX. This paper describes peer-to-peer connection between MUs and IED in order to segrigate the SV messages of 32 bays on the process bus. As a LAN switch is not necessarily required in the process bus, higher reliability, long lifetime, interoperability and easy-maintenance can be achieved. The sampling timing of each MU is controlled from IED by 1PPS signal which is independent from the time stamp signal made by GPS so that lock out of busbar protection is prevented even at the case of GPS clock loss. This technique can be applied not only to busbar protection but also to VSS (voltage selection scheme). View full abstract»

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  • Modification of in-service substation based on IEC 61850

    Publication Year: 2012 , Page(s): 1 - 5
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (106 KB)  

    The standard IEC 61850 contributes the manufacturers and the end users. But it also makes many obstacles to the modification of the conventional substation. This paper presents a scheme which modifies an in-service conventional substation gradually to a modern substation which conforms to IEC 61850 standards. The procedure of the modification is divided into three stages. During the first stage, all the preparations have been finished. All the configurations and joint tests have been done before shipment. The secondary stage is to construct the substation network. New Human Machine Interface (HMI) and communication gateway will replace the old ones. They simultaneously support protocol of the existing system and IEC 61850 standards. The third stage is the modification of the bay level devices. The old cabinets and the cables out of the cabinets are kept. The inner IEDs are replaced. The connections between the IEDs and the cabinets also need to be re-arranged. The modification of bay can be done one by one according to the overhaul plan. The process is stable and secure, and it won't affect the normal operation of the substation. View full abstract»

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  • A Multi-Agent System for protection coordination of radial systems in the presence of distributed generation

    Publication Year: 2012 , Page(s): 1 - 6
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (341 KB)  

    This paper proposes a Multi-agent System (MAS) approach to coordinate overcurrent relays, aiming to protect distribution systems with distributed generators. The connection of distributed generation (DG) units causes a reduction in the efficacy of protection systems coordination and, in some cases, an increase of operating times. Coordination studies aim to guarantee the protection selectivity in a diversity of fault situations, also considering topological changes. Consequently, sometimes a correct protection operation at every point of the system in every possible situation cannot be guaranteed. The proposed MAS uses communication between agents to achieve on-line coordination. In order to evaluate the approach, simulation tests of a real system were executed and the protection operating times using the proposed methodology are compared with the operating time of existing relays. Results show that this approach provides a noticeable reduction of protection operating time and there is also an improvement of selectivity. View full abstract»

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  • Measured impedance by distance relay for inter phase faults in the presence of SVC on double-circuit lines

    Publication Year: 2012 , Page(s): 1 - 6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (227 KB)  

    This paper presents the measured impedance at the relaying point in the presence of Static Var Compensator (SVC), one of the shunt connected Flexible Alternating Current Transmission System (FACTS) devices; in the case of inter phase, phase to phase and three phase, faults. The presence of SVC on a transmission line has a great influence on the measured impedance at the relaying point. In the presence of SVC, its compensation current as well as its installation location affects the measured impedance and consequently the distance relay ideal tripping characteristic. View full abstract»

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  • Time-varying waveform analysis for power transformer protection using frequency shift Empirical mode decomposition

    Publication Year: 2012 , Page(s): 1 - 6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (70 KB)  

    Empirical mode decomposition (EMD) method is a novel time-frequency analysis tool to analyse non-stationary signals, which decomposes the signal concerned into intrinsic mode functions (IMFs) modulated in terms of both amplitude and frequency. The original version of EMD, however, suffers from an algorithm difficulty to separate two individual components, frequencies of which are within an octave. To improve the frequency resolution, a signal pre-processing method is used to shift the frequencies apart based on signal communication theory. This proposed frequency shift EMD has been successfully applied to extract modal parameters of low frequency oscillations for power systems. In this paper, this method is used to analyse the transient signals (inrush current) in the field of power transformer protection. Comparing with low frequency oscillation signals, these signals include more frequency components with faster dynamics. Numerical simulations are conducted to verify the frequency shift EMD. The results show that this method is adequate for time-varying waveform analysis for power transformer protection, and with the information provided by this frequency shift EMD, more robust protection schemes for power transformer could be proposed. View full abstract»

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  • Superiority of decision tree classifier on complicated cases for power system protection

    Publication Year: 2012 , Page(s): 1 - 6
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1132 KB)  

    Diagnosis of power system faults requires identification and classification of voltage disturbances in power systems and smart grids. The objective of this approach is to develop state of art signal classification algorithms for classifying different types of power quality disturbances (faults) based on latest improvements in signal processing and pattern recognition techniques. This paper proposes a new solution for power system monitoring against all possible power quality issues. S-transform is used for analyzing distorted power signal. As a classifier, decision tree algorithm is used and its performance is compared to other classifiers. The proposed hybrid power system monitoring system is able to detect common power system disturbances such as voltage sag/swell/, flicker, DC component, electro-magnetic interference, harmonics, transients and blackouts. View full abstract»

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  • Migration paths for IEC 61850 substation communication networks towards superb redundancy based on hybrid PRP and HSR topologies

    Publication Year: 2012 , Page(s): 1 - 6
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (490 KB)  

    This paper provides an overview of recent developments in high availability networks and new redundancy protocols designed to guarantee seamless failover and proper functioning of the most critical substation automation applications such as tripping via GOOSE (Generic Object Oriented Substation Event) messages and IEC 61850 Process Bus based on switched Ethernet. The authors describe most common redundancy methods such as Rapid Spanning Tree Protocol and the latest redundancy protocols such as PRP (Parallel Redundancy Protocol) and HSR (High Availability Seamless Redundancy). In addition the authors elaborate on possible migration strategies of existing networks, provide a vision of hybrid PRP-HSR networks for HV (High Voltage) and EHV (Extra High Voltage) installations and propose HSR as a switch redundancy solution for future replacement of RSTP. View full abstract»

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  • IEC61850 substation experiences DPSP 2012

    Publication Year: 2012 , Page(s): 1 - 5
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (122 KB)  

    The advent of IEC61850 Standard has ushered a new age for substation automation. This standard has gained a very strong footing in Europe and its application is spreading across the world. In USA the progress towards IEC61850 implementation is relatively slower. IEC61850 holds great promises for substation automation and protection. There are many advantages that this standard brings to the area of protection and automation in the form of reduced substation cost, ease of communication, reduced wiring cost, and interoperability between various multi-vendor IEDs. Although this standard is viewed as being very useful and cost-effective, there are several new challenges posed by the implementation of this standard in the US. Some of these are the level of understanding of this standard in the US is spotty which will improve over time. Another issue that concerns utilities in the US is the level of cyber security that this standard provides. At this point the IEC61850 in the US is limited to the walls of the substation. Hence, for the present time, the cyber security issues are within the regulation imposed by the various regulating agencies in the US. One other issue that is very critical is the new techniques and tools required for commissioning a substation that has multi-vendor IEDs. This main thrust of this paper is to highlight some of the installation and commissioning issues that were encountered during one of the pilot projects at a utility in the US. This pilot project involved the first IEC61850 substation built in the US with multi vendor IEDs. There were several challenges that the commissioning team had to face and it was a great learning experience for everybody involved. This paper will highlight all the experiences associated with making this first IEC61850 substation a great success in the US. This paper will consist of four sections. The first section will cover the hardware needed to support the IEC61850 communication over a TCP/IP network. The secon- section will explain what and how IEC61850 GOOSE works. This section will include an example of a line relay application. The second section will also cover the security aspects of using IEC61850 for substation control and protective relay applications. The third section will cover testing the individual measuring units in the relays and the overall protection scheme tests. The fourth section is about lessons learned during the initial design and substation commissioning. View full abstract»

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  • IEC 61850 experience in the Portuguese transmission system to date and foreseeable applications in the future — A case study and future outlook

    Publication Year: 2012 , Page(s): 1 - 6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (260 KB)  

    In this paper the authors report current experience of IEC 61850 application in the Portuguese transmission system through the presentation of the Ermesinde case study. Adopted physical and logical architectures, function allocation, as well as engineering tools and processes are described and discussed. In the second part of the paper a future outlook for advanced transmission system automation is presented in terms of opportunities and challenges in the light of current praxis, edition 2 and future developments of IEC 61850. View full abstract»

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  • Design and operation of the IEC61850 9–2 process bus used for the protection system

    Publication Year: 2012 , Page(s): 1 - 6
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (195 KB)  

    The digital substation and the implementation of IEC61850 are fundamental to the future of protection relays. The IEC61850 standard, "Communication Networks and Systems in Substation", provides the basis for the communication system for the digital sub-station's protection and control schemes. Section 9–2 defines the Ethernet based communication network providing data transfer between primary equipment and bay level IEDs, the process bus. This paper describes the background for the choice of bus architecture for the process bus for use in an EHV transmission sub-station. It reports on the results of performance tests on a feeder protection scheme using both an IEC 61850 and a conventional relay. Further tests have examined the performance of the IEC61850 relay when the data transfer traffic on the process bus exceeds its capability and data packets are therefore lost. View full abstract»

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  • Use of transmission protection technology in distribution relays

    Publication Year: 2012 , Page(s): 1 - 5
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (195 KB)  

    Transmission level protection functions are increasingly being looked at for Distribution systems. This can be attributed mainly to the enhancements being planned for by the Operating Companies, to increase the system efficiency, and also to ensure reliable power supply to the end Consumers. Slowly, the catch word "Smart Grid" is being consciously and progressively transformed to practical implementations to reap operational benefits, and to increase the system reliability. There is also increased regulatory pressure on the Operating Companies to revamp the Distribution systems to prevent major catastrophes, given that the nature of these Distribution systems is also changing. One such change could be the birth of "micro-grids", where the lower fault levels could necessitate application of differential or distance protection. Given all these demands, though it seems straightforward to use the existing Transmission protection relays in Distribution as well, practical benefits need to be weighed. Also, considerations need to be given to the physical limitations and the operational demands. This paper will attempt to capture the emerging trend of the use of Transmission Protection Technology in Distribution systems, by elucidating the needed balance between the practical benefits that could be enjoyed, and the constraints that could be posed. View full abstract»

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  • Performance evaluation of current differential relays over a wide area network

    Publication Year: 2012 , Page(s): 1 - 6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (274 KB)  

    Progress in the development of communication network technology continues apace and Ethernet technology, once limited to local area network applications, is increasingly being considered for use as the backbone technology for wide area communication networks. The technology, most commonly referred to as “Carrier Ethernet”, seems likely to become the dominant technology within wide area networks ultimately replacing earlier generation networks based upon PDH and SDH / SONET platforms. The availability of Carrier Ethernet and in particular, in terms of the testing described here, IP/MPLS-based Carrier Ethernet now enables us to consider the application of Ethernet technology to teleprotection. View full abstract»

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  • Current sensors for improved capacitor bank protection

    Publication Year: 2012 , Page(s): 1 - 6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (575 KB)  

    The new generation of current sensors has performance characteristics that can improve design and operation of modern power systems. This paper presents novel solutions for protection of capacitor banks using Rogowski coils as currents sensors. View full abstract»

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  • Improving open-loop medium-voltage feeder self-healing

    Publication Year: 2012 , Page(s): 1 - 6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (215 KB)  

    A common practice for improving electric service reliability is to provide an alternate source of supply. On the distribution system, two feeders — each with one or more mid-line overcurrent protective devices — can be tied together through a normally-open tie point to restore service to unfaulted sections of line. Conventional looped distribution systems rely on overcurrent coordination to ensure that the correct device in the loop clears a given fault. But existing technologies have limited abilities to properly coordinate a large number of devices in series. This paper outlines the application of new technologies that enhance the loop system concept by testing the line for faults without using conventional reclosing. Pulseclosing technology, unlike conventional reclosing, reduces thermal and mechanical stress on substation transformers and other equipment by eliminating the repeated occurrence of high fault currents. It overcomes coordination constraints, allowing the expansion of a distribution loop to an unlimited number of series overcurrent protection devices. Pulseclosing effectively hunts for faults without affecting upstream customers and it reduces the opportunity for sympathetic tripping of nearby devices. Maximum system restoration can be achieved within a few seconds after initial fault detection. These advancements are all achieved without the need for communication between devices. View full abstract»

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  • Flexible protection architectures using distributed optical sensors

    Publication Year: 2012 , Page(s): 1 - 6
    Cited by:  Papers (5)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (413 KB)  

    In this paper we describe recent developments in flexible protection schemes that make use of passive fibre Bragg grating (FBG) based transducers for the distributed measurement of voltage and current. The technology underpinning the passive optical approach is described in detail, and both the present development and the future potential of the approach are discussed. In co-operation with Toshiba, the integration of the technique with an existing busbar protection relay is demonstrated, illustrating the flexibility offered by protection schemes that are based on the use of small, passive, multiplexable, dielectric transducers. View full abstract»

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  • Recent developments in standards and industry solutions for cyber security and secure remote access to electrical substations

    Publication Year: 2012 , Page(s): 1 - 8
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (241 KB)  

    This paper discusses real world examples of utility initiatives to address the issue of substation cyber security in the context of both industry best practices and the global standards organizations seeking to provide a blueprint for security implantation. The authors provide an overview of existing technologies for securing IP and Ethernet communications networks and end devices. One of the aspects helping secure access to utility networks are centralized secure access management systems that facilitate authentication and authorization of users and devices while increasing productivity by reducing manually repetitive tasks. A commercial implementation of such a system is described. The authors also provide a brief overview of the latest industry efforts in standardization and describe selected focus groups, initiatives and institutions that are developing cyber security guidance for the electric power industry. Finally the authors describe practical experience from deploying a secure remote access management system at a large transmission utility in the United Kingdom. Key challenges, issues and experience from system design and implementation are presented. View full abstract»

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  • Assessing the reliability of adaptive power system protection schemes

    Publication Year: 2012 , Page(s): 1 - 6
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (192 KB)  

    Adaptive power system protection can be used to improve the performance of existing protection schemes under certain network conditions. However, their deployment in the field is impeded by their perceived inferior reliability compared to existing protection arrangements. Moreover, their validation can be problematic due to the perceived high likelihood of the occurrence of failure modes or incorrect setting selection with variable network conditions. Reliability (including risk assessment) is one of the decisive measures that can be used in the process of verifying adaptive protection scheme performance. This paper proposes a generic methodology for assessing the reliability of adaptive protection. The method involves the identification of initiating events and scenarios that lead to protection failures and quantification of the probability of the occurrence of each failure. A numerical example of the methodology for an adaptive distance protection scheme is provided. View full abstract»

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  • Smart power grids — A perfect solution, or just a fashion

    Publication Year: 2012 , Page(s): 1 - 4
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (107 KB)  

    The increase of the electric power demand is at the level 2–3% per year, and in some regions of the world may become much higher. In the same time the infrastructure of power systems develop much slower. The smart grid technology is to use modern telecommunication and informatics to bridge the gap. The aim is to integrate generation, transmission, distribution and consumption of the electrical energy to supply the power in reliable, safe, economic way with consideration of the environmental requirements. The technology consists of four main parts: • Management of demand. • Operational control of generation, transmission and distribution. • Protective devices of the new generation (adaptive and wide area). • Self healing and fast restitutions after system breakdowns. View full abstract»

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  • The performance triangle in digital substation architectures

    Publication Year: 2012 , Page(s): 1 - 6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (70 KB)  

    In the traditional domain of teleprotection signalling, there is a recognised triangle of performance. This triangle depends upon the required speed of communication, the expected dependability of the command, and the security of receipt. These three aspects are interlinked, and the correct balance of each is required in order to offer the traditional functionality such as permissive signalling, blocking and intertripping schemes. This paper relates the traditional concepts to the application of automation schemes within digital substations. In this manner, it is anticipated that protection engineers can relate today's Ethernet technology by analogy with equivalent trusted practices. Firstly, the paper discusses aspects of speed, particularly in terms of the response required in message-based schemes, and the methods by which integrators can achieve accurate time-synchronising. Secondly, achieving adequate dependability by means of redundancy, and appropriate architectures is treated. Thirdly, security is covered, including aspects of cybersecurity and settings/configuration management. View full abstract»

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  • A network sever-based simulator for protective relays

    Publication Year: 2012 , Page(s): 1 - 4
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (424 KB)  

    This paper presents a network-based simulator for protective relaying algorithms. The simulator is based on the client-server paradigm. The simulator which consists of server-side relaying algorithm modules and the user interface provides the network-based environment to simulate a variety of protective relaying algorithms. It is developed by using open-source development tools and model-based design methods. The relay models implemented have many functional blocks for flexibility. Clients are able to access the simulator through a generic web browser. The simulator makes it possible for protection engineers, relay developers and students to concentrate on the development and analysis of a protective relaying algorithm in which users are interested. View full abstract»

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  • Voltage unbalance protection VT and relay errors effect on unbalanced voltage detection; Considerations for system relaying, stability and developments

    Publication Year: 2012 , Page(s): 1 - 7
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (70 KB)  

    In a power system network, an unbalanced voltage condition can occur due to various reasons. Excessive voltage unbalance has become an issue of concern in power quality at network level, leading to numerous problems. This calls for a stringent management of unbalanced. There are several codes of practice to advise and to enforce network operating conditions to keep system unbalance within specific limits. Analysis of system unbalance voltage and power system control is carried out through Voltage Transformers and protective relays. The accuracy of Voltage Transformers from primary to secondary varies according to the type (Class of VT). Also, the accuracy of Relays is of the concern to the same extent. This poses a limitation on detection of actual system unbalance. This study gives an overview of fundamentals of sequence components, unbalanced voltage definitions and use of different types of VTs and relays to analyse unbalanced voltage. This paper considers detection of low level voltage unbalance equivalent to maximum limits allowed in national grid codes in order to initiate system to generate tripping/alarm. This article endeavours to summarise deviational effect of accuracy levels of VT and relays. The study provides a reference of selection of VTs and Relays to detect known % unbalance in the system. Coverage has been extended to discuss mitigation techniques of voltage unbalance and deviational error minimisation. The emphasis is to initiate a thought process for requirement of improved methodologies to eliminate errors in analysing. Therefore this study aims in building a better power system. View full abstract»

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  • Full H7 compliant trip circuit supervision using numerical relays

    Publication Year: 2012 , Page(s): 1 - 4
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (385 KB)  

    Protection of power systems requires a high degree of reliability. Whenever a protection is called upon to operate, it must do so. Failure to do so may result in costly damage to plant, loss of supply to many consumers, and potentially, danger to life. Protection relays are designed in such a way as to ensure reliability of operation. Very often, the main threat to reliable operation is the circuit connecting the operating contact and the circuit breaker trip coil itself. Thus, it is usual to monitor these elements using trip circuit supervision (TCS). The aim of our work in this area was by investigation, discussion, reasoning, calculation and testing, to devise a straightforward solution to strictly meet the ENA “H7” specification by utilisation of opto-isolator inputs in numerical relays. This paper details the success achieved with this. View full abstract»

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  • The comparison and analysis for loss of excitation protection schemes in generator protection

    Publication Year: 2012 , Page(s): 1 - 6
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (346 KB)  

    Loss-Of-Excitation (LOE) condition of a generator may cause severe damages on both generator and the interconnected systems. This paper analyses the behaviours of different LOE protection schemes, such as R-X, G-B, P-Q and U-I schemes, for a hydro generator, which is connected to an infinite bus. Based on the simulation results, the reliability and stability of existing LOE protection schemes are compared and a preferred scheme is selected. An improvement to the scheme is also proposed to prevent the LOE relay incorrect operation during external faults, such as short-circuit faults on busbar or transmission lines. View full abstract»

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  • Impact of low burden on measurement transformer accuracy under steady state conditions

    Publication Year: 2012 , Page(s): 1 - 4
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (70 KB)  

    This paper discusses the behaviour of both current- and voltage transformers under low-burden conditions. It is shown that this behaviour is basically linear under steady-state conditions. Moreover, there is a duality between the equations for VT and CT. Recommendations and possible mitigation strategies in case of low burden on the secondary side of measurement transformers are discussed. View full abstract»

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  • Fault location method using measurements of differential relays for parallel transmission lines with series capacitor compensation at both ends

    Publication Year: 2012 , Page(s): 1 - 6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (322 KB)  

    This paper presents an accurate fault location algorithm for double-circuit transmission lines with series capacitor compensation at both ends. It has been considered that a fault locator utilizes a communication channel of differential protective relays through it phasors of currents at both line ends are exchanged. Besides the phasors of two-end currents, three-phase voltage measured at a local end and a zero-sequence current from a parallel healthy line circuit have been additionally included into the fault locator input signals. The developed fault location algorithm has been formulated for fault loops composed accordingly to the fault type. The algorithm has been tested and evaluated using signals taken from ATP-EMTP versatile simulations of faults on the test series compensated transmission line. The presented sample results of the evaluation show the validity of the presented fault location algorithm and its high accuracy. View full abstract»

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