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Universities Power Engineering Conference, 2006. UPEC '06. Proceedings of the 41st International

Date 6-8 Sept. 2006

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  • [Front cover]

    Page(s): C1
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    Freely Available from IEEE
  • An Integrated Protection Scheme Based on a Distance Approach

    Page(s): 800 - 803
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (5010 KB) |  | HTML iconHTML  

    This paper presents a new integrated protection scheme based on distance protection technique. An integrated protection relay is installed at a substation and interfaced to every line through the CTs and busbar VT. The relay is also interfaced to the substation communication network which is communicated with all neighboring substations. The directional detection, phase selection and adaptive distance algorithms are implemented into the relay with multiple distance settings for the protection of every line sections connected to the substation busbar. When a fault occurs on any of the line associated with the substation, the relay will firstly determine the faulted direction, then the faulted phase. The distance algorithm together with the relevant setting will then apply to the faulted line/phase to determine the fault location. The relay will trip instantly when a zone 1 fault is detected. The relay will communicate with relevant relay at remote ends to determine whether to trip or restrain when a zone 2 fault is detected. The paper includes studies of a typical multi section system, which shows that the new scheme not only offer the new protection features for individual power line, but also provide the characteristics of integrated protection View full abstract»

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  • An Application of Electrical Interaction Paths in Equivalence Networks to Identify Cut Edges and Vertices

    Page(s): 804 - 808
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (3089 KB) |  | HTML iconHTML  

    The removal of cut edges and cut vertices will lead to disconnected sub-graphs in a connected power network. These edges and vertices may stand for the weak places or some optimization partitioning and dimensionality reduction strategy, which have significance for such network analysis as power flow, voltage stability and relay coordination. The identification of cut edges and cut vertices can be expressed into observing the change of topology connectivity while removing some vertices or edges, which can be implemented by the geometrical topology analysis methods. Based on the analysis of equivalent networks and electrical interaction paths, this paper presents a novel physical topology analysis arithmetic to identify cut edges and vertices, which introduces two simple equality criterions derived from the reduced Z-matrix elements. The improvement over existing graph-theoretical approaches is in that this new arithmetic has specific physical significance, which can borrow ideas to insight and research the relationship between geometrical topology and physical topology in power network View full abstract»

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  • Voltage Inversion Due to Presence of TCSC on Adjacent Lines and Distance Relay Mal-Operation

    Page(s): 809 - 813
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (455 KB) |  | HTML iconHTML  

    This paper discusses the distance relay over-reaching in the presence of thyristor controlled series compensator (TCSC) which is categorized as a series connected flexible alternating current transmission system (FACTS) device. This is done by presenting the measured impedance at the relaying point in the case of TCSC presence at the near end of the line behind. Distance relay tripping characteristic is greatly influenced in the presence of TCSC on the transmission line or even in the case of installation of TCSC on the adjacent lines, near end of the line behind. Distance relay tripping characteristic depends on many factors including the power system structural conditions and the pre-fault loading, the earth fault resistance, and TCSC compensation degree View full abstract»

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  • The Development of Non-Intrusive Techniques for Partial Discharge Detection on MV and EHV Switchgear

    Page(s): 814 - 818
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (3907 KB) |  | HTML iconHTML  

    There is a large population of ageing distribution plant and equipment installed on electricity companies' networks and in many industrial and commercial locations. In order to achieve effective utilisation of these assets and make sound decisions on maintenance strategies, asset refurbishment or replacement, it is necessary to have reliable information on the condition of existing plant. The trend to extend maintenance periods and optimising the availability of switchgear brings with it a need for interim non-intrusive diagnostic techniques to give confidence in the continuing safety and reliability of the equipment. This paper will look at developments in equipment available for partial discharge testing of switchgear operating in the 3.3 kV-400 kV range View full abstract»

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  • A Microprocessor and Wavelets Based Relaying Approach for on Line Six-Phase Transmission Lines Protection

    Page(s): 819 - 823
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (442 KB) |  | HTML iconHTML  

    This paper introduces a microprocessor and wavelets based non communication relaying approach dedicated for on line six-phase power transmission lines fault detection, classification and faulted phase(s) selection. The approach uses wavelets for capturing the fault induced high frequency signals of currents and/or voltages. The captured high frequency signals are then used in conjunction with their energies to determine the faulted line and consequently for making a trip decision. For this purpose, a suitable wavelet for on line protection is chosen and tuned at a suitable band of frequencies. In order to investigate a real time performance of the introduced approach a microprocessor based laboratory prototype has been implemented and tested. The obtained results show that the approach is high speed in faulted phase(s) detection and insensitive for the fault inception angle, fault resistance, and line terminals View full abstract»

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  • Optimal Coordination of Directional Over Current Relays in Power System Using Genetic Algorithm

    Page(s): 824 - 827
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (3064 KB) |  | HTML iconHTML  

    In this paper a new approach will be used for optimal coordination of directional over current (DOC) relays based on genetic algorithm. In this approach, optimal operation characteristics and also optimal current setting and time setting of each OC relays will be determined simultaneously. Also, a new objective function will be used which is different from ordinary methods such as simplex, two phase simplex, dual simplex. Improvement of selectivity and speed of the protection system, obtaining the absolute optimal point of the optimization problem are the specifications of the proposed approach. Numerical results obtained with the proposed method for a real power system are presented View full abstract»

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  • Transient Directional Protection Based on the Transformation of Positive Sequence Component

    Page(s): 828 - 831
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (2040 KB) |  | HTML iconHTML  

    This paper proposes a new current mode derived by a new modal transformation technique, the alpha mode. The mode is used to detect and distinguish between internal and external faults for power line protection, based on a new transient directional comparison technique using current alone. The technique uses the symmetrical component to replace Clark or Karrenbauer transformation to decouple the three phase transient current signals. Wavelet transform is then applied to the positive sequence component to produce the modular maximum, which are subsequently used to distinguish between internal and external faults. The modular maximum of the wavelet transform for the new alpha mode have the same polarity at both ends of the line for internal faults and opposite polarity for external faults. Theoretical analysis and extensive simulation studies show that the technique is able to give correct responses for all fault types View full abstract»

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  • An Advanced Substation Communication System for Integrated Protection

    Page(s): 832 - 835
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1523 KB) |  | HTML iconHTML  

    This paper proposes an advanced substation communication system for supporting the latest development in power system protection - integrated protection. Recent developments in power system protection are firstly outlined, and then a description of a substation integrated protection system supported by an advanced communication network is given. Based on the proposal, there are 3 major components within the network: the CVD communication unit; the optical network; and the central integrated protection unit. The research will focus on the concept, evaluation and design of the optical network communication system. View full abstract»

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  • A Novel Optical Current Transformer Based on Comparative Measurement

    Page(s): 837 - 840
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    A comparative method, which can compensate the material's Verdet constant and linear birefringence variations of Optical Current Transformer (OCT) due to environmental factors, is proposed. The strategy is based on a novel OCT where a permanent magnet is used as reference source. Theoretic analysis is carried out employing matrix optics theory, and the experiment results are presented to show the validity. The point type sensing head is adopted in designed sensing element. So the OCT is simple in structure and is suitable for applications in the high voltage environment. View full abstract»

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  • Investigation into Protection of Active Distribution Network with High Penetration of Embedded Generation Using Radial and Ring Operation Mode

    Page(s): 841 - 845
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (3805 KB) |  | HTML iconHTML  

    Existing distribution networks are mostly designed to operate in radial mode without having generation units accommodated on them. The increase in penetration of embedded generations (EGs) into existing distribution network in recent years has resulted in bi-directional power flow and changes in network voltage profile. These in turn caused important impact on system protection of existing distribution network. The protection issues that have been identified include (i) increase of network fault level that requires costly upgrading of switchgears, (ii) disruption of feeder protection operation which could lead to unnecessary tripping of healthy feeders and reduction of the fault detection sensitivity of protection devices, (iii) the necessity of introducing new protection requirements particularly with regard to loss of mains (LOM) protection to avoid islanding condition (iv) the necessity of introducing the concept of intentional islanding under certain circumstances. Future distribution networks are likely to be operated in ring mode rather than radial in order to optimise the integrated capacity of embedded generations as reported in literature. The advantage of adopting ring mode operation includes, (i) increase of the reliability of electric power supplies and (ii) in the context of EGs, it eases the issues of voltage regulation. However, ring operation mode in addition to the presence of embedded generation could complicate the protection system, particularly, that related to feeder protection. Therefore special considerations are required for ring feeder protection compared to radial operation mode. This paper concerns with investigating the protection requirements of ring and radial distribution networks in the presence of embedded generations (EGs). View full abstract»

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  • Protection Issues Associated with the Proliferation of Static Synchronous Compensator (STATCOM) Type Facts Devices in Power Systems

    Page(s): 846 - 850
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (2186 KB) |  | HTML iconHTML  

    With the increase in the number of static synchronous compensator (STATCOM) type FACTS devices in transmission lines, operation of distance relays in transmission lines are affected. It is very important that the distance relays do not mal- operate under system fault conditions, as this will result in the loss of stability or the security of the system, which defeats the main objective of installing a STATCOM. As STATCOM type FACTS devices have fast response and their functional characteristics and control system introduce dynamic changes during fault conditions in a transmission line it is important that distance relays perform correctly irrespective of such dynamic changes introduced during fault. In this paper, a general survey of the FACTS devices employed in the power systems is presented. This is followed by a review of the effects of a STATCOM connected at the midpoint of a transmission line on the performance of distance protection relays. View full abstract»

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  • An Advanced Real Time Digital Simulator Based Test System for Protection Relays

    Page(s): 851 - 855
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (2602 KB) |  | HTML iconHTML  

    This paper reports on the developments of the real time digital simulator (RTDS) based test systems for protection relays. The background of the developments in protection relays and their associated technologies, such as optical transducers and IEC 61850, are introduced. New developments in RTDS systems are described. It is shown that the current development in transducers and communication technology will have great impact on the developments of protection relays and their associated RTDS based relay test systems. The paper further describes the current, new developments and the future trend in the development of protection relays and their associated RTDS systems View full abstract»

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  • Load Flow Method for Distribution Network Design by Considering Committed Loads

    Page(s): 856 - 860
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (456 KB) |  | HTML iconHTML  

    The conventional load flow methods for transmission systems could not be utilized for distribution systems, due to their especial characteristics. If methods like Newton-Raphson and fast-decoupled are used for distribution systems, the probability of the convergence would be low. Therefore, due to inherent characteristics of distribution systems, it is essential to develop the distribution version of the load flow methods. One of the applications of distribution load flow methods is in the design process, at either MV or LV level. There are two types of loads in the design process, current committed and demand committed loads that both must be considered by load flow for design purpose. This paper presents a load flow method for distribution network design, which can handle both current and demand committed loads View full abstract»

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  • Condition Monitoring System for Circuit Breaker Based on Substation Automation System

    Page(s): 861 - 865
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (2138 KB) |  | HTML iconHTML  

    Condition monitoring of circuit breaker is preference for cost saving in power utilities. However, extensive condition monitoring of circuit breaker is a hard task considering its tremendous number. Circuit breaker time, which is composed of opening time and arcing time, as well as its variation trends, can be used as an index to represent condition of mechanical and dielectric component of circuit breaker. Since the digital relay and digital fault recorder that can record dynamic process of circuit breaker operation, it is especially attractive to extract this data for circuit breaker information without hardware investment. In order to deduce circuit breaker time with transient data logged in substation automation system, a substation automation information management system is developed in this paper. The transient data follows transient data transformation standard (COMTRADE) is concentrated in controlling center. The information management system parses the composition and format of the logged data according COMTRADE, hence calculate and visualize the circuit breaker time and its variation trends View full abstract»

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  • Thermal Overload Protection of Induction Motors Under Waveform Distortion

    Page(s): 866 - 870
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (434 KB) |  | HTML iconHTML  

    Induction motors require thermal protection to prevent overheating due to cyclic as well as steady state overloads. A protective relay uses the thermal model to continuously calculate the temperature in real time. The virtual temperature is monitored and trips to prevent overheating. Although the thermal models are relatively suitable for protecting the motors in the overload condition but they are not quite effective under distorted waveforms. Due to the harmonics in the system, the total losses in the motor will be more resulting in higher temperature rise of the motor. Under distorted supply system the motors cannot be operated at full load condition. To utilize the motor most effectively under distorted supply condition, a proper derating of the motor is required which essentially depends on an accurate determination of the motor winding temperature. In this paper a new thermal model is proposed that not only protects the motor from overload under normal power supply condition, but also applies a proper derating factor under waveform distortion. The simulation results indicate the effectiveness of the model in the presence of different harmonics. View full abstract»

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  • Optimized Main Protection Scheme Design of 600MW Hydro Generator in Pubugou Power Station

    Page(s): 871 - 875
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (4032 KB) |  | HTML iconHTML  

    The paper analyzed all the possible faults that may happen in stator of Pubugou 600 MW multi-branch hydro generator. And transient electrical characteristics of these faults are simulated by simplified simulation model, which is constructed based on dual damper in each pole principle. Based on simulation data, the protection effects of different protection theories under different stator branch grouping modes on the neutral side are analyzed, and Pubugou generator optimized main protection scheme is proposed, which ensure the safety working for the generator and provide the references for the related engineering application and research work View full abstract»

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  • A New Wavelet Transform Approach to Discriminate Magnetizing Inrush Current and Fault Current

    Page(s): 876 - 880
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (3369 KB) |  | HTML iconHTML  

    A new approach for transformer protection based on wavelet transformation is proposed in this paper. In the proposed approach, transient current signals at both sides of a transformer are firstly captured and then analyzed by wavelet transform, from which the modular maxima (MM) are derived and subsequently used to discriminate between magnetizing inrush current and fault currents. Various types of internal faults and magnetizing inrush are modelled using real-time digital simulator (RTDS). Extensive RTDS simulations were carried out to cover various transformer operational conditions such as magnetizing inrush with various closing angles of circuit breaker, various fault types on either side of transformer, fault currents under CTs saturation during server fault conditions. The sampled current signals of both sides of a transformer are then analyzed by wavelet transform. A series of obvious characteristics are observed by decomposing the transient current signals into scale 5 (j=5) using Daubechies4 wavelet function. The multiplication of the MM on either side of transformer is then utilized to distinguish between inrush current, internal fault current and external fault current. Extensive simulation results proved that the new algorithm is simple, reliable, accurate, immune to CT's saturation, and is able to perform correctly for the worst cases where an internal fault occurs when a transformer is energized without load View full abstract»

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  • An New Directional Comparison Scheme for Distribution Line Protection

    Page(s): 881 - 885
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (3381 KB) |  | HTML iconHTML  

    This paper presents a new directional comparison protection scheme specially designed for distribution systems. A comprehensive study is performed on different directional discrimination algorithms and relaying schemes in order to assess their performances in distribution systems. An integrated solution was proposed, which combines better performed directional algorithms, such as the Negative sequence-based algorithm and superimposed component-based algorithm, etc. which together forms a new scheme to cover various system and fault conditions. Combined blocking scheme is proposed for better reliability and synchronization. Extensive EMTP simulation studies proved that the algorithm and its associated protection scheme are able to provide fast and reliable responses for all fault conditions. In particular, it is able to give correct responses adapting to the change of system operation conditions, including the changing of system configuration, power flow direction, and source and tapped-off-load conditions. View full abstract»

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  • A New Approach for Calculating Settings of Distance Relays Considering Mutual Coupling Effect

    Page(s): 886 - 889
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (2601 KB) |  | HTML iconHTML  

    This paper proposes a new systematic approach for calculating settings of all zones of ground distance relays when mutual coupling effect is considered. The proposed zone 1 setting calculation method is based on the apparent impedance seen by the ground distance relays when faults are simulated on the assumed reach of zone 1. Also, it presents a method for calculating zone 2 and zone 3 settings based on the composite current assistance parameter and apparent impedance in the paper. It is shown that the proposed systematic method guarantees the coverage of zone 1 and increases the sensitivity and accuracy of zone 2 and zone 3 settings View full abstract»

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  • Protective Relays Performance in a Harmonic Environment

    Page(s): 890 - 893
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1074 KB) |  | HTML iconHTML  

    Power system harmonics affect relay operation in many ways, they can reduce operating currents, increase or decrease operating time. Distance relays reach can be affected. This paper reviews relay performance in the presence of harmonics current the results are recorded View full abstract»

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  • Identification of Surface Discharges Over New and Aged Polymeric Chain Insulators Using a Non Invasive Method

    Page(s): 903 - 906
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (2738 KB) |  | HTML iconHTML  

    Surface discharges generated over polymeric insulators installed in power equipment and transmission lines can eventually lead to failure, as damage over the surface of affected insulation can slowly evolve into severe faults. Thus, early detection of surface discharges can avoid an important disruption of the equipment. There are several methods for the early detection of surface discharges however most of them require decommissioning of the equipment. This paper briefly illustrates the differences in the emission of surface discharges between new and aged insulators using both radiated and conducted measurements in a High Voltage Laboratory. Test equipment including antennas as a mean of detection, and digital processing techniques for signal analysis, were used. This research is a basis for the early detection and identification of surface partial discharges in power substations and transmission lines. The measurement system has the advantage that no physical connection is required, allowing the electrical equipment to remain in continuous operation View full abstract»

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  • Detection of Partial Discharges at High Frequencies

    Page(s): 907 - 911
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (4156 KB) |  | HTML iconHTML  

    This paper details a partial discharge measurement detection model that has been used to produce a test circuit suitable for detection of partial discharge at high frequencies. The circuit is designed to identify partial discharges in different insulating samples stressed by non-standard (including high frequency sine-waves and square waves). This is particularly important for the testing of equipment used in modern high voltage power electronic environments. The circuit was built and tested after carrying out simulations using the PSPICE software. The details of these simulations and the results collected are presented in this paper. The advantage of a balanced circuit measurement system is highlighted as well as the variance in predicted noise levels when different frequencies are used to energize the object under test. A comparison between the simulated circuit response and the experimental results is included View full abstract»

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  • Corona Inception in the Presence of Insulators in a Rod-Plane Gap Under Positive Switching Impulse Voltages

    Page(s): 912 - 915
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    Results are presented concerning corona inception in air and in the presence of a porcelain insulator in a non-uniform field under positive switching impulse voltages. It is shown that in the presence of the insulator both first and second coronas start earlier, under lower inception voltages and with smaller associated charges compared to corona inception in air alone. Where the insulator is present, the first and second corona inception voltages and the required voltage increase during dark period increase linearly with the applied voltage. This is not so in the case of corona inception in air alone where the second corona inception voltage was found roughly constant, independent of the applied voltage variations. The apparent first and second corona charges were found to increase with the corresponding inception voltages according to a power and an exponential law respectively View full abstract»

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  • Streamer Propagation and Flashover Along Insulator Surface in a Uniform Field in Air: Influence of Humidity

    Page(s): 916 - 920
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (468 KB) |  | HTML iconHTML  

    Results are presented concerning the influence of humidity on streamer propagation and flashover along a PTFE cylindrical insulator in a uniform field in air. Experiments were carried out in a three electrode arrangement consisting of a parallel-plane gap (12 cm), stressed by negative DC voltage and a needle in the earthed anode. Positive streamers were initiated by applying a pulse voltage at the needle electrode and propagate along the insulator surface. Streamer properties investigated are the electric field required for stable streamer propagation and the propagation velocity with field values sustaining stable streamer propagation and also under "overfields". The electric field required for flashover and the corresponding time were measured. It is shown that the electric field required for stable streamer propagation and the associated velocity increase with increasing humidity, whilst under "overfields" high humidity causes streamers to decelerate. Time to breakdown tends to decrease while the required field to breakdown increases with increasing humidity View full abstract»

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