Adaptive Relay in Microgrid - Hardware Implementation with User Interface

The increase in percentage-wise proportion of Distributed Generations is a great boon to the end consumers. However, such developments lead to major protection challenges in distribution systems. This paper describes the hardware implementation of an Interface relay, which is connected at the point of common coupling(PCC) in the micro-grid. The work includes the development of a Graphical User Interface (GUI) for the effective utilization of the proposed relay. The various functions implemented in the Interface relay are Synchronization, Islanding and bidirectional over current protection. The program is coded in the micro-controller using embedded C software. Phase locked loops (PLL) with moving average filter algorithm is used in the relay to attenuate the 100Hz ripples introduced during unbalance in the supply voltage. In the case of bidirectional over current protection, different relay operating time has been set for faults occurring in forward and reverse direction. The proposed Interface relay implemented has been rigorously tested to validate the performance based on simulation of the test signals using National Instruments waveform generation module and using Lab-View software. The test results clearly indicate the successful performance of the proposed scheme for micro-grids.