Study On Shunt Capacitors Protection Relay And Its Realization Based On DSP

As an important reactive compensation device, shunt power capacitor are applied in power systems widely. According to statistics, many kinds of different faults occur, when capacitors are run, showing traditional protection relaying schemes have limitations and disadvantages. Now integrated intelligent devices are developing, which contain many functions, such as measurement, protection, control and remote control. These devices are powerful means to resolve the problems of capacitors' effective run and its protection.This paper focuses on computer relaying research and its realization of 110kV and below voltage class shunt capacitors. Fist, protective relaying philosophies are analyzed and researched. Some traditional protective relaying schemes' limitations and disadvantages have been given and overcome in this paper. For example, H-bridge different current protection scheme and unbalance current protection scheme in double-wye connected capacitors mask balanced failures and have no indication of involved phase. A new approach is given that can overcome the disadvantages.As for computer relaying algorithms, considering characteristics of capacitors, Full-wave Fourier algorithm is adopted. Combined with different filter and zero filter, this algorithm eliminates the influence caused by decaying DC component and frequency excursion.As for the function of communication, Can field bus is used, which has high reliability and good real time. The function of communication is realized by designing periphery circuit based on Motorola 56F807 DSP and programming software.Based on Motorola56F807 DSP with high performance, both C and assemble languages are adopted to program. By associated debugging of software and hardware, this protection device has such functions as over-voltage protection, over-current protection, unbalance voltage protection, unbalance current protection, under voltage and zero-sequence over current protection. Meanwhile it provided other functions such as signal detecting, man-machine information exchanging, remote control communication, self-detecting, synchronous time and defaults recording.