Features of fault transient's in generator network of powerful electric power stations

THE PURPOSE. To consider the problems of generator circuit breaker. To consider the problems of high degree of asymmetry of short-circuit current and long delayed current zeros in detail. Propose methods for solving these problems. Develop the equivalent electrical circuit model of electric power station. This model should demonstrate the above-mentioned problems and effectiveness of the proposed solving problems methods. METHODS. The fault transient’s simulations have been performed by means of the software package Matlab Simulink. RESULTS. The equivalent electrical circuit model of electric power station was proposed and developed. This model allows simulating the short circuit currents from a synchronous generator. Short-circuit current waveforms are obtained. These waveforms describe the problem of high degree of asymmetry and long delayed current zeros phenomenon. Proposed decision on using thyristorbased hybrid circuit breaker with PTC-thermistor-based current limiting device. For equivalent electrical circuit the PTC-thermistor model was developed. Short-circuit current waveforms when applying PTC-thermistor-based current limiting device are obtained. CONCLUSION. The simulation results showed that the effect of long delayed current zeros (when the current does not pass zero at its nearest minimum) is not typical for high-power synchronous generators (PSG > 300 MW). This effect can occur when the synchronous generator is operating in the reactive power compensation mode. At the same time, there should be no additional electric resistance (for example a gas electric arc). The use of PTC-thermistor for thyristor-based hybrid circuit breaker will reduce energy of short circuit current on ~25% and it will completely protect the circuit breaker from does not pass zero current. This will increase reliability of thyristor device for hybrid generator circuit breaker.

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