Study On Injection Voltage Scheme For Stator Single Earth-fault Protection Of Generator

With the increament of generator capacity, the requirement of stator single earth-fault protection is becoming more and more high for generator. The injection stator earth-fault ground protection are a widely application foreground because of its predominant highlighted. The first, this paper analyzes the characteristic of 20Hz injection protection in the protective device of SIEMENS and proposes a improved scheme for its limitation. Then it analyzes the grounding styles'different effects on the sensitivity of the stator ground protection and proves that the equivalent parameters of the grounding transformers influence the measurement of the earth-resistance. This paper also analyzes the choise of injection frequency and gave an ideal rang of it after the digital simulation. Otherwise,it also analyzes the difference between grounding with equivalent circuit of exciting impedance and extingguishing coil at the neutral.