Abstract:

The neutral point displacement of the three-phase four-wire system caused by the zero-phase open circuit,which leads to the over voltage damage of the equipment by power users,is still a pain point in the power supply sector.With the increase of the user’s harmonic load,there are more and more accidents that cause zero-phase open circuit overvoltage due to the zero line overburning,Only that terminal users install voltage protection circuit breakers can it solve this problem.However,the overvoltage protection circuit breakers are expensived to be widely applied.This paper proposes a zero-phase open circuit protection scheme using zinc oxide varistor combined with existing residual current protection devices for single phase user.In the case of zero-phase open circuit overvoltage,it can complete the reaction action quickly and reliably to protect the circuit,and has a low cost,which has very good practical value.

Key words: zinc oxide varistor, overvoltage protection circuit breaker, harmonic load, residual current protection devices