The 3-phase short-circuit braking method for 3-level inverters is analyzed and discussed in details, which is widely used in the inverter-motor system.

Discussion of three-phase short-circuit criterion of phase selection relay based on delta variable element of phase current differential;

Based on this model,three-phase short-circuit of synchronous machines are emulated and computed .

Analyzes the cause of 6kV common box bus-bar three-phase short-circuit fault at No.

The three-phase short circuit currents of bulk electric power system are very high,and the high currents do harm to the working of the system.

Firstly,an example of three-phase short circuit is given.

De-excitation of steam-turbine generator after abrupt three-phase short circuit(ATPSC)is serious situation.

With analysis of electrodynamics force about three-phase short-circuit current,after stress analysis,the appearance of short huge electrodynamics force influence outdoor post-mounted vacuum circuit breaker greatly.

In short-circuit current calculations for Jiangsu Power Grid,it was found that the single-phase short-circuit current was bigger than the three-phase short-circuit current of 220 kV buses in some 500 kV substations and even exceeded the rated breaking ability of circuit breakers.