In this paper, according to characteristics of high frequency short pulses electrochemical machining (HSPECM), we describe a quick short-circuit protection circuit designed HSPECM power.

The new quick protection device can guarantee an effective protection against the recovery voltages after discharge by shortcircuiting the primary terminals of testing transformer via current limiting chokes in a very short time.

It has been safely operating in the fast protection for 13kw/500Hz GTO dc chopper and 15kw/10kHz medium frequency induction heating power supply employing GTO.

According to the characteristic of the laser diode load and it s power,the design of hardware and software can provide much fast protection to avoid the error of over current,load,module and cooling system,These can raise the level of the reliability.

Improving rotor grounding protection of small units by integrated use of 7UM62 and ZD-9 devices;

Based on principles of rotor grounding protection and formation of shaft voltage,this paper explains relationships between rotor point 1 grounding protection misoperation with shaft voltage and main shaft grounding.

This paper analyzes the influences of shaft voltage absorbing circuit and brush touching resistance on the performance of generator rotor earth fault protection.

The principle and characteristic of voltage injection at rated frequency and a square wave voltage injection at lower frequency are introduced for rotor earth fault protection of turbine generator.