Impulse voltage test system is one of the basic items of high-voltage testing for power equipment

　　Impulse voltage test system is one of the basic items of high-voltage testing for power equipment.The impulse voltage test can be used to study the insulation performance of power equipment when subjected to atmospheric overvoltage(lightning strike),and can also be used to study the insulation performance of power equipment when subjected to operating overvoltage. 　　At the same time,many aspects such as electromagnetic compatibility research and discharge mechanism research also require impulse voltage testing.The characteristics of the impulse withstand voltage test are generally that the impulse voltage generator needs to meet two requirements:first,it must be able to output a voltage of several hundred thousand volts to several million volts,and at the same time,the voltage must have a certain waveform.

　　In order to generate high amplitude pulse voltage,the Marx multi-stage circuit invented in 1923 is still used,as shown in Figure 3-3-1.In this circuit,the 3-stage capacitors are charged to U0 by a DC voltage source in parallel through a high resistance RL,and then connected in series through synchronous discharge of the 3-stage ball gap f,thereby obtaining a pulse voltage of nearly 3 U0 on the test sample.Although the Marx circuit in practical use has multiple different circuit wiring,the basic principle is the same.

　　According to actual measurements,lightning waves are non periodic pulses with statistical parameters.Its wavefront time(approximately the time required to rise from zero to peak)is 0.5-10μs.The half peak time(approximately the time required to rise from zero to the peak and then drop to half the peak)is 20-90μs.The wavefront and half peak time with a cumulative frequency of 50%are approximately 1.0-1.5μS and 40-50μS.

　　The duration of the operating impulse voltage wave is much longer than that of the lightning impulse voltage wavelength,and its shape is more complex.Moreover,its shape and duration vary depending on the specific parameters and length of the circuit.However,currently,there is a trend internationally to use a long pulse with a few hundred microseconds of wavefront and several thousand microseconds of wavelength to represent it.