By hvhipot 
HV Hipot Electric Co., Ltd. specializes in producing series resonance (also known as AC/DC voltage withstand test device). Next, we will share with you an introduction to AC/DC voltage withstand test.
With the continuous development of urban power grids, more and more large substations are being built to prevent external damage and meteorological conditions. Generally, substations are built as fully indoor structures, assembling busbars, circuit breakers, isolating switches, current transformers, voltage transformers, lightning arresters, and grounding switches that occupy a large area into one box, filled with SF6 gas as insulation, called composite electrical appliances, also known as GIS.
The purpose of the pressure test is to check whether the equipment is damaged and installed correctly during transportation. The GIS insulation system consists of two parts, namely SF6 gas and insulation at the interface between the gas and the insulator. Check whether there are foreign objects inside the equipment, and whether the cleanliness and insulation inside the equipment meet the specified requirements.
The variable frequency series resonant withstand voltage test device is suitable for the handover and preventive testing of high-capacity and high-voltage capacitive test samples such as power cables, power transformers, generator sets (hydro generators or thermal power generators), motors, switchgear, GIS switches, etc.
Test method and application of frequency conversion series resonance:
The variable frequency series resonance test device mainly consists of a variable frequency controller, excitation transformer, high-voltage reactor, high-voltage voltage divider, etc. Variable frequency controllers are divided into two categories: desktop controllers with 20KW and above, and portable box controllers with 20KW and below; It consists of a controller and a filter. The main function of a variable frequency controller is to convert a 380V or 200V AC power frequency sine wave with fixed amplitude and frequency into a sine wave with adjustable amplitude and frequency. And provide power for the entire equipment. The function of the excitation transformer is to raise the voltage output by the variable frequency power supply to the appropriate test voltage. The high-voltage reactor L is an important component of the resonant circuit. When the power frequency is equal to 1/(2 π√ LCX), it undergoes series resonance with the test sample CX.
The variable frequency series resonance test device adopts a fixed reactor and a variable frequency power supply, with a frequency variation range of 30-300Hz. During the test, a suitable inductance value is selected in advance according to the capacitance Cx of the tested equipment (which can be achieved by series or parallel connection of 4 reactors), and then the output frequency of the variable frequency power supply is changed to make the entire circuit in series resonance state, so as to obtain a high test voltage at both ends of the tested equipment Cx.