Cable resonance withstand voltage test
The resonant voltage withstand test method is to change the inductance and test frequency of the test system, so that the circuit is in a resonant state, so that most of the capacitive current on the test circuit and the inductive current on the reactor are offset, and the energy supplied by the power supply is only the study power consumed in the circuit, which is 1/Q of the capacity of the test product (Q is the resonant multiple of the system). Therefore, the capacity of the test power supply is reduced, and the weight is greatly reduced. The resonant withstand voltage test system can be divided into two kinds according to the regulation mode: the modulated induction type and the modulated frequency type.
The adjustable inductance type resonant test system can meet the requirement of withstand voltage, but because of its large weight and poor mobility, it is mainly used in the laboratory. Frequency conversion series resonance voltage withstand test uses the inductance of the reactor and the capacitance of the subject to achieve capacitor resonance, and obtains high voltage and high current on the subject. It is a new method and trend of high voltage test at present, and has been widely used at home and abroad.
Frequency conversion series resonance is a resonant current filter circuit, which can improve the waveform distortion of the power supply, obtain a better sinusoidal voltage waveform, and effectively prevent the harmonic peak to the test product. Frequency conversion series resonance works in the resonance state, when the insulation point of the subject is broken down, the current is immediately detuned, and the loop current rapidly drops to one tenth of the normal test current. When a flashover breakdown occurs, due to the loss of resonance conditions, in addition to the short circuit current immediately decreases, the high voltage also immediately disappears, and the arc can be extinguished. The re-establishment process of the recovery voltage is very long, and it is easy to disconnect the power supply when the flashover voltage is reached again, so it is suitable for the insulation withstand voltage test of high voltage and large capacity power equipment.
The frequency conversion resonance test system can not only meet the requirements of high voltage XLPE cable, but also has the advantages of light weight and good mobility, which is suitable for field test. After analysis and comparison, the frequency conversion series resonance test device uses a fixed reactor as a resonance reactor to achieve resonance in the way of frequency modulation, the frequency adjustment range is 30~300Hz, in line with the national standard "Electrical equipment handover test Standard" (GB50150-2006) recommended to use a frequency of 20~300Hz resonance voltage test.
Notes on resonance withstand voltage test
(1) Most of the resonant power supply products are high-voltage test equipment, which is required to be used by high-voltage test professionals, and should be carefully read the instruction manual before use, and repeated operation training.
(2) The operator shall be no less than 2 persons. When used, the unit should strictly abide by the safety operation rules of high-pressure test.
(3) In order to ensure the safety and correctness of the test, in addition to being familiar with the product manual, the test operation must be carried out in strict accordance with the relevant national standards and regulations.
(4) Each connection line can not be connected wrong, especially the ground line can not be connected wrong, otherwise it can cause damage to the test device.
(5) When the device is used, the output is high voltage or ultra-high voltage, must be reliably grounded, pay attention to the safe distance of operation.
(6) Series resonance test system is the use of resonant reactor and the test product resonance to produce high voltage, that is to say, can produce high voltage is mainly to see whether the test product and resonant reactor resonance, so the test personnel in the analysis of the site can not produce the required high voltage, should analyze what damage the resonance conditions, the loop is connected and so on.
(7) The series resonance test system of the excitation transformer has specific voltage and current requirements, in the selection of substitutes, must consider the voltage and current, can not use just the same capacity of the ordinary test transformer.
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