The frequency conversion series resonance withstand voltage test complete set is mainly aimed at AC withstand voltage tests for cross-linked cables, hydraulic generators, main transformers, busbars, GIS, etc. It has a wide range of applications and is an ideal withstand voltage equipment for prefecture, city, and county high-voltage test departments as well as power installation, repair, and test engineering units. The device mainly consists of a variable frequency control power supply, excitation transformer, reactor, capacitive voltage divider, and compensation capacitor (optional). The variable frequency series resonance test device measures AC withstand voltage by changing the inductance and frequency in the test circuit to make the circuit resonate. This method can meet the test requirements of high voltage and large current. 1. Before the test, it should be understood whether the non-destructive test items of the tested equipment are qualified, and the test should be carried out after eliminating them; 2. Adjust the protective ball gap so that its discharge voltage is 105% to 110% of the test voltage. Conduct three consecutive tests, and there should be no obvious difference. Also check the reliability of the overcurrent protection device action; 3. During the test, if it is found that the voltmeter pointer swings greatly, the tested object emits abnormal sounds, the milliammeter indication increases sharply, the tested object smokes, sparks, or the insulation surface emits continuous spark discharge, etc., the voltage should be immediately reduced, ground wire should be hung on the high-voltage side, the test site should be enclosed with barriers, warning signs should be hung, and special personnel should be assigned to supervise; 5. After wiring according to the test wiring diagram, a special person should check it to confirm it is correct, including lead-to-ground distance, safety distance, etc., before pressurization can be prepared; 6. Before pressurization, check whether the voltage regulator is at zero position. Only after confirming it is at zero position can pressurization be carried out, and the operation can only be implemented after shouting "high voltage"; 7. Reliably ground the test equipment, the shell of the tested object, and non-tested windings. For multi-oil equipment, the oil should be allowed to stand for a certain period according to relevant regulations before testing. For example, for large-capacity transformers, the oil should stand for 12-24 hours; for 3-10kV transformers, the oil should stand for 6-12 hours; 8. During the voltage increase process, monitor the changes of the voltmeter and other instruments. At 0.5 times the extra test voltage, read the capacitive current of the tested equipment; when rising to the extra voltage, start calculating the time, then read the capacitive current again. After the time is up, slowly reduce the voltage to zero, then disconnect the power supply; 9. Regarding the voltage increase speed, it can be slightly faster below 30% of the test voltage, and then the voltage increase should be uniform, approximately at 5% of the test voltage per second, or rise to the extra test voltage within 10-15 seconds; 10. If there is no clear regulation for the tested equipment, the general withstand voltage time is 1 minute; for insulating rods and other appliances, the withstand voltage time is 5 minutes. After the test, the ground wire should be hung in time, and then contact the relevant parts, which should have no heating phenomenon; 11. Before and after the test, measure the insulation resistance and absorption ratio of the tested equipment, and the two measurement results should not have obvious differences. 1. The maximum working voltage at power frequency: The insulation structure of electrical equipment must be able to withstand the maximum working voltage at power frequency for a long time during the entire operation process, usually called the maximum working voltage of the system, generally 1.15 times the rated voltage. 2. Transient overvoltage, including rising frequency voltage and resonance overvoltage. The increase of the resonant AC power frequency voltage of the series resonance withstand voltage test device is caused by the capacitance effect of the no-load line, load shedding, and asymmetric grounding. When the load is suddenly dumped, since the power supply has only one no-load transmission line, and the transmission line indicates that the current flowing through the internal resistance of the power supply becomes capacitive current. This current flows through the reactance in the system, causing the voltage to rise. Because the voltage rise is nearly 50 Hz AC voltage, it is a power frequency voltage increase. Under the action of today's relay protection, its action time is about tens of milliseconds to one second. With the long-term application of AC voltage, it has a great impact on the insulation aging of electrical equipment and the insulation structure of the power system. Resonance overvoltage is caused by resonance caused by ferromagnetic effect or nonlinear inductance elements of the iron core. Its amplitude is higher and its duration is longer. Its frequency can be the power frequency fundamental wave or higher-order harmonics. 3. Operating overvoltage is caused by the operation of circuit breakers in the power system. In a series circuit composed of resistance, inductance, and capacitance, when the capacitive reactance XC and the inductive reactance XL are equal, the phase of voltage U and current I in XC=XL is the same, and the circuit is resistive. This phenomenon is called series resonance. When the circuit is in series resonance, for example, cutting off, closing a long no-load line, cutting off a no-load transformer (pneumatic variable), etc. This overvoltage waveform is very irregular and the situation changes greatly. It can be a damped oscillation wave or a non-periodic voltage shock wave, generally reaching the maximum voltage within 1 ms. The operating overvoltage of the power system is related to the system voltage. The higher the system voltage, the smaller the voltage. For 6~35 kV systems, the voltage is about 5~4 times. 4. Lightning overvoltage: Lightning overvoltage often causes insulation damage to electrical equipment. In order to ensure the safe operation of the power system, lightning protection measures must be taken, such as installing lightning rods, lightning arresters, etc. In order to ensure that the insulation structure can withstand the above four voltages, it is necessary to conduct impulse wave voltage tests and power frequency voltage resistance tests on the insulation structure, and the insulation structure must have sufficient margin. The capacitance of the sample and the reactor forms a series resonance connection mode, and the voltage divider is connected in parallel to the tested object to measure the resonant voltage of the tested object and serve as an overvoltage protection signal.