Recently, the Wuhan UHV after-sales service team received an after-sales invitation from Beijing Electric Power Engineering Co., Ltd. to provide technical support for several instruments such as UHV series resonance test device, GM-5kV adjustable high-voltage digital megohmmeter, ZGF DC high-voltage generator, UHV-8003 partial discharge detector and UHV-525 transmission line fault distance tester.

Subsequently, Wuhan UHV technicians and Yang Gong, the on-site tester of the customer company, agreed on the time, arrived in Yuzhou City, Henan Province in the morning of the same day, and went to the project site in the afternoon to check the situation of the test products. The test samples include 110kV cable and 110kV zinc oxide arrester. The three-phase 380V power supply cannot be found in the field environment, so it is necessary to prepare a generator to supply power to the resonant equipment.

In the afternoon, after all the preparations are in place, the trial officially begins. The service is carried out in the mode of explanation and operation, and the resonance is composed of a frequency conversion source, an excitation transformer, a reactor, and a voltage divider. The test voltage of the 110kV cable is 128kV, and the reactor of Wuhan UHV is 27kV and has 6 sections. The capacity of the device is set at 405kVA, divided into five reactors, and the single section of the reactor is 67.5kVA/2.5A/50H.

Verification: 1. AC withstand voltage test of 110kV/1200mm² length 0.35km cable, capacitance ≤ 0.0847uF, test frequency 30-300Hz, test voltage 128kV, running time 60min.

Five reactors are used in series, L=50×5×1.2=300H

Test frequency: f=1/2π√LC=1/ (2×3.14×√300×0.0847×10-6) =31.57Hz

Test current: I=2πfCU test =2π×31.57×0.0847×10-6×128×103=2.02A

By calculating the Wuhan UHV technicians, it was concluded that at least 5 reactors were needed to complete the test, and 6 reactors were used here, mainly because of the detection of other test equipment. After the wiring is completed, turn on the machine, select the parameter settings, you only need to change the test voltage and withstand voltage time, the test voltage is 128kV, and the withstand voltage time is 60 minutes. Enter the manual test interface, confirm the wiring and safety again, click to start the test after confirmation, click to tune, the instrument will automatically find the frequency, when the resonance point is found, click to boost until 128kV and wait for the end of the test. In the withstand voltage, Wuhan UHV technicians use UHV-8003 partial discharge detector to detect partial discharge of cables. After the withstand voltage is completed, the cable insulation test and line parameter test are carried out again, and finally the DC characteristic test of zinc oxide arrester is carried out. After all the equipment was tested in turn, the customer's testers used the equipment again to carry out various tests independently on other test points, which were all well completed. So far, the after-sales service journey has ended successfully!