Variable Frequency Series Resonance Test/Variable Frequency Resonance System - Test Precautions?

The following are the test precautions for variable frequency resonant systems:

I. Detailed Preparation Before the Test

1. Parameter Matching Calculation: Accurately estimate the capacitance of the test sample and calculate the resonant frequency range. Select appropriate reactor combinations based on the equipment's rated parameters to ensure the system resonant point falls within the effective operating frequency band of the frequency converter.

2. Comprehensive System Inspection: Check that the connections of components such as the frequency converter power supply, excitation transformer, reactors, and voltage dividers are reliable, and that the insulating surfaces are clean and dry. Pay particular attention to ensuring good heat dissipation and ventilation of the frequency converter.

3. Reliable Grounding: Each component in the system must achieve reliable single-point grounding. The cross-sectional area of the grounding wire must be sufficient (≥25mm²), and the grounding resistance must meet the requirements.

II. Precise Control of the Test Process

1. Frequency Scanning: Perform automatic or manual frequency scanning at a low output voltage (≤3kV), slowly adjusting the frequency to find the resonant point (the point of maximum current). Frequency scanning is strictly prohibited when approaching the test voltage.

2. Segmented Voltage Increase: After finding the resonant point, maintain frequency stability and increase the voltage smoothly in stages. Observe the system at each stage and continue increasing the voltage only after confirming stable system operation.

3. Full-Process Monitoring: Closely monitor changes in output voltage, current, frequency, and power. Pay special attention to the inverter's operating status; immediately reduce voltage and shut down the system if any abnormal alarm occurs.

III. Special Precautions

1. Electromagnetic Compatibility: Shielded cables must be used for measurement and reliably grounded to reduce the impact of high-frequency interference from the inverter on the measurement system.

2. Protection Settings: Correctly set overvoltage, overcurrent, and flashover protection parameters in advance to ensure accurate and reliable protection actions.

3. Heat Dissipation Management: Monitor the inverter's heatsink temperature during long-term testing to ensure the cooling system is functioning properly.

IV. Post-Test Procedures

• After the test, reduce the voltage to zero before disconnecting the power supply. Fully discharge the test sample and high-voltage system; the discharge time should be longer than in routine tests.

In summary, variable frequency resonant testing requires special attention to the accuracy of parameter matching, the stability of frequency adjustment, and electromagnetic compatibility protection. Careful operation is essential to ensure the safety and effectiveness of the test. The MSXB-F-1000kVA 500kV variable frequency resonant system is primarily designed and manufactured for AC withstand voltage tests on 35kV, 110kV, and 220kV cables, 110kV and 220kV switches, transformers, insulators, etc., as well as the neutral point of 220kV main transformers and the line terminals of 110kV main transformers. It has a wide range of applications and is an ideal withstand voltage testing device for municipal, county, and prefecture-level high-voltage testing departments and power installation and maintenance engineering units. The device mainly consists of a variable frequency power supply, excitation transformer, reactor, capacitive voltage divider, and compensation capacitors.

1. Circuit breakers, PTs, CTs, and insulators of 220kV and below: test frequency 30-300Hz, test voltage 500kV, test time 1min

2. 110kV/630mm² cable, 1km ≤0.201uF: test frequency 30-300Hz, test voltage 128kV, test time 60min

3. Circuit breakers, PTs, CTs, and insulators of 110kV and below: test frequency 30-300Hz, test voltage 270kV, test time 1min

4. 110kV 5. Main transformer terminal, capacitance ≤0.015uF, test frequency 45-65Hz, test voltage 160kV, test time 1min

6. 220kV/300mm² cable 0.5km, capacitance ≤0.086uF, test frequency 30-300Hz, test time 60min

7. 35kV/630mm² cable 3km, capacitance ≤0.76uF, test frequency 30-300Hz, test voltage 52kV, test time 60min

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