Preventive Testing in High-Voltage Distribution Rooms: Key Items and Methods

Preventive testing is a critical procedure to ensure the safe and reliable operation of electrical equipment in high-voltage distribution rooms. By identifying insulation issues and early defects, this approach helps prevent unexpected equipment failures, power outages, or severe damage caused by working voltage or overvoltage conditions. Tailored to the unique requirements of each distribution room, the following key testing categories and methods are essential:

1. Transformer Testing

Transformers are vital components requiring regular assessment. Key testing procedures include:

1. Insulation Resistance Measurement

   • Utilize a 2500V megohmmeter to measure insulation resistance before testing and during the voltage withstand process.

2. DC Resistance Measurement

   • Measure resistance on the high-voltage side (phases 1, 2, 3) and the low-voltage side using an electric bridge or DC resistance tester.

3. Transformer Oil Breakdown Voltage Test

   • Conduct this test three times and calculate the average value for accuracy.

4. Withstand Voltage Test

   • Apply a 30kV power frequency voltage for one minute to evaluate the transformer's voltage endurance.

5. Core Inspection

   • Perform this inspection when necessary to assess internal conditions.

6. Testing Frequency

   • Conduct tests every two years as per standard guidelines.

2. Power Cable Testing

Power cables are crucial for electricity distribution, requiring regular checks to maintain integrity. Specific tests include:

1. Insulation Resistance Measurement

   • Use a 2500V megohmmeter or digital equivalent to test inter-phase insulation for one minute before the DC withstand voltage test.

2. Power Frequency Voltage Test

   • Gradually increase the test voltage to 50kV and maintain it for five minutes without breakdown, ensuring the leakage current remains below 50 μA.

3. Testing Frequency

   • Conduct this test cycle every 1-3 years based on operational requirements.

3. High-Voltage Electrical Equipment Testing

Testing high-voltage equipment such as switchgear involves the following procedures:

1. Insulation Resistance Measurement

   • Test the insulation resistance between phases, busbars, transformers, circuit breakers, and ground.

2. Voltage Withstand Test

   • Perform this test on busbars, transformers, circuit breakers, and insulators to verify operational safety under high voltage.

3. Testing Frequency

   • Conduct testing every 1-3 years.

4. Relay Protection Debugging

Relays are critical for system safety and require meticulous testing, including:

1. Mechanical Inspection

   • Check components such as turntables, gears, and contacts for wear or damage.

2. Calibration and Recordkeeping

   • Set and record parameters such as starting current, constant current, tripping current, and quick break current.

3. Circuit Breaker Testing

   • Perform rated tripping tests, including opening, closing, and tripping functions.

4. Testing Frequency

   • Conduct these tests annually.

5. Grounding Resistance Testing

Grounding systems are essential for electrical safety. Testing involves:

1. Resistance Measurement

   • Measure grounding electrode resistance using a dedicated tester. The resistance must remain below 1 ohm.

2. Testing Frequency

   • Conduct this test annually. Note: A power outage is required for testing, and accessories like 15M/30M wires, grounding poles, and connecting ground wires are necessary.

6. Protective Equipment Testing

To ensure operator safety, protective equipment must undergo annual testing. Key items include:

1. Insulated Tools

   • Test high-voltage insulated gloves, boots, switch rods, and voltage testers to verify their insulation performance.

2. Lightning Arrester Testing

   • Perform breakdown voltage tests on lightning arresters. For older valve-type arresters, the testing cycle is every two years.

Conclusion

Regular preventive testing in high-voltage distribution rooms is essential to minimize operational risks, ensure equipment reliability, and maintain electrical safety. By adhering to specified methods and schedules, operators can prevent costly failures and ensure optimal performance across all components.