What Tests Are Required for a Qualified AIS Voltage Transformer?

Hey everyone! I’m Oliver, an experienced electrician with over a decade in the power system industry. Today, we’re diving into a practical topic — what tests are required to ensure an Air Insulated Switchgear (AIS) voltage transformer is qualified? These tests are crucial not only for ensuring the device operates correctly but also for maintaining the safety and stability of the power grid. Let’s get started!

1. Visual Inspection
First Look Matters

The very first step is a visual inspection. Don’t underestimate this step; many obvious defects can be spotted here.

• What to Check: Look for cracks on the casing, check if seals are intact, and ensure all labels are clear.
• Why It Matters: Addressing these issues upfront can prevent various problems later, such as oil leaks or water ingress.

2. Insulation Resistance Test
How Good Is the Insulation?

Next up is the insulation resistance test. This test confirms whether the insulation parts of the voltage transformer are still effective.

• How to Do It: Use a megohmmeter to measure the insulation resistance between different parts.
• Standard: Typically, the insulation resistance should be no less than 500 MΩ (the exact value varies based on the equipment and application environment).
• Why It Matters: Good insulation is fundamental to preventing electrical accidents.

3. Withstand Voltage Test
Can It Handle High Pressure?

Then comes the withstand voltage test, also known as the high-voltage test. This test verifies whether the voltage transformer can safely operate at specified voltage levels.

• How to Do It: Apply a voltage higher than the rated voltage by a certain multiple and observe for any breakdown during the holding period.
• Why It Matters: Ensures the device can operate stably under high voltage conditions in real-world applications, avoiding damage due to overvoltage.

4. Error Test
Is the Measurement Accurate?

For voltage transformers, the error test is one of the most critical steps. After all, its job is to accurately convert voltage signals.

• How to Do It: Compare the output voltage against the input voltage using standard sources and high-precision measuring instruments.
• Standard: Generally, the error should be within ±0.2% (varies depending on the application scenario and grade).
• Why It Matters: Ensures accuracy for metering and protection functions.

5. Temperature Rise Test

How Stable Is It Under Heat?

Another often overlooked but essential test is the temperature rise test. This evaluates the thermal stability of the voltage transformer during prolonged operation.

• How to Do It: Run the transformer at its rated load for a certain period and record temperature changes.
• Standard: The temperature increase should not exceed specified limits to avoid affecting the lifespan of insulating materials.
• Why It Matters: High temperatures can impact the life and safety of the equipment.

6. Partial Discharge Test
Any Hidden Dangers Inside?

Finally, we can’t ignore the partial discharge test. This test helps identify potential internal issues within the device.

• How to Do It: Use specialized equipment to detect the presence of partial discharges.
• Standard: The level of partial discharge should be below a specific threshold to ensure long-term operational safety.
• Why It Matters: Partial discharges can be precursors to insulation failure, and detecting them early can prevent major faults.

Conclusion

In summary, a qualified AIS voltage transformer must undergo a series of rigorous tests before being put into service. These include visual inspection, insulation resistance test, withstand voltage test, error test, temperature rise test, and partial discharge test. Each step is critical, and any issue in one of these areas could lead to malfunction or even safety incidents.

I hope this article helps fellow professionals! If you have any questions or want to share your experiences, feel free to leave a comment or send me a message. Let’s learn together and improve collectively!

—Oliver