Effective maintenance programs extend the life of a power transformer and valuable equipment while improving safety and reliability. Comprehensive testing services can detect potential problems with great accuracy so that a high level of performance is maintained. To accommodate the equipment’s evolving lifecycle, specified tests are completed at these stages.
- During manufacturing or remanufacturing
- After installation and on-site commissioning
- Following repairs, maintenance or servicing
- During annual inspections
- Before recycling or end-of-life disposal
Lightning Impulse Tests
The overvoltage capacity of transformers is assessed using generators that simulate electrical surges and instruments that measure the response. Impulse tests are conducted on each phase and winding. The voltage is gradually increased to levels several times higher than the ordinary operating capacity. The impulse test determines whether the equipment can withstand lightning strikes and extreme overvoltage conditions. It is a pass/fail test that requires decommissioning or repairs if faults are identified.
Low Frequency Dielectric Tests
Sustained low frequency tests are used to measure the dielectric strength, resistance and losses of specific insulating materials. This procedure is usually completed after impulse tests. It is one of the most common tests used on high-voltage equipment and transmission lines. Elevated test voltages can be applied to high-voltage mains, cables, insulators and transformers. Increased stress helps to ensure that the equipment can handle everyday conditions and extreme overages. Certain very low frequency tests measure the capacitance of high-voltage cables. This works because reduced frequencies increase the resistance substantially at much lower voltages.
In surge tests, the windings and insulating materials are subjected to extreme voltages similar to the amount of power generated by switching activities in the grid or from lightning strikes. These procedures are useful at high-risk sites although they can also be used in high voltage substation and fast track power applications. Voltage fluctuations easily damage coil windings and dielectric insulation. Surge tests may be combined with partial discharge analysis to determine whether the surge has produced flashover coronas. These tests are important because surges often exceed the equipment’s factory-specified basic impulse level (BIL). Surge tests can be completed in the factory, at the time of commissioning and during routine checks.
The Importance of High-Voltage Tests
A complete series of field tests can improve the safety and reliability of high-voltage sites. As equipment ages, the insulation weakens, and the likelihood of catastrophic failure increases. Testing programs are designed to detect and monitor potential problems before they cause unexpected outages.
For more information about developing and implementing specialized maintenance plans, contact Equisales Associates in Houston. Our firm offers field services and equipment sales that are suitable for conventional and fast-track power sites in all markets.