The specialized production ofpartial discharge testersfor UHV power can help many power workers conduct various power tests more conveniently.

It is not recommended to use a thermal imager for partial discharge inspection

The thermal imager observes the infrared energy emitted by the target object. This electrical inspection means that we are searching for overheated electrical assets. For example, loose and corroded connections can generate higher resistance, resulting in higher temperatures, or unbalanced loads due to phase to phase temperature differences, or reduced liquid levels due to transformer oil leaks, which can be evident when using thermal imaging instruments correctly.

However, partial discharge is a problem with thermal imagers. Thermal imaging depends on the current, and its power is proportional to the current multiplied by the square of the resistance (higher current leads to higher temperature, and higher resistance also leads to higher temperature). Partial discharge can cause insulation overheating, and repeated occurrences can result in cumulative effects, leading to damage and eventual failure. However, its distance is short and its speed is fast (with a duration of a few microseconds every few milliseconds), so only in severe extreme advanced situations, such as the advanced arc stage of corona, has the opportunity to absorb heat through thermal imagers or even high-quality models. Internal partial discharge (i.e. inside the insulator) is highly unlikely to be picked up.

Insulation deteriorates with age. Other factors may lead to premature failure, such as moisture, dirt/contamination, poor craftsmanship, and/or defective materials. At the point of degradation, insulation failure occurs when it is unable to withstand the electric field applied to it and malfunctions. This is a voltage event. Taking an extreme example, consider a backup medium voltage cable with surface partial discharge, which is powered but actually has no load and still emits ultrasonic waves and UHF by-products.

In short, IR testing and PD testing methods are complementary technologies for detecting different types of electrical faults.