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The Dangers of Partial Discharge and How To Detect it Using Acoustic Ultrasound

Updated: Aug 18, 2021

According to current statistics, around 85% of power failures occur in medium to high voltage transformers. The main cause of damage in the insulation of these transformers is from specific electrical anomalies known as partial discharges. Partial discharges are localized electrical discharges in systems that can have harmful effects on equipment, resulting in power loss or insulation damage. Because of this, it is vital to be able to detect these discharges early and correct them as quickly as possible. These discharges may not create any detectable changes in temperature, but they do have a measurable acoustic signature. This means that ultrasound detectors like the UL101 can be used to detect them.

Let’s go over some of the types of partial discharge. A common type of partial discharge is called Corona; a high energy discharge that can result in mechanical, electrical, or thermal damages. These discharges are luminescent and can actually be seen in complete darkness, often glowing blue or purple. Although corona does not always indicate failure, it should be investigated when it is present. Some forms of corona can result in catastrophic failure for power management components, many of which are very expensive to replace. When detected using an acoustic ultrasound device, the “Corona Effect” can be seen by its characteristic “buzz-type” background sound, with blows on it that are equivalent to the individual discharges. We’ve included an image of this pattern below.

In many cases, tracking partial discharges in underground or closed systems can prove to be difficult and potentially dangerous. However, ultrasound can provide inspectors with valuable data by pointing them in the direction of partial discharge, without requiring them to open cell doors. This gives inspectors more data on which panels are safe to open, as well as giving them insight into the safety measures needed to open the ones with partial discharge present.

Although acoustic ultrasound can be a very valuable tool for inspection, it also does come with some drawbacks. If there is ultrasound coming from other bearings or electrical devices in the area, it may not be reliable to just use an acoustic device for inspection. For tasks like these, other equipment may need to be purchased.

Regarding the UL101 from CTRL Systems however, we do offer a full kit specifically for investigating electrical systems, as well as the Corona Detector Kit. These kits are specifically designed for detecting partial discharges and are industry leading in Signal-to-Noise ratio readings, meaning that they have the highest sensitivity for locating partial discharge.

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