What is Partial Discharge Testing?

Partial discharge testing is a method used to assess the condition of electrical insulation systems in high-voltage equipment, such as transformers, cables, and switchgear. Partial discharge occurs when a small amount of electrical discharge occurs within the insulation system due to the presence of voids, cracks, or other defects.

Partial discharge testing is used to identify and locate these defects before they can cause insulation failure or other problems. The testing involves applying a high voltage to the equipment and monitoring the electrical activity using sensors or other instruments. The results of the testing can be used to evaluate the condition of the insulation system and to plan any necessary maintenance or repairs.

Partial discharge testing is an important diagnostic tool in the maintenance of high-voltage equipment, as it can help prevent unexpected failures and ensure the safety and reliability of the equipment.

Causes of Partial Discharges

Partial discharges in electrical insulation systems can be caused by a variety of factors, including:

1. Impurities in the insulation material: Impurities such as moisture, dust, and other contaminants can cause partial discharges in the insulation.
2. Mechanical damage: Physical damage to the insulation system can create voids or cracks that can lead to partial discharges.
3. Ageing and deterioration: Over time, insulation materials can degrade due to exposure to heat, moisture, and other factors. This can lead to partial discharges.
4. Electrical stress: High electrical stresses, such as those caused by voltage spikes or lightning strikes, can cause partial discharges in the insulation system.
5. Poor installation: Improper installation of the insulation system, such as inadequate clearance or incorrect cable termination, can create conditions that lead to partial discharges.
6. Manufacturing defects: Defects in the manufacturing process, such as poor quality control or improper assembly, can lead to partial discharges in the insulation system.

Partial Discharge Testing can be carried out in two ways

Offline Partial Discharge Testing

Offline partial discharge testing is conducted when the equipment is offline, meaning it is not in service and is not energized. The equipment is usually disconnected from the electrical network and taken to a testing facility. Offline testing is typically more thorough than online testing, as it provides a more controlled environment for testing and allows for a more comprehensive analysis of the results.

Online Partial Discharge Testing

Online partial discharge testing is conducted when the equipment is in service and operating under normal conditions. Online testing typically involves using sensors or other instruments to monitor the equipment while it is in service. This method of testing is less disruptive and allows for more frequent monitoring of the equipment, but the results may be less comprehensive than offline testing.

Who needs to carry out Partial Discharge Testing?

Partial discharge testing is typically carried out by electrical engineers or technicians who have specialized training and experience in testing and diagnosing electrical insulation systems. These professionals may work for equipment manufacturers, electrical utilities, or other organizations that operate and maintain high-voltage equipment.

It is important to note that partial discharge testing should only be carried out by qualified professionals who are familiar with the equipment being tested and the specific testing methodology being used. Improper testing can lead to inaccurate results and potentially dangerous situations.

This testing is an important aspect of the maintenance and safety of high-voltage equipment, and it is recommended that testing be performed regularly according to industry standards and best practices. The frequency of testing may vary depending on factors such as the age of the equipment, the operating conditions, and the level of risk associated with the equipment.