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How Does Partial Discharge Detection Work On Switchgears?

It is always important to conduct tests and do maintenance for your equipment, this includes all kinds of equipment, from generator maintenance, power transformer repair to switchgear maintenance.

Over the years, studies have shown that more than 85% of disruptive failures in both medium voltage (MV) and high voltage (HV) equipment and machinery are Partial Discharge related. So, if you still insist that your switchgear doesn’t need any tests or maintenance, then it’s time you take a second thought as a failure in your switchgear can ultimately cause severe damage to the switchgear itself, along with other related equipment. In worst cases, it may even cause harm to your staff.

You may have heard of partial discharge (PD) detection but not know of how it works, let alone its effectiveness. However, there is nothing wrong with that as we are bound to encounter something new every day. Below, you’ll find out what partial discharge detection is all about, from understanding the different types of tests to how it works on switchgears.

What Is Partial Discharge Detection?

Partial Discharge Detection is when a test is done on the switchgear to obtain critical information on the quality of the switchgear and the impact that it has on your critical facility. By doing this test, you will be able to determine your switchgear’s condition and it basically allows you to prioritize maintenance resources and take action before any system failure occurs.

Types of Partial Discharge Testing

Online Partial Discharge Testing

This predictive maintenance tool allows you to assess the condition of the switchgear, whether it’s about the levels of partial discharge or its potential impact on the health of the equipment. Compared to offline testing which requires interruption of service and production, it is considered relatively inexpensive to perform online testing.

If you need your switchgear to operate all round the clock, then it is best to use this option.

Permanently Mounted Sensors

These High Frequency Current Transformers (HFCT) are best used for areas that require employees and staff to be more careful or are hard to access to conduct periodic online partial discharge detection. They are installed on the machinery during a plant downtime or outage to gain access to the machine online and information about the condition of the equipment.

After the installation is done, no further disruptions or outage are needed for any other online testing.

Continuous Online Monitoring

However, a permanently mounted PD monitoring system may not always be the answer, and when that happens, you should consider doing continuous online monitoring instead when you only plan to monitor the system for a short period. It is also excellent for critical equipment which displayed a high amount of partial discharge, including equipment that are not able to function soon enough.

Continuous online monitoring allows you to obtain specific information on the capability and condition of the machinery, while also alerting you on any required maintenance and failures that need to be fixed.


Whatever problems that occur in the electrical equipment, in particular, medium and high voltage ones, like corona and partial discharge, are able to detect the sound waves that are created by these problems which can be detected by this test.

Similar to online partial discharge testing, it can be performed on the machine without causing any disruption to the plant or facility operations as makes sure that the insulation integrity is maintained.

Offline Partial Discharge Testing

This test can measure the switchgear’s reaction to a particular stress level and anticipate its performance in the future without causing an error or fault. Additionally, offline partial discharge testing can also determine where the defect is on various field-aged machinery, allowing the engineer to get ready any repair or maintenance.

However, the constant challenge with this test is the fact that it can only be done offline and when the machine is out of service.

Although extensive research and knowledge obtained online about partial discharge on switchgears are always useful, it may not be substantial as it is always best to seek an expert in this field, such as Maintech Engineering and Supplies (MES) who handle all sorts of services from generator rewinding repair, switchgear maintenance to electric motor installation.

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