What Are the Types of Switchgear Testing?

Switchgear must be able to cope with disturbances caused by unavoidable factors and be able to carry fault currents in case of problems in the system. 

They must also be able to withstand voltages under normal and abnormal conditions and carry different load currents throughout their operating life. 

Switchgear testing is done to discover possible risks and ensure that the equipment meets these requirements.

All switchgear performance, both under normal and abnormal conditions, must be validated through various tests that refer to the parameters described in national and international standards, as well as various possible practical situations.

Equipment testing begins with various steps, during which the manufacturer verifies each relevant parameter to guarantee good performance in the long term. 

In accordance with the various voltage levels and specifications listed in IEC 62271-100 and IEC 62271-200, we can choose from the various switchgear testing methods available.

How often should Switchgear be tested?

Switchgear should be tested annually to ensure that they are performing at their best. Preventive maintenance and regular testing are essential to extend the life and performance of your switchgear system. 

In addition to regular mechanical and insulation testing, visual inspections are also necessary to spot discoloration on components or debris buildup. Addressing these minor issues can help keep the switchgear operating properly.

In addition, it is very important to promptly repair physical damage and unsatisfactory test results to keep the system in good working order. Every year, you should inspect and test several important components of the switchgear. 

This includes breakers, switches, wiring points, insulation, and disconnects, as well as ensuring that mounting bolts and terminations are tight. In addition, you should check the thermostat and temperature control panel to ensure that everything is working properly.

If not addressed promptly, small issues can develop into significant problems. During maintenance checks, rust, corrosion, and damaged insulation can be easily identified and repaired.

Therefore, performing regular switchgear inspection and maintenance can offer the following advantages:

1. Preventing failure: As long as the equipment is functioning until it fails, replacing parts is only necessary once the indicator light comes on. Regular testing identifies possible faults and extends component life.

2. Saves costs: Regular maintenance saves money on expensive emergency repairs.

3. Improves Performance: By ensuring that equipment is functioning properly and has been tested, you can improve overall electrical system performance by maintaining the highest level of operational efficiency.

Types of Switchgear Testing

Here are some types of Switchgear testing:

Dielectric Tests

Sometimes, power systems face overvoltage at their power frequency, which can result from load shedding, errors in transformer OLTC operation, inadequate shunt compensation, resonance, and others. 

Dielectric testing is performed to ensure that the circuit breaker (PMT) design can cope with these events, as well as other situations such as lightning, switching operations, and so on.

This is verified in accordance with applicable standards.

a. One-Minute Dry-Power Frequency Voltage Withstand Test

This test aims to verify the equipment's ability to withstand the test voltage at the power frequency for one minute under dry conditions. The power frequency test voltage value used is compared to the system voltage specified in the standard.

b. One-Minute Wet-Power frequency Voltage Withstand Test

This test is similar to the one-minute dry power frequency voltage test, but is conducted under humid conditions. This test is only applied to outdoor installations, where equipment may be exposed to higher humidity conditions. 

The purpose of this test is to ensure that the switchgear can withstand power frequency voltages even in a humid environment, which can affect the performance of insulation and other components.

c. Lightning Impulse Voltage Dry Withstaand Test

With a standardized peak value (1.2/50μs), this test examines the ability of the switchgear to withstand overvoltages generated by lightning impulses. Lightning impulses can cause very high voltage spikes. 

The purpose of this test is to ensure that the switchgear can operate safely and remain stable when exposed to extreme lightning impulses.

d. Switching Impulse Voltage test

This test is carried out to determine whether the switchgear is strong enough to withstand the voltage spikes generated by the settings. For systems with voltages over 300 kV, this test is very important. 

During the opening and closing process of EHV lines or connected lines, as well as inductive/capacitive load breakers, switching voltage surges occur. 

Standard switching impulse test waves with a duration of 250/2500 μs are usually used to describe these switching surges, which are relatively longer (around 2500 μs) and have a lower rate of rise.

e. Partial Discharge Test

In cases where the switchgear design itself consists of a combination of conventional compositions, such as CT and VT, where yag can be tested to their respective standards, the partial discharge test is not recommended to be performed on the complete switchgear. 

However, this test is recommended for switchgear that uses organic insulating materials. This is seen in integrated switchgear designs, particularly for GIS, where the live parts and connections are embedded in solid insulation.

f. Artificial Pollution Test

This test is only performed in outdoor installations and is usually done as agreed between the user and the manufacturer. The voltage values used in this test are calculated using system voltage standards.

g. Switchgear Design Aspect

When designing switchgear, components that have different electrical potentials must be separated separately to maintain the safety of employees working nearby and maintain their operational reliability.

Three main functions of isolation in switchgear:

- Separates current-carrying live parts from earth,

- Maintains contact distance when the breaker condition is open;

- Separating active parts that carry current from different phases.

h. Electrical Operation Test

According to IEC 60439, 8.3.1, electrical operation tests for equipment attached to switchgear and MCCs (such as circuit breakers, magnetic contactors, switches, and relays) should be performed by providing a combination of simulated input and output circuits. 

Thereafter, the operation of the devices should be verified to ensure that they function properly as expected.

i. Sequence Test

The electrical sequential operation test of the device is conducted to ensure that the electrical system in the switchgear and MCC has been properly structured and connected according to the approved schematic diagram.

This test also aims to ensure that the device operates as intended.