Low Voltage Switchgear Standards and Testing

Generally all Switches, Switch Disconnectors, Disconnectors and Fuse combination units are designed to comply with the requirements, Standards and Testing. All are comply with the requirements of IEC 947-3 or EN 60947-3. This is also requires a combination of type tests and routine tests before installation. For this reason normally a sequence of type tests is required to prove that it compliance with the standard. In this post we will learn about the Low Voltage Switchgear Standards and Testing with Sequence.

Low Voltage Switchgear Standards and Testing:

Switchgear Standards and testing sequence includes the following important tests,

Switchgear Making and Breaking Switching Capacity Test:

Switchgear needs to pass the making and breaking switching capacity test. This test usually shows that this device is suitable for any extreme overload conditions of resistive, inductive or highly inductive loads during operation. The current overload ratings and the categories of duty have been shown in image. This type of test is performed by operating a selected device a number of times with its assigned rating.

Switchgear current overload ratings and categories of duty.
Switchgear current overload ratings and categories of duty.

Switchgear Temperature Rises Testing:

This test always performed with the highest current rating of the device. By this test it proves that under full-load conditions in service the device will not damage cables. It also includes the terminals and insulating materials or keeps operators at risk through contact with hot accessible parts. Because you really don’t want to operate any circuit breaker which is really hot (Body) during operation time. For this reason the limits of acceptable temperature rise are stipulated in the standard. If the switchgear surrounding temperature is high then some additional problem can come out.

Related: Circuit Breaker Operation Principle

Switchgear Operational Performance Test:

This operational performance test conducted to prove that, switchgear is mechanical and electrical durability during operation. Generally a number of on-load and off-load switching operations are made. It depends on the making and breaking operation duty assigned by the switchgear manufacturer.

Dielectric Verification Test:

This dielectric verification test proves that the device will complete operation sequence without damaging its insulation system. By this test a fuse switch is also proved by a fuse-protected short-circuit withstand (Breaking). For this test, the tested fuselinks use to have the maximum rating and with a breaking capacity that assigned by the fuselink manufacturer. No damage like welding of the contacts must occur to the switch as a result of this test. Disconnector has to provide isolation properties and additional types of tests are performed to prove these property.

Leakage current test is conducted after the main test sequence. Where the maximum levels of acceptable leakage current are specified. May be you already know that, the isolator handle need three times more force than the normal operation force (On). And it is necessary to switch off the device. To perform this test, contacts of one phase being artificially locked in the off position. Then test force is applied to open the switch. During and after this test, the on–off indicators of the disconnector must not give a false indication.

Related: Introduction of Switchgear

But for routine test is applied to all switch devices include an operational check. In this test each device will operated five times to check its mechanical integrity. In the mean time a dielectric test is carried out at a voltage which depends upon the rated voltage of the device that provided by the device manufacturer. Rated operating voltage for low voltage switchgear (380/415 V), the dielectric test voltage is 2500V.

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