Load Break Switches

Switches can be divided into three main groups, namely:
· Load break switch
· Ring main unit 
· Switch fuse combination

A medium voltage load break switch can de-energise circuits under normal operating conditions. It should be capable of making and breaking normal load currents, such as cable charging currents and transformer no-load currents. Next to that the load break switch  must be able to perform making operations under short-circuit conditions, since this is a possible operation condition when energising a medium voltage circuit under short-circuit conditions.

The IEC 60265-1 and ANSI C37.74 are the applicable standards for testing medium voltage load break switches.
When the load break switch is a part of a ring main unit the short circuit tests should be performed according the IEC 60265-1, IEC 62271-200 and standards that are applicable to other components that are a part of the ring main unit.

For load switches, switch-disconnectors, general-purpose switches, and back-to-back capacitor bank switches, the IEC 60265-1 is an often applicable standard. These switching devices are capable of making, carrying and breaking currents under normal circuit conditions, which may include specified operating overload conditions. They must also be able to carry currents under specified abnormal circuit conditions, and be able to close on and withstand short circuit currents.

Additional tests that should be performed on the last group, the switch fuse combination, are mentioned in the IEC 62271-105.
At the DNV KEMA High-Power Laboratory tests on load break switches are performed with the highest accuracy and under well-defined conditions in accordance with the standards requirements.
Furthermore, for obtaining a DNV KEMA Type Test Cerficate the more tests need to be performed by the DNV KEMA High-Voltage Laboratory, such as:
· Dielectric tests
· Temperature-rise test

More information? Contact us.