OSM Recloser Interface Test Set

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The implementation of testing procedures is an integral aspect of both the switchgear manufacturing and servicing processes. Possessing the ability to conduct testing both in house and on the field ensures the safety, lifespan and rated operation of switchgear devices.

Due to the large range of primary fault currents (up to 16000A), relays are generally tested using secondary injection, whereby the relays are subjected to the same currents they would normally receive from the secondary of a CT. However, unlike general protection relays, the OSM recloser does not provide discrete inputs for CT connections, making it difficult to introduce a secondary signal to the MPM. Furthermore, the recloser utilises Rogowski sensors within the cubicle instead of CT's, which output a voltage signal proportional to the input current. This does not allow for a current signal to be injected into the MPM.

NOJA Power Interface Test Set

To overcome this problem, NOJA Power provides an Test Set to simulate the current and voltage signals generated by sensors inside the OSM15 and OSM27 recloser bushing.
The Interface Test Set uses Rogowski transformers to convert an injected current signal into the voltage signal that the MPM is expecting. When used in conjunction with a power system and three phase test set it can be used to conduct the following tests:

• Three phase short circuit
• Phase to phase short circuit
• Earth fault
• Upstream broken wire
• Low source voltage
• Loss of supply

In addition to this functionality, this device has external voltage free contacts both normally open and normally closed that simulate the positioning of the contacts. The simulator also allows coil faults to be actioned and include; Mechanical Trip / Manual Trip, Simulator Coil Short Circuit, Simulator Coil Open Circuit.

The Interface Test Set allows for either the OSM or Simulator to be selected for coil operation from the MPM. This offers several advantages during application. As the MPM provides directional protection using voltage as a reference to determine current directions, the Interface Test Set provides an interface so that LV can be applied that the MPM will interpret as MV to allow for directional testing. This also provides the means to test UV1, Uv2 and UV3 based protection.