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  • Fail-safe sequential disconnection of current, voltage and trip circuits when the test-plug handle is inserted.
  • Latching feature when the test-plug handle is withdrawn allowing the relay to stabilize with service values before the trip circuits are restored. This prevents inadvertent tripping.
  • Complete isolation of secondary instrument transformer circuits.
  • Trip-block plug which isolates a trip circuit without interrupting other circuits, allowing the trip output to be monitored, and also provides visual indication of an isolated trip circuit.
  • Block-plug handle which disconnects all circuits routed through the test switch.
  • Ammeter test-plug with local automatic short-circuiting device in case of inadvertent opening of a CT circuit.
  • Auxiliary station power supply made available for test equipment.
  • Extension bases which facilitate measurement and adjustment of plug-in module circuits.


The COMBITEST system for testing of protection relays is built up around the RTXP 8, RTXP 18 or RTXP 24 test switches. The test switch can also be used for other testing needs not directly associated with relays, such as for switchboards or voltmeters. The test switch may be used where testing would otherwise require disconnection of the instrument transformer’s secondary or control wiring. It may also be used to advantage in the testing of other complete relay systems, even when each individual relay has its own test switch. When the test-plug handle is inserted into the test switch, preparations for testing are automatically carried out in the proper sequence, i.e. blocking of tripping circuits, short-circuiting of CT’s, opening of voltage circuits, making relay terminals available for secondary injection. The test-plug handle may be connected to any type of test equipment or instrument. When a number of protection relays of the same type are tested, the test-plug handle need to be moved only from the test switch of one relay to the test switch of the other, without altering previously made connections. If different types of relays are to be tested, it is a simple matter to change the connections on the test-plug handle and the relay testing set.