The P991 test block, designed within all the protection ranges, offers safe and preconfigured facilities for monitoring and secondary injection testing in any power system protection scheme when used with the P992 multi-finger test plug.

The P991 test block features visible automatic line CT shorting prior to the relay CT circuit being broken on insertion of a P992 multi-finger test plug. Up to three stages of sequential contact operation are provided by the P991 test plug. To avoid accidental tripping an extraction stop facility is included. The P991 test block carries 14 circuits. Each circuit is brought out to separate pairs of 4mm screw terminations at the rear of the test block