Once the test plug is connected, the protection relay is prepared for injection tests, which will not affect at all to the rest of the system, from which it has been safely isolated Field elements will be automatically isolated short-circuiting current circuits and opening voltage and digital circuits.
The rugged FTP test plug includes a mechanism to guide and facilitate the insertion on the test block ensuring the opening of all contacts at the same time, and the insertion in the correct position. Once the test plug is inserted, it is possible to block it mechanically so that not involuntary extraction could be done.
The test plug includes 28 sockets which allow the use of safe banana plugs. 14 sockets are for injection test on the protection relay, and 14 for accessing to live side. Protection side and live side are clearly marked on the test plug. Each socket on the test plug is identified by a number which coresponds to the same numbered terminal of the test block to which the socket is connected when the test plug is inserted.
When the test plug is removed, a retention system will oblige to make this removal in the following sequence:
- Connection of voltage & current circuits.
- Opening the short circuit of the CTs.
- Connection of tripping circuits.
Before proceeding to the second step, it is necessary to act on the retention system of the test plug. This operation will give the necessary time for the values of current and voltage to stabilize after energizing transients, avoiding thus unwanted tripping due to these transients. During insertion and removal operation there will be no bounces which can cause interruption of the CT circuit.