Testing and inspection of Relays

 

The application of the Relays in today’s Technological era is extensively vast and are the core part of any Electrical or Electronic protection system. As we know, Relays are used for the protection purposes, Relays isolate the faulty element/or faulty block (which might suffer from any abnormal condition) from the system.  Some Relays are manufactured for High Voltage or High Current applications directly and for Voltage and Current ratings which are beyond from the boundary, Instrument Transformers are used for such kind of applications, Instrument transformer sense the normal and abnormal condition, both the conditions sensed are fed directly from the secondary side of the instrument transformer to the Relay to compare with the reference value, if the sensed value is within the permissible limits it will act nothing but if there is any faulty condition relay will break the link between source and the load directly by itself or else by the help of attached Circuit Breaker which is linked with the Relay.

So, for normal and precise operation of Relay it is required to maintain the accurate working of the Relay. Otherwise its risky to rely the protective system which itself is faulty, so the Relay should be tested once before installing if it is working precisely or not, and after every two years after installing, according to the NFPA 70B 2016 the relay is required to be tested completely. Below some are the techniques to test the relays.

Physical Inspection:

In this particular method the Relays are inspected generally by their physical appearance, by observing their Electro-Mechanical working, if the plunger system is working correctly or not if the relay is  Electro-Mechanical, and if the Relay is Solid state then its hard to observe physically, further test must be performed for more inspection.

Electrical Parameters Inspection:

In this method, rated coil voltages are applied firstly to the Relay, then the conductivity of the contacts is inspected, also in the High Voltage and High Current Relays the arcing is monitored while the contacts are made and break, so the Di-Electric strength between the contacts can be tested. Artificially abnormal conditions are applied to Relays to monitor the behavior so that it could be inspected properly.

Mechanical Strength Inspection:

Mechanical strength of the Relays is inspected to withstand in industrial application or in high temperature environment is also inspected in the routine inspection.

Solid State Relays Inspection:

Solid state Relays are used where very fast switching is required, these relays are fast in response, since these Relays does not have any moving part within themselves so there is not any Electro-Mechanical tests are required to perform, these Relays are inspected for their switching time, leakage current inspection, their thermal behavior when full rated load current is passing through them.