Testing of Earth Leakage relay

           Testing of Relay is very important to check the healthiness of relay as well as it's circuit.In ELR testing whole circuit being checked. Common standard used in ELR is IEC-62020 and IEC-60755. It has Sequence of operation which is as follows,

1. CBCT Sense Leakage current and it send to ELR.

2. ELR has Current and time setting so if Leakage current is greater than its setting then it's contacts will changeover and ELR give trip indcation.

3. As ELR give trip indication it will trip MCCB or open contactors.

           CBCT sense zero sequence current so it's called zero sequence current detector, We simply pass one wire through CBCT and flow single phase current. as current reach it' s setting limit ELR tripped and it will trip MCCB. Sometime it happen that ELR not operate at its set point but above it's set point, so if difference is high then your CBCT has error. Require replacement with new CBCT.

For better performance you need to mount same CBCT which is came with relay, because different maufacturers are has it's own ratio of CBCT.

               CBCT always installed at incoming side cable so you can protect the whole circuit to load. both red wires is for relay input and other 2 wires for test signal output.

     Whole circuit diagram of ELR and CBCT.

               In monsoon season IR of cable to earth become low due to moisture in air so at that time leakage current will be more so it happens that your ELR malfunction and trip your MCCB so set your set leakage current wisely.