RESIDUAL CURRENT DEVICE (RCD)

Definition – It’s a device which continuously monitors the current & interrupts the circuit if current flows in wrong path like earth etc. It’s a live saving device which is used mostly in residents. It provides very high level of protection which protects a person from electric shock.

(Note:-RCCB is one of the RCD equipment.)

COMPARISION BWTWEEN MCB, ELCB, RCCB, RCBO & RCD

 

Type of protection MCB ELCB RCCB RCBO RCD
Over-current yes no no yes no
Short Circuit yes no no yes no
Earth Fault no yes yes yes yes

Note30mAELCB/RCCB/RCDs are used for personal protection against electric shock because more than 30mA leakage current is harmful (as per NBC-2016 for residential, school & Hospitals) .

100mA ELCB/RCCB/RCDsare used where there are some standing leakage current in electronic devices (as per NBC for other buildings except residential, school & Hospitals). This is the value of current which falls between 30mA & 300mA.

300mA ELCB/RCCB/RCDs are used in order to protect form fire as leakage current more than 300mA may cause fire accidents if faulty circuit is not isolated from the circuit. Also such

— In modern installations, a certain amount of current flowsto earth. This leakage current is known as Standing Leakage Current. The source of such leakage current is RFI filters & surge suppressers fitted in electronic devices like computers, fridges etc. This leakage current is considered to be maximum 2mA for per 10A load. Hence for 100A load, leakage current would be 20mA. Therefore, No. of computers on each earth leakage protection device should be selected carefully so that leakage current should not disturb the operations.