Full form of RCD – The full of RCD is Residual Current Device.

What is RCD – Definition of RCD is given below –

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

Note – 30mAELCB/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/RCDs are 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 flows to 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.

Frequently Asked Questions (FAQs) on RCD –

Q1) What does RCD stand for?

Ans) RCD stands for Residual Current Device?

Q2) What circuits should RCD be protected?

Ans) It is an electrical device used for protection of user from electrical shock   when current diverts its path such as earth leakage etc. which may be in equipment or circuit.

Q3) What is RCD circuit breaker?

Ans) The full form of RCD is Residual Current Device which is used for protection from earth leakage etc.

Q4) How to test RCD with multimeter?

Ans) RCD can’t be tested with multimeter because multimeter is used for wire continuity, AC / DC current measurement in wire & AC / DC voltage measurement etc.

Q5) What is RCD testing? Or How to test RCD tripping?

Ans) The RCD can be tested by a test knob provided in RCD itself. We can test it by pressing the test knob, if RCD is tripping by pressing test knob then it is OK/ healthy otherwise it is faulty.

Q6) Why does RCD trips?

Ans) RCD trips when there is imbalance current in the circuit due to earth fault etc.

Q7) Why is my RCD tripping?

Ans) Your RCD is tripping because of current imbalance which may be due to earth fault & other reasons.

Q8) What is RCD & MCB?

Ans) The function of both RCD & MCB is different. RCD provides protection on imbalance current in the circuit which may be due to earth fault while MCB provides protection against over current which may be due to overloading or short circuit.

Q9) What is the difference between MCB, ELCB, RCCB, RCBO & RCD.

Ans) The detail of each device is given in above section of this page.