Earth Leakage Circuit Breaker By 47 M B

Earth Leakage Circuit Breaker By: 47. M. B. J. Varma 48. Mallikarjuna Abhilash 49. Maraka Kulateja 50. Prajakta Mategadikar 51. Medepalli Nikhil Raj

Definition: An Earth Leakage Circuit Breaker (ELCB) is a device used to directly detect currents leaking to earth from an installation with high earth impedance to prevent shock.

HISTORY ØVoltage ELCBs were first introduced about sixty years ago and current ELCB was first introduced about forty years ago. ØFor many years, the voltage operated ELCB and the differential current operated ELCB were both referred to as ELCBs because it was a simpler name to remember. ØIEC decided to apply the term residual current device (RCD) to differential-current-operated ELCBs. ØResidual current refers to any current over and above the load current.

ELCB Manufacturers: Legrand Havells ABB (ASEA Brown Boveri) Crabtree Siemens AG Schneider Electric Vguard

Ø The main purpose of Earth leakage protectors is to prevent injury to humans and animals due to electric shock. Ø ELCBs were mainly used on TT earthing systems. TYPES OF ELCB: 1. Voltage ELCB 2. Current ELCB

Voltage ELCB: Ø One terminal of the relay coil is connected to the metal body of the equipment to be protected against earth leakage and other terminal is connected to the earth directly. Ø If any insulation failure occurs or live phase wire touches the metal body, of the equipment, there must be a voltage difference appears across the terminal of the coil connected to the equipment body and earth. Ø This voltage difference produces a current to flow the relay coil. Ø If the voltage difference crosses, a predetermined limit(gnerally 50 V), the current through the relay becomes sufficient to actuate the relay for tripping the associated circuit breaker to disconnect the power supply to the equipment

Voltage ELCB

Voltage ELCB Advantages: ü Less sensitive to faulty conditions. ü Nuisance tripping especially during thunder storms(When an installation has two connections to earth, a nearby high current lightning strike will cause a voltage gradient in the soil, presenting the ELCB sense coil with enough voltage to cause it to trip). ü If the installation’s earth rod is placed close to the earth rod of a neighboring building, a high earth leakage current in the other building can raise the local ground potential and cause a voltage difference across the two earths, again tripping the ELCB.

Voltage ELCB Disadvantages: § They do not allow a single building system to be easily split into multiple sections with independent fault protection, because earthing systems are usually use common earth Rod. • As electrically leaky appliances such as some water heaters, washing machines and cookers may cause the ELCB to trip. • They do not detect faults that don’t pass current through the CPC to the earth rod.

What is the use of TEST button on ELCB?

The test facility provided on the home ELCB will only confirm the health of the ELCB unit That test facility does not confirm that the ELCB will trip when an electric shock hazard does occur.

Current ELCB: Ø Current-operated ELCBs are generally known as Residual-current devices (RCD). Ø These also protect against earth leakage. Ø Both circuit conductors (supply and return) are run through a sensing coil; any imbalance of the currents means the magnetic field does not perfectly cancel. The device detects the imbalance and trips the contact. Ø When the term ELCB is used it usually means a voltage-operated device. Ø Similar devices that are current operated are called residualcurrent devices. Ø RCCB is more sensitive than ELCB.

Typical RCB circuit(Single Phase):

Current ELCB Working: Ø The polarity of the phase winding and neutral winding on the core is so chosen that, in normal condition mmf of one winding opposes that of another. Ø As it is assumed that, in normal operating conditions the current goes through the phase wire will be returned via neutral wire if there's no leakage in between. Ø As both currents are same, the resultant mmf produced by these two currents is also zero-ideally. Ø The relay coil is connected with another third winding wound on the CT core as secondary. The terminals of this winding are connected to a relay system.

Current ELCB Working: Ø In normal operating condition there would not be any current circulating in the third winding as here is no flux in the core due to equal phase and neutral current. Ø When any earth leakage occurs in the equipment, there may be part of phase current passes to the earth, through the leakage path instead of returning via mental wire. Ø Hence the magnitude of the neutral current passing through the RCCB is not equal to phase current passing through it.

Typical RCB circuit(Three Phase): This relay causes tripping of the associated circuit breaker to disconnect the power supply to the equipment under protection

v Residual current circuit breaker is sometimes also referred as residual current device (RCD) when we consider the device by disassociating the circuit breaker attached to RCCB. v The entire parts of RCCB except circuit breaker are referred as RCD. Sensitivity of RCB: Ø Medium sensitivity (MS): 100 - 300 - 500 - 1000 m. A (for fire protection) Ø Low sensitivity (LS): 3 - 10 - 30 A (typically for protection of machine)

Break time of RCB: Ø G (general use) for instantaneous RCDs (i. e. without a time delay) Minimum break time: immediate Maximum break time: 200 ms for 1 x IΔn Ø S (selective) or T (time delayed) for RCDs with a short time delay (typically used in circuits containing surge suppressors) Minimum break time: 130 ms for 1 x IΔn Maximum break time: 500 ms for 1 x IΔn

Shock Preventor No JOLT From VOLT

Electrical accidents Statistics Almost 12 people die due to electrocution every day(Source-NCRB) -42% of total fires occur due to electrical sources(Source-OISD) -8% deaths that occur in factories are due to electricity. -

üAt present to prevent electrical shock three wire system with protective multiple earthing is used. üInstallation of ELCB üELCB needs effective earth to trip the power else require a secondary path for current to unbalance in ELCB to operate and protect. üELCB should be tested once in a month for a better protection.

Earth Loop Voltage Detector: Ø Generally called as ELVD Ø An intelligent sensor in the ELVD senses and compares the voltage of the neutral and the earth terminals (Body) of the appliance. Ø If the voltage level or fault signal exceeds 75 V, a positive signal is sent to the circuit breaker to cut the power only to the faulty appliance. All other lights and electrical appliances in the home continue to function normally. Ø All that needs to be done to restore power to the appliance is to restart it after rectifying the fault in the appliance.

ØELVD is far more better than conventional circuit breakers which has delayed reaction presenting hazard. ØThe operating time of ELCB is <40 milliseconds where as of ELVD is <10 milliseconds Until the fault in the appliance has been fixed, the ELVD will not allow the device to be powered.