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ACTIVE LERNING MATERIAL SUBJECT: EEE SUBJECT CODE : 2110005 MADE BY- DIVYA PARMAR(13EEEG117) BHARGAVI VYAS(13BEEEG133) SHIVANGNI PARMAR(13BEEEG102) GUIDE BY- MRS.SHITAL PUJARA. ELEMENTS OF ELECTRICAL ENGINEERING. EARTH LEAKAGE CIRCUIT BREAKER(ELCB).
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ACTIVE LERNING MATERIALSUBJECT: EEESUBJECT CODE : 2110005 MADE BY- DIVYA PARMAR(13EEEG117)BHARGAVI VYAS(13BEEEG133)SHIVANGNI PARMAR(13BEEEG102) GUIDE BY-MRS.SHITAL PUJARA
Definition • Device designed to open the circuit automatically under abnormal conditions without damage to itself when properly applied within its rating.
Circuit breakers are categorized by the method employed to interrupt the circuit current (extinguishing the arc) when the current contacts open.
INTRODUCTION An Earth Leakage Circuit Breaker(ELCB) is a safety device used in electrical installations with high earth impedance to prevent shock. It detects small stray voltages on the metal enclosures of electrical equipment, and interrupts the circuit if a dangerous voltage is detected. Once widely used, more recent installations instead use residual current circuit breakers which instead detect leakage current directly.
PURPOSE The main purpose of earth leakage protecters is to prevent injury to humans and animals due to electric shock.
WORKING The ELCB consists of an operating coil and a trip mechanism which in turn trips the supply to the circuit. It will operate if a live terminal or conductor is touched by an earthed object or person provided the leakage current exceeds the rated operating current of ELCB. The phase and neutral wires of the circuit being protected , are led through one winding of a transformer. A second winding controls the tripping mechanism. Under normal Conditions, when there is no leakage current the tripping mechanism is not energized and contacts are kept closed using a spring mechanism.
When the earth leakage occurs from either the phase or the neutral side of the circuit, the currents are unbalanced by amount equal to the leakage current reaches the rated tripping current of the ELCB, the tripping mechanism will operate opening the ELCB contacts. A test button is included in the ELCB for testing its trip mechanism. This test should be carried out periodically to ensure its satisfactory working. The ELCB can be reset manually after its operation. But it cannot be reset, as long as the leakage persists. The ELCB is provided near the main switch board to protect the whole of the residence installation from leakage in any circuit or appliance , by switching off the supply.
TYPES OF ELCB • There are two types of ELCB • Voltage Operated • Current Operated
VOLTAGE OPERATED ELCBVoltage-operated ELCBs were introduced in the early 20th century, and provided a major advance in safety for mains electrical supplies with inadequate earth impedance. V-ELCBs have been in widespread use since then, and many are still in operation.
CURRENT OPERATED ELCB Current-operated ELCBs are generally known today as RCDs(residual current device). These also protect against earth leakage, though the details and method of operation are different . When the term ELCB is used it usually means a voltage-operated device. Similar devices that are current operated are called residual-current devices.
ADVANTAGES ELCBs have one advantage over RCDs: they are less sensitive to fault conditions, and therefore have fewer nuisance trips. (This does not mean they always do, as practical performance depends on installation details and the discrimination enhancing filtering in the ELCB.) Therefore by electrically separating cable armour from the cable circuit protective conductor, an ELCB can be arranged to protect against cable damage only, and not trip on faults in downline installations.
DISADVANTAGES • ELCBs introduce additional resistance and an additional point of failure into the earthing system. • As with RCDs, electrically leaky appliances such as some water heater, washing machines and cookers may cause the ELCB to trip. • They do not allow a single building system to be easily split into multiple sections with independent fault protection, because earthing system are usually bonded to pipe works.
