Guest guest Posted February 25, 2008 Report Share Posted February 25, 2008 ELCB = Earth Leakage Circuit Breaker. There are two types of ELCB, the voltage operated device and the differential current operated device. For the convenience of this article only (and at the risk of causing even more confusion) I will refer to these as vELCB and iELCB. vELCBs were first introduced about sixty years ago and iELCBs were first introduced about forty years ago. To the top The principle of operation of the vELCB is as follows. Under normal conditions the closed contacts of the vELCB feed the supply current to the load. The load is protected by a metal frame, such as in an electric cooker. The vELCB also has a relay coil, one end of which is connected to the metal frame and one end connected directly to ground. A shock risk will arise if a breakdown in the insulation occurs in the load which causes the metal frame to rise to a voltage above earth. A resultant current will flow from the metalwork through the relay coil to earth and when the frame voltage reaches a dangerous level, e.g. 50 volts, the current flowing through the relay coil will be sufficient to activate the relay thereby causing opening of the supply contacts and removal of the shock risk. As can be seen from the above description, this type of ELCB is essentially a voltage sensing device intended to detect dangerous touch voltages. The level of shock protection provided by the vELCB was somewhat limited as these devices would not provide shock protection in the event of direct contact with a live part. An additional problem with the vELCB was its tendency to be tripped by earth currents originating in other installations. To the top The iELCB was introduced in the late 1950's. It operates on the following principle. Under normal conditions the closed contacts of the iELCB feed the supply current to the load. The load conductors are passed through a current transformer (CT), a doughnut shaped device. The load conductors act as primary windings of the transformer. The CT is fitted with a secondary winding. Under normal conditions, the total current flowing from the supply to the load will be the same as the total current flowing back to the supply from the load. As the current in both directions is equal but opposite, it has no effect on the CT. However, if some current flows to earth after the iELCB, possibly due to an earth fault, the current flowing to the load and from the load will be different. This differential current will cause a resultant output from the CT. This output is detected and if above a predetermined safe level, it will cause the iELCB to trip and disconnect the supply from the load. To the top For 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. However, the use of a common name for two different devices gave rise to considerable confusion in the electrical industry. If the wrong type was used on an installation, the level of protection given could be substantially less than that intended. To remove this confusion, IEC decided to apply the term Residual Current Device (RCD) to differential current operated ELCBs. Residual current refers to any current over and above the load current. The RCD is now the preferred means of providing shock protection, and the term RCD has largely replaced ELCB within the industry. Unfortunately, the RCD industry has had considerable difficulty in shaking off the old association with ELCBs, and many electrical contractors still ask for an ELCB when in fact they want an RCD. Hopefully this article will remove some of the confusion. To the top RCD = Residual Current Device. This is a generic term for the entire range of RCDs. Sunil Katare wrote: Dear Team members, Pl. help me out by clearifying the importance & difference between ELCB & RCCB in electrical safetry. Can any body give me details about safe electrical connections for, DG Set - 15kva Welding Machine etc. Looking for last minute shopping deals? Find them fast with Yahoo! Search. Now you can chat without downloading messenger. Click here to know how. Quote Link to comment Share on other sites More sharing options...
Guest guest Posted February 25, 2008 Report Share Posted February 25, 2008 Dear Sunil, ELCB & RCCB are same. ELCB means Earth leakage Circuit Breaker & RCCB means Residual Current Circuit breaker. For DG set & Welding machine you must ensure Main Control switches with Fuses of required capacity. Provision for locking switches in OFF position for LOTO. Power Indication LED lamps Ammeter, Voltmeter, Frequency Meter for DG set. Two separate & distinct earth connections for Metal frames of all Electrical equipment. Neutral Earthing for Gen set with provision for Watering & Resistance measurement. Regards, ------------------------------------------------------------------------------------------------------------------------------------------------------------- BS Gopala Krishna Manager- HSE, Management Representative- ISO 14001,OHSAS18001 Tel 080 22192638 Mobile 9342161817 E mail b.gopalakrishna@... From: indiansafetyprofessionals [mailto:indiansafetyprofessionals ] On Behalf Of Sunil Katare Sent: Monday, February 25, 2008 9:57 PM To: indiansafetyprofessionals Subject: Elecrtical Safety Dear Team members, Pl. help me out by clearifying the importance & difference between ELCB & RCCB in electrical safetry. Can any body give me details about safe electrical connections for, DG Set - 15kva Welding Machine etc. Looking for last minute shopping deals? Find them fast with Yahoo! Search. Quote Link to comment Share on other sites More sharing options...
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