Earth Leakage Circuit Breaker
An Earth Leakage Circuit Breaker (ELCB) (now referred to as residual current circuit breaker) is a safety device used in electrical installations with high earth impedance to prevent shock. History
ELCBs were mainly used on TT earthing systems. Nowadays, ELCBs have been mostly replaced by residual-current devices (RCDs). However many ELCBs are still in use.
Early ELCBs responded to sine wave fault currents, but not to rectified fault current. Over time, filtering against nuisance trips has also improved. Early ELCBs thus offer a little less safety and higher risk of nuisance trip. The ability to distinguish between a fault condition and non-risk conditions is called discrimination.
ELCB manufacturers include: Legrand, Havells, ABB, Siemens AG, Areva T&D, Camsco, Telemecanique, Orion Italia, Crabtree, MEM.
[edit] Types
There are two types of ELCB: • voltage operated and, • current operated.
[edit] Voltage-operated
Voltage-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 but are no longer installed in new construction. A voltage-operated ELCB detects a rise in potential between the protected interconnected metalwork (equipment frames, conduits, enclosures) and a distant isolated earth reference electrode. They operate at a detected potential of around 50 volts to open a main breaker and isolate the supply from the protected premises. [2]
A voltage-operated ELCB has a second terminal for connecting to the remote reference earth connection.
The earth circuit is modified when an ELCB is used; the connection to the earth rod is passed through the ELCB by connecting to its two earth terminals. One terminal goes to the installation earth CPC (circuit [[Power system protection |protective]] conductor, aka earth wire), and the other to the earth rod (or
ELCBs were mainly used on TT earthing systems. Nowadays, ELCBs have been mostly replaced by residual-current devices (RCDs). However many ELCBs are still in use.
Early ELCBs responded to sine wave fault currents, but not to rectified fault current. Over time, filtering against nuisance trips has also improved. Early ELCBs thus offer a little less safety and higher risk of nuisance trip. The ability to distinguish between a fault condition and non-risk conditions is called discrimination.
ELCB manufacturers include: Legrand, Havells, ABB, Siemens AG, Areva T&D, Camsco, Telemecanique, Orion Italia, Crabtree, MEM.
[edit] Types
There are two types of ELCB: • voltage operated and, • current operated.
[edit] Voltage-operated
Voltage-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 but are no longer installed in new construction. A voltage-operated ELCB detects a rise in potential between the protected interconnected metalwork (equipment frames, conduits, enclosures) and a distant isolated earth reference electrode. They operate at a detected potential of around 50 volts to open a main breaker and isolate the supply from the protected premises. [2]
A voltage-operated ELCB has a second terminal for connecting to the remote reference earth connection.
The earth circuit is modified when an ELCB is used; the connection to the earth rod is passed through the ELCB by connecting to its two earth terminals. One terminal goes to the installation earth CPC (circuit [[Power system protection |protective]] conductor, aka earth wire), and the other to the earth rod (or