ELCB
ELCB
(OP)
There are two ELCBs(4 pole)instaled in a distribution board.
One is on the main supply (60 A,200ma) and other one for a perticular device (30 A,300ma).The tripping time of both is same 0.1s.But for a lighting time secondary was tripped but not main.After that I manually shorted the neutral and earth of the device on that time both ELCB tripped simultaniously.So I am unable to find the reson for this problem.Can anyone help me?
One is on the main supply (60 A,200ma) and other one for a perticular device (30 A,300ma).The tripping time of both is same 0.1s.But for a lighting time secondary was tripped but not main.After that I manually shorted the neutral and earth of the device on that time both ELCB tripped simultaniously.So I am unable to find the reson for this problem.Can anyone help me?






RE: ELCB
I would suggest that the main incomer be changed to 60A 200/300ma ,100msec. The extra delay should allow any down stream faults to be cleared in time.
RE: ELCB
Tip : The main ELCB shuold always have current sensitivity higher than those of outgiong ELCBs, because the phase to ground leakages which no matter how small, are always there and their cumulative effect causes the main ELCB to trip on earth faults at outgoing circuits. Therefore the current sensitivity of main ELCBs is always kept higher as compared to outgoing ones.
RE: ELCB
RE: ELCB
RE: ELCB
All the previous respondents have fallen into the common trap of assuming that if the upstream ELCB has a higher current setting (300mA v 200mA) it will provide discrimination, but as noted above if the fault current is higher than those settings, as most faults are of course, both ELCBs will see the fault and trip - the fault current is not limited by the relay setting but by the impedance of the circuit. The ONLY way to provide discrimination with sensitive earth-fault relays (RCDs ELCBs call them what you will!) is to use time discrimination. About 300msec should be enough with most modern devices. So don't change the ELCBs just adjust the time delays.
RE: ELCB
In the first case Secondary ELCB tripped due the lightning strike.When manually shorted bothe tripped.In the second case even though both tripped simutaneously is there any possibility to one tripped earlier.
RE: ELCB
The ELCBs/RCDs are meant for protection against electrocution or fire due to leakage of current (caused by poor insulation etc.) and this explains why the operation of these devices shall be fast.
The ELCBs with current sensitivity of 30mA provide best protection against electrocution and are specified in individual outgoing circuits with limited amount of wiring downstream of ELCB to prevent spurious operation). Whereas, the ELCBs with sensitivity of 100, 300 or 500mA can be employed, as appropriate, in the incomer circuits and can provide effective protection against fire.
The current sensitivity to be selected is primarily decided by the amount of wiring downstream of the ELCB and the need to prevent spurious operation due to normal capacitive leakage currents to earth through the insulation.