Earth Leakage
Earth Leakage
(OP)
Could you explain the operation of a domestic earth leakage unit. Can lights be connect to earth leakage? Will you get nuisance tripping when a light bulb pops?
Thanks
Thanks
When was the last time you drove down the highway without seeing a commercial truck hauling goods?
Download nowINTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS Come Join Us!Are you an
Engineering professional? Join Eng-Tips Forums!
*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail. Posting GuidelinesJobs |
|
RE: Earth Leakage
RE: Earth Leakage
The operation of Domestic Earth leakage is somethig like this.
It is done basically by a device called RCCB ( Residual current circuit Breaker). It basically detects the leakage of current interms of milliamps. Standard is 30mA, 100mA and 300mA. Note that 30mA is more sensitive than other.
It basically has a current transformer sensing the phase and neutral side. Normally operation ( No fault), the summation of current flow through neutral is zero and when there is a leakage, it sense the current through the current transformer and opens the breaker thereby isolating the supply and load side
Hope this helps
soma(Electrical)
G.P.A.Eswaran
Project Engineer
QuEST-GE GEDC
e-mail: arthanarieswaran.g.p@quest-global.com
RE: Earth Leakage
But do notconnect devices like fridges to circuits protected this way unless it is required by standards.
You may find a lot of rotten food at home after nuisance tripping when you come back from a holiday.
If you also want to protect these devices use a separate RCCB device for these circuits.
RE: Earth Leakage
In the Uk we do not connect to lighting circuits, more from a point of safety.
Nusiance tripping can occur due to transients etc. it depends on the manufacturing standard. Most modern RCD's incorporate filter circuits to limit this problem. Light bulbs blowing do produce transients that can cause tripping.
RE: Earth Leakage
The long answer is:
1. I made the mistake of wiring a fluorescent fixture in my kitchen to a GFI outlet. Flipping the switch on will trip the outlet once in a while. It never trips after it has started, only instantaneously with starting. This happens only about once every month or two, not every day. I cannot explain why the starting current would not be equal on the phase and neutral, but apparently there is some small difference there about equal to the trip level of the receptacle.
2. Every device has some small associated ground leakage current. Every device you add to a GFI circuit will add to the total ground leakage seen by that circuit. It does not take too many downstream devices leaking at maybe 3 to 10mA to add up to 30mA, and start causing a bunch of nuisance tripping. This effect is exacerbated in areas where water can condense, such as cold rooms, bathrooms and outdoors (generally, most of the places where you are required to provide GFI).
RE: Earth Leakage
If there is a fault between active and earth in the house, some current returns in the earth wire and so reduces the current in the neutral wire, so causing an imbalance in the core balance CT - and hey presto, the protective device trips.
Bung
RE: Earth Leakage
Standard UK practice is to limit the earth leakage on any circuit to 25% of the nominal rating of the RCD. Typical IT equipment can produce as much as 3.5mA of earth leakage, so where you may have a PC and screen and UPS it is possible in theory to have as much as 10.5mA of earth leakage.
Where earth leakage on any circuit may in operation exceed 10mA we also have to take additional steps for safety in teh form of running an additional earth wire etc.