It is for protecting power distribution system, earth leakage devices are only for protecting people from electrocution. An overload circuit breaker is designed to interrupt a circuit when the current exceeds a preset limit. In a thermal type breaker, a small over-current (due to overloading) can be tolerated for a prolonged period before tripping, although a large over-current (due to a short circuit) will trip fairly quickly. A magnetic type breaker will trip very quickly once its threshold current has been reached. As the current necessary for fatal electrocution is less than a couple of Amp. for a duration of less than a couple of seconds, an overload breaker offers virtually no protection from electrocution. Earth leakage protection devices are designed to trip for fault currents between 10 ~ 100 mA and for interrupt times between 40 and 100 milliseconds after a fault current is sensed.
Earth leakage devices are based on the principle that the amount of current entering a device should be exactly the same as the amount of current leaving the device and that any discrepancy is due to current flowing somewhere that it shouldn't, which is a bad thing. If an electrical appliance such as a luminaire is working properly all electrons entering the luminaire will flow in down the active wire, around through the filament of the lamp and out again down the neutral wire. If there is a fault in the wiring which somehow allows the body of the appliance to become connected to the active line, then when someone touches the appliance, by being elecrocuted they provide a path to earth for the current which is not via the neutral; this is the situation for which an earth leakage protection device is employed. An overload circuit breaker will not care that a small, albeit fatal, additional current is now flowing.
In a protection device an earth leakage current is sensed by comparing the active and neutral currents flowing through a circuit, usually by the simple means of measuring the current induced in a coil through which both of the wires have been passed. Under normal conditions, as there are identical currents in both wires and the currents will be flowing in opposite directions, there will be no current induced in the coil. The current induced in the coil by a fault condition can be used to trigger an interruption to the circuit.
You may meet them as RCDs (Residual Current Devices), ELCBs (Earth Leakage Circuit-Breakers), CBRs (Core Balance Relays) or GFIs (Ground Fault Interrupts) but whatever your background and whichever TLA (Three Letter Abbreviation) you use, earth leakage devices are not only a crucial component in your electrical safety scheme, they are frequently also required by regulation. Let's look at what they do, how they do it and how we can use them to improve safety without causing too many unnecessary disruptions to what we do.
How to avoid a major production catastrophe? To place each device in your electrical system on its own rather costly earth leakage protected circuit ensuring that only the faulty device will be disconnected. A more cost-effective alternative may be to place devices with known leakage on to a circuit which has an earth leakage protection device with higher activation threshold or one designed specifically to work with the ballasts of discharge light sources. Some devices may actually be so reduced in operational effectiveness that they are better installed on circuits not fitted with an earth leakage device. These variations are often only possible in fixed installations and must always be done in consultation with an electrician or electrical engineer who is fully cognisant with the safety and operational requirements of the situation.
Earth leakage protection is an important part of the electrical safety scheme for any system, although it may present some implementation difficulties where there are conflicts between the safety ideal and the operational reality. It is vital for us to make certain that the system that we are using is configured to meet the best possible.
ELCB stands for core balance Earth Leakage Circuit Breaker and this device will break the electrical circuit as soon as it detects any significant leakage. Once you have installed the ELCB into the wiring system of your aquarium, it will continually monitor the current in both the active and neutral wires in search of leakage. When it detects a large enough current loss, the whole circuit will be cut off instantly, thus preventing electrical accidents from happening. Since different appliances have different natural current losses, the cut of level for ELCB:s normally varies from 10 milliamps to 30 milliamps. 30 milliamps is considered a good level for aquarium use.
Without an ELCB, a normal household switchboard with standard circuit breakers will normally not cut off the circuit when a low magnitude leakage to earth occurs. The problem is of course that even a low magnitude leakage can cause serious injury to humans. When you hock up your aquarium equipment to a 240 volts outlet, a current of no more than 50 milliamps can be fatal, and no more than 10 milliamps is needed to give the aquarists a serious, agonizing electrical shock.
Installing an ELCB is rather expensive and it is naturally tempting to spend the money on more appealing aquarium thingamajigs. Setting some money aside to safeguarding yourself, your family, your pets, and that kind neighbor who volunteered to care for your fish during your vacation, from electrical accidents is however the best course of action in the long run. Even a fairly insignificant electrical accident is a really agonizing experience that no one should have to go through.
Portable ELCB:s are self-contained units that you simply plug into the standard socket before you plug in your aquarium equipment. It is normally a bit more expensive than the wall mounted ELCB, but you can on the other hand plug it in yourself without having to hire an electrician. You can also bring it along when you move to a new address or move your aquariums to a new room in your house.
The wall mounted ELCB A wall mounted unit is normally less expensive than a portable ELCB, but you might on the other hand have to hire an electrician to do the installation for you. If you feel confident to do it yourself, you should still check with local authorities and your insurance company before you give it a try. In many parts of the world, this type of installation can only be done by qualified personal, and your insurance company might also deny you compensation if an accident occurs in something that you installed yourself.ELCB for the entire house
If you are willing to hire a qualified electrician, you can have an ELCB wired into the main switchboard of your home, thereby securing protection for all the power points in your house or apartment – not only the one you use for your aquarium. This is a bit more expensive than the two other alternatives, but you will on the other hand make every inch of your home where water and electricity is mixed much safer, e.g. the kitchen, the bathroom, the garden and so on.