Earth Tester
2008
 |
 KIKUSUI TOS6200 TOS 6200 Earth Continuity Tester CLASS1 $997.00 Time Remaining: 2d 11h 5m Buy It Now for only: $997.00 |
Earth Tester
Electrical Earth - Why Do We Need It? By Dave J Fletcher
Why do we have an earth in our houses? To answer that requires a little explanation of how electricity reaches our homes and how fuses work.
Electricity is generated at power stations or similar installations,
wind farms, hydro-electric turbines etc. These plants generate the electricity which is the transformed up to around four hundred thousand volts and distributed around the country via the national grid.
It is easy and cost effective to transport electricity at these incredibly high voltages but obviously it once again has to be transformed back down to 230 volts for use in the house.
At the transformer the centre of the winding is connected via rods or mats, to the earth. This earthing of the winding provides a reference point, nominally zero volts. Electricity is then supplied at 230 volts to this reference.
To be useful electricity requires a circuit. The electricity must flow from a source, through the device whatever it may be, kettle, iron cooker etc. and return to that source.
To protect the cable in which it flows the amount of electricity must not exceed the capability of the cable. This would be an overload in the long term, in the short term a fault in the cable or any device attached to it will cause a large amount of electricity to flow and it is this that blows the fuse.
The amount of electricity needed to blow a fuse is determined by the rating of the fuse itself, i.e. a current of around 1.6 times the fuse rating is required to operate a re-wirable fuse so a 20A fuse will need approximately 32 amps.
To facilitate the quick and efficient operation of the fuse the electrical earth provides a quick route back to the source, that is the transformer. The better the return path, the more electricity flows and the quicker the fuse operates.
The circuit that the live conductor and the earthing conductor form is called the earth loop. The earth loop is measured with a special tester and must conform to certain constraints for the variety of fuses available.
The requirements for each type of fuse, properly called a protective device, are laid down in the wiring regulations. The electrical earth therefore, is extremely important for the safety of any user of electrical system. The absence of the earthing conductor means that any fault on the system will not operate the fuse until you or one of your family becomes that missing part.
Dave Fletcher is a qualified electrician in the UK. Home-owners and diyers-find Cordless Drills including the fantastic Milwaukee Cordless Drill on my site.
About the Author
Weird light fixture problem. Have I killed my kitchen lights?
Hi!
I have changed our living room light fixture to a pendant style one. When I removed the old fixture I noticed there is an extra black wire there (the wires are the UK old style red/black). So I had one live red, one live black, one Neutral black and one earth. By mistake I connected two live wires into the light fixture. When the lights didn't work It took me a couple of minutes to figure it out but eventually I removed the live-black and put in the neutral-black wire. The live black is now tucked in there somewhere (clipped for safety of course). Light works, great!
However, I then annoyingly note that the light fixture in the kitchen stopped working. Using a tester screwdriver I note that the bulb socket does have power through them, but none of the lights work. When I put in a new light bulb which I know is good, still nothing....
What have I done??? How come I have power (via the tester) and no light?
Thanks!
Harel
The extra black wire was to the kitchen lite...put it back the way it was.
Motwane's Digital Earth Tester DECT-3
