Working with electricity is one of the most dangerous things.
The secret to working with electricity is to ONLY USE ONE HAND.
If you are feeling for wires or doing anything with one had, keep the other hand away from EVERYTHING.
Never lean-against or touch any metal cabinets when working. This applies to cool-room wiring etc.
Never work on any wiring when it is LIVE.
If you have to test circuits when they are LIVE, use equipment with good-quality test probes, leads and insulated test-gear.
This is the only time you are risking a shock as both hands are touching live connections.
Never take your eyes off your hands and never probe without watching the probe.
This all sounds like obvious, silly, statements, but you only have one life and a severe shock will put you off work for the rest of your life.
I have never had a "belt" in 50 years, and have been working ON and WITH live wiring and LIVE CIRCUITS for many years.
It's the one-hand secret that keeps you alive.
You may think body-resistance is 50k to 150k, but this is the resistance of your skin. When electricity burns through the skin, the internal resistance of your body is VERY LOW. That's why a very high current will flow and COOK YOU INSTANTLY.
The same with water.
PURE WATER has a very high resistance, but tap water has a few dissolved minerals and this reduces the resistance considerably.
If you touch something wet, the resistance at the point of contact is very low and the electrical shock (the current) will be multiplied 1,000 times. That's why electrocution in wet conditions is instantaneous.
EARTH LEAKAGE DETECTORS (ELD) are also called RESIDUAL CURRENT DETECTORS (RCD) or EARTH LEAKAGE CIRCUIT BREAKERS (ELCB) and they work on the principle of monitoring the current through the active wire and the neutral wire.
These two wires are wound on a transformer with one or two turns.
The neutral wire is connected "backwards" and when current flows, no field is produced. The two fields cancel each other. On the same transformer is a secondary winding of 1,000 turns.
If current just flows through the active or neural wire, a voltage is produced in the 1,000 turns and this is detected by an electronic circuit that trips a relay to turn the power OFF.
This happens in one or two cycles and the shock you get does not have time to cook your body.
It's lucky our supply is AC.
With AC you can feel a voltage as low as 80v but with DC you cannot feel up to 200v.
Originally the distribution-networks were designed by Edison and he chose 110v DC as this was about the highest voltage for the wiring, switches and fittings. It also suited his carbon-filament lamps.
But the generator and sub-stations had to be within 2 miles (5km) as the voltage was down to 80v at the end of the distribution when everyone turned on their lights and used the power.
This required generating plants all over New York. Along came Tesla with his concept of AC and all the problems of distribution disappeared.
The power could be produce 100 miles away and stepped-up via a transformer for transmission and then stepped down to a working voltage at the point of requirement.
Power was generated at Niagara Falls and everyone within 100 miles could be connected.
This also changed the voltage from DC to AC.
This brought many benefits.
The main one, as far as we are concerned, is the shock.
You get a shock when touching AC and this creates a reaction to remove your hand or finger very quickly.
But let's go back and explain a few of the terms we used:
The word SUPPLY refers to our electricity supply.
The word AC refers to the fact that the electricity is rising and falling at the rate of 50 or 60 cycles per second.
We use the words ALTERNATING CURRENT because this indicates the supply has power or energy to do work.
You cannot have CURRENT if you don't have VOLTAGE as the voltage "pushes" the current through a circuit.
You can have alternating voltage with almost zero current (Van de Graaff Generator) and almost no work can be done with this form of electricity.
Working on AC is said to be "safe" because it throws you off.
Some workers have been thrown across a room after getting a shock. Other's have diode instantly.
Don't try your luck. There are no second chances.
You need to know all the precautions before entering this field of work.
HOW DO YOU SERVICE 600,000 VOLT POWER LINES?
The insulators on 600,000 voltage power lines need to be serviced without disrupting the supply.
This is done with a helicopter and a man on a platform, lowered from the hovering 'copter on a winch.
The man is dressed in a conductive suit and the first thing he does is clip a conducting pole to the 600,000 volt wire. This immediately makes him 600,000 volt live. But he is only charged STATICALLY as he is not touching any other conductor and there is no flow of electricity.
The electricity flows around his body, through the suit but the actual flow of electrons is so small that the current is microscopic.
The suit must have a plastic coating to prevent corona discharge and now he can work on the line. He must no go anywhere near the metal-work of the pylon as 600,000 volts will jump many cm.
The same situation applies when a linesman connects power to a property while the lines are active.
He uses insulating gloves, however provided he touches only one wire at a time and stands on an insulated (isolated) platform, no current will pass through his body.
ELECTROCUTION is the FLOW of ELECTRICITY.
The human body can be raised to 600,000 volts and not be affected, but it can be shocked by as little as 80v in wet conditions.
The 600,000 volts is called a STATIC CHARGE and basically NO CURRENT FLOWS.
The 80v in wet conditions will allow a small current to flow and this will produce a "shock."