Understanding Electrical Safety

UNDERSTANDING ELECTRICAL SAFETY

Power types:

· Direct Current (DC) – A single direction flow, positive to negative, provided from Batteries or DC generators

· Alternating Current (AC) – an alternating forward & back flow at 50 hertz (cycles per second) provided from generators and Eskom

· Static Electricity - Electron charges differenced often related to friction between different materials (eg. wool and synthetic fabrics)

Power terms:

· Volts: like pressure in a hosepipe. At 220 volts for a single phase power supply or 380 volt 3 phase normally used for industrial type applications

· Amps: like water quantity in a hosepipe. Commonly 10 amps to 25 amps at homes

· Watts: Watts = Amps x Volts, being the amount of electricity used or consumed by the appliance

Consider a double plate hot plate with 2 x 1000 watt plates on a 220 volt electrical supply. How many amps will it use?

Amps = watts / volts = 2000 / 220 = 9 amp. So the hot plate cord should be at least 10 amp rated, while a 15 amp cord will have a lesser chance of overheating and so will be even safer in use.

Safety Issues:

· Circuit breakers (trip switches) and Fuses: They are provided in live line of electrical circuits to cut off the electrical supply to prevent more that the rated amount of amps of electricity being drawn from the circuit (ie. stops circuits being overloaded

· Main stitches (or double dipole switches): They are provided in electrical circuits to isolate both the live and the neutral wire power supply to a circuit. This is important because of the nature of an alternate current supply.

· Earth leakage: This is a safety device which cuts off the electrical supply (both live and neutral) when it detects as little as 30 milliamps difference in the power flowing in the live and neutral wires. This leakage is caused by the power leaking through another route to an earth including through a person’s body to an earth while getting a shock and so cuts off the electricity. A shock of over 30 milliamps can cause heart fibrillation.

· Polarity: This refers to the correct wiring of electrical equipment, especially plugs, extension leads and similar. In normally electrical wiring, the live (brown) wire goes to the on-off switch then to the appliance. If the wiring is wrong polarity wired the live goes to the appliance and later leaves the appliance at the switch, which means you can be electrocuted with the on-off switch being off.

· Plug wiring: It is important that all three pin plugs are correctly wired. With the plug open and the pins facing away from the brown (live) wire is to be attached to the bRown RIGHT pin terminal, the bLue (neutral) to LEFT pin terminal & the green/yellow wire, the eArth wire to the APEX (the top) terminal pin.

· Double insulation and two pin (eruo) plugs: Most hand appliances like electric drills, hair driers, food mixers, etc have a square in a square symbol on the manufacturer’s plate (eg. ).

This symbol indicates that the appliance has a double insulated design, which is a

design to avoid the possibility of giving an electric shock under normal use conditions. Consequently there is no need for an earth wire so a double insulated appliance is normally fitted with a two pin plug.

· Multi-plugs & extension cords: The Watts = Amps x Volts equation must be considered to ensure the multi-plug or extension has the correct power capacity rated cord for the proposed use purpose. An under sized capacity cord is likely to overheat causing an electrical short and a possible fire.

If it doesn’t look right, don’t take chances with electricity, as it can kill, get an electrician to check it

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