Switchboards and Safety Switches
Think of your switchboard and it's control equipment as a line of defense between you and the electrical current that supplies all your circuits. Ceramic fuses and circuit breakers are there to protect the cables if they become over loaded, once they reach the limit they should trip instantly. They aren't there to protect you from an electrical fault. For this you need a safety switch, also known as a Residual Current Device. Safety switches are there to protect you if you come into contact with a live object. Not only will they protect you but they also detect faults in any appliances and trip instantly before a dangerous situation occurs.
Safety switches are now, and have been for some time, mandatory in Australia and New Zealand. The most common cause of death by electrical shock can occur within 25-40 milliseconds, so a Residual Current Device detects a leakage of current before it can pass into the operator. RCDs measure the current between the live and neutral conductor. When the sum of the current changes or does not remain zero, leakage is detected and the device opens its contacts to stop accidental electrocution.