Earth Leakage #1
A company that installed appliances on their client’s behalf called for technical support after two people had received a shock from one of their appliances. The appliance was subjected to an electrical safety test and passed with flying colours.
Two hours later, the technician who conducted the test received a call stating that the appliance had given an employee an electric shock. The technician was surprised as he had just tested and passed the appliance.
The technician returned to the site, disconnected the appliance from the power supply and retested the appliance. Once again it passed. He disconnected his test equipment and reconnected the appliance to the mains power supply, inserted his servicing key and went to open the door to the servicing compartment. To his surprise, he too received an electric shock.
Investigations found that the electrical installation in the building was faulty, having a high earth resistance to the switchboard and that only when the appliance was connected to the mains power supply and running, were relays activated allowing current to flow throughout the entire appliance. A hitherto in-power circuit had a serious earth leakage that rendered the appliance unsafe.
This fault could only be detected with an Earth Leakage test conducted whilst the appliance was running.