In addition to the physical handle test, there are electrical threshold tests to ensure current will not jump the contact gap or track to earth under specified fault conditions. This communicates very effectively that isolation has not been achieved and that the circuit or equipment is not safe, and has not been isolated. Should there be one welded contact, the OFF position cannot be reached, and a padlock device cannot be fitted, even with three times the normal operating force being applied and when released the handle returns to ON. Example these switches cannot be turned to OFF (handle moved to the off position) unless all the main contacts have physically opened. They are electrically capable of making and breaking the load under normal conditions and specified overload conditions and also pass electrical and mechanical tests to comply as isolators. They are switch devices that cut off a circuit or equipment from a source of power and ensure that the electrical circuit or equipment is completely isolated in order to conduct maintenance, servicing, modification or repair.įor the above applications, a 1 pole isolator for single phase, or a 3 pole isolator for three phase are generally installed. Commonly referred to as Isolating switches, an “On Load Isolator” is the most common piece of equipment used to achieve isolation. The purpose of isolation is to provide protection against electrical hazards such as electric shock, burns and ballistics (the effects of arc flash), and the unintentional start-up of machinery.
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