The following basic types are available, typically rated at 350 or 500 MVA at 11 or 22 kV respectively: bulk oil minimum oil air break vacuum SF6 Circuit breakers are designed to deliberately create an arc, and thereafter to control…
The main four different switches used in a power system are: Circuit breakers are designed for controlled closing and controlled or automatic opening of load and fault current. Their duties are to close onto a fault and to automatically open…
The incident energy determined at each assessable location will fall within a defined arc flash/arc blast PPE category, as defined in the table below. Incident Energy PPE Category Cal/cm2 >1.2 to 4 1 >4 to 8 2 >8 to 25…
Arc flash/arc blast hazard labels inform personnel of the arc flash/arc blast hazard and the required PPE at each switchboard or arc flash/arc blast hazard location. The labels should present the following information: electrical hazard and danger symbols; arc flash/arc…
The likelihood of an arc flash/arc blast event is dependent upon the type of activity being undertaken at the time. It is generally accepted that the greatest likelihood occurs when there is direct interaction by an individual on energised equipment…
Arc faults are potentially fatal to any personnel in the vicinity. The intense heat of the arc flash/arc blast can severely burn human skin and ignite the clothing of anyone within several feet of the incident. Treatment for arc flash/arc…
The safe approach distance (SAD) is based on an “exclusion zone” principle. This principle defines an area around an exposed conductor into which no part of the person, mobile plant or object (other than approved insulated objects) may encroach unless…
An arc flash/arc blast is a dangerous electrical plasma explosion created by a short circuit through air that causes electric current to flash over from one exposed conductor to another or to ground. An arc flash/arc blast is characterised by…
The main considerations of safe working procedures on electrical equipment are to ensure safety of workers and safety of the general public. In addition to this, the continuity of supply, and the welfare of plant is important. To be able…
Power systems are effectively earthed by the neutral points being connected directly to earth. The only resistance being the inherent resistance of the connections and the earth itself. A system fault comprises either one or more phases being accidentally connected…