When an alternating current is made to flow across multiple conductors of a transmission line where its spacing is large compared to their diameters, the air surrounding the conductors (composed of ions) is subjected to…
Current transformers normally have a single conductor as a primary winding connected in the run of the line conductors. The voltage which appears across the primary terminals is very small and therefore the voltage at…
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…
Before starting to write a switching program, it is important to understand and use standard terminology. The table below includes some common fields found on templates. Program Field Meaning Program number This is obtained…
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…
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…
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…
Ring main units (RMU) are widely used in industry and for distribution systems. RMUs operate independently, which means that it is possible to earth an incoming supply cable while it is still energised from the…
The standard power transformer is “on-load tap changing” (OLTC) to ensure that the secondary distribution voltage is within limits although the primary voltage may change. Tap changer range is usually from 15% above normal to…
