Rabu, 31 Desember 2014

Electrical Knowledge - 1 - Switchgear

Nemu artikel bagus di gugel tapi lupa nama situsnya apa,,, ijin share ya siapapun yang sebenarnya nulis artikel ini... ;)

A circuit is a path that ends where it starts, like a race track. One lap is one trip around the circuit. Electricity only flows in circuits composed mainly of wires connecting power sources and loads.
Turning off the eletricity involves disconnecting a wire in the circuit, also called opening the circuit, or "breaking the circuit". Reconnecting or turning on the circuit is also called closing or "making" the circuit.
Making and breaking are called switching.

Switchgear normally refers to an assembly of conductors and supporting structures designed to switch, i.e make and break, connections, usually in high power circuits with capacity of hundreds thousand of amps. This discussion applies equally to any circuit ampacity.
When a switch opens a circuit, an electrical arc forms betwee its contacts and, similar to arc welding, this arc readily melts metal, so its energy must be controlled to keep it from melting and destroying the switch.
The part of the switch that quenches the arc is often called the "arc chute". Also, if the switched contacts do not have enough metallic mass, a high current can "spot weld" them together before the switch (e.g circuit breaker) can be automatically opened.
The most current a switch can be expected to pass is called the "short circuit current" that occurs when the load that the circuit's current is  bypassed with a "short"or inadvertent connection. So the breaking capacity of switchgear is the most a current  switch can passwithout meting down, welding together or exploding, when opening a circuit under full load or short circuit conditions.

To select a proper switch, the avalaible fault (short circuit) current must be determined and it is limited by the ability of the power source to provide power and the resistance (more properly impedance) of all the components supplying the switch. This fault current determines how much energy would be avalaible if an arc flash occurs, and also determines what level of PPE (Personal Protective Equipment) an electrician would be required to use if working on a "live"

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