Switchgear (e.g. fuses, circuit breakers, and electrical disconnects) is considered the component in an electrical system that isolates electronic hardware, preventing it from being ruined by an electrical current that may be excessive, which often can happen in a power surge. To prevent such damage-and likewise to avoid fires and injuries-facilities frequently use one of the following kinds of circuit breakers (CBs): oil, gas, air, or vacuum.

Examining Oil Circuit Breakers

An older form of switchgear, oil circuit breakers rely on oil vaporization to send a jet of oil through arcs which extinguishes them. Oil CBs in many cases are the target of retrofits that upgrade them with newer technology.

Looking at Gas Circuit Breakers

Gas circuit breakers commonly stretch arcs with a magnetic field, after which depend on the dielectric strength of SF6 gas to extinguish them.

Examining Air Circuit Breakers

As their label suggests, air circuit breakers use air as an extinguishing method. This is done by (a) puffing air at an arc, or (b) swinging the contacts into a sealed chamber, where the arc is extinguished simply by air which escapes in the chamber.

Going Over Vacuum Circuit Breakers

Vacuum circuit breakers put out arcs simply by stretching them. As there is nothing to ionize besides the contact material, vacuum CBs need only stretch arcs a small amount, generally less than 3mm. Because of their extinguishment proficiency, vacuum CBs in many cases are reported to be "arc-resistant."

The Advantages of Arc-Resistant Switchgear Retrofits

Arc-resistant switchgear is useful for any facility that would like to reduce the impact of internal switchgear faults, such as: ruined equipment, building fires, and injured equipment operators. In most cases, these kinds of tragedies happen all at once, presenting a significant budgetary burden that the right retrofits may have prevented. To understand the advantages of arc-resistant retrofits, it can help to check out what can happen in their absence.

The Details of an Internal Switchgear Fault

An interior switchgear fault that comes from an un-extinguished arc commonly occurs in four different phases, with phases 2 and 3 lasting only milliseconds:

Phase 1

Also called the compression phase, this is when arcs build up to the point they achieve maximum internal pressure.

Reviewing Phase 2

Also called the development phase, this is where the pressure relief vent actually starts to open as arcs display wave action along with possible under-pressure.

Reviewing Phase 3

Also called the emission phase, this is the time the pressure relief vent has opened up as well as the gas in the gear housing reaches arc temperature.

Phase 4

Also known as the thermal phase, this is when arcs consume all combustible substance for their environment until they're extinguished.

Because phases 2 and 3 occur in a matter of milliseconds, it really is not possible for equipment operators to flee the danger zone before stage four commences. Consequently, 2 optimal safety measures to protect against internal switchgear arcs are actually (a) strategic retrofits to replace old circuit breaker systems and (b) replacing weak gear housing with more powerful housing to minimize exterior effects (e.g. replacing metal-enclosed housing with metal-clad housing). Before it decides on retrofits, a company should have its switchgear inspected by way of a generator services provider who specializes in switchgear retrofits.