The Role of Low Voltage Industrial Circuit Breakers in Enduring Personnel Safety

Unsafe workplace conditions’ regarding electrical and industrial workers is an issue that has recently been thrust into the spotlight. This is due to ever increasing media and expert criticism regarding the number of injuries and deaths every year from electrical accidents in industrial environments. It was found in the United States in 2008 alone that over 2000 people were injured from electrical faults such as electrical arcing.

Electrical arcing faults are an extremely dangerous phenomenon which can occur when an electrical current jumps a space in a circuit. These events can go on until physically interrupted or until electrical system components melt or catch fire. For this, and other reasons, safety components such as fuses, electrical safety relays and circuit breakers are employed in industrial electrical systems.

Low Voltage industrial circuit breakers from a Safety Perspective

Industrial Circuit Breakers are one of the main safety components in low voltage industrial electrical systems such as switchboards or switchgears. An industrial circuit breaker is essentially “a device designed to open and close a circuit”, and most importantly in the case of this paper to “open a circuit at a pre-designated overcurrent without damaging itself”.

Commonly, low voltage industrial circuit breakers involve three important components regarding safety:
A frame or mold case
A trip mechanism
Arc inhibition devices

The frame or mold cases around circuit breakers aid in protecting personnel by generally deny access to the internal workings of the breaker. When the circuit breaker is live, dangerous voltages flow through the internal components, such as the trip mechanism, posing an electrocution risk for maintenance workers; hence the casing acts as something of an insulator.

The trip mechanism located within circuit breakers however, is one of the most important breaker components, as it causes the breaker to ‘trip’ or to deny power to faulting electrical components in the event of an overload or short circuit. This ‘tripping’ can occur via thermal triggers due to heat produced by overload currents, or due to magnetic triggers produced by high level currents passing through a conductor, and triggering an electromagnetic trip device. A serious problem with normal tripping devices however is that they only trigger due to short circuits or overloads, and not in the hazardous event of an arc fault.

This makes arc fault inhibition devices such as arc extinguishers, and the recently developed arc fault circuit interrupters, integral parts of this type of circuit breakers. Arc circuit interrupters basically monitor the current flow through the circuit breaker and use sensing circuitry to distinguish between wanted and unwanted events. This means that normal arcing does not trip the breaker, however arcing faults do.

It can therefore be concluded that industrial circuit breakers and the related components such as fuses and safety relays play an extremely large role in protecting not only technicians and electrical personnel, but also general industrial workers. With continuing advances in technology regarding circuit breakers in particular it can be expected that the safety of these devices will only continue to improve.