If the lights are on, everything is fine with the electrical system. This is a common assumption, but issues sometimes can be lurking behind the scenes.
Figure 1. Performing the manufacturer’s recommended maintenance and testing of a circuit breaker will extend the equipment’s useful life.
Switchboards and switchgear are utilized to distribute electricity within a facility. Switchboards are more commonly used in commercial and light industrial applications, while switchgear is usually specified in heavy industrial applications, where the demands on the equipment require more robust construction. To maximize the useful life of the equipment and to mitigate the risk of an unscheduled power outage due to equipment performance, it’s critical to properly test and maintain the switchgear and switchboards that distribute electricity throughout the power distribution system (Figure 1).
Electrical switchgear has two types of components, which can be referred to as passive and active. The passive components include such things as the steel framing channels, cover plates, barriers, and horizontal and vertical bus structures, as well as components that make up the mechanical structure of the equipment. The critical active components are the power circuit breakers or fused devices that comprise the overcurrent protective system.
The main function of the active components is to protect assets and personnel. Both the passive and active components require regular maintenance to ensure equipment integrity, as well as proper mechanical and electrical functionality, and to provide protection for the equipment’s useful life. Major electrical equipment manufacturers generally recommend annual maintenance for power circuit breakers to ensure proper operation and maintain equipment warranties. This maintenance consists of cleaning and lubrication of the primary and secondary disconnects, racking mechanisms, and cell interlocks. A thorough on-site maintenance workscope for low voltage power circuit breakers includes:
Figure 2. Even with proactive maintenance, circuit breakers can be upgraded, while the switchgear structure, conduits, cabling and footprint are left intact.
- cleaning and lubrication
- overcurrent protective device testing
- insulation testing
- charge/close/trip circuit testing.
The use of new or refurbished parts or subassemblies may be required to return a circuit breaker to good operating condition.
A more intensive maintenance option for circuit breakers is in-shop reconditioning. The breaker is initially tested against ANSI standards and then completely disassembled, cleaned, and inspected. Damaged parts are refurbished or replaced, and pivot points are relubricated before the circuit breaker is reassembled. The reconditioned breaker, including the new assemblies, is retested against ANSI standards. This option should be performed when the on-site maintenance workscope can’t bring the breaker within tolerances defined in current industry standards. As part of this service, the trip unit can be retrofitted to a modern digital device.
Figure 3. One advantage of replacing with new switchgear is the ability to take advantage of current technology.
Even with annual maintenance, however, power circuit breakers may need additional upkeep or upgrades (Figure 2). Factors to consider include the operating environment, availability of spare parts, reliability, and the cost of ongoing maintenance. There may also be the need to increase the switchgear’s fault or continuous current rating, or the desire to upgrade technology. As a result, facility managers are often faced with the choice of maintaining aging or obsolete equipment or replacing it with a new switchgear lineup to take advantage of current technology (Figure 3).
Circuit breaker failures
Electrical equipment life can be defined as the duration until the equipment no longer performs its intended function, either mechanically or electrically. Although passive components require maintenance, it’s typically the nature of the active components, along with insulation life, that defines the expected life of the switchgear. When circuit breakers don’t operate properly, there are typically no advance indicators, unless electrical testing has been utilized to track performance. Industry groups, such as the IEEE Circuit Breaker Quality and Reliability working group, have analyzed the factors that affect the condition and performance of circuit breakers.