The need for proper maintenance of switchgear has been increasing over the years as electricity networks are expanding and carrying increasing energy over longer distances. Maintenance of switchgear is critical to maintaining equipment integrity, ensure proper mechanical and electrical functionality, and optimise it’s useful life.
Electrical switchgear is composed of passive and active components. While passive components include horizontal and vertical bus structures, active components comprise power circuit breakers and fusible switching devices. Circuit breakers are used to turn on/off electric currents on the power transmission and distribution (T&D) networks for routine operations and protection of other equipment and personnel in case of an arc flash event. The proper maintenance of circuit breakers helps reduce the risk of an unplanned outage and extend the useful life of assets. A regularly scheduled preventive maintenance programme for switchgear is intended to detect, repair and replace affected electrical components, parts or equipment before they lead to catastrophic damages.
Maintenance of switchgear
Most companies undertake predictive maintenance for circuit breakers, which involves accurately predicting the condition of the breakers, without opening them up for inspection. This helps reduce maintenance costs and increase efficiency. A few other measures that can be adopted for switchgear maintenance are as follows…
- Infrared inspections: Thermal imaging (infrared) is a valuable practice that can be adopted while the equipment is being energised. Infrared inspections help identify loose bus connections before they result in a full or partial equipment outage. Thereafter, maintenance is scheduled to correct the identified issue.
- Regular on-site maintenance: Thorough on-site maintenance of circuit breakers includes inspection, cleaning and lubrication of primary and secondary disconnects; a racking mechanism; cell interlock adjustments; protective device testing; insulation testing; and circuit testing on a regular basis. Various factors such as moisture and heat combined with dirt, dust and other emissions in the environment which rapidly deteriorate the insulation, conductive materials and protective devices in the equipment need to be considered while determining the time intervals at which maintenance work should be carried out.
- Equipment reconditioning: In this process, the circuit breaker is initially tested against appropriate standards and then completely disassembled, cleaned and inspected. The damaged parts are refurbished or replaced, and the pivot points are relubricated before the circuit breaker is reassembled. Finally, the reconditioned circuit breaker, including new assemblies, is retested. Reconditioning should be performed when on-site maintenance work cannot bring the circuit breaker within the tolerances defined in current industry standards.
- Maintenance of records and trend performance: In certain circumstances, switchgear components can be outside the design tolerance levels defined in current industry standards though they may be able to stay in that condition for a long period of time and still be functional. To deal with such situations, tracking of test data and trends can give an estimate of the expected life of switchgear equipment and thus help undertake maintenance measures in the required areas.
- Equipment upgradation: Recent advances in technology have facilitated the production of circuit breakers with better performance, reduced maintenance requirements and on-board diagnostics. However, companies are faced with the choice of maintaining ageing equipment or replacing it with a new switchgear line-up to take advantage of new technologies. In this regard, a more cost-feasible alternative is to leave the existing switchgear structure in place and upgrade the equipment with state-of-the-art circuit breakers.
- Outsourcing preventive maintenance: Another important measure is outsourcing preventive maintenance through a long-term maintenance contract. Since very few companies can perform all the required maintenance activities, the service provider can create a multi-year contract, which will ensure effective maintenance of switchgear.
- Utilising predictive maintenance tools: There are several tools and services that can be utilised to predict equipment life and maintenance requirements. These tools include on-line monitoring systems that can warn of impending failures, wireless temperature monitoring systems, partial discharge monitoring systems, power system assessments, circuit monitors and intelligent protective devices.
- Short-circuit analysis study: A short-circuit analysis will determine if the switchgear is rated properly. With proper rating, faults can be detected easily with minimal effect on the switchgear.
In sum, proper maintenance of switchgear will help maximise its lifetime and reliability and improve the performance of T&D systems.