Switchgear power systems are known to be reliable and do not require major maintenance. However, because of this reputation for reliability, they tend to be the most overlooked aspect in a power control system. Despite the infrequent need for maintenance or repair, switchgear can encounter some serious problems such as irreparable damage to the switchgear power system. Failures are most likely to occur during or shortly after switchgear operations. Safe functioning is determined primarily by the way switchgear is operated, the condition of the equipment and the conditions in the electrical system at the time it operates. Since the proper functioning of switchgear is directly linked to the reliability of power supply, it is important to undertake maintenance on a regular basis.
Power Line presents an overview of key maintenance measures for switchgear…
Maintenance for switchgear power systems can be categorised as preventive or corrective maintenance and, less commonly, predictive maintenance.
Preventive maintenance is the key to keeping the system working properly. Preventive maintenance measures entail the regular annual inspection of components including circuit breakers, disconnect points and switches. The components should be manually tested to ensure smooth functioning. Small, continuous vibrations can cause damage to equipment. So mounting bolts and terminations must be tested for tightness to reduce vibration. Any loose mounting bolts should be retightened.
Further, visual inspection should be done to check if there is any dust accumulation or debris on or around the components. Dust can form an insulating layer around equipment, thus hampering the cooling process. This can lead to overheating and possible equipment failure. Besides, visual inspections should be done to check tightness or discoloration in any of the parts, which may be indicative of underlying problems. In addition, installing dehumidifiers and dust-free ventilation systems can help reduce dust and humidity, which affect the performance of the power system and potentially cause system failure.
Another factor that is often overlooked in the maintenance of switchgear is the temperature of the switch room or facility. Such equipment is highly sensitive to temperature changes. During annual inspections, the temperature control panels, thermostats and actual temperature of the room should be monitored to determine the proper operating parameters required by the equipment. Switchgear can be inspected using thermal imaging to assess the state of the system and predict failures beforehand. Temperature sensors can also be fitted to cables in the switchgear to continuously monitor temperature build-up.
Other methods of testing include partial discharge testing, using either fixed or portable testers, and acoustic emission testing using surface-mounted transducers for oil equipment or ultrasonic detectors used in outdoor switchyards. Performing preventive maintenance increases the longevity of switchgear.
Although well-planned and thorough preventive maintenance reduces the likelihood of a power outage or switchgear failure, there are times when equipment does fail. Such failures can seriously impede electricity supply and must, therefore, be corrected at the earliest. Therefore, it is advisable to stock original spare parts, especially components that are more likely to fail or are difficult to acquire at short notice.
When switchgear is overstressed, it should ideally be replaced. Fault current or energy can be reduced by installing reactors or reconfiguring the network. While network configuration is critical for the safe operation of switchgear, interlocks should ideally be fitted to prevent overstressing. In case only individual switchgear panels need to be replaced and the new switchgear is from a different supplier, it should be ensured that the rating of neither the existing nor the new equipment is compromised while connecting the busbar systems.
Predictive maintenance methods are used for condition-based monitoring of switchgear equipment. It is used to determine when switchgear maintenance is required. Maintenance measures are undertaken based on different parameters, techniques for acquiring the condition data and, most importantly, an understanding of the degradation mechanisms affecting the switchgear. To this end, intrusive and non-intrusive diagnostic tests can be conducted on switchgear. Tests should be undertaken especially at the time of commissioning in order to establish a baseline for future comparison.
Switchgear equipment typically requires a low level of maintenance. Getting into an annual inspection routine can potentially avert expenditure on new equipment installation or repairs. Simple maintenance measures can extend the equipment lifespan by lowering the likelihood of malfunctions.