A well-planned operations and maintenance (O&M) of substation and switchgear assures reliable supply and reduction in failures. Many failures can be detected during substation and switchgear maintenance routines, thereby reducing the risk of significant plant downtime and preventing future problems. The risk of an unexpected breakdown in the substation and switchgear can lead to huge time and cost overruns for utilities. Maintenance involves periodic planned inspections, checking, testing and troubleshooting to ensure the correct operation of all components and their interaction during the plant life cycle. Each device requires a different strategy. Implementing the right action at the right time will define different electrical substation and switchgear maintenance procedures, whether time, condition or reliability based. All of them must be supported by suitable testing tools.
Power Line presents an overview of key maintenance measures for substation and switchgear…
O&M strategies
Substation: Over the years, three main maintenance strategies have been developed, based on utility preference, to maintain principal assets. In time-based maintenance, there is periodic maintenance according to the manufacturer’s generic maintenance schedule. This may include the provision of spare parts and consumables, and the replacement of worn-out components or systems during service life. Under this strategy, preventive maintenance will be carried out at predefined intervals based on the experience of usage. Another strategy is condition-based maintenance. Under this, maintenance planning is done according to the condition of the equipment. Condition-based monitoring of substation assets can be undertaken through a combination of intelligent electronic devices, smart sensors, fully secure communications/ open protocols and intelligent head-end, which is a user-friendly software. A prerequisite is a detailed condition evaluation of the installed equipment. The actual equipment condition is continuously assessed by the online detection of significant working device parameters and their automatic comparison with average values and performance. Maintenance is carried out when certain indicators give the signal that the equipment is deteriorating and failure probability is increasing. This strategy, in the long term, helps in drastically reducing the costs associated with maintenance, thereby minimising the occurrence of serious faults and optimising the management of available economic resources. Reliability-centred maintenance is the third method considered by utilities. Substation reliability modelling enables customers to understand the risk associated with each of its components. Reliability-centred maintenance is based on optimising maintenance investment by limiting the execution of unnecessary tasks while focusing on substation components, which represent a higher risk. This evaluation includes failure mode and effect analysis to determine the best maintenance strategy to maintain reliability. The life cycle cost-based evaluation of this strategy has to be derived from CBM analysis.
Switchgear: Maintenance of switchgear power systems can be categorised as preventive or corrective and, less commonly, as predictive maintenance. Preventive maintenance is the key to keeping the system working properly. It entails 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. 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.
Conclusion
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.
One of the dominant components of operating costs is maintenance and associated costs. The decisive parameters have to be identified along with their influence on the overall cost. The choice of maintenance strategy is dependent on various factors including timely action supported by suitable testing tools. Ultimately, getting into an annual inspection routine can potentially avert expenditure on new equipment installation or repair.
Net, net, simple maintenance measures can extend equipment life by reducing the probability of malfunctioning.