Equipment Condition Monitoring

Strategies for improving substation performance

Utilities need to make decisions regarding power network equipment performance, maintenance schedules, replacement of existing assets and addition of new ones on a regular basis. This not only has a significant impact on their  operational performance but also affects costs. To facilitate this decision-making process, companies undertake equipment condition monitoring (ECM), which provides valuable data on the working condition of select grid components to both operators as well as asset managers.

Power utilities employ ECM to maintain electric equipment in top operating condition, thereby minimising the number of interruptions. Equipment operating parameters are automatically tracked through ECM, to detect the emergence of any abnormal conditions. It quantifies the risks associated with equipment failure, which helps the concerned department to take timely action to improve reliability and extend equipment life. Typically, this approach is applied to substation transformers and high voltage electric supply circuit breakers to minimise the maintenance costs of these devices, improve their availability and extend their useful life.

Typically, monitoring of specific and individual components of substation equipment is undertaken rather than of the complete substation. It can take many forms including manual inspections (periodic visual inspections), continuous monitoring with a change-in-status/condition alarm as the only output (low-level alarm), periodic automated monitoring connection of portable analysis instruments (dial-up computer analysis) or continuous online monitoring (full-time measurement of parameters to assess the condition while in service). This monitoring provides data that is diagnosed through innovative algorithms and knowledge modules, which allows accurate evaluation of condition information and predictive diagnosis.

Benefits of ECM

Equipment availability and reliability can be significantly improved through ECM, by reducing the need for offline maintenance and testing, as well as the number of equipment failures. ECM has several advantages for substations in terms of operations and maintenance (O&M), as well as safety of equipment. It ensures continuous real-time condition monitoring of all substation assets.

ECM also helps determine the operational ability and status of the substation equipment through online monitoring and therefore provides information on both current conditions as well as historic trends. It also helps detect abnormal conditions in the working of the equipment and initiates action to prevent failure.

In addition, ECM analyses data to identify potential equipment failures and therefore undertake maintenance planning for a large population of similar equipment. ECM can help determine the anticipated remaining life of the equipment by employing life assessment techniques.

Besides, it ensures proper verification tests by confirming correct installation conditions and adjustments. It automates the collection and preservation of baseline condition data and characteristics. ECM also provides information on the prior condition of equipment after a failure has occurred and prevents unsafe conditions for workers.

Further, ECM plays an important role in improving the performance of substations through greater grid reliability and in reducing O&M costs. Through real-time monitoring, ECM enables fewer outages and asset failures. As a result of reduced outages, reliability improves as reflected by lower SAIDI (system average interruption duration index). Similarly, ECM helps bring down O&M costs via condition-based maintenance, implying servicing of an asset only when it is needed. It helps in extending the asset’s lifespan, thus reducing capital replacement costs. It also helps achieve greater efficiency with reduced manpower levels and higher corporate savings. Improved safety for the workforce and better power quality through ECM ensures employee retention and customer satisfaction.

Applications of ECM

ECM involves the use of condition-based monitoring systems for substation assets through a combination of intelligent electronic devices, smart sensors, open protocols and Head-End software. It can be seamlessly integrated in the existing substation communication and visualisation infrastructure, from simple bay controllers to high-end control centre applications. ECM solutions can be customised as per the individual requirements of the substation to monitor all relevant components of the electricity supply network – from transformers and switchgear to overhead lines and cables. ECM systems are implemented in such a way that complete asset-related condition information is available to the operator and the asset manager in a consistent format.

The application of ECM includes real-time monitoring of partial discharge in transformers and gas-insulated switchgear; the temperature, pressure and liquid level of oil in transformers; moisture levels, dissolved gas analysis, cooling performance, load tap control, fault location and loading on transformers; and performance of breakers, bushings, capacitor banks, surge arrestors, reactors and protection system condition monitoring.

Sources of monitoring data

There are various sources from which ECM systems can obtain data for substation equipment. This involves the use of specific monitors, available signals, and data and energy management systems. Direct and specific monitoring devices are available for specific components of equipment or even for the entire substation.

The available data signals are an important source of information for monitoring purposes. In order to optimise the monitoring process, the most cost-effective scheme should be adopted. In substations, data pertaining to current and voltage transformer outputs, digital relay interrogation for fault magnitude and interrupting time, event timing, control input and outputs, and temperature data can be measured. Considerable information can be gathered from substation parts such as  circuit breaker parameters and transformer parameters.

The energy management systems deployed by large electrical systems are capable of collecting huge volumes of data. Appropriate data mining techniques can be used to derive significant information without investing in an unreasonable amount of monitoring devices.

Best practices

Several best practices associated with ECM can be adopted for substations. The use of reliability-centered maintenance, as well as failure mode, effects and criticality analysis (FMECA) can assist in selecting and optimising the most appropriate attributes monitored for any given situation and equipment. Centralised records of equipment failure and its causes help in efficient monitoring. In order to be truly effective, ECM should be a part of an overall condition-based maintenance strategy that is properly designed and integrated into the regular maintenance programme. Age-related data collection from substation equipment and focus on the equipment that has the highest risk associated can help in achieving the best results through ECM. The use of standardised diagnostic and failure investigation guides can help in the failure analysis of substation equipment. Moreover, a cost-benefit analysis of monitoring will help in the proper application of ECM.

The way forward

The proper understanding of the condition of substation equipment helps prevent failure, maximises future operations, enables appropriate scheduling and determines the extent of inspections and maintenance, provides personnel safety, and protects the environment. In the near future, ECM can grow multifold to cover a wider range of substation equipment. However, the challenge is to gather the expertise of equipment manufacturers, users, manufacturers of monitoring devices and systems integrators to ensure the seamless delivery of equipment condition information in an effective, efficient and economic manner.

A broader perspective for identifying monitoring opportunities as well as conducting research on failure causes is essential for the growth of ECM techniques. Individual online monitoring efforts need to be integrated with large and long-term solutions for a modular approach towards the implementation of online condition monitoring. The standardisation of online condition monitoring systems and protocols is required instead of the current system wherein ECM applications are implemented on an ad hoc or experimental basis.

Future advances in online monitoring must be integrated into the current systems to improve the existing substation equipment. Expert systems need to be developed for online monitoring to translate data rapidly into recommended action. Further, proper education and training facilities for employees regarding online monitoring systems are also significant.

Net, net, ECM is an effective, economic and efficient means of gaining the required understanding of equipment condition through monitoring and tracking of data regarding equipment failure and taking necessary preventive actions.

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