A switchgear is the core part of electrical systems responsible for system protection, voltage transformation, and circuit switching, effectively serving as the first line of defence against electrical faults and other issues. This means keeping it well-maintained and in good condition is paramount to protect people and other equipment should a malfunction occur, and this all starts with performing periodic health checks.
Through proper diagnosis and testing, organisations can identify potential issues that may affect reliability and get ahead of them before they become bigger issues. Examples of these include corona discharge and moisture, which, when left unaddressed, increases the risk of shortages and accelerates the deterioration process in the way of rusting and premature ageing. Below, we outline the main steps for verifying whether a switchgear remains in good working order.
An Overview of the Main Testing Procedures
First and foremost, it is essential to choose tests that are suited to your switchgear’s voltage levels. Additionally, routine maintenance could follow the switchgear health check, depending on the test results. Next, operators must coordinate an outage to begin switchgear testing by following three key phases.
The first phase takes place before the test and involves reviewing the switchgear’s equipment history and gathering all the necessary materials for the evaluation. Then, inform everyone in the facility about the schedule of the testing and develop a work plan to streamline the process.
The second phase entails disconnecting the unit and employing all the essential safety measures. This is followed by going through the inspection checklist and cleanings, as well as testing and replacing any worn-out parts. Lastly, a physical examination of the switchgear and its components will round things off along with double-checking the work done. Afterwards, restart the unit.
The third phase then focuses on creating a report of the testing, relaying any issues encountered to management, and developing the next steps if necessary.
Switchgear Testing Requirements
Testing switchgear units with MV and HV 3-phase AC circuit breakers operating at 50-60hz requires abiding by the IEC 62271-100 and its mandatory routine tests. Of course, some manufacturers may have their own additional test and inspection recommendations, so be sure to take note of them as well to ensure your unit meets the declared ratings and functions.
Some of the mandatory tests mentioned above include:
- Mechanical operation tests check all the switchgear’s mechanical operations to ensure the proper fit and function of components. These tests also check mechanical operating times at various voltage levels to confirm that mechanisms work as intended.
- Hi-pot (high-potential) test or dielectric withstand test is something that should only be performed after all the necessary repairs and cleaning for accurate results. This test injects a high voltage into circuit breakers to determine the condition of their insulation and ability to hold voltage, as well as checks for any current leakages.
- The insulation resistance test also applies voltage but into the switchgear insulation instead to check its resistance, particularly its megaohm value. If this value is too low, it often indicates a weakening insulation and requires immediate action.
Additionally, there are also standard tests designed for a switchgear’s MV and LV components:
- Functional tests: These simply verify the proper functioning of each unit.
- Auxiliary circulation tests: Measure the insulation for LV units.
- AC insulation tests: Assess the insulation condition between line, ground, and open contacts.
- Contact resistance tests: Check the current conductors and their contact resistance.
- Tightness tests: Annually check the tightness of breaker connections.
How Often Should You Do Switchgear Health Checks?
It is recommended to test switchgear units once a year and perform preventative maintenance consistently to maintain their performance and extend longevity. Specifically, take care to manually test and check the following components:
- Switches
- Circuit breakers
- Insulation
- Wiring
- Mounting bolt tightness
- Termination tightness
- Disconnect points
- Thermostats
- Temperature control panels
Beyond routine mechanical and insulation testing, it is also essential to conduct visual inspections to address common issues like debris buildup and part discolouration early on for optimal switchgear performance.
Conclusion
Placing switchgear health checks low on your list of priorities can be a costly mistake that puts the safety of employees and other equipment at greater risk. Alternatively, staying on top of it means less work and costs involved as it saves the business from avoidable loss of production, legal and medical expenses, OSHA visits, and more.
With that said, should your organisation ever need an expert on switchgear testing and maintenance, MES is the electrical engineering service provider you can always count on. In addition to switchgears, our expertise also covers electric motor rewinds, generator overhauling, and much more, making us the one-stop solution for all your equipment servicing needs.
