Protective relays are decision-making elements in the protection scheme for electrical power systems. They monitor circuit conditions and initiate protective action when an undesired condition is detected.
Protective relaying serves many functions including isolating faulted circuits or equipment from the remainder of the system so the system can continue to function, limiting damage to faulted equipment, minimizing the possibility of fire or damage to adjacent equipment, and minimizing hazards to personnel.
According to Reg. 110(4), ER (Electricity Regulations) 1994; any protective relay and device of an installation will need to be checked, tested and calibrated by a competent person at least once every two years, or at any time as directed by the Energy Commission.
Why is protective relay testing important?
When they are required to operate because of a faulted or undesirable condition, it is imperative that protective relays function correctly. A strong maintenance and test program will keep your protective relays in a high state of readiness ensuring they respond properly to normal and abnormal conditions and help you avoid equipment damage, prolonged downtime and employee injuries.
When protection relay testing is not carried out on a regular basis, the risk of dangerous electrical faults increases, potentially resulting in damage to equipment and harm to personnel.
Types of testing
There are three main types of protective relay testing (apart from testing after a fault occurs):
- Bench testing – This involves investigating the relay on its own and that it matches the design. This prevents more expensive and more time-consuming problems from occurring at later stages in a project.
- Commissioning testing – Once the electrical system has been constructed, commissioning the relay involves making sure the larger system functions as expected. For example, when the protection relay is attached to the switchgear, it should function as expected, react to interlocks and other simulated conditions. After this, the relay’s function will have been demonstrated.
- Maintenance testing – When maintenance testing is carried out, complete design intention is assumed, but relay behaviour must be checked under operation. Apart from relay-specific failures, the relay cannot detect changes in system characteristics, such as downstream network loads being changed over time. Such long-term changes may require the relay to be reprogrammed to ensure expected operation is maintained.
Safety is everything
Electrical safety is not an issue to be taken lightly. According to statistics released by the Fire and Rescue Department, a total of RM3.31 billion worth of properties were destroyed in fire-related incidents in 2018. Of that number, faulty electrical sources were at the very top of the list with over 5,300 cases recorded over the last three years.
This is the reason why at GreenBay, we take a proactive stance when it comes to electrical safety:
- All electrical works are carried out by a team of competent and qualified engineers.
- The electrical works shall be carried out in accordance with rules and safety regulations and best working practices.
- All installation shall be maintained in good working order and safety precautions shall be observed at all times to prevent danger.