13 What Is The Importance Of Testing Protective Relays?
Protection relay hot testing can feel like a game of walking-on-eggshells. Keeping your cool and following the procedure will help you avoid mistakes that can cause costly problems later on. Check the relay front panel and case for foreign objects that may interfere with operation. Ensure the settings are in accordance with the coordination study and engineered setting file provided by the equipment owner.
Commissioning
NETA-certified protective relay tester professionals assist with the field, shop and laboratory testing of electrical equipment. These professionals also perform routine maintenance, set up barricades and help to manage a wide range of general tasks that are required by a substation or switchyard.
Testing a protection system ensures that it works as expected and prevents more expensive and time-consuming problems from occurring in the field. Testing can reveal a number of issues such as switching errors, application shortcomings, pilot wire faults and more.
To perform a complete testing of a protection relay, you can use a test set to replace the CT/PT inputs with the actual in-service inputs. This allows you to create realistic fault simulations and verify that the element will ignore faults on the wrong side of pickup, and trip for the right ones. You should also verify the operation of all relay digital inputs and output contacts. This is important as it helps to reduce unplanned trips and equipment damage.
Maintenance
Maintaining a Protective relay tester is critical to protecting your system and extending its service life. Routine maintenance procedures include verifying the operation of all digital inputs, output contacts and settings, as well as the operation of the control annunciation systems. This testing can be done using simulations, lab tests and/or site visits.
If your system is protected by microprocessor-based relays, it’s important to download and compare their settings with the settings indicated on the latest coordination studies and setting sheets provided by the equipment owner. This will help ensure that the protection features continue to operate in accordance with the engineer’s intended design.
Inspect the relay case for physical damage and make sure it is clean. Check for shorting hardware, connection paddles and knife switches and remove any foreign material from the case. Also, check for target reset functionality and disk clearance and spring bias. This will also help determine if the relay is operating correctly and avoiding overheating.
Troubleshooting
A Protective relay tester works with a variety of electromechanical control equipment systems. They are responsible for conducting field, shop and laboratory tests, inspections, repairs, and replacements on assigned circuits and electrical equipment. They also work with energized power equipment such as voltage regulators and batteries.
When performing system functional tests, ensure that the relays function correctly as a coordinated unit through the interaction of each sensing and processing devices. Verify all interlock safety devices are in the correct position, along with bus restoration and transfer switches. Check for proper operation of metering circuits and relay alarms. Test lock-out relays and block close circuits. Check the operation of auxiliary relay digital inputs, indicating devices and communication lines. Inverse and definite time overcurrent, distance overcurrent and ground fault protection should be confirmed for each device in the system. Also verify metering calibration and the operation of control annunciation systems.
Installation
Relay Testers install, inspect and make minor calibrations to control circuits, voltage regulators, battery chargers, and electrical equipment in substations. They are also responsible for preparing and maintaining a variety of records, including test results, blue prints, diagrams, and other documentation. They also set up barricades and perform general housekeeping duties to maintain safe work areas in the power plant and switchyards.
Testers ensure that metering relays and current transfer circuits are operating properly, and verify the operation of control annunciation systems. They also test the operation of auxiliary relays and trip units.
Protective relays are critical to power grid safety. They detect dangerous or intolerable conditions and then either initiate, permit or interrupt switching to prevent injury or extensive damage. They can be microprocessor relays that incorporate numerous protection functions into a single unit or electro-mechanical relays. Modern digital relays can be more complex, incorporating internal logic and control algorithms. They are characterized by their ability to handle more complicated fault conditions than electro-mechanical relays.
Conclusion
Protective relay tester is used in power utilities, power plants and industrial installations. It is also frequently employed by testing service companies who need to perform routine tests quickly and easily. Verify that relay settings match the latest coordination and arc-flash study or engineered setting files. Conduct insulation resistance tests on electromechanical relays circuit-to-frame and ground.