What are the best practices for testing protective relays and coordination settings?

1 Plan and prepare

Before conducting any testing, you should plan and prepare the test procedure, equipment, and personnel. You should review the relay manuals, drawings, schematics, and settings to understand the relay functions, features, and logic. You should also identify the test points, connections, and isolation methods for the relays and the associated equipment. You should select the appropriate test instruments, such as relay test sets, voltage and current sources, meters, and software tools, and verify their calibration and functionality. You should also ensure that you have the necessary safety precautions, such as personal protective equipment, lockout/tagout procedures, and communication protocols.

2 Perform functional tests

Functional tests are the tests that verify the operation and response of the relays to various input signals and conditions. They simulate the actual fault scenarios that the relays are designed to detect and clear. Functional tests can be performed using primary or secondary injection methods. Primary injection involves applying high voltage and current to the relay inputs through the actual power system components, such as transformers, breakers, and switchgear. Secondary injection involves applying low voltage and current to the relay inputs through the test set or other sources. Primary injection is more realistic and comprehensive, but also more complex and hazardous. Secondary injection is simpler and safer, but may not cover all the aspects of the relay operation.

3 Perform coordination tests

Coordination tests are the tests that verify the coordination settings of the relays with respect to each other and the power system characteristics. They ensure that the relays operate in a selective and timely manner, clearing the faults with minimal interruption and disturbance to the system. Coordination tests can be performed using time-current curves, which plot the operating time of the relays as a function of the fault current magnitude. Time-current curves can be obtained from the relay settings, manuals, or software tools. Coordination tests can also be performed using fault simulation methods, which apply different fault types and locations to the system and measure the relay operating times and tripping sequences.

4 Perform communication tests

Communication tests are the tests that verify the communication functions and features of the relays, such as remote control, data transfer, status monitoring, and protection signaling. Communication tests are especially important for relays that use digital or fiber-optic communication channels, such as IEC 61850, DNP3, or Mirrored Bits. Communication tests can be performed using communication analyzers, which capture and analyze the data packets and messages sent and received by the relays. Communication tests can also be performed using test sets or software tools, which simulate the communication commands and signals to and from the relays.

5 Record and analyze results

After performing the tests, you should record and analyze the results to verify that the relays and coordination settings are functioning properly and within the expected ranges and tolerances. You should compare the test results with the relay settings, specifications, and requirements, and identify any deviations, errors, or anomalies. You should also compare the test results with the previous test results, if available, and note any changes, trends, or deterioration. You should document the test results in a clear and concise format, such as a test report or a test certificate, and include the test procedure, equipment, data, and analysis.

6 Troubleshoot and correct issues

If you find any issues or problems with the relays or coordination settings during or after the testing, you should troubleshoot and correct them as soon as possible. You should follow the manufacturer's instructions and recommendations for troubleshooting and repairing the relays, and use the appropriate tools and techniques. You should also consult with the system operator, engineer, or designer to determine the best course of action for correcting or adjusting the coordination settings, taking into account the system conditions, constraints, and objectives. You should retest the relays and coordination settings after making any changes or corrections, and confirm that they are working correctly and satisfactorily.

7 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?