How to measure the vector diagram of relay protection

Relay protection vector diagrams are measured using a vector analyzer to display the amplitude and phase of voltages and currents, allowing verification of phase sequence, magnitude, and relay functionality.

Tools Required

• Protection loop vector analyzer (e.g., ZC-650) capable of measuring three-phase voltage, current, phase, frequency, and power parameters .
• Variable current source and analog load for simulating normal and fault conditions in the circuit .
• Three-phase load and fault resistors to replicate operational and fault scenarios in a controlled environment .

Measurement Procedure

1. Connect the Analyzer: Connect the input of the current transformation device to the mains supply and the output to the circuit under test. Connect the analog load to the output of the tested circuit .
2. Simulate Load and Faults: Use three load resistors to simulate a three-phase load and three fault resistors to simulate a three-phase fault. Configure load and fault switches in a star connection to control the test conditions .
3. Display Vector Diagram: The vector analyzer will show voltage and current as phasors. The length of each vector represents amplitude, and the angle represents phase relative to a reference phase (usually UA), .
4. Verify Phase Sequence: The analyzer indicates correct phase sequence with a green square and incorrect sequence with a red square. White squares indicate amplitude without phase sequence determination .
5. Data Retention and Analysis: Use the retention function to freeze the vector diagram on the screen for detailed analysis. Switch between three-phase and single-phase interfaces as needed for specific measurements .

Interpretation

• Vector Lengths: Proportional to voltage or current magnitude.
• Vector Angles: Show phase relationships between currents and voltages.
• Phase Sequence: Ensures correct relay operation and prevents miscoordination.
• Fault Simulation: Confirms relay response under abnormal conditions, verifying protection logic and timing .

Best Practices

• Always start with all load switches closed and fault switches open to measure normal operating conditions .
• Gradually introduce fault conditions to observe relay response and vector changes.
• Document all measurements for comparison with relay settings and design specifications.
• Ensure safety by isolating high-voltage circuits and using proper protective equipment. By following these steps, engineers can accurately measure and analyze the vector diagram of relay protection, ensuring correct relay operation and system reliability.