SF6 relay is an important protection and control element in the power system. If the circuit breaker fails, it will cause great economic losses. To ensure the reliability of the circuit breaker operation, it is necessary to constantly monitor the various indicators of the circuit breaker. In particular, the density of SF6 gas must meet the requirements of relevant standards, so that SF6 circuit breakers can maintain good working conditions for a long time.
Monitoring and verifying the alarm and blocking action values (return values) of the density relays of newly installed SF6 gas electrical equipment and the density relays of SF6 gas electrical equipment in operation are very important to ensure the normal operation of electrical equipment.
I. SF6 relay test method
To calibrate the SF6 relay, the density relay calibrator can be used to calibrate the density relay and pressure gauge of SF6 electrical equipment.
II. SF6 relay test procedure
1. Cut off the gas circuit of the density relay of the device under test and the gas circuit of the device body.
2. Cut off the power supply of the density relay control circuit of the tested equipment.
3. Connect the gas circuit connection part of the sf6 gas density relay calibrator to the gas circuit of the measured density relay.
4. Connect the node socket of the density relay calibrator to the corresponding node of the measured density relay.
5. Adjust the pressure of the storage cylinder of the density relay calibrator to reach the rated inflation value of the measured density relay, and then reduce the pressure to the alarm and lockout pressure.
6. Record the action value or return value of the density relay reaching the alarm or lockout (the recorded value should be corrected to the pressure value at 20°C).
7. For equipment with a pressure gauge installed at the same time, when the sf6 gas density relay checks the alarm or blocking action value or return value, it can record the indication value of the pressure gauge at the same time, and compare it with the pressure value given by the density relay calibrator (in addition 2-4 points of different pressure values can be added as needed). The calibration of each pressure gauge should be 5-8 points.
8. The calibration of the density relay that is not installed is carried out in steps 3-6.
III. Judgment of SF6 relay test results
The calibration result of the density relay is compared with the manufacturer's setting value of the density relay's alarm and blocking node and its accuracy range. The calibration of the pressure gauge only gives the indication value of the pressure gauge and the corresponding SF6 relay calibrator. The given pressure values are compared.
IV. Precautions for SF6 relay calibration
1. The connection position of the contact socket of the density relay calibrator should be correctly selected during calibration, and the connection to the normally open or normally closed contact of the density relay should be avoided.
2. The pressure and temperature indications of the density relay calibrator used should be verified by the metrological verification department. The verification cycle of SF6 relay is handled according to the verification cycle of national pressure and temperature gauges.
3. When the test result of this operation does not conform to the factory value, the test shall be rechecked. When the failure is confirmed, the sulfur hexafluoride density relay should be replaced as required.
