(1) The equipment has SF6 inflation system, which can help density relay to easily and quickly inflate when testing samples.
(2) The device has two kinds of sensors at the same time, namely, relative pressure sensor and absolute pressure sensor. Since there are many types of SF6 relays, the role of these two sensors is to measure the values of different types of relays.
(3) Compared with SF6 gas testing, the traditional density relay calibrator has certain measurement errors, so SF6 gas testing is generally adopted in practice to improve testing efficiency and accuracy.
SF6 relay is mainly used to monitor the change of SF6 gas density in circuit breakers. During operation, SF6 relay has poor performance in testing SF6 gas density under extreme temperature, which leads to increased error. Therefore, it is of great significance to study the performance of SF6 relay under extreme temperature.
The testing device of SF6 relay is mainly divided into two parts: constant temperature control box and calibration platform, which both operate at extreme temperatures. The high and low temperature control box can be used to control the temperature between -40℃ and 160℃. Then use the SF6 relay to conduct precise testing.
In order to connect the data, the control box and the platform must be used together so that the air pressure and temperature between them can be effectively regulated. The calibration software automatically reads and stores test values based on temperature, including contact action values and contact return values. Since there is a certain curve relationship between pressure value and temperature, whether the operation value of SF6 relay is qualified can be judged by the change of the relationship between them.
1. Ensure the accuracy of reading pressure value
During the test, it is found that the value on SF6 relay does not match the pressure value collected by the system, and there is a considerable error.
Cause of the problem:
(1) Because the thickness of the pipeline is easy to change greatly, the pressure transfer is relatively unstable, making the instantaneous pressure unbalanced;
(2) In a low temperature environment, if the pressure indication value of SF6 relay near and far the air supply port does not match, and the near end is greater than the far end, it means that the distance between the installation position of the density relay and the position of the air supply port is not equal;
(3) Because the distance between the gas density meter and the pressure sensor is far, the reading value is not timely.
In view of these three problems, specific improvements can be made to the pipeline, such as replacing the mounting frame of the density relay, adjusting the position so that the distance between the relay position and the position of the air supply port is equal; Adjust the position of the pressure sensor to the near end of the relay to improve the timeliness and accuracy of reading the pressure value.
2. Ensure the accuracy of reading the temperature value
Adjust the temperature in the high and low temperature constant temperature control box to -40℃, and then put the SF6 relay into it for two hours for testing.
It is found that the temperature read by the system after adjustment is -33 ° C instead of -40 ° C. The reason for this is that SF6 gas liquefies with increasing pressure.
Then a certain amount of heat is released to make the test temperature near the gas path higher than the adjustment temperature. To ensure that the actual ambient temperature reaches -40 ° C, adjust the position of the temperature sensor and keep it away from the gas path.