SF6 gas density relay is mainly used to monitor the change of SF6 gas density in circuit breaker. During operation, the SF6 relay will have poor SF6 gas density at extreme temperatures, resulting in increased errors. Therefore, it is of great significance to study the performance of SF6 relay at extreme temperatures.
The inspection device of the SF6 relay is mainly divided into two parts, which are the constant temperature control box and the calibration platform. The operation of the two needs to be carried out in an extreme temperature environment.
The high and low temperature control box can be used to control the temperature between -40°C and 160°C, and then the SF6 relay can be used for accurate inspection.
In order to connect the data, the control box and the platform must be used together, so that the pressure and temperature of the air source between them can be effectively adjusted.
The calibration software will automatically read and store the test value according to the temperature, including the contact action value and the contact return value.
Since there is a certain curve relationship between the pressure value and the temperature, the change of the relationship in the two can be used to judge whether the action value of the SF6 relay is qualified.
1. The equipment has an SF6 gas filling system, which can help the density relay test sample to carry out gas replenishment conveniently and quickly.
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 gas density relays, the role of these two sensors is to measure the values of different types of relays.
3. Compared with SF6 gas detection, the traditional density relay calibrator has a certain measurement error, so the SF6 gas detection is generally used in the actual operation to improve detection efficiency and accuracy.
1. Ensure the accuracy of reading pressure values
In the process of testing, it was found that the value on the SF6 relay did not match the pressure value collected by the system, and there was a considerable error.
Cause of the problem:
First, because the thickness of the pipeline is prone to large changes, the pressure transmission is relatively unstable, which makes the instantaneous pressure unbalanced;
Second, if in low temperature environment, the pressure indication values of the SF6 relay at the near and far ends of the air supply port do not match, and the near end is larger than the far end, it means the distance between the installation position of the four density relays and the position of the air supply port are not equal;
Third, because the position of the density relay is far away from the position of the pressure sensor, the phenomenon that the reading value is not timely will occur.
In response to these three problems, specific improvements can be made to the pipeline, such as: replacing the mounting frame of the SF6 relay, and adjusting the position to keep the distance between the relay position and the air supply port position equal;
Adjust the installation position of the pressure sensor and change it near the proximal end of the relay to improve the timeliness and accuracy of reading the pressure value.
2. Ensure the accuracy of reading temperature values
Adjust the temperature in the high and low constant temperature control box, control it at -40 ℃, and then put the SF6 relay into it for two hours before testing.
During the inspection, it was found that the temperature read by the system after adjustment was -33°C instead of -40°C. The reason for this phenomenon is that SF6 gas will liquefy as the pressure rises.
Then a certain amount of heat is released to make the test temperature near the gas path higher than the adjustment temperature. In order to make the actual ambient temperature reach -40°C, the position of the temperature sensor should be adjusted to keep it away from the gas path.