Ⅰ. Why should SF6 density relay be calibrated?
In the Power Equipment Handover and Preventive Test Regulations, the density relay is required to be calibrated after handover, overhaul and every 3 years. This is because the SF6 density relay may change its performance due to various reasons during long-term operation, or even lose its monitoring function. For example, after a long period of inactivity, the action contacts will be jammed or inflexible, the contactors will be in poor contact, and some will have poor temperature compensation performance. When the ambient temperature changes, it may cause the sf6 density monitor to malfunction. Gas monitoring of operations equipment should include regular calibration of SF6 gas pressure gauges and density relays.
Ⅱ. SF6 density relay calibration process
1. (1) Screw the adjustment handle on the valve device to the "off" position to isolate the density relay from the switch body on the gas path; (2) Unscrew the protective cover of the self-sealing valve on the valve device; (3) Connect one end of the hose to the calibration transition joint, and the other end to the calibrator interface; (4) Connect the calibration transition joint to the self-sealing valve on the valve device, and the air connection is completed; (5) Use the density relay calibrator to check the density relay online without dismantling the meter.
2. The above-mentioned operation process can be fully sealed, which can ensure the safety of operators.
3. The above-mentioned operation process can ensure the seal of the switch without affecting the safe operation of the switch.
Ⅲ. The SF6 density relay cannot be disassembled frequently for calibration
Most of the density relays on SF6 electrical equipment connected to the check valve interface are sealed by setting a sealing ring or gasket, if they are frequently disassembled, their sealing will inevitably be damaged, resulting in the slow air leakage of the equipment and bringing hidden dangers to the safe operation of the entire power system. Therefore, the SF6 density relay cannot be frequently disassembled for calibration, instead, it is recommended to use online calibration without dismantling the meter. When the pressure of the SF6 gas chamber in the high-pressure switch drops, the density relay will give an alarm to remind the staff to refill the equipment. When the gas pressure in the equipment continues to drop and is lower than the blocking pressure, the density relay will issue a blocking command to terminate all activities of the equipment to ensure the safety of the high-voltage switch gear and the entire power system.
