In the normal operation of the SF6 density relay equipment, the SF6 gas in the electrical equipment will inevitably leak outward, and the moisture outside the electrical equipment will also penetrate into the high-voltage electrical equipment, resulting in a decrease in the density of the SF6 gas and a small water content. Exceeding the standard will bring huge hidden dangers to the safe and stable operation of high-voltage electrical equipment. Because of this, in recent years, SF6 leakage and on-line monitoring of micro-water content in SF6 have received more and more attention.
Doing a good job in online monitoring of SF6 gas density has very important practical significance, because doing a good job of SF6 gas density monitoring is the key to ensuring the safe and stable operation of high-voltage equipment, especially once SF6 high-voltage electrical equipment leaks, the SF6 gas density will inevitably It will decrease accordingly, which will not only cause a gradual decrease in the withstand voltage strength of high-voltage electrical switchgear, but also cause a gradual decrease in the breaking capacity of circuit breaker equipment. Therefore, it is particularly important to do a good job in SF6 gas density monitoring by using the gas density meter.
Generally speaking, when we judge whether high-voltage equipment can meet the requirements of insulation performance or arc extinguishing performance, we often use the gas density indicator to measure the density of SF6 gas and then come to a conclusion. The dielectric strength has a direct effect and influence, that is, the number of molecules of SF6 gas per unit volume. We can use the actual pressure of SF6 gas at 20°C to represent the density value of SF6 gas. Therefore, in order to further improve the safe operation of SF6 gas-insulated equipment, it is necessary to do a good job in real-time monitoring of the density value of SF6 gas.
And through the analysis of test data, we can know that when the density of SF6 gas is constant, there is no relationship between the breakdown strength of SF6 gas and the temperature; and when the pressure of SF6 gas is constant, then the breakdown strength of SF6 gas is will decrease accordingly with increasing temperature. Especially under the premise of a certain density, when the temperature changes, the pressure will also change, and whether this change is caused by air leakage or the effect of temperature, the temperature compensation correction method can be used. Once SF6 gas leaks, the SF6 density relay is bound to issue a prompt according to the actual change of the density value, and then people can take corresponding solutions according to the corresponding prompt, and replenish the gas in time to prevent the insulation performance of electrical equipment from continuously decreasing. In addition, if the SF6 gas leakage is too serious, the SF6 density relay will give a pair of locking contact signals, indicating that the equipment can no longer operate normally.
There are two common temperature compensation or correction methods: the first one is the most common state parameter equation of SF6 gas at present; The relationship between air pressure and temperature is measured and analyzed, and the density of the measured value is compensated to the density value at 20°C.