Analysis of Six Problems Related to SF6 Relay

SF6 gas density relay is also known as SF6 gas density monitor, SF6 relay, SF6 gas density controller, high-precision SF6 gas density monitor, etc.

Sulfur hexafluoride (SF6) is a non-toxic, tasteless, colorless, odorless, non-combustible synthetic gas, with the insulation characteristic and the arc extinguishing ability that the general dielectric does not have, widely used in the world's power industry in high-voltage circuit breakers and transformer equipment. It almost become the first choice of high-voltage, high-voltage circuit breakers and GIS insulation and arc extinguishing medium.

The density of SF6 gas is the main index of the insulation characteristic and arc extinguishing performance of the gas, so the operation regulations of the National Power Company mandate that the density of SF6 gas must be tested regularly before and during the operation of the equipment.

SF6 relay is a pressure relay with temperature compensation function, mainly used in the switchgear in energy industry. It combines pressure measurement and limit switches in one device. The effects of ambient temperature are adjusted through a special compensation system.

1. Why is not the density unit displayed on the SF6 relay dial?

The function of density detection of density meter is realized by equivalent pressure. Specifically, the pressure in the gas chamber is converted into equivalent pressure of 20℃ after temperature compensation.

2. Why is the pointer not in zero position when SF6 relay is not in use sometimes?

SF6 relay is a meter with temperature compensation function. The pointer is not in zero position because the internal compensation plate of the meter compensates according to the ambient temperature.

3. Why is the accuracy level of SF6 relay level 1 or Level 1.5?

The accuracy of the density meter generally refers to the accuracy at the standard temperature (20℃). The accuracy error can be obtained by multiplying the range on the dial by the accuracy level represented by the current meter.

4. Why is the density meter in SF6 relay called absolute pressure gauge?

The shell of density relay is sealed and is not connected with the outside atmosphere, so the accuracy of the meter is not affected by the altitude. We call this type of meter the absolute pressure gauge.

5. How many pairs of contacts can SF6 relay achieve at most?

The maximum number of density relays used in medium voltage is not more than 3 pairs, and that in high voltage equipment is generally not more than 4 pairs.

6. Is the measuring medium of SF6 relay only sulfur hexafluoride?

The measuring medium of SF6 relay can be sulfur hexafluoride, carbon tetrafluoride, or a certain proportion of gas mixture according to the requirements of different customers.

The density of SF6 gas is indirectly represented by the pressure value of SF6 gas after temperature compensation. The density relay works under the rated pressure. When the ambient temperature changes, the pressure of SF6 gas also changes. The temperature compensation device inside the density relay automatically compensates the changed pressure, so that its pressure does not change with the change of temperature.