Functions of metering switch manufacturers' products

The metering switch manufacturer is a device for changing the operation mode in the power system, switching on and off load currents, capacitive load currents such as unloaded long lines or capacitor banks, and switching off inductive small load currents such as unloaded transformers or high voltage motors.

In combination with relay protection, it can quickly remove faults from the grid when they occur, thus reducing damage to power equipment and improving the stability of the grid.

In conjunction with automatic reclosing, it can ensure the timely removal of faults and restoration of power supply in the event of a transient fault in the grid, improving the reliability of power supply to the grid.

Oil metering switch manufacturer: is a metering switch whose contacts are interrupted in transformer oil and uses transformer oil as the interrupting medium. The oil is only used as an interrupting medium and the oil consumption is low, which is called an oil-free metering switch. The oil is also used as an insulating medium and consumes a large amount of oil, known as multi-oil metering switches.

Air switch: A metering switch that uses high pressure air to blow an arc. The general blowing pressure is in the range of 10-40 atmospheres and has been largely eliminated due to its complex structure.

Vacuum metering switch: a metering switch whose contacts are interrupted and closed in a vacuum, using the vacuum as the insulating medium and arc extinguishing medium. The vacuum level of the vacuum metering switch should be above 0.0133 Pa

Solid gas producing metering switch: a metering switch that uses the gas decomposed by solid gas producing substances under the high temperature of the arc to extinguish the arc. Due to the low arc extinguishing capacity, it is generally used only as a load switch.

Sulphur hexafluoride metering switch: A metering switch that uses high pressure sulphur hexafluoride gas to blow the arc. It is widely used due to its good arc extinguishing properties.

SF6 gas characteristics: Insulation strength is 2-3 times higher than air under a uniform electric field and the breaking capacity is 100 times higher than air. However, SF6 gas is produced in very small quantities under the action of an electric arc. SF4 combines with metal contacts and moisture in SF6 gas to produce HF and SOF2. SF4, HF and SOF2 are toxic and very corrosive to metals and insulation materials.

Classification of metering switches (by operating mechanism)

Electromagnetic operating mechanism: uses the electromagnetic force of the closing coil to close the switch, while the breaking spring stores energy. It is characterised by a high closing current, which can reach several tens to several hundred amps. Therefore, the closing circuit cannot be directly connected by the contacts of the control switch and a closing contactor must be used. Suitable for metering switches up to 35 kV.

Spring-operated mechanism: The stored energy closing spring is used for closing, and the closing spring releases energy to store energy for the breaking spring. Now widely used.

Hydraulic operating mechanism: compressed N2 (disc spring) is used as the energy source and hydraulic oil is used as the transmission medium for opening and closing. Widely used for 110kV and above oil-free and SF6 metering switches.

Pneumatic operating mechanism: using compressed air as kinetic energy to push the piston to achieve opening and closing. Fitted with air compression equipment, the brake divides the gate by compressed air for spring energy storage, and the gate divides by spring.

Metering switch parameters

Rated breaking current: The maximum current that can be safely broken by the metering switch at the rated voltage.

Rated closing current: the maximum current that the metering switch can reliably connect. Generally 1.82 (2.5) times the rated breaking current is taken.

Rated breaking capacity: is a parameter that characterizes the breaking capacity of the metering switch and is calculated from the breaking current. For three-phase metering switches, the rated breaking capacity formula is: rated breaking capacity = 3 rated breaking current rated line voltage.

Rated short-term withstand (thermally stable) current: the ability of the metering switch to withstand the thermal effects of short-circuit current. It is the effective value of the current that the metering switch can carry in the closed position within the specified time, numerically equal to the rated short-circuit breaking current of the metering switch.

Rated peak withstand (dynamic stability) current: The peak current of the first half wave of the rated short-term withstand current that the metering switch can carry in the closed position. It is equal to the rated short-circuit closing current.

Structure of the metering switch

The disconnection section 3360 comprises the conductive and contact system and