Product details

Structural and technical requirements

The load switch in the box type switchgear adopts a three position SF6 load switch, and the electrical life of the SF6 load switch should meet the E3 level requirement: the electrical life of the circuit breaker should meet the E2 level requirement.

In PT cabinets, metering cabinets, and other switch cabinets that use air insulation, anti condensation measures should be taken (condensation controllers should be installed inside the cabinets), such as installing resistance heaters (with control switches).

The relative pressure of SF6 in the gas package of the unit type SF6 ring main unit should not exceed 1.4 bar. The entire inflatable shell should meet the requirements of the "closed pressure system" specified in IEC 60298, with an annual leakage rate of no more than 1%, maintenance free for 30 years, and no need for re inflation. The pressure of the gas inside the SF6 chamber can be monitored through an SF6 pressure gauge.

The rated current of the fuse should be matched with the load, and the parameters of the fuse are: rated voltage of 12kV, rated breaking current (effective value) of 63kA. The switch used for transformer protection should be able to fuse and trip, as well as easily achieve electric tripping.

The box type switchgear should have complete five prevention interlocking functions.

Through the control of the mechanism interlocking device, the operation achieves the following five prevention interlocking functions:

1. Prevent accidental opening and closing of circuit breakers (load switches);

2. Prevent load on/off isolating switches;

3. Prevent live hanging (closing) of grounding wires (grounding switches);

4. Prevent closing circuit breakers (load switches, isolating switches) with grounding wires (grounding switches);

◆>Prevent accidental entry into electrified compartments.

◆ Adopting a fully enclosed structure, the switchgear mainly consists of compartments such as gas chambers, cable chambers, and mechanism chambers (secondary chambers). The distance from the cable joint to the cable entry point (hole or fixing clamp) is ≥ 370mm, and the inner sleeve and supporting insulation parts are made of epoxy resin material, with a creepage distance of ≥ 20mm/kV. The interconnection adopts copper busbar, and the grounding busbar adopts copper busbar. The selection of cross-section should meet the requirements of GB3906.

The mechanism box panel is equipped with a live indicator with electrical verification function, which is easy to replace and can be externally connected to a secondary phase analyzer.

The primary circuit simulation sign of the box type switchgear is clearly marked.

High voltage electrical components installed internally, such as SF6 load switches, circuit breakers, transformers, lightning arresters, etc., should have durable and clear nameplates, which should be installed during operation or inspection

A location that is easy to observe during repair.

The opening and closing station is equipped with a secondary room or control box, which has a secondary circuit that matches the operating mechanism. It can be configured with a manual/electric operating mechanism and reserved with electric operation function, remote control and remote signaling interfaces to meet the needs of remote monitoring. It should also have a short circuit fault indicator to meet the requirements of phase to phase short circuit and single-phase fault grounding indication, and have switch output function. Ring Main Unit

The internal terminal requires the use of dust-proof and flame-retardant products. The secondary wire section of CT is a copper core with a cross-sectional area of 2.5 square millimeters, and a current testing box is installed in the circuit. The voltage and control wires have a cross-sectional area of 1.5 square millimeters with a copper core.

The lower cabinet door is equipped with an observation window and made of flame-retardant transparent material.

The installation and maintenance of cables in front of the cabinet where the box type switch is located can be installed against the wall.

The load switch adopts a three position structure, with intuitive position indication on the front panel. The grounding switch and load switch of the three position switch, as well as the isolation switch, have separate operating handle sockets.

The structure of the box type switchgear has the function of preventing personal injury to operators in the event of internal faults and arcing: the compartments are equipped with metal partitions to prevent the expansion of accidents; The chamber has a pressure release area; cupboard

There is a pressure relief plate at the back of the body.

The installation dimensions of load switches and operating mechanisms are uniform, and the same components, vulnerable parts, and spare parts are interchangeable.

The air chamber of the box type opening and closing station is welded with 3mm 304 stainless steel plate, and the cabinet body is made of aluminum zinc coated steel plate (except for ventilation, exhaust ports, and observation windows), with a steel plate thickness of not less than 2mm and sufficient mechanical and fire resistance strength.

All components of the live main circuit are installed in the air chamber, and the protection level of the air chamber should meet the requirements of IP67; The cabinet meets the requirements of IP4X.

The position of the lifting rings (one on each side) used for lifting should be set reasonably, and the switch equipment in the suspension should be kept horizontal. There should be no frictional contact between the lifting chain and any components to avoid lifting

Scratching the spray coating on the surface of the box during installation.

A dedicated grounding busbar should be installed along the entire length of the box type switchgear. If it is made of copper, its current density should not exceed the specified grounding fault

200A/mm”, But the small cross-section shall not be less than 30mm ". The grounding conductor should not have a fixed connection terminal connected to the grounding grid and should have a clear grounding mark. If the grounding conductor is not made of copper, it should also meet the requirements of peak withstand current and short-time withstand current specified on the nameplate.

The contact area of the shell grounding point should meet the requirements, and the diameter of the grounding screw should not be less than 12mm. The grounding point should be marked with the word "grounding" or other grounding symbols.

The main busbar in the air chamber is made of copper material, and the cross-sectional area of the branch leads in the busbar segmented cabinet is the same as that of the main busbar; The outer surface of the main busbar and branch busbar (including connecting parts) shall be directly insulated with organic insulation, which means that there shall be no exposed parts of the busbar in the busbar compartment and cable compartment (except for cable connection terminals).

Other requirements for SF6 load switch:

1. The arc extinguishing medium and insulation medium of the load switch are SF6 gas;

2. Each independent SF6 gas chamber should generally be equipped with a device that can display the internal air pressure, which should be able to clearly display the pressure range for safe operation of the equipment.