MV Switchgear 10 kV

Depending on the needs and the nature of the load, this switchgear is used for distributing and metering consumed electrical energy and for connecting the transformer cell to the MV network.

The most common MV switchgear configuration is two line cells and a transformer cell for distribution substations, or two line cells, a metering cell and a transformer cell for industrial substations.

Line (network) cell

Dimensions (W × H × D): 600 × 1900 × 750 mm
Switch pole spacing: 210 mm
Type test: “Nikola Tesla” Institute

In MV switchgear this cell is used for distributing electrical energy. A typical configuration contains at least two such cells, or more if required.

It is made of welded profiles that form the basic frame of the cell. The frame primarily carries the load-break switch and ensures safe operation without any risk of the structure twisting or bending.

It is equipped with a latest-generation compression-type MV load-break switch with a pole spacing of 210 mm, which guarantees the required dielectric strength. The poles are fully cast in epoxy resin and only the moving contact is visible through a transparent cover, so the open and closed positions can be checked visually.

The switch is fitted with earthing blades interlocked with the main contacts: it can be earthed only when the main contacts are open (switch off).

It is operated from the front with a special lever; switching on and off is done by rotating the lever. There is visual indication of the switch position and of the earthing blades, a mechanical interlock between the main contacts and the earthing blades, and the cell door cannot be opened while the switch is closed and not earthed.

This provides maximum protection for the operator. Additional protection comes from the thickness of the sheet-metal partitions, the design of the switch itself, which is almost fully enclosed, and the insulating plates and epoxy bushings where the busbar system passes from cell to cell. As a result, an arc does not spread from one cell to the next.

The cell is also fitted with a pressure-relief flap for venting gases in the event of an arc. The bottom is closed with galvanised steel sheet with rubber cable glands, which prevents rodents from entering the cell.

The structure is free-standing, so it can be installed against a wall or anywhere in the substation. The type test was carried out at the “Nikola Tesla” Institute in Belgrade.

Metering cell

Dimensions (W × H × D): 600 × 1900 × 750 mm
Instrument transformers: 12 kV
Busbars: Cu 30 × 5 mm

In MV switchgear this cell is used for metering consumed electrical energy at medium voltage in indoor installations, which also captures the transformation losses.

It is made of welded profiles that form the basic frame, carry the instrument transformers and the MV fuse bases, and ensure safe operation without any risk of the structure twisting or bending.

It is equipped with the appropriate number of 12 kV current and voltage transformers, depending on whether two-element or three-element metering is used.

The structural profiles, the cell partitions and the door are made of 2 mm cold-rolled steel sheet. The partition in the upper part of the cell, which holds the bushings for the 30 × 5 mm copper busbars, is made of 6 mm pertinax, which further increases the dielectric strength of the equipment. For safety reasons the flap opens from the cell floor towards the rear, so any gases are directed upwards.

The cell also has built-in holders for the MV fuse links that protect the voltage transformers.

The cell door can be opened only by authorised staff of the distribution system operator, as it is always sealed by the responsible distribution company.

The cell has been type-tested at the “Nikola Tesla” Institute, an accredited national laboratory.