Indoor switchgears

Indoor switchgear is a block-module with electrical switchgear equipment of 6(10) or 0.4 kV placed inside it. Medium voltage 6 (10) kV switchgear is designed on the basis of “Rial” KSO chambers. Low-voltage switchgear is a system of low-voltage cabinets of own needs, lighting, heating, ventilating, fire and burglar alarm and other. The main technical features of indoor switchgear are given in the table below.

Parameter designation


Rated voltage, kV

6 (10)

Maximum operational voltage (linear), kV

7.2 (12)

Short time withstand current at the side of H, during 1 s, kA


Peak withstand current at the side of HV, kA



Indoor switchgears are designed for operation in the following climate conditions:

-operational ambient air temperature: from -60 0C till +40 0C;

-relative humidity: up to 80% (t = +200C);

-environment – industrial atmosphere, type 2 according to GOST 15150-69;

-altitude above sea level: up to 1000 m.

Equipment of indoor switchgear 6 (10) kV

The indoor switchgear of block-modular execution is applied with 6 (10) kV “Rial” KSO chambers (produced by JSC “Nevsky zavod “Electroshchit”). KSO chambers set may consist of inlet chambers, outgoing lines chambers, chambers of transformer protection, sectional chamber and other, depending on customer’s demand.

Own needs system of complete substations and indoor switchgears

To provide the own needs system the switchgear heated section is equipped with switchboard of own needs (SChSN). The switchboard of own needs is powered by: low-voltage switchgear in KTP, auxiliary transformer in the indoor switchgear or by external power source 380/220 V.

If the switchgear breakers are supplied with digital relay protection and reserve switching device, then the control circuits of the own needs switchboard are equipped with an uninterruptable power supply.

Complete substations and indoor switchgears connection

Complete substations and indoor switchgears connection is performed with cables. There are three ways of cables connection: aerial lead-in, lead-in through side apertures or through apertures in the floor. It is possible to supply complete substation and indoor switchgear as a unit, when they are installed in separate modules. In that case the connection of complete substation and indoor switchgear is performed with high-voltage jumper cables (they are shipped by manufacturing plant).

The connection of step-up substations is fulfilled with external cable connection through busbar inlet in the side wall of block-module.

Aerial lead-in: the connection is realized through the cross bar on the roof of block-module; then to the facility of high-voltage lead-in with the help of jumper cable.

Cable connection at the 6/10 kV side, as well as at the 0.4 kV side, is fulfilled through seal boards, placed in the technological apertures of the side walls or the floor.

Automatic power supply is connected with external low-voltage jumper cables and bus inputs on the side wall of the block-module.