Apex Compact Switchgear

Apex compact switchgear chambers are designed for operation in electrical units of three-phase alternating current with frequency of 50 and 60 Hz, at voltage of 6 and 10 kV for the system with a neutral point insulated or grounded through an arc-suppression coil. Apex compact switchgear are made for installation in radial, trunk and loop distribution cable networks. They perform connection, power supply and safety functions.

The cubicle is an assembled metal structure with components connected with each other using rivets. All metal parts of housing of Apex compact switchgear are manufactured from a bent section with thicknesses of at least 2 mm. Gears and attachments of the main and auxiliary circuits are inside the housing. Cubicle service conditions is single-sided.

For the safety of maintenance and accident containment the case is divided into isolated compartments.

The cubicle consists of three compartments:

• a relay compartment;
• a busbar and switching unit compartment;
• cable compartment.

From the front the access to the compartments is limited with doors of special design. Each compartment door is also equipped with a locking system connected to the switching unit.

Busbar and switching unit compartment

The switching unit compartment comprises a switching unit. Busbars are put into a solid shielded insulation and do not contact with the environment. This compartment is completely isolated from other compartments, including using a unit that performs the function of a mechanical baffle between the main compartments.

The unit has three main configurations:

• - a vacuum power circuit breaker integrated with a three-position disconnector-earthing device;
• - a vacuum load break switch integrated with a three-position disconnector-earthing device;
• - a three-position disconnector-earthing device.

Despite the fact that the use of an insulated bus system guarantees the highest level of reliability and safety, the busbar and switching unit compartment is equipped with an overpressure relief valve. The overpressure relief valve, located in the upper part of the cubicle provides release of arc combustion products to a place that is safe for operations personnel.

The cubicle front has a unit drive, closed with a front control panel. The panel is made of a steel sheet with thickness of 2 mm and with powder paint coating. The panel displays a mimic diagram corresponding to the unit configuration, openings for the controls and a watch window to control the grounding blades position.

Cable connections compartment

Cable compartment is designed for arrangement, fixation and connection of cables. It can contain the following equipment:

• current transformers (in cubicles with width of 650 mm those are cast and support-type, in cubicles with width of 400 mm those are bus-type);
• voltage transformers (in cubicles with width of 650 mm);
• zero-sequence current transformers;
• voltage monitors capacitive divider;
• surge suppressor;
• cable inlets with hoses for power cables fixing;
• ground bus system.

In cubicles with a width of 650 mm, the cable is connected using a bolted connection or a plug connection. In cubicles with a width of 400 mm it is connected only with a plug connection. By request installation of a short-circuit current monitor can be installed.

The combustion products and gases in case of a short circuit arc are discharged from the cable compartment through the channel in the rear of the cubicles. In the upper part the channel is covered with a relief valve.

The design of the cable compartment door is arc-resistant and is equipped with a lock that allows to open the door only when the earthing device is on.

The bottom of the cable compartment is equipped with inlets for the power cable passage and with special clamps for attaching it, as well as with brackets for attaching zero-sequence current transformers.

Each cubicle has its own internal earthing loop and it is connected to the external earthing loop with a bolted connection.

Secondary switching compartment

Relay protection and emergency automation compartment comprises the following equipment of the secondary circuits: microprocessing protection units, circuit breakers, relays, terminal rows, signaling equipment, etc. A microprocessing protection unit, measuring instruments and metering devices, push-button control stations and light-signaling equipment are usually located on the compartment door. Cubicles of auxiliary circuits are interconnected using connectors located in the cable conduit in the relay compartment.