10 kV switching station on КСО-Е cells: four bays with microprocessor protection (Chornomorsk)

The task

The site needed a small but complete 10 kV switching station: four bays, one of them a standby supply.

The particular challenge is scale. With four cells rather than seventeen, each one carries more functions: the incomer holds metering, protection and voltage measurement at once. Hence the requirements:

• metering and protection from a single set of current transformers — rather than separate CTs per task inside a cramped cell;
• an identical operator interface across all four cells despite their different roles;
• visible position of the switching devices — on a site without permanent staff, the station's state has to be readable from the front.

The solution

We built the station on four КСО-Е-393В single-side-maintenance cells — a design that mounts against a wall and is serviced from the front only.

• Switching. A 10 kV / 630 A vacuum switching module with a solenoid operating mechanism. 10 kV / 630 A disconnectors with manual drives, labelled right on the front — "load-break switch drive", "earthing switch drive" — so the operator is never guessing which handle is which.
• Metering and protection from one CT set. Current transformers rated 300/5 A with two secondary windings: class 0.5S for metering and 10P for protection. One set of devices, two duties, without duplication in a tight cell.
• Voltage measurement. A 10 kV voltage transformer in its own compartment, with HV fuses on post insulators.
• Protection. A РС83 microprocessor protection and automation relay on every cell front, in Ukrainian, with a display and identical control logic across the row.
• Surge protection — arresters on the 10 kV side and on the auxiliary circuits.
• Control circuit supply — a dedicated single-phase dry transformer 220/110 V.
• Front-panel instruments — a 300/5 A ammeter and a 300 V voltmeter: current and voltage visible without the inspector's own meter.
• Documentation. Each of the 4 cells has its own factory passport with serial number and a full bill of components.

The third incomer comes from a diesel generator. When the grid voltage disappears, for a site like this it is not "the lights go out" but the process stops. That is why the station's scheme includes a separate, third bay — fed from a diesel generator. It is not "a spare hole for a cable later" but a full cell: its own vacuum switching, disconnectors and a microprocessor protection and automation relay — the same level as on the main incomers. The bay's purpose is labelled on the front panel, so during switching operations it is visible which incomer the staff are working with.

For designers: the typical solutions "10 kV switching station on КСО cells" and "КСО protection schemes".

Figures (from the passports)

КСО-Е-393В single-side-maintenance switchgear cells, 2026

Serial Nos. 174119 (variant 21В), 174120 (17В), 174121 and 174122 (04) · passports Э-25-358 ПС · Odesa

Incomer cell contents (from the bill of supply, passport No. 174119)

Why four cells is not simply "less"

In a large station the functions are spread across dedicated cells: a metering cell, feeder cells, a separate bus-section cell — as in our case study of the 17-cell station in Uman. With four bays that is not an option — the functions have to share one 800 mm wide body: metering, protection, voltage measurement, control-circuit supply. This is exactly where design-to-scheme matters rather than picking cells from a catalogue: one CT set serving two duties, compartments laid out around the actual cable entries, coordinated settings on identical relays.

Photo report: the station and its documentary nameplates

We'll size a switching station for your number of bays

Send us the single-line diagram — we'll select the cell variants, the ratings and the equipment. From four cells to a complete switching station, with a passport for every cubicle.