10 kV КСО switchgear retrofit: new internals in the existing cubicles — no civil works

The task

The site ran a 10 kV switching station built on КСО cubicles. The equipment had reached the end of its service life: electromechanical protection with no event recording and no communications; instrument transformers past their rated life.

Replacing the station outright would have meant dismantling the cubicles, civil works and a long outage. That did not suit the client. The job was to renew the internals while keeping what still works — the cubicle steelwork and the existing layout.

The solution

We performed a retrofit: everything that governs the operation and safety of the station was replaced, and everything without a service-life constraint was kept.

• Replaced. Cubicle doors with new front panels, microprocessor protection relays, current transformers, control and signalling circuits, secondary wiring, labelling.
• Kept. Cubicle steelwork, row layout, cable entries, the civil structure of the room.
• Protection and automation. One relay type on the incomers and the bus-section breaker, another on feeders and voltage transformers — a single operator interface across the row. Signalling from "Альтра", an intelligent earth-fault protection system, is brought out separately: "Альтра: signal / trip" on the panel.
• Metering. New 400/5 A current transformers with two secondary windings: class 0.5S for metering and 10P for protection.
• Fitting it together. The tightest part of any retrofit is the inter-cubicle wiring: new doors and devices have to meet the geometry of an existing row. That is why the document set includes a calculation of inter-cubicle cable lengths and a cable schedule — cables arrived cut to length rather than as a drum to be trimmed on site.

Scope of work (from the order's document set — 21 drawings)

Plus: control panel (ЩКМ), DC/auxiliary supply cabinet (ШВОТ), cable schedule, layout drawing, requirement questionnaire, inter-cubicle cable length calculation.

Current transformers (from the manufacturer's rating plate)

After the retrofit the cubicles carry our factory nameplate to TU U 27.1-40132794-002:2018.

Why a retrofit rather than a new station

• Shorter outage — work proceeds bay by bay, not on the whole station at once.
• No civil works — foundations, floor, cable basement and room dimensions stay as they are.
• Cheaper than full replacement — you pay for the internals, not for steel and installation all over again.
• Modern protection — microprocessor relays with event recording instead of electromechanics.

If a new station makes better sense — we build КСО-Е cells from scratch. For designers: the typical КСО retrofit solution.

Photo report: the station after the retrofit

We'll cost the retrofit of your switching station

Send us the single-line diagram and the type of your existing cubicles — we'll assess what can stay and what has to be replaced, and give you the scope broken down by bay.