Secondary systems for a 35 kV switching station: protection cabinet, load-shedding cabinet and instrument-transformer terminal boxes

The task

Secondary circuits are what you never see in a photograph of a finished substation, yet they decide whether the protection operates at all. The customer needed:

• A line protection and control cabinet (РШ) — the brain of the bay: relays, terminals and the circuit-breaker control circuits.
• An under-frequency load-shedding cabinet (АЧР) — when the system frequency drops it disconnects predefined loads so the wider system does not collapse. A mandatory element for any site operating within the power system.
• Two terminal boxes — ЯЗТН for voltage-transformer circuits and ЯЗТС for current-transformer circuits. The measuring circuits run through them: this is where secondary wiring is tested, short-circuited and opened without shutting the site down.
• An outdoor-rated build. IP54 on all four cabinets: the site is of the open type and the cabinets do not stand in a heated room.

The solution

All four cabinets were built as one batch, to a single secondary-wiring standard.

• One wiring standard throughout. Identical terminal rows with every conductor marked, identical trunking, identical colour coding. A crew that maintains one cabinet opens the next and finds the same logic.
• The protection cabinet. The heaviest item — 200 kg in a 1280 × 1000 × 520 mm enclosure: relays, terminals, auxiliary supply breakers and terminal rows inside.
• The load-shedding cabinet as a separate product rather than "a function inside the protection cabinet": 1200 × 600 × 360 mm, with an instrument and controls on the door.
• The VT and CT terminal boxes — the same 1200 × 600 × 360 mm envelope, different contents: current-transformer circuits with shorting facilities in one, protected voltage circuits in the other.
• Sealing and climate. IP54 — gasketed doors and bottom cable entry through gland plates.
• A passport and a rating plate for every cabinet — serial numbers 174109–174112.

Figures (from the passports)

The order — four LV assemblies:

Common parameters:

The series product card: Protection and control cabinets. For design engineers: the standard solution Protection schemes for КСО cubicles.

Photo report from production

We will build to your diagram

We will build the secondary systems to your protection scheme. Protection and control cabinets, load-shedding cabinets, VT and CT terminal boxes, auxiliary supply cabinets — to your secondary wiring diagram, with every conductor marked and a passport for each cabinet. Send the diagram and an engineer will size the package. → [enquiry form]