400 A ATS panel: automatic mains-to-generator transfer for an industrial site

The task

The site has a diesel generator as its standby source. The point was never simply to have the generator — it was to make the load move onto it without a human in the loop, and back again once the mains recovers.

The requirements that shaped the design:

• Two independent 400 A incomers — from the switchboard and from the generator, with mechanical and electrical interlocking: the two sources must never meet.
• Automation, not a manual changeover switch — transfer without an operator, triggered by loss of mains or by its parameters drifting out of tolerance.
• Monitoring supply quality, not just its presence — phase imbalance and a broken neutral must be detected the same way as a complete outage.
• Metering kept separate — the metering section sits in its own IP54 enclosure, suitable for a dusty room.

The solution

We built two panels that work as a pair.

1. The АВР-200-400 panel — the heart of the scheme:

• Two 400 A moulded-case circuit breakers with a 36 kA breaking capacity and adjustable trip units.
• Two motor operators on those breakers — this is what makes the transfer automatic: the breaker opens and closes on a command from the logic, not by hand.
• Two three-phase voltage and phase-monitoring relays — watching each incomer: voltage, imbalance, phase sequence and phase loss.
• Interposing relays for the transfer logic and signalling.
• Busbars with phase colour marking and a separate PEN bar.
• Source indication on the door: two lamps labelled "Від шафи ГРЩ" (from the switchboard) and "Від шафи АВ ДГУ" (from the generator ATS). The operator sees which source is feeding the site without opening the panel.

2. The ПР11-3045 IP54 panel — a 400 A metering section with a circuit breaker in a dust- and moisture-protected enclosure.

Both panels carry a factory nameplate and a QR code: ratings and serial number can be read on site. The series product card: ATS panel. For designers: the typical solutions "0.4 kV ATS" and "0.4 kV ATS with two incomers".

Figures (from the passports)

АВР-200-400 panel, serial No. 174139

ATS bill of supply (from the passport)

ПР11-3045-IP54-У1 metering panel, serial No. 174140

What this delivers on site

• Transfer to the generator with no operator — the logic detects loss or degradation of the mains and starts the transfer itself.
• Protection against a bad supply, not only a missing one — the phase-monitoring relay catches imbalance and phase loss, which are often more damaging to equipment than a clean outage.
• The two sources can never meet — the incomers are interlocked.
• Status readable from the corridor — labelled lamps on the door instead of guesswork.

Photo report: from frame to the finished panel

We'll build an ATS panel to your diagram

Send us the single-line diagram and the type of your standby source — we'll size the panel to your current, with motor operators, phase monitoring and metering. From the diagram to factory testing and a passport.