The VM-4 series brings metal-clad switchgear technology to the 35 kV class while preserving the compact footprint and serviceability typical of 10 kV bays. The cubicles are intended for receiving and transferring three-phase power at 50 Hz in systems with an isolated or compensated neutral, provide selective interruption of short-circuit currents up to 31.5 kA, and are designed for daily switching duty. The enclosure is made of steel with an additional Aluzinc AZ-150 coating, delivering over 1,000 h corrosion resistance in a salt-spray chamber. Each cubicle is divided into four isolated compartments, each with its own pressure-relief duct and rupture panels: during an internal arc, gases are vented strictly upward, preventing damage to adjacent LV circuits.

The switching device is a withdrawable 40.5 kV vacuum circuit-breaker (class M2/E2/C2) rated for 30,000 O-C operations and short-circuit currents up to 31.5 kA. The truck can be moved to the service and test positions manually; a motor operator is available for remote substations. Polycarbonate-epoxy shutters automatically cover the fixed contacts when the truck is withdrawn, eliminating exposure to live parts. Secondary wiring is routed in shielded metallic raceways; single-point earthing of shields reduces high-frequency interference and simplifies integration of digital IEDs.

Internal arc resistance is type-tested to IAC AFL 31.5 kA 1 s (IEC 62271-200); during testing, the enclosure maintained its geometry and the temperature on external surfaces did not exceed 240 °C. For high-humidity sites (water utilities, port-area switchrooms) IP 41/IP 54 options are available: additional door seals and ventilating air-locks with heaters keep the dew point below -5 °C. For seismic regions, reinforced anchors and braces are applied, qualified to intensity 8 on the MSK-64 scale.

Protection and control devices are installed in a dedicated relay (LV) compartment: IEDs with IEC 61850 Ed.2 support, station-service transformers, and metering modules with DLMS transport. An LC-to-SC optical patch panel enables direct connection to the fiber backbone without field modifications. For brownfield upgrades, a "cross-layout" is available: VM-4 is built to KSO-366 envelope dimensions but with a vacuum CB and modern interlocks, simplifying retrofits without complete busbar dismantling.

Installation convenience is designed-in. All mounting points are accessible from the front; cable terminations are set at 900 mm above floor level to speed stripping and torque inspection. The spare-parts kit includes heat-shrink lugs, spare springs for the earthing switch, and diagnostic fittings for partial-discharge measurements without taking equipment out of service. The availability coefficient K_gt over a two-year pilot operation was 0.9978, comparable to best-in-class imported 36 kV products.

Standards and testing:

• IEC 62271-200 (up to 52 kV) - type tests to IAC AFL 31.5 kA 1 s;
• IEC 62271-100 - 40.5 kV vacuum circuit-breakers, class M2/E2/C2;
• IEC 62271-102 - earthing switches, mechanical endurance 5,000 cycles;
• IEC 60071-1 - insulation coordination, LI 170 kV / SI 95 kV;
• EN/IEC 60721-3-3 - environmental conditions (replaces GOST 15150 U3/T2); IEC 60529 - IP 31 standard, IP 54 optional.

Applications

VM-4 cubicles are installed in permanent indoor switchrooms or factory-built modular E-houses and are effective in:

• package substations for oil & gas clusters and gas distribution stations;
• station-service boards of TPPs, GTUs, and cogeneration plants;
• industrial substations (metallurgy, chemical, food plants);
• utility network nodes at 35 kV for long overhead-line backup and RES interconnection;
• switchgear for municipal infrastructure, data centers, and airports.

Technical data

Documentation for manufacturing KRU VM-4

Tender package. Questionnaires, single-line diagrams, and technical descriptions tailored to procurement requirements.

Working drawings & 3-D models. Layouts, BOMs, secondary schematics, and cable schedules.

Contract manufacturing of assemblies. We can place fabrication of the enclosure, doors, and shutter mechanism with partner plants when needed.

Adaptation to existing equipment. We design equivalent bays for interfacing with installed busbars.

Why work with us

Lean teams. Documentation is clear for a mid-level engineer.

Serial launch without prototypes. Proven modules reduce risk.

24/7 support. Consulting on fabrication, assembly, and commissioning of VM-4.

Questions? Write to: inbox@proekt-energo.com

PDF - VM-4 Technical Information