S-410 Medium-Voltage Switchgear 6(10) kV

The S-410 series is a universal metal-clad platform for building 6-10 kV switchgear intended for both urban networks and industrial sites with increased requirements for corrosion resistance and internal-arc withstand. The panels receive, distribute, and switch three-phase AC at 50 / 60 Hz in systems with an isolated or compensated neutral, clearing short-circuit currents up to 31.5 kA. The structure is based on a sheet-steel frame with aluzinc coating AZ150; all joints use blind rivets and 8.8-grade bolts, ensuring the cabinet geometry is retained under dynamic loads up to 6 kN.

The enclosure is divided into four isolated compartments: busbar, withdrawable circuit-breaker, cable, and relay/control. Each compartment has its own pressure-relief channel so that, in the event of an internal arc, hot gases and combustion products are vented upwards without affecting adjacent panels. For humid environments, the cabinets can be supplied to IP 41/IP 54: door perimeters are sealed with EPDM profiles, and ventilation louvres are fitted with G4 filters and 150 W heaters to prevent dew formation.

The switching part is implemented with 12 kV vacuum circuit-breakers from leading brands VD4 (ABB), SION (Siemens), Susol (LS); other manufacturers’ devices may be installed provided interface and mounting dimensions are observed. Racking the cassette to the test position takes ≤ 60 s by a single operator, and a motor operator (option) enables remote operations via SCADA/DCS. A glass-fiber-reinforced polyester shutter mechanism automatically closes the primary socket contacts when the truck is withdrawn, preventing access to live parts.

Secondary wiring is laid in shielded cable ducts with single-point earthing of the screens to reduce HF interference and ensure compatibility with digital protection and control per IEC 61850 Ed.2. A touchscreen HMI is mounted on the relay-compartment door for local monitoring, and an LC-to-SC optical patch panel provides fast integration into the optical backbone. For revenue metering, a dedicated area is provided for meters with DLMS/M-Bus and current transformers with accuracy classes 0.2S / 0.5S.

Cable entry may be from below, above, or via an external hood (options A, B, C). The design allows connection of up to four 3 × 240 mm² power cables; adjacent panels should have fewer cables to maintain convenient routing. A front-access service tray is available from the façade, allowing installers to fix terminations at a height of 900 mm without leaving a single switchgear-aisle bay. Average assembly effort - 11 person-hours; availability factor K_gt after one year of a pilot installation - 0.998.

Standards and routine/type tests:

IEC 62271-200 - IAC AFL 31.5 kA 1 s (internal-arc classification);
IEC 62271-100 - 12 kV circuit-breakers, class M2/E2/C2;
IEC 62271-102 - earthing switches, mechanical endurance 5,000 cycles;
IEC 60071-1 - LI 75 kV / SI 42 kV (standard insulation level);
EN/IEC 60721-3-3 - environmental conditions for indoor installations; IEC 60529 - IP 31 (option IP 41/IP 54).

Scope of supply and applications

KRU S-410 is installed in indoor MV switchgear rooms and factory-built modular substations:

package transformer substations in urban distribution networks;
auxiliary switchgear of TPP/CCPP/HPP units;
industrial substations: metallurgy, chemicals, pulp & paper;
pumping stations, utilities, data centers, agro-clusters.

Technical data

Rated voltage, kV	6; 10
Maximum system voltage, kV	7.2; 12
Rated current of main circuits, A	630; 1250; 1600; 2000; 2500; 3150
Rated busbar current, A	1250; 1600; 2500; 3150
Thermal withstand 3 s, kA	20; 25; 31.5
Dynamic withstand 1 s, kA	51; 64; 81
Maintenance access	two-sided
Insulation level (IEC 60071-1)	standard
Environmental conditions	EN/IEC 60721-3-3
Degree of protection (IP)	IP 31 (IEC 60529)
Overall dimensions, mm - width - depth - height	750; 1125 1400 2300