K-301 “Volga” Medium-Voltage Switchgear 35 kV

KRU K-301 “Volga” is a 35 kV modular medium-voltage switchgear line designed for transmission and industrial power systems where reliable clearing of short-circuit currents up to 31.5 kA is required in networks with isolated or compensated neutral. The panels receive and distribute three-phase 50 Hz power, forming modular line-ups in indoor substations, factory-built modular substations, and plant main substations. Each cubicle is a welded/riveted frame made of 2 mm galvanized sheet, optionally Cr III passivated - corrosion resistance > 1000 h in salt-spray testing (ISO 9227). External panels are coated with polyester powder, RAL 7035.

The enclosure is divided into four isolated zones: busbar, withdrawable circuit-breaker, cable, and relay/control compartments. Each has its own pressure-relief duct with rupture membranes that vent hot gases strictly upwards, protecting personnel at the front. Internal-arc tests per IEC 62271-200 confirmed class IAC AFL 31.5 kA 1 s; external surface temperatures did not exceed 240 °C and doors remained operable. A seismic option is available certified for 8-degree MSK-64 with reinforced bracing and M20 anchor bolts.

The withdrawable unit is equipped with a 40.5 kV vacuum circuit-breaker (M2/E2/C2) from VD4 (ABB), SION (Siemens), Susol (LS) or equivalents. The cassette travels on dual channel rails; the “in-service → test” operation is completed in 90 s with a single handle. A motor operator (option) enables remote racking and switching via SCADA. The six-pole primary contact set uses bushing insulators with copper studs; transition resistance ≤ 20 µΩ verified by type test reports.

The cable compartment accommodates a 40 kA earthing switch, 0.2S-class current transformers, ZnO surge arresters, and VDS capacitive voltage indicators for non-contact voltage presence. Busbars are copper: 1 x 10 x 80 mm (up to 1600 A) or a stack 2 x 10 x 80 mm (2000-2500 A); joints use mushroom-head bolts and damping pads to reduce short-circuit forces and magnetostriction. All secondary wiring runs in shielded ducts; a mounting frame is prepared for IEC 61850 Ed.2 IEDs and an LC-to-SC 24-fiber optical patch panel.

Standards and references:

IEC 62271-200 (up to 52 kV) - IAC AFL 31.5 kA 1 s;
IEC 62271-100 - 40.5 kV circuit-breakers, class M2/E2/C2;
IEC 62271-102 - earthing switches, mechanical endurance 5000 cycles;
IEC 60071-1 - LI 170 kV / SI 95 kV;
EN/IEC 60721-3-3 - environmental conditions (indoor); IEC 60529 - IP 31 (option IP 41/IP 54).

Scope of application

K-301 “Volga” is installed in permanent and fast-deployable indoor MV switchgear:

110/35/6 kV transmission and distribution substations in the oil & gas sector;
plant main substations: metallurgy, cement, and chemical industries;
auxiliary switchboards of TPP and GTES units rated 100-300 MW;
factory-built modular substations for renewable generation and data centers.

Technical data

Rated voltage, kV	35
Maximum system voltage, kV	42
Rated current of main circuits, A	630; 1250; 1600; 2000; 2500
Rated busbar current, A	1600; 2000; 2500
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 (indoor)
Degree of protection (IP)	IP 31 (IEC 60529)
Overall dimensions, mm - width - depth - height	1200 2250 2500