Purpose and Application

The VNA-10 series (VNA-10/400; VNA-10/630) load break switches are intended for routine load switching of sections of three-phase AC circuits with rated voltages 6 (10) kV, 50 Hz, as well as for safe earthing of de-energized sections using built-in earthing blades. The device belongs to the class of medium-voltage switching equipment with a self-generated gas (auto-expansion) arc-quenching system, providing reliable interruption of load currents and transformer magnetizing currents while maintaining compact dimensions and a moderate total cost of ownership.

Typical applications: prefabricated transformer substations (KTP), unit-type cubicles (KSO), metal-clad switchgear (KRU) and distribution points at 6–10 kV. In indoor (ZRU) and metal-clad (KRU) switchgear bays, VNA-10 load break switches are used for bus sectioning, connection/disconnection of outgoing feeders, feeder back-up, disconnection of power transformers (often as an “LBS + medium-voltage fuses” solution), and for routine operations in networks of industrial plants, public utilities, mining and oil & gas sites, agricultural facilities and logistics hubs.

Thanks to standardized connection dimensions and left/right-hand drive options, the VNA-10 is equally suitable for new installations and modernization of existing switchgear. When installed in KSO/KRU cabinets, the switch provides a visible isolating gap and clear position indication, simplifying permit-to-work procedures and improving personnel safety. Optional position indication contacts “ON/OFF/EARTHED” enable integration into telecontrol/SCADA systems, DCS and protection & automation (RPA), supporting monitoring and remote service scenarios.

The application scope includes: incoming/sectionalizer bays, outgoing feeders of 6–10 kV cable and overhead lines, transformer bays of distribution substations, process substations at industrial sites, bypass nodes for maintenance periods, as well as facilities with enhanced requirements for robustness and ease of maintenance. Unlike disconnectors, a load break switch is designed for safe load-current switching, shortening switching time, reducing consumer outages and minimizing the need for additional switching devices.

Service Conditions

The VNA-10 load break switch is designed for indoor installation and is manufactured for climatic category U2 per GOST 15150 (location category 2). This implies operation indoors or under a shelter with natural ventilation; the cubicle design must prevent condensation on live parts. Under typical conditions the device operates reliably in the presence of dust, industrial aerosols and temperature fluctuations common to switchgear rooms. For regions with high humidity and sharp daily temperature variations, it is recommended to install space heaters and microclimate control inside the cabinet.

The device is rated for the mechanical and thermal stresses arising during normal load switching, during short-circuit currents within the declared withstand limits (see technical data table), as well as during switching of transformer magnetizing currents and cable charging currents. Applicable for networks with isolated or resonant-earthed (arc-suppression coil) neutrals, and for resistance-earthed systems, provided project requirements and operating manuals are observed.

Cabinet layouts with VNA-10 ensure safe operation during regular switching. Measures against condensation, dust and foreign objects must be implemented, along with organizational safety measures: warning labels, door interlocks, use of padlocks and personal lockout tags within LOTO procedures. For sites subject to increased vibration or shock (e.g., near heavy process equipment), reinforced fastening hardware and a schedule for periodic torque checks of bolted joints are specified.

Technical Data

Design and Construction

The VNA-10 is a three-pole device with a visible isolating gap and a self-generated gas (auto-expansion) arc-quenching system. Main assemblies include: welded base frame (plinth), bushing insulators, fixed and moving main-circuit contacts, bridging current-carrying blades, arc-quenching chambers made of gas-generating polymer material, mounting and adjustment hardware, interlocking mechanism, and provisions for earthing blades with reliable kinematic linkage to the operating mechanism. Contact surfaces are copper-alloy with a hardened coating to ensure low contact resistance and high erosion resistance under repeated operations.

The auto-expansion arc-quenching principle uses gases released from the arc-chute walls as the arc develops. The generated gas displaces and cools the plasma, promotes de-ionization of the contact gap and rapid recovery of dielectric strength. This enables reliable interruption of load currents and limited switching currents without complex extinguishing media. Chamber geometry and contact profiles are optimized to direct the gas flow, reduce wear and minimize pressure in the arc zone.

The switch is equipped with separately mounted operating mechanisms - manual spring-charged (PR-10/PRBD-10) or motor operators for remote control. Left-hand (VNA-L) and right-hand (VNA-P) drive arrangements are available, simplifying alignment with existing bay doors, cable entries and neighboring equipment. The mechanism stores energy prior to operation and releases it rapidly at the switching instant, reducing arcing time and thermal stress on the contacts. For integration into protection/automation and SCADA/DCS, limit micro-switches provide “dry-contact” position signals “ON/OFF/EARTHED”.

For ease of service, the design provides access to the arc-chutes and contact system from the front of the bay with minimal disassembly. Adjustment points have baseline marks; allowable tolerances and tightening torques are specified in the O&M documentation. Connection dimensions and busbar profiles match widely used KSO/KRU solutions; adapter kits are available to interface with non-standard connection planes and phase spacing. For combined use with medium-voltage fuses (PKT/PKN), cable entries and holders are provided within transformer-protection bay designs.

Safety and Interlocks

Personnel safety is ensured by several protection layers. Mechanical interlocks prevent closing of the main circuit with the earthing switch engaged and prevent selection of the “EARTHED” position when the main circuit is closed. Electromechanical locks and door interlocks inhibit cabinet opening when voltage is present or when the device is not latched in a defined position. Provisions are made for padlocks and warning tags during permit-to-work activities. A visible isolating gap and clear position indication on the mechanism panel improve the reliability of state identification.

The supply package and operating documentation specify interlock checks, maintenance intervals and personnel requirements. Position signalling and integration into SCADA/DCS enable remote supervision, preventing erroneous actions during operations. The mechanical strength of insulators, busbars and fasteners is verified during routine and acceptance tests, assuring compliance with electrical and mechanical safety requirements throughout the device life cycle.

Options and Accessories

Standards Compliance

• IEC 62271-103 - medium-voltage load break switches: general requirements and test methods.
• IEC 62271-102 - disconnectors and earthing switches (requirements for earthing assemblies).
• IEC 62271-1 - common specifications for medium-voltage switchgear and controlgear.
• IEC 62271-200 - AC metal-enclosed switchgear and controlgear (1–52 kV); requirements for cubicles housing load break switches.
• EN/IEC 60721-3-3 - environmental conditions for stationary use at weather-protected locations (climatic category for indoor installation).

Engaging Contractors and Partners

We invite switchgear manufacturers, electrical EPCs and installers, SCADA/DCS integrators, service companies and investors interested in localizing production of VNA-10 load break switches. We provide a full cooperation cycle: review of the specification, adaptation of design documentation to your machinery park, selection of materials and components, development of routing sheets and quality-control instructions, personnel training and support for serial production launch. On request we arrange fabrication of assemblies at partner facilities (machining, plating, plastics, stamping) with incoming/in-process control, and perform acceptance tests per the project’s program and procedures.

Documentation Offered

We supply a complete documentation set to manufacture VNA-10/400 and VNA-10/630 at your facility: BOMs, assembly drawings, 3D models, parts lists, lubrication and adjustment charts, electrical and kinematic schematics, installation and interlock-adjustment instructions. Available formats: DWG/DXF (AutoCAD), SLDPRT/SLDASM (SolidWorks), Parasolid (x_t/x_b), STEP, PDF. If required, we will adapt to specific KSO/KRU layouts, verify mechanical interfaces, calculate busbar current loads, and recommend contact pressures and tightening torques. If you do not plan to manufacture certain parts in-house, we will place them with vetted suppliers; your site will handle assembly, adjustment, testing and packing.

Service Life and Maintenance

Mechanical life to first major overhaul - at least 2000 O-C cycles; interval between overhauls - at least 1000 operations. Follow the prescribed maintenance per the O&M manual: visual inspection of assemblies, condition check of arc-chutes, verification of deposition on contact surfaces, insulation cleaning, lubrication of sliding pairs, interlock inspection/adjustment, torque checks of fasteners, and verification of limit switches. To ensure stable performance, observe the tightening torques and contact pressures specified in the technical documentation.

Advantages of Working with Us:

- No need to maintain a large engineering staff: you receive a standardized documentation package suitable for an engineer of average qualification.
- Launch of serial production without a prolonged prototype stage: we use proven solutions and standard units with industrial track record.
- Consulting support at all stages: from procurement of materials and components to commissioning, staff training and acceptance testing with formal protocols.

For additional information on VNA-10 load break switches: inbox@proekt-energo.com

…as is well known, an error made in design leads to tenfold costs in manufacturing and a hundredfold in operation. High-quality documentation and competent cooperation are the key to reliable performance of 6–10 kV distribution networks.

PDF - Download technical information on VNA-10 load break switches.