The single-front medium-voltage switchgear KSO-393 (rated for 6–10 kV) is intended for receiving, distributing, and switching three-phase AC power at 50 Hz in systems with isolated or effectively earthed neutral. The series is designed for indoor air-insulated switchgear (AIS) of packaged transformer substations, for intake/distribution points at industrial facilities, for plant auxiliary switchgear of power stations, for municipal infrastructure, and other power supply systems. The cubicles can be installed both in permanent indoor substations and in rapidly deployable factory-built modular enclosures, which simplifies brownfield modernization and shortens commissioning times.

Purpose and application

Functionally, KSO-393 covers incomer, bus-section, and feeder connections of medium-voltage switchgear. Typical applications include: connection of 6–10 kV power transformers; switching of cable and overhead lines; busbar sectioning with the option of automatic transfer scheme; supply of process loads and plant auxiliaries; measurement, metering, and data transfer to monitoring systems and SCADA/DCS. Unified mating dimensions, transition panels, and coordinated busbar centerlines make it easy to integrate with existing boards during phased reconstruction. For new builds, standard modules allow quick configuration of the switchgear scheme for the required capacity and supply reliability category.

Service conditions

Cubicles are supplied for indoor, temperate, weather-protected locations - environmental category EN/IEC 60721-3-3 (replaces GOST 15150 U3). The design takes into account temperature, humidity, dust, as well as storage and transportation modes. The base degree of enclosure protection is IP20, preventing access to hazardous live parts and ingress of solid objects; local increases of IP in individual compartments are possible by design while maintaining thermal conditions and ventilation. For high-altitude sites, the effect of reduced air pressure on dielectric strength is considered and reflected in insulation clearances and acceptance test methods. For corrosive environments, enhanced coatings and corrosion-protection measures are applied, including galvanized or Al-Zn (Aluzinc) coated steel enclosures.

Layout and construction

The KSO-393 enclosure is available in two variants:
- a welded structural-steel frame with powder-polymer coating, designed for long-term mechanical and environmental durability;
- a bolt/rivet-assembled steel construction with Al-Zn (or Zn) coating on non-welded fasteners, focused on manufacturability and service convenience.

The internal space is divided into functional compartments. The busbar compartment houses main busbars and inter-panel links; the apparatus compartment contains the primary switching device (typically a vacuum circuit-breaker), disconnector, and earthing switch; the cable compartment contains cable terminations, current transformers, post insulators, and fixing hardware; a dedicated low-voltage compartment accommodates protection and control relays, meters, instruments, and marshalling panels. Viewing windows on the front allow visual confirmation of device positions. For maintenance, the cubicle includes internal lighting and a receptacle for a portable lamp.

The design provides rational placement of live parts, insulators, supports, and protective screens so that in plausible fault conditions products of an internal arc or gas release do not impose hazardous loads on personnel and do not cause insulation flashover to adjacent compartments. Required air and creepage distances are provided, along with measures to reduce local heat dissipation in high-current areas (bus joints, cable lugs, transition nodes).

Safety and interlocking

KSO-393 implements a comprehensive set of interlocks preventing hazardous or incorrect actions: blocking disconnector operation with the circuit-breaker closed; blocking closing of the earthing switch with the disconnector closed; blocking disconnector closing when the circuit is earthed; blocking door opening unless the circuit is earthed. Closed-door breaker operation is a fundamental safety principle that minimizes operator risk during any switching. Interlocks are implemented by mechanical, electrical, and, where required, electromagnetic means to ensure the prescribed sequence of operations. Optional arc-flash sensors and high-speed protection devices can be added to reduce incident energy during internal faults.

Versions and options

The KSO-393 series supports a wide set of configurations and options:
- selection of the primary switching device (vacuum circuit-breaker with required current and interrupting ratings; other options by agreement);
- manual and motor operators with remote control, telemetry, and telemetering;
- microprocessor-based protection relays: overcurrent/directional, differential and distance functions, autoreclose and automatic transfer, disturbance recording;
- instrument transformers (CTs/VTs) of required accuracy classes for protection and metering;
- internal arc classification (IAC) options with specified accessibility sides and directed energy relief to safe zones;
- enhanced anti-corrosion coatings, insulation/heaters, temperature monitoring of cable lugs and busbars, partial-discharge monitoring;
- seismic versions, extended spare-parts kits, standardized bus links, and transition panels for interfacing with other cubicle series.

Typical configurations

Common KSO-393-based configurations:
1) Incomer - connection of a power transformer or MV line, measurement and metering, optional automatic transfer;
2) Bus-section - bus sectioning to improve maintainability and contingency flexibility; variants with circuit-breaker or disconnector;
3) Feeder - outgoing cable and overhead lines equipped with protection and current/voltage monitoring;
4) VT/CT panel - auxiliary supply for measuring circuits, commercial/technical metering, system monitoring;
5) Plant auxiliaries - supply of DC/AC auxiliary power, control and life-support systems of the switchgear;
6) Bus coupler/tie - bus links and bypass connections between sections and busbars for flexibility during maintenance and expansions.

Compliance with standards (key norms)

• IEC 62271-200 - AC metal-enclosed switchgear and controlgear (design, type tests, internal arc classification IAC).
• IEC 62271-1 - Common specifications: service conditions, insulation levels, test methods.
• IEC 62271-100 - AC circuit-breakers: interrupting capability, endurance, test duties.
• IEC 62271-102 - AC disconnectors and earthing switches: drives, interlocking, mechanical endurance.
• IEC 60529 - Degrees of protection (IP code) to justify IP20 / locally increased IP ratings.
• EN/IEC 60721-3-3 - Environmental conditions for stationary use in weather-protected locations (replaces GOST 15150 U3 for climatic category).
• IEC 60038 - Standard voltages; dielectric test levels as per the IEC 62271 series.
• IEC 61869 (all relevant parts) - Instrument transformers (CTs/VTs) for protection and metering.

Engaging contractors, manufacturers, and investors

We offer cooperation to switchgear manufacturers, EPC contractors, and investors interested in localizing production of medium-voltage cubicles. The implementation package includes material and purchased-parts specifications, manufacturing instructions (cutting, bending, welding/non-welded assembly, painting), quality-control plans, cable schedules, and procedures for routine/functional tests. A phased transition is possible-from screwdriver assembly to full-cycle production of enclosures and busbars at your site. Staff training, process audits, and support of the first series reduce risks and accelerate certification.

Documentation offered - drawings and 3D models

A full set of design and shop documentation is provided for KSO-393: data sheets, single-line and functional diagrams, purchased-parts lists, assembly drawings and detailing, 3D models of assemblies and enclosures, cable schedules, and secondary connection diagrams. Popular formats are supported - AutoCAD (DWG/DXF), SolidWorks, Parasolid. Documentation is adapted to your component lineup, installed equipment (press brake, paint line, etc.), and corporate standards. Nameplate templates, labeling schemes, and packaging/transport recommendations can be provided as needed.

Operation and maintenance

The “closed-door breaker operation” concept is mandatory for safety and improves the predictability of switching. Modular architecture and unified parts shorten repair time and simplify spares management. We recommend regular checks of bolted joints and thermal conditions of high-current nodes, adjustment of protection settings to the current network configuration, and periodic verification of mechanical interlocks. For sites with high industrial-safety requirements, consider arc-flash protection, partial-discharge monitoring, and remote thermal monitoring of cable lugs and busbars.

Technical data

We offer you the documentation set for manufacturing KSO-393:

- Preliminary technical package for tenders: data sheets, specifications, single-line and functional diagrams, equipment lists - for fast compliance checks and preparation of a commercial offer.
- Shop drawings, 3-D models, and a full design package to launch production at your site. If enclosure and busbar fabrication is not available in-house, we will arrange manufacturing at partner facilities; you perform final assembly, routine/acceptance tests, and installation.
- Rapid document updates to your project requirements and manufacturing capabilities; support for component procurement, supervisory installation and commissioning; preparation of insulation and functional test programs.

Benefits of working with us:

- No need to maintain a large team of highly qualified engineers: the documentation set is structured for confident work by a mid-level engineer.
- Serial launch is possible without building a costly prototype, thanks to proven standard modules and validated solutions.
- Technical support at all stages - from adapting documents to your component lineup to commissioning support and preparation of O&M manuals.

For additional information on KSO-393, please contact: inbox@proekt-energo.com

Experience shows that an error made at the design stage leads to a multiple increase in costs during manufacturing and throughout operation. Correct specification of apparatus, competent design of busbar joints, and selection of instrument transformers with the required accuracy classes are the foundation of reliable and safe substation operation over its life cycle.

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