Retrofitting the K-27 (K-XXVII) switchgear roll-out element involves modernizing the existing 6–10 kV switchgear by replacing obsolete and physically worn-out components with modern solutions (vacuum or SF₆ -switches, adapted mechanisms, new interlocks) without interfering with the structural part and without replacing the cell housing. This approach allows you to quickly increase the reliability and safety of the switchgear, reduce operating costs, and minimize equipment downtime. As part of the retrofit, existing cable entries, busbars, foundation base, and most of the metal structures are retained, which is especially important for facilities with limited shutdown windows and high requirements for uninterrupted power supply.

Purpose and scope of application

The purpose of the modernization is to extend the service life of the K-27/K-XXVII cells and bring them up to modern requirements for operational reliability, electrical safety, and maintainability without completely replacing the switchgear. Replacing the roll-out element solves the following key tasks:

• Ensuring the required switching capacity in 6/10 kV networks with isolated or compensated neutral by using vacuum circuit breakers with a switching capacity of up to tens of thousands of cycles, stable breaking capacity, and increased resistance to contamination.
• Reducing operational risks and costs by eliminating oil management, reducing routine maintenance, standardizing spare parts, and using sealed-for-life arc chambers.
• Improved personnel safety through the introduction of modern interlocks, curtain mechanisms, voltage indicators, as well as the option to bring the design up to the required LSC/PM/PI categories and measures to limit the consequences of internal arcing.
• Unification of the switchgear fleet - transition to standard series of devices (6/10 kV vacuum with spring-motor or electromagnetic drive) with wide market representation and affordable service support.
• Minimization of technological equipment downtime - the retrofit is designed to fit K-27 mounting locations and is compatible with the geometry of the guide and contact systems, which allows for replacement in short technological windows and in stages.

Areas of application: substations of power systems and power plants, distribution points of large industrial enterprises (metallurgy, chemistry, oil and gas, mining, cement and construction industries), transport facilities (metro, railway substations), data centers, commercial real estate, and housing and communal services. Retrofit can be used wherever K-27/K-XXVII series cells and their modifications are used, as well as panels from other manufacturers that are compatible in terms of connection dimensions.

Technical data (typical ranges for K-27)

Operating conditions

The converted cells retain the climatic design of the original switchgear (as a rule, U3 according to GOST  15150) and are designed for operation in rooms at altitudes up to 1000 m above sea level. Typical temperature ranges: from -5 °C to +40 °C (without heaters) and from -25 °C to +40 °C (when heaters are installed in the relay compartment). Permissible relative humidity up to 95% at 25°C without condensation. For facilities located above 1000 m, as well as in conditions of increased dust, vibration, aerosols, and moisture condensation, special design solutions are offered: increasing leakage paths and air gaps, applying moisture-proof coatings to current-carrying parts, sealing entries, local heating and ventilation of compartments, using moisture absorbers, and organizing directed air exchange. The project provides for adjustments to insulation levels and relay settings, taking into account reduced atmospheric pressure and non-standard climatic factors.

From the point of view of electromagnetic compatibility and noise immunity, local conditions are taken into account: the presence of frequency drives, arc furnaces, and powerful starting currents. Based on the results of the survey, additional filters, ferrite elements, shielding of secondary switching circuits, as well as redundancy of operating current (AC/DC) power circuits using fail-safe logic and battery status diagnostics.

Layout and design solutions

The K-27 retrofit is carried out according to one of three basic scenarios, selected for the specific site conditions and shutdown dates:

• 1) Replacement of the switch on the existing pull-out element. An adaptation kit is supplied (brackets, transition plates, drive shaft/coupling, rigid/flexible bus adapters) is supplied, mechanical locks are restored and checked, the secondary circuit plug connector is transferred/replaced, and the curtains and support rollers are inspected. Pros: minimal delivery cost and the possibility of phased commissioning; cons: dependence on the condition of the old trolley and guides, increased work time.
• 2) Complete replacement of the roll-out element with a new one. A new roll-out element is supplied with a switch installed and pre-adjusted locks, geometrically compatible with standard guides, contact tulips, and limit switches. The old element can be preserved as a spare. Advantages: quick installation, consistent assembly quality, minimal modifications to the cell, possibility of fleet standardization.
• 3) Factory-ready module (“OneFit” / “plug-in”). Includes trolley, switch, curtains, adjustment mechanisms (worm/lever), drives, terminal blocks, nameplates, and documentation. The module undergoes standard factory testing and has unified interfaces for K-27, which ensures predictable installation times, repeatable quality, and reduced commissioning work on site.

  The delivery includes vacuum circuit breakers from leading manufacturers (e.g., ZN63A/VS1, BB/TEL, BBR-10, Evolis, 3AH series, etc., as agreed with the project). The model selection is determined by the rated current and breaking capacity, the drive interface (spring-motor/electromagnetic), service life requirements, and operating conditions. If necessary, current/voltage transformers, arc current sensors, relay protection cabinet, microprocessor-based relay protection terminals, modernization of automatic transfer switch circuits, SSPTI/ASUTP, installation of voltage indicators, as well as retrofitting with optical signaling and programmable modular relays.

  Design improvements include: restoration or replacement of mechanical interlocks (prohibition of rolling out when the switch is on, prohibition of switching on when the element is extended, interdoor locks), adjustment of curtain mechanisms and their synchronization with the trolley movement, installation of guides and stops, revision of the contact system (tulips, knives), introduction of optical voltage indicators on connections, replacement of busbar entries if necessary. Marking is carried out in accordance with ESKD and current safety standards, secondary circuits are traced, and updated schematic documentation is provided.

  Safety

  The K-27 retrofit is aimed at increasing the level of protection for personnel and equipment. The following measures are being implemented:

  • Restoration and/or installation of new mechanical interlocks with interlocks (rollout only when the switch is off and the grounding device is on, key locks on drives and doors, “test/input” positions).
  • Curtain mechanisms (metal or insulating partitions) that prevent access to live parts when the roll-out element is removed, with PM or PI segregation class depending on the selected configuration.
  • Indication and diagnostics: visual position indicators (ON/OFF, input/test, EARTHED), optical indicators of voltage presence at connections, earth switch position control, contact connection overheating sensors as per design.
  • Measures to limit the consequences of internal arcing (optional): organization of gas exhaust channels, reinforcement of panels and doors, arc suppression guides in compartments, installation of fast-acting current/arc protection (including optical sensors), selection of accessibility category and IAC depending on site requirements.

  All solutions comply with the requirements of current standards and factory instructions. Upon agreement, the project achieves the objectives for Loss of Service Continuity (e.g., LSC2B) and partition class (PM/PI), as well as the target IAC parameters (A, AF, AFLR) within the design capabilities of a specific cell and room.

  Manufacturing options

  Retrofit kits are available in several versions, allowing for flexible adaptation to the specific features of the equipment fleet and budgets:

  • Basic - replacement of the switch with a mechanical adaptation kit and restoration of locks. Designed for cases where the condition of the trolley and guides is satisfactory and the repair time is limited.
  • Standard - delivery of a new roll-out element (trolley) with a switch, curtain assembly, and a set of secondary connectors installed. Recommended for standard cells without significant non-standard modifications made in previous years.
  • Extended - turnkey factory-ready module (trolley, switch, curtains, drives, terminal blocks, nameplates, factory protocols). Provides for a minimum amount of work on site and reduced commissioning times, suitable for mass replacement of several connections.
  • Special - for harsh operating conditions (aggressive environments, dust, vibrations, altitude > 1000 m, high humidity), with reinforced insulation, sealing, additional coatings and climate kits, as well as adaptation of relay protection and automation to the requirements of a specific technological process.

    Compliance with standards

    Retrofit solutions and documentation are geared towards compliance with current international and Russian standards, including (depending on the scope of work):

    1. IEC 62271-200 - AC metal-enclosed switchgear and controlgear 1–52 kV (LSC/PM/PI classification, requirements for compartments and internal arcing, current editions).
    2. IEC 62271-100 - High-voltage AC circuit-breakers (switching capacity, T100s/T100a modes, service life).
    3. IEC 62271-102 - Disconnectors and earthing switches (requirements for earthing switches and disconnectors).
    4. IEC 62271-1 - Common specifications for high-voltage switchgear and controlgear (operating conditions, insulation levels).
    5. GOST 15150/15543.1 - climatic design U3 for premises, placement category.
    6. GOST/IEC 60071-1/-2 - insulation coordination (according to the project).

    Economics, timing, and typical risks

    Practice shows that retrofitting K-27 is significantly cheaper than completely replacing switchgear and construction work: no dismantling of cable entries and busbars is required, dimensions and connections are retained, and downtime of technological equipment is reduced. Typical risks include hidden wear and tear of guides/curtains and contact systems, clogging of compartments, unauthorized modifications made in previous years, and errors in drawings. These risks are reduced by preliminary inspection (measurement, photo referencing), the manufacture of jigs and templates, bench testing at the factory, commissioning at the site, and quality control using checklists. For bulk deliveries, standard kits are used to speed up logistics and standardize spare parts.

    Comparison of retrofit options

    Option	Timeframe	Intervention	Cost	Advantages	Risks
    Replacing the switch on the old element	Longer	Medium	Low	Minimum delivery	Dependence on wear of trolley/guides
    New roll-out element	Fast	Low	Medium	Compatibility, repeatability, old one - in reserve	Precise cell measurement required
    OneFit module	Very fast	Minimal	Average/higher	Type testing, pre-adjustment of locks	Early project alignment required

    Attracting contractors and partners

    We invite electrical equipment manufacturers, machine-building and metalworking enterprises, RZA integrators, design and commissioning organizations, as well as investors interested in the production of retrofit kits for the K-27 cell park to cooperate with us. Various formats are possible: licensed assembly according to our documentation, cooperation in machining and painting, OEM partnership for circuit breakers, joint pilot projects at customer sites, localization of components, and subsequent certification. We provide support at all stages, from the selection of equipment and specifications to the organization of bench and acceptance tests.

    Documentation offered

    - Preliminary package for participation in tenders: scope of delivery, questionnaires, list of applicable standards, cable and connector schedules, single-line and structural diagrams.
    - Working drawings, specifications, 3D models (STEP/Parasolid), assembly instructions, electrical installation diagrams, secondary connection diagrams (DWG/DXF), list of tooling gauges and templates for assembly control. - Kit for manufacturing the roll-out element at your facility or outsourcing production: machining, bending, welding, painting, assembly, testing, packaging, and preservation. If necessary, selection of contractors for critical operations (powder coating, electroplating, insulating coatings).
    - Adaptation of the set of documents to the project requirements: dimensions of a specific cell, actual level of wear of guides and contacts, connectors and switch type used, requirements for relay protection and automation, automated control systems and telemechanics, local industrial safety standards and electrical installation regulations.

    Advantages of working with us

    - No need to maintain highly qualified engineering and technical personnel: You receive a complete set of documentation that a moderately qualified engineer can work with.
    - No need to produce prototypes: our experience and standardization of components allow you to start production immediately after approval and test assembly.
    - We advise on all aspects of replacing the K-27 (K-XXVII) switchgear roll-out element, including the selection of circuit breakers, contact adapters, secondary circuit connectors, relay protection and automation, and testing.
    - We assist with production cooperation (metal structures, painting, current-carrying parts, cable assemblies), supply templates, and train assemblers and adjusters. For serial deliveries, we provide safety stock of critical components.

    For more information on replacing the K-27 (K-XXVII) switchgear roll-out element (retrofit), please contact: inbox@proekt-energo.com

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