RETROFIT is the modernization or partial re-equipment of complete switchgear (KRU) and single-sided service chambers (CSO) with the replacement of obsolete equipment with modern equipment. For 6–10 kV switchgear of the K-10 series, the greatest practical effect is usually achieved by replacing the withdrawable element with an obsolete oil/low-oil circuit breaker (standard devices of the VMP/VMPE family and analogues) with a new withdrawable element with a vacuum (or SF6) circuit breaker and a modern drive. Unlike oil-filled devices, vacuum circuit breakers do not require oil maintenance, have a high mechanical and switching capacity, ensure stable shutdown parameters, and simplify routine maintenance. At the same time, if necessary, locking mechanisms, curtain devices, earthing switch drives, secondary circuits, mating parts of connectors, and door panels are also updated if necessary. Retrofitting allows you to keep the cabinet, busbars, busbar bridges, foundations, cable entries, and mounting locations, significantly reducing the budget and downtime without compromising reliability.

Purpose and scope of application

The proposed solution is designed to replace the withdrawable unit (WU) of the K-10 series switchgear with a new withdrawable unit that is compatible in terms of dimensions and connection sizes with the existing cell. The retrofit is applicable for 6 and 10 kV distribution devices with an industrial frequency of 50 Hz at substations and power distribution points of power systems, at industrial and infrastructure facilities, in the oil and gas and mining sectors, at housing and communal services facilities, and in the agro-industrial complex. The typical reason for the project is the exhaustion of the circuit breaker's service life and/or increased operational risks (oil leaks, instability of shutdown parameters, shortage of spare parts, increased time for inspection and repairs), as well as the need to improve industrial safety and bring the equipment up to modern operating requirements.

The updated withdrawable unit with a modern circuit breaker ensures the performance of standard switching operations (connection/disconnection, automatic protection and control, interaction with relay protection and automation) in normal and emergency network modes, including short circuits and overloads. The design is intended for operation in networks with isolated or compensated neutral. Compatibility is ensured by power plug adapters that geometrically replicate the mating parts of a specific K-10 modification, as well as by matching the secondary interface (standard connector, transition plates, or replacement of the mating part of the connector according to the project). If necessary, the modernization is supplemented by the introduction of arc protection, updating of TT/TN, installation of modern RZA terminals, circuit breaker life counters, and remote monitoring devices.

Technical data (typical)

Operating conditions

The retrofit kit is designed for use in switchgear rooms and/or outdoor cabinets (if available in the appropriate version) that meet the requirements of current standards. Climatic versions — U1/UHL1 according to GOST 15150 (or equivalent according to the project), the temperature range and humidity requirements are determined by the initial cell and site conditions; in case of high humidity/condensation, anti-condensation measures (heaters, ventilation, drainage, microclimate control) are provided . Permissible installation height — up to 1000 m above sea level without derating; at higher altitudes, additional calculations of electrical strength and thermal conditions are performed. The degree of protection of the enclosure and the design of the pressure relief doors/valves are determined by the design of the K-10 cabinet and are agreed upon at the survey stage.

Seismic resistance, vibration resistance, fire resistance of cable entries, and contamination/condensation categories are selected based on the data of the K-10 base cell and project requirements. For outdoor cabinets, the following are additionally specified: thermal insulation, heating and ventilation, UV resistance of coatings, corrosion protection of metal structures and fasteners, types of cable glands and cable seals.

Layout and design solutions

The basic layout of the new roll-out element for K-10 retains the logic of the original cell: trolley (frame) with switch, primary plug-in contacts, roll-out/roll-in mechanism along guides, set of mechanical and electrical interlocks, curtain mechanism, mating part of secondary connector, and controls on the front panel. The design uses:

• a modern vacuum (or SF6, depending on the design) switch with a spring or electromagnetic drive, with a service life sufficient for intensive operation;
• power contact adapters that ensure geometric compatibility with busbar and cable mating parts of a specific K-10 modification without reworking the busbar;
• a universal secondary connector (or a set of adapter plates) for connecting existing control, signaling, and relay protection and automation circuits;
• connection earthing mechanism (if provided for by the cell design) with drive, locks, and position indication;
• curtain devices that automatically close plug-in contacts when the trolley is rolled out, and mechanical door locks;
• a set of plates, pictograms, inspection windows, and inter-section/inter-compartment locking devices (as designed).

For the K-10 fleet, it is usually advisable to consider three levels of modernization (in terms of labor intensity and implementation time):

1. Adaptation kit for existing VE — replacement of the switch and adaptation of interlocks/secondary circuits on the standard trolley. Minimum cost, but higher labor intensity and duration of work, requires precise adjustment of the geometry of the plug-in unit and drives.
2. Complete replacement of the roll-out element — delivery of a new VE assembly, fully compatible in terms of mounting locations, dimensions, and interlock logic. The fastest commissioning; the original retractable element can be left as a spare (in agreement with the operating department).
3. Modular plug-in unit (factory retrofit module) — a single ready-to-use module with built-in curtains, interface frame, unified contact and locking system. Minimization of installation risks, ease of maintenance, and repeatability of parameters; higher cost, justified for serial replacement.

The optimal option is selected based on the results of the RU survey and analysis of the source documentation. For K-10, differences in the design of the adjustment mechanisms, the location of the locking elements, the types of secondary connectors, and the cable compartment layout options are critical — therefore, the project must be based on photographs, measurements, short-circuit parameters, and actual secondary circuit diagrams. If necessary, the front panel is modified, the mating parts of the secondary connector are installed/replaced, the limit switches and indicators are relocated, and the curtain mechanism and drive elements are replaced.

Safety

The retrofit concept maintains or improves the level of operational safety compared to the original K-10 configuration. Mechanical and electrical interlocks are implemented to prevent erroneous operations (prohibition of moving the switch when the switch is on, prohibition of switching on when the trolley is not in the working position, interlocks “switch - earthing switch”, locking of the compartment door when the connection is on). Fixed “repair/test/operating” positions, main device position indicators, the possibility of sealing and installing padlocks are provided. Depending on the project requirements, arc protection (optical sensors/current criteria), voltage control, event logging, and remote access interfaces are implemented.

For increased personal safety requirements, solutions can be designed taking into account the principles of internal arc resistance (IAC) and LSC categories for continuity of service. For existing K-10 cabinets, the actual achievability of IAC/LSC is determined by the design of the enclosure, the presence/type of pressure relief valves, and the strength of the doors; during retrofitting, additional guide channels and reinforced elements may be installed (based on the results of calculations and tests).

Manufacturing options and options

• Switches: vacuum switches from industrial manufacturers (rated at 6/10 kV; currents 630–3150 A; breaking capacity 20–40 kA); alternatively, SF6 switches of a specified type.
• Drives: spring-motor (with emergency manual cocking) or electromagnetic; manual/motor drive for trolley adjustment — depending on design; local and remote control.
• Secondary circuits: secondary connector compatible with the original diagram; adapters for existing harnesses; modernization of APV/AVR diagrams, remote signaling, and local indication.
• RZA and service: protection and automation terminals (MTZ, ZZ, directional stages, UROV), arc protection, recorders, integration according to IEC 61850/Modbus (according to the project).
• Materials and execution: galvanized/stainless steel elements, powder coatings, anti-condensation heaters, temperature/humidity sensors.
• Documentation: 3D models, design documentation, specifications, installation/configuration/operation instructions, test reports, test methodology programs.

Comparison of typical retrofit approaches

Compliance with standards

The retrofit solution is designed in compliance with current requirements for high-voltage switching equipment and complete devices. The project specifies target standards and boundaries of responsibility (device/substation/cell). When selecting a circuit breaker and accessories, the provisions of the following documents are taken into account (the list is specified for a specific facility):

• IEC 62271-1 — general requirements for high-voltage AC apparatus and complete units;
• IEC 62271-100 — AC circuit breakers (resource classes, switching capacity, tests);
• IEC 62271-102 — Disconnectors and earthing switches (mechanical and interlocking requirements);
• IEC 62271-200 — 1–52 kV metal-clad switchgear assemblies (LSC/IAC classification for new/upgraded switchgear);
• IEC TS 62271-304 — classification of indoor operating conditions with condensation/contamination;
• GOST 15150 — climatic versions and equipment placement categories.

Attracting partners and contractors

We are open to cooperation with electrical equipment manufacturers, machine-building enterprises, and engineering companies for the serial production of roll-out elements for K-10. Possible formats: supply of a complete set of electrical equipment according to the customer's specifications, supply of components and “semi-finished products” (frames, adapters, facade sheets, curtain mechanisms, a set of locks), transfer of a set of design documentation with author's supervision of the launch into production, as well as “turn-key” — inspection, design, manufacture, installation, PNR, and commissioning at the facility. For integrators and service companies, it is interesting to enter the market for servicing the installed K-10 fleet with unified selection technology and repeatable VE design.

Documentation offered

The standard package includes: a set of working drawings (DWG/DXF), specifications, operating documentation, 3D models (STEP/Parasolid), facade panel layouts, assembly diagrams and incoming inspection cards, transportation/storage/installation/commissioning instructions, type and acceptance test reports. The documentation is adjusted to the project requirements and technological capabilities of your production (metal thickness, available coatings, fastener nomenclature, etc.). Upon agreement, source files for AutoCAD/SolidWorks/Compass-3D are provided for quick integration into PLM.

We offer you documentation for replacing the roll-out element of the K-10 switchgear (retrofit):

- Preliminary technical documentation for participation in tenders for the replacement of the KRU K-10 roll-out element. We will prepare the necessary information for you to assess the possibility of manufacturing products in accordance with the requirements of the tender documentation and questionnaires. - Working drawings, 3-D models, and other necessary documentation for manufacturing the KRU K-10 roll-out element at your enterprise. If you do not plan to manufacture the product's components and parts yourself, we will help you outsource their manufacture to third-party enterprises. Your enterprise will perform the general assembly and installation of the product. All documentation will be adjusted as necessary in accordance with the project requirements and the technological capabilities of your enterprise. If equipment from another manufacturer is installed at the substation, we will prepare documentation for the manufacture of similar equipment in addition to the installed equipment.

Advantages of working with us:

- No need to maintain highly qualified engineering and technical personnel - you receive a set of documentation for the manufactured product, which can be handled by an engineer with average qualifications.
- No need to manufacture prototypes - our experience allows us to successfully launch serial production of the product.
- Working with our documentation, your specialists will receive advice on all the nuances of replacing the KRU K-10 roll-out element.

For more information on replacing the KRU K-10 roll-out element (retrofit), please contact: inbox@proekt-energo.com

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