A retrofit of KRU K-13 (K-XIII) is a set of measures to upgrade the switching section of medium-voltage cubicles (6–10 kV) by replacing life-expired components with modern ones while retaining buildings, bus bridges, cable terminations and most metalwork. This approach quickly improves reliability and safety without the high cost of a complete switchgear replacement and without long outages of process equipment.

Purpose and scope

The primary objective of the K-13 retrofit is to replace the oil circuit-breaker with a modern vacuum or SF₆ circuit-breaker (gas-insulated) with a spring-charged or magnetic actuator. The upgraded withdrawable unit operates normally within the existing KRU/KSO and fully integrates into interlocking chains, control circuits and protection/automation systems. The solution is suitable for:

• industrial substations (main step-down substations, distribution switchrooms, package substations) across chemical, oil & gas, mining & metals, and pulp & paper industries;
• power and utility infrastructure: CHP plants, boiler houses, 35/6–10 kV substations, district substations, district/individual heating substations;
• transport and logistics infrastructure: traction substations, compressor stations, port facilities;
• generation based on renewables (wind and small hydro) and backup diesel/gas-engine gensets where high operating duty and fast clearing are required;
• facilities with stringent continuity-of-supply and operational-risk requirements.

A retrofit is equally effective for a single withdrawable unit replacement or as part of a phased modernization program of an entire switchroom. In most cases the feeder interface, secondary terminal blocks, cable terminations and bus bridges can be retained-while the switching module is upgraded first.

Service conditions

Upgraded withdrawable units for KRU K-13 are designed for standard service conditions used for medium-voltage switchgear:

• Rated voltage: 6 or 10(12) kV; frequency 50 Hz;
• Environmental classification: indoor installations per EN/IEC 60721-3-3; typical ambient temperature range from -25…-5 °C up to +40 °C (depending on version);
• Altitude: up to 1000 m without derating; higher altitudes by agreement with dielectric-strength correction factors;
• Relative humidity: up to 95 % at +25 °C without condensation (short-term);
• Pollution withstand: sealed-for-life interrupters ensure operation in dusty environments; for harsh conditions-filters, improved sealing and anti-condensation heaters are available;
• Seismic capability: configurations with validated analysis/tests up to zone 8 (on request);
• Overvoltage categories: compatible for joint operation with surge arresters to limit switching overvoltages;
• Atmosphere: non-explosive, free from conductive dust and aggressive gases in concentrations harmful to metals and insulation (special versions for designated zones on request).

For cold/tropical climates, optional packages include anti-condensation heaters, enhanced moisture protection, corrosion-resistant coatings, and vibration-resistant mounting. Versions tailored to oil & gas, transportation and nuclear industry requirements are available on agreement (factory QA levels, special coatings, marking, etc.).

Layout and design options

Retrofit options for K-13 are selected after a site survey: assessing compartment dimensions, busbar position, rail tracks, shutter mechanism, earthing-switch kinematics and secondary interfaces. We offer three proven concepts that differ in intervention scope, schedule and cost:

1. Adaptation kit on the existing withdrawable unit. The trolley and power contacts are retained; a new circuit-breaker (vacuum/SF₆) is installed with adapter plates and linkages, the actuator is adapted, cam interlocks/limit switches are renewed, and the secondary plug is replaced/reconfigured. Pros: minimal changes inside the cubicle. Cons: increased labor, precise kinematic alignment required.
2. Complete replacement of the withdrawable unit. A new withdrawable module is supplied, complete with circuit-breaker, primary contact arms, coordinated shutter mechanics and earthing-switch drive. Compatibility with mounting interfaces and interlocking logic is guaranteed. Pros: fast installation, predictable result. The former unit can be kept as a spare or for parts.
3. Factory-built “plug-in” module (Retrofill class). An integrated frame with a new circuit-breaker, internal primary interface and a hard-bus subsystem aligned with existing terminations. Includes protective shutters, interlock systems and test/maintenance positions. Type checks of dielectric clearances, temperature rise and opening dynamics are performed. Pros: highest repeatability and fastest commissioning.

Structurally, the new withdrawable unit includes: a trolley frame with position detents (“racked-out”, “test”, “service”), guide and brush contacts, shutter linkages, earthing-switch drive, secondary connectors, a local indication and limit-switch block, mounting plates for protection/AR/ATS functions, and options for phase-synchronization and wear signalling. The interrupter system is sealed; maintenance is limited to periodic checks of mechanics and electrical joints. Optional energy storage with remote charging, motor-charging drive, contact-wear sensors and operation counters can be fitted.

During retrofit we seek to improve dielectric distances and air clearances around primary contacts and live parts by using screening covers, improved bus hardware, heat-resistant insulators and modern materials. This lowers the probability of internal flashover under contamination and humidity and reduces thermal stress at continuous current.

Safety

Personnel and equipment safety is a key project criterion. The retrofit includes:

• Mechanical/electrical interlocks preventing incorrect operations (e.g., racking with the breaker closed, closing with the earthing switch engaged);
• Self-closing shutters on primary contacts;
• Position sensors and limit switches duplicating “ON/OFF”, “test/service” and “earthed” indications;
• Local pictograms and warning labels per ISO;
• Secondary-circuit verification via a test connector without applying MV to the primary circuit;
• Compatibility with protection & control devices (ANSI 50/51, 50N/51N, 27/59, 81, 94, 25, 46, etc.) and AR/ATS programs;
• Optional packages to enhance internal-arc robustness (directed pressure relief, reinforced doors and panels for legacy enclosures).

Commissioning includes dielectric tests of insulation, contact-resistance checks, thermal imaging, protection setting, and functional checks of interlocks and remote commands.

Configurations and supply

We supply K-13 retrofit kits and withdrawable units in several configurations:

• With a base vacuum circuit-breaker (rated current 630–3150 A; breaking capacity 20–31.5 kA; mechanical endurance up to 30–50 k cycles);
• With an SF₆ circuit-breaker as part of an integrated module (for specific service conditions where required);
• Actuator: spring-charged with motor-charging or magnetic actuator; with remote control capability;
• Secondary interfaces: one/two 32/64-pin connectors adapted to standard K-13 terminal blocks;
• Options: shunt/undervoltage releases, SF₆ density sensors (where applicable), circuit-integrity test devices, key-interlock systems, add-on protection cabinets.

Supply is possible as a self-installation kit at the Customer’s site (with author supervision) or as a turnkey service including a site supervisor, commissioning and staff training.

Standards compliance

K-13 retrofit solutions are engineered and manufactured to the current requirements applicable to medium-voltage switchgear and controlgear, including:

• EN/IEC 62271-1 - general requirements for medium-voltage switchgear and controlgear;
• EN/IEC 62271-200 - metal-enclosed switchgear for voltages above 1 kV and up to and including 52 kV;
• EN/IEC 62271-100 - AC circuit-breakers;
• EN/IEC 62271-102 - disconnectors and earthing switches;
• EN/IEC adoptions applicable in the customer’s region;
• Applicable electrical installation rules and industry safety regulations in the country of use.

Engaging contractors and partners

We are open to cooperation with electrical equipment manufacturers, metalwork plants, installation and commissioning firms, engineering companies and investors interested in serial manufacture and deployment of K-13 retrofit kits. Possible cooperation models:

• Licensed assembly to our design package at the partner’s site with supply of critical components (trolley frames, contact arms, shutter mechanisms, interlock assemblies);
• Contract manufacturing of selected assemblies and mechanical parts at the contractor’s facilities with our acceptance;
• EPC-format partnerships (survey - design - manufacture - commissioning - service) for large modernization programs;
• Investment projects to set up a new area/line for serial retrofits of legacy KRU series.

For design and tender teams we provide an advance information package: BIM/CAD-ready 3D models, typical specifications, BOMs, test protocols, commissioning procedures, risk registers and safety plans.

Documentation offered

Delivered with the supply and/or under a separate contract:

• Complete design package (fabrication drawings, parts lists, schematic/connection diagrams, kinematic diagrams, operation & commissioning manuals);
• 3D models in STEP/Parasolid, plus sets in AutoCAD (DWG/DXF) and SolidWorks for production prep;
• Questionnaires and specification templates for tenders, nameplates and service logs;
• Test protocols (electrical, mechanical, interlock checks) and conformity lists;
• Survey methodology for existing K-13 cubicles with defect checklists.

Technical data

Project implementation steps

1. Survey of K-13 cubicles: measurements, photo records, condition of trolleys, contacts, shutters, drives and secondary circuits;
2. Engineering: 3D modelling, interface adaptation, schematic review, preparation of drawings and questionnaires;
3. Manufacture of frames, arms, shutter mechanics, breaker/actuator selection, assembly of modules;
4. Pre-factory tests: dielectric checks, temperature-rise, mechanical cycling, interlock and secondary-circuit checks;
5. Delivery and site supervision, integration into cubicles, alignment checks, commissioning with protection engineers;
6. Putting into service, staff training, handover of documentation and test records.

Economic effect and operational advantages

• Lower CAPEX compared with full switchgear replacement (no dismantling/installation of enclosures, busbars and cables);
• Minimal downtime - phased work while keeping adjacent feeders energized;
• Lower OPEX - no oil system, no drain/fill procedures, no arc-chamber servicing;
• Higher electrical safety (improved clearances, robust interlocks, accurate indication);
• Predictability - proven designs and type-checked assemblies reduce rollout risks.

Bottom line: retrofitting the K-13 withdrawable unit is a fast, predictable way to extend switchgear life, align it with modern standards and increase electrical readiness without major reconstruction.

Why work with us

- No need to maintain a large in-house engineering team - you receive a complete design package that a mid-level engineer can work with.
- No pilot prototypes required - our rollout experience enables immediate series production.
- Your specialists receive consulting on all KRU K-13 (K-XIII) withdrawable-unit replacement nuances: from kinematic alignment to interlock checks and commissioning.

For more information on KRU K-13 (K-XIII) withdrawable-unit replacement (retrofit), contact: inbox@proekt-energo.com

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