K-59 Switchgear - Withdrawable Element Replacement (Retrofit)

Retrofit is the modernization or partial re-equipment of metal-clad switchgear (KRU) and KSO cubicles by replacing life-expired equipment with modern equivalents without rebuilding the switchgear room.
The primary focus is the replacement of the most stressed and safety-critical unit - the oil circuit-breaker. New interrupting devices are vacuum or SF₆ circuit-breakers with spring-charged or magnetic-actuator mechanisms; unlike oil breakers, they are essentially maintenance-free, offer longer service life and stable arc-quenching characteristics. A more extensive (comprehensive) modernization of the switchgear is also possible: block replacement of the compartment, including the withdrawable element (truck), shutter mechanism, earthing switch operating mechanism, door, relay cabinet, and, if necessary, adaptation of cable terminations.
The reliability of the switchgear depends directly on the reliability of its switching equipment. Such modernization is a simple and cost-effective way to address ageing breakers in legacy switchgear and improve industrial safety.
Retrofitting existing electrical equipment is more economical than purchasing new gear, performing design and installation works for its placement, and compensating losses from reduced power delivery during replacement; at the same time, periodic repairs of end-of-life breakers do not guarantee the required supply reliability. Other cell elements do not always require renewal.

Purpose and application

The K-59 withdrawable element retrofit is intended to extend the service life of in-service medium-voltage (MV) switchgear 6–10 kV, 50 Hz at industrial plants, utility substations, and transport/municipal infrastructure. The main task is to replace obsolete small-oil/oil circuit-breakers with modern vacuum or SF₆ devices with minimal intervention in the cell design and without replacing busbars, foundations, or cable entries. The solution provides:
- compliance with up-to-date safety and operational reliability requirements;
- reduced operating costs (no oil handling, less routine maintenance, predictable service intervals);
- improved maintainability thanks to shorter repair/outage windows and quick removal/installation of the withdrawable element;
- compatibility with modern microprocessor protection and control IEDs (installation of new PAC devices with self-diagnostics, disturbance recording, and communication protocols).

Typical applications include 6–35 kV incoming/feeder sections of substations, power-plant service boards, distribution substations of industrial facilities (main/plant/central distribution), mining, oil & gas, chemical, metallurgical and pulp & paper industries, as well as infrastructure power systems (airports, metros, data centers, logistics hubs). In typical projects, retrofit enables rapid restoration of interrupting capacity, achievement of required protection settings and selectivity, improved maintainability, and safer operation for personnel.

Technical data (typical values)

Parameter	Value / range	Note
Rated voltage, kV	6; 10 (up to 12 by insulation level)	Selected to match the network
Rated current of main circuit, A	630 / 1000 / 1250 / 1600 / 2000 / 2500	Depends on feeder duty
Rated short-circuit breaking current, kA	20 / 25 / 31.5 (3-phase)	Per IEC 62271-100
Rated short-time withstand current 1 s, kA	20–31.5	Thermal withstand
Rated peak withstand current, kA (peak)	50–80	Depends on breaker series
Circuit-breaker class	E2 / M2 / C2	Switching duty, mechanical endurance, pole discrepancy
Operating mechanism	Spring-charged / magnetic actuator	Motor-charging option
Control voltage, V	110/220 V DC (others on request)	For relays & mechanism
Degree of protection	IP 2X for the compartment; higher per project	Per IEC 60529
Secondary interface	Standardized plug-in connector	Labeling per project documentation
Mechanical endurance	≥ 10,000–30,000 operations	Depends on breaker model
Ambient temperature range, °C	-25…+40 (-40 on request)	With space heaters as needed
P&C compatibility	Modern IEDs with protocols (IEC 61850/Modbus, etc.)	Per project specification

Service conditions

The solution is intended for indoor MV switchgear under the following conditions (unless specified otherwise by the project):
- ambient temperature: -25 °C to +40 °C; -40 °C available with heaters/insulation shields;
- relative humidity: up to 95 % at +25 °C without condensation; for high humidity, install cabinet heaters and desiccants in the relay cabinet;
- altitude: up to 1000 m a.s.l. (higher on agreement with dielectric clearances and/or insulation levels adjusted);
- installation category - rooms without conductive dust or aggressive gases; pollution degree according to the site category; for harsh environments, dust/moisture-protection measures are applied (door gaskets, insulating barriers, sealed entries);
- seismic withstand - as per project requirements (solutions up to 7–8 MSK/Richter available subject to calculations and/or tests).
Environmental classification is selected per IEC 60721-3-3 / IEC 60721-3-4 as applicable to the site.

Climatic execution and location category are chosen for the site conditions. For cold regions, relay-cabinet heaters and moisture protection are used; for dusty plants - reinforced shutter mechanisms, barriers, and routine inspections. Operation with equipment-induced vibration is acceptable within the limits for the corresponding class of switchgear.

Layout and design solutions

The withdrawable element is built on an adapter frame that mates the new circuit-breaker to the existing interfaces of the K-59 cell: tulip/plug-in primary contacts, busbars, shutter mechanism, and earthing-switch drive. The layout provides:
- modern circuit-breaker (vacuum or SF₆) with integrated spring-charged/magnetic actuator mechanism rated to E2/M2/C2 classes and specified breaking currents;
- mechanical adaptation: guides, latches, stops, and linkages to preserve the kinematics of racking between DISCONNECTED / TEST / SERVICE (CONNECTED) positions; if required - a new racking drive with the option of motorized racking under a closed door;
- shutter mechanism with automatic closure of primary openings upon withdrawal, ensuring the required degree of protection and clearances;
- secondary adapter with a unified plug-in connector, 1:1 mapping to existing circuits, and project-based marking; migration to a new connector type is possible while keeping the cell wiring;
- earthing-switch drive (where fitted) retained or upgraded with rods and interlocks; a new fast-closing earthing switch with making capacity may be installed;
- integration of protection & control: installation of new microprocessor IEDs (ANSI/IEC functions), CTs and VTs of required accuracy classes, indication panels, and position sensors;
- “closed-door” measures: remote racking and breaker ON/OFF with the door closed, viewing windows and nameplates, addition of arc-relief channels and pressure-relief flaps (if specified by the project);
- life-cycle support: modular components, spare-parts availability, and serviceability (quick access to mechanisms, bearings, and primary contacts).

Block replacement of the compartment (frame assembly) can be provided where required - a factory-built module with the breaker, shutter assemblies, latching and interface parts adapted to the existing tulip contacts. Such a module minimizes commissioning time and provides standardized interlocks plus type-tested short-circuit withstand, dielectric and functional tests at module level.

Safety

The safety package includes standard and optional mechanical/electrical interlocks preventing incorrect operations: blocking racking with the breaker closed, blocking breaker closing in intermediate positions, blocking compartment doors with the earthing switch engaged, master-key systems, and padlockable hasps for lockout-tagout. Shutter mechanisms automatically screen live parts during withdrawal; voltage presence indicating systems VPIS/VDS, position auxiliary switches, and coded terminal blocks help prevent miswiring. On request, remote racking and remote breaker operation reduce personnel exposure to arc-flash. The design ensures required creepage and clearance distances and forms internal barriers between compartments per project category.

Manufacturing options

For K-59, multiple modernization depths are available - from replacing the breaker on the existing truck to supplying a factory-ready module. Selection depends on deadlines, budget, cell condition, and site maintenance policy. A generalized comparison is given below.

Option	Scope	Pros	Notes / limitations
A. Breaker replacement on the existing truck	Adaptation kit + new breaker; interlocks upgrade, secondary rewiring, mechanical checks	Lowest material cost; familiar kinematics retained	Requires fitting work and more commissioning time; depends on truck condition
B. Complete replacement of the withdrawable element	New truck within K-59 dimensions, 100% compatibility with interlocks	Short commissioning; old truck can remain as a spare	Higher cost, lower labor; requires template fit-check
C. Factory-ready module (OneFit-type)	Factory adapter frame with breaker, shutters, and interlocks	Minimal outage, type-tested assemblies, higher repeatability	Subject to legacy cell dimensions; verify compatibility of bushings/busbars

Standards compliance

Retrofit is performed in line with international standards for medium-voltage equipment. Typical requirements for new components and sub-assemblies:
- IEC 62271-1 - common specifications for MV/HV switchgear and controlgear;
- IEC 62271-100 - AC circuit-breakers (E/M/C classes, ratings, switching performance);
- IEC 62271-200 - metal-enclosed switchgear for indoor installation (internal partitioning/accessibility categories);
- IEC 62271-102 - earthing switches (making capacity and interlocking);
- IEC 60529 - degrees of protection (IP codes) for doors and compartments;
- IEC 60068 / IEC 62262 - environmental/impact tests for individual assemblies as per project.
The scope of routine/site acceptance tests is defined by the commissioning program and project documentation.

Contractors and partnership

We welcome cooperation with contractors, switchgear manufacturers, and investors interested in serial production and deployment of K-59 retrofit solutions and compatible MV switchgear series. Cooperation models include: supply of design documentation packages for in-house manufacturing, contract manufacturing of selected units, co-branding of ready-made modules, localization of metalwork fabrication, training and author supervision during implementation. For large-scale retrofit programs, we prepare standard solution maps, budgetary estimates, delivery schedules, and turnkey commissioning plans.

We offer documentation for the K-59 withdrawable element replacement (retrofit):

- Preliminary technical documentation for tender participation on K-59 truck replacement. We will prepare the information needed to assess manufacturability per tender requirements and data sheets.
- Working drawings, 3-D models, and other documents required to manufacture the K-59 withdrawable element at your facility. If you do not plan to make parts and assemblies yourself, we will help place orders with third-party shops. Final assembly and installation can be performed at your site.
- All documentation can be adjusted, if required, to the project requirements and to your facility’s manufacturing capabilities.
- If your substation has equipment from another manufacturer, we will prepare documentation for similar retrofit equipment to complement what is installed.

Why work with us:

- No need to maintain a large team of senior engineers - you receive a complete design package for the product that can be handled by a mid-level engineer.
- No need to build pilot prototypes - our experience allows launching serial production directly.
- Working to our documentation, your specialists will receive guidance on all nuances of K-59 withdrawable element replacement.