Retrofitting the KR-10 withdrawable unit involves replacing the 6–10 kV cell's withdrawable trolley (WT) with a modern module featuring a vacuum circuit breaker and compatible interface units, while retaining the basic parts of the switchgear: the cabinet housing, busbars, cable connections, and the main layout of the switchgear. For most KR-10 facilities, retrofitting is a practical alternative to complete replacement of the switchgear: the equipment in the building remains in place, and only the “working connection mechanism” is updated — a trolley with a switch, contacts, curtains, interlocks, and a secondary interface. This approach is especially effective when the old switch has reached the end of its service life, scheduled maintenance becomes unpredictable, the plug-in unit overheats, or problems arise with interlocks and curtains.

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• Where KR-10 is used and when VE replacement is needed
• What retrofitting offers: operational advantages
• KR-10 roll-out element: composition and key components
• Compatibility with the cell: main circuits, mechanics, curtains
• Secondary circuits: connector and control logic connection
• Technical data (typical)
• How KR-10 retrofitting is performed: work algorithm
• Quality control and measurements (important for 6–10 kV)
• Options and functionality expansion

Where KR-10 is used and when VE replacement is needed

KR-10 is widely used in 6–10 kV switchgear at industrial enterprises, substations, and infrastructure facilities where maintainability and prompt maintenance of connections are important. The need to replace the withdrawable unit usually arises when the following signs appear:

• increased time required for circuit breaker maintenance and “floating” repair volume from inspection to inspection;
• burning/heating of the plug-in unit, traces of thermal impact on contact parts;
• unstable trolley adjustment: the need to “press down,” the appearance of backlash, skewing when rolling in;
• problems with curtains: incomplete closure, jamming, loss of clear kinematics;
• Reduced reliability of interlocks and limit switches (false prohibitions or, conversely, lack of prohibition).

What retrofitting offers: operational advantages

• Transition to vacuum switching — reduction of labor-intensive regulations and increase in operational resources.
• Normalization of the contact assembly — restoration of reproducible contact pressure and reduction of the risk of local overheating.
• Predictable mechanics — fine-tuned adjustment, fixed trolley positions, and clear locking logic.
• Reduced downtime — delivery of the assembled switchgear transfers the main adjustments and checks to the factory stage, leaving only installation and commissioning at the site.
• Readiness for secondary modernization — easier to implement arc protection, relay protection and automation terminals thanks to a streamlined secondary interface.

KR-10 roll-out element: composition and key components

The KR-10 roll-out element is a set of components that determine the safety of maintenance, thermal conditions, and connection stability during emergency modes. As part of the retrofit, a new VE (usually assembled) is formed, including:

• Trolley frame with bases that ensure repeatable roll-in geometry, without skewing or “wandering” elevation marks.
• 6–10 kV switch of the vacuum type (alternative — SF6 according to technical specifications) with drive; readiness circuits, block contacts, and manual controls are provided according to the design.
• Primary plug-in contacts with adapters for the mating parts of a specific KR-10 cell: the insertion depth, contact travel, and required contact force are fixed.
• Adjustment and locking mechanism that moves the trolley from the “test” to the “working” position with controlled pressure, eliminating under-adjustment.
• Curtains (or assemblies interacting with cell curtains) for automatic closure of current-carrying parts during roll-out.
• Locks and position sensors: prevention of erroneous operations and limit switches for “repair/test/working” positions.
• Secondary interface: connector/terminal module for connecting control, signaling, and relay protection circuits.

Compatibility with the cell: main circuits, mechanics, curtains

KR-10 comes in different versions and with object modifications, so retrofitting is performed with reference to a specific cell. Main compatibility points:

1. Main circuit: plug-in node geometry, phase alignment, contact pressure, dielectric distances, transition resistance control.
2. Movement mechanics: type of guides/rollers, stops, locks, trolley stability, and absence of misalignment along the trajectory.
3. Curtain mechanism: guaranteed coverage of plug-in unit openings when switching to “repair” mode, no jamming or spontaneous opening.

If a grounding device is present in a specific KR-10 configuration, the “switch-trolley-grounding device” interlocks and restrictions on the sequence of operations are linked.

Secondary circuits: connector and control logic connection

For successful replacement of the power unit, it is important to ensure correct connection of secondary circuits without “re-soldering” and chaotic modifications at the facility. Three typical scenarios are used:

• “1:1” connector — a complete replica of the existing connector and pinout; minimal installation work.
• Transitional pinout — adapter/strip with a circuit correspondence table (I/O matrix), marking and signaling logic are preserved.
• Replacement of the mating part — in case of contact wear or function expansion (control of shutdown circuits, addition of arc protection, new telemechanics signals).

Technical data (typical)

How KR-10 retrofit is performed: work algorithm

1. Cell inspection: photo documentation, measurements, determination of the contact system type, assessment of curtains, interlocks, and secondary connectors.
2. Designing the connection: contact adapters, kinematics of the adjustment, list of interlocks, table of correspondence of secondary interface circuits.
3. VE assembly: switch installation, adjustment of fine-tuning and interlocks, checking of secondary circuits and signals.
4. On-site installation: installation of trolley, connection of secondary circuit, control measurements of main circuit, checking of curtains.
5. PNR: functional check of interaction with RZA, correctness of shutdown, signaling, and (if necessary) telemechanics.

Quality control and measurements (important for 6–10 kV)

To prevent overheating and “floating” blockages, it is recommended to accept the KR-10 retrofit based on the following measurable criteria:

• micro-ohmmetry of the transition resistance of the main circuit after several roll-in/roll-out cycles;
• checking the adjustment and fixing of positions with control of limit switches;
• checking the curtains and interlocks for correct sequence of operations;
• functional checks of secondary circuits: switching on/off, position signals, interlock circuits, and disconnection from the relay protection and automation system.

The result is protocols and a list of settings (limit switches, interlocks, pinouts), which makes further operation predictable.

Options and functionality expansion

• arc protection (optics + current criterion) for accelerated arc shutdown;
• RZA modernization: terminals, UROV/APV according to the project, recording of oscillograms and events;
• status monitoring: operation counter, resource assessment, control of operating circuit voltage;
• integration into ACS/SCADA: remote signaling and remote control according to the project (if a terminal/gateway is available).

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

- Preliminary technical documentation for participation in tenders for the replacement of the KR-10 roll-out element (6–10 kV). 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 the manufacture of the KR-10 roll-out element at your enterprise. If you do not plan to manufacture the product components and parts yourself, we will help you outsource their manufacture to third-party enterprises. Your enterprise will perform the final assembly and installation of the product. All documentation will be adjusted, if 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:

- Link to your specific KR-10 cell: contacts, fine-tuning, curtains, locks, and secondary interface are designed as a controlled technical solution.
- Minimization of downtime due to factory preparation of the assembled VE and a clear installation/PNR algorithm.
- Quality control methods (micro-metrology, interlock testing, pinout certification) increase operational predictability.

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

PDF - Download technical information on replacing the KR-10 roll-out element