Retrofitting the withdrawable element (WE) of the KU-10C series switchgear is a technically correct replacement of the withdrawable connection trolley with a modern module for 6–10 kV networks while retaining the main part of the cell: metal body, busbars, cable approaches, and switchgear layout. This approach is used when the KU-10C cabinet is still mechanically and insulatively suitable for operation, but the “bottleneck” is in the withdrawable unit: the circuit breaker's service life is exhausted, the contact connection is unstable in terms of pressure, the adjustment does not ensure a repeatable working position, and the curtains and interlocks malfunction. As a result, replacing the VE transfers the connection to modern vacuum switching, restores the predictability of the mechanics, and simplifies further modernization of secondary circuits (RZA, signaling, arc protection, telemechanics) without reconstructing the entire switchgear.

When is replacement of the KU-10C withdrawable unit most justified?

• Switch resource: repairs become frequent, results are unstable, downtime and maintenance costs increase.
• Signs of overheating in the plug connection area: darkening/burning of contact parts, traces of heating on the insulation, “floating” transition resistance values.
• Incomplete carriage engagement: need for “re-engagement,” unstable fixation in the working position, skewing during rolling, increased backlash in kinematics.
• Failures of curtains and interlocks: incomplete closure, jamming, false locking, or lack of prohibitions on erroneous operations.
• Scheduled modernization of relay protection and automation: requires streamlining of the secondary interface, addition of shutdown circuit control, and ensuring readiness for telemechanics.

What is included in the new roll-out element: components and configuration

The KU-10C is not just a switch, but a complete connection module. To reduce the risks of “on-site adjustments,” a new roll-out element assembly is supplied in a standard project (based on the results of a specific cell inspection):

• trolley (frame) with support bases, guides/rollers, movement mechanism, and fastening;
• 6–10 kV vacuum circuit breaker with drive (spring-motor or electromagnetic — depending on operational power supply and operating modes);
• movable plug-in contacts and adapters for mating elements of the cell, designed for thermal conditions and electrodynamics;
• finishing mechanism (transfer to working position with controlled contact pressure);
• interaction units with curtains (or a curtain mechanism restoration kit — if necessary);
• set of locks and limit switches (carriage position, operation permissions/restrictions);
• secondary interface: “1:1” connector, adapter pinout or replacement of the mating part of the connector (depending on the condition of the cabinet).

Main circuits: contacting, adjustment, overheating, durability

For KU-10C, the key reliability factor is the quality of the plug connection and the repeatability of the adjustment. During retrofitting, measurable parameters are recorded that directly affect heating and service life:

• contact geometry: phase position, roll-in depth, contact travel, skew-free centering;
• contact force: the trolley must “settle” into the working position equally with each cycle, regardless of the skill of the personnel;
• transition resistance: micro-ohmmetry criteria are set (including control after several insertion/withdrawal cycles);
• Short-circuit stability: current-carrying parts, fasteners, and contact assemblies must withstand electrodynamic forces without residual deformation.

It is the “contacts + adjustment” that most often determine whether the upgrade will be durable. Therefore, the KU-10C retrofit is designed as a solution for the entire power supply unit, rather than as a replacement for the device without adjusting the connections.

Secondary circuits: connector, pinout, compatibility table

To prevent the introduction of the KU-10C power supply from turning into a lengthy “re-wiring” process, a scenario for connecting secondary circuits is selected in advance:

1. “1:1” connector — repeat of the existing connector type and pinout, minimum mounting window.
2. Transitional pinout — adapter/strip and circuit correspondence table (I/O matrix) with preserved labeling.
3. Replacement of the mating part of the connector — in case of contact wear, burnout, or expansion of functions (control of shutdown circuits, arc protection, additional telemechanics signals).

Recommended summary for the “secondary” — interface passport: pinout, list of signals, control points, and list of limit switches/block contacts involved in the logic of interlocks.

Technical data (typical)

Safety and interlocks: prevention of erroneous operations

Replacement of the KU-10C roll-out element must ensure unambiguous and verifiable safety. A typical set of functions that is incorporated and verified during retrofitting:

• prohibition of trolley movement when the switch is on;
• prohibition of switching on the switch outside the “test/operating” positions with confirmation of locking;
• correct operation of curtains: blocking access to live parts when exiting operating positions;
• “switch-trolley-door” logic and, if provided for by the design, connection to the grounding device;
• position indication and the possibility of sealing/locking in accordance with operating regulations.

Retrofit algorithm: inspection, manufacturing, installation, PNR

1. Inspection of the KU-10C cell: photos and measurements of the VE compartment, contact system, curtains, guides, fixing units, secondary connector; assessment of the condition of fixed contacts.
2. Binding project: contact adapters, finishing/stops, list of locks, secondary pinout and I/O matrix.
3. Factory assembly of the VE: adjustment of trimming and interlocks, functional checks of secondary circuits, mechanical runs.
4. On-site installation: VE installation, secondary interface connection, control measurements, curtain and interlock checks.
5. PNR and commissioning: checking switching on/off, position alarms, commands to switch off from the relay protection and automation system, and drawing up reports.

Acceptance and quality control: measurements and protocols

To prevent problems from recurring (overheating, “floating” positions, false interlocks), it is recommended to accept the KU-10C retrofit based on measurable criteria:

• micro-ohmmetry of the main circuit transition resistance (including control after several roll-in/roll-out cycles);
• checking the adjustment and fixing of the “repair/test/operating” positions with control of the limit switches;
• checking the curtains for complete closure and absence of jamming at all transitions;
• functional testing of secondary circuits: switching on/off, position signals, interlock circuits, disconnection from relay protection and automation.

The final documentation includes test reports and a list of settings (limit switches, interlocks, connector/adapter pinouts), which simplifies operation and further testing.

FAQ on KU-10C

Is it possible to replace only the switch, leaving the old trolley?
It is possible if the trolley, adjustment, contact assembly, and locks are in good condition. If there is overheating, backlash, or unstable fixation, it is safer to replace the entire switchgear.

Do the busbars and cable entries need to be replaced?
In a typical retrofit, no. The purpose of replacing the KU-10C switchgear is precisely to preserve the busbars and cable connections while updating the most worn-out unit.

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

- Preliminary technical documentation for participation in tenders for the replacement of the KU-10C switchgear 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 KU-10C switchgear 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. The final assembly and installation of the product will be carried out at your facility.
- All documentation will be adjusted as necessary in accordance with the project requirements and the technological capabilities of your facility.
- 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:

- The KU-10C retrofit project is built around critical parameters: contacting, fine-tuning, curtains, interlocks, and secondary interfaces are formalized as measurable and verifiable criteria.
- Downtime is minimized thanks to factory preparation of the assembled power equipment and a pre-designed circuit compliance table.
- As a result, you receive a KD/3D package and a quality control methodology (micro-ohmmetry, interlock verification, pinout passport), which increases operational predictability.

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

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