By TEBAOFLEX Jyen. Originally published on February 5, 2026.
Separate roof high voltage from inter-car control
A pantograph-to-transformer connection and an inter-car control jumper have different electrical and mechanical duties. The first needs coordinated insulation, screening, terminations and roof installation clearances. The second may combine low-voltage circuits and communications while accommodating vehicle articulation. A common railway label does not make them interchangeable.
Select the voltage class from the railway system
In an AC cable designation U0/U (Um), U0 describes conductor-to-earth rated voltage, U the conductor-to-conductor rating, and Um the highest system voltage for which the equipment is intended. Um is not a transient peak or lightning withstand rating. The infrastructure supply, earthing arrangement, temporary overvoltages, insulation coordination and vehicle specification all affect the selection.
A 26/45 kV designation alone is not a complete pantograph-cable specification. Confirm the required impulse and power-frequency withstand, screen duty, accessories, pollution exposure and installation environment with the responsible vehicle engineer. Do not infer suitability from nominal overhead-line voltage alone.
Use each standard within its scope
EN 50382-2 covers specified high-temperature railway cable constructions, including 1.8/3 and 3.6/6 kV types. It must not be cited as automatic qualification of a 26/45 kV roof cable. A higher-voltage assembly needs the actual applicable specification and supporting test evidence. Likewise, references to EN 50264 or UIC interfaces must identify the exact part, edition and construction being supplied.
For EN 45545 fire performance, establish the vehicle’s operation and design categories and the relevant requirement set for the component. A generic HL3 phrase without the applicable requirement set and evidence is insufficient. Material fire behaviour, circuit integrity and electrical insulation withstand are separate properties; one result cannot stand in for all three.
Screened insulation and terminations
Conductor and insulation screens help control electric stress in a screened cable. Their manufacture, surface condition and continuity matter, but triple extrusion alone is not proof of a partial-discharge limit. Specify the test voltage, sensitivity, calibration, duration and acceptance criterion from the governing specification; IEC 60270 measurement methods do not impose a universal 5 pC product limit.
A simple coaxial electric-field equation can illustrate radial stress in an ideal uniform insulation layer, but it does not evaluate terminations, interfaces, voids, ageing or impulse behaviour. Dividing a quoted material breakdown strength by that ideal field does not produce a defensible service safety factor. Review the complete cable-and-accessory system instead.
Inter-car motion and connector definition
Measure the actual bend, twist, extension and minimum clearances throughout the articulation envelope, including adverse vehicle positions. Select strain relief and routing that prevent the connector from carrying cable tension. Qualification should reproduce the agreed motion, temperature and environmental exposure, with electrical checks before and after testing.
A UIC connector designation does not establish a universal conductor layout or compatibility with every train bus. Obtain the vehicle wiring diagram, pin allocation, connector variant and communication-system requirements. A general multicore control cable is not automatically a qualified data transmission cable.
Evidence to request
- A controlled drawing with cable, screen, connector and termination details; relevant voltage and thermal ratings.
- Fire and electrical test reports tied to the supplied construction and applicable standards/editions.
- Assembly motion-test conditions and results, rather than an unsupported multi-million-cycle promise.
- A real bill-of-materials mass comparison if weight savings are claimed, including changed accessories and supports.
Sources and application documentation
Source: lappitalia.lappgroup.com
Source: produkty.lappgroup.com
Discuss the application
Send the application duty, installation drawing and required acceptance criteria to TEBAOFLEX. WhatsApp: +86 185 9591 3361. Request the applicable product documentation before ordering.