Busbar Insulation Retrofitting: Switchgear
Insulating busbar in a cabinet that is already built is a different job from insulating it on the panel builder's bench. If you are specifying a heavy-duty busbar insulation sleeve for switchgear rather than assembling at the bench, these are the three routes that work and the inputs that decide between them.
The problem this page solves
A retrofit starts from a cabinet that already exists. The bars are bent and bolted, the phase spacing is fixed by the enclosure, and the outage window is measured in hours rather than shifts. Insulation has to go on without stripping the bus, or the project has to be built around a shutdown.
Three failures drive the work: phase-to-phase short circuit where bars pass close together, pollution flashover tracking along an exposed bar surface, and accidental contact where a panel door opens onto live copper. Animal ingress into a cabinet adds a fourth: a small carcass bridging two phases is a common cause of an unplanned trip.
Tape wraps are cheap and creep under heat cycling. Moulded shrouds fit one geometry. Heat-shrink casing conforms to the bar, holds a continuous wall and covers the bend. Size it from the system voltage and the bar dimensions, not from a catalogue range alone.
- Phase-to-phase clearance : covering the bar raises the withstand between adjacent phases, so a tight cabinet can be brought back into clearance without rebuilding it.
- Pollution flashover : the casing lengthens the surface creepage path; the anti-tracking duty is set by the compound grade and the profile, so indoor, outdoor and polluted air are different answers.
- Touch safety : a continuous wall over the accessible run removes the exposed copper that an open panel door presents.
- Animal ingress : casing plus a closed connection box removes the bridging path between phases.
Technical specification and cross-identification
Every figure below is the published value on the Wellele product page for that item. Cross-identification lists the nearest catalogue family from other suppliers, for identification only.
| Wellele Series-Type | Form | Voltage class | Size basis | Reference standards | Cross-identification |
|---|---|---|---|---|---|
| WLL-BBN-10 | Heat-shrink casing, medium-thick wall | 8.7/15 kV | Recovered ID Φ20–180 mm | ASTM D2671, -55 to +125 °C | Raychem/TE BMM · 3M BBI-A · DSG-Canusa Deray-HB |
| WLL-BBN-24 | Heat-shrink casing (catalogued at RFQ) | 15–24 kV | Quoted on bar drawing | Quoted on bar drawing | Raychem/TE BBIT · 3M BBI-6A · Deray-HBM |
| WLL-BBN-35 | Heat-shrink casing, thick wall | 26/35 kV | Recovered ID Φ30–200 mm | ASTM D2671, -55 to +125 °C | Raychem/TE BBIT (35 kV class) · 3M BBI-10A · Deray-HBT |
| WLL-BBN-SNAP | Split silicone wall, clip-on, no heat | 10 kV / 35 kV | Bar width and thickness | Confirmed at quotation | No published cross-reference |
| WLL-BBN-BOX | Moulded flame-retardant box and cover | Ambient ≤50 °C | T / X / I / S / L layout | GB/T 13539.1 | No published cross-reference |
Cross-identification is a starting point for a like-for-like enquiry, not a statement of equivalence. Competitor designations are trademarks of their respective owners. WLL-BBN-24 has no page of its own and is quoted by code.
Selected products for this application
What to send for a sized recommendation
System voltage
Bar dimensions
Run and access
Phase spacing
Environment
Outage window
Engineering questions we are asked
Can I insulate busbars that are already installed in a live cabinet?
Two routes. The snap-on split tube clips over an installed bar without heat and without disassembly, which suits switchgear that cannot be stripped down. Heat-shrink casing needs the bar accessible and a heat source, so it is normally fitted during a planned outage or at the panel builder's bench. If neither fits your outage window, send the bar drawing and we will say which route is realistic instead of bidding both.
Which voltage class do I order for an 11 kV or a 33 kV system?
Order on the system's highest voltage, not the nominal figure: an 11 kV system maps to the 8.7/15 kV casing and a 33 kV system to the 26/35 kV casing. Voltage is only half the decision, because the bar dimensions and the phase spacing in the cabinet set the wall and the profile as well.
How do I size casing for a rectangular copper bar?
Work from bar width and thickness against the recovered ID, not from the bar's diagonal. The 8.7/15 kV range covers recovered ID 20 to 180 mm and the 26/35 kV range covers 30 to 200 mm. Send width, thickness, corner radius and the run length and we return the casing size with cut lengths.
Does the insulation stop flashover in polluted or coastal air?
It lengthens the surface creepage path, which is what pollution flashover depends on, but the anti-tracking duty is set by the compound grade and the profile rather than by the fact that the bar is covered. Tell us indoor, outdoor or polluted-substation air and the pollution level you design to, and we confirm whether the standard casing grade is enough or a different construction is needed.
Can casing be used to reduce phase-to-phase clearance?
Yes, that is one of its main jobs. Covering the bar raises the withstand between adjacent phases, so a cabinet can be built tighter or an existing one brought back into clearance. The clearance figure itself has to be recalculated by your engineer, because the casing changes both the surface path and the air gap. We supply the component data for that calculation, not a system clearance claim.
Send the bar dimensions and the outage window
Voltage class, bar width and thickness, phase spacing, indoor or outdoor air, and how long the cabinet can be down. We return a sized recommendation with cut lengths, lead time and a sample.
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