Insulated busbars let you build smaller switchgear. Instead of relying on air clearances between bare copper bars, you shrink insulation tubing onto the busbar and reduce the phase-to-phase and phase-to-earth distances by up to 60%. But the insulation must be matched to the system voltage — and that's what MPG series is designed for.
Three Voltage Grades
The MPG series covers three voltage classes, each with different wall thickness and insulation properties:
MPG01 (1 kV) — 1.0 mm recovered wall. For LV panels, distribution boards, and general busbar insulation where the system voltage is 1 kV or below.
MPG10 (10 kV) — 2.0 mm recovered wall. For MV switchgear rated 3.6 kV to 12 kV. The most common grade for medium-voltage distribution panels.
MPG35 (35 kV) — 3.0 mm recovered wall. For switchgear rated 24 kV to 40.5 kV. The thickest wall provides the insulation needed at the highest distribution voltage.
All three grades have a LOI (Limited Oxygen Index) >30, meaning they are self-extinguishing and meet flame retardancy requirements for switchgear assemblies.
The Clearance Advantage
The primary reason to insulate busbars is to reduce the physical spacing required in the panel:
| Voltage | Bare Busbar (Phase-Earth) | Bare Busbar (Phase-Phase) | With MPG (Phase-Earth) | With MPG (Phase-Phase) |
|---|---|---|---|---|
| 10 kV | 120 mm | 75 mm | 80 mm | 70 mm |
| 35 kV | 320 mm | 200 mm | 200 mm | 150 mm |
At 35 kV, insulating the busbars reduces the panel width by up to 37% — or allows more circuits in the same panel footprint. This is particularly valuable in compact substations and modular switchgear.
Additionally, insulated busbars eliminate the risk of animal-caused faults (rodents, snakes, birds bridging phases) and reduce the arc-flash hazard during maintenance.
How to Select the Right Size
Busbar tubing must slide over the rectangular busbar, so you need to measure the diagonal:
Diagonal = √(width² + thickness²)
For example, a 40 × 10 mm copper busbar has a diagonal of √(40² + 10²) = √1700 = 41.2 mm. You need tubing with an expanded ID of at least 42-45 mm (allowing a few mm of clearance for installation). The recovered ID must be less than the diagonal to ensure a tight fit.
Our MPG10 series is available in 12 standard sizes covering busbar diagonals from 12 mm to 120 mm.
Installation
MPG tubing is flexible enough to slip over an assembled busbar, so you can insulate busbars after panel assembly. Alternatively, pre-cut lengths can be installed on individual bars before assembly.
Heat with a torch or heat gun, starting from one end and working along the bar. The tubing shrinks tightly onto the rectangular profile, conforming to the flat surfaces and edges. Allow the assembly to cool before applying mechanical load.
For busbar joints (bolted connections), use a busbar joint box or wrap-around insulation cover — the tubing must be cut at the joint to allow bolt access.
FAQ
Can MPG tubing be installed over busbars that are already mounted in the panel?
Yes, for straight runs without joints. The tubing is flexible enough to slide over a horizontal or vertical busbar section. For busbar sections with tap-offs or branches, install the tubing before connecting the branches.
Does the color matter electrically?
No — red, yellow, and green MPG tubing are electrically identical. The colors provide phase identification (L1/L2/L3 or A/B/C). Black is available for neutral or earth bars.
What about busbar joints — how do I insulate them?
Bolted joints cannot be covered with shrink tubing (you need access for maintenance). Use a snap-on busbar joint box or a wrap-around insulation cover. These are available as accessories and match the voltage class of the tubing.
Written by Long, Sales Engineer at ZZ Heat Shrink. For MPG busbar tubing specifications and size charts, see busbar insulation. For a quotation, contact our engineers.