Bushing Draw Lead Extension
Custom-machined extensions for transformer bushing draw leads. Made to your dimensions when a replacement bushing sits higher than the original and the existing draw lead won’t reach.
- ApplicationPower transformer bushings, all makes and voltage classes
- MaterialsCopper, brass, or steel body, to customer spec
- ConfigurationExternal thread top (male) · Internal thread bottom (female)
- AvailabilityMade to order, customer-supplied dimensions
- DocumentationMaterial certification available on request
What is a bushing draw lead extension?
The draw lead is the copper conductor that passes through the center of a transformer bushing, connecting the winding terminal inside the tank to the top terminal of the bushing above the tank cover. The draw lead threads into the bottom of the bushing stem at one end and connects to the winding at the other.
When a replacement bushing has a taller overall height than the original, which happens frequently when sourcing a cross-manufacturer replacement or a bushing with an updated voltage rating, the draw lead is too short to close the gap. A draw lead extension threads onto the existing draw lead and adds the length needed to reach.
When you need one
The most common trigger is a bushing changeout where OEM bushings are no longer available and the replacement is dimensionally different. Even a 2–3 inch height difference makes the original draw lead unusable. Rather than sourcing an entirely new draw lead assembly, which may itself be unavailable, a properly machined extension solves the gap with correct thread engagement and full conductor cross-section.
Extensions are also used in restoration work when the original draw lead is corroded or damaged at the top and needs to be shortened, then extended back to the correct overall length.
What to send us for a quote
Because these are machined to your specific dimensions, we need four pieces of information:
- Top thread spec, outside diameter, thread pitch (TPI or metric), and length of the threaded section that engages the bushing stem
- Body diameter and overall length, the cylindrical shank dimensions
- Bottom thread spec, inside diameter and pitch of the female thread that accepts the existing draw lead
- Material preference, copper, brass, or steel body
If you have the failed or removed draw lead in hand, photos with a reference measurement (tape measure or caliper) are enough for us to work from. We can also work from drawings or dimensional specs from the bushing manufacturer.
Materials
Copper is the most common choice for the body, it matches the conductivity of the draw lead and requires no derating. Brass is used when corrosion resistance is the priority and slightly lower conductivity is acceptable. Steel is used in mechanical applications where strength is the binding constraint. Thread profiles are machined to match the existing draw lead and bushing stem exactly.
Send us the thread specs, body dimensions, and material preference, or just photos of the bushing and existing draw lead with a reference measurement. We’ll reply with a quote and lead time within one business day.