bimetallic lug

At a power distribution site, a technician named Jack was connecting a main cable to a transformer.

The cable was aluminum conductor, but he picked up a copper cable lug to terminate it.

A senior engineer stopped him immediately:

“Wait, you can’t use a copper lug here.”

Jack was confused:
“Isn’t copper better for conductivity?”

The engineer showed him another connection that had been in service for some time.
The joint was overheated and slightly burnt.

He explained:

“When aluminum conductor is directly connected to copper,
galvanic corrosion occurs.
Over time, the contact resistance increases, leading to overheating and failure.”

Then he took out a bimetallic lug (copper-aluminum terminal).

· The aluminum barrel connects to the aluminum cable

· The copper palm connects to the equipment

Jack completed the connection safely.

The next day, inside a control panel, Jack was wiring a copper conductor.
This time, he directly chose a copper lug.

Because now he understood:

“Use copper lugs for copper conductors,
use bimetal lugs when connecting aluminum to copper.”