1. Isolation Link Operation
ERMCO 15 KV Three Phase Fuse Cabinet
Isolation link was not properly sized from manufacture which resulted in miss-coordination with fuse.
Resulting in phase outage

2. Isolation Link Background
Used in pad mounted transformers and ERMCO fuse cabinets
Designed to operate at high fault currents
Provides extra protection during refusing and switching operations
Isolation Link is used between source side bushing and fuse. Designed to operate under high fault currents typically due to primary transformer winding fault.
Most commonly used in pad mount transformers but also used in ERMCO ECOpad. (fuse cabinet)

3. Note the location of the isolation link

4. Issues that GLE Had
The wrong size isolation link was installed at the ERMCO factory
Fuse cabinets have multiple fuse sizes based on load
The largest size isolation link should be used to coordinate with any size fuse
Fuse cabinet came installed with too small of a current rating for the application.
Third bullet only pertains to fused cabinets

5. Issues that GLE Had Cont.
If not properly coordinated with a Bay-O-Net fuse, isolation links can operate instead of the fuse
No easy way to replace isolation link after it has operated
GLE crews had to install a feed-thru on the primary side to energize the tap
To replace the isolation link the top of the tank has to be removed and the isolation link is immersed oil

6. Troubleshooting Procedures
Test for Source Voltage
Verify Continuity on Bay-O-Net fuse
Bay-O-Net Shows Continuity
Check Load Side for Fault Condition
Clear Fault
Re-energize Load Side
Upon arrival of GLE crews:
Load side of fuse cabinet showed de-energized phase and was open.
Crews patrolled UG line and at riser found faulted overhead primary
Fault was cleared and fuse cabinet was refused
After refusing, load side remained de-energized

7. Close up of the isolation link and how it attaches to the fuse holder

8. Dimensions of isolation link