1. CURRENT LIMITING FUSES FOR OVERHEAD TRANSFORMERS

2. Why consider current limiting fuses?
Originally a question on overhead transformer fusing.
Led to a suggestion to investigate using smaller fuses to limit oil spills from overhead transformers.
Evolved into a suggestion to utilize current limiting fuses to limit oil spills from internal faults in overhead transformers.

3. Oil Spills- Causes Year Overload Internal Fault 2003 273 133

4. Current Limiting Fuses
Looked at utilizing Cooper NXII CL fuse mounted either at the cutout or on the transformer.
Cost ranged from approximately:
$ 25/ for up to 12 amp
$ 30/ for amp
$ 40/ for amp

5. Survey Informal survey of SWEDE and EEI member companies.
Only three respondents used current limiting fuses for overhead transformers (CPS, Centerpoint & Exelon).
Among reasons cited included controlling catastrophic failures.

8. Findings
Current Limiting fuse could alleviate some oil spills due to internal fault.
Number would be limited.
Fault Current limited by reactors
Dependent on degree of protection
The cost of adding CL fuses to all overhead units was greater than the anticipated cost of oil spills.
Possible operating issues.

9. QUESTIONS?