Abstract - Partial Discharges (PDs) in fuses, resulting from electrical stress, can impair fuse functionality and equipment reliability. These discharges often arise from sharp edges of melting elements and are exacerbated in smaller transformers where reduced spacing increases electrical stress. This paper reviews the generation of PDs in fuses, highlighting the role of fuse design, mounting, and surrounding components. According to IEEE Std C37.48-2020, proper fuse installation and grounding are crucial to mitigate PDs.
Keywords—Partial Discharges, Fuses
I. GENERAL
If fuses are exposed to high electrical stress, they may produce PDs. PDs are produced from the sharp edges of the melting elements and can damage fuses by electrical erosion, resulting in impaired operation of the fuse.
The risk of PDs is heightened in smaller electrical equipment, such as smaller transformers, due to the reduced distances between the elements. This reduced spacing leads to higher electrical stress generating PDs. Since HV fuses are integral components of electrical equipment, their impact on PD measurements should be assessed.
In general, as indicated on the numeral 5.1.8 of IEEE Std C37.48-2020 “IEEE Guide and Tutorial for the Application of High-Voltage (> 1000 V) Fuses and Accessories,” suitable fuse mounting is important to avoid the onset of partial discharge. The primary area of concern is the location of ground-connected components near the fuse. If there is a relatively close ground plane, partial discharge measurements of the transformer will increase and in addition, fuse element deterioration is possible.
II. PARTIAL DISCHARGE GENERATION IN A FUSE
Melting elements are sharp live electrodes. They are often notched to withstand the recovery voltage. For arc extinction purposes, the fuse elements are embedded in sand, which is a porous dielectric filled with air. When this dielectric is exposed to a high electrical stress, electrical breakdown happens in the air gaps, leading to PDs.
IV. .PREVENTING FUSE PDS GENERATION
- The best practice is following the field grading, so that electrical field strength for PD generation is not exceeded. This is achieved mainly by adequate fuse to ground distances.
- As recommended by the numeral 5.1.8 of IEEE Std C37.48-2020, the outside surface of a CL fuse should be considered as a conductor for clearance purposes, rather than an insulator.
V. OTHER GENERAL CONCEPTS ABOUT PDS IN FUSES
- The displacement of sand grains inside the fuse can slightly change the PD level of the fuse.
- The number of PD impulses rise very fast from the inception voltage and up.
- The PD level in fuses normally decreases over time (after 5-10 minutes) at room temperature. However, at temperatures higher than 60 ℃ , this decrease is not observed.
- A larger diameter of the porcelain fuse decreases the PD level but increases the weight and the cost of the fuse.
VI. REFERENCES
- Guide and Tutorial for the Application of High-Voltage (1000 V) Fuses and Accessories, IEEE Std. C37.48-2020, 2024
- Design Tests for High-Voltage (LT 1000) Fuses, IEEE Std. C37.41-2016, 2024
- HV CL Type Distribution Fuses and Fuse Disconnecting Switches, IEEE Std. C37.47-2000, 2024.
- J. Gartner, E. Gockenback, H. Borsi, “Influences of High Voltage Fuses on Partial Discharge Measurement of Electrical Equipment”, Schering Institute of High Voltage Technique and Engineering, University of Hannover, Hanover-Germany, 1998
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