Fuse-Link Fault Sensors SF, DS and DE for Oil Transformers
DENCO publishes three fuse-link fault sensor ranges for oil transformers: SF (DSF10 to DSF140, 10A to 140A), DS (DDS3 to DDS50, 3A to 50A) and DE (DDE5 to DDE65, 5A to 65A). Each has a minimum melting curve and a total clearing curve, drawn at 60Hz and 25°C ambient in the oil transformer without initial load.
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The SF range covers 10, 15, 25, 40, 65, 100 and 140A (Graphs 01 and 02). The DS range covers 3, 8, 15, 25 and 50A (Graphs 03 and 04). The DE range has the finest steps: 5, 6, 8, 12, 15, 25, 40, 50 and 65A (Graphs 05 and 06). The catalog number is the range prefix followed by the ampere rating, so DDE12 is the 12A DE fault sensor.
The catalog also prints a dimension page for the oil-submersible transformer back-up fuse, to ANSI/IEEE C37.41-2016, with recommended single-phase and three-phase transformer Bay-O-Net and FTH combinations. Ask DENCO for the combination that fits a given transformer.
Specifications
| Parameter | Value |
|---|---|
| SF ratings | 10, 15, 25, 40, 65, 100, 140A (DSF10 to DSF140) |
| DS ratings | 3, 8, 15, 25, 50A (DDS3 to DDS50) |
| DE ratings | 5, 6, 8, 12, 15, 25, 40, 50, 65A (DDE5 to DDE65) |
| Curve basis | 60Hz, 25°C ambient, in the oil transformer without initial load |
Construction and options
- Three sensor ranges: SF, DS, DE
- Minimum melting and total clearing curve for each range
- Back-up fuse dimension drawings (p.88)
Catalog numbers in this series
| Catalog no. | Availability | Last reviewed |
|---|---|---|
| DSF10 | Active | 2026-08-27 |
| DSF15 | Active | 2026-08-27 |
| DSF25 | Active | 2026-08-27 |
| DSF40 | Active | 2026-08-27 |
| DSF65 | Active | 2026-08-27 |
| DSF100 | Active | 2026-08-27 |
| DSF140 | Active | 2026-08-27 |
Applications
- Oil transformer protection
Standards and equivalents
- Oil-submersible transformer back-up fuse: Standard ANSI/IEEE C37.41-2016
Wording is the catalog’s own. “In accordance with” a standard is not the same as certified or listed to it.
Curves and drawings
The catalog prints the following for this series: sf minimum melting (graph 01), sf total clearing (graph 02), ds minimum melting (graph 03), ds total clearing (graph 04), de minimum melting (graph 05), de total clearing (graph 06), back-up fuse dimension drawings (p.88). This series is on pp.82–88 of the January 2025 DENCO catalog. Access the catalog or ask for the drawing or curve you need.
Technical review
Specifications on this page are quoted from DENCO’s product catalog. Confirm any rating against DENCO engineering before specifying.