Overload-Protection Drop-Out Fuse Cutouts
RW10-10F / HRW10-10F – 10-12kV – 100/200A – Bimetal + Fuse Dual-Element
Dual-element fuse link cutout that protects against both sustained overload (bimetal thermal trip) and short-circuit (fuse link magnetic trip) in a single device. Eliminates the need for a separate overload relay on the transformer secondary side.
OEM / ODM – Low-MOQ samples – Type-test reports
Overview
The RW10-10F and HRW10-10F cutouts are the “dual-element” variant of the Fuse Cutout family. The key difference from the standard RW11/HRW11 is the fuse link itself: instead of a simple wire that melts only on high fault current, the F-series link contains two distinct elements in series inside the same tube.
Element 1 — Bimetal thermal strip (overload protection): A calibrated bimetallic strip responds to sustained moderate overcurrent (typically 1.3-2x rated). The strip heats, bends, and mechanically releases a spring-loaded toggle — tripping the cutout open before the transformer windings reach damaging temperatures. This is the same principle as a thermal-magnetic circuit breaker, but at medium voltage.
Element 2 — Fuse wire (short-circuit protection): Standard silver or silver-copper fuse wire sized to melt instantly on fault currents above ~3-5x rated. Arc extinction follows the normal gas-blast mechanism inside the tube.
Why this matters for transformers: A transformer overloaded at 150% of rated capacity may run for hours before failure — a standard fuse link rated at 1.5x will never blow at this level, until the transformer is already damaged. The bimetal element detects the sustained thermal stress and trips proactively. This eliminates the need for a secondary-side low-voltage circuit breaker or overload relay, simplifying the pole-top installation.
Technical Specifications
| Rated Voltage | 10-12 kV |
|---|---|
| Rated Current | 100 A / 200 A |
| Overload Trip Range | 1.3-2.0 x rated current (thermal) |
| Short-Circuit Trip | >=3-5 x rated current (magnetic/fuse) |
| Breaking Capacity | 6.3 kA (100A) / 8-12.5 kA (200A) |
| BIL | 75-110 kV |
| Power Freq Withstand | 42 kV (dry) / 30 kV (wet) |
| Creepage | 230-350 mm |
| Insulator Options | Porcelain (RW10-10F) / Polymer (HRW10-10F) |
| Fuse Link Type | Dual-element (K-type + bimetal), non-replaceable elements |
| Operating Temp | -30 to +40 C |
| Standards | GB 15166.3 / IEC 60282-2 |
Range
| Model | Export Name | Current | Insulator | Trip Type |
|---|---|---|---|---|
| RW10-10F/100 | 12kV/100A F-type | 100 A | Porcelain | Bimetal+Fuse |
| RW10-10F/200 | 12kV/200A F-type | 200 A | Porcelain | Bimetal+Fuse |
| HRW10-10F/100 | 12kV/100A F-type Polymer | 100 A | Polymer | Bimetal+Fuse |
| HRW10-10F/200 | 12kV/200A F-type Polymer | 200 A | Polymer | Bimetal+Fuse |
F-type links are matched to the cutout and must be ordered as a complete assembly. 24kV variants available on request.
Key Features
Thermal bimetal for sustained overload + magnetic fuse for short-circuit. One device replaces cutout + secondary breaker on the pole.
The bimetal operates purely on current heating — no CT, no relay, no battery. Self-powered protection ideal for remote rural installations.
Prevents cumulative thermal damage from repeated moderate overloads (common in agricultural irrigation and seasonal loads) that a standard fuse link would never catch.
The F-type eliminates one protection layer in the coordination chain. Only the high-side cutout and low-side service fuse remain to coordinate.
Tripped by overload: the tube drops open exactly as on fault, giving the same unmistakable ground-level visual indication.
Available in both insulator types. Choose polymer for coastal/polluted environments, porcelain for standard inland.
Applications
Seasonal pump loads that overload transformers for hours during irrigation season. The bimetal catches sustained 130-160% overload before winding insulation degrades.
Self-powered overload protection for pole-mounted transformers far from SCADA or substation monitoring. No control power needed.
Crushers, sawmills, and processing equipment with intermittent heavy loading that standard fuses cannot discriminate from faults.
Oil-filled distribution transformers where sustained overload accelerates oil degradation and paper insulation aging. Bimetal trip prevents cumulative thermal damage.
Frequently Asked Questions
How is the F-type different from a standard cutout?
Why not just size a smaller fuse link for overload protection?
Can I use standard K/T links in an F-type cutout?
When should I choose F-type over standard?
Need F-type Cutouts for Transformer Protection?
Tell us transformer kVA, load profile, and voltage — we will recommend the right F-type model.
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