XRNM High Voltage Current-Limiting Fuse

Medium Voltage Full-Range Fuse for Switchgear Transformer Protection (XRNM Series)

The XRNM series indoor current-limiting fuse is a compact protective device designed for medium voltage indoor switchgear, such as KYN28-12 metal-clad units or RMU cabinets. With its full-range breaking capacity, XRNM fuses interrupt both high and low fault currents, making them ideal for power transformers, voltage transformers, and ring network systems.

Compared to standard back-up fuses, XRNM fuses offer enhanced protection for distribution transformers up to 1600kVA without relying on a backup breaker for low-current faults.

Medium Voltage Full-Range Fuse for Switchgear Transformer Protection (XRNM Series)

Compared to standard back-up fuses, XRNM fuses offer enhanced protection for distribution transformers up to 1600kVA without relying on a backup breaker for low-current faults.

XRNM High Voltage Current-Limiting Fuse

🔧 Key Features

Model: XRNM (e.g., XRNM-12, XRNM-7.2)
Rated Voltage: 3.6kV / 7.2kV / 12kV
Rated Current: 6.3A – 125A
Breaking Capacity: Up to 50kA
Fuse Type: Full-range, current-limiting
Mounting: Plug-in or bolted for indoor cabinets
Standards: IEC 60282-1, GB/T 15166.2

⚙️ Technical Specifications

Parameter	Value
Rated Voltage	3.6 / 7.2 / 12kV
Rated Current	6.3A – 125A
Breaking Capacity	Up to 50kA
Power Frequency Withstand	≥42kV (1 min)
Lightning Impulse Withstand	≥75kV
Time-Current Class	gR (full-range)
Mounting Type	DIN plug-in / fixed bolt
Fuse Body Length	292mm / 442mm / 537mm
Application Environment	Indoor use, clean switchgear room

🏭 Application Scenarios

XRNM is a full-range fuse, making it especially suited for installations that lack downstream circuit breakers for coordination:

✅ KYN28-12 Metal-Clad Switchgear

Mounted inside 11kV or 6kV switchgear to protect feeders, buses, or transformers independently.

✅ Transformer Inlet Protection

Provides primary protection on MV transformer input terminals in substations or RMUs.

✅ Compact Indoor Substations

Fits neatly into limited-space installations, offering both overcurrent and short-circuit protection.

✅ Power Factor Correction Cabinets

Used in capacitor banks to avoid resonance faults and catastrophic damage.

🧱 Structural Highlights

Silver Melt Element: Designed for low let-through energy during fault clearing
Quartz Sand Filling: Quickly quenches arc energy, prevents internal pressure build-up
Precision Ceramic Tube: High dielectric strength and mechanical protection
DIN-Compatible End Caps: Ensure compatibility with standard switchgear fuse holders
Blown Fuse Indicator: Spring-loaded signal pin for external trip or alarm systems

✅ Certification & Compatibility

Fully compliant with IEC 60282-1 and GB/T 15166.2
Suitable for use in ABB, Schneider, LS Electric, or domestic brand switchgear
Supports integration with mechanical trip mechanisms for fault detection

❓ Frequently Asked Questions

• How is XRNM different from RN fuse types?
XRNM is a full-range fuse that can break both low and high fault currents; RN is typically a back-up fuse.

• Can it trip breakers automatically?
Yes, the indicator mechanism can be connected to a microswitch or shunt trip circuit.

• What’s the typical lifespan?
When used within rated limits, service life exceeds 10 years with no external damage or replacement.

• Can this fuse be used in capacitor banks?
Yes, but proper G-rated sizing is required to avoid unwanted tripping on inrush current.

• Is polymer casing available?
No, XRNM fuses use high-density porcelain bodies for consistent internal arc performance.