FN18-12D Indoor 12kV 3-Phase Gang Operated Air Load Break Switch with Earthing Device & Fuse Combination
The FN18 Series is a high-performance, 12kV indoor air insulation load break switch designed for advanced power distribution protection. Combining compressed-air and gas-produced arc extinguishing technologies, it offers a compact building block for metal-enclosed and pad-mounted switchgear applications.
Key Features:
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Reliable Protection: Safely switches load currents up to rated breaking capacity and handles short-circuit currents through its synchronized fuse-impinger system.
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Enhanced Safety: Equipped with a dedicated earthing device and optional mechanical interlocking for maximum operator security.
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Robust Construction: Features a heavy-duty steel frame, unique puffer-type arc extinguishing system, and blade-type interrupters with cast hinges.
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Optimized for Environments: Operates reliably in temperatures from -15°C to +40°C and altitudes up to 1000m.
FN18 Series Indoor High-Voltage Load Break Switch
1. Product Overview
The FN18 series is a general-purpose, three-pole, indoor high-voltage load break switch designed for advanced performance in a compact design. It is a versatile building block for metal-enclosed and pad-mounted switchgear applications with ratings from 12kV to 40.5kV.
This high-performance switch combines two reliable arc-extinguishing technologies: compressed-air and gas-produced arc extinguishing. It is an ideal solution for city network construction, high-rise buildings, and public facility power supply systems.
2. Key Features & Advantages
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Integrated Protection: When combined with fuses, it offers the advantages of both a load switch and a fuse. It can switch any load current up to the rated breaking current and handle overcurrents up to the rated short-circuit breaking current via synchronized fuse operation.
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Robust Construction: Features a heavy-duty steel frame with stand-off insulators and a unique puffer-type arc extinguishing system.
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Flexible Operation: Includes blade-type interrupters with cast hinges and jaw connectors for fast breaking and closing speeds.
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Comprehensive Functions: Despite its small volume and light weight, it offers full functionality and high reliability.
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Optional Accessories: Can be equipped with motor operators, auxiliary switches, shunt trip devices, grounding switches, and various mechanical interlocking systems.
3. Technical Parameters
| Rated Voltage | 12kV | 17.5kV | 24kV | 36kV | 40.5kV |
| Rated Current (A) | 400 / 630 / 1250 | 400 / 630 / 1250 | 400 / 630 / 1250 | 630 / 800 / 1000 | 630 / 800 / 1000 |
| Short-circuit Making Capacity (kA Peak) | 67 | 50 | 50 | 50 | 50 |
| Peak Withstand Current (kA Peak) | 82 | 82 | 82 | 66 | 66 |
| Short-time Current (kA/1s) | 31.5 | 31.5 | 31.5 | 25 | 25 |
| Impulse Withstand Voltage (kV) | 75 / 85 | 95 / 110 | 125 / 145 | 170 / 195 | 190 / 220 |
| Opening Time (ms) | 40 – 60 | 40 – 60 | 40 – 60 | 60 | 60 |
4. Usage Environment
To ensure optimal operation, the FN18 load break switch should be used within the following conditions:
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Ambient Temperature: Maximum +40°C (24-hour average ≤ +35°C); Minimum -15°C (indoor class).
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Humidity: Daily average relative humidity ≤ 95%; Monthly average ≤ 90%.
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Vapor Pressure: Daily mean value ≤ 2.2 x 10⁻³ MPa; Monthly average ≤ 1.8 x 10⁻³ MPa.
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Altitude: Maximum site altitude is 1000m above sea level.
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System Frequency: Suitable for AC 50Hz three-phase distribution systems.
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