DEHN DSH B TNS 255 FM Combined Lightning Current and Surge Arrester Type 1+2 for TNS Systems

With a lightning impulse current rating of 25 kA per pole (10/350 µs) and a total of 75 kA, this DEHNshield combined arrester delivers robust protection for low-voltage consumer installations at risk from direct lightning strikes. The DSH B TNS 255 FM is engineered for TNS networks, integrating Type 1 and Type 2 surge protection in a single compact unit to safeguard electrical systems against both lightning currents and switching overvoltages.

Overview

The DEHN DSH B TNS 255 FM is a high-performance surge protective device (SPD) from DEHN + SOEHNE, a global leader in lightning and surge protection. Designed for three-phase TNS power supplies, it provides a complete protection solution with a nominal voltage of 230/400 V AC and a maximum continuous operating voltage of 255 V AC. The arrester features a 4-pole configuration (3+1) with a floating changeover contact for remote monitoring, making it ideal for critical infrastructure and commercial buildings.

What stands out

• Combined Type 1+2 protection: handles both direct lightning currents and surge voltages in one device.
• High discharge capacity: 25 kA lightning impulse current per pole (10/350 µs) and 50 kA max discharge current (8/20 µs).
• Low voltage protection level: ≤1.5 kV for both L-N and N-PE, ensuring sensitive equipment remains safe.
• Remote signalling: integrated floating changeover contact enables easy status monitoring.
• Wide operating temperature range: -40 °C to +80 °C for reliable performance in harsh environments.

Technical details

• SPD Type: Type 1 + Type 2 Combined Arrester
• Network Configuration: TNS (Terra Neutral Separate)
• Nominal Voltage (U_N): 230 / 400 V AC
• Max. Continuous Operating Voltage (U_C): 255 V AC
• Lightning Impulse Current (I_imp) [L-N]: 25 kA (10/350 µs)
• Total Lightning Impulse Current (I_total): 75 kA (10/350 µs)
• Nominal Discharge Current (I_n) [L-N]: 20 kA (8/20 µs)
• Max. Discharge Current (I_max) [L-N]: 50 kA (8/20 µs)
• Voltage Protection Level (U_p) [L-N]: ≤ 1.5 kV
• Voltage Protection Level (U_p) [N-PE]: ≤ 1.5 kV
• Follow Current Extinguishing Capability (I_fi): 50 kA rms
• Response Time (t_A): ≤ 100 ns
• Number of Poles: 4 (3+1)
• Mounting Type: 35 mm DIN Rail
• Remote Signalling Contact: Yes (Floating Changeover Contact)
• Operating Temperature Range: -40 °C to +80 °C
• Degree of Protection: IP20
• Terminal Cross-Section (max): 35 mm² (solid) / 25 mm² (flexible)
• Standards: EN 61643-11 / IEC 61643-11

Our verdict

The DEHN DSH B TNS 255 FM is a top-tier combined lightning current and surge arrester for TNS systems. Its high discharge capacity, low protection level, and remote signalling make it an excellent choice for protecting sensitive equipment in commercial and industrial environments. With a wide operating temperature range and compliance with key standards, it offers reliable performance even in demanding conditions.