DEHN DG TT 20 340 Type 2 Surge Arrester 4-Pole for TT and TN-S Systems

The DEHN DG TT 20 340 stands apart from conventional surge arresters by integrating a four-pole varistor-based design specifically engineered for TT and TN-S earthing systems. Unlike generic Type 2 devices, it delivers a nominal discharge current of 20 kA (8/20 µs) and a maximum discharge current of 40 kA, ensuring robust protection for low-voltage installations. Its compact thermoplastic enclosure, rated UL 94 V-0, mounts directly onto a 35 mm DIN rail, making it a straightforward upgrade for distribution boards.

Highlights

• Type 2 surge protective device (SPD) per EN 61643-11 and IEC 61643-11
• 4-pole configuration for three-phase systems with neutral
• Maximum continuous operating voltage Uc: 340 V AC
• Voltage protection level Up ≤ 1.5 kV for sensitive equipment safety
• Visual fault indication via green/red flag for quick status checks
• No follow current, enhancing reliability and reducing stress on upstream protection

In daily use

Installed at the main distribution board, the DEHNguard DG TT 20 340 continuously monitors for transient overvoltages. When a surge occurs—whether from lightning or switching operations—the varistor elements respond within 25 nanoseconds, diverting excess energy to earth. The device is designed for TT and TN-S earthing arrangements, where the neutral and protective earth are separated, ensuring correct operation without unwanted tripping. Its short-circuit withstand capability of 50 kA (RMS) and compatibility with back-up fuses up to 125 A gG allow it to be integrated into existing installations with confidence.

Full specifications

• SPD type: Type 2
• Earthing system compatibility: TT, TN-S
• Number of poles: 4
• Maximum continuous operating voltage (Uc): 340 V AC
• Nominal discharge current (In) (8/20 µs): 20 kA
• Maximum discharge current (Imax) (8/20 µs): 40 kA
• Voltage protection level (Up): ≤ 1.5 kV
• Response time (tA): ≤ 25 ns
• Short-circuit withstand capability (Isccr): 50 kA (RMS)
• Max. back-up fuse (gG): 125 A
• Operating temperature range: -40 °C to +80 °C
• Mounting type: 35 mm DIN rail
• Enclosure material: Thermoplastic, UL 94 V-0
• Degree of protection: IP20
• Standards: EN 61643-11, IEC 61643-11
• Technology: Varistor-based
• Fault indication: Visual (green/red flag)
• Follow current extinguishing capability: No follow current

Final note

With its high discharge capacity, fast response, and suitability for TT and TN-S systems, the DEHN DG TT 20 340 is a reliable choice for protecting low-voltage installations from surge damage.