Class I II Surge Protective Device

The Class I II Surge Protective Device is an integrated T1+T2 power surge protection solution designed for low-voltage AC distribution systems. It combines the high-energy discharge capability of a Class I lightning arrester with the fast overvoltage clamping performance of a Class II SPD, helping protect downstream electrical equipment from direct lightning current, induced lightning surges, and grid switching overvoltage. Compared with traditional separated T1 and T2 surge arresters, the integrated structure simplifies cabinet design because no external decoupling component or strict inter-stage installation distance is required.

This device is suitable for 220/380V AC 50/60Hz systems and is commonly installed at the main incoming distribution cabinet, power room, outdoor distribution equipment, and the front end of sensitive electrical systems. With a modular DIN rail design, clear status indication, and wide operating temperature range, it provides practical lightning and surge protection for commercial buildings, industrial facilities, data rooms, photovoltaic-related distribution cabinets, and precision power supply environments.

• Integrated T1+T2 protection structure for both direct lightning current discharge and induced surge voltage clamping.
• Built-in intelligent energy matching design, reducing the need for external decoupling components.
• Suitable for 220/380V low-voltage AC power distribution systems and 3P+N three-phase four-wire applications.
• High impulse current capability with T1 Iimp options of 12.5kA or 25kA using the 10/350us waveform.
• T2 discharge capacity with nominal discharge current of 20kA or 40kA and maximum discharge current of 60kA or 80kA.
• Fast response time of <=25ns and voltage protection level of <=1.5kV for effective downstream equipment protection.
• Status window shows green for normal operation and red for failure, making maintenance inspection easier.
• 35mm standard DIN rail mounting for fast installation in distribution boxes and switchgear cabinets.

A typical model configuration is SPD-T1+T2-25/440-3P+N. In this structure, T1+T2 indicates combined Class I and Class II surge protection; 25 represents the T1 nominal impulse current of 25kA; 440 indicates a maximum continuous operating voltage of 440V AC; and 3P+N refers to a three-phase four-wire system configuration. This format helps engineers select the appropriate surge protective device according to the power system, lightning risk level, and cabinet layout.

The device uses a dual protection design that combines a gas discharge tube for Class I lightning current discharge and a varistor structure for Class II surge voltage clamping. When a high-energy surge from direct lightning enters the power line, the Class I stage acts first and discharges the large impulse current to earth. When induced lightning or switching overvoltage appears on the system, the Class II stage responds quickly and clamps the voltage to a safer level. The two stages coordinate automatically, helping reduce surge stress on downstream circuit breakers, control equipment, drives, meters, communication power supplies, and other sensitive electrical loads.

• Main incoming cabinets of commercial, residential, and industrial buildings.
• LPZ0 to LPZ1 lightning protection zone interfaces in low-voltage AC systems.
• Strong-current and weak-current equipment rooms requiring coordinated surge protection.
• Outdoor power distribution boxes and electrical panels exposed to lightning risk.
• Front-end protection for precision electrical equipment, control panels, and automation systems.
• Distribution systems using TN-S, TN-C, TN-C-S, TT, or IT earthing arrangements.

Installation must be completed by a qualified electrician after the upstream power supply has been fully disconnected. The SPD should be installed after the main incoming switch of the low-voltage distribution system and fixed firmly on a 35mm DIN rail. Connect the L phase conductors, N neutral conductor, and PE grounding conductor according to the product markings. To improve protection performance, the total connection length is recommended to be no more than 0.5m, reducing lead inductance and residual voltage during surge discharge.

A suitable backup fuse or circuit breaker should be installed upstream to prevent short-circuit risk if the surge protective device reaches end-of-life failure. After energizing the system, check the status window. Green indicates normal service condition; red indicates failure and the unit should be replaced immediately.

• Inspect the device every six months or before thunderstorm seasons.
• Confirm the indicator remains green and check that terminals are tight with no abnormal heating.
• Replace the device when the indicator turns red, after a severe lightning event, or when protection failure is suspected.
• Power off before replacement and use a new device with the same specification to avoid mismatch.

Do not install, remove, or service the device while energized. Do not use the SPD beyond its rated continuous operating voltage or in overloaded systems. The device must be selected according to system voltage, earthing type, lightning exposure level, installation position, and required discharge capacity. For main distribution cabinets and high-risk outdoor power systems, a T1+T2 combined surge arrester provides a more compact and coordinated protection scheme than using separated devices without proper energy matching.

For project selection or bulk purchasing, please provide the system voltage, earthing system, pole configuration, required Iimp and Imax levels, cabinet installation position, and estimated quantity. Our team can help confirm the suitable Class I II Surge Protective Device configuration and provide technical data, quotation support, and delivery information for your electrical protection project.