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AC Surge Protection Devices for Power Distribution | Type 1, 2, 3 SPD | 275V-440V
KRIPAL offers a diverse range of modular DC Surge Protective Devices (SPDs).
KRIPAL manufactures AC surge protective devices (AC SPDs) in the UKD1 series for low-voltage power distribution systems, protecting electrical and electronic equipment against transient overvoltages caused by lightning strikes and utility switching operations. Available in Type 1, Type 2 and Type 3 classifications per IEC 61643-11, these SPDs are rated for maximum continuous operating voltages of 275V and 385V AC with nominal discharge currents from 20kA to 100kA (8/20 microsecond waveform). The UKD1 uses metal oxide varistor (MOV) technology with a built-in thermal disconnector that isolates the MOV at end-of-life, and a pluggable module design that allows hot-swap replacement without disconnecting the power supply. A green-to-red visual status indicator and an optional remote signaling contact (changeover) provide local and remote SPD health monitoring. Compliant with IEC 61643-11 and EN 61643-11, KRIPAL AC SPDs are installed at main distribution boards, sub-distribution boards and at the equipment level to form a coordinated three-stage surge protection scheme.
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SPB Series AC Power Surge Protector 3Pole 280V SPD 30kA~60kA Surge Arrester
The SPB Series Class B SPD is designed for 50/60Hz AC systems up to 1000V, supporting TT, IT, TN-S, TN-C-S, and PV AC/DC power networks.
Ask a QuoteAC SPD Selection Guide: Protecting Power Distribution from Surge Damage
An AC surge protective device diverts transient overvoltages from the power conductors to earth, limiting the residual voltage (Up) that reaches downstream equipment to a level below its impulse withstand voltage. Lightning electromagnetic pulses (LEMP) couple into power lines through direct strikes to overhead lines or induced voltages from nearby strikes, generating impulses of 10/350 microseconds (Type 1) or 8/20 microseconds (Type 2/3). A coordinated SPD scheme places a high-energy Type 1 SPD at the service entrance, a lower-energy Type 2 SPD at the sub-distribution board, and a Type 3 SPD at sensitive equipment outlets, cascading the surge energy dissipation so that each stage reduces the surge to a level the next stage can handle. This selection guide covers SPD type, voltage protection level and installation location.
UKD1 AC SPD Series Technical Specifications
SPD Type Selection: Where to Install Each Type
Type 1 SPDs (tested with 10/350 microsecond impulse) are installed at the main distribution board where the supply enters the building, handling the direct energy of a lightning strike to the power line. Type 2 SPDs (8/20 microsecond) are installed at sub-distribution boards, handling the residual surge energy that passes through the Type 1 SPD plus induced surges from nearby strikes. Type 3 SPDs are installed at the equipment outlet, providing the final protection stage for sensitive electronics. The protection levels must be coordinated: the Type 1 Up must be below the Type 2 withstand, the Type 2 Up below the Type 3 withstand, and the Type 3 Up below the equipment impulse withstand voltage (typically 1.5kV for Category I equipment). The minimum conductor cross-section for SPD connection is 6 sq mm for Type 1 and 2.5 sq mm for Type 2/3, with the connecting leads kept shorter than 0.5 meters total length.
System Voltage and SPD Uc Selection
The SPD maximum continuous operating voltage (Uc) must be at least 1.1 times the nominal system voltage for TN systems and 1.6 times for IT systems (to withstand the phase-to-phase voltage that appears on one phase during an earth fault on another phase). For a 230/400V TN system, Uc of 275V AC phase-to-neutral is standard. For a 230/400V IT system or a 277/480V North American system, Uc of 385V AC is required. The UKD1 is available in 1P (single-phase), 2P (single-phase with neutral), 3P (three-phase without neutral) and 4P (three-phase with neutral) configurations, with each pole connected between a phase conductor or neutral conductor and the protective earth (PE) busbar. The neutral-to-earth SPD (N-PE) is typically a higher-energy Type 1 device because it must handle surge currents from all three phases combined.
Pluggable Module and End-of-Life Management
Each UKD1 MOV module is a pluggable unit with a mechanical coding key that prevents insertion of an incorrectly rated replacement. The thermal disconnector inside the module opens the circuit when the MOV degrades to end-of-life (typically after absorbing multiple surge events that gradually increase the MOV leakage current and operating temperature). The visual indicator changes from green to red, and the remote signaling contact changes state to alert the building management system. The pluggable design means the electrician replaces only the degraded module, not the entire SPD base and wiring, reducing replacement time from approximately 30 minutes (disconnect and reconnect all conductors) to 2 minutes (unplug the old module, plug in the new one, no tools required except for releasing the locking tab). Replacement modules are available as spare parts with a 10-year guaranteed availability from the date of the original SPD purchase.
Backup Overcurrent Protection for SPDs
An SPD installed on the load side of the main circuit breaker still requires its own backup overcurrent protection (fuse or MCB) to disconnect the SPD if the thermal disconnector fails and the MOV goes into a short-circuit failure mode. The backup device rating is specified by the SPD manufacturer (typically 125A gG fuse for Type 1, 63A C-curve MCB for Type 2) and must coordinate with the SPD’s short-circuit withstand rating. The backup protection should be installed as close as practicable to the SPD to minimize the unprotected conductor length that could develop an arc during an SPD end-of-life short-circuit. KRIPAL provides a recommended backup protection table in the UKD1 installation manual, with the device type, rating and manufacturer part number for each SPD model.
Design Your Surge Protection Scheme
- Risk Assessment: Submit your building location and supply configuration for a lightning risk assessment per IEC 62305-2 with SPD recommendations.
- Coordinated SPD Scheme: Our engineers design a three-stage SPD scheme with UKD1 devices at the main board, sub-board and equipment level.
- Replacement Module Stock: Pre-order spare pluggable modules with your initial SPD purchase for guaranteed 10-year spares availability.
Surge Protection for Buildings, Industrial Plants and Infrastructure
KRIPAL UKD1 AC surge protective devices form a three-stage coordinated protection scheme in low-voltage power distribution systems, from the building service entrance to the equipment outlet. Each stage reduces the surge energy and the residual voltage to a level that the downstream equipment’s insulation system can withstand, protecting the investment in electrical infrastructure and connected electronic equipment.
Building Main Distribution Board Type 1 SPD
A commercial building’s main LV switchboard installs a UKD1 Type 1 SPD (100kA 10/350 microsecond) at the incoming supply, connected between each phase and the main earth bar through dedicated 16 sq mm conductors kept shorter than 0.5 meter. This SPD handles the direct energy of a lightning strike to the overhead supply line that feeds the building, dissipating up to 100kA of 10/350 microsecond impulse current to earth. The backup overcurrent protection (160A NH fuse) is coordinated so that the SPD absorbs the surge without the fuse operating, but a sustained MOV short-circuit causes the fuse to clear in under 5 seconds. The remote signaling contact is wired to the building management system for central SPD health monitoring across multiple buildings on a campus.
Floor Sub-Distribution Board Type 2 SPD
Each floor sub-distribution board in a multi-story office building installs a UKD1 Type 2 SPD (40kA 8/20 microsecond) on the incoming side of the board main switch, protecting all downstream circuits against the residual surge energy that passes through the Type 1 SPD at the main board. The Type 2 SPD has a lower Up of 1.2kV compared to the Type 1 Up of 1.5kV, providing a further reduction in the surge voltage that reaches the downstream circuits. The DIN-rail mounting allows the SPD to be installed alongside the MCBs and RCCBs in the distribution board, with the connecting leads from the SPD terminals to the busbar typically 200-300mm. The pluggable module design means the building maintenance electrician can visually check the SPD status during the monthly distribution board inspection and replace any module showing a red indicator within one scheduled maintenance visit.
Sensitive Electronic Equipment Type 3 Protection
Server racks, medical imaging equipment and laboratory instruments install a UKD1 Type 3 SPD at the equipment power inlet, providing the final stage of surge protection with an Up of 0.9kV, below the 1.5kV impulse withstand voltage of Category I electronic equipment. The Type 3 SPD is typically a plug-in unit that connects to the equipment’s IEC C13/C19 power inlet or is installed in a dedicated SPD socket outlet, protecting the equipment’s switch-mode power supply input rectifier and DC-link capacitors from overvoltage damage. For data lines (Ethernet, telephone, coaxial), a separate UKD1 data-line SPD protects the equipment’s communication interfaces against surges coupled onto the data cables from the building’s structured cabling system.
Industrial Control Panel Protection
Factory automation control panels using PLCs, VFDs and HMI touchscreens install UKD1 Type 2 SPDs on the panel’s 230V AC control power input to protect the sensitive electronics against switching surges from nearby motor contactors and welders, which generate repetitive 8/20 microsecond impulses that can degrade semiconductor junctions over time. The SPD is wired before the control transformer primary fuse so that a surge event does not cause the transformer’s inrush current to blow the fuse, disrupting the entire control system. The MOV-based SPD absorbs the surge energy and the follow current from the supply is interrupted at the next AC zero-crossing (within 10ms at 50Hz).
Renewable Energy AC Combiner Panel
Solar PV AC combiner panels aggregating multiple inverter outputs before the site transformer install UKD1 Type 2 SPDs on the AC busbar to protect the inverters’ AC output filter circuits against induced surges from nearby lightning strikes to the overhead AC collection lines. The SPD must have a Uc of at least 1.1 times the inverter’s maximum AC output voltage (typically 400V three-phase, requiring a 440V Uc rating or the 385V standard rating which accommodates the 400V + 10 percent utility voltage tolerance). The pluggable module design is valued by O&M providers who can replace a degraded SPD module during routine inverter maintenance without scheduling a separate site visit.
Protect Your Electrical Installation
- Site Survey: Our engineers can visit or video-call your site to assess the existing SPD installation and recommend a coordinated protection upgrade.
- SPD Coordination Report: Request a report showing the Up cascade from your Type 1 to Type 3 SPDs, verified against your equipment impulse withstand ratings.
- Bulk Supply for Panel Builders: Order UKD1 SPDs in bulk with your distribution boards for one-supplier logistics.
KRIPAL AC SPD Manufacturing: Multi-Stage Protection from One Factory
KRIPAL AC surge protective devices are manufactured in a dedicated production facility where metal oxide varistor discs are produced, classified by voltage rating, and assembled with thermal disconnectors and status indicators. Each SPD undergoes a combination wave impulse test on sample units from every production lot for global low-voltage power distribution surge protection.
MOV Disc Classification and Matching
Zinc oxide varistor discs are individually tested for varistor voltage (V1mA) and classified into narrow voltage bands. For multi-pole SPDs, discs are matched within plus or minus 5 percent V1mA to ensure equal voltage sharing under surge conditions. Classification data is recorded per disc and cross-referenced to the assembled SPD serial number.
Thermal Disconnector Soldering Process
The low-temperature solder joint that forms the thermal disconnector is applied using a controlled soldering process where solder alloy composition, joint volume, and heating profile are precisely managed. Sample joints from each production batch are subjected to a calibrated hot-air test to verify disconnection within the specified temperature and time window.
Type 1, Type 2, and Type 3 Classification Testing
SPDs are classified according to IEC 61643-11 test classes through impulse testing. Type 1 SPDs are tested with 10/350 microsecond waveform, Type 2 with 8/20 microsecond waveform, and Type 3 with a 1.2/50 combination wave. Production samples from each batch are verified against the published protection level (Up) for their classification.
Visual Status and Remote Signaling Verification
The green/red visual status indicator and the volt-free changeover contact for remote signaling are tested on every unit. The mechanical flag mechanism is verified for positive transition from green to red upon thermal disconnection. Remote signaling contact transition is confirmed by continuity measurement in both normal and disconnected states.
Distributor Stock Holding Programs for AC SPDs
KRIPAL supports distributor inventory programs with agreed stock levels for standard AC SPD models from Type 1 plus 2 through Type 3. Shipments are planned based on demand data, with scheduled replenishment to maintain stable supply and consistent fill rates.
Private Label and OEM Branding for AC SPDs
Laser-marked part numbers aligned with your catalog, OEM-branded packaging, and customized instruction sheets are available. Unbranded supply is provided upon request for private label production of AC SPDs.
Multi-Region Certification and Compliance Support
CE, UKCA, and IEC 61643-11 EN 61643-11 compliance documentation is provided according to target export markets. Technical documentation files are maintained and updated in line with evolving surge protection regulatory requirements.
Direct Technical Access to KRIPAL Production Engineers
Your technical team communicates with the engineers who designed and tested your AC SPDs, not a distributor’s sales engineer reading from a catalog. Application questions including SPD coordination and backup overcurrent protection receive answers within 24 hours during China business hours.
Frequently Asked Questions
Explore FAQ >Type 1 (spark gap) is required at the main distribution board if the building has external lightning protection (air termination and down conductor system) per IEC 62305. Type 2 (MOV) is required at all sub-distribution boards regardless. Type 3 provides fine protection at sensitive equipment outlets.
SPDs must trigger in sequence from upstream to downstream. The upstream SPD (Type 1) absorbs the bulk energy and triggers at a higher voltage. The downstream SPD (Type 2) triggers at a lower voltage and handles the residual let-through energy. Minimum 10m cable length or decoupling inductors between stages ensure proper energy coordination.
KRIPAL SPDs feature a green/red mechanical flag: green = functional, red = replace. SPDs with remote signaling provide an electrical contact for BMS alarm integration. Pluggable modules can be swapped without disconnecting the SPD base wiring.
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