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三相サージ保護デバイス（SPD）ガイド：種類、配線、および選定方法
Choose a three-phase surge protective device by network arrangement, SPD type, Uc, Up, discharge rating and backup protection. Includes 3P, 4P and 3+1 comparison.
クイックアンサー： A three-phase surge protective device (SPD) limits transient overvoltage on a three-phase AC distribution system. The right device depends on the network arrangement, voltage, lightning exposure, installation point, and equipment withstand level. A 3-pole SPD is not automatically interchangeable with a 3+1 or 4-pole arrangement.
What a three-phase SPD does
An SPD is connected to the power system to limit surge voltage and divert surge current during a short transient. It does not regulate normal voltage, correct long-duration overvoltage, or replace the circuit breaker and earthing system. IEC 61643-11:2025 covers requirements and tests for SPDs connected to AC low-voltage systems. The actual protection at equipment also depends on installation and conductor length.
Surges may arrive through a utility supply, nearby lightning, or switching operations. Protection must be considered across every conductor that can carry the transient, including the neutral where one is present.
3P, 4P and 3+1: what changes?
| Arrangement | Typical conductors considered | What to verify |
|---|---|---|
| 3P | L1, L2, L3 | Whether the installation has a neutral and whether the SPD modes match the earthing system |
| 4P | L1, L2, L3, N | Protection modes and the manufacturer’s wiring diagram |
| 3+1 | Three line-to-neutral paths plus a neutral-to-earth path | Network type, N-PE component, backup protection and approved connection diagram |
These labels describe different connection arrangements; they do not by themselves establish suitability. Confirm whether the supply is TN-S, TN-C, TT or IT, whether a neutral is distributed, and the exact device wiring diagram. Do not infer a connection from the number of modules alone.
Choose Type 1, Type 2 or coordinated stages
タイプ1 devices are evaluated for lightning-current impulse duty and may be needed at a service entrance where the risk assessment and local rules indicate direct lightning-current exposure. タイプ2 devices address induced lightning and switching surges at distribution boards. A combined タイプ1+2 device can meet both classifications when its declared ratings match the design. Sensitive downstream equipment may need a coordinated additional stage.
One large current rating is not a complete design. Check the declared impulse or discharge-current ratings against the location and coordinate the voltage protection level with the equipment withstand level and upstream/downstream SPDs.
Seven specifications to check before ordering
- System voltage and frequency: record phase-to-phase and phase-to-neutral voltage.
- Earthing and conductor arrangement: identify TN-S, TN-C, TT or IT and whether neutral is present.
- Maximum continuous operating voltage (Uc): match each protection mode to the voltage it can continuously see.
- SPD class and discharge ratings: compare Type 1 Iimp or Type 2 In and Imax using their stated test waveforms.
- Voltage protection level (Up): compare the installed protection level with the equipment’s impulse withstand level.
- Short-circuit and backup protection: check the SPD’s declared short-circuit rating and the manufacturer’s required upstream fuse or breaker.
- Monitoring and maintenance: confirm status indication, remote contact requirements, cartridge replacement procedure and inspection access.
For a practical product comparison, see Kuangya’s AC SPDシリーズをご覧ください。, including KYSPD-12.5T1+2-3P そして KYSPD-20T2+3-4P. Use each product’s current datasheet and wiring diagram to confirm a specific installation.
Installation details that affect real protection
Keep the connections from the supply through the SPD to the protective-earth bar short and direct. Long leads add voltage during a surge; Schneider Electric’s installation guide recommends a total connection length of no more than 50 cm where practical. Route phase, neutral and PE conductors together and follow the manufacturer’s conductor-size and backup-protection instructions. A qualified electrician should verify protective bonding, available fault current, isolation and local code requirements before energizing the board.
Inspect the status indicator after a significant surge and during scheduled maintenance. Replace a failed cartridge only with the specified compatible part, and investigate repeated disconnection rather than simply replacing modules.
よくある質問
Does every three-phase panel need a 4-pole SPD?
No. The correct connection depends on the distributed conductors and earthing arrangement. A three-phase system may have no neutral, and a four-module product may use different internal protection modes from a 3+1 product.
Can a breaker replace an SPD?
No. A breaker provides overcurrent protection under its declared conditions. It does not provide the same transient voltage-limiting function as an SPD; the SPD may itself require coordinated backup protection.
Is a larger kA number always better?
No. Compare ratings with the same waveform and test class, then consider Uc, Up, system configuration, available fault current and the installed connection. A high discharge rating cannot compensate for incorrect wiring or excessive lead length.
Request the right three-phase SPD
Send the distribution-board voltage, earthing system, neutral arrangement, intended installation point, lightning exposure and required Type 1/Type 2 classification when you contact Kuangya for a selection review. For PV inverter systems, also assess the separate DC and AC inverter protection paths; an AC SPD is not a substitute for a PV-rated DC SPD.
技術参考資料： IEC 61643-11:2025 and Schneider Electric’s 0.5mの総リード線長に関するガイダンス。.
