Type 1, Type 2 and Type 3 are not three quality grades. They describe different SPD test duties and installation roles. A coordinated surge protection system must decide where each stage belongs, how the stages share surge energy and whether the voltage reaching the final equipment is low enough.
One SPD can be enough for a compact, low-exposure installation, but one device should not be assumed to protect an entire building or project.
Where partial lightning current may enter the electrical installation, a Type 1 or Type 1+2 SPD is normally evaluated at the origin. Type 2 SPDs are used at main or downstream distribution points to limit residual lightning-induced and switching surges. Type 3 or Type 2+3 protection is considered close to sensitive equipment when the upstream stage cannot maintain a sufficiently low protective level at the load. [1] [3] [4] [5]
The correct configuration may therefore be Type 2 only, one Type 1+2 combined SPD, separate Type 1 and Type 2 stages, or a complete Type 1–Type 2–Type 3 protection chain. The final choice depends on the project architecture, equipment withstand level, conductor routes and manufacturer coordination data.
Índice
Neste Guia
- What SPD coordination means
- Three checks that must not be confused
- When one SPD may be enough
- Where Type 1, Type 2 and Type 3 fit
- How to design the protection stages
- When Type 1 and Type 2 work together
- When equipment needs Type 3
- Distance and energy coordination
- Combined versus separate SPDs
- Worked engineering example
- Data centre, industrial, PV, EV and BESS applications
- Model-level coordination approval
- Procurement and OEM checklist
- Common coordination mistakes
- FAQ
What Does SPD Coordination Actually Mean?
SPD coordination means that two or more protection stages operate as one planned system. The upstream SPD manages the surge duty expected at its position. The downstream SPD further limits the remaining voltage without receiving more surge energy than it is designed to withstand. [1] [6]
This arrangement is also described as coordinated surge protection, cascaded surge protection or multi-stage surge protection. The purpose is not to install the maximum possible number of SPDs. The purpose is to place the required protection duty at each relevant electrical boundary.
IEC 61643-12 covers the selection, operation, location and coordination of SPDs connected to low-voltage AC power systems. IEC 60364-5-53 provides installation requirements. IEC 62305-4 addresses coordinated surge protection measures within a lightning protection zone concept. [1] [3] [4]
For basic definitions and test-waveform differences, see the separate Guia de SPD Tipo 1 vs Tipo 2 vs Tipo 3. This page focuses on how the protection stages work together.
SPD Coordination Includes Three Different Checks
The word “coordination” is often used too broadly. A project review should separate the following three questions.
The evidence column matters most during technical approval because each check requires different documents.
| Coordination check | Question to answer | Evidência necessária |
|---|---|---|
| Energy coordination between SPDs | Can the upstream and downstream SPDs share the expected surge energy without overloading either stage? | Manufacturer coordination table, tested product combination or documented decoupling condition |
| Protection coordination with equipment | Is the effective voltage reaching the equipment lower than the applicable equipment impulse withstand level? | SPD Up, connection arrangement, conductor route, equipment Uw and project protection margin |
| Fault and backup protection | Is the SPD compatible with the prospective short-circuit current and its upstream fuse or circuit breaker? | Short-circuit rating, maximum backup protection and manufacturer device-coordination schedule |
A datasheet showing only Type, Iimp, In or Imax is not sufficient to approve a complete SPD coordination plan.
Is One SPD Enough for the Whole Installation?
One SPD may be sufficient where the electrical system is compact, no Type 1 lightning-current duty has been identified, downstream circuits are short and the effective protective level is suitable for every important load.
One SPD is less likely to be sufficient where the installation has several distribution levels, long outdoor feeders, separate buildings, critical electronics or multiple conductive services entering the same equipment. [1] [4]
One SPD may be sufficient when
- No partial lightning-current duty is identified.
- There is one compact distribution board.
- Downstream conductors are short and not highly exposed.
- The effective protective level is suitable for every important load.
- No unprotected signal line bypasses the power SPD.
- The designer and SPD manufacturer confirm the arrangement.
Multiple stages should be evaluated when
- An external lightning protection system is installed.
- Partial lightning current may enter through a service.
- Main and sub-distribution boards are widely separated.
- Remote outdoor panels use long feeder routes.
- PLCs, servers or control electronics are critical.
- Switching equipment generates local transients.
Fast screening rule: if the project contains more than one lightning protection zone, a remote feeder or equipment with a lower impulse withstand than the upstream effective protective level, review an additional downstream stage.
Where Do Type 1, Type 2 and Type 3 SPDs Fit?
IEC SPD types correspond to different test duties and typical installation roles. The project should assign each device according to the surge conditions at its location rather than order the same SPD for every panel. [2] [5] [6]
| SPD stage | Typical location | Papel principal | Critical order data |
|---|---|---|---|
| Tipo 1 | Installation origin or main incoming board where lightning-current duty is expected | Discharge partial lightning current using the Type 1 test duty | Iimp, total current where relevant, Uc, Up, poles, protection modes and earthing system |
| Tipo 1+2 | Quadro principal de entrada | Meet Type 1 and Type 2 test duties within one product | Both classifications, Iimp, In, Up, backup protection and certificate scope |
| Tipo 2 | Main board, sub-distribution board, machine cabinet or equipment panel | Limit induced lightning, residual upstream and switching surges | Uc, In, Imax, Up, short-circuit conditions, poles and protection modes |
| Tipo 3 | Perto de equipamentos terminais sensíveis | Provide final voltage limiting after suitable upstream protection | Uoc or declared Type 3 duty, Up, load voltage, installation point and upstream coordination |
Type 1, Type 2 and Type 3 are different engineering roles. They are not low, medium and high product-quality levels.
How to Design Coordinated Surge Protection
- Identify where surge energy can enter. Review the external lightning protection system, incoming supply route, overhead or underground services, inter-building cables and the lightning risk assessment.
- Mark every important distribution level. Show the main low-voltage board, sub-distribution boards, UPS panels, machine cabinets, inverter panels, EV charger panels and other relevant enclosures on the single-line diagram.
- Identify critical equipment and its impulse withstand. Record PLCs, servers, control power supplies, industrial computers, inverters, chargers and other loads that may require a lower protective level.
- Select the correct SPD duty at each position. Evaluate Type 1 where lightning-current duty exists. Use Type 2 for distribution-level residual, induced and switching surges. Evaluate Type 3 close to sensitive loads where final-stage protection is required.
- Check the effective protective level. Do not compare the equipment withstand only with the SPD datasheet Up. Include voltage contributed by the connection arrangement and conductors. [3] [7] [12]
- Verify energy coordination between stages. Confirm whether the selected devices are tested as a coordinated combination, require conductor impedance or require an external decoupling component. [1] [6]
- Verify short-circuit and backup protection conditions. Check the prospective short-circuit current, the maximum permitted backup fuse or circuit breaker and the model-specific installation instructions.
- Review every conductive service. An AC power SPD does not protect Ethernet, RS485, 4–20 mA, coaxial, telephone or other signal circuits entering the same equipment. [4]
When Do Type 1 and Type 2 SPDs Work Together?
Type 1 and Type 2 coordination is evaluated where the installation must manage both lightning-current duty and a lower residual voltage for downstream distribution or equipment.
The Type 1 stage addresses the surge duty expected at the origin. A downstream Type 2 stage further limits the remaining voltage and handles switching or induced surges occurring after the origin. [5] [6]
| Condição do projeto | Initial configuration direction | What still requires confirmation |
|---|---|---|
| Type 1 and Type 2 duties are required at the same main board | Evaluate a Type 1+2 combined SPD | Iimp, In, Up, earthing arrangement, short-circuit conditions and certificate scope |
| Type 1 is installed at the origin and a separate downstream board exists | Type 1 at origin plus Type 2 downstream | Energy coordination, cable route, conductor impedance and manufacturer requirements |
| No Type 1 lightning-current duty is identified | Type 2 at the main distribution board may be appropriate | National rules, risk assessment, equipment withstand and downstream circuit layout |
| Remote machine, outdoor cabinet or separate building | Upstream protection plus an additional Type 2 at the remote distribution point | Feeder exposure, bonding, earthing, conductor route and signal-line entries |
Type 1 and Type 2 are complementary stages. A Type 1 rating does not automatically provide the final protective level required by every downstream load.
Does Sensitive Equipment Need a Type 3 SPD?
Not every electronic device requires a separate Type 3 SPD. Type 3 should be evaluated where the upstream protection cannot be shown to maintain an acceptable voltage at the equipment terminals.
Type 3 is normally used as a final stage close to the protected load and should be coordinated with suitable upstream Type 2 or Type 1+2 protection. It is not a substitute for service-entrance or distribution-board protection. [5] [6]
Evaluate Type 3 when
- The equipment has a low impulse withstand level.
- The load is critical, expensive or difficult to replace.
- The equipment is far from the nearest distribution SPD.
- The downstream cable may receive additional induced surges.
- Local switching transients occur close to the equipment.
- The equipment manufacturer specifies point-of-use protection.
A separate Type 3 may be unnecessary when
- A suitable Type 2+3 device is already installed close to the load.
- The upstream SPD and conductor arrangement provide a verified protective level.
- The equipment has documented integrated surge protection.
- The equipment withstand level is adequate for the verified residual voltage.
Significado do comprador: request the Type 3 coordination condition, not only the Type 3 datasheet. The supplier should identify the compatible upstream SPD and any distance or decoupling requirement.
SPD Distance and Energy Coordination
Distance affects two different parts of the protection design. These should not be combined into one simplified “10 m rule.”
Distance from the SPD to the protected equipment
A long conductor between an SPD and the protected equipment can receive additional induced surges. The conductors also contribute voltage during a fast surge current. Guidance based on IEC installation principles commonly uses approximately 10 m as a point at which additional protection close to the load should be considered. [3] [7]
This does not mean that every circuit longer than 10 m automatically requires a Type 3 SPD. The equipment withstand, conductor route, electromagnetic environment and effective upstream protective level still require review.
Distance between upstream and downstream SPDs
Cable impedance between SPD stages can influence how surge energy is shared. However, there is no universal separation distance that guarantees coordination for every Type 1, Type 2 and Type 3 product combination.
Some product families are tested for close installation. Some combined devices coordinate multiple test duties internally. Other combinations may require conductor impedance or an external decoupling component. The applicable manufacturer coordination data must determine the arrangement. [1] [6] [11]
Do not specify “10 m between every SPD” as a universal purchasing condition. Ask whether the proposed devices are tested as a coordinated combination, whether external decoupling is required and whether additional protection is needed near remote equipment.
SPD connection leads are a separate issue
The conductors connecting each SPD to the live conductors and protective earth should be short, direct and installed according to the applicable standard and manufacturer instructions. Excessive connection length can increase the effective voltage reaching the protected equipment. [3] [7]
See the separate SPD connection length and 0.5 m installation guide for detailed lead-length considerations.
Combined SPD or Separate Protection Stages?
A combined SPD is tested for more than one duty within one product. Common examples include Type 1+2 and Type 2+3 devices.
| Configuração | Main advantage | Limit that must be checked |
|---|---|---|
| Type 1+2 combined SPD | Provides both test duties at one installation point and avoids coordination between two separate products at that position | Does not automatically protect remote distribution boards or sensitive equipment |
| Separate Type 1 and Type 2 SPDs | Allows the stages to be installed at different distribution levels | Energy coordination and any separation or decoupling requirement must be documented |
| Type 2+3 combined SPD | Can provide distribution and final-stage duties close to sensitive equipment | An upstream Type 1 or Type 2 stage may still be required according to project exposure |
A combined classification describes the tested duties of one product. It does not prove that an entire building is protected from one installation point.
Worked Example: Main Board, Machine Panel and PLC Cabinet
The following is an illustrative engineering example. It is not a real customer project and it does not specify mandatory product ratings.
Illustrative system layout
- Main LV board: Type 1 or Type 1+2 duty should be evaluated because partial lightning current has been identified at the installation origin.
- Machine panel: an additional Type 2 SPD should be evaluated because the panel is remote from the origin and may be exposed to residual or induced surges along the feeder.
- PLC cabinet: Type 3 or Type 2+3 protection should be evaluated if the effective protection from the machine-panel SPD is not low enough for the PLC power supply and connected electronics.
- Signal circuits: Ethernet, RS485 and sensor conductors entering the PLC cabinet require a separate interface review. The power SPDs do not protect these circuits.
- Approval condition: the exact SPD models, Up values, backup protection and energy coordination must be confirmed from manufacturer documentation before the configuration is released.
Conclusão de engenharia: the distances do not automatically prove that three SPD types are mandatory. They show why the designer must verify the origin duty, downstream surge exposure, equipment withstand and model-level coordination instead of ordering one high-current SPD for the complete system.
How to Judge SPD Coordination in Different Projects
The following examples are initial engineering directions. They are not universal bills of materials. Final configurations must follow the project single-line diagram, adopted standards and equipment instructions.
| Aplicação | Abordagem típica de proteção | Additional coordination checks |
|---|---|---|
| Data centre | Origin protection where Type 1 duty applies, followed by Type 2 at important UPS, bypass or distribution points and final protection where sensitive equipment requires it | Redundant feeds, UPS operating modes, PDU routes, rack distance, network lines and monitoring circuits |
| Industrial control system | Main-board protection followed by Type 2 at machine or control cabinets; final protection may be required near PLCs or sensitive power supplies | VFD switching, motor circuits, 24 V DC supplies, sensors, RS485, Ethernet and equipotential bonding |
| Solar PV system | Coordinate AC and PV DC protection separately. Use PV-specific SPDs on the DC side and assign Type 1 or Type 2 duty according to the lightning protection concept | Maximum PV voltage, Ucpv, inverter location, DC cable route, LPS relationship and PV-specific standards |
| EV charging project | Review the site incomer, charger distribution board and individual charging equipment as separate protection points | Outdoor feeder exposure, EVSE instructions, national rules, communication circuits and IEC 60364-7-722 |
| BESS and PCS | Review grid-side AC, PCS, auxiliary AC, battery-side DC and monitoring circuits independently | Maximum DC voltage, grounding concept, PCS internal protection, fault-current conditions and communication interfaces |
A coordinated power SPD system protects only the power conductors on which it is installed. Data, control and communication interfaces require their own review.
PV SPD selection and coordination are specifically addressed by IEC 61643-31 and IEC 61643-32. [9] EV charging installations should also be checked against IEC 60364-7-722 and the EVSE manufacturer’s instructions. [10]
How to Approve the Actual SPD Model Combination
A general article can explain the coordination logic. It cannot prove that two specific SPD models are energy coordinated. Model-level approval requires product-specific evidence.
This distinction is important because different technologies and product families can require different separation distances, decoupling components or upstream and downstream combinations. A coordination condition published for one manufacturer’s models must not be transferred to another manufacturer’s products. [11]
| Proposed configuration | Approval status | Minimum evidence before release |
|---|---|---|
| One combined Type 1+2 SPD at the origin | Document check | Model-specific Type 1 and Type 2 classification, Iimp, In, Up, Uc, short-circuit conditions and backup protection |
| Separate Type 1 and Type 2 SPDs from the same product family | Coordination confirmation | Manufacturer coordination table or written statement covering the exact upstream and downstream models |
| Type 2 followed by Type 3 or Type 2+3 | Protection confirmation | Upstream compatibility, effective protection level, distance condition and protected-equipment withstand |
| SPDs from different manufacturers | Project assessment | Written compatibility guidance, engineering calculation or suitable laboratory or field validation |
| Alternative SPD replacing an approved project model | Full re-evaluation | Type, Uc, Up, discharge ratings, fault conditions, dimensions, wiring, certificate scope and coordination data |
Procurement rule: never infer coordination from similar Type labels, similar kA ratings or similar external dimensions.
Professional boundary: LEEYEE model recommendations should only be released after the exact system information and applicable coordination documents have been reviewed. Unverified coordination distances or compatibility claims should not be added to an OEM datasheet or project submittal.
O que os compradores devem confirmar antes de fazer um pedido
Do not request only “one Type 1 SPD” or “one Type 2 SPD.” Send enough information for the supplier to review the complete protection chain.
Project information to provide
- Single-line electrical diagram;
- Nominal and maximum operating voltage;
- AC, PV DC, battery DC or signal application;
- TN-S, TN-C-S, TT, IT or other earthing arrangement;
- External lightning protection system details;
- Incoming supply and lightning exposure;
- Main and downstream board locations;
- Approximate conductor lengths between boards and loads;
- Required SPD Type or combined classification;
- Uc, Up, Iimp, In, Imax or Uoc requirements;
- Prospective short-circuit current;
- Upstream fuse or circuit-breaker details;
- Number of poles and protection modes;
- Equipment impulse withstand where available;
- Required standards and certification markets;
- Remote signalling requirement;
- OEM label and packaging requirements;
- Quantity and sample-approval process.
Documents to request from the SPD supplier
- Datasheet for every proposed SPD stage;
- Installation instructions and wiring arrangement;
- Manufacturer coordination table or written coordination statement;
- Required distance or decoupling conditions;
- Maximum backup fuse or circuit-breaker data;
- Model-specific certificate or test-report scope;
- Dimensions, terminal capacity and remote-contact information;
- Sample validation plan for OEM or project approval.
Mixing brands requires additional verification. Type labels alone do not prove energy coordination. Where upstream and downstream SPDs come from different manufacturers, obtain written compatibility guidance or complete a project-specific engineering assessment.
Confirm the Complete SPD Configuration
Send your single-line diagram, system voltage, earthing arrangement, panel locations, conductor lengths and required standards for technical review.
LEEYEE provides surge protection selection and OEM configuration support through CNSPD, LEEYEE’s surge-protection-focused platform for global technical buyers.
Common SPD Coordination Mistakes
Choosing only by the largest kA value
Iimp, In and Imax represent different test duties. A larger number does not correct the wrong SPD type, Uc, Up, protection mode or installation position.
Assuming a Type 1 SPD protects every downstream load
Type 1 manages lightning-current duty at its installation point. Additional Type 2 or Type 3 stages may still be required to achieve the necessary downstream protective level.
Installing Type 3 without suitable upstream protection
Type 3 is final equipment protection. It should not be selected as the primary protection device for the service entrance or main distribution board.
Applying one 10 m rule to every situation
Distance from an SPD to equipment and distance between two SPD stages are different issues. Product-specific coordination data remains necessary.
Comparing equipment withstand only with datasheet Up
The installation arrangement and connecting conductors affect the effective voltage that can reach the equipment.
Copying another manufacturer’s coordination table
A model-specific distance or compatibility table applies only to the stated products and conditions. It cannot be transferred to another SPD family without verification.
Ignoring short-circuit and backup protection
Surge-energy coordination does not replace verification of prospective short-circuit current, backup protection and disconnector requirements.
Protecting only the AC power line
Ethernet, RS485, sensor, coaxial and other conductive circuits can bypass the power SPD and carry a transient into the same equipment.
SPD Coordination FAQ
Do all installations need Type 1, Type 2 and Type 3 SPDs?
No. The required stages depend on lightning-current exposure, distribution layout, conductor routes, equipment sensitivity and the rules adopted for the project. Some compact installations may use Type 2 only. Other projects may need Type 1+2 at the origin and additional Type 2 or Type 3 protection downstream.
Can a Type 1+2 SPD replace separate Type 1 and Type 2 devices?
It can provide both test duties at one installation point. It does not automatically replace downstream protection for remote panels, long feeders or sensitive equipment.
Must Type 1 and Type 2 SPDs always be separated by 10 metres?
No. There is no universal 10 m separation rule for every SPD combination. The required arrangement depends on SPD technology, manufacturer testing, conductor impedance and whether external decoupling is required.
Does equipment more than 10 metres from an SPD need another SPD?
Additional protection should be evaluated because long conductors can receive induced surges and increase the effective voltage at the load. The final decision depends on the equipment withstand level, conductor route, protective level and applicable installation rules.
Can Type 3 be installed alone?
Type 3 is intended as final-stage protection close to sensitive equipment. It should be coordinated with suitable upstream Type 2 or Type 1+2 protection rather than used as the main installation SPD.
Can SPDs from different manufacturers be coordinated?
They may be usable in the same project, but compatibility must not be assumed from the Type labels. Obtain written coordination information or complete a project-specific engineering assessment.
Does an SPD built into an inverter, UPS or EV charger remove the need for an external SPD?
Not automatically. Confirm the internal SPD classification, ratings, protection modes, replaceability and coordination limits with the equipment manufacturer. Protection may still be required at the installation origin or distribution board.
Can one high-current SPD replace a coordinated protection system?
Not necessarily. A high discharge-current rating only describes part of the device duty. It does not prove that the protective level is low enough at remote equipment or that exposed downstream circuits are covered.
What is the most important SPD coordination parameter?
There is no single parameter. Correct coordination depends on SPD test duty, Uc, Up, energy-sharing conditions, conductor arrangement, equipment withstand, earthing system, short-circuit conditions and backup protection.
Referências
- International Electrotechnical Commission, IEC 61643-12:2020, Low-voltage surge protective devices — Part 12: Surge protective devices connected to low-voltage power systems — Selection and application principles. Página de publicação oficial da IEC.
- International Electrotechnical Commission, IEC 61643-01:2024 and IEC 61643-11:2025, General requirements and test methods for surge protective devices connected to AC low-voltage power systems. IEC 61643-01; IEC 61643-11.
- International Electrotechnical Commission, IEC 60364-5-53:2019+AMD1:2020+AMD2:2024, Low-voltage electrical installations — Part 5-53: Selection and erection of electrical equipment. Official IEC consolidated publication page.
- International Electrotechnical Commission, IEC 62305-4:2024, Protection against lightning — Part 4: Electrical and electronic systems within structures. Página de publicação oficial da IEC.
- Institution of Engineering and Technology, Dispositivos de proteção contra sobretensões (DPS). Technical guidance covering SPD types, typical locations and coordinated protection. IET technical article.
- Phoenix Contact, Fundamentals for Surge Protection. Guidance on lightning protection zones, Type 1, Type 2 and Type 3 application positions and coordinated protection concepts. Official technical guide.
- DEHN, Surge Protection in Low-Voltage Switchgear Assemblies. Guidance on effective protective level, conductor length and downstream coordinated protection. Official technical document.
- BEAMA, Guide to Surge Protection Devices: Selection, Application and Theory. BEAMA resource page.
- International Electrotechnical Commission, IEC 61643-31:2018 and IEC 61643-32:2017, Surge protective devices for photovoltaic installations — Requirements, selection and application principles. IEC 61643-31; IEC 61643-32.
- International Electrotechnical Commission, IEC 60364-7-722:2018, Low-voltage electrical installations — Requirements for supplies to electric vehicles. Página de publicação oficial da IEC.
- Schneider Electric, CA903014E, Version 2.7, 2025, Coordination of Surge Protective Devices for Commercial and Industrial Buildings. Product-specific coordination schedules illustrating that coordination conditions depend on the exact device combination. Official Schneider Electric document page.
- International Electrotechnical Commission, IEC 60664-1:2020+AMD1:2025, Insulation coordination for equipment within low-voltage supply systems — Part 1: Principles, requirements and tests. Official IEC consolidated publication page.
This article provides general engineering and procurement guidance. The final SPD arrangement must be confirmed against the standards and national rules adopted for the project, the lightning and overvoltage risk assessment, the electrical single-line diagram, equipment manufacturer instructions and model-specific SPD coordination documentation. No coordination distance, model compatibility or certificate scope should be assumed without verification.
