Transient overvoltage problems are not limited to the field of household power socket plugs. In low-voltage distribution systems, control cabinets, commercial buildings, industrial equipment, communication rooms, and solar/pv (PV) projects, brief surge events can cause sensitive components and the connected loads to endure extremely high voltage stress. For procurement personnel and engineers, the key issue is not whether the surge protection device (SPD) is useful, but rather which device is most suitable for the specific system design.
When choosing a surge protection device (SPD), multiple factors need to be considered comprehensively, including device type, AC or DC application scenarios, voltage level, phase configuration, polarity arrangement, discharge performance, voltage protection level, installation location, and compatibility with other protective devices. For example, a product suitable for the AC main distribution cabinet may not be suitable for the DC side of the PV string, nor may it be suitable for three-phase distribution cabinets with different neutral wire configurations.
This guide is intended for electrical engineers, electricians, distribution panel manufacturers, industrial buyers, commercial facility buyers, solar/pv buyers, and procurement teams. It explains the terms SPD and TVSS, compares the 1st, 2nd, and 3rd type SPD options, and helps you prepare clear project information before requesting technical support from OOHMAGE.
Definition: A surge protective device (SPD) is an electrical protection device used to help limit transient overvoltage in an electrical system. It is installed at selected points in the power distribution path so surge energy or voltage stress can be controlled before it damages downstream equipment.
The simplified system flow is as follows: Input power / photovoltaic (PV) source → Distribution box or combiner box → Surge protector (SPD) → Protected electrical equipment.
In B2B electrical projects, SPDs are typically used in low-voltage distribution panels, control panels, OEM electrical panels, commercial buildings, industrial systems, and solar/pv systems. Their function is to support the overall protection strategy of the device, especially in cases where lightning strikes, switch operations, grid disturbances, inductive loads, or nearby electrical events may cause transient overvoltages.
When buyers search for surge protection products, they may encounter various terms. Among these terms, there are both formal product names, as well as long-standing industry nicknames, and some broad search terms. Understanding the differences between these terms can help avoid confusion when communicating with suppliers.
| Term | Meaning | How to Use It |
| SPD | Surge protective device; the modern common technical abbreviation after definition. | Use as the main abbreviation after first writing surge protective device (SPD). |
| TVSS | Transient voltage surge suppressor; an older or still commonly used term in some markets. | Use as related terminology buyers may encounter, not as a separate product claim unless confirmed by product documentation. |
| Surge protection device | Common search phrase for the same general product category. | Use naturally as a support phrase, especially for buyers who search this wording. |
| Surge protector | Often consumer or residential wording. | Mention only when clarifying the difference between consumer plug-in devices and B2B SPD products. |
TVSS refers to Transient Voltage Surge Suppressor. In many actual business communications, when buyers inquire about SPD (Surge Protection Device) applicable to distribution panels or control cabinets, the term “TVSS” might be used. However, the usage of this term often varies depending on the market, technical documentation, and project specifications. Therefore, it would be more prudent to clearly specify the required standards, system voltage, installation location, and product type.
When dealing with content related to OOHMAGE and communicating with suppliers, it is necessary to continue using “Surge Protective Device” (abbreviated as SPD) as the main product term. “TVSS” can be used as a related search term or specification term for explanation, so that engineers and the purchasing team can link the terms used in previous projects with the current SPD selection discussions.
The surge protector (SPD) remains in a standby state under normal operating conditions. During normal usage, it should not interrupt the normal power transmission of the circuit. When a transient overvoltage event occurs, the SPD responds according to its internal design and connection method, thereby limiting the voltage stress applied to downstream devices, or dissipating the surge energy through a controlled path.
The specific action characteristics depend on SPD technology, protection mode, system grounding method, conductor arrangement, and installation location. For example, in a low-voltage distribution panel, the SPD can be connected between the phase line, neutral line, and protective grounding conductor according to the specified configuration; while in a DC photovoltaic combiner box, due to the need to consider polarity, DC voltage, and the layout of the photovoltaic array, the protection requirements are different.
A basic process can be understood in three stages:
The performance of SPD (Surge Protective Device) depends on its type, rated parameters, installation location, wire length, grounding method, backup protection, and compatibility with other protective devices. They are only one component of the coordinated protection strategy, so SPD cannot replace fuses, circuit breakers, grounding systems, insulation coordination, or standardized electrical design.
The classification of SPD (Surge Protective Device) into categories 1, 2 and 3 helps engineers deploy surge protection devices at different locations in the electrical system. The specific requirements depend on local regulations, lightning exposure risks, architectural design, upstream power supply conditions, and project risk assessment. The comparative analysis in the following text aims to provide practical reference for procurement decisions, but it cannot replace professional engineering design.
| SPD Type | Typical Position | Main Purpose | Buyer Decision |
| Type 1 SPD | Service entrance or upstream distribution. | High-energy surge current protection, often where lightning exposure or upstream surge current risk is considered. | Ask whether external lightning protection, overhead supply, or high exposure conditions apply. |
| Type 2 SPD | Main or sub-distribution board. | Limits transient overvoltage inside low-voltage installations. | Commonly considered for commercial and industrial distribution panels. |
| Type 3 SPD | Near sensitive terminal equipment. | Fine protection close to selected equipment or terminal loads. | Usually coordinated with upstream Type 1 or Type 2 SPD rather than used alone. |
Class 1 surge protection devices are typically installed at the incoming power line or at other upstream locations, i.e., the areas where high surge current exposure risks need to be considered in the design assessment. Choosing such devices is not merely due to the large scale of the building; the project team should also comprehensively evaluate lightning protection measures, power supply configuration, exposure levels, and local electrical code requirements.
A Type 2 surge protection device is often used at main or sub-distribution boards. For many commercial buildings, industrial panels, equipment rooms, and OEM panel projects, Type 2 SPD selection becomes the core discussion because it addresses transient overvoltage within low-voltage installations.
A Type 3 SPD is usually placed close to sensitive terminal equipment. It is not a substitute for upstream protection. In many coordinated designs, Type 3 protection works together with a Type 1 or Type 2 SPD so the surge stress is handled across multiple levels rather than concentrated at the final device.
For procurement, the key point is to provide systematic information. Just by the name “surge protector”, the supplier cannot responsibly select the specific model. The inquiry information should clearly specify the installation location, such as the incoming terminal, main distribution panel, distribution box, control cabinet, photovoltaic combiner box, or equipment-side protection.
When it comes to choosing between Type 1 and Type 2 surge protectors (SPDs), this is one of the most frequently asked questions by buyers. The decision is not solely based on price or physical size, but rather on the installation location, surge exposure risk, the condition of the upstream power grid, and whether the system requires multi-level coordinated protection.
| Project Situation | Usually Consider | Reason |
| Building has external lightning protection or high exposure conditions. | Type 1 or Type 1+2 SPD. | Upstream surge current risk may be higher and should be reviewed at the service entrance or upstream point. |
| Main distribution board in a commercial or industrial facility. | Type 2 SPD or coordinated solution. | Internal transient overvoltage protection is commonly required at distribution level. |
| Sensitive equipment downstream. | Type 3 SPD with upstream coordination. | Fine protection near the load is more effective when upstream surge stress has already been reduced. |
| Solar/PV system. | AC SPD and/or DC SPD depending on system side. | AC and DC protection must be selected separately according to system design. |
Therefore, when comparing Type 1 and Type 2 surge protectors (SPD), the installation location should be taken into account first. If the equipment needs to be installed at the incoming line end of a building with a risk of lightning strike, a Type 1 or a Type 1+2 composite SPD can be considered; if the equipment is used in a distribution box within a facility, a Type 2 SPD is usually the preferred choice; if there are sensitive control or communication devices downstream, adding a Type 3 protection as part of the coordinated protection design can be considered.
This section is designed to assist you in identifying the key factors for selecting surge protection equipment suppliers. The final selection and installation must be based on the project drawings, product technical specifications, and local electrical regulations, and must be reviewed and confirmed by qualified engineering personnel.
SPD for AC and SPD for DC cannot be used interchangeably. They serve different circuit scenarios respectively – AC SPD is applicable to AC power distribution systems, while DC SPD is specifically designed for photovoltaic strings, DC combiner boxes, and other DC power applications. There are fundamental differences between them in terms of voltage characteristics, polarity requirements, and protection mechanisms.
| SPD Type | Used In | Example Application | Buyer Information Needed |
| AC SPD | AC circuits and distribution systems. | Distribution boards, commercial buildings, industrial panels, AC side of solar systems. | Voltage, phase, pole configuration, earthing system, and installation point. |
| DC SPD | DC circuits. | Solar PV strings, DC combiner boxes, DC power systems. | DC voltage, polarity, PV design, string arrangement, and installation location. |
In commercial buildings, the installation location of AC surge protectors (AC SPD) is a crucial factor to consider – whether it should be placed in the main low-voltage distribution cabinet, floor distribution box, or terminal equipment distribution panel, depending on the protection strategy. For solar photovoltaic projects, they are typically deployed on both the DC side and the AC side: the DC side includes photovoltaic strings and combiner boxes, while the AC side involves the output terminals of inverters and grid connection distribution equipment.
When preparing the quotation, do not simply state “Solar system needs to be equipped with SPD” in a general way. A professional quotation should clearly specify the following technical parameters: DC voltage level, photovoltaic string design scheme, inverter box and inverter layout, AC output voltage, phase number configuration, and compliance requirements of the target market location.
Before submitting the final project details, the buyer can first review the relevant product introduction and selection pages to learn about the specific information of SPD, DC SPD and solar inverter boxes with surge protection function, so as to more accurately determine the project requirements.
The selection of three-phase surge protectors should be based on the actual electrical parameters of the three-phase system, rather than being determined solely through keyword search. Before making the selection, the following key information should be verified: whether a neutral line is configured in the system, the rated working voltage, the type of grounding system, the required protection mode, and the available installation space in the distribution panel.
Safety Warning: The following information is for reference only during the selection process and does not constitute the wiring operation procedures. The design and installation of three-phase surge protectors must be carried out by qualified electrical professionals, and must strictly comply with local regulations, approved drawings, and product technical specifications.
| System Type | Common SPD Configuration | Buyer Needs to Confirm |
| Single-phase AC | 1P+N or 2P depending on system. | Voltage, earthing system, installation point, and protection mode. |
| Three-phase without neutral | 3P depending on system. | Line voltage, earthing arrangement, panel design, and backup protection. |
| Three-phase with neutral | 3P+N or 4P depending on system. | Neutral arrangement, protection mode, panel space, and supplier documentation. |
The selection of three-phase SPDs depends on the number of phases – for systems with neutral lines and those without, the product configurations are different. The protection modes may involve phase-to-neutral, phase-to-ground, neutral-to-ground, or other combinations.
When placing an order, the following must be provided: the schematic diagram of the distribution cabinet, the configuration of phase lines and neutral lines, the nominal voltage, the type of grounding system, the type of SPD, and the compliance requirements of the target country. Only after confirmation can an accurate selection be made, especially for OEM or commercial building projects.
In discussions on electrical technology, terms such as “surge protector” (SPD), “surge arrester” and “lightning arrester” are sometimes used interchangeably. However, in specific projects, they should not be regarded as equivalent. The three terms typically correspond to different voltage levels, product categories and application scenarios, and their selection must be distinguished.
| Term | Common Use | Article Treatment |
| Surge protective device / SPD | Low-voltage surge protection product category. | Main article focus. |
| Surge arrester | Often used in power systems or broader surge protection contexts. | Adjacent term; clarify voltage level and application context. |
| Lightning arrester | Often linked to lightning protection systems or lightning surge control. | Mention carefully; do not equate every SPD with a lightning arrester. |
This distinction is particularly important when communicating with suppliers. If the buyer merely mentions “lightning arrester” in a general way, the supplier often needs to clarify whether the project requires low-voltage SPD, power system lightning arrester, or other lightning protection components. Using precise terms helps reduce quotation deviations and improves the efficiency of technical support.
The selection of surge protectors (SPDs) should be based on the system design and project documents. Before comparing prices, it is necessary to first confirm whether the low-voltage surge protectors are compatible with the electrical systems, installation locations and target market requirements in commercial applications.
Before choosing an SPD, review the following items:
The most common mistake in procurement is focusing solely on the rated parameters or the low price. For surge protectors (SPD), the key factors determining whether a product is suitable or if there is a mismatch risk often lie in deeper parameters such as system voltage, protection mode, installation location, and compatibility requirements.
The wiring diagram of the Surge Protective Device (SPD) should be regarded as an engineering document specific to a particular project, rather than a general network diagram. The wiring method of the SPD depends on the type of AC or DC system, the phase line configuration, the polarity arrangement, the grounding system, the installation location, and the manufacturer’s instructions.
In the design of a typical low-voltage distribution panel, the SPD should be installed at the selected connection point to limit the transient overvoltage to a safe level before it reaches the downstream circuit. In the three-phase SPD wiring diagram, the phase lines, neutral lines (if applicable), and protection grounding configuration must be accurately indicated; in the DC SPD wiring diagram, the polarity relationship and the design requirements of the photovoltaic (PV) system must be clearly specified.
When wiring, use the shortest and most appropriate wires possible – overly long wires will reduce the protection efficiency. Depending on the product design and the electrical system, backup protection devices may also need to be configured. Specific details should be referred to in the product data sheet and project drawings.
Qualified-electrician note: This document does not provide step-by-step installation instructions. The final design, installation, inspection and testing work must be carried out by qualified professionals in accordance with local electrical regulations, approved project documents and the OOHMAGE product manual.
Industrial and commercial surge protection devices are widely used in various electrical environments. Although the specific application scenarios do not directly determine the product selection, they help clarify the key parameters of the system that need to be verified.
| Application | Why SPD Selection Matters |
| Commercial buildings | Helps protect distribution systems and sensitive equipment from transient overvoltage. Selection depends on board level, voltage, phase, and local requirements. |
| Industrial control panels | Reduces risk to controls, automation, and machinery circuits. Selection depends on control voltage, incoming supply, and panel layout. |
| Low-voltage switchgear | Requires type, rating, pole configuration, backup protection, and coordination decisions. |
| Solar/PV systems | AC and DC sides may require different SPD products selected according to PV design and inverter arrangement. |
| Telecom / equipment rooms | Sensitive electronics often require coordinated protection close to the load as well as upstream protection. |
| OEM electrical panels | Product selection must match panel design, available space, labeling, documentation, and target market requirement. |
The selection process must closely integrate the product with the electrical design scheme. Specifically: For a telecommunications room, emphasis should be placed on protecting sensitive electronic equipment and achieving coordinated downstream protection; for a solar energy project, it is usually necessary to configure both AC and DC SPDs; for industrial control cabinets, compact DIN rail installation may be required, and technical documents compliant with the target country’s regulations should be provided. The application scenario provides the selection background, and the specific technical specifications ultimately determine the product choice.
Share these details with OOHMAGE so the team can help match a suitable surge protective device for your electrical system or project. If some information is not available, send the project drawings, panel photos, system description, or existing specification so the technical team can identify what still needs to be confirmed.
This quotation preparation method is particularly useful for OEM panel buyers and project procurement teams. It can reduce repeated communication, avoid confusion between AC and DC, and help ensure that product selection is compatible with the final application scenario, rather than merely relying on keywords in the product catalog.
The selection of SPD should be based on the system design requirements, rather than on price or product name. The key considerations include: SPD type (Type 1/2/3), AC/DC system, phase and pole number, voltage parameters, discharge performance, installation location, backup protection and grounding method, etc.
OOHMAGE offers a full range of SPD products and provides selection support. For specific recommendations, please provide details of the electrical system, target market requirements, and project drawings – the more detailed the information, the faster and more accurate the selection will be.
