Sudden electrical malfunctions, unexplained equipment damage, and even occasional electrical fires are often related to "transient overvoltages," commonly known as "surges." These invisible "electrical shocks" can be caused by lightning strikes, turning appliances on or off, or interference from the power grid, making them "invisible killers" for electrical equipment.

Surge protection device (SPD) is a "shield" specifically designed to deal with surges. It can quickly release excess electrical energy to the ground when the voltage suddenly exceeds the limit, protecting equipment from damage. Whether in industrial plants, railway substations, communication base stations, or new energy power plants, they are indispensable. Below, Anhui Jinli Electric will explain the working principle of SPDs, how to select them, and how to install them.

How does SPD work? Like a "smart security guard"

The core functions of surge protection device (SPD) are two fold: first, to limit sudden voltage spikes, and second, to divert excess current to the ground. Its operating logic is quite simple to understand; it likes a "smart security guard": When the voltage is normal, the SPD remains in "dormant" mode, with extremely high internal resistance, completely unaffected by the normal operation of electrical appliances, and we are completely unaware of its presence. However, if the voltage suddenly spikes (exceeding a predetermined safe value), special components within the SPD (such as varistors and discharge tubes) instantly conduct, reducing internal resistance to extremely low levels, acting like a "floodgate" to quickly divert the excess surge voltage to the ground. Once the voltage returns to normal, it automatically reverts to "dormant" mode, ensuring uninterrupted equipment operation.

 How to choose SPD? Remember 3 core elements: industry, parameters, environment.

 1. First, consider the industry scenario: different places have different needs.

Industrial automation systems: Industrial automation electrical systems have multiple layers, requiring "multi-layer protection"—Class I for the main distribution box, Class II for the sub-distribution boxes, and Class III for the terminal distribution boxes, ensuring comprehensive protection without blind spots; Industrial automation control systems are characterized by precise control units, complex signal links, and harsh field environments. SPD selection must consider surge protection on both the power supply and signal sides, while matching the system's voltage level, interface type, response time, and other core parameters.

Electrified railway systems:For electrified railway systems, it is necessary to strictly follow the requirements of the China Railway Corporation Transportation Bureau's "Transportation Equipment Letter [2016] No. 325" and "Transportation Equipment Letter [2017] No. 240", and deeply integrate the two core principles of lightning protection zoning and lightning protection classification as defined in GB 50057-2010 "Code for Design of Lightning Protection of Buildings" and GB 50343-2012 "Technical Specification for Lightning Protection of Electronic Information Systems of Buildings", to build a lightning protection system for electrified railways that covers all aspects and all scenarios;

New energy system: New energy system (including photovoltaic, wind power, energy storage, electric vehicle charging, etc.), as the core component of the new power system, generally integrates a large number of precision electrical and electronic equipment (such as photovoltaic modules, inverters, converters, energy storage batteries, charging piles, etc.), and is mostly deployed in high-risk areas for outdoor lightning strikes. It is vulnerable to lightning surges and power grid fluctuations, leading to equipment damage, system paralysis and even fire accidents. Surge protective device (SPD) is a core protection device, and its scientific selection directly determines the system protection effectiveness. At this time, you must choose a new energy-specific SPD, otherwise problems may easily occur.

2. Key Parameters: Don't Ignore These Numbers

* Maximum Continuous Operating Voltage (Uc): The normal voltage that the SPD can withstand over a long period. It must be higher than the system voltage (phase voltage).

* Nominal Discharge Current (In): The surge current that the SPD can repeatedly withstand. Choose according to standards and installation location.

* Impulse Withstand Current (Iimp): The ability to withstand direct lightning strikes. The higher the value, the better the lightning protection effect. Choose a higher value for outdoor areas or places with frequent lightning strikes.

* Voltage Protection Level (Up): The voltage limit that the SPD can maintain. The lower the value, the safer it is.

3. Finally, consider the installation environment:

Temperature and humidity: In humid southern regions, cold northern regions, or high-temperature factory workshops, choose SPDs that are moisture-resistant and resistant to high and low temperatures, otherwise they are prone to failure;

Protection level: For outdoor installations or factory workshops with dust and oil stains, choose SPDs with high protection levels that are waterproof, dustproof, and resistant to mechanical impact, making them less likely to break.

How to install an SPD?

1. Installation Location: The closer to the power source/equipment, the better.

Power Inlet: The SPD should be installed where the power line enters the building or equipment to block surges as early as possible and prevent them from entering the equipment.

Tiered Installation: Install the SPD next to the main distribution box, sub-distribution boxes, and terminal equipment according to the previously mentioned Class I, Class II, and Class III classifications. Layered protection is more reliable.

2. Connecting Cables: The shorter the better, and grounding must be secure.

Cable Length: The connection cable between the SPD and the equipment/distribution box should be kept within 0.5 meters. The longer the cable, the worse the surge protection effect.

Equipotential Bonding: The grounding wire of all SPDs must be connected to the building's ground wire to ensure that surge current is successfully conducted to the earth.

3. Installation Methods: Distinguish Between Parallel and Series Connections

Parallel Installation: This is used in the vast majority of cases, such as the SPD in a distribution box. It is connected in parallel to the power lines to discharge surges without affecting normal power supply.

Series Installation: This is generally used for signal lines (such as network cables and data cables). It is connected in series in the middle of the signal line to protect the signal from surge interference.

4. Regular maintenance

Read the indicators: High-quality SPDs have status indicators; green indicates normal operation, while red indicates failure and requires replacement.

Regular inspection: During rainy seasons (such as spring and summer), or in critical locations like factories and power plants, SPDs should be inspected periodically to ensure their functionality.

Electrical safety is paramount. A small SPD can prevent equipment damage, reduce downtime losses, and even prevent electrical fires. Anhui Jinli Electric's SPDs are available in models suitable for different industries and scenarios. Whether you're in an industrial plant, railway substation, communication base station, or new energy power plant, you can find the right "protective shield."

By choosing the right model, installing it in the correct location, and performing regular maintenance, you can protect your electrical equipment from surge threats, ensuring safe and long-lasting use! If you have any further questions, feel free to contact Anhui Jinli Electric; their professional team will help you tailor a protection solution.