Created by: Glen Zhu | Updated Date: March 24th, 2025
When deciding the installation location of surge protective devices (SPDs), it is not enough to only consider the main distribution panel, branch circuits, and terminal equipment. In order to achieve comprehensive protection, it is necessary to combine the specific division of lightning protection zones (LPZ) to scientifically layout the installation location of SPDs in order to minimize the impact of surges on the system.
Lightning Protection Zones (LPZ) are defined concepts according to the IEC 62305-4 standard, aiming to divide areas into different protection levels based on the impact of lightning surges, and to configure corresponding SPDs according to the risk level of the area. Each zone requires surge protection devices (SPDs) of different levels for protection, in order to ensure that the system is protected from surge impacts.
Figure 1 – Lightning Protection Zone Concept
1. Location: Building exterior, photovoltaic systems, power grid entrance, electric vehicle charging stations, etc.
2. Affected by: Direct lightning strikes, electromagnetic induction, and strong surge interference
3. Recommended Surge Protection Device:
1. Location: Exterior wall boundaries, communication equipment, security systems, video surveillance, etc.
2. Affected by: Lightning Electromagnetic Pulses (LEMP) and surge energy interference
3. Recommended Surge Protection Device:
Function: Limit lightning surges and eliminate some internal induced surges
LPZ 1: Internal areas of main power distribution system and equipment
1. Location: Main distribution board, sub-distribution board, HVAC, photovoltaic inverters, etc.
2. Affected by: Residual lightning surges and inductive surges
3. Recommended Surge Protection Device:
LPZ 2: Area of precision equipment and sensitive electronic systems
1. Location: Data centers, network equipment, PLCs, medical devices, smart home systems, etc.
2. Affected by: Low voltage surges, inductive surges, and electromagnetic interference
3. Recommended Surge Protection Device:
2. LPZ 1 → LPZ 2 (branch circuit protection)
3. LPZ 2 → LPZ 3 (terminal equipment protection)
Location 1: Interface between the low-voltage distribution cabinet (incoming cabinet) at the power supply entry point of the building, i.e. LPZ 0 zone and LPZ 1 zone.
1. Low-voltage distribution line entry: (first level)
2. High-voltage distribution line entry into the building: (first level)
Location 2: Electrical equipment for building roofs (air conditioning units, outline lights) distribution box (at the interface between LPZ 0B zone and LPZ 1 zone, within LPZ 1 zone)
Conditions: The building uses a common grounding system, has a complete direct lightning protection device. When the electrical equipment is within the protection range of the air terminal:
Location 3: Information system computer room (LPZ 2 area)
Conditions: The building is equipped with external lightning protection devices, and the computer room implements comprehensive lightning protection measures such as grounding, shielding, equipotential bonding, etc.
For power and lighting distribution cabinets in the computer room, type 2 Surge Protection Device (second level) should be selected, with In not less than 5kA and voltage protection level Up not greater than 2.5kV (second level).
For UPS input or output distribution cabinets, type 2 Surge Protection Device (third level) should be selected, with In not less than 5kA and voltage protection level Up not greater than 1.5kV. For large computer rooms with equipment distribution line lengths exceeding 10m, a fourth-level SPD should also be added at the power supply location inside the equipment cabinet, with Up not greater than 1.5kV (third level).
Location 4: Building vertical shaft distribution cabinet (LPZ 2 area) (lightning induction protection) (second level)
Location 5: Outdoor electrical equipment distribution cabinet (LPZ 0 area) (first level)
According to the grounding method of the on-site low-voltage distribution system, determine the wiring method of Surge Protection Device, using 4P or 3+1 method.
The grounding methods of low-voltage distribution systems include: TN (TN-C, TN-C-S/TN-S), TT, IT.
Figure 2 – Wiring Method of Surge Portection Device (TN-C, TN-C-S, TN-S, TT, IT)
2. Coordinated Surge Protection Device system
3. Surge Protection Device branch, it is advisable to install overcurrent protection devices (backup protection devices, dedicated protection devices)
4. The total length of the connection lines for Surge Protection Device, overcurrent protection device, and SPD grounding line should be as short as possible, within a range of 0.5m.
Figure 3 – Connection Distance Specifications for Surge Protection Device
LSP’s reliable surge protection devices (SPDs) are designed to meet the protection needs of installations against lightning and surges. Contact our Experts!
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