When installing surge protectors (SPDs), it is necessary to strictly follow the specifications to ensure their effective operation and avoid safety hazards. The following are key precautions and operational points:
1、 Preparation and selection before installation
Match the usage environment
Voltage and frequency: Ensure that the rated voltage and frequency of the SPD match the system (such as 220V/380V AC power supply, DC power supply, etc.) to avoid component burnout caused by voltage mismatch.
Protection level: Select the corresponding SPD level according to the installation location:
First level protection (Type 1): used for direct lightning protection, installed in the main distribution box, requiring high lightning current resistance capability (such as 10/350 μ s waveform impulse).
Secondary protection (Type 2): Installed in the distribution box, tested for induced lightning and operational overvoltage using an 8/20 μ s waveform.
Level 3 protection: Near terminal devices (such as sockets), used for fine protection, requiring low residual voltage and fast response.
Scenario adaptation: Signal lines need to select SPDs with corresponding frequencies (such as 100Mbps/1G SPDs for network lines and RF SPDs for antenna lines).
Electrical parameter matching
Maximum continuous operating voltage (Uc): It should be 1.1-1.3 times higher than the normal operating voltage of the system (such as selecting Uc ≥ 255V for 220V systems) to prevent SPD from long-term overload failure.
Current carrying capacity: Select the nominal discharge current (In) and maximum discharge current (Imax) based on the expected surge intensity, such as power supply primary protection In ≥ 12.5kA, Imax ≥ 25kA.
Response time (Ta): In multi-level protection, the response time of the front stage (such as Type 1) can be slightly longer, and the last stage (Type 3) needs to be ≤ 25ns to ensure that the surge is suppressed step by step.
2、 Installation location and wiring specifications
Installation location of power system
Main distribution box (primary): installed at the incoming end of the household power supply, with a distance of ≤ 1m from the grounding busbar, to ensure rapid discharge of lightning current.
Distribution box (secondary): installed in the floor or area distribution box, with a distance of ≥ 5m from the primary SPD (if there is no decoupling device), to avoid the impact of undischarged surges from the previous stage on the subsequent stage.
Terminal device (Level 3): directly connected to the device's power outlet, or integrated inside the device (such as a server UPS with built-in SPD).
Installation location of signal system
Household end: Install corresponding SPDs at the entrance of network lines, telephone lines, cable TV lines, etc. to prevent surges from entering along the line.
Front end devices: Install SPDs in front of cameras, sensors, switches, and other equipment, especially outdoor devices that require priority protection.
Wiring principles
Short and straight circuit: The connection wires (live wire, neutral wire, ground wire) of SPD should be as short (≤ 0.5m) and straight as possible to avoid the formation of inductive loops and reduce the protective effect.
Separation of strong and weak electricity: The wiring between the power SPD and the signal SPD should be kept at a distance of ≥ 30cm to prevent secondary interference caused by electromagnetic coupling.
Grounding independence: The grounding wire of SPD should be separately connected to the grounding busbar (BVR yellow green wire, cross-sectional area ≥ 4mm ²), and it is prohibited to mix it with the neutral wire and equipment grounding wire.
3、 Grounding and equipotential connection
Grounding resistance requirements
The grounding resistance of the power supply SPD should be ≤ 4 Ω (building lightning protection grounding standard), and the signal SPD can be ≤ 10 Ω; If it is an independent grounding, the distance between the two should be ≥ 5m.
If the grounding resistance does not meet the standard, it is necessary to add grounding electrodes or use resistance reducing agents to improve it.
equipotential bonding
Connect SPDs, equipment metal casings, metal pipes, building steel bars, etc. to the same equipotential terminal board through grounding conductors to prevent potential differences between different points from penetrating the equipment.
Multi level SPDs need to be connected through decoupling components (such as inductors and resistors) to ensure that the front stage operates before the rear stage, avoiding "current grabbing" that can cause the rear stage to fail.
4、 Safety and maintenance precautions
Electrical safety operation
Cut off the power before installation and use insulated tools to avoid electric shock; The signal SPD needs to disconnect the signal source to prevent surge backlash.
The power supply SPD needs to be connected in series with fuses or circuit breakers (such as 16A air switches) to prevent the SPD from short circuiting and causing fires after aging.
Identification and recording
Mark the SPD model, installation date, rated parameters, and draw a system topology diagram for later maintenance.
The signal SPD needs to be labeled with the line type (such as "WAN port" and "CCTV") to avoid misconnection.
Regular testing and replacement
Visual inspection: Check the SPD indicator light (green is normal, red is invalid) and whether the casing is swollen, burnt, or damp every quarter.
Performance testing: Every year, specialized instruments are used to measure parameters such as residual voltage and leakage current. If performance degradation is found (such as residual voltage exceeding 1.3 times the nominal value), it should be replaced in a timely manner.
Life management: The service life of SPDs is usually 5-8 years, and the replacement cycle needs to be shortened when they are frequently subjected to surge impacts.
5、 Special scenario precautions
Flammable and explosive environment
Choose explosion-proof SPD and ensure reliable grounding during installation to avoid danger caused by electric sparks.
outdoor equipment
The signal SPD needs to have a waterproof casing (IP65 or above), and the power SPD needs to be equipped with a rain cover to prevent rainwater from entering and causing short circuits.
Hybrid system (power+signal)
When installing power and signal SPDs simultaneously, it is necessary to ensure that both are grounded on the same grid to avoid potential difference damage to the equipment.
Summary: Key points of installation
Accurate selection: triple matching of voltage, level, and scene to avoid "big horse pulling small car" or "small horse pulling big car".
Short and straight wiring: reduces line inductance and ensures rapid discharge of surges.
Reliable grounding: Low resistance grounding and equipotential connection are the basis of protective effect.
Timely maintenance: Regular testing and replacement to ensure that SPD is always in an effective state.
Following the above specifications can maximize the protective effect of surge protectors and reduce the risk of equipment damage due to overvoltage.
