SPD Selection Guide by Application Scenario: Precision Protection & Cost Optimization

Surge Protective Devices (SPDs) are critical defenses safeguarding electrical

equipment against lightning strikes and electrical surges. Given diverse application scenarios, scientific SPD selection is paramount for ensuring equipment safety and

longevity. This guide provides tailored recommendations to help mitigate

equipment damage and financial losses.

1. Residential Applications

Scenario Characteristics: Primarily low-voltage, single-phase power supply for appliances like TVs, AC units, and refrigerators.

Surges typically originate from induced lightning or grid fluctuations, with

generally low energy levels.

Selection Criteria:

Protection Level: Type 2 (T2).

Key Parameters:

Nominal Discharge Current (Imax, 8/20µs): ≥ 10kA ~ 20kA.

Voltage Protection Level (Up): ≤ 1.5kV.

Installation Location: Main distribution panel, connected in parallel with circuit breakers or RCDs.

Recommended Solution: Kaitai T2 SPD.

2. Commercial Buildings

Scenario Characteristics: Diverse electrical loads (lighting, elevators, HVAC, network equipment) within complex multi-level distribution systems. Surge sources include external lightning strikes

and internal switching overvoltages.

Selection Criteria:

Protection Level: Recommended multi-stage protection using Type 2 (T2) + Type 3 (T3).

Key Parameters:

Primary Protection (T2, Main Distribution Board): Imax ≥ 20kA ~ 40kA (8/20µs), Up ≤ 1.5kV ~ 2.0kV.

Secondary Protection (T3, Sub-Distribution Boards/Floor DBs): Imax ≥ 10kA ~ 20kA (8/20µs), Up ≤ 1.5kV.

Installation Locations:

Primary: Main Distribution Board (MDB).

Secondary: Sub-distribution boards or floor distribution cabinets.

Recommended Solution: Kaitai T2/T3 SPD solutions, offering high cost-effectiveness and easy installation.

3. Industrial Environments

Scenario Characteristics: Loads include large machinery, sensitive

controllers (PLCs), and VFDs. Equipment is highly vulnerable to powerful

lightning and switching surges.

Selection Criteria:

Protection Level: Essential coordinated protection using Type 1 (T1) + Type 2 (T2).

Key Parameters:

Primary Protection (T1, Service Entrance): Impulse Current

(Iimp, 10/350µs) ≥ 25kA, Up ≤ 2.5kV.

Secondary Protection (T2, Sub-Distribution): Imax (8/20µs) ≥ 40kA ~ 80kA, Up ≤ 1.7kV.

Installation Locations:

Primary: Building main power intake/service entrance.

Secondary: Workshop or equipment sub-distribution panels.

Recommended Solution: Kaitai T1+T2 SPD module sets.

4. Data Centers & Sensitive Equipment

Scenario Characteristics: Core equipment (servers, switches) is extremely

sensitive to voltage transients, requiring ultra-low residual voltage (Up) and fast response.

Selection Criteria:

Protection Level: Type 3 (T3) - Fine Protection Level.

Key Parameters:

Imax (8/20µs): ≥ 10kA.

Up: ≤ 1.0kV (suitable for sensitive equipment).

Response Time (tA): ≤ 25ns.

Installation Location: Equipment front-end, e.g., within server rack PDUs or at equipment sockets.

Recommended Solution: Kaitai Data Center SPDs (supporting combined

power & signal line protection).

5. Telecommunication Base Stations

Scenario Characteristics: Complex protection needs (power, antenna

feeders, signal/data lines) with multiple surge entry paths.

Selection Criteria:

Power Protection (T1+T2):

Iimp (10/350µs) ≥ 50kA (Primary).

Imax (8/20µs) ≥ 40kA (Secondary).

Signal/Data Line Protection:

Select dedicated Signal SPDs; focus on data rate, insertion loss, and interface type (RJ45, BNC, etc.).

Antenna Feeder Protection:

Focus on operating frequency range, Voltage Standing Wave

Ratio (VSWR), and insertion loss.

Recommended Solution: Kaitai Telecom Surge Protection Series

(Power SPDs, Signal Protectors, Antenna SPDs).

6. Photovoltaic (PV) Power Systems

Scenario Characteristics: Comprises high-voltage DC and AC sections. Surges can enter via DC strings or inverters.

System DC voltages are high (typically 500V~1500V DC).

Selection Criteria:

DC Side: Use PV-specific SPDs.

Imax (8/20µs): ≥ 20kA ~ 40kA.

Maximum Continuous Operating Voltage (Uc): Must match

system voltage (e.g., 1000V DC, 1500V DC).

AC Side: Use standard T2 SPDs.

Recommended Solution: Kaitai PV DC SPDs.

Summary: Core Principles for Scientific SPD

Selection

Assess Risk to Determine Level: Required protection level (T1/T2/T3)

depends on lightning exposure, equipment value, and sensitivity.

Scrutinize Key Parameters:

Discharge Capacity (Iimp/Imax): Higher specifications needed in

high-risk areas (high lightning activity, industrial settings).

Residual Voltage (Up): Must be below the protected equipment's

withstand level; lower Up is critical for sensitive devices.

Voltage Rating (Uc): Especially critical for DC systems (PV); Uc

must be ≥ system maximum continuous operating voltage.

Implement Multi-Stage Protection: Employ coordinated T1+T2 or T1+T2+T3 protection for

staged energy diversion and clamping.

Ensure Proper Grounding & Installation (Foundation):

Grounding resistance ≤ 10Ω.

Grounding conductors must be short, thick, and straight (length < 0.5 meters preferred).

Strictly install SPDs at designated points per standards

(service entrance, distribution boards, equipment front-end).

Adhering to these guidelines enables effective SPD selection, safeguarding

electrical equipment across diverse scenarios while preventing resource waste from under- or over-protection. Choosing quality brands like Kaitai Lightning Protection, combined with professional installation and maintenance, provides comprehensive defense for

your electrical systems.