Chapter 9: Calculator
Security Systems Lightning Protection and Grounding Design Guide
The following interactive calculators provide real-time engineering guidance for the most common design decisions in security system lightning protection. Each calculator produces immediate visual feedback as you adjust the input parameters, enabling rapid design iteration and "what-if" analysis. Results are indicative design guidance — final designs must be verified against applicable local standards and site-specific conditions.
Calculator 1: Lightning Risk Level Assessment
Estimate the lightning risk level for your security system installation based on site parameters.
3.0
flashes/km²/year — typical range 0.1 to 20
200
meters — outdoor copper cable length
10
meters — tallest structure or pole
Impact of security system failure
Composite Risk Score & Level
6.5 — MEDIUM
Recommended: Type 2 SPD + Ethernet SPD + bonding
Recommended protection measures will appear here.
Calculator 2: Grounding Electrode Resistance Estimator
Estimate the resistance of a vertical rod electrode or horizontal ring electrode based on soil resistivity and geometry.
100
Ω·m — typical: clay 20–100, loam 100–400, sand 400–2000
3.0
meters — typical 2–6 m for security poles
16
mm — standard copper-bonded rod: 14.2 mm
1
Parallel electrodes (spacing ≥ 2× length)
2.1 Ω
✓ Meets ≤ 4 Ω target
Estimated Electrode Resistance
2.1 Ω
Single vertical rod, 3 m, ρ = 100 Ω·m
Target: ≤ 4 Ω. Meets design target.
Calculator 3: SPD Voltage Protection Level (Up) Coordination Checker
Verify that your SPD stages are correctly coordinated — Up must decrease from Type 1 → 2 → 3, and each Up must be below the protected equipment's withstand voltage.
4.0
kV — typical 2.5–4.0 kV for Type 1
2.5
kV — typical 1.5–2.5 kV for Type 2
1.5
kV — typical 0.8–1.5 kV for Type 3
1.5
kV — per equipment datasheet (typical IT: 1.5 kV)
Type 1
4.0 kV
4.0 kV
Up1
→
Type 2
2.5 kV
2.5 kV
Up2 < Up1?
→
Type 3
1.5 kV
1.5 kV
Up3 < Up2?
→
Equipment
Uw 1.5 kV
Uw 1.5 kV
Up3 < Uw?
Coordination Status
✓ COORDINATED
All Up levels decrease correctly; Type 3 Up below equipment Uw
Coordination is correct. Verify cable length ≥ 10 m between Type 2 and Type 3, or add decoupling inductor.
Calculator 4: Cable Separation Distance Calculator
Calculate the minimum separation distance between security system cables and lightning protection down conductors, based on LPS class and installation conditions.
Per IEC 62305-3 / local standard
Material between cable and down conductor
10
Length of parallel run alongside down conductor
2
More conductors = lower current per conductor = smaller separation
Minimum Separation Distance
0.75 m
LPS Class II, air, 10 m run, 2 down conductors
If separation cannot be achieved, use fiber optic cable (no separation required) or install cable in metallic conduit bonded to the LPS system.
Calculator 5: Bonding Conductor Size Selector
Select the minimum bonding conductor cross-section based on the application, expected surge current, and conductor length.
20
kA — from SPD Imax or LPS class
2.0
meters — keep as short as possible
≤ 6 mm² — SPD short leads
16 mm² — Standard bonding
25 mm² — High-current paths
35 mm² — Main bonding
Recommended Conductor Cross-Section
16 mm² Cu
Equipment rack to MEB, 20 kA, 2 m, indoor
Use tinned copper conductor with green/yellow PVC insulation. Terminate with hydraulic crimp lug. Label both ends.