Lightning and Surge Protection for Industrial Solar PV in MENA — Why the Damage Usually Comes From Surges, Not Direct Strikes

Consider a pattern that every solar O&M team recognizes in principle, even if few have documented it.

A storm passes over the region. Nobody sees a strike on the site. The next morning, one inverter shows a communication fault, another has lost its monitoring link, and a string shows a current deviation that was not there the day before. Production data looks only slightly lower. Nothing in the logs says “lightning”.

In many such cases the cause is not a direct strike on the array. It is a surge: a short, very fast voltage pulse that entered the plant through its cables, its earthing, or its data lines, and stressed components beyond what they were designed to tolerate. Some fail immediately. Others are weakened, and fail months later without any visible link to the event.

This article explains how lightning and surges reach an industrial PV plant, what the applicable standards ask for, which design choices matter most, and how to specify and inspect protection so that it is still working in year 15. It is based on standards and engineering principles. Where a number depends on the site, it is labeled as such. Our approach is based on engineering principles and aligned with the IEC TR 63227 international standard for solar PV lightning protection.

Lightning and Surge Protection: How a Storm Reaches a PV Plant

There are three coupling paths, and most plants are exposed to all of them.

1. Direct strike. Lightning attaches to a structure, a module frame, a mast, or a cable. This is the least frequent path at any single site, but the most severe, and it is the case an external lightning protection system is designed for.

2. Induced surges. A strike that lands tens or hundreds of meters away produces a rapidly changing magnetic field. Any conductor loop in the plant acts like an antenna, and a voltage is induced in it. This path is far more frequent than a direct strike, and it is the one that long DC cabling makes worse.

3. Conducted surges and ground potential rise. Current entering the ground raises the local earth potential. Surges also arrive along the grid connection and along communication, monitoring, and sensor cables. A plant that is perfectly protected on its DC side can still be damaged through its data lines.

The practical consequence is that protection must work as a system of layers (lightning protection, bonding, surge protective devices, cable routing), not as a single device.

Why Large DC Arrays Are Exposed

Three features of industrial PV make it more exposed than a typical building electrical system.

Long cable runs

DC cables between the array and the inverter room can run for hundreds of meters, which increases the area available to couple a surge.

Large conductor loops

The loop formed by the positive and negative conductors of a string is the key variable. The larger the loop area, the larger the induced voltage.

Exposed metal structures and distributed equipment

Frames, mounting steel, combiner boxes, and sensors sit outdoors, and inverters and data loggers sit at the far end of long cables.

The curve below makes the loop-area effect visible.

Induced voltage vs loop area curve:

%%{init: {"themeVariables": {"xyChart": {"plotColorPalette": "#FF6B6B, #4D96FF, #6BCB77, #FFA900"}}}}%%
xychart-beta
    title Induced-Voltage-vs-Loop-Area
    x-axis [1m2, 5m2, 10m2, 20m2, 50m2, 100m2]
    y-axis Voltage-kV 0 --> 32
    line Strike-at-20m [0.30, 1.5, 3.0, 6.0, 15.0, 30.0]
    line Strike-at-50m [0.12, 0.6, 1.2, 2.4, 6.0, 12.0]
    line Strike-at-100m [0.06, 0.3, 0.6, 1.2, 3.0, 6.0]
    line Equipment-limit-4kV [4.0, 4.0, 4.0, 4.0, 4.0, 4.0]

Legend: Calculated illustration, not measured data. Lines from top to bottom: strike at 20 m, 50 m, and 100 m from the loop; flat line at 4 kV as an example of an equipment impulse withstand level (use the value from your own equipment datasheets). Simplified model: V ≈ (μ0 / 2π) × (A / d) × (di/dt), with an assumed rate of rise of 30 kA/µs, loop in the worst-case orientation, no shielding by structures, no frequency effects. Real values depend on geometry and site.

What the curve shows. The induced voltage grows in direct proportion to the loop area and falls with distance from the strike. A string whose positive and negative cables are routed together can have a loop area of about 1 to 2 m². The same string with cables routed separately over a long run can reach tens of m². In this simplified model that is the difference between a few hundred volts and several kilovolts. The effect comes from cable routing, not from any equipment choice, and it is decided during installation at little or no extra cost.

What the Standards Ask For

The following is a map of the main documents. Clause numbers and edition details should be checked against the versions applicable to your project.

Two points deserve emphasis.

First, a risk assessment is the starting point, not an option. Lightning flash density varies widely between a desert interior, a mountain area, and a coastal zone. It should be taken from local meteorological or lightning-detection data, not assumed.

Second, an external lightning protection system and surge protection solve different problems. Air terminals address direct strikes. Surge protective devices address the surges that reach cables. Having one does not replace the other.

The Design Choices That Matter Most

Route positive and negative conductors together

This is the single most effective measure for reducing induced voltage, as the curve shows. It costs nothing if specified before cable installation, and it is expensive to correct afterward.

Install surge protective devices at both ends of long DC runs

Common guidance places protection at the inverter and, where the cable run between array and inverter is long (a figure of the order of 10 m is often cited), also at the array side. Verify the rule in the standard edition and the manufacturer’s instructions that apply to your plant.

Select devices on voltage protection level and DC rating

The protection level must sit below the impulse withstand level of the equipment being protected. DC devices must be rated for the actual maximum DC voltage of the string, and they require appropriate backup protection as specified by the manufacturer.

Protect the AC side and the data lines

Inverter AC output, the interconnection with the plant, RS485 and Ethernet links, and pyranometer or temperature-sensor cables are frequent entry points. A plant with well-protected DC circuits and unprotected data lines has only part of the solution.

Keep bonding continuous

Equipotential bonding between frames, mounting structures, combiner boxes, and the earthing system limits the potential differences that damage equipment. The earthing configuration discussed in the earlier article on DC earthing on this platform interacts with these choices, so lightning protection and DC earthing should be designed together.

Check what the warranty requires.

Some equipment warranties depend on the installation of specified protection. Read the terms before assuming surge damage is covered.

The Decision Framework

Decision flowchart:

flowchart TD
    A["New or existing industrial PV plant"] --> B["Lightning risk assessment (IEC 62305-2, local flash density data)"]
    B --> C{"External lightning protection needed?"}
    C -->|Yes| D["Air terminals, down conductors, earthing, separation distances"]
    C -->|No| E["Surge protection and bonding still required"]
    D --> F["Equipotential bonding of frames, structures, boxes"]
    E --> F
    F --> G["Route positive and negative conductors together to minimize loop area"]
    G --> H["SPDs on DC side (inverter end and array end for long runs)"]
    H --> I["SPDs on AC side and on data and sensor lines"]
    I --> J["Commissioning tests: bonding continuity, earth resistance, SPD verification"]
    J --> K["O&M inspection: SPD status, after-storm checks, replacement at end of life"]
    K --> L["Protection still working in year 15"]

    style B fill:#ffd93d,color:#000
    style G fill:#51cf66,color:#fff
    style L fill:#2f9e44,color:#fff

Legend: 🟡 Yellow = starting point | 🟢 Light green = highest-value design measure | 🟢 Dark green = protection maintained over the project life

Protection That Fails Silently

Surge protective devices are consumable. Each surge uses up part of their capacity, and at the end of life they may stop protecting while the system keeps running normally. Many devices have a status indicator or a remote contact for this reason.

This makes inspection the weak link. A plant can leave commissioning with correctly installed protection and, after several storm seasons, operate with devices that have already reached end of life, and nobody knows.

Commissioning checks

• Continuity measurement of equipotential bonding, with values recorded.
• Earth resistance measurement of the earthing system.
• Verification that SPDs are the specified type and rating, correctly connected, and with status indicators in the normal state.
• Documentation of cable routing for positive and negative conductors, with photographs.

Inspection during operation

• Visual and remote status check of every SPD at the quarterly inspection, integrated with the monthly field protocol described earlier on this platform.
• An additional inspection after any significant storm in the area, with attention to SPD status, communication faults, and strings that show a deviation.
• Replacement of any device at end of life, with a record of the replacement.
• Thermal imaging of SPD enclosures and terminals during the annual thermal inspection.

Good Answer or Red Flag: Questions for Your Contractor

1. “Was a lightning risk assessment performed, and which local data did it use?”
Good answer: “Yes, per IEC 62305-2, using flash density data from [named source], with the resulting protection level documented.”
Red flag: “Solar plants do not need one in this region.”

2. “How are positive and negative DC conductors routed, and what is the resulting loop area per string?”
Good answer: “Routed together along the full length, with the routing drawing included in the handover documentation.”
Red flag: “The routing follows the cable trays.” That is not a loop-area specification.

3. “Where are DC surge protective devices installed, and what are their protection level and DC rating?”
Good answer: “At the inverter and at the array end for runs above the threshold, with the datasheet values compared against the equipment withstand levels.”
Red flag: “The inverter has built-in protection.” Built-in protection varies, and it does not cover the array end or the data lines.

4. “Are data, communication, and sensor lines protected?”
Good answer: “Yes, with surge protection on each external line, listed in the protection schedule.”
Red flag: “Only the power circuits are covered.”

5. “How will end-of-life status of the SPDs be monitored and who replaces them?”
Good answer: “Status contacts are connected to monitoring, with quarterly inspection and replacement written into the O&M scope.”
Red flag: “SPDs are maintenance-free.” No SPD is.

The Contract Dimension

Two of the clauses discussed in earlier articles on this platform extend naturally to protection.

• EPC contract: require the lightning risk assessment, the SPD schedule with protection levels, the cable routing specification, and the bonding continuity and earth resistance test results as commissioning deliverables.
• O&M contract: include SPD status inspection, post-storm inspection, and replacement at end of life, with the replacement cost allocated explicitly, and require reporting of any storm-related event.

How to Think About the Cost

Protection costs are small relative to the plant, and the useful question is whether the expected avoided loss exceeds the annualized cost. The method is:

Expected annual avoided loss per MWp = (annual probability of a damaging event per MWp) × (repair or replacement cost + lost energy value during downtime)

The probability depends on local flash density, plant layout, and existing protection, and the consequence depends on which equipment is affected and how long replacement takes. Both should be estimated for the specific plant, using your own equipment prices and tariff. A single damaged inverter can mean a long lead time for a replacement, which turns a small repair into a long loss of production. This argues for including downtime in the calculation.

I do not give a dollar figure per MWp here, because it would depend on assumptions that vary from site to site. The method above, applied to your own numbers, will give you a defensible one.

Lightning protection for a PV plant is rarely about a dramatic strike. It is about the ordinary storm that passes at some distance and leaves a surge in the cables.

The measures that matter most are not exotic. A documented risk assessment. Positive and negative conductors routed together. Surge protective devices at the right places on DC, AC, and data lines. Continuous bonding. Commissioning measurements that create a baseline. And an inspection routine that treats SPDs as consumables, so that protection that was installed in year one is still there in year fifteen.

None of these require new technology. They require that someone asks, before the cables are pulled, the questions listed above.

If you are specifying or reviewing lightning and surge protection for an industrial solar installation in MENA or Africa and want an independent technical review of the design, the commissioning checklist, or the O&M scope, a structured review is available.

Contact: contact@solarpvmena.com — response within 48 hours.

The inspection and commissioning methodology referenced in this article builds on the field protocols documented in earlier articles on this platform and in the MENA Industrial Solar Data Guide. The guide covers commissioning baselines, inspection routines, and operating data from an industrial installation in Morocco. It does not cover lightning protection design.

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