Solar arrays are exposed electrical installations with long cable routes and outdoor metal structures. A coordinated design for earthing, bonding, lightning risk and surge protection reduces electric-shock, fire and equipment-damage risk. Copying a standard earth-pit count without calculations is not an adequate design.
Key takeaways
- Earthing and bonding have different but related safety functions.
- Lightning protection should follow a site risk assessment.
- SPDs must match AC/DC voltage and discharge duty.
- Cable routing and separation influence induced surge risk.
Protective earthing and bonding
Exposed conductive parts should be bonded into the protective earthing system according to the applicable design. Connections must remain electrically continuous and corrosion-resistant over the project life. Earthing conductor size, material, routing and termination should be coordinated with fault protection and local soil conditions.
- Bond module frames and support structures as required.
- Use compatible metals and approved lugs.
- Protect conductors from mechanical damage.
- Test and document continuity and earth performance.
Lightning risk assessment
A rooftop PV system does not automatically require a separate lightning protection system, and it should not be assumed to protect a building. Assess building geometry, exposure, occupancy, existing protection and applicable standards. Where an LPS exists, PV placement, separation distance and bonding must be coordinated with it.
- Review the existing building lightning system.
- Maintain required separation where designed.
- Avoid creating unsafe flashover paths.
- Coordinate air terminals and PV layout.
AC and DC surge protective devices
SPDs limit transient overvoltage reaching sensitive equipment. Device type, maximum continuous operating voltage, discharge current, protective level and backup protection must suit the circuit. DC SPDs must be certified for the PV maximum voltage and polarity. Lead length and routing strongly affect protective performance.
- Select AC and DC products for their actual circuits.
- Keep SPD connections short and direct.
- Provide backup protection as specified.
- Inspect status indicators after surge events.
Installation verification
Final verification can include visual inspection, continuity, insulation resistance, polarity, protective-device checks and earth measurements as applicable. Results should be recorded with drawings and equipment data. Any interaction with the utility earthing arrangement must follow the approved design and local requirements.
- Use qualified electrical personnel.
- Follow safe isolation and test procedures.
- Maintain as-built drawings and labels.
- Retest after major modification or damage.
Frequently asked questions
How many earth pits does a solar plant need?
The number cannot be selected from capacity alone. It depends on the earthing design, soil, fault protection, lightning system and applicable requirements.
Can AC and DC use the same SPD?
No. Use devices specifically rated and certified for the relevant AC or DC circuit.
Does an SPD replace lightning protection?
No. Surge protection is one part of a coordinated lightning and electrical protection design.
Turn guidance into a practical system plan
Use Spectra’s engineering calculators for a preliminary estimate, then request technical verification before purchase or installation.