Drone Media Imaging conducted a full IEC 62446-3 compliant thermal inspection of the rooftop solar installation at Hilton Foods, Huntingdon, commissioned by Lumen Electrical. The survey combined radiometric aerial thermography and structured electrical testing to evaluate system behaviour, identify anomalies and verify general health of the commercial PV installation.
Thermal analysis detected a series of repeatable cell-level hotspots positioned consistently across multiple modules. These anomalies presented as uniform, low-severity temperature rises that aligned with manufacturing or design-linked characteristics rather than field faults. No evidence of PID, string imbalance, diode dropout or installation defects was found. Electrical readings taken under IEC 62446-1 confirmed stable Voc, safe insulation resistance values and correct bonding arrangements.
Environmental factors—703 W/m² irradiance, 17°C ambient, and steady wind conditions—provided a strong baseline for accurate thermal interpretation. The combined findings concluded that the system was performing within expected parameters, with no operationally significant concerns. Continued monitoring is advised to track long-term behaviour, but no immediate corrective work is required.
This project demonstrates the value of pairing Level 3 thermal analysis with IEC-aligned electrical testing for reliable assessment of commercial solar PV assets.
Project Overview
Subject
solar panel inspection, drone solar thermography, IEC 62446-3 inspection, commercial PV survey, rooftop solar fault detection
Skills Used
Aerial Thermography (Level 3), IEC 62446-3 Compliance, IEC 62446-1 Electrical Testing, Radiometric Thermal Analysis, PV System Diagnostics
Portfolio Tags
solar, thermography, PV inspection, IEC compliance, commercial rooftop, hotspot detection, drone survey, solar maintenance
IEC 62446-3 Solar Panel Inspection at Hilton Foods, Huntingdon
Level 3 thermography and IEC-compliant solar inspection delivering accurate temperature profiling, hotspot detection, and electrical performance verification..
aerial thermal inspection for solar panels
Project Overview – Aerial Thermal Survey of a Commercial Rooftop PV System
Drone Media Imaging was commissioned by Lumen Electrical to complete an IEC 62446-3:2017 compliant thermal inspection of the commercial rooftop solar array installed at Hilton Foods in Huntingdon. The objective was to assess module health, detect thermal irregularities, and verify general system behaviour under operating conditions.
The inspection took place on 16 September 2025 at 10:42, using a radiometric 640×512 thermal camera flown at low altitude to achieve high-resolution module-level clarity. Environmental conditions were favourable, with 703 W/m² irradiance, 17.1°C ambient, 60% RH, and a WSW wind of ~9.8 mph, providing a stable thermal baseline for accurate analysis.
Aerial thermography allowed rapid, safe and comprehensive coverage of the full rooftop layout, capturing every string, row and module under consistent imaging geometry. This formed the foundation for a complete IEC-aligned temperature map of the system.
IEC 62446-3 Compliance
Thermal Findings – Systematic Cell-Level Hotspots Across Multiple Modules
The survey identified a repeating pattern of cell-level hotspots appearing in the same position across a range of modules. Each hotspot showed a temperature differential typically between 4°C and 10°C above reference levels. Because these anomalies were consistent in form, placement and intensity, they were assessed as non-critical and likely related to module design or manufacturing characteristics rather than field-installation issues.
Key findings included:
No evidence of string mismatch, J-box temperature rise, PID, or bypass diode dropout
No thermal signatures indicating electrical overload or reverse current behaviour
Localised shading from bird droppings caused isolated cell heating at a few locations
One module identified as missing/removed from a previous operational intervention
Importantly, no system-critical anomalies were detected during analysis, and no frames showed behaviour consistent with developing electrical failure.
drone solar hotspot assessment
Electrical Testing – IEC 62446-1 Verification & Interpretation
To complement the thermal inspection, string-level electrical tests were completed using IEC-compliant PV instrumentation. This provided quantitative electrical context to the radiometric thermal results.
Electrical Summary
Voc readings: approx. 600–650 V, stable across all strings
Isc readings: 2–8 A, reflecting fluctuating irradiance during short passing cloud
Insulation resistance (Riso): 29–58 MΩ, well above IEC minimum thresholds
Earth continuity: 0.38 Ω, confirming effective bonding of inverter metalwork
These measurements validated the thermal interpretation: the system was behaving consistently and safely, with no string-level abnormalities that would normally align with thermographic faults.
Recommended Action
Because the hotspot pattern is uniform and non-critical, the recommended approach is monitoring rather than intervention. Should the intensity of hotspots increase or spread across additional module batches, escalation to the manufacturer would be appropriate.
