A thermographic survey is an infrared-imaging inspection of electrical equipment and connections under load or at rated conditions, in which a calibrated thermal camera detects and records the surface temperature of every component in the system under test - switchgear, transformers, bus work, cable terminations, joints, and fuses - to identify any point where abnormal heat is being generated. NETA ATS-2025 section 9 governs the acceptance thermographic survey, which is performed on the complete electrical system or a major subsystem, with the camera focused on all accessible components that are expected to carry current or dissipate heat once the system is energized. The thermal image or video footage is then compared against the baseline ambient temperature and the known temperature rise that normal operation should produce, and any area that stands out as hotter than expected is flagged and investigated.
Electrical connections, components, and conductors that are loose, corroded, oversized, undersized, or incorrectly installed will generate excess heat under load as resistance rises at the fault site - long before the heat manifests as smoke, arcing, or burnout. A thermographic baseline taken before the system is put into service, or early in its life, establishes what normal operation looks like on a thermal image; any future thermographic survey that shows a new hot spot, or a progressive rise in temperature at a known joint, signals a developing problem that can be addressed through maintenance or repair before it becomes a fire, a fault, or an unplanned outage. At acceptance, a thermographic survey confirms that all terminations, connections, and components are within their expected temperature profile for the loading conditions under which the survey is run.
Acceptance: a thermographic survey is performed after the system or subsystem has been energized and loaded, or brought to rated conditions, so that current is flowing and heat generation reflects real operation rather than no-load idle conditions. The survey is typically done early in the energization sequence or shortly after initial startup, once the system has reached a stable thermal state and all components have had time to rise to their steady-state temperature. This baseline thermographic record is then retained for comparison against future surveys during the equipment's service life.
With the system energized, loaded, and operating at or near nameplate current and voltage, a qualified thermographer equipped with a calibrated infrared thermal camera (with a calibration due date verified before use) systematically scans all accessible electrical components and connections that are part of the circuit under test: bus-bar joints and terminations, transformer bushings and cooler attachments, cable-to-equipment terminations, switch and breaker contacts, resistor banks, and any other heat-generating or current-carrying path. Ambient temperature is recorded alongside the thermal readings so the observed temperature rise can be normalized to the baseline. The thermal image or video is captured at each location, labeled with the component identity and location, and any area that visibly exceeds the expected temperature for that type of component is photographed in detail and documented in the thermographic survey report.
For each area inspected, per NETA ATS-2025 section 9.2.5: the location and identity of the component, the surface temperature recorded by the thermal camera, the ambient temperature at the time of survey, the system voltage and current (or loading level) under which the survey was performed, and the thermal camera make, model, serial number, and calibration due date. Any area flagged as showing elevated or abnormal temperature is recorded separately with its location, measured temperature, and deviation from the expected baseline or the adjacent-component reference temperature. Survey date and time, thermographer name and credentials, and ambient conditions (weather, humidity, time of day if relevant to solar gain) are documented alongside the visual and mechanical inspection notes so the thermal baseline can be reproduced and audited later.
NETA ATS-2025 section 9 and its referenced Table 100.18 provide guidance on interpreting the findings: a component or connection that runs within the expected temperature range for its type and loading level is accepted as normal, while any area showing a temperature rise above the equipment nameplate rating or a significant deviation from the adjacent-phase or adjacent-component reference temperature is investigated further before the system is left in continuous service. The threshold for 'abnormal' depends on the component type, the loading, and the ambient conditions; NETA ATS-2025 provides a structure for recording findings and assigning suggested actions (continue in service, continue with caution, perform maintenance, or take out of service pending repair) based on the magnitude and location of the anomaly. See the purchased standard for the complete guidance table and the thermographer qualification requirements.
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