Load is not optional
Graded to a criterion
Thermal misses PD
What was not reachedWhat a survey actually covers
- Switchgear, MCCs and distribution boards, under load, with the load recorded alongside every image
- Busduct and busbar systems, including joints, which is where busduct almost always fails
- Transformers, bushings and terminations
- Cable terminations and joints
- Motors, drives and starter circuits
- Acoustic imaging for partial discharge on medium-voltage assets, where a thermal camera sees nothing at all
A survey performed at light load will pass equipment that would fail at full load. Rise is proportional to the square of current, so the same defect at half load shows roughly a quarter of the temperature rise. Every image needs the load at the time recorded next to it, and a survey taken during a quiet shift should say so on its face.
Grading, so two surveys can be compared
A number without a criterion is unusable. Findings are graded against published severity criteria, based on the rise above a reference, either a similar component under similar load or the ambient, and on whether the component is a connection or a conductor.
Widely used industry guidance treats a rise of a few degrees over reference as something to monitor, ten to twenty degrees as requiring repair at the next opportunity, and rises beyond roughly forty degrees over reference as requiring immediate attention. Published electrical maintenance guidance places a clear danger threshold in the region above 120 °C at the component itself. Whichever criterion is used, the report must name it, so that a survey next year is comparable rather than a fresh opinion.
If you are considering permanently installed temperature sensors on busduct or switchgear rather than periodic survey, check the sensor's own maximum rated temperature. Many common contact sensors top out below the danger band that the maintenance standard is asking you to detect. A sensor that saturates before the alarm condition cannot raise it. This has to be checked at specification, against the datasheet, not assumed.
Hazardous areas, where the camera choice is settled before the survey
In a classified area, the instrument taken through the door has to be certified for that zone. This is a compliance requirement, not a preference, and it is the cost floor for surveying that area.
It is also the single most common place where a survey scope gets quietly value-engineered, by substituting a non-certified instrument and surveying from outside the boundary or during a shutdown. That changes what the survey is. Certification is never the thing to trade away. If cost has to come out of a hazardous-area survey, take it out of scope, frequency or reporting depth, and keep the compliance intact.
What you get
A report that a maintenance planner can raise work orders from without calling us:
- Thermal and visual image pairs for every finding, so the component is identifiable
- Load at the time of measurement, and ambient
- Component identification down to the panel, the way it is labelled in your plant
- Rise over reference, the criterion applied, and the resulting severity class
- A recommended action and a timeframe
- A register of items that were not accessible, and why. A survey that quietly omits what it could not reach reads as a clean bill of health and is not one.
Questions we get asked
How often should a thermal survey be done?
Annually is the common baseline for general distribution. Critical switchboards, high-cycling equipment and anything with a history of findings justify more frequent survey. What matters as much as the interval is that it is done under comparable load, so the trend means something.
Do panels have to be opened?
To see terminations directly, yes, and that carries an arc flash risk which has to be managed by a competent person with the correct PPE and a permit. Infrared windows installed at the design stage remove that exposure permanently and make future surveys quicker and safer.
Can a thermal camera detect partial discharge?
No. Partial discharge is largely an acoustic and radio-frequency phenomenon, and a developing PD site may show no thermal signature at all until very late. Medium-voltage assets need acoustic or ultrasonic assessment alongside the thermal survey.
Can you survey inside a hazardous area?
Yes, with a camera certified for the zone. That is a requirement of the area classification rather than a choice, and it should be confirmed in writing before the survey is scheduled.