In this article we look at what a thermographic survey of your electrical systems means, and what problems it can and can not find.
What is a Thermographic Survey?
In basic terms, it means looking for temperature differences, or hot spots. A Thermographic Survey of electrical equipment, or an electrical system, would normally be looking for heat build up that could cause a problem.
We have conducted Thermal Surveys for many years as part of normal inspections and tests. This originally involved feeling for heat, often by running your hands over fuses, circuit breakers, and cables etc., or looking for obvious signs of burning or arcing. The introduction of infrared thermometers made the process a little less tactile, and kept us more in line with the Electricity at Work Act. The development of thermal imaging away from the cryogenic systems to electronic systems has given us a much better tool, in the form of infrared cameras, for carrying out these thermal surveys. We can now graphically display heat build up, analyse what may be causing it, and predict if the heat is a normal part of energy delivery or a problem.
Why have a Thermographic Survey?
The Institute of Electrical Engineers state that Thermographic Inspections should not be seen as a substitute for Periodic Inspection and Testing, so why bother? Both have a specific role to play in analysing the condition of your electrical system and equipment, and both need to be conducted somewhat separately. For much of a periodic inspection and test the electrical system needs to be isolated from the supply, for some parts of the test the system needs to be energised, but not under load. To get the best from a Thermographic Survey, your electrical system needs to be running as close to normal load as possible. In addition to each procedure needing to be carried out with the electrical system at different states, each will find specific problems that the other may not. Some problems an inspection and test may find, that a thermographic survey may not, include;
- Insulation breakdown.
- Exposed live parts.
- Loose or missing earths.
- Inadequate earth impedance.
- Low level overloading.
- Inadequate RCD performance.
- Incorrect short circuit or overload protection.
- Low level unbalanced loads.
- Poor power factor.
- Overloaded circuits.
- Internal faults in switches, circuit breakers, and isolators.
- Unbalanced loads.
- Potential winding and bearing failures in motors and other equipment.
- Overloaded neutrals due to triplen harmonics.
Is it effective?
Thermal detection equipment is very effective in detecting problems that may be difficult to spot during a conventional test, usually before they can develop into a serious issue. It should also be noted that a thermographic survey of an electrical system should be carried out by an inspector with a really good understanding of electrical systems and equipment, and the results need to be analysed carefully.
It is quite normal for a hard working electrical system to generate some heat, this does not always mean there is a problem, many other factors need to be taken into account. Heat can also be found in a areas of a system where it should not be, this can often be indicative of a problem developing, but can easily be missed if the inspector is lacking in the knowledge of electrical systems.
We are passionate about the work we do, when we sign off an inspection and test report we need to know that we are giving our clients as much information as we can about their electrical system. The only way we feel we can do that, is to combine the electrical inspection and test, with a thermographic survey or their electrical system.