- Why undertake a thermographic survey?
- Under what circumstances should I consider a thermographic survey?
- Is any additional guidance available?
- When is it most beneficial to undertake a themographic survey?
- Typically what items of equipment would be included in the thermographic survey?
- What are the outputs from a thermographic survey?
Why undertake a thermographic survey?
The objective of a thermographic survey is to identify abnormally high temperatures within electrical distribution systems. Any high temperatures within electrical components are often indicative of imminent or possible problems. Early identification of these faults is essential in order that corrective action can be undertaken before the problem escalates. Electrical circuits and components often fail because of fatigue, defective components, contamination, or just loose connections due to poor workmanship, but all failing components have one thing in common, they will always have a rise in temperature or ‘hot spot’ prior to failure.
The Institution of Engineering and Technology (IET) recognise the benefits of performing thermographic surveys of an electrical distribution system, as a supplement to a periodic inspection and test. It is not however, a substitute for an inspection and test programme or documented routine maintenance programme.
Under what circumstances should I consider a thermographic survey?
Thermographic surveys are particularly valuable on large, complex 24/7 operations, where electrical equipment cannot be switched off. Isolation of the supply becomes increasingly difficult where the continuity of supply is essential for patient care, for example, as may be the case in hospitals.
Notwithstanding the foregoing, it remains necessary to confirm the continuing suitability of such installations to remain in service. They must therefore still be subjected to planned and preventative maintenance, or regular periodic assessment of their condition.
Is any additional guidance available?
Guidance on the scope of thermographic survey is given in IEE Wiring Regulations Seventeenth Edition BS 7671:2008 Guidance Note 3, Inspection and testing.
When is it most beneficial to undertake a thermographic survey?
It is imperative that as many circuits as possible are in operation whilst carrying out the thermographic survey as it is only when the electrical system is under load, that weaknesses (hot spots) are most readily identified.
In order to gain the maximum benefit from the survey, it is better to remove covers or open doors wherever possible, as the camera measures surface temperature. Excessive temperatures can however still be identified where this is not practical, as heat will radiate out and warm the covers and doors.
Typically, what items of electrical equipment would be included in the thermographic survey?
In the first instance, electrical equipment which cannot be isolated or equipment which is giving cause for concern. A methodical approach, from source of supply through to final circuits is the normal procedure, but not always possible. Preparation for a thermographic survey is the key in order to maximise the engineer’s time and efficiency whilst on site.
The following list is not exhaustive:
- Main LV transformer
- Main switch panel
- Main distribution boards
- Sub distribution boards
- Consumer units
- Supplies to fixed equipment
- Cables emanating from substations, MCCs, control panels and distribution boards
- Motor or motor controlling equipment/wiring systems integral to plant and machinery enclosures
What are the outputs from a thermographic survey?
Suspected problems identified during the course of a survey are photographed, with both thermal and digital images presented in our report. Guardian would give an explanation as to the cause of problems identified, wherever possible. In the report there will also be a listing of all equipment surveyed for reference purposes, which will satisfy EaWR 1989, and BS 7671:2008.
Guardian would undertake the survey systematically, looking at distribution equipment within the premises, as well as switchgear, and where applicable infrastructure. The work is most cost effectively completed with the assistance of the client. Guardian would require a member of staff to accompany our engineer whilst on site, thereby providing access to areas when required, as well as providing the most direct route around the premises.
The thermographic report is to be produced in Microsoft Word format and can be supplied on our interactive website, as a bound hard copy, or on CD-ROM.