Thermography, The basics

Fuseboard Fault

Faults of fuseboards usually only come to light when they burn out or completely fail causing risk of fire or plant disruption. A survey will highlight problem areas and we will tell you in our report exactly what you need to do to repair the fault.

We regularly survey and locate faults on all types of electrical systems ranging from 132,000 volt power transmission systems through to industrial 415 and 12 volt systems. Huge benefits can be obtained from a quickly performed survey of your electrical distribution system and control panels.

Control Panel Fault

We have identified thousands of faults within control panels and switchgear. Very often the repair involves just re-tightening a connection but left alone would result in a burn out and plant downtime costing potentially thousands of pounds.

We recommend regular thermographic surveys of the following types of equipment:

  • Fuse boards
  • Distribution boards
  • Busbar systems
  • Control panels
  • High voltage and medium voltage systems
  • Power line connections and insulators
  • Switchgear
  • Electronic components
  • UPS and battery systems
  • PLC connections
  • Motor control centres

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.

Some problems that may that a Thermographic Survey may find, that an inspection and test may not, include; Poor or loose connections.

  • 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.

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.

 

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