Tel: 01942 397 643 Email: info@applitec.co.uk

Using Thermal Imaging for the Periodic Inspection of Critical Systems

When undertaking periodic inspections, contractors are all too often refused permission to shut down parts or any of the installation to carry out the required tests; the contractor duly records a limitation on the Periodic Inspection Report. The situation can go on for several years and elements of an electrical installation are never assessed, which of course, does not comply with BS 7671 or the Electricity at Work Regulations 1989; electrical installations must be tested and inspected at regular intervals.

The Need For Periodic Inspections

Over time, electrical installations degrade due to a number of factors; loading, overheating, environment,
mechanical damage, wear and tear, poor maintenance etc. It is therefore important that any deficiencies in
the installation are found and corrected as soon as possible.

The Law

The law requires that electrical installations are maintained and kept in a safe condition. The following extract from the Electricity at Work Regulations 1989, Regulation 4, places a duty on employees to provide safe systems for their workers:

Regulation 4 of the Electricity at Work Regulations 1989

Systems, work activities and protective equipment

(1) All systems shall at all times be of such construction as to prevent, so far as is reasonably
practicable, danger.
(2) As may be necessary to prevent danger; all systems shall be maintained so as to prevent so far as
is reasonably practicable, such danger.
(3) Any equipment provided under these Regulations for the purpose of protecting persons at work on
or near electrical equipment shall be suitable for the use for which it is provided, be maintained in
a condition suitable for that use, and be properly used.

Competency

The law requires that the operation, maintenance and testing of electrical systems and equipment should be carried out only by those persons who are competent for the particular class of work. The use of people who are properly trained and competent to work on live equipment safely is a legal requirement.

The following extract from the Electricity at Work Regulations 1989, Regulation 16 defines competency:

Regulation 16 of the Electricity at Work Regulations 1989

Persons to be competent to prevent danger and injury

No person shall be engaged in any work activity where technical knowledge or experience is necessary to
prevent danger or; where appropriate, injury, unless he possesses such knowledge or experience, or is under such degree of supervision as may be appropriate having regard to the nature of the work.

The requirements of BS 7671

One of the essential requirements of BS 7671 is stated in Regulation 130-01-01. This Regulation sets the
scene for Chapter 13, Fundamental Principles. The requirements of Chapter 13 are intended to provide for
the safety of persons, livestock and property against dangers and damage which may arise in the reasonable use of electrical installations. Risk of injury may result from shock currents, excessive temperatures likely to cause burns, fires, other injurious effects and explosion.

It is therefore a requirement to select the correct equipment and install in a suitable manner for the particular application. It is also a requirement that such installations be periodically inspected and tested to ensure ongoing safety.

Chapter 73 of BS 7671, Periodic Inspection and Testing states that, where required, periodic inspection and testing of every electrical installation shall be carried out to determine whether the installation is in a satisfactory condition for continued service.

The frequency of periodic inspection and testing should be determined by taking into account the type of installation, the use and operation, the frequency and quality of maintenance and the external influences to which it is subjected.

The Periodic Inspection

In smaller installations, such as those in domestic properties, the periodic inspection is a relatively straight-forward process. The installation would be under the control of the inspector and they may shut down parts or all of the installation at will to undertake the relevant tests. On larger installations, this is not easy.

Consider an electrical installation in a hospital, hotel or a bank. The duty holder has refused the contractor
permission to shut down parts of the installation for any number of reasons, loss of data, patient safety,
CCTV equipment etc. The contractor would then make reference to this situation on the Periodic Inspection Report. Installations that have such critical loads, like hospitals and banks cannot afford supply failure. Failure of a piece of distribution equipment or a distribution cable, for example, which causes an interruption of supply, could be extremely dangerous as well as financially disastrous for the organization.

Ironically it is those circuits for which permission to isolate is refused are those which require the most scrutiny to ensure that they do not fail…

The contractor cannot insist on shut down to assess the installation but the duty holder still has a duty of
care to ensure that their systems are safe. To comply with BS 7671 and the Electricity at Work
Regulations 1989, the duty holder must make available all parts of the installation for periodic inspection.

Problems and hidden dangers

Visual inspections of electrical installations will pick up most common problems, e.g. if the method of installation is unsuitable for the environment in which it is located, mechanical damage due to impact or abrasion will generally be obvious and any problems associated with wear and tear, such as loose screws or covers, will be clearly apparent.

If elements of the installation are not inspected, problems may therefore go undetected.

Loose terminals, located within an enclosure, can cause overheating in conductors and equipment. The heating effect is due to an increase in resistance across the joints; as heat rises, the insulation can fail which would cause an arc or even an explosion in some cases.

A build up of dust and debris, undetected over time, can cause arcs, tracking, short circuits and faults with equipment. Clearly, this is a major fire hazard.

There are other problems found in electrical installations, which a general periodic inspection would not necessarily discover. Overloaded circuits can also cause overheating in conductors and equipment.

Infrared Thermography is a relatively new technology which allows for assessment of energized electrical installations. Infrared Thermography is based on the principle that all materials emit electromagnetic radiation which can be detected by an infrared camera. The amount of radiated energy detected is translated into temperature information based on the laws of quantum physics. All materials above the hypothetical temperature of absolute zero, (-273.15’c, 0 kelvin) will emit this energy.

In electrical installations, heating effects are created and generated as a result of numerous factors including cyclical-load operations, insufficient cross-sectional area of conductors, types of loads and system deterioration.

A common point of failure, related to heating in electrical applications, is at terminations of conductors. In many cases this is due to an increase in the resistance of that joint or connection which is directly related to the thermal energy that can be identified.

Note that raised temperatures on one or even a number of circuits may not be a cause for concern; some circuits are designed to operate up to 70’C, others may even be designed to operate up to 90’C. Problems deteriorate very rapidly.

An increase in resistance not only creates heat connections and joints, but also fatigues the apparatus reducing useful service life and increases the risk of fire. The increased resistance will cause an increase in power loss at termination, which in turn increases energy costs; again the increase in emission of thermal radiation will be detected by the infrared camera.

This technology provides for early detection of problems and potential catastrophic failure of the equipment and associated components but should not be used as a replacement for regular programmed periodic inspections.

Presenting the findings

Early discussions will establish exactly what the client requires from the inspection. The client should be aware that the use of an infrared camera to assess an electrical installation is not a replacement for an ongoing periodic inspection and testing regime and it does not provide the information required in the Periodic Inspection Report (BS 7671).

Coupled with a periodic inspection this method is over and above the requirements of BS 7671 and will prove to be a valuable maintenance and diagnostic tool.

Links
J & J Rothwell and Son - Gas Safe heating engineers Manchester
Ralos Solar Energy - Alternative heating solutions
GM Brickwork - New build, Extensions, Alterations

Taken from IEE Wiring Matters/Summer 06

	Tel: 01942 397 643 Email: info@applitec.co.uk
	Home Thermal Testing
	Using Thermal Imaging for the Periodic Inspection of Critical Systems
	When undertaking periodic inspections, contractors are all too often refused permission to shut down parts or any of the installation to carry out the required tests; the contractor duly records a limitation on the Periodic Inspection Report. The situation can go on for several years and elements of an electrical installation are never assessed, which of course, does not comply with BS 7671 or the Electricity at Work Regulations 1989; electrical installations must be tested and inspected at regular intervals.
	The Need For Periodic Inspections
	Over time, electrical installations degrade due to a number of factors; loading, overheating, environment, mechanical damage, wear and tear, poor maintenance etc. It is therefore important that any deficiencies in the installation are found and corrected as soon as possible.
	The Law
	The law requires that electrical installations are maintained and kept in a safe condition. The following extract from the Electricity at Work Regulations 1989, Regulation 4, places a duty on employees to provide safe systems for their workers: Regulation 4 of the Electricity at Work Regulations 1989 Systems, work activities and protective equipment
	(1) All systems shall at all times be of such construction as to prevent, so far as is reasonably practicable, danger. (2) As may be necessary to prevent danger; all systems shall be maintained so as to prevent so far as is reasonably practicable, such danger. (3) Any equipment provided under these Regulations for the purpose of protecting persons at work on or near electrical equipment shall be suitable for the use for which it is provided, be maintained in a condition suitable for that use, and be properly used.
	Competency
	The law requires that the operation, maintenance and testing of electrical systems and equipment should be carried out only by those persons who are competent for the particular class of work. The use of people who are properly trained and competent to work on live equipment safely is a legal requirement. The following extract from the Electricity at Work Regulations 1989, Regulation 16 defines competency: Regulation 16 of the Electricity at Work Regulations 1989 Persons to be competent to prevent danger and injury No person shall be engaged in any work activity where technical knowledge or experience is necessary to prevent danger or; where appropriate, injury, unless he possesses such knowledge or experience, or is under such degree of supervision as may be appropriate having regard to the nature of the work.
	The requirements of BS 7671
	One of the essential requirements of BS 7671 is stated in Regulation 130-01-01. This Regulation sets the scene for Chapter 13, Fundamental Principles. The requirements of Chapter 13 are intended to provide for the safety of persons, livestock and property against dangers and damage which may arise in the reasonable use of electrical installations. Risk of injury may result from shock currents, excessive temperatures likely to cause burns, fires, other injurious effects and explosion. It is therefore a requirement to select the correct equipment and install in a suitable manner for the particular application. It is also a requirement that such installations be periodically inspected and tested to ensure ongoing safety. Chapter 73 of BS 7671, Periodic Inspection and Testing states that, where required, periodic inspection and testing of every electrical installation shall be carried out to determine whether the installation is in a satisfactory condition for continued service. The frequency of periodic inspection and testing should be determined by taking into account the type of installation, the use and operation, the frequency and quality of maintenance and the external influences to which it is subjected.
	The Periodic Inspection
	In smaller installations, such as those in domestic properties, the periodic inspection is a relatively straight-forward process. The installation would be under the control of the inspector and they may shut down parts or all of the installation at will to undertake the relevant tests. On larger installations, this is not easy. Consider an electrical installation in a hospital, hotel or a bank. The duty holder has refused the contractor permission to shut down parts of the installation for any number of reasons, loss of data, patient safety, CCTV equipment etc. The contractor would then make reference to this situation on the Periodic Inspection Report. Installations that have such critical loads, like hospitals and banks cannot afford supply failure. Failure of a piece of distribution equipment or a distribution cable, for example, which causes an interruption of supply, could be extremely dangerous as well as financially disastrous for the organization. Ironically it is those circuits for which permission to isolate is refused are those which require the most scrutiny to ensure that they do not fail… The contractor cannot insist on shut down to assess the installation but the duty holder still has a duty of care to ensure that their systems are safe. To comply with BS 7671 and the Electricity at Work Regulations 1989, the duty holder must make available all parts of the installation for periodic inspection.
	Problems and hidden dangers
	Visual inspections of electrical installations will pick up most common problems, e.g. if the method of installation is unsuitable for the environment in which it is located, mechanical damage due to impact or abrasion will generally be obvious and any problems associated with wear and tear, such as loose screws or covers, will be clearly apparent. If elements of the installation are not inspected, problems may therefore go undetected. Loose terminals, located within an enclosure, can cause overheating in conductors and equipment. The heating effect is due to an increase in resistance across the joints; as heat rises, the insulation can fail which would cause an arc or even an explosion in some cases. A build up of dust and debris, undetected over time, can cause arcs, tracking, short circuits and faults with equipment. Clearly, this is a major fire hazard. There are other problems found in electrical installations, which a general periodic inspection would not necessarily discover. Overloaded circuits can also cause overheating in conductors and equipment. Infrared Thermography is a relatively new technology which allows for assessment of energized electrical installations. Infrared Thermography is based on the principle that all materials emit electromagnetic radiation which can be detected by an infrared camera. The amount of radiated energy detected is translated into temperature information based on the laws of quantum physics. All materials above the hypothetical temperature of absolute zero, (-273.15’c, 0 kelvin) will emit this energy. In electrical installations, heating effects are created and generated as a result of numerous factors including cyclical-load operations, insufficient cross-sectional area of conductors, types of loads and system deterioration. A common point of failure, related to heating in electrical applications, is at terminations of conductors. In many cases this is due to an increase in the resistance of that joint or connection which is directly related to the thermal energy that can be identified. Note that raised temperatures on one or even a number of circuits may not be a cause for concern; some circuits are designed to operate up to 70’C, others may even be designed to operate up to 90’C. Problems deteriorate very rapidly. An increase in resistance not only creates heat connections and joints, but also fatigues the apparatus reducing useful service life and increases the risk of fire. The increased resistance will cause an increase in power loss at termination, which in turn increases energy costs; again the increase in emission of thermal radiation will be detected by the infrared camera. This technology provides for early detection of problems and potential catastrophic failure of the equipment and associated components but should not be used as a replacement for regular programmed periodic inspections.
	Presenting the findings
	Early discussions will establish exactly what the client requires from the inspection. The client should be aware that the use of an infrared camera to assess an electrical installation is not a replacement for an ongoing periodic inspection and testing regime and it does not provide the information required in the Periodic Inspection Report (BS 7671). Coupled with a periodic inspection this method is over and above the requirements of BS 7671 and will prove to be a valuable maintenance and diagnostic tool. Links J & J Rothwell and Son - Gas Safe heating engineers Manchester Ralos Solar Energy - Alternative heating solutions GM Brickwork - New build, Extensions, Alterations
	Taken from IEE Wiring Matters/Summer 06
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