Shri S’ad Vidya Mandal Institute of Technology

College Campus, Old National Highway No.-8,Bharuch-392 001

C E R T I F I C A T E

This is to certify that Shri Patel Talha Anver (roll no:-

05 EL 27) & Shri Parmar Chintan (roll no:-05 EL 31) of

B.E.IV (7th Semester) Electrical engg, Exam No.

has satisfactorily completed his Seminar titled

“THERMOGRAPHY” for the term ending in Nov.-Dec.

2008-2009.

Date:

Signature of Guide

1

ACKNOWLEDGEMENT

I am taking this opportunity to thank all those people who have been a guiding force in their own special way. Their presence has been a strong motivation in accomplishing this task.

My great obligations towards shri H.S.Nankani (Seminar Guide) for providing me the necessary support and feed back during the development of the seminar, which was way beyond my expectations, and it has indeed helped me to identify the best in myself.

I also thanks to my parents and to the greatest GOD for giving me blessing through which I can prepare this whole presentation so successful and effective.

At the end I want to express thanks to all who directly or indirectly involved in suggestions and modifications to improve the seminar.

2

INDEXSr. no Subject Pg. No.

1) Introduction 4

2) Electrical IR basics 5

3) Why electrical thermography? 5

4) Temperature and electrical components

6

5) What electrical distribution should be checked?

General equipment list

7

76) Inspection and equipment 8

7) What is IR thermal imaging 9

8) Principle of thermography Definition Characteristics

10

9) Bolometer 11

10) Exception analysis Exception repair priority

1. Exception eg.: 1 2. Exception eg.: 23. Exception eg.: 3

1212131415

11) Few problems and solutions Oil filled circuit breakers

1617

12) Applications of thermography Transformers Insulators and bushings Conductors Radiators Electric motors A case of motor bearings

18181920212122

13) Benefits of infrared electrical inspections

23

14) Disadvantages 25

15) Conclusion 26

16) References 27

3

INTRODUCTION

What is themography??--->infrared thermography is the science of acquisition and analysis of thermal information by using non contact thermal imaging devices.

Infrared Thermography in Power Engineering Systems. Today’s requirement for an effective maintenance plan has never been so critical to ensure the perfect operation of the power systems. Thermal imaging has evolved into one of the most valuable diagnostic tools to be used for predictive maintenance (PdM).

Thermal imaging, also called thermography, is the production of non-contact infrared pictures from which temperature measurements can be made. This technique is used to detect anomalies often invisible to the naked eye, even while electrical systems are under load. When a connection becomes loose there is a resistance to current that can cause an increase in temperature and subsequent failure of components, potentially resulting in unplanned outages and possible injury. In addition, the efficiency of an electrical grid becomes low prior to failure, thus energy is spent generating heat, causing unnecessary losses. If left unchecked, heat can rise to a point at which connections will melt and break the circuit; as a result fires may occur.

Besides loose connections, electrical systems suffer from load imbalances, corrosion, and increase in impedance to current. Thermography will quickly locate hot spots, determine the severity of the problem and help to establish the time scale in which the equipment should be repaired. Thermography is also particularly useful for inspecting indoor and outdoor components such as motor control centers, substations, breaker panels, switchgear, transformers and circuit breakers. Thermography not only detects high temperatures but can also be used to detect

4

temperatures that have fallen below recommended levels, thus providing a very wide range of functions.

ELECTRICAL IR BASICS

Infrared thermography is used to perform inspections on electrical equipment because excess resistance on electrical apparatus indicates electrical faults such as loose connections, overloaded or imbalanced circuits, faulty breakers, damaged switches, faulty fuses and a wide range of other unwanted electrical conditions. Before an electrical component burns up, it heats up. Thermography is used to see the excess heat (resistance) so that problems can be found and maintenance personnel can act to correct the problem before the component fails, causing damage to the component, safety hazards and/or production downtime.

WHY ELECTRICAL THERMOGRAPHY?

Simple we all know as soon as new electrical components are installed they begin to deteriorate. No electrical system is 100% efficient. Current flowing through an electrical system will generate a small amount of heat because of electrical resistance. With time, the components and contact surfaces of the electrical system will begin to deteriorate. With the deterioration comes increased resistance and with resistance, increased heat. This course will continue until eventual failure. Fluctuating and high loads, vibration, metal fatigue, age and specific operational environments such as extreme ambient temperatures, wind, chemicals or dirt in the atmosphere will increase the speed of degradation and

5

the number of faults in electrical systems. The defect will normally alter the thermal signature at the component surface due to the change in the amount of heat generated and the heat transfer properties of the component. These faults, if not found and taken care of, will lead to catastrophic failures, unplanned shutdowns and losses of production. Once a clear understanding is obtained on what the normal thermal signature is for the many electrical apparatuses and components, the thermography technician will be able to quickly identify a thermal anomaly. On larger more critical components such as transformers, circuit breakers, capacitors etc., the baseline images and data will be stored and compared to new data collected from each inspection interval. It is the job of the thermographer to identify, record, analyze and diagnose indications of abnormal heat transfer in the electrical equipment or components.

It is important that the data collected is accurate, repeatable and is properly analyzed. This depends on many variables; the main one is the thermographers’ level of understanding of infrared instrumentation, background theories and the level of field experience.

TEMPERATURE AND ELECTRICAL COMPONENTS

Many fires in industry are directly related to faulty electrical components. Costly Downtime is also often contributed to electrical failures and problems. The principle behind an electrical fault is very simple, as a connection deteriorates the resistance to the flow of electrical energy increases. This electrical energy is transformed into thermal energy, which shows up as increased temperature. Wherever there is increased resistance caused by a condition such as a bad

6

connection or overload, it will show up in the infrared image as a brighter spot.

Temperature is an excellent indicator to the operating condition and hence the reliability and longevity of an electrical component. It is well understood that the life of electrical components and materials is drastically reduced as temperatures are increased.

WHAT ELECTRICAL DISTRIBUTION EQUIPMENT SLOULD BE CHECKED?

Utility substations, transformers and feed poles Main incoming services, plant main knives, capacitor

banks, etc Main switchboards and disconnects Main distribution panels and main disconnects Uninterruptible power supplies Generator controls and transfer switches Main I-Line panels Lighting and receptacle panels Disconnects and combination starters Service disconnects for motors Machine control panels

General equipment list:-Rotating machinery/loads

Motors & Generators Pumps A/C units Fans Gear boxes Motor controls & adjustable speed drives Lighting & Electrical systems

7

Switchgear Transformers Cables/wiring Switches & Circuit breakers Grounding systems & Ground fault protection Surge arrestors Power factor correction Filters and reactors Outdoor bus structures Emergency systems

o UPS o Generators

INSPTECTION AND EQUIPMENT

Frequency of inspection derives from a number of factors, including safety, the criticalness of the equipment, the expense of a failure, and the frequency with which problems impact production and/or maintenance.As assets age, are heavily loaded, or are poorly maintained, inspections may become more frequent. When repairs or modifications to equipment happen, conduct a follow-up inspection.

Equipment type Max. time between inspections

Transformers 12 months

440V motor control centers-

Air-conditioned-

Non-air conditioned or older

6-12 months

4-6 months

Electrical distribution equipment

4-6 months

8

Large motors 12 months

Smaller motors 4-6 months

what is IR Thermal Imaging?

Thermal images are pictures of heat rather than light. The technology is based on the fact that any object whose temperature is above 0 °K radiates infrared energy.

An IR thermal imager captures a portion of this radiated energy and provides a calibrated temperature presentation. Through a variety of scanning techniques, a spatial map of temperatures is generated and displayed or saved as a computer file. The computer-compatible file format is available for subsequent manipulation, display or for process control.

Thermal imaging systems are available with a wide range of capabilities, features, form factors and prices. Scan speeds can range from "real time" to seconds per image. Systems sensitive to 3-5 and/or 8-12 micron wavelength bands are available. Detectors range from simple, single element, thermo- electrically cooled to large format focal plane arrays

9

operating at room temperature. Thermal sensitivity of less than .1° C is available.

Image structure ranges from 30K to >250K pixels per image; spatial resolution can be as fine as 25 microns. The technique has been used for years by military, law enforcement and firefighting agencies and is increasingly finding commercial uses in process control, reliability and non-destructive testing (NDT).

Principle of thermography

Fig.2

Camera detects infrared emitted from an object with the help of a sensor or detector called micro-bolometer

It transfers the amount of energy into the temperature

It displays as infrared images

10

Fig.1

Definition of infrared thermography:Infrared thermography is equipment or method, which detects infrared energy emitted from object, converts it into temperature, and displays image of temperature distribution. To be accurate, the equipment and the method should be called differently the equipment should be called infrared thermograph and the method should be called infrared thermography.

Characteristics of infrared thermography:

1) It captures as temperature distribution on a surface, and it can display as a visible information

2) Temperature can be detected from a distance without contacting an object.

3) Temperature can be measured in real time.

BOLOMETER:-

Bolometer is a device for measuring the energy of incident electromagnetic radiation. It was invented 1878 by an American astronomer Samuel Pierpont Langley. It consists of an "absorber" connected to a heat sink (area of constant temperature) through an insulating link. The result is that any radiation absorbed by the absorber raises its temperature above that of the heat sink—the higher the energy absorbed, the higher the temperature will be. Temperature change can be measured directly or via an attached thermometer (composite design).

11

The bolometer used in thermographic cameras or infrared cameras is called micro bolometer.

A microbolometer is a specific type of bolometer used as a detector in a thermal camera. Infrared radiation with wavelengths between 8-13 μm strikes the detector material, heating it, and thus changing its electrical resistance. This resistance change is measured and processed into temperatures which can be used to create an image. Unlike other types of infrared detecting equipment, microbolometers do not require cooling.

Cross-sectional view Of a micro-bolometer

Fig.3

EXCEPTION ANALYSIS

12119.7°F

179.5°F

120

140

160

AR01

SP01

Below is an exception. One of the conductor terminals is hot. Hot Terminal Temperature…..203° FLeft Terminal Temperature….156° FTemperature difference is …… 47° F

Fig. 4When should you repair this exception?

EXCEPTION REPAIR PRIORITY CRITERIA-

Priority 0:- Temp. 10F or less – no corrective measures required at this time.Priority 1:- Temp. 10F to 20F – corrective measures required at next maintenance period.Priority 2:- Temp. difference 20F to 30F – corrective measures required as scheduling permits.Priority 3:- Temperature difference 30F to 100F – corrective measures required as soon as possible.Priority 4:- Temperature difference over 100F – corrective measures required immediately.

Exception example # 1:-

13

Hot Spot Temperature…...203F

Reference Temperature….156F

Temperature Difference….47F

Repair Priority 3Corrective Measures

Required As Soon As Possible

119.7°F

179.5°F

120

140

160

AR01

SP01

Breaker connections

Fig. 5

Exception example #02Fuse Block

14

87.8°F

232.4°F

100

150

200

AR01

SP01

Hot Spot Temperature…...303FReference Temperature….170FTemperature Difference….133F

Repair Priority 4Corrective Measures Required

Immediately Fig. 6

Exception example #03Motor drive end bearing hot

15

Hot Spot Temperature….127F

Reference Temperature…99F

Temperature Difference..28F

Ambient Temperature….74F

Repair Priority?

Mechanical System

Fig. 7

FEW PROBLEMS AND SOLUTIONS

Oil filled circuit breakersA hot spot was identified on the test tap cover of the A phase, The hot spot exhibited a ΔT of 12°F when compared with B and C phase tap covers on the same OCB.

Visual inspection indicated a slight oil leak near the bottom of the cover

16

• Oil leaks out of tap compartment.• Moisture gets into tap compartment.• Electrical breakdown occurs along the porcelain cone surface.• As tracking or arcing continues, deeper erosion occurs in the cone.• If erosion continues and compromises the porcelain cone, tracking could pass to an adjacent compartment, causing an explosion and resulting in catastrophic failure.

This is a good example of a relatively low temperature differential that could have caused major equipment damage and lost production.

17

Oil circuit breaker Infrared image

Fig. 8

Test tap cone Tracking within the test tap cone

Fig. 9

APPLICATIONS OF THERMOGRAPHY

Transformers:-

18

Thermography is based on the fact that majority of the components show an Increase in temperature when malfunctioning.. This abnormal rise in temperature will be reflected on the surface as hot spots. The thermography study can detect the hot-spots immediately without any physical contact with the object. The maintenance activity can be planned depending upon the severity off the defect found. All major transformers should have a normal thermal signature. Once it is known, transformers can be analyzed for fluid levels, clogged cooling tubes, internal and external connections, internal arcing and general overheating. Air cooled transformer coils can be evaluated for overheating or imbalance as well as connection problems.

Transformer Infrared image showing damaged spots (bright colour) Fig. 10

19

Insulators and Bushings:-

Problems with cracks or improper joints have been found in certain insulators that affect the electrical and mechanical strength of the insulator. When surface moisture is present, a very small discharge current flow over the surface of the insulator raising the temperature. When an insulator is cracked, the discharge current flows down the crack and not over the surface and the insulator shows up Slightly colder. Due to improper connections the local heating may give rise to hot-spot.

Infrared image of Transformer bushing

transformer bushing

Fig. 11

20

Conductors:-

Infrared thermography is used to indicate general overheating due to overloading or undersized cables, high resistance, poor connections and bad splices. Excessive heating along a conductor may indicate an over loaded conductor. Unbalanced load on a three--phase system with one conductor warmer than the others will account for some differences between conductors.

Fig. 12

21

27.0 27.0

29.5 29.5

32.0 32.0

34.5 34.5

37.0 37.0

39.5 39.5

42.0 42.0

44.5 44.5

47.0 47.0

RG:1 : 1. 00 SC: OFF

(100.0)

(-20.0)

07/08/31

11:46:41Max:40.6

a40.6

b29.9

Radiator:-

Heat dissipation is due to natural convention of the oil, more temperature is observed at the top of the radiator and it gradually reduces towards bottom. No variation along the cooling surface shall be observed in any clogged tube or chocked fins. These problems can be easily identified.

Fig. 13Electric Motors:-

Thermal imaging can also help you track the temperature at which your electrical motor is operating, which is crucial to the longevity of the motor. For example, for every 10¬*C above allowable maximum operating temperature, the life of the motor is reduced by half. This damage is irreversible. In many industries, this can amount to thousands of dollars a year in lost profit. There is a wide variety of equipment that can be included in an infrared mechanical inspection program, such as: motors, pumps, fans, bearings, generators, compressors, conveyor systems etc.

22

32.9 32.9

34.9 34.9

36.9 36.9

38.9 38.9

40.9 40.9

42.9 42.9

44.9 44.9

46.9 46.9

48.9 48.9

RG:1 :1.00 SC:OFF

(100.0)

(-20.0)

07/06/16

11:15:26Max:48.5

a46.9

b37.1

All cable runs, bus ducts, distribution panels, motor control centers etc. should be checked to hotspots or heat imbalances. This can identify loose connections, overloads, unbalanced loads, and high neutral currents that need to be corrected.

A case of motor bearings:-

Start with a newly commissioned and freshly lubricated motor, and take a "snap shot" of the motor bearing housing while the motor is running. Use this image as a baseline.As the motor and its lubrication ages, the bearings wear and heat-producing friction develops in the motor bearing, causing the outside of the bearing housing to heat up. Take additional thermal images at regular intervals, comparing them to the baseline to analyze the motor's condition. When the thermal images indicate an overheating bearing, generate a maintenance order to replace or lubricate the bearing housing and reduce or eliminate the possibility of costly engine failure.

Fig. 14

23

BENEFITS OF INFRARED ELECTRICAL INSPECTIONS

With most problems on an electrical system are preceded by a change in its thermal characteristics and temperature, whether hotter or cooler, a properly trained and experienced thermographer is able to identify and analyze these problems prior to costly failure occurring. Infrared electrical inspections provide many benefits to the recipient. The two keyadvantages, from which the others stem, are:

1) The reduction in disassembling, rebuilding or repairing components, which are in good operating condition. This type of repair is meaningless and costly and may lead to a 30 percent reduction of production. Furthermore, it is not guaranteed that the component will be in better condition after the repair, since the location of the problem or cause was not established. With infrared thermography you identify and hence repair only what needs repairing.

2) Problems that truly exist will be identified quickly, giving time to repair the problem before failure. In most cases the problem is identified well before the problem becomes critical. Depending on the temperature and criticality of the component, the decision can be made to repair immediately, repair at the first opportune time, or monitor on a continual basis until the critical temperature is reached or until the repair can be

24

scheduled. Identifying a true anomaly, scheduling the repair, and eliminating the actual cause of the problem within a proper time frame is the most efficient and cost effective way to maintain the system.

The other advantages of an infrared inspection program are based on the above overall advantages, yet are no less important. They are:

1) Safety - failure of electrical components could be catastrophic, injuring or even killing employees, maintenance personnel or the public.

2) Greater system security - locate the problems prior to failure greatly reduces unscheduled outages, associated equipment damage and downtime.

3) Increased revenue - with more uptime, revenue is maximized. With less maintenance on good components and faster repairs of faulty components, maintenance costs care is reduced leading to a better bottom line.

4) Reduced outage costs - the cost of an emergency outage is ten times greater than planned maintenance.

5) More efficient inspections - since all common electrical problems announce themselves as an increase in temperature, they are easily detected in a minimum amount of time. No service interruption is required for infrared inspections.

6) Improved and less expensive maintenance - a) Precise pinpointing of problems minimize time required for predictive and preventive maintenance, b) Maintenance efforts directed to corrective measures rather than looking for the problem,

c) Repair only what requires repairing, reducing repair time and replacement of good components.

25

7) Reduce spare parts inventory- with improved inspection techniques giving advanced warning of failure, fewer spare parts are required in inventory. What would it mean to the bottom line if your spare parts inventory could be reduced by 10%?

8) Reduced operational costs- with the system up and running for longer periods of time, the reduction and improvement of inspections, maintenance, spare parts inventory and outages will reduce the overall cost of operations.

DISADVANTAGES

1) Cameras are expensive and are easily damaged2) Images can be hard to interpret accurately even with

experience3) Accurate temperature measurements are very hard to

make because of emissivities.4) Most cameras have ±2% or worse accuracy.5) Trained employees are required.6) Ability to only measure surface areas

26

CONCLUSION

Understanding the effect of heat on the reliability of electronic products and the integrity of manufacturing processes is critical if problems are to be avoided. This means the need to understand thermal management techniques and the need for comprehensive data has never been greater. The tools used in the past, contact probes, thermocouples, fingers can't provide this thermal data quickly or cost effectively. With the availability of thermal imaging systems the engineer can now perform the required analysis in a timely fashion without delaying product development schedules, or interfering with a manufacturing process.

1)Thus with the help of thermography we can detect faults

2)The faults can be repaired well in advance.3)Permanent damage is avoided.

27

4)Other than electrical application there are many other applications.

5)They can be used in medical fields, mechanical field, and many more fields.

REFERENCES

1)www.temperatures.com2)www.wikipedia.com3)www.fsiir.com4)www.compix.com5)www.irananalyzers.com6)www.wikipedia.org7)www.nde2007.com

28

29