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Substations call for a predictive approach to maintenancebecause a failure can be costly for end users in terms oflost production and revenues and lead to lower revenuesfor the utility from lost sales due to unreliable service.

Since overheating as well as abnormally cool operatingtemperatures may signal the degradation of an electricalcomponent, thermal imagers provide the predictive capa-bilities required for substation and switchgear maintenance.

Substations and Switchgear

For more information on Thermal Imagersgo to www.fluke.com/thermography

Application Note

Applications forThermalImagers

In the power generation anddistribution industries, the termsubstation is used in manyways. Various outdoor acilitiesranging rom switchyards atgenerating stations to equip-ment at utilities or at industrialacilities that switches or modi-ies voltage, requency or othercharacteristics o primary powerare called substations.

Predictive maintenance (PdM)helps ensure the quality o an end

users electricity by enhancingthe reliability o substations. PdMaccomplishes this increased reli-ability by monitoring equipmentover time in order to isolate

conditions that indicate impend-ing ailure. The goal is to deter-mine whether corrective actionis required and, i so, to take thataction beore equipment ails.

One set o tools or monitor-ing equipment in substations isFlukes handheld thermal imag-ers. Thermal imagers capturetwo-dimensional representationso the apparent surace tempera-tures o electrical componentsand other objects. The cameras

now include IR-Fusion*, a tech-nology that uses a visual, or vis-ible light, image with an inraredimage or better identiication,analysis and image management.The dual images are accuratelyaligned at any distance height-ening details so problems areeasier to spot.*The Fluke Ti20 comes with InSideIRanalysis and reporting sotware with reeupdates or the lie o the product.

What to check and

when?For a detailed outline o main-taining substations and relatedswitchgear assemblies, ollowNFPA Standard 70B, Recom-mended Practice or ElectricalEquipment Maintenance, Chap-ter 8: Substation and Switch-gear Assemblies. That standardexplains that in transormingprimary power, substationsmay provide system protection,

power-actor-correction meteringand circuit switching in additionto changing voltage. Substationsand switchgear inherently operateat high voltages. NFPA standard70E provides additional speciicguidance on procedures and thelevel o personal protective equip-ment required when inspectingsubstations. Thermal inspectorstypically inspect transormers,regulators, switches, circuit break-ers and capacitors among other

components.The time o day is an important

actor in collecting thermal imageso substation components. Read-ings in the stillness o early morn-ing may avoid the eects o solarrelections and wind, which canskew temperature readings. How-ever, in pre-dawn hours loads aregenerally lighter and problems lessdetectable. The training and expe-rience o the thermographer mayalso aect when outdoor IR scansshould be perormed.

What to look for?

Following a thorough inventory othe equipment in a substation, scanthe entire substation yard, savingimages o any known or possibleanomalies. Look especially orsimilar pieces o equipment undersimilar loading that are clearlyoperating at dierent temperatures.For equipment that always has

a high operating temperature,establish a baseline or standardacceptable temperature range tocompare readings to.

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A good thermographicapproach to substation main-tenance is to create inspectionroutes that include all the substa-tions owned by your utility oracility. On a computer, save ther-mal images o each substationcomponent and track temperaturemeasurements over time. That

way, youll have baseline imageswith which to compare laterimages. Doing this will help youdetermine i temperature levelsare unusual and, ollowing correc-tive action, help you determine imaintenance was successul.

What represents ared alert?

Equipment conditions that posea saety risk should receivethe highest repair priority.Beyond that, NETA (InterNa-tional Electrical Testing Associa-

tion) guidelines say that whenthe temperature dierence (T)between similar componentsunder similar loading exceeds15 C (27 F) immediate repairs

should be perormed. NETA alsorecommends the same actionwhen theT between a compo-nent and ambient air exceeds40 C (72 F).

Following this line o thinking,one way to categorize mainte-nance tasks and lag equipmenturgently needing repairs is tomonitor substation equipment orspeciic degrees o temperaturerise above established reerencepoints. Knowledgeable technical,saety and maintenance person-

nel might establish these limits torange rom continue to monitorto correct immediately, withother levels o action such asschedule maintenance or repairas soon as possible in-between.

This approach has been suc-cessul when reerence pointstake into account the dierencesbetween line-o-sight scans(e.g., metal-to-metal contacts inswitchgear) and non-line-o-sight situations (e.g., the internalcomponents o transormers),

where heat is dissipated orobscured rom the direct viewo the thermographer and the IRcamera. In a non-line-o-sightscan, the actual operating tem-perature will be much higherthan the IR camera registers,so the reerence points thatsignal what corrective actionto take must be much lower.Also, abnormally cool as wellas abnormally hot componentsshould be included in the mix.

2 Fluke Corporation Thermal Applications: Substations and Switchgear

Fluke CorporationPO Box 9090, Everett, WA 98206 U.S.A.

Fluke Europe B.V.PO Box 1186, 5602 BDEindhoven, The Netherlands

For more information call:In the U.S.A. (800) 443-5853 orFax (425) 446-5116In Europe/M-East/Arica +31 (0) 40 2675 200 orFax +31 (0) 40 2675 222In Canada (800)-36-FLUKE orFax (905) 890-6866From other countries +1 (425) 446-5500 orFax +1 (425) 446-5116

Web access: http://www.luke.com

2005, 2007 Fluke Corporation.

Specifcations subject to change without notice.Printed in U.S.A. 12/2007 2542593 A-EN-N Rev B

Fluke. Keeping your worldup and running.

Whats the potentialcost of failure?

The costs associated with aailed electrical substation

depend upon many actorsincluding the number and typeso customers aected. Onesource*, estimates the averagehourly cost o downtime acrossall industries at nearly $950,000.

Follow-up actions

Whenever you discover a problemusing a thermal imager, use theassociated sotware to documentyour indings in a report thatincludes a digital, visual-lightimage o the equipment and a

corresponding thermal image.Thats the best way to communi-cate any problems you ound andto make any suggestions or cor-recting them. Following correctiveaction, a new thermal image canbe used to assess the eective-ness o repairs and evaluate thematerials and techniques used.With this inormation, you cancontinuously improve your main-tenance program or substations.

*IT Perormance Engineering and Measure-ment Strategies: Quantiying Perormance

and Loss, Meta Group, Oct. 2000; FibreChannel Industry Association as ound on theWeb site o the Association o ContingencyPlanners, Washington State Chapter: www.acp-wa-state.org.

bag in place.

An imaging tip:

Consider perorming IR scans o substations during the winter and early springmonths rather than during the summer when loading is the highest. In thesummer, it is more diicult or maintenance personnel to get authorization orshutdowns or repairs. However, during peak loading in the summer is whenequipment is most likely to ail. Repairs made in winter and spring will putequipment in tiptop condition to meet the demands o summer.

This thermal image shows hot secondary connections on thetransormer.

Examine transormers, comparing similar connections undersimilar loads.