INFRARED WINDOWS APPLIED IN SWITCHGEAR …

1 Fig. 1: The thermal image at left shows an elevated temperature and possible loose connection at the Phase A line terminal of the circuit breaker Fig. 2: Thermographer conducting an IR scan of a low-voltage motor control center unit with the unit door open. INFRARED WINDOWS APPLIED IN SWITCHGEAR ASSEMBLIES: TAKING ANOTHER LOOK David B. Durocher Senior Member, IEEE Eaton Corporation 26850 SW Kinsman Road Wilsonville, OR 97070 USA David Loucks Senior Member, IEEE Eaton Corporation 1000 Cherrington Parkway Coraopolis, PA 15108 Abstract - Maintenance of electrical power distribution assemblies APPLIED in industry has been critical in assuring facility uptime and reliability. One important metric in assuring reliability is electrical terminations of energized conductors. During normal energized service, terminations both at conductor bus joints and at cable terminations are subject over time to thermal expansion and contraction, ultimately resulting in loosened connections and excessive heat.

2 Deteriorating terminations left unchecked will ultimately fail, resulting in electrical hazards for personnel and also costly loss of production. INFRARED (IR) inspection has proved to be an excellent maintenance method used to identifying problems with loose electrical terminations. However, the design of Internal Arc Classified (IAC) SWITCHGEAR assemblies to address arc-flash concerns has changed assembly designs that now limiting line of sight access necessary for IR inspection via WINDOWS . This paper will discuss global Standards, how they affect SWITCHGEAR designs and application of IR WINDOWS , then present some alternative technologies that in some applications may be more suitable. Index Terms Thermal Imaging, INFRARED Camera, IR WINDOWS , Arc-Resistant SWITCHGEAR , Thermal Sensors.

3 I. INTRODUCTION INFRARED inspection has proved to be an excellent maintenance method used to identifying problems with loose electrical terminations. As shown in Fig. 1, an INFRARED camera can effectively survey energized systems and provide a thermal image that identifies a potential problem, in this case a loose terminal at the line side of the molded case circuit breaker at Phase A. This method can be used to pinpoint a potential problem and remedy this issue before a hot spot becomes an equipment failure. Many industrial manufacturing facilities have effectively used INFRARED scanning of both medium-voltage and low-voltage SWITCHGEAR and motor control assemblies as a means of predictive maintenance. Thermal imaging for electrical systems will be performed on a rotational basis for the entire facility and maintenance outages are scheduled on an as-needed basis only after an electrical problem has been identified.

4 Some industry standards including IEEE Standard 1458 Recommended Practice for the Selection, Field Testing, and Life Expectancy of Molded Case Circuit Breakers for Industrial Applications [1] actually recommends the use of INFRARED scanning as a means to detect issues such as the one illustrated above. Fig. 2 shows a plant thermographer conducting a routine thermal scan using a hand-held camera, in this case inspecting a low-voltage motor control center unit with the door open. This method although effective, can present some risks to the person conducting the INFRARED (IR) scan. The emerging understanding of arc-flash hazards of energized electrical systems has changed the way maintenance personnel perform IR scanning of electrical systems. New globally accepted and APPLIED standards such as IEEE Standard 1584 Guide for Performing Arc-Flash Hazard Calculations [2] now have clearly defined the hazards associated with working on or around energized conductors.

5 Application of this Standard includes calculations that determine the magnitude of incident or potential heat energy should an arc flash event occur. PRESENTED AT THE 2014 IEEE IAS ANNUAL MEETING MINING INDUSTRY COMMITTEE VANCOUVER, BC: IEEE 2014 - PERSONAL USE OF THIS MATERIAL IS PERMITTED. ofcadidethPrFiPrcolotimfrorethinbapomPot hthcoimchimanmtadi apIRmsoadasththdityFig. 3: Two diffeoptic at left and The thermal ef the electricaalories per cestance referreefined and worhat the IR carotective Equipig. 2, if the therotection Bounonsidered a loww-voltage sysmes the Flashom the energemoving a covehe worker. II. RTo solve thtroduced IR Wasic configuratolymer/mesh omedia which olymer/mesh IRhis is only suithermography. over, designedmpact. The haracteristics imaging. Introdund the camerameasured is thaarget plus the scussed furthe Problem solvepproach.

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