Up Time Magazine - February/March 2009 - (Page 25) development: geometric factors, spatial factors, and environmental conditions. Other more subtle conditions may also exist, but the three discussed in detail below are the most common contributors to most problems you will face. Geometric factors include sharp edges on conductors, connections, and switchgear cabinet components. These features can include sharp or squared surfaces on conductors (Figure 2), tag ends on conductors, sloppy tape wraps, and corners and other sharp edges on cabinet bracing and support shelves. subject to wet or humid conditions are more likely to have corona and tracking activity over those cabinets that are kept cool and dry. For these reasons, it is important to make sure that cabinet heaters and fans are working properly. Signs of Corona and Tracking There has been much written claiming that the most noticeable sign of corona will be the smell of ozone, since this is, after all, the major by-product of corona. I have not person- ally smelled ozone in switchgear cabinets, but one important reason for this may be that arcflash protective hoods and face shields drastically decrease one’s ability to smell the outside world. So, please, do not use this as the only criteria to determine if corona is present. In a great number of cases, corona and tracking problems can be identified by visual inspection. The trained eye usually can pick out problematic areas by using a flashlight and having an unobstructed view of the equipment. Cables, World Leaders in Infrared Safety Figure 2 - A sharp edge on a piece of copper bus provides an excellent spot for corona activity. Spatial factors include small air gap spaces between, conductors and switchgear cabinet components. Examples of this include: 1) conductors being tie-wrapped together, 2) conductors touching insulators, conduit, and edges of cabinets, 3) non-shielded cables in contact with grounded surfaces, and 4) bus bars in close proximity to insulation board (Figure 3). Concerned about NFPA70E? When it comes to predicitve maintenance of high energy switchgear, Infrared (IR) sightglasses from Hawk IR International provides the safety that you need and the flexibility that you want. Is YOUR electrical thermography to Code? Compliance, Safety and Speed for under $400 Why not? Hawk IR C-Range Quadraband Sightglasses with Arc-Resistant Optics. Designed for high energy electrical systems, the Arc-Resistant C-Range Sightglasses from Hawk IR International have been arc-tested to every major standard to 50kA for a MASSIVE 30 cycles for maximum safety. Compatible with all infrared (IR) and corona (UV) cameras, the Quadraband Sightglass allows you to inspect your energized electrical equipment for high resistance joints (IR) and degrading insulation (UV) without exposing operators to live conductors. Help comply with NFPA70E and keep your power flowing. Figure 3 - Corona deposits resulting from small air gap spaces between insulation board and 13kV bus bars. Finally, environmental conditions can also greatly affect the presence of corona and tracking. Contamination in the forms of dust, oils/fluids, and other particulates on conductors and insulators will create corona. Also, switchgear rooms that are hot because of poor air circulation and cabinet enclosures that are www.uptimemagazine.com Hawk IR International Inc. 2911 Turtle Creek Blvd., Ste. 300 Dallas, TX 75219 Email: sales.ur@hawk-ir.com Toll-free: 1-877-4HAWKIR www.irwindows.com/UR 14/1/09 16:13:36 Uptime ad.indd 1 25 http://www.irwindows.com/UR http://www.irwindows.com/UR http://www.uptimemagazine.com
For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.