Search
Search using google with ads
Described as the "largest most complex machine ever built,"
this page covers commonly visible parts and functioning of the electric grid from generation to end user.
|
Search Search using google with ads
|
Grounding 3-phase distribution Described as the "largest most complex machine ever built," this page covers commonly visible parts and functioning of the electric grid from generation to end user. |
 Larger imageGrounding 3-phase distribution "Standard 142-1991 lists several reasons for limiting the ground fault current by resistance grounding: 1. To reduce burning and melting effects in faulted electrical equipment, such as switchgear, transformers, cables, and rotating machines (motor). 2. To reduce mechanical stresses in circuits and apparatus carrying fault currents. 3. To reduce electrical-shock hazard to personnel caused by stray ground fault currents in the ground return path. 4. To reduce the arc blast or flash hazard to personnel who may have accidentally caused or who happen to be in close proximity to the ground fault. 5. To reduce the momentary line voltage dip occasioned by the occurrence and clearing of a ground fault. 6. To secure control of transient over-voltages while at the same time avoiding the shutdown of a faulty circuit on the occurrence of the first ground fault (high-resistance grounding)." By Larry A. Pryor, P.E., GE Senior Specification Engineer. "... lightning activity can be characterized by lightning ground flash density, expressed in terms of number of lightning flashes to ground per square mile per year. The line itself tends to be a somewhat focused collector of lightning and will attract flashes which would otherwise strike the ground over a swath whose width is approximately four times the average height of the uppermost conductor or shield wire" ... the Neutral or static wire found atop transmission, subtransmission, and distribution poles. If a pole has the 3 Hot wires at the top and Neutral traveling lower on pole, then the line is considered unshielded from lightning. In this case "lightning to unshielded lines involves a strike to one of the phase conductors (hot wires), resulting in line outage. "For properly designed lines, having well located shield wires (as shown in photo), most lightning strikes to the line will terminate on the shield wire. The surge of current will travel along the shield wire until it reaches a structure (pole) where it will be conducted down into the ground'" Transmission surge arrestors .pdf |
 | Buy
from my affiliate links every time/ thanks: Amazon ''As an Amazon Associate I earn from qualifying purchases'' Enter Amazon from any link on my site, fill cart with any item ... purchases pay small commission E-mail: geno03245w@gmail.com My response might end up in spam folder, check email folders Waterheatertimer on Twitter Message thru facebook |