Search results
Results From The WOW.Com Content Network
One voltage cycle of a three-phase system. A polyphase system (the term coined by Silvanus Thompson) is a means of distributing alternating-current (AC) electrical power that utilizes more than one AC phase, which refers to the phase offset value (in degrees) between AC in multiple conducting wires; phases may also refer to the corresponding terminals and conductors, as in color codes.
Overhead power lines are easiest to diagnose since the problem is usually obvious, e.g., a tree has fallen across the line, or a utility pole is broken and the conductors are lying on the ground. Locating faults in a cable system can be done either with the circuit de-energized, or in some cases, with the circuit under power.
In moister climates, tree growth is a significant problem for overhead power lines. ABC will not arc over if touched by tree branches. Although persistent rubbing is still a problem, tree-trimming costs can be reduced. Areas with large trees and branches falling on lines are a problem for ABC as the line degrades over time.
Rural services normally try to minimize the number of poles and wires. It uses higher voltages (than urban distribution), which in turn permits use of galvanized steel wire. The strong steel wire allows for less expensive wide pole spacing. In rural areas a pole-mount transformer may serve only one customer.
The worker is brought alongside the wire in a hovering helicopter and works from that position. As the worker approaches the line, an arc will form between the line and the worker as they are being charged. This arc can be debilitating, and the worker must immediately bond themself electrically to the line to prevent further arcing. [3]
Radial operation is the most widespread and most economic design of both MV and LV networks. It provides a sufficiently high degree of reliability and service continuity for most customers. [ 7 ] In American (120 V) systems, the customers are commonly supplied directly from the distribution transformers via relatively short service drop lines ...
Single-wire earth return (SWER) or single-wire ground return is a single-wire transmission line for supplying single-phase electrical power to remote areas at low cost. It is principally used for rural electrification, but also finds use for larger isolated loads such as water pumps. Single-wire earth return is also used for HVDC over submarine ...
Corona discharges on the 380kV overhead power line over the Albula Pass (Switzerland) in foggy weather conditions (30 second long exposure) Coronas can generate audible and radio-frequency noise, particularly near electric power transmission lines. Therefore, power transmission equipment is designed to minimize the formation of corona discharge.