Phase Shift Analysis and Phase Identification for Distribution System with 3-Phase Unbalanced Constant Current Loads

Abstract

-Power grids are large complicated networks in use around. An absolute phase value for a particular unknown-phase line at a local site should be identified for the operation and management of a 3-phase distribution network. The phase shift for a specific point in the line, as compared with a phase reference point at a substation, must be within a range of ± 60 o for correct identification. However, the phase shift at a particular point can fluctuate depending on the line constants, transformer wiring method, line length, and line amperage, etc. Conducted in this study is a theoretical formulation for the determination of phase at a specific point in the line, Simulink modeling, and analysis for a distribution network. In particular, through evaluating the effects of unbalanced current loads, the limitations of the present phase identification methods are described.

Prototype Method for the Tracing of Power Transformers and Wires in Distribution Systems

“…4. More details for the Simulink model such as power sources, lines, unbalanced loads, transformers, grounding resister and phase measurement system for phase simulation are simply explained below [2]. In the first, the input source is expressed in terms of power with an internal resistance and inductance.…”

“…Ku's and Shon's methods cannot discriminate wires of 3-phase distribution lines, instead, it is possible to discriminate transformer served to customers [2,9]. Fig.…”

“…When confusion for phases and wires occurs, disproportionate concentrations of loads can easily occur, and this type of disproportionate concentration of loads can cause phase unbalance that can lead to power loss or power failures and, further, equipment failures due to excessive voltage regulation or reduction of useful life, etc. What this would all mean is that it can result in substantial management difficulties such as economic losses, all because of the reduced quality of voltage supplied to the customer [2].…”

“…The determination of an absolute phase is difficult when it is needed on site. For the most recent research of the phase determination, GPS technology is utilized to synchronize time at different locations, which is used to measure the phase for electric signals [2].…”

Cable and Phase Identification based on Power Line Communication

“…As such, most of phase distinguishing methods employ methods that distinguish phases based on comparing the known phase value of a substation with the unknown phase value of a local site [2][3][4][5][6][7]. For the phase determination, GPS technology is utilized to synchronize time at different locations, which is used to measure the phase for electric signals [8].…”