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Mho elements constitute the main component of transmission line protection in North America and many countries overseas. Distance elements based on incremental quantities and derived from the same base equations as mho elements emerged about two decades ago as a way to improve the speed of distance elements. This paper compares the intrinsic protective properties of mho and incremental distance elements,...
This paper discusses the factors to consider for sizing current transformers (CTs) for line protection applications. We first cover CT basics, with emphasis on errors and ac and dc saturation. We also discuss the criteria to avoid CT saturation. Then we analyze the effect of CT saturation on overcurrent, distance, directional, and differential elements. Further, we present the advances in protection...
One of the traditional techniques for detecting power swings uses a dual-quadrilateral characteristic. It is based on the measurement of the time interval it takes the positive-sequence impedance to cross two blinders. Another technique monitors the variation of the swing center voltage approximation. This paper presents a performance comparison between applications of these two techniques in cases...
Fault location information is critical for operating and maintaining transmission networks. Some of the challenges in calculating accurate fault location include fault resistance, zero-sequence mutual coupling, load, system nonhomogeneity, and transmission lines composed of multiple sections with considerably different characteristics. This paper presents a fully automated real-time fault location...
This paper describes a protective relay for fast and reliable transmission line protection that combines elements that respond only to transient conditions with elements that respond to transient and steady state conditions. In this paper, we also present an algorithm that prevents Zone 1 distance element overreach in series-compensated line applications and show how to prevent corruption of the distance...
The difficulties that arise in implementing the time-overcurrent relay characteristic on microprocessor systems are due mainly to two factors. Firstly, data acquisition is usually linear whereas curve scales are logarithmic. Secondly, we have to calculate the main variable, namely the normalized fault current given as the ratio of the measured line current to the preset pickup value in a system in...
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