Distributed Series Impedance Research Articles

Small devices for longitudinal compensation in overhead power lines

Distributed-series impedance (DSI) technology for overhead power lines is under active development in the United States and Russia. DSI can be used for a wide range of application, for example, for redistribution of power flows in parallel lines and cross sections; phase balancing; increasing the power-transfer capability, stability, and reliability of the functioning of an electric-power network; and reducing power losses. This article describes the principles of operation of the DSI and proposes a generalized analytical model, which illustrates the concept of controlling the reactance introduced by means of a device in a power line. The structure of an inductive-capacitive DSI with two capacitors made by OAO G.M. Krizhizhanovskii Energetics Institute in cooperation with AO NTTs FSK EES is described in detail. This work discusses general characteristics and parameters of the device. The main modes of operation of the developed DSI prototypes are presented. The feasibility of the devices has been confirmed during trial operation.

New Approach to Congestion Mitigation Based on Incidence Matrix DCOPF

An incidence matrix approach for mitigating congestion in transmission network is presented in this paper. Based on this methodology, all congested power transmission lines is identified and main economical signals for investment planning is introduced. In this method, we can determine strong and weak transmission corridors in the network. The Flexible AC Transmission System (FACTS) device has been applied to enhance the controllability of power systems. New generations of FACTS device called Distributed FACTS such as distributed series impedance or distributed static series compensator have recently received increasing interests for power system control and are expected to be broadly deployed. This paper presents a detailed formulation and algorithm to find the best location and size of DFACTS to achieve the optimal utilization of transmission capacity to mitigate congestion. This approach can be applied in market simulation and planning owing to its robustness and speed. Unlike, previous admittance based matrix methodologies, which solidly depended on the network topology, independency of network in the presented approach; it would be an effective tool for long-term expansion planning criteria or implementing D-FACTS devices in modern power systems. The simulation results show that the presented method is both satisfactory and consistent with expectation. Simulation results are presented with the PJM 5-bus system to illustrate the capabilities of presented approach in compression with previous works.

Distributed FACTS—A New Concept for Realizing Grid Power Flow Control

Flexible AC transmission systems (FACTS) devices are used to control power flow in the transmission grid to relieve congestion and limit loop flows. High cost and reliability concerns have limited the widespread deployment of FACTS solutions. This paper introduces the concept of distributed FACTS (D-FACTS) as an alternative approach to realizing cost-effective power flow control. By way of example, a distributed series impedance (DSI) and a distributed static series compensator (DSSC) are shown that can be clipped on to an existing power line and can, dynamically and statically, change the impedance of the line so as to control power flow. Details of implementation and system impact are presented in the paper, along with experimental results.

Step-Function Response of a Line with Ground Return - Empirical Vs. Asymptotic Approximations for Impedance

A first-order asymptotic approximation to the distributed series impedance of an overhead transmission line with ground return (frequency-dependent resistance) is insufficient for the prediction of the step-function response at distances of a mile (1. 6km) or more from the source. Series solutions based on a third-order asymptotic impedance approximation have useful convergence properties only for distances up to perhaps three miles. An empirical impedance function, designed to approximate the true function closely over a finite band of somewhat more than one decade, and utilizing corrective terms proportional to √s exp (-k <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> ,√s) and s exp (-k <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> √s), yields a series solution which is usable for much longer distances. These series solutions predict a more rapid rise in voltage than does the first-order asymptotic approximation and they indicate that, at distances of more than a few miles, rise time tends to be directly proportional to the distance.

Generalized Confluent Hypergeometric and Hypergeometric Transmission Lines

A proliferation of exact closed-form solutions of the telegrapher's equation <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V_{xx} - Z_{x}Z^{-1}V_{x} - kZ Y V = 0</tex> for the voltage <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V(x)</tex> in an <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RC</tex> or lossless transmission line, with distributed series impedance <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Z(x)</tex> and shunt admittance <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Y(x)</tex> , respectively, have emerged in recent years. Generalizations of known solutions have been constructed, sometimes using ad hoc methods. A systematic method is described for deriving exact solutions in terms of standard transcendental functions, which yields far more general profiles for <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Z(x), Y(x)</tex> , or <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Z(x)/ Y(x)</tex> than previously given. Examples of the procedure are given based upon Bessel's, Whittaker's, and the hypergeometric equation, and previously derived profiles emerge as special cases of the analysis.