Series Compensated Transmission Line Protection Using Pscad

2011

This paper is focused on optimizing the distance protection algorithm for series-compensated line. This algorithm requires estimation of three-phase voltage drops across capacitors bank. For this purpose a nonlinear differential equation is solved on-line, applying comparatively low sampling frequency. In order to assure high fidelity of the waveforms reconstruction using the up resampling procedure has been introduced. The other interest of this paper is in impedance calculation based on optimal solution of the fault loop model.

Fault detection during power swing condition is a challenge for stable operation of power system due to several reasons like protection problems, Voltage/current inversion,sub-harmonic oscillations and transients especially if it is series compensated modulation of voltage and current waveforms with swing frequency etc. This paper proposes a negative-sequence current–based technique for detecting presence of fault, classification of fault occurred, estimated zone and location of the fault occurred and the fault inception time with respect to system reference clock during the power swing condition in a series compensated line. In proposed work negative sequence current was analysed as it keeps the other parameters in the system in healthy state. The technique is tested for different series-compensated power systems including a SMIB system and a WSCC-9bus-3machine power system with their different configurations and contingency combinations. Power swing caused by various faults are simulated with PSCAD / EMTDC and MATLAB/SIMULINK and compared with available techniques to prove the effectiveness of the proposed technique algorithm.

Tripping of one circuit of a heavily loaded double-circuit transmission line may lead to tripping of the healthy circuit due to an out-of-step condition. Out of step is resulted by overloading of the healthy circuit. In this paper, a reliable and economical scheme of using series capacitors is proposed to avoid tripping of healthy circuit. Series Capacitors improve the power transfer capability of the remaining circuit by inserting a capacitor in series with the healthy circuit at the same instant of tripping faulted circuit. The insertion of series capacitors SCs improves system stability and prevents system blackouts, in other hand affects the transient performance of distance relays. Elliptical characteristics are proposed to reduce the effects of SCs on distance relays.

Fault detection during power swing condition is a challenge for stable operation of power system due to several reasons. This paper proposes a negative-sequence current-based technique for detecting presence of fault, classification of fault occurred, estimated zone and location of the fault occurred and the fault inception time with respect to system reference clock during the power swing condition in a series compensated line. The technique is tested for different series -compensated power systems including a SMIB system and a WSCC-9bus-3machine power system with their different configurations and contingency combinations. Power swing caused by various faults are simulated with PSCAD / EMTDC and MATLAB/SIMULINK and compared with available techniques to prove the effectiveness of the proposed technique algorithm.

2017

— Increasing the power transfer capability of existing AC transmission lines has been found to have a great impact on systems performance and economy. The paper presents a methodology of series compensation of an AC transmission line and the degrees of series compensation used to increase the power transfer capability of the overhead transmission line and to get adequate control of steady-state voltage and reactive power requirements. The described methodology is based on assumed system design criteria and takes into consideration several schemes of compensation. The compensation effectiveness indexes are used to help in the analysis of the compensated transmission line. The methodology has been practically applied to the artificial AC transmission line and results are also provided in the paper. The methodology and compensation effectiveness indexes discussed in this paper can be applied to any other existing practical system. Subscripts r = receiving end s = sending end

The continuous increase in disturbances on the Cameroon Southern interconnected electric power system resulting in its inability to reliably meet demands due to improperly protected and old unmaintained transmission and distribution systems, insufficient investment and upgrade of infrastructures. Furthermore, rapid load growth and low water levels of the reservoirs create much stress on the power balance problem and on the existing transmission lines. In this paper, a protection system for transmission lines using series capacitors is discussed in detail.

2010 International Conference on High Voltage Engineering and Application, 2010

This paper investigates a new distance protection principle for a transmission line compensated with 3-phase capacitor banks installed in the middle of the line. Series Capacitors (SCs) equipped with Metal-Oxide Varistors (MOVs), when set on a transmission line, create certain problems for its protective devices. Direct application of the classic distance protection (designed for traditional lines) to series-compensated lines results in considerable shortening of the first zone reach and also in poor transient behaviour. In order to overcome these difficulties the new distance protection principle for the first zone has been developed. The detailed model of considered transmission lines including the SCs&MOVs banks as well as the measurement channels has been developed. Using this model, the reliable fault data has been generated for evaluation of the new distance protection principle under variety of fault conditions. The study has shown considerable improvement of series-compensated line protection as a result of applying the developed new principle.

Electric Power Systems Research, 2017

This paper presents a non-unit protection scheme for series capacitor compensated transmission lines (SCCTL) using discrete wavelet transform and k-nearest neighbor (k-NN) algorithm. All the protective relaying functions such as fault detection, fault classification, faulty phase identification and fault location estimation have been considered in this work. Such a comprehensive work providing all protective relaying functions for protection of double circuit SCCTL utilizing k-NN has not been reported so far. The signal processing and feature extraction are done using discrete wavelet transform due to its capability to differentiate between high and low frequency transient components. For fault detection and classification, only approximate wavelet coefficient of current signal up to level 1 has been used; while for k-NN location estimation, both voltage and current signals of the two circuits are decomposed up to level 3 have been used. Finally, the standard deviation of one cycle pre-fault and one cycle post-fault samples of the approximate wavelet coefficients are calculated to form the feature vector for the k-NN-based algorithm. The performance of the proposed technique is evaluated for large number of fault events with variation in fault type including inter-circuit faults, fault inception angle, fault location and fault resistance. The change in position of series capacitor and different degree of compensation has been discussed. The accuracy of the proposed k-NN-based fault detection and classification module is 100% for all the tested fault cases with a decision period of less than half cycle. The k-NN-based fault location scheme estimates the location of fault with ≤1% error for most of the tested fault cases, which is an exceptional attribute of the proposed scheme as compared with 10-15% error of conventional distance relaying scheme.

2013

Tripping of one circuit of a heavily loaded double- circuit transmission line may lead to tripping of the healthy circuit due to an out-of-step condition. Out of step is resulted by overloading of the healthy circuit. In this paper, a reliable and economical scheme of using series capacitors is proposed to avoid tripping of healthy circuit. Series Capacitors improve the power transfer capability of the remaining circuit by inserting a capacitor in series with the healthy circuit at the same instant of tripping faulted circuit. The insertion of series capacitors SCs improves system stability and prevents system blackouts, but in other hand affects the transient performance of distance relays. Then Elliptical characteristics are proposed to reduce the effects of SCs on distance relays.

High Voltage, 2018

In recent years, the inclusion of flexible AC transmission systems (FACTS)-based compensating devices such as a thyristor-controlled series capacitor (TCSC) and a unified power flow controller (UPFC) has been increased in high-voltage power transmission systems due to numerous technical and economical benefits. However, the operation of such FACTS devices introduces harmonics and non-linearity in power system and causes fast changes in line impedance. As a result, the most widely used fixed impedance setting based distance relaying scheme finds limitation in protecting such compensated lines. Significant research has been carried out in recent years to develop new algorithms and methods to address the problem. This paper presents a comprehensive review of recent developments in the protection of TCSC/UPFC compensated high-voltage transmission lines. The relative merits and demerits of each of the available methods are also presented for comparison. Prior to detail review, the impact of TCSC/UPFC on distance protection is evaluated by using data generated through EMTDC/ PSCAD on a 400 kV two-bus test power system. This study can be useful to both academic researchers and practicing engineers to gain insight on the protection of FACTS compensated transmission lines and for further development of newer algorithms. 2 FACTS compensated high-voltage transmission lines: protection challenges The basic configuration and the different operating modes of TCSC and UPFC controllers and their impacts on the distance protection are well documented in [10-16], respectively. However, for the sake of completeness, in this section, the impact of TCSC/UPFC compensated transmission lines on the performance of distance relay is evaluated by using data simulated through EMTDC/ PSCAD on a 400 kV test power system.

This paper analyses the issues of protective relaying for a series compensated transmission line. Two conditional impedances of a fault loop have been proposed for use in the analysis of the overreaching phenomenon and in the distance relaying. The impedances were determined on the base of the fault data obtained from ATP-EMTP simulations. The locus analysis of the steady state fault loop impedances for a variety of conditions has been performed.

The increase in electrical energy demand has presented higher requirements from the power industry during past two decades. In recent years, the highly increasing cost of building new transmission lines, compounded by the difficulty to obtain new transmission corridors, has led to a search for increasing the transmission capacity of existing lines. Use of series capacitors for compensating part of the inductive reactance of long transmission lines increases the power transmission capacity as well as improves the system stability. Transmission line compensation implies a modification in the electric characteristic of the transmission line with the objective of increase power transfer capability. The series compensator is primarily applied to solve load flow problems which may be related to length of line or structure of transmission network. This paper presents an analysis of the location of series capacitor, effect of series line compensation level on the line voltage profile, transferred power and transmission losses. Also it gives information about problem formulation for load flow analysis. For this purpose simple three bus model has been developed in MATLAB/SIMULINK. It gives basic mechanism of series compensation also highlight its benefits for power system.

This paper presents an approach based on S-Transform (ST) and Least Square Support Vector Regression (LSSVR) techniques for predicting the fault location in a compensated power transmission line with the fixed series capacitor. The entropy features of ST matrix are extracted for reducing the dimension of three-phase current signal measured from the sending end of the transmission line. Then, the extracted features are applied as input to LSSVR for determining fault location on series compensated line (SCL). The presented method has been tested using model of a 400kV, 320km transmission line, which is compensated, by a three-phase capacitor bank in the middle. The results show that the proposed method is capable of determining fault location on SCL under wide variations in operating conditions (i.e. fault resistance, fault inception angle, fault distance, percentage compensation level, source impedance and load angle).

iaeme

In this paper, performance evaluation of different schemes for location of fault in series compensated transmission lines are presented. A fault location algorithm using two end measurements and another fault location algorithm using one end measurements for transmission lines with series compensator at midpoint are simulated and results are obtained. Both the schemes are compared on the basis of results and it is found that the algorithm using one end measurements gives more accurate results. ATP-EMTP software is used for modelling of two machine system incorporating MOVs, series compensator and transmission line. The simulation results show the better accuracy and dependability of one end measurement algorithm.