耦合双回线路电弧故障测距的新相模变换方法

输电线路故障测距一直是经久不衰的研究课题。,根据三相系统和同塔双回线系统的阻抗矩阵关系,从能用单一模量反映所有普通三相系统故障的新相模变换矩阵出发,推导出适用于双回线的相模变换矩阵。提出了一种基于新模量变换的双回线故障定位时域算法,该算法利用某一故障模量电弧电压、电流的转移特性来构造测距算法。它具有如下特点:算法在时域中进行,所需的时间窗短,不需要滤波等环节;用最小二乘法来提高测距精度,且测距的精度不受过渡电阻、故障类型及对端系统阻抗变化的影响。大量的电磁暂态仿真结果表明,该算法具有很高的精度。     

Under-Reach Correction in Twin Circuits Without Residual Current Input From the Parallel Line

Mutual coupling poses difficult problems witnessed during single phase to earth fault, in transmission line protection. In parallel lines on the same right of way, mutually coupled zero-sequence circuits cause error in the apparent impedance seen by the relay. This causes the distance relay at one end of the faulty line to over-reach while the one at the other end to under-reach. Incorrect sensing of the ground fault due to zero-sequence voltage inversion caused by mutually coupled zero-sequence network may lead to false trip of the neighbouring healthy line. The paper develops characteristic expressions for effective sequence impedances of twin circuit lines and presents a non-iterative microprocessor based algorithm for fault distance and under-reach estimation in real time, for under-reach correction in basic distance relaying scheme. The residual current measurement from the parallel circuit is not required for this purpose.      

A New Distance Relaying Algorithm for Single-phase-to-ground Faults on Series-compensated Parallel Lines without the Parameter Requirement of Mutual Coupling and Series Capacitor Device

A new distance-relaying algorithm for single-phase-to-ground faults on series-compensated parallel transmission lines is proposed in this article. Fault impedance can be calculated using this algorithm without any parameters requirement of mutual coupling and series capacitor device (series capacitor/metal oxide arrestor/discharging gap). The series capacitor device is simplified as linearized impedance during faults. The parameters of mutual coupling and a series capacitor device can be used as variables in the fault loop equations. Real-time digital simulator tests show that the proposed distance-relaying algorithm can obtain more accurate results than traditional distance-relaying algorithms for series-compensated parallel transmission lines.     

Fault Location for Single-Circuit Line Based on Bus-Impedance Matrix Utilizing Voltage Measurements

Diverse transmission line fault location algorithms have been proposed in the past depending on measurements available. Existing algorithms usually require measurements captured from buses of a faulted line. By taking advantage of the bus-impedance matrix technique, this paper presents a possible fault location approach for single-circuit lines utilizing only voltage measurements from one or two buses, which may be distant from the faulted line. With the addition of a fictitious bus where the fault occurs, the transfer impedances of this bus and other buses are revealed as a function of the fault location. Based on the relationship between the bus voltage change due to fault and the transfer impedance, the fault location can be derived. Shunt capacitance of the line is ignored first and then fully considered based on distributed parameter line model. Electromagnetic transients program simulation studies have shown quite encouraging results.     

A DIAKOPTICAL TECHNIQUE FOR SHORT CIRCUIT STUDIES OF LARGE SIZE POWER SYSTEM NETWORKS

ABSTRACT

The paper presents a diakoptical technique for deriving the impedance matrices required for short circuit studies of large size power system networks by tearing the system into smaller subsystems by cutting appropriate tie lines. The bus admittance matrix is formed for the sequence networks of each subsystem and then modified later by means of diakoptics. The simulation of mutual couplings is taken into account in the zero sequence networks. Only columns of the impedance matrices corresponding to the faulted buses are computed in the proposed technique which is based on factorized bus admittance matrices and full exploitation of sparsity. The proposed technique can either be used in a single–processor computer for sequential solution of torn subsystems or in a multicomputer configuration for a faster solution by parallel processing of torn subsystems. Both symmetrical and unsymmetrical faults are studied by using the proposed technique which produces exact results as the untorn system. No iterative calculations are required as short circuit analysis is basically a linear problem. Included in this paper is a numerical example of a sample test system.     

A new distance relaying algorithm based on complex differential equation for symmetrical components

This paper presents a new digital impedance measuring technique for transmission lines that combines symmetrical components and the complex differential equation of an equivalent fault loop circuit. The phase voltages and currents at the relaying point are transformed into symmetrical components using Fourier filters of short window length. Depending on fault type, an appropriate fault loop circuit is formed, signals of which are the appropriate symmetrical components, while a parameter of which is the positive sequence impedance being a geometrical measure of the distance from the relaying point to a fault. The impedance, however, is measured very fast by on-line solving the complex differential equation originated for this fault loop circuit. Consequently, this approach combines frequency domain estimation of symmetrical components (accurate filtration) and time domain measurement of positive sequence impedance (high speed response).

The presented method suits well the protection of parallel lines against high-resistance faults occurring very close to the far end of a line. A new method is proposed for detecting high-resistance faults and deciding which line out of two parallel lines actually suffers a fault.

The included EMTP test results demonstrate the efficiency of the proposed relaying algorithm.     

电力系统不对称状态计算

本文提出基于补偿原理,充分利用相阻抗(或导纳)矩阵的优点的新方法,可方便地精确计算电网的任何不对称状态,包括可以想像到的复杂故障。     

A practical fault location approach for double circuit transmission lines using single end data

Double circuit transmission lines are frequently subjected to a variety of technical problems from the perspective of protection engineering. These problems are mainly due to the mutual coupling effects between adjacent circuits of the line. In this paper, a new fault location approach for double circuit transmission lines is introduced. It depends only on the data extracted from one end of the line. This practically facilitates implementing and developing this approach, as it needs no information from the other end. The approach is based on modifying the apparent impedance method using modal transformation. Depending on modal transformation, the coupled equations of the transmission line are converted into decoupled ones. This greatly eliminates the mutual effects resulting in an accurate estimation for the fault distance in a straightforward manner. Also the effects of prefault currents, charging currents, and the unknown fault resistance on the estimation accuracy are compensated. The proposed approach was tested via digital simulation using ATP-EMTP in conjunction with MATLAB. Applied test results corroborate the superior performance of the proposed approach.     

利用零序电流倍增特征的不接地系统故障选线

针对中性点不接地系统单相接地故障选线困难的问题,通过母线故障相接地故障转移与中性点接入小电阻的方式来增强故障信息从而选出故障线路.建立了故障转移阶段、并联电阻投入前后各个阶段的零序网络模型,分析了健全线路和故障线路各自的零序电流幅值的变化特征.在中性点小电阻投入、母线开关分闸前后各馈线零序电流幅值变化明显,健全线路零序...     

Adaptive noncommunication protection based on traveling waves and impedance relay

This paper presents an adaptive noncommunication approach for line protections that are able to classify the fault as internal or external with respect to the relay protection zone for most of the faults in radial lines and for all faults in meshed networks. Basically, with a combination of the current traveling waves detected at the relay location due to fault and open switching operations with apparent impedance seen by relay, the remote breaker operation is detected and the faulted line is identified. The protection developed is selective and is not affected by power system oscillations. The system was simulated with the MICROTRAN, the results showing the feasibility of implementing this algorithm.     

New fault-location method for a single multiterminal transmission line using synchronized phasor measurements

This paper describes a new iterative method to locate a fault on a single multiterminal transmission line. The method uses synchronized voltage and current measurements from all terminals. Using positive-sequence components of the prefault and postfault waveforms, positive-sequence source impedances are estimated. Using these source impedances and the line data, the positive-sequence bus impedance matrix (Z/sub bus/) is formed. Using the properties of Z/sub bus/, an iterative algorithm is proposed. The algorithm first identifies the faulted section and then locates the fault on this section. This algorithm is applied to the data obtained from the Electromagnetic Transients Program simulation of a multiterminal transmission line. The simulation results show that the distinctive features of this method are that it performs with very high accuracy for all types of faults at different fault locations and is practically immune to fault resistance.     

500kV输电线路高抗和串补对过电压影响分析

在超高压输电线路中,通常会配置高抗和串补来提高输电线路的输电能力和系统的稳定性,同时也会对输电线路的电压特性造成影响。本文以500 kV A-B线路为例,分析了500 kV输电线路中高抗和串补的投退对于工频过电压、操作过电压以及潜供电流的影响,针对高抗和串补的投退方式、线路不同类型故障以及单双回线运行等方面的因素,进行了多角度的仿真分析和研究。研究结果对电网的运行具有一定的实际指导意义。     

A new dynamic control strategy for power transmission congestion management using series compensation

The growth of electricity market due to increase in demand and infrastructure made the power system more complex. Managing the transmission congestion is one of the main challenges faced by the utilities. To relieve from the bottlenecks, Flexible AC Transmission Systems (FACTS) and Distributed FACTS (D-FACTS) devices can be used in controlling the transmission line power flows. The real power flow control is realized by varying the transmission line impedance. The power flow in transmission line should satisfy inequality constraints to maintain the system in normal state. To achieve this, an algorithm is developed to control the FACTS/D-FACTS devices connected to all the transmission lines of n-bus system. The significant changes required in line impedance which will be deployed by FACTS devices are decided by the algorithm. In this paper, a 5 bus system and a 14 bus system with FACTS devices in all the transmission lines is considered. The transmission lines of the 5 and 14 bus systems are made to be overloaded in different combinations by choosing appropriate loading conditions. The control algorithm is tested on all the overloaded conditions to overcome the congestion. The FACTS devices controlled by the algorithm removes the overloading effect and improve the reliability of the network.     

A NEW DEVELOPMENT OF BUS IMPEDANCE BUILDING ALGORITHM CLOSELY RELATED TO BUS ADMITTANCE MATRIX

ABSTRACT

The bus impedance algorithm was originally developed in 1960 by Brown, Person, Kirchmayer and Stagg [l], viewing the elements of the bus impedance matrix as open circuit parameters of the network. In this paper an alternative formulation based on simple matrix algebra is presented. Only well established simple results of network matrices are used

For any change in the partial network, first, the bus admittance matrix is derived. Then, with proper matrix inversion technique, the corresponding bus impedance matrix is obtained. The development is comprehensive so as to include the effects of mutual couplings, multi line switching, phase shifting components etc.     

不对称三相潮流的对称分量分析法

本文提出了在对称分量坐标中不对称三相潮流的两种求解方法——隐式阻抗矩阵法和解耦—补偿法。这两种方法都能充分利用对称分量坐标中对称元件,诸如发电机、变压器等的解耦特性,提高三相潮流的解算速度。解耦—补偿法则进一步利用不对称输电线路三序之间的弱耦合特性,通过对三序间弱耦合的补偿,实现三序之间的解耦求解,该法还适合于并行计算。算例表明,本文提出的方法具有较快的计算速度和良好的收敛特性。     

Building algorithms for the formation of the bus hybrid matrix

Two algorithms have been developed in this paper to build the bus hybrid matrix through a step-by-step addition of a transmission line to the power system with consideration of mutual couplings between the lines. Formulas have been derived for the addition of a tree branch and a link, when the buses of the added line are referred to impedance and/or admittance form. The procedure developed eliminates the transformation and the tearing algorithms.     

Distribution Line Carrier Sensitivity Analysis Using Bus Impedance Matrix

In a previous paper[1] we described the use of a bus impedance matrix approach for determining the signal strength of distribution line carrier signals. The technique used bus impedance matrices to calculate transimpedances which are the ratios of the voltage at any point on the line to the current injected at any point on the line. In the current paper we apply sensitivity analysis to this bus impedance approach and show how simply new transimpedances can be obtained from the original values when changes in the distribution line are made.     

An accurate fault location algorithm for parallel transmission lines using one-terminal data

An accurate fault location algorithm for parallel transmission lines, using fundamental frequency components of post-fault voltage and current measured at one terminal, is described in this paper. Parallel transmission lines can be decoupled into the common component net and differential component net. In differential component net, the current distributing coefficient is a function of fault distance, and the differential component current at the fault point can be expressed in terms of the current at the local terminal. Therefore, for asymmetrical faults, the phase fault current can also be expressed as a function of local terminal current and fault distance. With the fault boundary conditions for a given fault type, the fault location equations can then be derived. Based on distributed parameter line model, the proposed algorithm achieves superior locating accuracy, with mutual coupling between circuits, source impedance and fault resistance having very little influence on the locating accuracy. The performance of new algorithm is verified by computer simulation results for transposed and non-transposed lines.     

A novel digital distance relaying technique for transmission lineprotection

Parallel transmission lines often pose more difficult protection problems than single lines. In the case of parallel lines, a number of problems arise when using the distance protection. The paper discusses problems associated with parallel line distance relaying schemes and presents a novel technique to overcome these problems. Two relays instead of four are proposed for the double lines, One relay is located at the beginning and another one at the end. Each relay is fed by three voltage and six current signals from the two lines. The suggested technique is based on the comparison of the measured impedance of corresponding phases. So, the complexity of the possible types of faults, high path fault resistance, mutual effects, current in-feed, inter-system faults are solved. Moreover, 100% of line is protected and the problem of balance-point locations is avoided. Alternative Transient Program models the power system and simulates different fault conditions     

A new adaptive PMU based protection scheme fortransposed/untransposed parallel transmission lines

This paper proposes a brand-new adaptive phasor measurement unit (PMU) based protection scheme for both transposed and untransposed parallel transmission lines. The development of the scheme is based on the distributed line model and the synchronized phasor measurements at both ends of lines. By means of eigenvalue/eigenvector theory to decouple the mutual coupling effects between parallel lines, the fault detection and location indices are derived. The two proposed indices are used in coordination such that the internal and external fault events can be distinguished completely. By on-line estimation of the line parameters under the actual power system conditions, the proposed scheme will respond more accurately to power system faults. Extensive simulation results using EMTP have verified that the accuracy of the fault location achieved is up to 99.9%. The proposed protection system responds well and fast with regard to dependability and security. All the results show that the performance of the proposed detection/location indices is independent of fault types, locations, resistance, source impedance, fault inception angles, and load flows