Protection Of Double-circuit Lines Research Articles

A standby protection scheme to complement transverse differential protection of double circuit lines in the case of one parallel line tripped

Transverse differential protection of double circuit lines has limited application since both parallel lines are required to be simultaneously in operation. In field applications, it is common to trip one of the parallel lines due to automatic reclosing, permanent fault, maintenance, etc. During these events, it is necessary to block transverse differential protection. A new standby relay protection scheme based on overcurrent and directional elements is proposed as a solution to the previous issue. The newly proposed directional element is based on the detection of variations in phase angles of line currents during the fault and it does not require voltage signals. Its application is limited to radial power flow networks with pre-fault current direction known. The algorithms selectivity has been verified for various fault types and locations on an untransposed distributed three-phase model of a double circuit line. Additionally, the proposed protection scheme has been tested using recorded fault current signals obtained from the experiments performed on the scaled model of double circuit lines in the relay protection laboratory. The proposed algorithm proved to be a promising solution to complement transverse differential protection of double circuit lines in the case of one parallel line tripped.

Fault location in UPFC compensated double circuit transmission line using negative sequence current phasors

Double-circuit transmission lines are used in modern power systems to enhance the transmission capability and to improve system reliability and safety. However, the protection of double-circuit lines is a challenging task as the presence of flexible ac transmission system (FACTS) in modern power grid impairs the performance of the conventional distance protection schemes. Moreover, the high impedance faults cannot be detected by relays as they become under-reach. This paper proposes a negative sequence current based scheme for locating faults and identifying faulty circuit/ line in double circuit transmission line compensated by UPFC at one end. In the proposed scheme the current signals are collected from both ends of the line to be protected. Then the negative sequence components of the currents are calculated. The discrimination between internal and external fault is achieved from the phase angles of the negative sequence currents and the fault location is determined from the ratio of the negative sequence currents. Prior knowledge about the type of fault is not required for fault location estimation. Extensive fault simulation studies including high impedance faults have been performed. The scheme is immune to the fault inception angle and fault resistance.

Protection of Double-Circuit Line with Thyristor Controlled Series Capacitor Using Principal Component Analysis

In this paper, a fault direction estimation algorithm is proposed for a double-circuit line with thyristor controlled series capacitor (TCSC) using principal component analysis (PCA)-based technique. In case of PCA, an orthogonal transformation is used to convert correlated variables into linearly uncorrelated variables called principal components. Fault in such a compensated line leads to voltage inversion, current inversion, and subsynchronous resonance situations, which affect the performance of the conventional direction estimation process. Transients associated with metal oxide varistor (MOV) operation and control action associated with TCSC, further modulate equivalent impedance of TCSC and MOV combination. In the proposed approach, PCA of angles between positive and negative sequence components of voltage current has been carried out to extract the pattern and to declare the fault direction accurately. The double-circuit line with TCSC is simulated using PSCAD/EMTDC software. The performance of the proposed technique is tested for numerous test cases, and it was found to be accurate.

Directional relaying for double circuit line with series compensation

In this paper, a directional relaying algorithm for the protection of double circuit line with series capacitor is presented. The method uses four classifiers based on positive and negative sequence components which are combined with a voting technique to derive the direction of fault. The technique is evaluated using data simulated with electromagnetic transients including DC/power system computer added design (EMTDC/PSCAD) for a series compensated double circuit line. Results for voltage inversion, current inversion, high resistance far end fault, single pole tripping and cross country fault are presented. The proposed technique is found to be accurate.

Classification of Single Line to Ground Faults on Double Circuit Transmission Line using ANN

Abstract— This paper discusses the potential application of ANN techniques for detection of single line to ground faults and fault type classification on double circuit transmission lines with remote end infeed. Distance protection of double circuit transmission lines has been a very challenging task. The problems arise principally as a result of the mutual coupling between the two circuits under different fault conditions. An accurate algorithm for fault detection and classification of single line-to-ground faults (A1N, A2N, B1N, B2N, C1N & C2N) in double circuit transmission line considering the effects of mutual coupling, high fault resistance, varying fault location, fault inception angle and remote source infeed is presented using feed forward neural network (FFNN) algorithm. The algorithm employs the fundamental components of voltage and current signals. This technique neither requires communication link to retrieve the remote end data nor zero sequence current compensation for healthy phases are required. This is a major advantage of the proposed algorithm for protection of double circuit line fed from both the ends. Results of study on a 220 kV transmission line are presented as an illustration. Simulation results indicate that algorithm is immune to the effect of mutual coupling, fault type, fault inception angle, fault resistance, fault location and remote end infeed. Index Terms— Artificial neural network, Double circuit transmission line, Fault detection & classification, High impedance fault, Single line-to-ground fault.

Adaptive Nonconmunication Protection of Double Circuit Line Systems

This paper presents a new technique for non-communication protection of double circuit lines. In the technique, the sequence and super-imposed signals are used to detect the remote circuit breaker operation, from which whether a fault is inside the protected section can be derived. Extensive simulation studies with respect to typical double circuit transmission line systems show that the proposed technique is able to fast and correctly determine whether a fault is inside the protected line section without the need for communication links.

Enhanced double circuit line protection

This paper describes a double circuit line protection relay which has all 6 line currents and voltages available for processing. This allows several alterations to the standard 3-phase distance package which enhance the performance of the protection system. Results are presented for the relay fed with simulated waveforms from a Playback Simulator. The system used in the simulations is modelled on a 69 kV parallel line in the Winnipeg Hydro network.

A nonpilot phase selector based on superimposed components for protection of double circuit lines

This paper gives details of a new phase-selection scheme for simultaneous phase-ground faults on both circuits of double circuit EHV transmission lines. Fast phase selection (within half a cycle) can be achieved by using the information contained within the fault transients. The theory is presented along with results obtained through simulations using EMTP. The scheme enables single pole tripping to be employed for simultaneous faults. The proposed scheme does not require communication between the two ends of the line. Limitations due to the low bandwidth of CVTs have not caused problems and the method has shown immunity to system noise.

Adaptive Distance Protection of Double-Circuit Lines using Artificial Neural Networks

Adaptive Distance Protection of Double-Circuit Lines using Artificial Neural Networks

Travelling-wave-based protection of double-circuit lines

Double-circuit current comparison protection (DCCCP) is an algorithm for travelling-wave-based protection of a double-circuit high-voltage line. It uses the balance between the two circuits to distingush between an internal fault and an external disturbance. To prevent incorrect trips superimposed currents are used, and the relay has to be blocked after detecting an external disturbance. The setting of relay parameters is discussed, as well as its performance. The tripping time is between 100 and 200 μs for the majority of faults. For faults around voltage zero, the tripping time is between 1 and 3 ms, depending on the amplitude of the short-circuit current. Faults close to the remote line terminal are not detected at all. Some direct lightning strokes will lead to an incorrect trip. To overcome the disadvantages of DCCCP, it is combined with travelling-wave-based differential protection in a protective scheme. Differential protection is a somewhat slower but very reliable backup. Its parameter setting is discussed, as well as its performance. The tripping time is between 1 and 3 ms. The protective scheme further contains fast reclosure, breaker-failure detection and adaptive setting for the backup relays.

Variable-characteristic generalised techniques for distance protection: Double-circuit-application studies

A previous paper outlined the principles of a new method for dynamically varying the shape of polarised quadrilateral relay characteristics for the protection of e.h.v. transmission lines. The present paper extends these methods to the protection of double-circuit lines. Consideration is given to the compensation of earth-fault relays, and it is shown that compensation schemes which ignore the effect of mutual coupling between circuits are desirable. Digital-computer application studies of a typical double-circuit 400kV transmission line of earthed construction indicate that, from the point of view of accuracy and fault coverage, there is little advantage in the use of variable devices in zone 1. However, they enable a greater proportion of the protected feeder to be covered with minimum fault-detection time. Emphasis is placed on the response of relays connected to healthy conductors, and the possibility of avoiding unwanted tripping emerges. A high degree of immunity to maloperation during heavy-circuit loading and power swings is achieved.