Fault Impedance Estimation Research Articles

Compensated fault impedance estimation for distance-based protection in active distribution networks

Electric distribution networks are experiencing fast changes mainly due to the integration of distributed energy resources. These changes originate the active distribution networks, where several distributed energy resources are integrated, usually using power converters. In these active networks, the conventional control, operation, and protection schemes used in power systems are unsuitable, and as a consequence, new approaches must be proposed and tested. This paper analyses the distance relay performance in active distribution networks; as the main contribution, a communication-less compensation strategy is proposed to deal with the effects of fault resistance and the distributed energy resources’ infeed and remote currents. The obtained results demonstrate the excellent performance of the proposed compensation strategy aimed at determining the true value of the estimated positive sequence impedance. This compensation can be easily integrated into the software of conventional distance relays to overcome fault resistance, infeed, and remote current effects.

Unbalance compensated distance relay for active distribution networks

Integration of Distributed Energy Resources (DER) into the Active Distribution Networks (ADN) causes issues in conventional overcurrent protection. Additionally, another conventional protection, such as the distance function, has been used, but ADN characteristics require new well-fitted approaches. This paper proposes a strategy to improve conventional distance relays when applied in unbalanced distribution lines. The strategy is based on the relay’s current and voltage measurements and the line series impedance matrix. Different overhead line cases are studied considering several pole geometrical arrangements and fault types. Based on the results, the new set of equations for distance-based protection can achieve a more accurate fault impedance estimation, with a maximum error of 0.1% in the analysed situations and despite the fault conditions. The high proposal performance and the straightforward application make this proposal suitable for the nowadays ADN protection.

Compensated Fault Impedance Estimation for Distance-Based Protection in Active Distribution Networks

Compensated Fault Impedance Estimation for Distance-Based Protection in Active Distribution Networks

Phase distance relaying algorithm for unbalanced inter-phase faults

This study presents a new fault impedance estimation algorithm for inter-phase faults for the purpose of phase distance relaying of extra high voltage (EHV) and ultra high voltage (UHV) transmission lines. The principle is based on the assumption that the fault arc path is predominantly resistive, and the phase angles of the unmeasured fault point voltage and fault arc path current are equal. This is used to construct the fault impedance estimation equation, which naturally prevents the effects of fault arc path resistance, load current, power swing and load encroachment. PSCAD (simulation software) simulation shows the validity of the proposed algorithm.

Ground distance relaying algorithm for high resistance fault

This study proposes a new fault impedance estimation algorithm of phase-ground fault for ground distance relaying based on the negative-, zero- and comprehensive negative–zero-sequence current component. The principle is based on the assumption that fault path is purely resistive, and the phase angle of fault point voltage and fault path current is equal to construct the fault impedance estimating equations for ground distance relay, which can eliminate the effect of fault path resistance, load current and power swing. PSCAD software simulations show the accuracy of proposed algorithm.

Fast and accurate parameter estimation algorithm for digital distance relaying

Response of digital distance relaying depends on the fast and accurate calculation of parameters such as voltage and current phasors and fault impedance. This paper describes a new apparent impedance estimation algorithm that is based on modal components theory. It is shown in the paper that the proposed algorithm has several advantageous features in terms of speed and accuracy over previously suggested symmetrical and modal components based algorithms. The paper discusses a procedure for deriving a fault impedance estimation algorithm that can be used for protecting power transmission lines. The proposed algorithm was evaluated using an alternative transient program (ATP). The program models a power system, simulates many fault conditions on a selected transmission line and generates fault data. The relay software then obtains filtered, scaled and sampled data and calculates fault impedance using the proposed algorithm. The relay characteristic makes trip decisions based on the fault impedance estimates. The paper shows the feasibility of the proposed algorithm for first zone distance protection. Some results of these studies are presented and discussed in the paper.

Further enhancements in the symmetrical components based improved fault impedance estimation method Part I. Mathematical modelling

This paper develops an approach that can be used for further enhancement of the symmetrical components based improved fault impedance estimation method that has previously been proposed by the authors. In addition to discussing the mathematical basis of the new approach, enhanced and computationally efficient performance equations are presented. In view of the recent advancements in optical transducers and high speed optical fibre communications, the new technique uses sequence components of voltage and current samples obtained from both the ends of the protected transmission line. It is also shown in the paper that the new performance equations are independent of fault resistance. The PC based Alternative Transients Program was used to model a six bus system and to generate fault data. The results of performance assessment studies on this new method are presented and discussed in Part-II of this companion paper.

Further enhancements in the symmetrical components based improved fault impedance estimation method Part II. Performance evaluation

An approach that can be used for further enhancing the symmetrical components based improved fault impedance estimation method has been proposed by the authors in Part-I of this companion paper. The PC based alternative transients program (ATP) was used to model a six bus system and generate fault data. The performance of the proposed method was assessed using the generated fault data. The results of performance assessment studies are presented and discussed in this paper. The proposed method was also applied for calculating an exact fault location. It is also shown in the paper that the proposed method provides highly accurate fault location estimates based on the distance relaying information.

95/03686 Second- and third-zone performance assessment of a symmetrical component based improved fault impedance estimation method

This paper presents a continuous distribution method for calculating the reliability indices of a system connected to one or more assisting systems. A multi-parameter distribution consisting of a combination of gamma distributions is used for representing the area generation system models. A cluster-based load model is used for incorporating the hourly load variation and correlation between area loads. Using this load model, one does not need to make assumptions regarding the nature of correlation, i.e. whether perfectly correlated or not. The concept of equivalent generators to represent the assisting systems is used for incorporating the interconnection effects. The most important contribution of this paper is the expression for frequency of loss of load when loads are not perfectly correlated and therefore the system is non-coherent. The results obtained are compared with those of the recursive method for accuracy and efficiency.

Second- and third-zone performance assessment of a symmetrical component based improved fault impedance estimation method

Abstract The performance assessment of a symmetrical component based fault impedance estimation method that has previously been proposed by the authors is discussed in this paper. A brief review of the proposed method is given. The personal computer based Alternative Transient Program was used in these performance assessment studies. Voltage and current signals for various fault conditions were generated by simulating different types of fault on a selected transmission line of a sample power system. These signals were processed, sampled, and used in the proposed method. The apparent impedance of the protected transmission line from the relay location up to the fault point was calculated using the proposed method. These impedance estimates were inserted in R − X plane characteristics to determine the suitability of the proposed method for digital distance protection of the second and third zones. The results of these performance assessment studies are presented and discussed in the paper.

Fault impedance estimation algorithm for digital distance relaying

Fault impedance is one of the major parameters that must be estimated accurately in digital distance relaying application. In this paper, a new algorithm is proposed based on symmetrical components theory. The proposed algorithm has computational advantage over previously suggested symmetrical components based algorithms. A procedure for applying shunt fault conditions to the sequence equations to estimate fault impedance of the protected transmission line is discussed. The Alternative Transient Program (ATP) that is available on personal computers was used in evaluating the proposed algorithm. ATP models a power system and simulates many fault conditions on a selected transmission line. Fault data obtained were used in calculating fault impedance using the proposed algorithm. Fault impedance estimates were inserted in relay characteristics to determine suitability of the proposed algorithm for first zone distance protection. Sample results of these studies which show stable fault distance estimates are presented and discussed in the paper. >

Rule based decision support system for single-line fault detection in a delta-delta connected distribution system

Single-line fault detection, faulted feeder identification, fault type classification, fault location and fault impedance estimation, continue to pose a problem to delta-delta connected distribution systems such as the Los Angeles Department of Water and Power (LADWP) which has over 1500 feeder circuits at the 4.8 kV voltage level. This paper describes a rule based decision support (RBDS) system application to single-line fault detection in a delta-delta connected distribution system. The RBDS system is built from knowledge acquired through exhaustive simulation based on non-arcing type fault situations. It is primarily designed to detect the presence of a fault, identify the faulted feeder, the faulted phase and classify the fault type. It is also designed to gauge the proximity of the fault to the substation and to assess the fault impedance. A fault in the distribution system, upon identification, triggers an alarm with explanatory facility leading to the fault. The RBDS system was tested with different sets of simulated data and proved successful in most cases. Additional tests will be done using field data made available by LADWP. The RBDS system module is a prototype integrated fault detection scheme to be installed in a LADWP distribution substation.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

First-zone performance assessment of a symmetrical component based improved fault impedance estimation method

Abstract This paper describes the first-zone performance assessment of a symmetrical component based fault impedance estimation method that has previously been proposed by the authors. The performance equation of the proposed method is briefly reviewed and various performance assessment techniques are also discussed. The Alternative Transient Program, which is available on personal computers, was used in these performance assessment studies. This Program was used to model a power system and to simulate many fault conditions on a selected transmission line. Fault data thus obtained were used in calculating the fault impedance using the proposed method. Fault impedance estimates were inserted in R-X plane characteristics to determine the suitability of the proposed method for first-zone digital protection. The results of these performance assessment studies are presented and discussed in the paper.

Symmetrical component based improved fault impedance estimation method for digital distance protection Part II. Computational aspects and validation

Part I of the paper ( Electr. Power Syst. Res., 26 (1993) 143–147) on this subject has discussed the design aspects and the basis of the improved method for fault distance calculation. This paper deals with the computational aspects and validation of the fault impedance estimation method proposed in Part I. The performance equations of two fault impedance estimation methods that are based on the symmetrical component theory are reviewed. Also discussed are the computational aspects of these two methods. Instruction execution cycles of a TMS-320 digital signal processor are used to determine the computational requirements of the arithmetic operations of the two methods. A comparative study is also given in this paper. Definite computational advantages of the proposed method over the previously suggested methods based on symmetrical component transformation are demonstrated. The proposed method of Part I is validated using numerical examples.

Symmetrical component based improved fault impedance estimation method for digital distance protection Part I. Design aspects

Recently, distance relays using digital processors have received considerable attention from researchers. The digital processor based distance relays use estimates of fault impedance (distance) in making decisions. Several methods have been suggested in the past that can be used to estimate fault distance. Researchers have proposed symmetrical component, Clark's component and modal component theories for developing distance estimation methods. The approach used in the symmetrical component based methods has resulted in a higher computational burden on the digital processor, which was addressed using special hardware or multiprocessors. In the present paper, an improved method is proposed that also uses symmetrical component transformation. The simplified approach used in the proposed method leads to a computational advantage over previously suggested symmetrical component based methods. The paper derives performance equations that are valid for ten types of shunt fault encountered on transmission lines. The basis for analyzing shunt faults on the transmission line model and developing the fault estimation method is discussed in detail. The proposed method is also validated using numerical examples, the results of which are reported in Part II of this paper ( Electr. Power Syst. Res., 26 (1993) 149–154).