Transformer Internal Faults Research Articles

Receding Horizon Observer Approach to Fault Detection in Electrical Transformers

Internal transformer faults could cause severe damage to electrical networks and also deteriorate the energy quality standard. Most of existing approaches for fault detection in transformers are based on signal processing methods or a static parity check of functionality. Two analytical redundancy approaches one based on dynamic parity checs and a second using a receding horizon observer, to internal fault detection in transformers are proposed in this paper. The main advantage of our proposal is that explicit knowledge of the Lipschitz constant of the transformer nonlinearities is not required and the considered algorithms has a high degree of portability. Furthermore, the effect of load and external faults on the residual are decoupled. Stability properties of the model are demonstrated. Some simulations shown the efficiency of the proposed detection method and highlight the reliability of the considered approach.

PCA based protection algorithm for transformer internal faults

In this paper a new protection scheme is introduced to detect and identify transformer winding faults. The new approach is based on artificial neural networks (ANNs) using radial basis functions (RBFs) and the principal component analysis (PCA). The nonlinear system's input and output data is manipulated without considering any model of the system. This approach is used to detect and identify internal short circuit faults of a three phase custom built transformer. The suggested technique is also able to distinguish between the fault and magnetizing inrush current. The test studies carried out shows that the proposed method leads to satisfactory results in terms of detecting and isolating parameter faults taking place in non-linear dynamical systems.

Transformer Internal Faults Simulation

Abstract —this paper presents a novel method of modeling internal faults in a power transformer. The method leads to a model which is compatible with commercial phasor-based software packages. Consequently; it enables calculation of fault currents in any branch of the network due to a winding fault of a power transformer. These currents can be used for evaluation of protective relays' performance and can lead to better setting of protective functions. Index Terms —Transformers, transformer windings, modeling, short circuit currents, internal fault I. INTRODUCTION Here is an ongoing need to develop analyses and systems for better protection of power systems. Transformers are widely used in the power system and are among the most important and the most expensive equipments. Failure of a power transformer may lead to loss of power in parts of a system, which can be costly and inconvenient for customers. Therefore; the protection of power transformers is of high importance. The internal short circuit currents for a transformer may be larger than its terminal short circuit currents. Accordingly, high current stage protection is used in transformer differential protection in order to protect transformers against such large internal short circuit currents immediately. Therefore, for adequate power transformer protection, an accurate method of calculation of internal faults should be available. There are several researches in the area of simulation of internal faults in a power transformer [1]-[4]. Nevertheless; all of these methods consider that the transformer is separated from the network. However; transformers are always used inside an actual power system. Therefore; the contribution of the network in an internal fault in a transformer should be regarded. Moreover; none of the previous methods is capable of considering the transformer internal faults in short circuit analysis, and none has been addressed in the practical fault analysis standards (such as IEC, IEEE, etc.). Calculation of fault currents due to a winding fault of a power transformer, not only at the terminals of the power transformer but also in any branch of the network, was the motivation for doing this study. This paper presents a method of modeling internal faults of power transformers in phasor-based fault analysis. The model is fully compatible with software packages which are using phasor-based fault analysis. Moreover; it considers the contribution of the network surrounding the transformer, and can calculate the fault currents in any branch of the network. The winding fault can be single phase to ground or two phase to ground or three phase to ground. Although internal two phase to ground fault and three phase to ground fault rarely happen in a power transformer, the model enables calculation of fault currents in these situations too. II. TRANSFORMER MODEL

Modeling and detection of transformer internal incipient fault during impulse test

Incipient faults are low magnitude and fast decaying transients, lasting only for a few microseconds during impulse tests of transformers. They are very difficult to detect, even for experts, and may cause severe problems leading to faults and consequent outage. Thus, simulation and diagnosis of incipient faults is very important requiring a valid model and advanced detection technique. In this paper, a new arc discharge model is proposed to simulate arcing phenomena between two discs of a power transformer winding, as one type of important incipient fault, during impulse test. Using wavelet transform techniques, a new methodology is developed. It is shown that winding input current, affected by arcing phenomena and obtained through impulse voltage test, provides important information for detection and analysis of this transient type of minor fault. A number of experiments and simulations were performed to evaluate the validity and accuracy of proposed model and diagnostic technique.

TLM modeling of transformer with internal short circuit faults

Purpose – The purpose of this paper is to describe a technique for modeling transformer internal faults using transmission line modeling (TLM) method. In this technique, a model for simulating a two winding single phase transformer is modified to be suitable for simulating an internal fault in both windings.Design/methodology/approach – TLM technique is mainly used for modeling transformer internal faults. This was first developed in early 1970s for modeling two‐dimensional field problems. Since, then, it has been extended to cover three dimensional problems and circuit simulations. This technique helps to solve integro‐differential equations of the analyzed circuit. TLM simulations of a single phase transformer are compared to a custom built transformer in laboratory environment.Findings – It has been concluded from the real time studies that if an internal fault occurs on the primary or secondary winding, the primary current will increase a bit and secondary current does not change much. However, a very...

Modeling and real-time fault identification in transformers

In this paper, a different internal fault modeling and an identification algorithm are presented. There has been an increasing concern about turn-to-turn faults in transformers because of the high costs of unexpected outages. It is not always possible to analyze the transformer behavior under such faults at rated conditions, since the tests are highly destructive. To develop transformer internal fault detection technique, a transformer model to simulate internal faults is required. This paper describes a novel technique and methodology for modeling and identifying transformer internal faults by using transmission line method (TLM) and fuzzy reasoning technique based on dynamic principal component analysis (PCA), respectively. The transformer has been modeled considering non-linearities as hysteresis and saturation. Transformer internal fault currents are successfully discriminated from the rated currents. The degree and priority of transformer internal faults are obtained by the proposed method. It is suited for implementation on computers because of no computation complexity. Hence, the proposed algorithm can be used effectively in real-time fault identification problems.

A New Method to Identify Inrush Current Based on Error Estimation

This paper presents a novel scheme based on error estimation for identification of magnetizing inrush and internal fault conditions in transformers. Because the inrush current is a peaked wave with a dead angle, we can discriminate internal fault current from inrush current by comparing the similarity between the actual wave and two reference waves under two different frequency conditions per half cycle. Experimental results indicate that this technique is effective under different fault conditions, and an operating time of 10-13 ms can be achieved for internal faults in transformers.

Finite element analysis of internal winding faults in distribution transformers

With the appearance of deregulation, distribution transformer predictive maintenance is becoming more important for utilities to prevent forced outages with the consequential costs. To detect and diagnose a transformer internal fault requires a transformer model to simulate these faults. This paper presents finite element analysis of internal winding faults in a distribution transformer. The transformer with a turn-to-earth fault or a turn-to-turn fault is modeled using coupled electromagnetic and structural finite elements. The terminal behaviors of the transformer are studied by an indirect coupling of the finite element method and circuit simulation. The procedure was realized using a commercially available software. The normal case and various faulty cases were simulated and the terminal behaviors of the transformer were studied and compared with field experimental results. The comparison results validate the finite element model to simulate internal faults in a distribution transformer.

Finite Element Analysis of Internal Winding Faults in Distribution Transformers

With the appearance of deregulation, distribution transformer predictive maintenance is becoming more important for utilities to prevent forced outages with the consequential costs. To detect and diagnose a transformer internal fault requires a transformer model to simulate these faults. This paper presents finite element analysis of internal winding faults in a distribution transformer. The transformer with a turn-to-earth fault or a turn-to-turn fault is modeled using coupled electromagnetic and structural finite elements. The terminal behaviors of the transformer are studied by an indirect coupling of the finite element method and circuit simulation. The procedure was realized using a commercially available software. The normal case and various faulty cases were simulated and the terminal behaviors of the transformer were studied and compared with field experimental results. The comparison results validate the finite element model to simulate internal faults in a distribution transformer.

Digital Filtering Algorithms for the Differential Relaying of Power Transformer: An Overview

This paper reviews the digital differential relaying algorithms proposed by different authors for the protection of power transformer and compares them as to their speed of response, computational burden, and the capability to distinguish among an inrush, over-excitation, and transformer internal fault. The mathematical basis of each algorithm is described. All the algorithms are capable of discriminating an inrush, over-excitation, and transformer internal fault.

A Digital Relaying Algorithm for Detecting Transformer Winding Faults

Electric power utilities use differential relays for detecting faults in power transformers. Conventional designs of these relays use second harmonic, third harmonic or total harmonic current as a restraining quantity. This inhibits the relay operation during magnetizing inrush conditions. Initial designs of digital differential relays also used similar approaches. Most designs used the second harmonic component of the current to block trippings during the magnetizing inrush conditions. As the operating voltages and lengths of transmission lines have increased substantially, currents during internal transformer faults can contain large harmonic components. Therefore, the security of differential relays using harmonic restraint is a matter of concern. However, some recently reported algorithms do not use second harmonic restraint to block trippings during magnetizing inrush conditions. They use winding currents. In most situations, the currents in a delta winding are not readily available. The algorithms based on transformer models need equivalent circuit parameters of the transformer. The relay engineer must determine the equivalent parameters of the transformer before using these algorithms. This paper presents a new digital algorithm for detecting winding faults in single-phase and three-phase transformers. The proposed algorithm does not use harmonic component of current to block trippings during magnetizing inrush conditions. It is applicable to situations where it is and it is not possible to measure winding currents. The algorithm does not require the B-H curve data and takes hysteresis losses of the transformer into account. The algorithm was tested using a variety of operating conditions simulated on a digital computer.

A state-of-the-art review of transformer protection algorithms

A comparative study of algorithms for digital differential protection of power transformers is reported. The mathematical basis for each algorithm is described. The algorithms are compared as to their speed of response, computational burden and capability to distinguish between an inrush and transformer internal fault. >

A practical construction of a protection system for transformer internal faults by Sheath coils attached to transformers with concentric cylindrical windings

Electrical Engineering in JapanVolume 98, Issue 4 p. 81-88 Article A practical construction of a protection system for transformer internal faults by Sheath coils attached to transformers with concentric cylindrical windings Hiroshi Sasaki, Hiroshi Sasaki Hiroshima UniversitySearch for more papers by this authorKazuyoshi Shigemaru, Kazuyoshi Shigemaru Hiroshima UniversitySearch for more papers by this authorTsutomu Sakimoto, Tsutomu Sakimoto Goal Incorporation Ltd.Search for more papers by this authorToshimune Okihara, Toshimune Okihara Hiroshima UniversitySearch for more papers by this author Hiroshi Sasaki, Hiroshi Sasaki Hiroshima UniversitySearch for more papers by this authorKazuyoshi Shigemaru, Kazuyoshi Shigemaru Hiroshima UniversitySearch for more papers by this authorTsutomu Sakimoto, Tsutomu Sakimoto Goal Incorporation Ltd.Search for more papers by this authorToshimune Okihara, Toshimune Okihara Hiroshima UniversitySearch for more papers by this author First published: 1978 https://doi.org/10.1002/eej.4390980411AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Volume98, Issue41978Pages 81-88 RelatedInformation

Automatic switches to protect transformers

AN AUTOMATIC grounding switch in combination with an automatic air-break switch can be used in place of a circuit breaker in the 110-kv supply to a transformer. Since internal faults in transformers do not occur frequently, these high-voltage circuit breakers can be put to better use at terminals of transmission lines where faults are caused by lightning. The substitute for a circuit breaker on the high-voltage side of a transformer must provide for interrupting load, magnetizing, and fault currents. The low-voltage circuit breakers are necessary in all except very small single-bank stations for all three interrupting duties. An air-break switch on the high-voltage side of a transformer should be able to interrupt the magnetizing current or to break parallel in a station having two or three banks of transformers. The remaining duty is to interrupt current flowing from the 110-kv network into a faulted transformer. This can be done indirectly by putting a fault on the 110-kv bus which will operate circuit breakers at distant ends of the 110-kv transmission line. This is a drastic method of avoiding interruption of 110-kv fault current at the station flowing to transformer with an internal fault; but as this kind of fault occurs very seldom, such a general interruption can be endured occasionally. When two or more transmission lines are terminated at such stations, high-voltage circuit breakers are required at terminals of lines only, because the automatic air-break switch can be used to disconnect a faulted transformer after all sources of fault current have been removed.