M.K. Ilampoornan

Bio: M.K. Ilampoornan is an academic researcher from Loyola University Chicago. The author has contributed to research in topics: Power factor & Distribution transformer. The author has an hindex of 2, co-authored 10 publications receiving 13 citations. Previous affiliations of M.K. Ilampoornan include Anna University & Indian Institute of Technology Madras.

Instrument transformer winding fault analysis using frequency response analysis

Abstract: Improvement of diagnostic methods for both power and Instrument transformer is crucial considering the part they play in electrical networks as well as their cost. Frequency response analysis based testing of transformers is one of the methods that have been introduced recently. This method enables the identification of winding deformations resulting from the short circuit currents and winding dislocations occurring during transportation, and can also be used to assess the state of electrical insulation. The damage may cause a change in the physical condition of transformer which would be reflected in the electrical parameters- resistance, inductance and capacitance. The insulation performance is influenced by thermal, electrical and mechanical stresses. The displacement of windings can occur during transportation of transformers or during a short circuit near the transformer in the power system. The Frequency Response Analysis (FRA) can detect the type of fault and the exact location of fault. FRA essentially consists of measuring the impedance of transformer windings over a wide range of frequencies and comparing the results with a reference set. There are two ways of injecting the wide range of frequencies necessary, either by injecting an impulse into the winding or by making a frequency sweep using a sinusoidal signal. The former method is known as the impulse response method and the latter is known as the swept frequency method. The result obtained for the various fault condition is compared with the reference set and the conclusions are drawn.

Sensitive method for detection of winding deformation during short circuit test

Abstract: The mechanical strength and integrity of the transformer windings is established by short circuit test. Reactance comparison method and frequency response analysis methods are conventionally used to assess the failures. Concurrent application of various high frequency excitations has also been tested. We show that optimized multisine excitation has the potential of high sensitivity towards displacement identification.

Compensation of Negative Sequence Component using sequence parameters

Abstract: Current unbalance is frequently encountered power quality problem. Negative sequence current leads to increase in machine temperature and unnecessary tripping of circuit breakers. Unequal phase current and harmonic current causes increased line losses and skin effect. In this paper, a new stationary reference frame control is proposed and implemented based on Positive and Negative Sequence Component Extraction. Positive sequence current is taken as reference for VSI, used as current unbalance compensator. VSI is designed to eliminate negative sequence current component thereby balance of currents are obtained. Consequently, reduction in lines losses and improvement of power factor is also observed in the power system.

On the Mechanical Short-Time Rating of a Current Transformer

Abstract: Closed-form expressions and a finite-element method are used to compute the maximum force in the primary conductor of a wound current transformer (CT). It is shown that for a given volume for the primary winding, one configuration exists that leads to a maximum force. It is proved that the mechanical short-time rating of two CTs having different turns but identical ampere turns is not equivalent. Designers can now establish and test a CT with a worst-case configuration.

Voltage SAG/SWELL mitigation using AC chopper

Abstract: A new topology is proposed here to compensate voltage sags in power systems. One of the major power quality issues encountered by industries is the voltage sag. To compensate sag, a new topology is designed without storage device. This sag adjuster is capable of compensating deep and long duration voltage sag. The sag adjuster of each phase derives power from other two phases. The sag occurring in single-phase is compensated by sag adjuster; it is realized with two ac chopper circuits. By controlling the firing angle of each ac chopper, the required voltage is obtained to compensate for the voltage sag. Simulation of proposed topology is done. The results are comply with IEC standard.

Analytical estimation of short circuit axial and radial forces on power transformers windings

Abstract: In this study, an analytical method is proposed to calculate exerted axial and radial forces on the high and low voltage (LV) windings in core type power transformers. Hence, an analytical modelling approach is proposed to compute short circuit currents in the transient mode and steady state. The proposed model includes non-linear characteristics of the core materials, eddy currents effects, symmetrical and asymmetrical hysteresis loops of the used laminates. Then, exerted axial and radial forces on the high and LV windings are analytically computed in the transient mode and steady state. In order to certify obtained analytical results, the two-dimensional (2D) time stepping finite element method (TSFEM) is utilised to determine aforementioned forces. In this modelling approach, the geometrical, electrical and magnetic characteristics of the core type transformer under short circuit fault are taken into account. Furthermore, three-dimensional TSFEM is employed to verify the analytical and 2D TSFEMs results.

A Smart Frequency Domain-Based Modeling Procedure of Rogowski Coil for Power Systems Applications

Abstract: Rogowski coils are key measurement instruments in several applications due to their flexibility, large bandwidth, linearity, and so on. Like the majority of the instrument transformers (ITs), Rogowski coils are standardized and their use is regulated almost for every application. This article focuses on a smart way for the equivalent parameters’ computation of the Rogowski coil. The parameter computation is performed by evaluating the Rogowski response when subjected to a single waveform generated to fulfill a specific requirement on its frequency content. Results demonstrate the equivalency of the presented method compared to the typical frequency sweep test. In addition, the results have been used to validate Rogowski’s output estimate procedure presented by the authors in a previous work.

Online assessment of winding deformation based on optimised excitation

Abstract: On line assessment of winding deformation in a power transformer can be performed via a bushing tap excitation with optimized high frequency excitation. A benchmark layer winding is used to validate the use of the specific high frequency excitation. Axial displacement, compression and buckling of the winding are simulated and the changes identified. Measurements are performed on a voltage transformer to verify the suitability of the technique. The procedure will result in a considerably shorter time for measurement.

A Novel Power Transformer Fault Diagnosis Model Based on Harris-Hawks-Optimization Algorithm Optimized Kernel Extreme Learning Machine

Abstract: Abstract Dissolved gas analysis (DGA) method is widely used to detect the incipient fault of power transformers. This paper presents a novel DGA method for power transformer fault diagnosis based on Harris-Hawks-optimization (HHO) algorithm optimized kernel extreme learning machine (KELM). The non-code ratios of the gases are used as the characterizing vector for the KELM model, and the Harris-Hawks-optimization (HHO) algorithm is introduced to optimize the KELM parameters, which promotes the fault diagnostic performance of KELM. Based on dataset collected from IEC TC 10, the fault diagnosis capability of the proposed method is validated by different characterizing vectors and is compared with conventional KELM and other optimized KELM. Moreover, the generalization ability of the proposed method is confirmed by China DGA data. The results demonstrate that the proposed method is superior to other methods and is more effective and stable for power transformer fault diagnosis with high accuracy.