Soft ware based technique for the identification of transformer faults in real time

Frequency Response Analysis (FRA) has been growing in popularity in recent times as a tool to detect mechanical deformation within power transformers. To conduct the test, the transformer has to be taken out of service which may cause interruption to the electricity grid. Moreover, because FRA relies on graphical analysis, it calls for an expert person to analyse the results as so far, there is no standard code for FRA interpretation worldwide. In this paper an online technique is introduced to detect the internal faults within a power transformer by considering the voltage-current (V-I) locus diagram as a transformer fingerprint that can be measured every cycle to provide a current state of the transformer. The technique does not call for any special equipment as it uses the existing metering devices attached to any power transformer to monitor the input voltage, output voltage and the input current at the power frequency and hence online monitoring can be realised. Various types of faults have been simulated to assess its impact on the proposed locus. A Matlab code based on digital image processing is developed to calculate any deviation of the V-I locus with respect to the reference one and to identify the type of fault. The proposed technique is easy to implement and automated so that the requirement for expert personnel can be eliminated

High Voltage Power Transformer Dissolved Gas Analysis, Measurement and Interpretation Techniques

Dissolved Gas Analysis (DGA) is widely accepted powerful tool in diagnosing power transformer health condition. Several DGA measurement techniques have been developed since 1950’s, from limited laboratory testing up to site online monitoring. Gas Chromatography (GC), Hydrogen On-line Monitor and Photo-Acoustic Spectroscopy (PAS) are most popular among existing DGA techniques. Basic operating principle, advantages and disadvantages of GC, Hydrogen On-line Monitor and PAS are reviewed and discussed in this paper. Several DGA interpretation techniques such as Key Gas Method, Doernenburg, Rogers, IEC ratio methods and Duval Triangle method are also reviewed in this paper

A Novel Method of Measuring Transformer Oil Interfacial Tension Using UV-Vis Spectroscopy

In this article we propose an alternative method of measuring the IFT of transformer oil, using ultraviolet-to-visible (UV-Vis) the IFT of an oil sample and its spectral response parameters (bandwidth and peak absorbance)

Fuzzy logic approach for power transformer asset management based on dissolved gas-in-oil analysis

Dissolved gas analysis (DGA) of transformer oil is one of the most effective power transformer condition monitoring tools which can be facilitated to determine transformer criticality ranking and hence identifying a suitable condition-based asset management decision. There are many interpretation techniques for DGA results however all current techniques rely on personnel experience more than analytical formulation. As a result, the current techniques do not necessarily lead to the same conclusion for the same oil sample. A significant number of DGA results fall outside the proposed codes of the current based-ratio methods and cannot be diagnosed by these methods. Moreover, ratio methods fail to diagnose multiple fault conditions due to the mixing up of produced gases. To overcome these limitations, this paper introduces a fuzzy logic approach to aid in standardizing DGA interpretation techniques, identify transformer critical ranking and provide a suitable asset management decision based on DGA analysis. The approach relies on integrating all existing DGA interpretation techniques into one expert prototype model. DGA results of 338 oil samples of pre-known fault condition that are collected from different transformers of different rating and different life span are used to establish the model which is developed based on the consistency of various traditional DGA interpretation techniques that are currently used by various utilities and chemical laboratories worldwide

High frequency transformer computer modeling

Frequency response analysis (FRA) technique is nowadays widely used in both factory and field applications as a diagnostic tool for power transformers. The main problem about FRA techniques is to interpret the observed evolution of the frequency response in order to identify failures. Transformer high frequency computer modeling is proposed in this work to be used with the FRA. The physical meaning of the model parameters allows the identification of the problem inside the transformer. The paper presents the model and experimental results and analysis of the frequency responses on the variations of the winding parameters. Effect of core, bushings, oil and tank on FRA is also investigated

Superconducting magnetic energy storage unit, an efficient energy technology for power systems

This paper discusses application of superconducting magnetic energy storage (SMES) unit to improve power system performance. The application of SMES unit in mitigating voltage sags and in damping dynamic oscillations in power systems is discussed. To show the effectiveness of the proposed controller in providing continuous voltage regulation and in enhancing power system dynamics, a three-phase short circuit is applied to the system and simulation is carried out with and with no SMES connected to the system. The results of these investigations are studied using the well-developed graphic facilities available in an industry standard power system package, namely PSCAD/EMTDC. Results have shown that SMES unit can effectively improve system stability and power quality of power systems

Application of UPFC to improve the low-voltage-ride-through capability of DFIG

In this paper, a new controller approach for unified power flow controller (UPFC) is proposed to improve the low-voltage-ride-through (LVRT) capability of a DFIG-based WECS during voltage sag. The shunt and series converters of the UPFC are controlled using a hysteresis current controller (HCC) and proportional integral controllers (PI), respectively. Detailed simulation is carried out using MATLAB/SIMULINK software to highlight the impact of UPFC in improving the overall system performance during grid fault

Impact of Power Transformer Insulating Mineral Oil Degradation on FRA Polar Plot

Frequency response analysis (FRA) has been employed as an effective tool for the detection of various mechanical winding and core deformations within electrical power transformer. Traditional FRA signature interpretation relies on the magnitude of the FRA plot although all practical frequency response analyzers are able to provide both magnitude and angle of the FRA signal in wide frequency range. Moreover, no attention has been given to the impact of power transformer insulating oil degradation on the FRA signature. This paper presents is aimed at introducing a new interpretation approach of the FRA signature using polar plot which is obtained by incorporating FRA signature magnitude and phase into one plot. The paper also investigates the impact of insulating mineral oil degradation on the proposed polar plot signature. Digital image processing (DIP) technique is developed to automate the interpretation process. In this regard, the physical geometrical dimension of a single-phase transformer filled with insulating mineral oil is simulated using three-dimensional finite element analysis to emulate real transformer operation. FRA polar plot signatures are measured and analyzed for various health conditions of the mineral oil. Results show that insulating mineral oil degradation has an impact on the transformer FRA polar plot signature. The proposed FRA polar plot technique is easy to implement within any frequency response analyzer

Image processing-based on-line technique to detect power transformer winding faults

Frequency Response Analysis (FRA) has been growing in popularity in recent times as a tool to detect mechanical deformation within power transformers. To conduct the test, the transformer has to be taken out of service which may cause interruption to the electricity grid. Moreover, because FRA relies on graphical analysis, it calls for an expert person to analyse the results as so far, there is no standard code for FRA interpretation worldwide. In this paper an online technique is introduced to detect the internal faults within a power transformer by constructing the voltage-current (V-I) locus diagram to provide a current state of the transformer health condition. The technique does not call for any special equipment as it uses the existing metering devices attached to any power transformer to monitor the input voltage, output voltage and the input current at the power frequency and hence online monitoring can be realised. Various types of faults have been simulated to assess its impact on the proposed locus. A Matlab code based on digital image processing is developed to calculate any deviation of the V-I locus with respect to the reference one and to identify the type of fault