Partial discharge localization in transformers using monopole and log-spiral UHF sensors (original) (raw)
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Partial discharge localization in transformers using UHF sensors
2011 Electrical Insulation Conference (EIC)., 2011
This paper uses detailed model for computation of sectional winding transfer functions that are necessary for partial discharge (PD) localization in transformer windings. In order to increase the accuracy of PD localization in practical cases, the circuit of PD detection impedance is included in the model. Also to increase the reliability, the use of calibration pulses is included in the localization algorithm. By that, it is possible to optimize model parameters before employing them to find the location of discharges. The accuracy of the method is analyzed by measurements on a special prepared transformer in laboratory.
Partial Discharge Detection and Localization in Power Transformer Windings
Applied Mechanics and Materials, 2014
The activity of partial discharge (PD) is one of the major causes of failure of high voltage transformers. Partial discharge detection is usually used as a preventive technique to avoid large-scale losses in the power system. Suitable and reliable methods to detect and localize PD in equipment winding insulation, such as in a transformer, are still widely researched. Among the methods used are based on the acoustic wave, on the electrical determination of the dominant capacitive region in frequency domain, and on the travelling wave method. After a brief review on current methods, a technique based on the frequency spectra of the measured signals showing the characteristic of the transfer functions is proposed. A Matlab simulation of the proposed technique is then presented. PD signals are injected at various points in a transformer winding to represent PD sources at different location within the winding. The main difficulties encountered in current methods, which is the noise and t...
Partial Discharge Localization for a Transformer Based on Frequency Spectrum Analysis
2003
Partial discharge (PD) is a major source of insulation failure in power transformers. The location of a PD source is of crucial importance in both the maintenance and repair of a transformer. This paper applies the knowledge that the poles of a PD current frequency spectrum do not change, whilst the zeros vary with the position of a PD source within the winding. An algorithm based on this approach has been developed for the localization of PDs. The algorithm adopts the wellknown ladder network to model the transformer winding, then estimates the parameters of this model from the poles of the PD current frequency spectrum. This provides the necessary information to be able to calculate a PD signal from different source locations within the model. Finally, the position of a PD source can then be estimated by a comparison of the measured and calculated PD signals. Simulation and experimentation results are demonstrated in the paper.
In this contribution a system for the detection and evaluation of electrical broadband measured partial discharges (PD) on power transformers is introduced and discussed. The theoretical background for some features of the system like the PD localisation based on the use of sectional winding transfer functions (SWTF), are explained exemplarily, whereas the operation of the system is described for two different transformers. The performed measurements could be carried out on-line due to an enhanced sensor technology, superior signal transmission techniques and improved digital signal processing, which enables a significant reduction of disturbing noise.
2015
The article presents a new approach to the detection of a very weak electromagnetic (EM) signal, which is generated by partial discharge (PD) in a high-voltage, oil-filled power transformer. The new technique is based on the discrimination of signals with origin in outside of the transformer which are detected by external sensing head. Performed measurement process contains several different measurement modes with corresponding arrangement of sensing heads. The time-shifts of the waveforms related to transient process occurrence in the signals are the main input parameters for localization methods. In order to estimate the position of the signal source in the 3D space a minimum of four antennas has to be used, since the time of the PD is unknown. Security of the power transformers is an issue which is closely related to the stability of whole electric power distribution system. High power transformers in nuclear power plant reach power up to hundreds of MVA and any damage or destruc...
Partial Discharge (PD) is one of the most important factors in the gradual destruction of transformer insulation, more importantly if the problem is not resolved can cause complete insulation failure. Physical localization of the fault inside the transformers in terms of saving repair time and cost is important. In this paper, by modeling a high voltage winding of a power transformer as a single-layer disk winding with air core the localization of PD is investigated. In this configuration, winding consists of six disks. Here, by applying impulse voltage as PD signal to the beginning of each disk, the voltages are measured and saved online at the bushing and neutral ends of the winding. By using the curve fitting method, the equations of PD signals at these two ends are extracted, then by computing transfer function in Laplace domain the magnitude of this transfer function are saved as a reference diagram. We have done this for all 6 disks. When PD occurred at winding by measuring vo...
Sensors, 2019
This paper presents an algorithm for the localisation of partial discharge (PD) sourcesin power transformers based on the electromagnetic waves radiated by a PD pulse. The proposedalgorithm is more accurate than existing methods, since it considers the effects of the reflection,refractions and diffractions undergone by the ultra-high frequency (UHF) signal within the equipmenttank. The proposed method uses computational simulations of the electromagnetic waves generatedby PD, and obtains the time delay of the signal between each point in the 3D space and the UHFsensors. The calculated signals can be compared with the signals measured in the field, so thatthe position of the PD source can be located based on the best correlation between the simulatedpropagation delay and the measured data. The equations used in the proposed method are definedas a 3D optimisation problem, so that the binary particle swarm optimisation algorithm can be used.To test and demonstrate the proposed algorith...
A new method for locating partial discharges in transformers
Annual Conference on Electrical Insulation and Dielectric Phenomena
During the manufacture of cast coil transformers voids are occluded in the epoxy if the vacuum impregnation process is not carefully controlled. These voids may become the sites of partial discharges which will cause the transformer to fail. Partial discharge sites in cast coil transformers are often difficult to locate. One approach to locating partial discharges in these transformers is to use information contained in the electromagnetic signals generated by the partial discharges. Transformers are compact units often containing thousands of feet of wire and internally their structure is very complex and irregular. Partial discharge signals observed at the terminals of transformers are extremely distorted because the windings are not arranged in a manner which provides a good propagation path to the measurement point. A new method for determining the axial location of partial discharges in cast coils will be presented. A signal processing algorithm is used to determine the normalized energy as a function of position along the coil. The normalized energy is interpreted in terms of the attenuation of the electromagnetic emissions from the partial discharges along the axis of the transformer. A plot of the attenuation as a function of distance along the length of coil clearly indicates the location of the partial discharges.
International Journal of Smart Electrical Engineering, 2018
Partial Discharge (PD) is the most important source of insulation degradation in power transformers. In order to prevent catastrophic failures in transformers, PDs need to be located as soon as possible so that maintenance measures can be taken in time. Due to the structural complexity of windings, locating the PD source inside a transformer winding is not a simple task. In this paper, the efficacy of the proposed Frequency Response Assurance Criterion (FRAC) correlation technique for finding the location of a PD source in a transformer winding is evaluated and compared with two well-known correlation techniques in this regard, that are Time domain correlation and KullbackLeibler divergence. The responses of the winding to PD pulses, generated by Heidler function, of known pulse duration applied in parallel along the whole sections of the winding are considered as the reference data. In addition, the captured responses of the winding generated by injecting the PD pulses of arbitrary...