A novel wavelet approach to busbar protection during CT saturation and ratio-mismatch
TL;DR: In this paper, the use of a continuous wavelet transform (CWT) was used to distinguish faults in a busbar protection zone from those outside the zone. And the proposed wavelet transformation approach based on the Morlet wavelet basis function was found to be an excellent discriminant for identifying the fault signals during the CT saturation and ratio mismatch.
Abstract: This paper deals with the use of a continuous wavelet transform (CWT) to distinguish faults in a busbar protection zone from those outside the zone. The Morlet wavelets are used as the wavelet basis function. They are more efficient in monitoring fault signals as time varies. The differential current as the operating quantity and the sum of the current magnitudes as the stabilizing signal are computed. The magnitudes of the CWT of these currents are derived to obtain the operational and restraint signals. The CWT coefficient plots are given to precisely determine the scale of analysis. The proposed wavelet transform approach based on Morlet basis function is found to be an excellent discriminant for identifying the fault signals during the CT saturation and ratio mismatch. ATP simulations are used to test and validate the proposed CWT approach for model power system faults.
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TL;DR: This study improves the busbar differential protection scheme by the addition of a new feature extracted from differential current using S-transform analysis, and justifies the superiority of the proposed method in terms of speed and security even in noisy conditions.
Abstract: Differential protection is the main protective scheme of busbar in power systems but its operation degrades during current transformer (CT) saturation conditions. In this study, the busbar differential protection scheme is improved by the addition of a new feature extracted from differential current using S-transform analysis. S-transform as a powerful signal processing technique gives a complete visualisation of the signal in both time and frequency domains. The new extracted feature as well as the magnitude of the differential and restraint currents are utilised to increase the security of traditional busbar differential protection scheme. With the addition of this new feature, distinctive regions are created in the feature space which can be separated by an appropriate classifier. In this study, the well-known classifier, i.e. support vector machine is employed to effectively discriminate internal faults from external faults. To evaluate the performance of the proposed method, a part of Iranian 400-kV power system grid is simulated in the PSCAD/EMTDC environment. The transient behaviour of CTs during saturation conditions is simulated based on the precise Jiles–Atherton model. The obtained results justify the superiority of the proposed method in terms of speed and security even in noisy conditions.
37 citations
TL;DR: In this paper, a new support vector machine (SVM)-based fault zone identification scheme for busbar which correctly identifies faults occurring inside and outside the protection zone of busbar is presented.
Abstract: This study presents a new support vector machine (SVM)-based fault zone identification scheme for busbar which correctly identifies faults occurring inside and outside the protection zone of busbar. The proposed scheme utilises one cycle post-fault current signals of all the lines as an input to SVM. In order to achieve the most optimised classifier, Gaussian radial basis function has been used for training of SVM. Feasibility of the proposed scheme has been tested by modelling an existing 400 kV Indian busbar system in PSCAD/EMTDC software package. More than 28 800 fault cases with varying fault resistances, fault inception angles, fault locations, types of faults and source impedances have been generated and used for validation of the proposed scheme. The proposed scheme effectively discriminates between in-zone and out-of-zone faults with very high fault classification accuracy for different fault and system conditions. Moreover, the proposed scheme remains stable during an early and severe current transformer (CT) saturation condition giving an accuracy of 99 for all the fault cases.
30 citations
TL;DR: The obtained results reveal the proposed 87BW function provides ultra-high-fast trip for internal and evolving external-to-internal faults, guaranteeing security for normal through-load and external faults as well, even in the case of early and severe current transformer (CT) saturation.
Abstract: This paper presents a new wavelet-based busbar differential protection algorithm, named as 87BW function. The instantaneous current-based differential protection fundamentals are taken into account and the well-known 1-out-of-1 and 2-out-of-2 tripping logics are mapped into the wavelet domain. Operating and restraint wavelet coefficients energy of currents are computed, regarding station configuration and bus zones boundaries. Thereby, the proposed 87BW function can be properly used in both static and dynamic busbar configuration. Its performance was evaluated through EMTP-based simulations of faults in a 230 kV power substation with double bus single breaker configuration. The obtained results reveal it provides ultra-high-fast trip for internal and evolving external-to-internal faults, guaranteeing security for normal through-load and external faults as well, even in the case of early and severe current transformer saturation.
26 citations
Cites background or methods from "A novel wavelet approach to busbar ..."
...In respect to busbar, some algorithms based on wavelet transform have been reported as alternatives to reduce the protection scheme operating time [12]–[18]....
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...Undoubtedly, the wavelet-based busbar protection algorithms reported in [12]–[18] could provide very fast operating time for most internal faults and prevent false trip for external ones, even if CT saturation takes place....
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...In [12], a busbar differential protection scheme based on the Morlet wavelet is introduced, showing good performance during saturation and ratio mismatch of CTs....
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TL;DR: In this paper, the fault indexes of differential current and that of a source CT current are obtained over narrow moving windows based on their respective detail coefficients and compared with their respective threshold values to detect the internal faults.
Abstract: This paper deals with application of Wavelet Transform for detection of busbar faults and to discriminate them from external faults. The fault indexes of differential current and that of a source CT current are obtained over narrow moving windows based on their respective detail coefficients. The fault indexes of both current signals obtained are compared with their respective threshold values to detect the internal faults. The time shift of differential current detail coefficients compared to those of source current due to saturation of CT is used to discriminate the external faults from internal faults. The scheme is tested successfully for different types of external and internal faults.
26 citations
TL;DR: The proposed algorithm is twice or more faster than the traditional instantaneous-current-based algorithm for most of the internal and evolving external-to-internal faults, while ensuring secure operation for external ones even when severe current transformer (CT) saturation takes place, through a new harmonic power restraint strategy.
Abstract: This paper presents a new method for busbar differential protection based on the instantaneous power concept. In order to do so, the instantaneous power per phase of each network element connected to the busbar is computed by using the instantaneous current values and a voltage memory action strategy. The performance of the proposed technique is compared to one of the traditional instantaneous-current-based differential protection algorithms, which is widely used by manufacturers of commercial relays. Both internal and external faults, as well as evolving external-to-internal faults, were simulated in a power substation with double-bus single-breaker configuration using the software ATPDraw. The obtained results reveal that the proposed algorithm is twice or more faster than the traditional instantaneous-current-based algorithm for most of the internal and evolving external-to-internal faults, while ensuring secure operation for external ones even when severe current transformer (CT) saturation takes place, through a new harmonic power restraint strategy. Also, since the proposed method provides faster fault detection time, the requirements for CT time to saturate may be alleviated, guaranteeing correct operation even in the case of early CT saturation.
19 citations
Cites methods from "A novel wavelet approach to busbar ..."
...Moreover, in [13]–[17], different wavelet-based schemes were used to analyze high frequencies transient components generated by faults....
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References
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Book•
10 Aug 1992
TL;DR: In this paper, the authors present a classic power system relaying and power system phenomena including stability protection, reliability, and reliability of the relaying system from a network operator's perspective.
Abstract: ??????????? ????? Stanley Horowitz H Power System Relaying May 13th, 2020 With emphasis on power system protection from the network operator perspective this classic textbook explains the fundamentals of relaying and power system phenomena including stability protection and reliability The fourth edition brings coverage up to date with important advancements in protective relaying due to significant changes in the conventional electric power system that will
696 citations
TL;DR: The wavelet transform of a signal consists in measuring the "similarity" between the signal and a set of translated and scaled versions of a "mother wavelet" as discussed by the authors.
Abstract: This paper introduces wavelets and shows that they may be efficient and useful for power distribution relaying. The wavelet transform of a signal consists in measuring the "similarity"between the signal and a set of translated and scaled versions of a "mother wavelet". The "mother wavelet" is a chosen fast decaying oscillation function. Wavelets are used to analyse transient earth faults in a 20 kV resonant grounded network as generated by EMTP. It is shown that wavelets may be employed for analysing records to study efficiently the faulted network. Moreover, this new technique can actually be implemented in real time for protection devices. Thus, it is suitable for application to protective relays.
273 citations
TL;DR: In this article, an application of Morlet wavelets to the analysis of high-impedance fault generated signals is proposed in which the time and frequency information of a waveform can be presented as a visualized scheme.
Abstract: An application of Morlet wavelets to the analysis of high-impedance fault generated signals is proposed in this paper. With the time-frequency localization characteristics embedded in wavelets, the time and frequency information of a waveform can be presented as a visualized scheme. Different from the fast Fourier transform, the wavelet transform approach is more efficient in monitoring fault signals as time varies. The proposed method has been applied to discriminate the high-impedance faults from the normal switching events, and to examine the faults under various grounds including Portland cement, wet soil and grass. Testing results have demonstrated the practicality and advantages of the proposed method for the applications.
148 citations
TL;DR: In this article, the authors describe a digital technique for protecting busbars by using positive and negative-sequence models of the power system in a fault-detection algorithm, while phase voltages and currents are used to detect faults.
Abstract: This paper describes a digital technique for protecting busbars. The technique uses positive- and negative-sequence models of the power system in a fault-detection algorithm. While phase voltages and currents are used to detect faults, parameters of the power system are not used. An analysis of the performance of the proposed technique during CT saturation and ratio-mismatch conditions is presented. The performance of the technique was investigated for a variety of operating conditions and for several busbar configurations. Data generated by EMTP simulations of model power systems were used in the investigations. The results indicate that the proposed technique is stable during CT saturation and ratio-mismatch conditions.
63 citations
TL;DR: In this paper, a novel technique for current differential pilot relay protection (CDPR) by using wavelet analysis is described, where power system CAD is used to generate current signals at both ends of a transmission line in a typical system with fault at various locations.
Abstract: This paper describes a novel technique for current differential pilot relay protection (CDPR) by using wavelet analysis. Power system CAD (PSCAD) is used to generate current signals at both ends of a transmission line in a typical system with fault at various locations. In this paper, discriminating between internal fault and external fault/change, identifying of faulted phase, and classifying fault type are achieved by using wavelet analysis. The simulation results show that this approach provides a high operating sensitivity for internal fault and remains stable for external fault/change.
39 citations