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This paper provides a comprehensive review of the acoustic method used for partial discharge (PD) localization in power transformer. The paper outlines the partial discharge mechanism, basic principle and properties of the acoustic emission (AE), advantages and limitations of the acoustic method compared to the electrical method, and different AE based PD localization techniques along with their algorithms used in power transformer. Most of the algorithms proposed in the literature for PD localization in power transformer are based on the time difference of arrival (TDOA) of AE signals. Thus, this paper would help researchers, academicians, and engineering communities working in the area of AE based PD localization in power transformer to avoid insulation damage. [ABSTRACT FROM AUTHOR]

This paper presents a new differential protection scheme for busbar using d–q–0 transformation. The proposed method is based on derivation of operating and restraining currents by utilizing direct axis (d) component of current transformer (CT) secondary current signals of all bays. The dual slope relay characteristic (derived from the operating and restraining current) of the proposed scheme operates in conjunction with a CT saturation detection algorithm and hence, provides better stability during external faults with CT saturation. The performance of the proposed scheme has been evaluated by modeling a 400 kV sub-station with two different busbar configurations, namely Breaker-and-Half configuration (BHC) and single breaker double-bus configuration (SBDBC) in PSCAD/EMTDC software package. The proposed algorithm has been tested for various fault cases with diversified system and fault parameters. The proposed scheme is highly sensitive against in-zone faults even with a considerable value of fault resistance as the average fault detection time remains within one-and-half cycle. At the end, a comparative evaluation of the proposed scheme with the conventional bus differential protection scheme (87B) clearly indicates its superiority in terms of stability against close-in out-of-zone faults with CT saturation and sensitivity for high impedance internal faults. [ABSTRACT FROM AUTHOR]

Due to dependency on Plug Setting (PS), Time Dial Setting (TDS), size of the network, more than one back-up relays for one primary relay and other technical constraints, coordination of Directional Overcurrent Relays (DOCRs) is an extremely constrained and nonlinear optimization problem. In this paper, a new Gravitational Search (GS) based algorithm is presented for achieving optimal coordination of directional overcurrent relays. The proposed algorithm utilizes user defined characteristic for inverse time overcurrent relays than the predefined standard curves. The user defined relay characteristic deals with constants that control the shape of the characteristics as variable adjustable values which are optimally chosen along with TDS and Plug Setting Multiplier (PSM). The performance of the proposed algorithm has been evaluated on 8-bus, 15-bus and IEEE 30-bus distribution network at different fault locations (near-end, far-end and middle point). In addition, the time of operation of some of the primary relays at different fault locations on IEEE 30-bus distribution network is also presented. At the end, comparative evaluation of the proposed algorithm with other optimization algorithms having different relay characteristics presented in the literature clearly indicates its effectiveness and superiority in terms of the sum of total primary relays operating time. [ABSTRACT FROM AUTHOR]

This paper presents a random forest (RF) classifier-based digital protection scheme which provides an effective discrimination between internal and external faults on a busbar. The measured current signals of all the bays (lines) connected to a busbar have been used as feature vectors. The system and fault parameters have been varied to generate a wide variety of simulation cases (33,600) consisting of both internal and external faults. By giving post-fault data of one cycle duration of all the bay currents as an input to the RF classifier, and taking only 30% of the total data (33,600) for training and remaining 70% of the total data for testing, an accuracy higher than 98% has been obtained. The PSCAD/EMTDC software package is used to model a prevailing 400-kV Indian busbar system for the purpose of authentication of the presented technique. The presented technique successfully differentiates between internal faults and external faults and remains unaffected against the change in system and fault parameters. In addition, the proposed scheme maintains stability under the Current Transformer saturation phenomena particularly during a heavy-through fault. A comparative analysis of the proposed scheme with the recently proposed scheme using support vector machine classifier clearly shows its superiority. [ABSTRACT FROM PUBLISHER]

This article deals with the condition monitoring and fault diagnosis of a three-phase induction motor using a support vector machine classifier. By acquiring the three line voltages and currents of the motor in real time (experimentally on a 3-HP motor in the laboratory environment), total harmonic distortion is calculated, which in turn is used for the training of the support vector machine. A laboratory prototype has been developed through which various data have been generated by conducting extensive experiments on a healthy motor as well on a motor having faulty bearing, shorting of stator turns, and broken rotor bars with varying load conditions. The performance of the projected support vector machine-based scheme has been assessed for two kernel functions on the basis of fault classification accuracy. It can be noted that the accuracy of the radial basis function kernel is higher than that of the polynomial kernel. The proposed support vector machine-based scheme gives satisfactorily results, as the fault discrimination accuracy is found to be more than 98%. Simultaneously, it also gives an accuracy of the order of 95% for different motor design specifications, which confirms robustness of the proposed scheme. [ABSTRACT FROM AUTHOR]

This article presents relevance vector machine (RVM) based relaying scheme for busbar protection which correctly differentiates between internal faults on busbar and external faults. To validate the proposed scheme, numerous computer simulations have been carried out on an existing 220 kV Indian power generating station having different types of bays such as line, transformer, reactor & generator with generator transformer (GT). Various fault conditions (test data set of 23,760) have been simulating using the power system computer aided design (PSCAD)/ electromagnetic transient direct current (EMTDC) software package (Winnipeg, MB, Canada) by varying fault & system parameters. The proposed RVM based fault discrimination scheme is executed in MATLAB software (The Math- Works, Natick, Massachusetts, USA) by loading the simulation data. Comparative evaluation of the proposed RVM based scheme with the existing support vector machine (SVM) based scheme clearly indicates the superiority of the proposed scheme in terms of decision speed (faster than SVM based scheme) and classification accuracy (more than 99%). Moreover, it does not operate under different types of external faults and system disturbances. Subsequently, the proposed scheme remains stable during severe current transformer (CT) saturation condition. [ABSTRACT FROM PUBLISHER]

In this article, a new islanding detection technique based ondq0 transformation is presented for the power system network containing distributed generators. The proposed technique is based on the peak value of current (Is) that is obtained bydq0 transformation of current signals. Simulations of various islanding conditions have been carried out using PSCAD/EMTDC software package (Manitoba HVDC Research Centre, Winnipeg, MB, Canada) at different values of active and reactive power mismatches. Moreover, various non-islanding events have also been taken into account. The simulation results clearly point out that the proposed scheme completely eliminates the non-detection zone and rapidly detects islanding. At the same time, it also avoids nuisance tripping during various non-islanding events as well as for the system with multiple distributed generators. Comparative evaluation of the proposed scheme is also carried out with the existing scheme, and it has been observed that the proposed scheme remains stable during a non-islanding situation in which the existing scheme fails. [ABSTRACT FROM PUBLISHER]

Abstract—Integration of distributed generation with utility network demands satisfactory operation of an islanding detection scheme, as it can otherwise lead to such problems such enhancement in non-detection zone, out-of-phase reclosing, personnel safety, and degradation of power quality. This article presents a new islanding detection scheme based on the rate of change of impedance (dz/dt) of each phase. To calculatedz/dt, phasor computation is carried out using a half-cycle modified discrete Fourier transform algorithm. Test data are generated using the PSCAD/EMTDC software package (HVDC Research Center, Inc., Manitoba). Various islanding conditions have been simulated by disconnecting the main circuit breaker with different values of active and reactive power mismatch. At the same time, different non-islanding conditions have also been simulated through switching (ON/OFF) of load, energization/de-energization of medium transmission lines, short-circuit on an adjacent feeder, and switching (ON/OFF) of the transformer and capacitor bank in the network. The simulation results indicate that the proposed scheme is capable of providing effective discrimination between islanding and non-islanding conditions. The proposed scheme is able to detect islanding conditions within a half-cycle from event inception. [ABSTRACT FROM PUBLISHER]