Transformation Of Units Research Articles

The Use of Generalized Gaussian Distribution in Vibroacoustic Detection of Power Transformer Core Damage

Vibroacoustic diagnostics (VM—Vibroacoustic Method) is one of the methods for diagnosing the active part of power transformers. Measurement technologies have been refined over the past several years, but the methods of analyzing data obtained in VM diagnostics are still in development. In most cases, they are based on a simple frequency spectrum analysis, and the diagnostic conclusions are subjective and depend on the expert’s professional experience. The article presents an objective method for the detection of transformer unit core damage, based on the analysis of the statistical properties of the vibration signal registered on the surface of the tank of an unloaded transformer in the steady state of vibrations (VM). The algorithm for proceeding further is: FFT analysis of the vibroacoustic signal, with the determination of the relative changes in vibration power as a function of frequency P r ( f ) and, finally, the determination of the statistic properties of the dataset P r ( f ) . The Generalized Gaussian Distribution (GGD) is used to describe the P r ( f ) set. The detector output values are the λ and p parameters of the GGD distribution. These two numerical values form the basis for the classification of the technical condition of the transformer unit core. The correctness of the described solution was verified on the example of ten pieces of 16 MVA power transformers with different operating times and degrees of wear.

An optimized FPGA design of inverse quantization and transform for HEVC decoding blocks and validation in an SW/HW environment

This paper presents an optimized hardware architecture of the inverse quantization and the inverse transform (IQ/IT) for a high-efficiency video coding (HEVC) decoder. Our highly parallel and pipelined architecture was designed to support all HEVC Transform Unit (TU) sizes: 4 × 4, 8 × 8, 16 × 16, and 32 × 32. The IQ/IT was described in the VHSIC hardware description language and synthesized to Xilinx XC7Z020 field-programmable gate array (FPGA) and to TSMC 180 nm standard-cell library. The throughput of the hardware architecture reached in the worst case a processing rate of up to 1080 p at 33 fps at 146 MHz and 1080 p at 25 fps at 110 MHz when mapped to FPGA and standardcells, respectively. The validation of our architecture was conducted on the ZC702 platform using a Software/Hardware (SW/HW) enviro nment in order to evaluate different implementation methods (SW and SW/HW) in terms of power consumption and run-time. The experimental results demonstrate that the SW/HW accelerations were enhanced by more than 70% in terms of the run-time speed relative to the SW solution. Besides, the power consumption of the SW/HW designs was reduced by nearly 60% compared with the SW case.

High-fidelity hardware-in-loop simulation of tethered-wings based on discrete-time mechanics

This paper presents a hardware-in-loop simulator for ground-based tethered-wing systems based on a discrete-time Lie group variational integrator. The integrator expresses the highly detailed dynamics of the system of reeling mechanism, tether, and wing. A physical generator is coupled to the integrator based on co-simulation methods. This approach yields a high-fidelity simulation environment that allows for the accurate assessment of the power transformation unit’s performance and its embedded controllers. The stability and accuracy of the simulator are analyzed in the presence of time-delays caused by hardware-software interfacing and after applying a scale factor to the hardware. On-line measures for monitoring the accuracy of the coupling are presented and employed in laboratory experiments with the HIL simulator.

Discrimination of Internal Faults and Other Transients in an Interconnected System With Power Transformers and Phase Angle Regulators

This study solves the problem of accurate detection of internal faults and classification of transients in a 5-bus interconnected system for Phase Angle Regulators (PAR) and Power Transformers. The analysis prevents mal-operation of differential relays in case of transients other than faults which include magnetizing inrush, sympathetic inrush, external faults with CT saturation, capacitor switching, non-linear load switching, and ferroresonance. A gradient boosting classifier (GBC) is used to distinguish the internal faults from the transient disturbances based on 1.5 cycles of 3-phase differential currents registered by a change detector. After the detection of an internal fault, GBCs are used to locate the faulty unit (Power Transformer, PAR series, or exciting unit) and identify the type of fault. In case a transient disturbance is detected, another GBC classifies them into the six transient disturbances. Five most relevant frequency and time domain features obtained using Information Gain are used to train and test the classifiers. The proposed algorithm distinguishes the internal faults from the other transients with a balanced accuracy of 99.95%. The faulty transformer unit is located with a balanced accuracy of 99.5% and the different transient disturbances are identified with a balanced accuracy of 99.3%. Moreover, the reliability of the scheme is verified for different rating and connection of the transformers involved, CT saturation, and noise levels in the signals. These GBC classifiers can work together with a conventional differential relay and offer a supervisory control over its operation. PSCAD/EMTDC software is used for simulation of the transients and to develop the two and three-winding transformer models for creating the internal faults including inter-turn and inter-winding faults.

Algorithm for Probability Calculation of B- Spline Curve

This paper presents a probability calculation method for B-spline curve, which is made up of coordinate transformation unit, normalization unit, binarization unit, probability calculation unit, data decoding unit. This thesis offers the general structure and algorithm principle of generating B-spline curve, and draws the B-spline curve on the simulation hardware of VC++6.0 software. Experimental results show that compared with the traditional method of directly calculating B-spline, Paper’s method has lower algorithm complexity and faster curve generation, which is more beneficial to the realization of high-order B-spline curve.

Interpretation of sweep frequency response analysis traces on inter-turn short circuit fault

Sweep frequency response analysis (SFRA) is a reliable method for detection and diagnosis of faults in the active part of transformers. However, although SFRA is widely employed, the interpretation of SFRA signature is still a challenge and require experts to analyse them. This is due to lack of guideline and standard for SFRA signature interpretation and clarification. This paper presents the interpretation of SFRA signature by classification and quantification on inter-turn short circuit fault on the transformer winding. The short-circuited turns fault on HV winding phase “A” was practically simulated on three different units of three-phase transformers. The results of simulated fault are presented and discussed. A conclusion was drawn which provides the interpretation of the SFRA response due to inter-turn short circuit fault case by using a statistical indicator which is NCEPRI algorithm.

Enhancing the security of AES through small scale confusion operations for data communication

With the advent of computers, networks, distributed systems and wireless data transfer technologies, data communication is subjected to potential threats and hence needs to be protected. Advanced Encryption Standard (AES) is an efficient encryption algorithm used for secure wireless communication, but its security is under threat due to different forms of theoretical and practical attacks such as linear cryptanalysis, differential cryptanalysis, boomerang attack, truncated differentials, hybrid attacks, related-key distinguishing attack, and side channel attacks. This work is focused on reducing the attacks by increasing the complexity of cryptanalysis through small scale variations in the shift row transformation and key expansion unit of the AES algorithm. The proposed small scale variations in the linear layer of the cipher unit and in the word column of key expansion unit enhances confusion during encryption. The inherent diffusion property of the algorithm along with the proposed confusion characteristics allows us to increase the overall security of the algorithm. The confusion and diffusion characteristics of the modified algorithm are found to be higher in terms of balance, Strict Avalanche Criterion and bit independence criteria. The AES variants are also tested using NIST-800-22 statistical test suite for random number generators, the small scale variations made in the architecture provides a higher degree of randomness in the ciphertext thus increasing cryptanalysis complexity. This paper also proposes an obfuscation control unit that allows on-demand selection of the three AES variants resulting in a variable encrypting pattern for a plaintext-key pair thus adding more bottlenecks to the adversaries.

Determination of Spectral Characteristics in a Vibration Sensor Microcircuit

This article discusses aspects of the implementation of digital signal processing algorithms in devices with multifunctional diagnostics of bearing assemblies in integrated-circuit form. The possibility of applying the effective implementation of spectral analysis algorithms on a defined basis is considered. The structural flow chart of the filter which performs Goertzel transformation and schemes for implementation of the fast Fourier transform unit is shown. To solve these problems in Matlab environment were developed mathematical models of Goertzel filter of fast Fourier transform unit was simulated operation of these units for specifying of parameters and evaluation of achieved characteristics. After the evaluation of simulation results, 2 types of spectral analysis units were developed: Goertzel transformation units for accurate calculations and fast Fourier transform units for analysis during the whole operating band. The created units of spectral analysis make it possible to efficiently solve the problems of bearing diagnostics, obtain information on the video spectrum of the vibration signal in the full frequency band and at the same time to determine the exact value or vibration levels at the characteristic frequencies.

Hierarchical Classification for Complexity Reduction in HEVC Inter Coding

In order to adapt to various real-time applications, fast coding algorithms for high efficiency video coding (HEVC) standard maintain a hot research topic in recent years. In this paper, a complexity reduction algorithm based on hierarchical classification for HEVC inter coding is proposed. It consists of five fast algorithms which is accomplished by hierarchical classification trees at coding unit (CU) level, prediction unit (PU) level and transformation unit (TU) level respectively. At the beginning of proposed algorithm, intra features and inter features which describe the texture and context properties of CU, PU and TU are extracted from the training set. Then the classification trees for CU, PU and TU are generated by carefully selecting features and designing the classification criteria. By analyzing the spatiotemporal correlation, two strategies including early termination and early split are applied to fast coding by referring to these classification trees. The objective evaluation demonstrates that the proposed algorithm can significantly reduce coding complexity with little compression loss. Particularly the subjective evaluation based on similarity measurement for color histogram approves that decoded video quality between the original HM16.9 algorithm and the proposed algorithm is nearly identical.

Modeling and Analyzing Graph Algorithms by Means of Graph Transformation Units.

Modeling and Analyzing Graph Algorithms by Means of Graph Transformation Units.

Вдосконалення методу контролю ізоляції блока ‘’генератор-трансформатор’’

In the conditions of significant aging of the main production capacities and prolongation of the service life of electrical equipment of power plants of Ukraine, the question of development and implementation of methods of continuous control of the technical condition of the generator–transformer unit equipment is urgent. Modern information-measuring systems and relay protection terminals, operated on generator–transformer units, enable control of electrical, thermal, mechanical parameters and parameters characterizing the status or position of technological fittings and auxiliary equipment, as well as providing relay protection of electrical equipment a wide range of possible damage. However, the existing information-measurement systems do not allow the tracing of the following electrical parameters of the stator winding isolation such as resistance, capacitance and tangent of angle of the dielectric loss, and relay protection may be insensitive to the occurrence of single-phase ground fault near the neutral point of the stator winding and symmetric decrease of parameters of the stator winding insulation, and does not allow detecting the occurrence of damage at an early stage of its development and signal this to the service personnel. There is also the possibility of false actuations at unit start-ups due to the asymmetry of voltages in the machine phases, which is especially acute in synchronous hydrogenerators. The paper proposes a method of controlling the isolation of a stator winding of a synchronous generator operating in a block with a transformer, a block diagram and basic formulas for signal processing and calculation of electrical insulation parameters. The proposed method is based on the overlay on the circuit containing the stator winding, alternating voltage signals with a frequency lower than the rated network frequency, DC voltage, the use of energy of the pre-charged capacitor and the calculation of the isolation parameters of the generator–transformer unit. The proposed solutions will allow increasing the efficiency of operation of power units by providing operational and repair personnel with reliable information on the technical condition of isolation of equipment in the scheme of power unit output.

Multi-Layer Transformer Aggregation Encoder for Answer Generation

Answer generation is one of the most important tasks in natural language processing, and deep learning-based methods have shown their strength over traditional machine learning based methods. However, most previous deep learning-based answer generation models were built on traditional recurrent neural networks or convolutional neural networks. The former model cannot well exploit contextual correlation preserved in paragraphs due to their inherent computation complexity. For the latter, since the size of the convolutional kernel is fixed, the model cannot extract complete semantic information features. In order to alleviate this problem, based on multi-layer Transformer aggregation coder, we propose an end-to-end answer generation model (AG-MTA). AG-MTA consists of a multi-layer attention Transformer unit and a multi-layer attention Transformer aggregation encoder (MTA). It can focus on information representation at different positions and aggregate nodes at same layer to combine the context information. Thereby, it fuses semantic information from base layer to top layer, enhancing the information representation of the encoder. Furthermore, based on trigonometric function, a novel position encoding method is also proposed. Experiments are conducted on public datasets SQuAD. AG-MTA reaches the state-of-the-art performance, EM score achieves 71.1 and F1 score achieves 80.3.

Valorization of Agricultural Waste: Theoretical Estimation and Experimental Biomethane Yield from Cashew Nut Hulls

Biomethane potential production from cashew nut hulls, an agricultural waste, was carried out using old and fresh hulls as substrates. Samples were taken from old hulls (around 8 years old) and fresh hulls produced in cashew scale transformation units at Bobo Dioulasso/Burkina Faso. Physicochemical parameters showed that cashew hulls can be a good candidate for anaerobic digestion. But high acidity, total phenols and lignin tenor could be a constraint for anaerobic bacteria. Theoretical biochemical methane potential showed high value of 666.937 CH4 L. (Kg VS)-1 and 526.206 CH4 L. (Kg VS)-1 for crushed fresh and powdered old hulls, respectively. Experimental biochemical methane potential showed significantly low potential of 1.982 CH4 L. (Kg VM)-1 and 46.840 CH4 L. (Kg VM)-1 for fresh and hold hulls, respectively. Pretreatment for optimization, chemical composition and co-digestion system must be expected for a better anaerobic digestion performance.

New adaptive coordination approach between generator-transformer unit overall differential protection and generator capability curves

This paper presents a new method to increase the reliability of the generator-transformer unit overall differential protection with use of the capability charts. The main objective of proposed method is preventing the false tripping under both heavy external solid-faults associated at Generator Step-Up Transformer (GSUT) HV Side and Unit Auxiliary Transformer (UAT) LV Side, load rejection either house load rejection or zero load rejection, and synchronization. Also, the proposed method simultaneously detects both faults at low voltage side of UAT where the fault current is very small and near to normal load current comparing to generator capacity and single-line-to-ground faults at GSUT Low voltage side (generator terminal) due to the transformer delta connection that isolates the zero-sequence component from the network side. The presented method is based on using adaptive setting (three selected settings) for the generator-transformer unit overall differential protection to raise the characteristic setting under the external fault, load rejection and synchronization and decrease the characteristic setting under internal high-impedance fault. The suitable setting is selected according to the location of the generator operating point inside the generator capability curves. The generator capability curves are divided into four operating regions, where each one has a different differential characteristic setting having dual-rate of change of the differential current. The four operating regions are normal load operation and high impedance internal fault; heavy external and internal faults; load rejection and synchronization; and at under excitation operation without faults, respectively. The real dynamic simulation of the power station has been conducted by ATP/EMTP software for the large steam turbine driven synchronous generator. Extensive simulation case studies for internal faults and system disturbances are investigated as well as practical recorded signals.

Measurement-based frequency-dependent model of a HVDC transformer for electromagnetic transient studies

A wide-band, frequency-dependent five-terminal model is developed that represents one HVDC transformer unit in the French-English IFA2000 HVDC interconnection. Three such interconnected 1-ph units constitute one 3-ph transformer bank needed in 12-pulse conversion. The model is obtained via admittance frequency sweep measurements on the transformer's terminals, including common-mode measurements to capture the high-impedance coupling to earth at lower frequencies. The data set is modified to reduce the magnetizing current to a realistic level by a novel eigenvalue scaling procedure. The final data set is subjected to modeling by a stable and passive rational model while utilizing a mode-revealing transformation to retain the accuracy of the small eigenvalues that are related to the high-impedance coupling to earth. The paper describes details related to the measurements and modeling steps as well as the many intermediate accuracy validations that were done. Also is described challenges in the measurements that resulted due to interference of the measurements by a nearby 400 kV overhead line. The model is applied in a time domain simulation of the complete HVDC link in normal operation where voltage waveforms resulting from line commutations are compared against those by a classical model with added stray capacitances.

Latent transformations neural network for object view synthesis

We propose a fully convolutional conditional generative neural network, the latent transformation neural network, capable of rigid and non-rigid object view synthesis using a lightweight architecture suited for real-time applications and embedded systems. In contrast to existing object view synthesis methods which incorporate conditioning information via concatenation, we introduce a dedicated network component, the conditional transformation unit. This unit is designed to learn the latent space transformations corresponding to specified target views. In addition, a consistency loss term is defined to guide the network toward learning the desired latent space mappings, a task-divided decoder is constructed to refine the quality of generated views of objects, and an adaptive discriminator is introduced to improve the adversarial training process. The generalizability of the proposed methodology is demonstrated on a collection of three diverse tasks: multi-view synthesis on real hand depth images, view synthesis of real and synthetic faces, and the rotation of rigid objects. The proposed model is shown to be comparable with the state-of-the-art methods in structural similarity index measure and $$L_{1}$$ metrics while simultaneously achieving a 24% reduction in the compute time for inference of novel images.

A VVC Proposal With Quaternary Tree Plus Binary-Ternary Tree Coding Block Structure and Advanced Coding Techniques

This paper describes a video coding technology proposal submitted by MediaTek in April 2018 in response to a joint call for proposals (CfP) issued by ITU-T VCEG and ISO/IEC MPEG. The proposal uses the conventional block-based hybrid coding approach with a breakthrough design of block structure, substantial improvements of coding tools, and new inventions of loop filtering techniques. First, the block structure is designed using a highly flexible partitioning scheme, where each coding tree unit in a picture is split into multiple coding units (CUs) by a recursive quaternary tree followed by a recursive binary-ternary tree. The prediction unit (PU) and transform unit (TU) concepts are unified with the CU concept, i.e., PU and TU are basically the same as CU. Moreover, inter prediction, intra prediction, transform, quantization, in-loop filtering, and entropy coding are all improved. Finally, new loop filtering techniques are invented, where the proposed convolutional neural network loop filtering is of particular interest. The proposed video codec achieves 43.81% average bit rate savings based on objective measures compared to the High Efficiency Video Coding (HEVC) anchors and is among the best-performing CfP responses both objectively and subjectively. It has been partially adopted into the working draft of the Versatile Video Coding (VVC) standard.

Top oil heat distribution pattern of ONAN corn oil based transformer with presence of hot spot study using FEMM

Transformer thermal modelling is a crucial aspect to be considered as this may help the determination of heat capacity of transformer. This paper present, simulation study on Oil Natural Air Natural (ONAN) transformer heat distribution pattern with and without presence of hot spot temperature (HST). This paper aims to compare the effects of different HST value at different locations inside the transformer unit as well as to evaluate the top oil thermal behaviour of corn oil as cooling mechanism in a transformer. To achieve aforementioned objectives, three HSTs were introduced to the 30 MVA transformer winding to find the total heat build-up in the top of the transformer tank. The outcome of thermal properties is examined using x-y temperature plot. From the results found that the location of HST affects overall transformer’s temperature. HST at the top of the winding give a significant effect compared to when HST is at the bottom of the winding. It is also evident that the usage of corn oil reduced the temperature distribution of the transformer. The findings suggest that the temperature distribution study especially on transformer is important to monitor in-service transformer in a non-invasive manner.

A Tunable Selective Encryption Scheme for H.265/HEVC Based on Chroma IPM and Coefficient Scrambling

Designing selective encryption (SE) schemes for H.265/HEVC has been attracted much attention with the advent of H.265/HEVC codec in the past two decades. However, the most SE algorithms for H.265/HEVC encrypt the syntax elements in the bypass mode to keep the bit rate. Moreover, the edge region of the video data is not sufficiently protected. To produce large visual distortion and edge loss, a tunable SE scheme for H.265/HEVC based on the chroma intra prediction mode (IPM) and coefficient scrambling is proposed. First, a pseudo-random number sequence is generated by AES-CTR. Then, the prediction, residual, and reconstruction information in the H.265/HEVC encoding process is encrypted by a pseudo-random sequence. It encrypts the syntax elements of context-based adaptive binary arithmetic coding (CABAC) in the bypass mode. Some syntax elements, including chroma IPM in the regular mode, are encrypted as well. To further protect the edge information, a coefficient scrambling is adopted. The edge information of each frame is extracted and the transform units (TUs) are classified according to it. Then, the coefficients of the TUs containing edge are scrambled. Finally, a sign used for marking the type of each TU is embedded into a coefficient. The experimental results and analysis show that the proposed scheme has better visual distortion and subjective evaluation results compared with some existing H.265/HEVC SE algorithms. Meanwhile, users can flexibly use the proposed SE scheme according to encryption performance and bit rate requirements, which is attractive in the scenario of protecting video in cloud servers.

A transform size based quantization for high efficiency video coding

Quantization is a key component in High Efficiency Video Coding (HEVC) standard. It enhances coding efficiency, and also introduces quantization distortion which causes degradation of the quality of the reconstructed video. In current framework, HEVC has adopted more transform sizes, and it is obvious that the transform unit (TU) with different transform size has different feature. A TU-level quantization technique, namely an adaptive quantization step size Q along with a fixed transform size is proposed in this paper. The proposed algorithm is implemented in HM software. Compared with HM anchor, the proposed TU-level quantization step adjustment (TUQA) method achieves an average of 0.32%, 2.34% and 2.58% BD bitrate saving for luminance and chrominance components, respectively. The largest BD bitrate saving is up to 1.0% for luminance and 3.8% for chrominance.