Power Engineering

Permanent URI for this community

https://hdl.handle.net/10352/181

Browse

Now showing 1 - 8 of 8

A testing and verification protocol for a modern bus bar transfer scheme based on the transfer philosophy and theory of voltage decay
(Vaal University of Technology, 2020-04) Van Rooyen, Johannes Petrus; Le Roux, B. J.; Walker, J. J., Prof.
This dissertation focuses on the creation of a testing protocol or procedure for verification of a modern motor bus bar transfer scheme. There are four main transfer methods addressed during this study and with it the main parameters affecting the operation of such a system. The complete construction of the simulation and training panel is described and with it the outline of the testing protocol for using this panel is given. Some simulation work was done to calculate the correct verification times based on mathematical formulation to lay out the criteria for verification of transfer methods when testing with a modern three phase test bench. On completion of result documentation, a detailed analysis is conducted to generate the testing protocol which is also discussed in detail. From the test results obtained it was possible to accurately test the 4 common transfer methods using the theory of voltage decay as a guideline, but the protocol will have to be adjusted to suit individual transfer system needs as each transfer system may be unique in design and function although the basic principles outlined during this report will stay the same. Possible steps to take when adjusting the protocol were addressed and some future work for testing motor bus bar transfer schemes was suggested.
Correlation of different methods to determine the corona inception stress on overhead conductors under HVDC application
(Vaal University of Technology, 2022-04-06) Sibanyoni, H. M. B.; Djeumen, J. S.; Walker, J. J., Prof.
This dissertation’s focal point is on the correlation of different methods to determine the corona inception stress on overhead conductors under high voltage direct current (HVDC) application. The corona phenomenon is one of the key elements that should be considered when designing high voltage (HV) transmission lines. This phenomenon is known to compromise the efficiency of transmission lines and may cause electromagnetic interference (EMI) in telecommunication lines. Corona measurement methodologies form an integral part in the detection, measurement and isolation of corona discharges. The international electro-technical commission IEC 60270 specification addresses the electrical method using a coupling capacitor and acquisition unit for the detection and measurement of partial discharges. However, there are also non-conventional methods available, namely the inductive method, which uses high frequency current transformers (HFCT), acoustic methods and optical methods for detection of corona discharges (corona camera). These above-mentioned corona measurement methodologies have various advantages and disadvantages with the main difference being in the location of the sensor. The coupling capacitor is connected directly to the main circuitry of the power system, the HFCT is connected in the earth connection and the acoustic sensor as well as the corona camera being placed at a safe distance away from the system. The electrical method using a coupling capacitor is the only method that can be calibrated to measure current by means of electromagnetic coupling. The HFCT transforms the leakage current containing a frequency bandwidth flowing in the earth connection that are due to corona discharges. The corona camera visualises, locates the corona discharge point and displays the partial discharge intensity by detecting the ultraviolet radiation photon count rate. For the purpose of this dissertation, the following corona measurement methods are under review: Electrical method, inductive method and optical method. The acoustic method was not reviewed because the location of the corona measurement device is the same as that of the optical method, which is at a safe distance away from the power system. The corona measurement tests were performed in a high voltage laboratory using a corona cage. The test methodology was based on gradually increasing the voltage until the corona inception voltage is reached for both positive and negative polarities. The results show a difference in the measured inception voltage for the different methods and that the location of the corona measurement devices has an impact on the measured corona inception voltage. The results indicate that connecting the corona measurement device directly to the main circuitry of the system, as is the case with the electrical measurement method using a coupling capacitor, will be the most sensitive method and result in the lowest measured corona inception voltage.
Design and development of a high efficiency modulated Class E amplifier
(2006-01) Crafford, Crafford, Hendrik Lambert Helberg Hendrik Lambert Helberg; Pienaar, H. C. v Z.
Amplitude modulation is not commonly associated with effective amplifying. This work focuses on implementing amplitude modulation into a high efficiency Class E amplifier. Different types of amplifiers are compared with each other, to show the advantages of using a Class E amplifier. The theory of the Class E amplifier is dealt with in detail. A harmonic filter is designed for the amplifier to make it radio spectrum friendly. The modulation process is implemented with the aid of a transformer into the Class E amplifier. The advantage of this is that the transformer serves both as a radio frequency choke for the Class E circuit as well as a modulator. The implementation of the amplitude modulation into the high efficient Class E circuit was successful. The final Class E circuit had superb efficiency, the harmonic filter showed good harmonic attenuation and the modulation process had low distortion. All this resulted in a fine low power AM transmitter.
Development of a multi-protocol equipment interface for use in renewable energy systems
(Vaal University of Technology, 2023-01-31) Benson, M; Sutherland, G., Dr.; Joubert, A., Dr.
Modern renewable energy systems be it off-grid, grid-connected, hybrid or a combination consisting of different equipment allowing data communication through different wired and wireless methods. The combination of equipment by different manufacturers has an impact on the communication and functionality of these energy systems. The aim of the research is to develop a multi-protocol equipment interface allowing communication between different renewable energy equipment using different communication mediums and communication protocols. The communication protocols to be focused on were Modbus and SunSpec using RS-232, RS-485 and Ethernet as wired communication mediums between the equipment interface and renewable energy devices. The research methodology utilized allowed for multiple cycles to develop the equipment interface. The first cycle focused on the hardware design and the second cycle focused on the design and development of the software algorithm required to retrieve the data from various renewable energy equipment. The equipment interface has shown that it was able to obtain a single data register value using Modbus and SunSpec and that it can gather data values from multiple registers as required by the user for Modbus and SunSpec. The user has to specify communication medium and the registers which are required along with the data types and scale factors depending on communication protocol used.
Displaced neutral on woodpole structures with 300 kv basic insulation level rating (BIL)
(Vaal University of Technology, 2022-03-06) Becker, Taryn Robin; Britten, A. C., Prof.; Walker, J. J., Prof.
The influence that the geometry of the woodpole structure has on the voltage developed across the 500 mm basic insulation level (BIL) coordination gap and conductive bonding accessories is discussed in this dissertation to further understand possible reasons for failures of woodpole structures as experienced in the field. A scaled woodpole structure comprising of porcelain insulators was erected under laboratory conditions to assess the relationship between the voltage developed across the 500 mm insulation coordination gap under balanced and unbalanced system conditions. Other parameters including the leakage current behaviour as well as the phase relationship between the under these conditions were also investigated. The laboratory scaled structure was energised using three single phase 132 kV voltage transformers. Furthermore, a two-dimensional model was developed to simulate the electric field condition in and around the phase insulators and the coordination gap using QuickfieldTM, a finite element (FEM) simulation software. The experimental, as well as the simulation results, showed that the configuration of the insulators has an influence on the voltage developed across the coordination gap. The two structures with different insulator configurations were considered with porcelain insulators. The difference between these configurations was the installation of the insulators, for configuration 1 all the insulators were erected in the vertical upright position whereas for configuration 2 the outer two insulators were inverted downwards in the strain position. The magnitude of the BIL voltage developed across the gap was the highest for configuration 2 under balanced conditions in comparison to configuration 1 when all the insulators are upright, this condition is true for both the laboratory model and well as the simulation model. Certain scenarios were used to compare the scaled woopole model and the 2D FEM model. The parameters such as voltage, leakage current and phase relationship under balanced and unbalanced conditions were considered. Based on the more common network faults such L-L fault, L-G fault, L-L-G and L-L-L-G faults, the approach looks at a more specific fault and the impact this fault has on the deterioration of the wooden structure. The emphasis is on what occurs in the field when a phase is disconnected from its insulator or when more than phase is disconnected from the structure. Included in the analysis, is the influence of the insulator geometry and its role. Findings from the laboratory structure and FEM model indicated that the worse-case condition was for configuration 2, when phase B is disconnected from structure. When two phases were disconnected, results from the FEM model indicated that configuration 1 was worse-case compared to that of the laboratory structure have higher values measured on configuration 2 when only phase A is connected to the structure.
Incandescent light power efficiency: an impact study on the power consumption of the Vaal University of Technology's light sources
(2013-12) Adeniyi, A. O.; Sutherland, G.; Nicolae, D. V.; Joubert, T.
In view of the energy consumption problems, an impact study, extensive laboratory tests and an investigation towards comparable energy saving light sources was carried out on the light sources identified in the survey conducted at the Vaal University of Technology (VUT), Vanderbijlpark campus. Three types of identified incandescent light sources were purchased and extensively tested in order to obtain viable statistical data on the life span, luminance delivered per unit, power consumption and economic effect, as well as identifying relevant energy efficient light sources for replacement purposes. A suitable computerised maintenance program has been developed to be introduced to the VUT that currently does not have a lighting system maintenance program. The case study was located within the empirical-analytical paradigm, using quantitative data. The identified aims and goals place the empirical part of the study in the category of implementation evaluation research that provides an overview of a maintenance plan.
Modelling of transmission line faults using machine learning methods
(Vaal University of Technology, 2023-03-30) Makgai, Maphale Lucas; Sutherland, G., Dr.; Joubert, A., Prof.
Electrical transmission lines are a link between the generation station and the consumer. Any abnormality in transmission lines may result in a prolonged total electricity shutdown if not detected and identified accurately. Malfunctioning of transmission lines contributes to economic destruction and leads to wildfires and damage to electrical equipment. The existing literature has confirmed that 70 to 80 percent of the abnormalities that usually occur in transmission lines are single line-to-ground (L-G) faults. Detecting and identifying such faults will minimise restoration time. Machine learning-based models' accuracy has never been comprehensively tested in detecting and identifying L-G faults in transmission lines under noisy conditions. This study tested a MATLAB machine learning-based model to detect and identify L-G faults when introducing noise on these transmission lines.
Partial discharge evaluation of a high voltage transformer
(2015-02) Kyere, Isaac Kwabena; Walker, J. J.; Le Roux, B. J.
This dissertation is devoted to the study of partial discharge evaluation of a high voltage transformer. The 400 V/300 000 V (300 kV) high voltage transformer in the high voltage laboratory was manufactured in 1967. Given the old age of the transformer and the crucial importance of insulation systems, it is vital to assess the condition of its insulation to ensure the effectiveness and the reliability of the transformer as well as the safety of the personnel using it. In order to achieve that, it is important to evaluate the partial discharge in the insulation system as this is the main cause of destruction of insulation. The phase-resolved partial discharge method was the main method used to perform the partial discharge measurements in this research. Partial discharge measurements were performed on a faulty 11 kV voltage transformer. Defects were also created in samples of solid insulation at predetermined locations with different shapes and sizes. The measurements taken on the 11 kV voltage transformer and samples of solid insulation formed a basis to prove the validity of the assessment methods on the 300 kV transformer. Using the method mentioned above, partial discharges were recorded with respect to the phase of the applied voltage with the aid of a commercial instrument which complies with IEC 60270, (ICM monitor - partial discharge detector from Power Diagnostix Systems GmbH). The observations from this study have furthered the understanding of partial discharge processes. The patterns recorded were analysed in order to conclude about the condition of the transformer. From the partial discharge pattern, the type and location of partial discharges were concluded. The patterns obtained from the transformer reveal that the device is healthy and can be operated up to 200 kV.

Browse

Browsing Power Engineering by Title

Results Per Page

Sort Options