OpenUCT :: Browsing by Author "Gaunt, C Trevor"

Browsing by Author "Gaunt, C Trevor"

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Open Access
Active filter current compensation for transmission optimisation
(2015) Carpenter, Paul Andrew; Gaunt, C Trevor; Malengret, Michel
This dissertation is based on the fact that any m-wire electrical system can be modelled as m-equivalent Thevenin voltages and impedances when viewed from any node. The dissertation describes how to calculate the optimal distribution of currents, so a specific amount of power can flow through and reach the network equivalent Thevenin voltages with minimal losses. The optimal current distribution method uses a recently patented method which calculates the optimal currents for each of the wires which are shown to be obtained from the Thevenin parameters and power flow at any instant in time at any node. Once the ideal currents are found, these can be obtained by active and passive devices to inject a specific amount of power (positive and negative) as to compensate existing currents. The focus is particularly on the proof of concept by simulations and physical experiments with work not specifically described in the patent with more emphasis on the optimisation to active compensation. It is explained and shown how this can be implemented using the Malengret and Gaunt method. This method reduces the cost in application where not all the currents need to be processed through a converter (e.g. inverter) but only the difference between the existing and desired optimal currents. A smaller shunt parallel converter can result with ideal current flow without the need for interrupting the currents as described in the present patent. The methodology is explained and demonstrated by simulation.
Open Access
Applying the Herman-Beta probabilistic method to MV feeders
(2015) Chihota, Munyaradzi Justice; Gaunt, C Trevor; Herman, Ronald
The assessment of voltage drop in radial feeders is an important element in the process of network design and planning. This task is however not straight forward as the operation of modern power systems is highly influenced by a variety of uncertain and random variables such as stochasticity in load demand and power generation from renewable energy resources. Classic deterministic methods which model load demand and generation with fixed mean values consequently turn out to be inadequate and inaccurate tools for the analysis of power flow in the uncertainty-filled system. Statistically based methods become more suitable for such a task as they account for input variable uncertainties in their calculation of load flow. In the South African context, the Herman Beta algorithm, a probabilistic load flow tool developed by Herman et al. was adopted as the method for voltage assessment in Low Voltage (LV) network. The method was shown to have significant advantages compared with many other probabilistic methods for LV feeders, as investigated by Sellick and Gaunt. Its performance with regards to speed and accuracy is superior to deterministic, numeric probabilistic and other analytical probabilistic methods. The evolving connections of smaller generators, referred to as Distributed Generators (DGs), to the utility grid inspired the extension of the HB algorithm to active LV distribution networks. The HB algorithm was however formulated specifically for LV feeders. The assumptions of purely resistive feeders and unity power factor loads make it unsuitable for the Medium Voltage (MV) distribution network. In South Africa, deterministic methods are still being used for network design in MV distribution networks. This means that the drawbacks of such methods, for example inaccuracy and computational burden with large systems, are characteristic of the quality of network design in MV feeders. The performance of the HB algorithm together with the advantages and superiority of load modelling using the Beta probability density function (Beta pdf) suggested that modifying the input parameters could allow the HB algorithm to be used for voltage calculations on MV networks. This work therefore involves the adaptation of the way the HB algorithm is used, to make it suitable for voltage calculations on MV feeders. The HB algorithm for LV feeders is firstly analysed, coded into MATLAB, tested and then validated. Following this, the input parameters for feeder impedance and load current are modified to include the effects of reactance and non-unity power factor loads, using approximate modelling techniques. For reactance, the modulus or absolute value of the complex impedance is used in place of the resistance, to compensate for the line reactance. The load current is adjusted by inflating it by the power factor. The results of calculations with the HB algorithm are tested against a Monte-Carlo Simulation (MCS) solution of the feeder with an accurate model (full representation of feeder impedance and load power factor). The approach is extended to include shunt capacitor connections and DG in voltage calculations using the HB algorithm and testing the results with MCS. The outcomes of this research are that the approach of adjusting the input parameters of line resistance and load current significantly improves the accuracy of calculations using the HB algorithm for MV feeders. Comparison with the results of MC simulations indicates that the error of voltage calculations on MV feeders will be less than 2% of the 'accurate probabilistic value'. However, it is not possible to predict the error for a particular application.
Open Access
Cost comparison of hydropower options for rural electrification in Rwanda
(2012) Nsengiyumva, Anicet; Gaunt, C Trevor; Herman, Ronald
The decision to develop a hydropower plant depends on several factors, which cost is the most significant. This thesis, entitled "Cost comparison of hydropower options for rural electrification in Rwanda" intends to show that the use of a large number of mini hydropower plants for electrification of sparse rural areas in Rwanda is the least cost option when compared to installing either a single small or large hydropower plants. This is done by considering rural households to be randomly distributed and the model composed by 98 rural villages having three different population densities is used to test the validity of the hypothesis. Three different hydropower options providing the same level of service to rural households were used for the cost comparison. The relationship between the electrification cost per household versus the population density is deduced. Many distribution technologies can be used in rural areas and the accurate selection of the appropriate distribution technology is the main concern as it affects the cost of the whole distribution system. The rural network should be carefully designed so that the sizing of conductors to be used for LV and MV network is properly done at a low cost. The high distribution cost depends largely on the size of power to be delivered. Based on these findings, the cost comparison of mini, small and large hydropower schemes for rural electrification in Rwanda is discussed.
Open Access
Decision aiding in off-grid electrification projects: the role of uncertainty acknowledgement and objectives alignment
(2010) Bekker, Bernard; Gaunt, C Trevor
Most completed South African off-grid electrification projects have failed to contribute significantly to the sustainable development of the communities they supply. The hypothesis of this research is that the root causes of these failures can often be found in the pre-implementation decision making (planning) processes, specifically in three areas: 1. Decision aiding approaches and tools, aimed at supporting the decision making process, are either not used or do not support high quality decisions. 2. Uncertainties that can impact the project negatively are often not acknowledged (identified) initially, and can therefore not be addressed proactively. 3. The primary project objectives often do not align with sustainable development objectives, which mean that even if all the project objectives are achieved (i.e. a successful project) the project still does not contribute to sustainable development. The process of validating this hypothesis results in several outputs aimed at improving the contribution of future off-grid electrification projects to sustainable development: A framework of primary energisation objectives for sustainable development is developed, which defines what the outcomes of a successful off-grid electrification project should be. High quality decision making is defined, and a framework of decision aiding characteristics that support high quality decision making is developed against which decision aiding approaches and tools can be evaluated. The concept of soft and hard uncertainties is introduced, and it is shown that most of the social and institutional unacknowledged uncertainties in South African off-grid projects are hard. Hard uncertainties are impossible to represent probabilistically, and are difficult to include in traditional single-dimensional (mostly cost-based) decision aiding approaches and tools. A degree of surprise tool, based on Shackle's measure of a decision maker's degree of surprise at a future outcome becoming reality, is developed to act as an example of how hard uncertainty can be acknowledged in the decision making process. p14 - Abstract Soft uncertainty in the decision process is quantified for two examples: renewable energy system sizing, where an adequacy confidence index is proposed, and renewable energy resource estimation, where the accuracy and applicability of RETScreen and Homer within a South African climatic context are analysed. Finally, the above outputs are integrated into an existing decision aiding process and applied in order to demonstrate the value of decision aiding which includes uncertainty acknowledgement and objectives alignment. The applicability of the results of this research is not limited to off-grid electrification, and can be of value within any developmental project aligned with sustainable development, especially where social and institutional uncertainties are prevalent.
Open Access
Definition of apparent power in 3-phase 4-wire non-sinusoidal power systems
(2008) Malengret, Michel; Gaunt, C Trevor
The thesis starts by collating and comparing most power theories in the instantaneous and average power domain. The instantaneous theories are reformulated and classified into three groups, which can be linked with one equation. Introducing a new instantaneous theory based on vector space allows the fundamental properties of the groups to be examined and provides the means to extend instantaneous power into the rms domain and calculate the compensating currents required. The approach results in power components that can be attributed a real physical interpretation. The new approach to three phase power theory has significant potential for education, the practical design of active compensators, and the revision of international standard definitions of power.
Open Access
Design of a power profiler for domestic load research analysis
(2012) Stowe, Grant; Gaunt, C Trevor
This dissertation presents the development of a proof-of-concept measurement instrument to satisfy the requirements of the University of Cape Town's Load Research Group. The new instrument needed to make use of current technologies to cost-effectively measure multiple residential households and provide remote communications capabilities for reliable remote data retrieval. Measurement of three-phase 4-wire configurations was necessary as well as the ability to create second-based profiles of consumer voltage, current and active, reactive and apparent powers for load identification purposes. The main components of a measurement system were identified and prototype development was split into two stages: component integration testing and final product integration. The product was called the Power Profiler and two early prototypes were developed to test the main measurement and processing components and mechanical integration to create a compact versatile test instrument. Energy measurement ICs were used instead of discrete sampling of voltage and current to improve accuracy and allow the use of a low- cost and easy to program digital signal controller for measurement processing and storage. Several communication options were incorporated into the Power Profiler including remote GSM and local USB and Bluetooth communication. The third prototype was subjected to full calibration testing with a Chauvin Arnoux power quality analyzer used as the reference meter. The Power Profiler proved to be a high accuracy instrument with a typical inaccuracy of 0.4% for RMS voltage (over a 20:1 range), 0% for RMS current, 1.1% for active power, 0.3% for reactive power and 0.1% apparent power versus the reference meter. To validate the Power Profiler measurement functionality it was connected to a residential household in conjunction with the reference meter and 4 hours of measurement data was captured for comparison. After a successful validation the Power Profiler was then left to capture another 43 hours of measurement data using a 5-second, 10-minute and 2-hour measurement profile. This data was then analyzed to see if non-intrusive load discrimination could be performed. From the measurement and validation data several common household appliances were identified including the refrigerator, geyser, kettle, microwave and washing machine. The Power Profiler stores not only the average values measured between recording intervals but the maximum and minimum levels as well. This data proved very valuable for the detection of voltage dips and swells that would otherwise have gone unreported by a conventional power meter. The maximum statistic also effectively showed the startup current of motor-based appliances such as the refrigerator and washing machine which greatly assisted with load discrimination. The embedded software for the Power Profiler was split into several software tasks to simplify code maintenance and future development. A C# PC Control and Configuration application was developed to automate calibration as far as possible, and to allow an operator to configure and upload measurement data from the Power Profiler. Extensive use of object-oriented programming techniques was made to allow the reuse of the interface and control software in future applications by other developers. Remote communications capabilities were demonstrated over GSM GPRS connections to allow the retrieval of measurement data from field-deployed Power Profilers. The ability of the Power Profiler to simultaneously record second-, minute- and hour-based profiles and to allow the operator to decide which of this measured data to upload is highly effective in managing remote communication bandwidth and reducing overall operating cost of the system. The Power Profiler product proved to be a cost-effective replacement to the currently used logger and offered more channels with higher resolution measurement and profiling capabilities in a compact instrument. Remote communication capabilities reduces the overall operating cost of the system and simplified measurement retrieval. The ability to easily custom-develop software for both the Power Profiler and PC-based applications made it a flexible instrument valuable for research-orientated applications.
Open Access
Designing low voltage feeders to meet quality of supply specifications for voltage variations
(2012) Kadada, Holiday C; Gaunt, C Trevor; Herman, Ronald
The provision of electricity has become a global necessity. In the developing world, residential electrification has become a tool for poverty alleviation. Unfortunately connecting residential customers to the grid, particularly in the low income communities, is more of a social task as the expected returns from the investment are unlikely to cover the costs to electrify and supply the communities. In such cases it is necessary to not over- or under-design a low voltage (LV) distribution network as this leads to unnecessary capital expenditure. The main source of uncertainty in designing LV residential distribution networks has been found to be the mode used to model the residential load. Residential electricity demand is a stochastic parameter dependant on the behaviour and occupancy patterns of household occupants. Traditionally the After Diversity Maximum Demand (ADMD), which is in essence and average value of load per household, was used to model load. However, using a singular value to describe the complex random nature of load is misleading. Probabilistic methods have been adopted to model residential load behaviour as these methods are better suited to representing the stochastic nature of the load. The Beta probability function was found to be the best representative function of residential load as its characteristics were reflective of the attributes of residential load. Studies on pre-existing LV networks in South Africa have found that these networks are operating outside of Quality of Suppy (QoS) regulation. The current QoS guideline of South Africa NRS 048-2 stipulates that 5% of measured supply voltage levels measured during a certain period are allowed to be outside the QoS compliance limits. This means that 95% QoS compliance of supply voltage levels is required for all LV networks. This QoS condition has not currently been worked into the design parameters. If a network is operating out of QoS guidelines a network upgrade is necessary. This research showed that the main source of the QoS violations of these networks was due to the risk levels used to calculate the expected voltage drops during the design stage of the networks. Typically, 10% risk is used for voltage drop calculations. This means that a best case of 90% compliance is expected which is outside the 95% compliance limit required by NRS 048- This study focused on two objectives. The first was to derive design parameters that are representative of residential load and can be used to design LV networks that comply with QoS specifications. The second was to define a means or develop a model for LV network designers to distinguish the parameters appropriate for a design, based on the customer class to be electrified. In this investigation new design parameters were derived that incorporate the 95% compliance limit of NRS 048-2 allowing LV networks built based on the new parameters, to operate within QoS limits. The parameters were derived using residential load data collected in South Africa since the early 1990's. An equation was also derived which allows countries with only ADMD data available to calculate QoS design parameters suitable for their situation.
Open Access
Determining preferred substation configurations based on reliability and cost
(2016) Van der Merwe, Johanette; Gaunt, C Trevor
Many different substation configurations exist, each with its own space requirements, reliability and cost. Distribution planners need to choose between these numerous layouts and suggest the preferred substation configuration for future networks, but often don't understand the advantages and total life cycle cost associated with each. The aim of this research is to identify a simplified approach that can be used to determine a set of preferred substation configurations that minimises the total life cycle cost of the substation. An analytical approach is considered which uses deterministic reliability assessment to determine the load-based and economic performance indicators for different substation layouts. This analytical approach builds on the simplified reliability estimation approach developed by Van der Merwe (2014). This simplified approach is sufficiently complex to ensure that errors are not one-sided, while at the same time minimising the number of calculations of the reliability evaluation. A cost estimation tool was developed to determine the utility cost for each of the substations. The purpose of this tool is to prepare preliminary estimates of substation life cycle costs during the planning stage, based on conceptual design information. The value based reliability planning approach (VBRP) is used to determine the substation configuration with the lowest life cycle cost, given the specified design criteria. This substation is then the optimal configuration for the specific design criteria. The research considers 432 different substation configurations, and 720 different design criteria. This results in 311 040 different substation layouts. The approach was programmed into an MS Excel model and this model was used to compare the 432 different substation configurations for each of the 720 different design criteria and 18 different customer damage functions, i.e. repeating the comparison of the 432 different substations 12 960 times. The time required to perform one comparison of the 432 different substation configurations for one given design criteria and customer damage function is approximately 2 seconds. The process was automated and the time required to run through all the design criteria and customer damage functions was 8 hours 46 minutes on a standard laptop with an i5 processor. The optimal substation configuration obtained for each of the 12 960 scenarios were analysed and clustered in order to derive the preferred set of substation configurations. Through this process the 432 different substation configurations were reduced to only 17 different substation configurations.
Open Access
Determining the optimal nuclear safety regulatory approach for South Africa's expanding nuclear power industry
(2018) De Araujo, Jenna; Gaunt, C Trevor; Oaker, Bradley
South Africa is poised to expand significantly its nuclear power generation industry. Considering that the current South African nuclear safety regulatory approach is applied to regulate the operation and maintenance of one mature nuclear power plant, it is expected that significant adaptation of this approach will occur for the regulatory system to accommodate the planned industry expansion. This dissertation tests the hypothesis that the optimal nuclear safety regulatory approach for South Africa’s planned nuclear industry can already be determined by systematically comparing the suitability of various alternatives in use in the international nuclear industry. Investigating the validity of this hypothesis improves the understanding of the possibilities available for future nuclear safety regulation in South Africa and aids preparations and decision-making in this regard. Research was conducted on the various nuclear safety regulatory approaches applied internationally and on what determines the suitability of each approach in different circumstances. The characteristics of South Africa’s current and planned nuclear power generation industry were investigated. Applying multi-criteria decision making analysis methodology, a test was developed and used to systematically assess the relative suitability of the various regulatory approaches to the South African context. The three primary approaches to nuclear safety regulation considered were the prescriptive approach, the performance based approach and the goal-setting approach. Based on currently available information, the test results show that the goal-setting regulatory approach is the optimal approach for South Africa’s planned nuclear power industry. However research findings also show that the state level bilateral cooperation the South African government would pursue to develop South Africa’s fleet approach to the 9,6 gigawatt nuclear new build programme may have sufficient influence on South Africa’s nuclear industry to change South Africa’s optimal nuclear safety regulatory approach or make this plant specific. The benefits of aligning South Africa’s nuclear safety regulatory approach with the approach applied in the fleet vendor company’s country of origin may outweigh other considerations. The vendor company for South Africa’s nuclear new build programme is not yet known. Even though systematic comparison of the suitability of various regulatory approaches shows that the goal-setting nuclear safety regulatory approach is the optimal approach for South Africa, the hypothesis is shown to be false. The optimal nuclear safety regulatory approach for South Africa’s planned nuclear industry cannot already be determined, since bilateral cooperation with the nuclear new build fleet vendor company’s country of origin may be the dominant factor in shaping South Africa’s nuclear safety regulatory approach. In the interim and in the event that strategic regulatory alignment for the new build fleet is not embarked upon, the research findings and test results have an important implication: Applying the goal-setting approach as the dominant nuclear safety regulatory approach can optimize nuclear safety regulation of South Africa’s nuclear industry.
Open Access
The development and testing of a fault-tolerant series resonant distribution network
(2004) Cross, Nicola; Gaunt, C Trevor
Includes bibliographical references.
Open Access
Distribution network development planning with quality of supply (QOS) costing
(2002) Fipaza, Mmeli; Gaunt, C Trevor
The report outlines details of research in distribution network development with consideration of costs due to quality. Network planning methods are diverse with the common objective of establishing minimum cost options without violating network constraints. The selected network alternative is directed to meet customer requirements. Network planning models have evolved from consideration of simplistic models to multi variable and more realistic approaches. It is not always possible to achieve the desired outcome because planning is a difficult and complex task. There are usually uncertainties due to vague or no information available about the long-term (15-20 years) planning. The uncertainties generally result in risks, which have to be sufficiently analysed before reaching planning decisions. The recently proposed Minimum Risk Criterion is not a preferred risk resolution approach because it suggests that utilities should not establish expensive networks due to cost risk. Uncertainty modeling approaches based on fuzzy logic are proposed as the solution for analysis of uncertain conditions where very limited information is available. Costs in distribution lines are usually due to capital investment and operating costs. Distribution capital costs are primarily due to cost of conductor, s ucture and insulator. The cost of conductor and structure varies with size and type. Insulator costs do not vary significantly with variations in insulator type and properties. Quality related costs are a relatively new concept in distribution costing and are developed in the research. They are primarily due to mitigation, condition monitoring and interruptions. Quality mitigation costs are defined in the mitigation cost models in Figure 4- 8 and Figure 4- 9. The impact cost values in the models were established on the basis of assumptions, which require further research. According to CTLab [12], quality-monitoring equipment costs could vary from R50, 000 to R250, 000. Interruption costs are incurred through penalty cost and revenue losses. The penalty cost is similar to the revenue loss cost in many respects but is incurred when the standard limits are violated. Revenue loss costs are applicable whenever the frequency or voltage deviates from the nominal. It may be preferred to accept revenue losses where mitigation is expensive.
Open Access
Duality derived topological model of single phase four limb transformers for GIC and DC bias studies
(2017) Borrill, Leslie David; Gaunt, C Trevor
Geomagnetic disturbances brought about by solar activity cause geo-electric fields in the Earth that drive geomagnetically induced currents through the earthed neutrals of transformers and through power transmission networks. The flow of these currents causes the magnetic cores of transformers to half-wave saturate. Saturated transformers pose problems for power system operators since they can cause harmonics, transformer heating, mal-operation of protection relays, generator heating and vibration, and consume a large reactive power that can cause voltage collapse. Network studies of slow transient phenomena such as transformer half-wave saturation require appropriate models with parameters that represent the transformer transient state aptly. In this thesis a novel duality derived reversible model is developed of a single phase four limb transformer. The test transformers' non-step lap butt type core joints are shown to be problematic and the model is developed further to include the core joints. Due to the irregular core stacking method joint parameter determination is at best an approximation and the model is reduced to a duality compliant equivalent pi model for accuracy reasons. The pi model parameters and saturation characteristics are determined through laboratory testing and a complete pi model is presented. An understanding of a single phase transformer's physical behavior to slow transients is undertaken through the use of appropriately developed test circuits. Search coils are used extensively to understand the transformer core's behaviour through flux mapping of the core and stray flux in the surrounding air space when the transformer saturates. Three phase testing is included using a three phase bank of test transformers. The electrical measurements of waveforms are analysed and fast Fourier transforms carried out to obtain the harmonic components. The effect on a motor load of the distortion caused by transformer half-wave saturation is determined. A novel method of determining the effective core joint area of the problematic non-step lap butt type core joints is developed and a joint utilization factor is proposed that can be used in the absence of transformer manufacturer design information about this joint type in other transformer models.
Open Access
Dynamic-systems analysis of self-excitation associated with a capacitor-coupled substation (CCS) - induction machine system
(2006) Reeves, Kevin; Gaunt, C Trevor
The purpose of this thesis is therefore to establish the cause of SSR at the Meru-Petronet system, and other similar systems, and investigate various compensation techniques.
Open Access
Effect of conductor size on the total cost of electricity distribution feeders in South African electrification
(2006) Carter-Brown, Clinton Geoffrey; Gaunt, C Trevor
There is an optimum conductor size that minimises the lifetime cost of domestic electrification networks. The lifetime cost consists of the initial capital cost and ongoing running cost. Technical load losses are an important running cost and consideration for conductor size optimisation. Traditional conductor size optimisation methods base technical load loss costs on upstream generation and network costs. These loss costing methods assume that consumers behave as constant power loads. The impact of conductor voltage drops on changes in consumer energy consumption and demand and hence changes in utility bulk purchase cost and sales revenue are ignored. Traditional load loss calculation methods do not adequately describe the stochastic nature of individual consumer loads. In low-voltage domestic networks traditional methods may account for less than 25% of the actual lifetime running cost due to load losses and conductor voltage drop. It is shown that the results of traditional conductor size optimisation methods are severely compromised.
Open Access
The effectiveness of electricity time of use tariffs in the Western Cape
(2010) Essa, Fagmie; Gaunt, C Trevor
In South Africa, Time of Use (TOU) tariffs have been available to Eskom's customers since 1986. TOU tariffs are intended to encourage users to avoid using electrical energy during the periods at which the national electricity system is stressed during normal operating conditions, i.e. peak periods. It has not always been clear how customers were responding to the different types of Eskom tariffs. A study was done of Eskom's Large Power Users (LPUs) in the Western Cape province of South Africa. Customers were categorised into City of Cape Town (CCT), 2 types of KSACS customers, Agricultural, Non-Agricultural and Rural Municipalities. At least 30 customers within a category were selected as a sample of that category.
Open Access
Effects of geomagnetically induced currents on power transformers and reactors
(2003) Amuanyena, L A T; Gaunt, C Trevor
Bibliography: leaves 106-109.
Open Access
Ensemble estimation and analysis of network parameters: strengthening the GIC modelling chain
(2017) Heyns, Michael John; Gaunt, C Trevor; Lotz, S I
Ensemble Estimation and Analysis of Network Parameters - Strengthening the GIC Modelling Chain - Abstract Large grounded conducting networks on Earth's surface have long been known to be affected by solar activity and geomagnetic storms. Geomagnetically induced currents (GICs) in these quasiantennas are just one of the effects. In modern times, society has become more and more dependent on electrical power and, as a result, power networks. These power networks form extensive grounded conductors and are susceptible to GICs, even at mid-latitude regions. Given a large enough event now, such as the Carrington event of 1859, the direct and knock-on results can be devastating. Such an event is more than just a possibility, it is just a matter of time. With this in mind, the study of the effects of GICs and the modelling of them has become essential to ensure the future security of society in general. GIC modelling makes the assumption that the resultant GIC at a specific node in a power network is assumed to be linearly related to the horizontal vector components of the geoelectric field, which is induced by a plane-wave geomagnetic field. The linear GIC and geoelectric field relation is linked by a pair of network parameters, a and b. These parameters are not easily measurable explicitly but may be estimated empirically. Furthermore, these parameters are traditionally only seen to include network information and remain constant given a stable network. In this work, a new empirical approach to derive estimates for a and b is presented where the linear relation is solved simultaneously for all possible pair of time instances. Given a geomagnetic storm time-series (length n) of simultaneous GIC and geoelectric field data to solve for a and b, taking all possible time instance pairs yields approximately N²/2 estimates for a and b. The resulting ensembles of parameter estimates are analysed and found to be approximately Cauchy-distributed. Each individual estimate resulting from a single pair of time instances being solved is not the true state of the system, but a possible state. Taking the ensemble as a whole though gives the most probable parameter estimate, which in the case of a Cauchy distribution is the median. These ensemble parameter estimates are used in the engineering link of the modelling chain, but the ensembles themselves allow further analysis into the nature of GICs. An improvement is seen when comparing the performance of the ensemble estimates applied to an out-of-sample dataset during the Halloween Storm of 2003 with previous GIC modelling in the South African power network using the same dataset. Analysis of the ensembles has verified certain ground assumptions (specifically the plane-wave assumption and network directionality) made as a first-order approximation in GIC modelling and has also shown that errors from these assumptions are absorbed into empirically derived network parameters. Using a range of estimates from the ensemble, a GIC prediction band is produced. This in itself corresponds to an error estimate in the prediction. For the first time, it has been explicitly shown that empirically derived network parameters show a correlation to the magnitude of the produced GIC. This behaviour is then used to refine the parameter estimation further and allow for real time dynamic network parameter estimation that further improves modelling.
Open Access
Eskom's employees perception on nuclear power in accordance with the IRP 2010 Nuclear Energy Plan
(2017) Chutri, Mithun; Gaunt, C Trevor
The future role of nuclear power in global sustainable development, and particularly in the development of industrialising countries is contentious; the debate is often highly emotive. The Republic of South Africa's (RSA) progress towards its largest nuclear procurement program is taking place in the midst of changes within the African National Congress (ANC) ruling party, an increase in global demand for uranium and growing energy needs within South Africa. Major nuclear accidents such as Chernobyl or Fukushima have set nuclear power plant security on top of the public agenda. The internalisation of governance through the creation of responsible eco-citizenship is a primary technique to screen perceived risk, which works through the course of public participation. Participation however, must include those that drive the objectives within the nuclear context. Eskom's Koeberg Nuclear Power Station (KNPS) has a workforce of more than 2000 employees. In 2016, the Department of Energy (DOE) had decided that Africa's leading power utility will be the owner operator and procurer of the planned 9.6 Gigawatts (GW) (e) nuclear fleet that is set out in the IRP2010 report. The perceptual impact of this workforce that keeps the country's economic lifeblood moving is often understated, which was the focus of this study. This study had a distinct focus on what Eskom employee's perceptions are with respect to the IRP2010 nuclear new build program. It was limited to the Western Cape Province and included views from divisions that may be involved in the realisation of the nuclear project. It is unique in its context, as very little has been documented on employee perception within RSA's nuclear industry. It is comparative to a public perception survey, which had a distinct focus on nuclear risk. The public's greatest concerns were noted to be corruption, project mismanagement, excessive cost and lack of trust in stakeholders. The outcome of this study discovered similarities with the public perception survey, however here within nuclear safety and compliance to business best practice were greater significant factors. Most respondents had sufficient knowledge and support for RSA's nuclear plans set out in the IRP reports. Dimensions of how perception was created were voted as being heavily dependent on the leadership within the organisation. With this in mind, Eskom employees have indicated that they are more likely to influence the public if they have their leadership's support, and have gone as far as selecting nuclear power over renewable energy to drive towards the country's commitment towards low greenhouse gas (GHG) emissions. So while there may be shades of perceptual similarities between the public and Eskom employees, fundamentally this study revealed that these two bodies do not have the same perception on nuclear power. The study revealed that if Eskom employee's nuclear perception is disregarded and mismanaged, it may delay the realisation of the nuclear new build program in line with IRP 2010 timelines. This is mainly due to the concern of adherence to good corporate governance by Eskom's leadership.
Open Access
Estimation of Geomagnetically Induced Currents (GICS) in the Namibian transmission network
(2013) Simon, Magnaem Ngendina; Gaunt, C Trevor
Geomagnetically Induced Currents (GICs) have become a matter of concern not only to networks located in high magnetic latitude regions but also in networks located in mid-latitude regions. GICs pose a threat of transmission equipment damage which could lead to short power interruptions and potentially long term blackouts. Improved modelling techniques are essential in predicting the GICs flowing in the network in order to enable power utilities to reduce the risk of damage to equipment and improve the reliability of their power supply. This dissertation, entitled ESTIMATION OF GEOMAGNETICALLY INDUCED CURRENTS (GICS) IN THE NAMIBIAN TRANSMISSION NETWORK, aims at improving GIC estimation by installing measurement equipment in order to compare measured GIC results with modelled results. The purpose of which is to validate the calculation technique. The Nodal Admittance technique was proposed for the study and was first validated using published data obtained using the a&b parameter method. For the measurement techniques, two methods were found namely direct measurements in the transformer neutral conductor and indirect measurements in the transmission lines. In this dissertation, the former was implemented due to its simplicity in usage.
Open Access
An exploratory study of the sustenance of rural electrification in the Kingdom of Swaziland
(2007) Dlamini, Samuel M K; Gaunt, C Trevor
Includes bibliographical references (leaves 118-127).