The aim of this study was to assess the electrical performance of the Cahora Bassa HVDC scheme. For practical reasons a database was developed to hold and analyse the performance data. Microsoft® Access 2002 relational database management system was chosen for this work. The principle of simplicity and flexibility were used in the design of the database. The Apollo year 2002 faults data was populated into the database. The database stored the information in a format that enables the user to extract results and the information required by Ciqre, The Ciqre Working Group 14 collects performance information from all the participating HVDC schemes around the world annually. The Apollo converter station's 2002 performance data was compared to other similar HVDC schemes that submitted to Cigre in the year 2002. In addition performance trends were drawn from similar schemes that submitted to Cigre over the past years. The Apollo performance data is quite comparable to other similar schemes in 2002 and over the past years. / Thesis (M.Sc.)-University of KwaZulu-Natal, 2005.

Conventional Current Transformers (CTs) provide the input signal required by protection relays, control equipment and energy metering in power networks. Catastrophic failures of CTs may lead to injury of personnel within the substation, interruption of power supply and damage to adjacent high voltage equipment. One of the causes of CT failures is high values of insulation power factor. Research indicates that with increasing primary insulation power factor values, partial discharges develop between the paper insulation leading to its exponential decay with the end result of an ultimate CT failure. Reports in Eskom Distribution indicated that a number of CTs from one manufacturer were exceeding the specified insulation power factor value. This research was initiated to investigate the impact of high power factor on the premature failure of CTs. This study serves to analyse the significance of power factor on paper-oil insulation within a hair-pin type CT. The internal primary insulation of a hair-pin type CT used in Eskom Distribution is reviewed in terms of its design, construction and relevant tests. Sample CTs rated at 132kV and manufactured in the year 2007 to 2009 from the specific manufacturer were selected for insulation power factor testing. The Doble M4100 diagnostic test system was used to perform the testing that also assisted in providing a comparison between the units with high insulation power factor values and that which were within the specified limits. The results show that the high values of insulation power factor give a direct indication of the dielectric losses (I2R) within that CT, which inadvertently indicates the shortened serviceable life of that CT. High moisture content within the primary insulation, low quality insulating oil and inadequate quality assurance were identified as some of the contributory factors in the CTs non compliance. The effects of high values of insulation power factor are the primary factor for continuous on-line condition monitoring techniques that enable data trending and provide for early warning of an imminent CT failure. The testing of the sample CTs provided a more dynamic approach for recommendations to prevent the installation of such units into the power network. / Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2010.

Demand side management (DSM) interventions aim to influence the way electricity is used by customers through specific actions and programmes. A desired load shape is achieved by encouraging electricity users to consume more electricity at times when excess capacity is available and less during times of constraints. In South Africa, load management is a fixed response between 18:00 and 20:00 and includes load shifting and load curtailment out of the Time of Use (TOU) tariff peak period. Demand Market Participation (DMP), on the other hand, is a more flexible curtailment initiative and is scheduled day ahead only if constraints are expected. This study evaluates the effectiveness of load management and DMP initiatives and proposes an optimised approach. Customer responses to the TOU tariff and the alignment of system and tariff peaks were investigated by making use of TOU metering and system sent out data. The research shows that not all customers respond to the TOU tariff signal. System peaks and TOU tariff peaks are aligned however a number of system peaks occur out of the tariff peak periods. The research further shows that load management and DMP initiatives shift and curtail load effectively. Load management initiatives with an energy efficient component are very effective and highlight the importance of energy efficiency as a whole. Historical system sent out data was analysed and the results show that a significant number of load management initiatives can become more dynamic. It was further evident that curtailment initiatives contribute more to the system than load shifting initiatives. Load management initiatives are initiated by TOU tariff peaks and not system peaks. Load management initiatives could therefore be optimised if system constraints are used as a reference and not TOU periods. It was also evident that load shifting initiatives do not add much value during the low-demand seasons. The results of this study could be utilised to improve DSM initiatives. This study also serves to influence future DSM strategies which will embrace a sustainable DSM programme. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2009.

Large boilers have typically been designed for continuous operation from 60-100% load. With restructuring of electrical supply and in some cases because of local fuel supply constraints, some of these boilers are run for only two shifts per day and this entails warm start ups. A reasonable objective is to bring the plant online as quickly as possible within the equipments constraint and without risk of tripping major plant equipment such as feed pumps and circulation pumps. The project required the development of a model accurate enough to represent the boiler thermal dynamics. The thesis compares the simulated model results with the measured results from a Benson boiler from Majuba power station. The developed model is then used to investigate gain scheduled and robust control approaches to the design of the control system for collector vessel level and evaporator flow rate. Once the control problems are clearly understood, an investigation into fast start up is undertaken. The subject of the start up of Benson boilers has limited open literature. This is because flexibility in plant operation has only recently become an important issues with electricity utilities. The limited research in the field of robust control of start up of Benson boiler has made the extensive work done by both Eitelberg and Boje [2001,2002,2004] state of the art. Most of the research done in this thesis follows from the work done by Eitelberg and Boje. / Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2005.

Modern transmission systems are becoming heavily loaded. In addressing this issue Eskom has been installing series capacitors in their power transmission grids for the purposes of ensuring improved system stability, increased transmittable power, reduced transmission losses, enhanced voltage control and more flexible power flow control. Environmental concerns are also addressed at a fraction of the cost when compared to the alternative. However, with the utilization of series capacitors and their over-voltage protection devices typically the Metal Oxide Varistors and Spark Gaps when installed on transmission lines, several problems are created for the distance protection relays. This is because series capacitors when used on transmission lines can have serious effects on the performance of distance relay protection. This is because of the change of impedance seen by the distance relay since the electrical impedance measured by the relay is no longer a unique correspondence of the physical distance from the relay location to the point of fault when the protection of the series capacitors comes into play. The research results will show that, because of subsynchronous oscillations and voltage inversion phenomena as a result of series compensation, can cause distance protection’s zone 1 directional elements to operate incorrectly, more specific to internal faults which may appear as external faults and external faults which may appear as internal faults. The research will be investigating some of the challenges that are encountered by the distance protection relays when protecting a transmission line incorporating series capacitors. In answering the research question: “What are the issues associated with the utilization of series capacitors on the Eskom Transmission grid to the performance of distance protection?” the Digsilent PowerFactory software simulator package will be utilized to achieve the desired objectives. Other research projects have looked into the research question at hand utilizing the physical REL 531 relays and a real time model of the Eskom Hydra South Network, a system that supplies power to the Western Cape. In this research the author will be looking at the ability of Digsilent and its REL 531 Models to repeat and confirm the same conclusions, before considering possible alternative solutions. The Muldersvlei-Bacchus and Bacchus-Droerivier lines forming part of the Eskom Hydra South Network were selected as the area of focus. The decision to select these two particular mentioned lines as the area of focus was because the studies will be able to cover impact of external series capacitors to both the performance of the relays on lines that are series compensated and those that are not. The performance of the relays will involve analyzing the impact of series capacitors on the relays for faults before and after series capacitors. The research will also be investigating the possibility of utilizing the current supervised zone 1 configuration, which has recently been introduced on some Eskom distance protection relays as a solution, to overcome the impact of series capacitors on the performance of the distance protection relays. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2010.

Eskom (Electricity Supply Commission of South Africa) is the national electrical utility that provides the generation, transmission and distribution of electricity in South Africa. The majority of Eskom's electricity distribution is done with either 11 kV or 22kV electrical overhead networks. An unacceptable number of Eskom's pole mounted power transformers on these networks have been failing over the past six years in the Kwa-Zulu Natal region. The average transformer failure rate for the Distribution Eastern Region was calculated to be 2.4% per annum. International norms seem to indicate a transformer failure rate of between 0.5% and 1.0% per annum as acceptable. The estimated cost of these transformer failures was between R9 million and R13 million per annum for the Eastern Region. Eskom Distribution has seven regions and the total cost of these failures was considerable to the business. These transformer failures contributed an average of 5.3% per month of the Supply Loss Index (SLI) for the Eastern Region, with a maximum contribution of 14.5% per month of the SLI for the region. The SLI is an Eskom performance measure of the unavailability of supply of the networks. The Eskom plant performance database (NAPI) was statistically analysed in detail and a number of field investigations conducted at transformer installations that had failed in the past. Transformer earth electrode resistance measurements were taken in an attempt to identify the cause of these transformer failures. Local transformer manufacturers were consulted and a national transformer refurbishment company's database was analysed during the investigation as part of a holistic approach to the industry related dissertation. The main finding of the NAPI data analysis was that the majority of the transformers failed during lightning storm periods. Another similar Eskom investigation had a sample of failed transformers opened for internal inspection. Signs of lightning damage to either the primary side winding or the primary lead were found. The proposed failure hypothesis was that the transformers required additional lightning protection of the primary side to protect the transformer against lightning. It seemed that the current specification of the Eskom distribution class surge arresters was inadequate to offer sufficient lightning protection of the pole mounted transformers. Practical measures were implemented on existing Eskom 11 kV networks in the Glencoe area as part of an Eskom research project to reduce the high failure rates of transformers. Two experimental networks were established and one control network was used as a reference line. The project implementation was completed at the end of October 1999. The experimental project looked at applying additional primary side lightning protection of the transformers. The main emphasis of the lightning protection on the first network was the use of two distribution class arresters in parallel (double arrester configuration) for each transformer and an understrung conductor connected to the prior structure back from the transformer installation. The second network had the standard single arresters installed on the transformers. A 600mm wood path was placed in series with an earthed down conductor installed on each intermediate woodpole structure to ensure a basic insulation level of 300kV for the network. The control network also had single arresters installed and was a fully insulated network (no earthed down conductor on the woodpoles). Each network was carefully monitored in terms of equipment failures and the performance levels of each network was measured with installed voltage dip recorders near the individual network circuit breakers. The Eskom Lightning Position and Tracking System (LPATS) data was collected and analysed to quantify the lightning activity before the project implementation to that of after project implementation. For the period November 1999 to March 2002 not a single transformer or surge arrester had failed ,due to lightning on the double arrester and understrung conductor configuration experimental network. There were recorded transformer and surge arrester failures on the second experimental network and on the control network. It was found that the practical methods implemented on the networks did not have a negative impact on the performance levels of the networks. Laboratory work was conducted in the high voltage laboratory at the University of Natal, on various metal oxide varistor (MOV) blocks of opened up new and failed surge arresters. This was to determine the effect of MOV blocks in parallel under power frequency and current impulse conditions. In particular, to determine what the effect of parallel MOV blocks with different voltage-current (V-I) characteristics would have on the current sharing and energy absorption capabilities of the individual blocks. The work was performed to simulate the behaviour of two surge arresters in parallel as in the experimental project. The experimental project lines were modeled using the Alternative Transients Program (ATP) simulation package and various parametric studies performed in the single phase conductor simulations. Each network component (such as the line, transformer and surge arrester) and phenomena (such as the effect of corona, the transient earth electrode resistance and voltage flashover) were modeled. The effect of surge arresters in parallel and the use of an understrung conductor arrangement were quantified. A current sharing factor (k-factor) was introduced to quantify the sharing of currents through surge arresters in parallel with different V-I curves. The main finding from the impulse laboratory work was that current sharing between parallel MOV blocks became better at higher currents. This finding was supported by other research work findings, particularly in the field of nuclear fusion research with parallel arresters. The results of the ATP simulations showed that the experimental network with the parallel arresters and understrung conductor arrangement considerably reduced the energy absorbed by the individual arresters. The effect of the double arrester configuration was to reduce the energy absorbed by the individual arresters even with arresters with different V-I characteristics and different manufacturers. The understrung conductor arrangement was found to be the major contributor towards the reduction of the energy absorbed by the arresters. The equivalent circuit of a MOV block for transient studies was proposed and then simulated in ATP. The simulated results were compared to the measured waveforms obtained from the impulse laboratory work. A good agreement between the simulated and measured waveforms was obtained. For existing Eskom networks with high arrester and transformer failure rates, the double arrester (distribution class) configuration would be the most time and cost effective solution. The alternative of using a single station class arrester is not proposed due to the costs involved and the availability of stock. The understrung conductor arrangement did significantly reduce the energy absorbed by the arresters but due to high labour costs and time requirements this would not be recommended for existing networks. It is suggested that Eskom investigate this practical method for new lines to be built in high lightning areas. Even with arresters from different manufacturers, the use of the double arrester configuration would decrease the energy absorbed and hence reduce the risk of failure of the individual arresters protecting the transformer. This means that Eskom field staff can use different manufacturer arresters in parallel. This would be especially for times when replacing failed arresters or a faulty transformer under breakdown conditions and electrical supply has to be restored to the customer as soon as possible. It was proposed to perform arrester matching by ensuring that the both arresters were from the same manufacturer. / Thesis (M.Sc.Eng)-University of Natal, Durban, 2002.

An ad hoc network is a multi-hop wireless network in which mobile nodes communicate over a shared wireless channel. The network is formed cooperatively without specific user administration or configuration and is characterised by a distributed network management system and the absence of a wired backbone. Military, law enforcement, and disaster relief operations are often carried out in situations with no pre-existing network infrastructure and can benefit from such networks because base stations, which are single points of failure, are undesirable from a reliability standpoint. The rising popularity of mobile computing has also created a potentially large commercial market for multimedia applications applied over wireless ad hoc networks. This dissertation focuses on the routing aspects of ad hoc networking. The multi-hop routes between nodes constantly change as the mobile nodes migrate. Ad hoc network routing algorithms must therefore adapt to the dynamic and unpredictable topology changes, the random radio propagation conditions and portable power sources. Various routing protocols have been proposed in the literature for ad hoc networks. These protocols together with comparative simulations are discussed and a new protocol based on load balancing and signal quality determination is proposed . and the simulation results are presented. Currently the proposed routing protocols are compared using simulation packages which are often time consuming. This dissertation proposes a mathematical model for evaluating the routing protocols and the resultant end-to-end blocking probabilities. The mathematical model is based on a derivation of the reduced load approximation for analysing networks modelled as loss networks and the evaluation incorporates and adapts models that have been used for the analysis of cellular Code Division Multiple Access (CDMA) systems. While analytical methods of solving blocking probability can potentially generate results orders of magnitude faster than simulation, they are more importantly essential to network sensitivity analysis, design and optimisation. / Thesis (M.Sc.Eng.)-University of Natal, Durban, 2003.

The power transfer capability of a transmission line is determined by the magnitude of the voltage at each end of the line, angle difference of these voltages and the impedance of the line. This impedance is mainly inductive. Traditionally, fixed series capacitor banks have been used for series compensation. However, due to instability problems associated with loading transmission line close to their thermal limits, researchers have looked at other alternatives to line compensation by static devices such as fixed series capacitors. Flexible AC Transmission Systems (FACTS) has allowed power utilities to use existing transmission line networks close to their thermal limits without compromising stability of the power system. A FACTS series compensator is capable of influencing the transmission of power in a transmission line by dynamic control of the series compensating reactance inserted in the line. There are several different devices under the FACTS family, however, in this thesis only the Thyristor-Controlled Series Capacitor (TCSC) was considered. A TCSC comprises a fixed capacitor in parallel with a thyristor-controlled reactor (TCR). By varying the firing angle ex:. of the thyristors, the TCSC can be made to act in variable inductive or capacitive reactance mode. The thesis' overall objective was to design a practical TCSC for use in a research laboratory for further research initiatives. This thesis looks at different issues that need to be considered when designing and rating a TCSC compensator. In particular, the thesis examines the effects of different sizes of TCSC components on the rating of the device, the effects of harmonics on the TCSC ratings, sizing of TCSC's variable reactance, and the response time of TCSC to a step change in the firing angle. A mathematical model of a TCSC in a single-machine infinite bus (SMIB) system was developed and subsequently used in the initial design of the TCSC. Studies that were done using mathematical model of the TCSC module confirmed the ability of the TCSC controller to dynamically control the capacitive compensating reactance in the transmission line. The thesis then describes the development of a laboratory-scale TCSC for research investigations. Measured results from the laboratory demonstrate the ability of the TCSC series compensator to provide rapid control of series reactance of a transmission line. A detailed mathematical model of the SMIB equipped with TCSC module was developed, using parameter values of the laboratory scale prototype, to investigate power oscillation damping. Time-domain simulation results are presented in this thesis to demonstrate its ability to damp power swings in an electrical network. / Thesis (M.Sc.Eng.)-University of Natal, Durban, 2003.

This thesis aims to verify the use of quantitative feedback theory (QFT) as a viable tool for designing power system stabilisers (PSS) for a single machine infinite bus system. The result of the QFT design is verified by simulation of the linear and nonlinear models representing the power system, and also by experimental procedures carried out in a laboratory. QFT falls into the classical control category, and is a frequency domain design method. It is an alternative to other design methods such as root locus and Hoo . The QFT design procedure can be extended to a multimachine system and QFT designs of MIMO systems has gained impetus. From theory, through simulation, and to the final laboratory testing on a single machine, infinite bus system, it will be shown that the application of QFT to robust PSS design does indeed work. QFT is a design method that allows the designer to choose a set of realistic operating points and to produce a design that include those points. Other methods allow the designer to produce a design for single operating point, and one has no idea how the design performs at the other operating points. / Thesis (M.Sc.Eng.)-University of Natal, Durban, 2003.

The thesis discusses the findings of an investigation into the use of novel condition monitoring techniques for oil-paper insulated high voltage equipment as used on the Eskom Main Transmission System. This research into the monitoring of the condition of high voltage (RV) insulation was undertaken because of the high failure rate of high voltage current transformers (eT's) and transformer bushings on the Eskom Transmission National Grid. These failures reached unacceptably high levels in the 1990's. The extent of failures has been quantified and was the driving motivation behind this research. Techniques for the condition assessment and condition monitoring of oil-paper filled high voltage equipment have traditionally focused on off-line techniques, in particular off-line tan delta measurements. This requires that the equipment be removed from service temporarily, but at widely spaced intervals before a measurement may be taken (typically every 3 to 6 years). Such techniques will not be able to detect faulty equipment where the insulation integrity deteriorates rapidly, resulting in catastrophic failure with risk to both adjoining equipment and personnel. The need for an on-line technique for detecting deteriorating insulation prior to failure was identified in the early 1990's and various systems were developed. This research investigation has focussed on assessing the use of on-line relative tan delta monitoring of RV insulation and compares this to off-line monitoring. In particular, the ability of such a relative tan delta measurement system to detect deteriorating oil-paper insulation has been assessed. The investigation has included the design, construction and commissioning of a dedicated test facility located at Eskom's Tugela substation. This test facility is unique in the world. This test facility has resulted in a number of experiments that have provided invaluable insight into possible failure modes of oil-filled high voltage equipment and the ability of on-line techniques to detect rapid failure modes has been carefully assessed. Further assessment of the on-line monitoring systems was also undertaken at various Eskom operational installations. The results of these tests and operational monitoring are addressed in this research. The research work and its findings are assessed against published literature and global activity in this important area. / Thesis (M.Sc.-Eng.)-University of KwaZulu-Natal, Durban, 2004.