Ulrich Minnaar

The aim of this report is to: 1) Provide a basic overview of how electricity is transmitted and distributed to assist someone who is not involved with the delivery of electricity to customers to engage meaningfully with the subject matter; 2) Describe the embedded nature of electricity customers connected to distribution networks and the limitations it places on how load shedding is executed and; 3) Assess the feasibility of excluding the identified customer categories from load shedding. Additionally, indicative costs for the most common backup generation alternatives to protect these customer categories from load shedding are discussed.

The aim of this report is to: 1) Provide a basic overview of how electricity is transmitted and distributed to assist someone who is not involved with the delivery of electricity to customers to engage meaningfully with the subject matter; 2) Describe the embedded nature of electricity customers connected to distribution networks and the limitations it places on how load shedding is executed and; 3) Assess the feasibility of excluding the identified customer categories from load shedding. Additionally, indicative costs for the most common backup generation alternatives to protect these customer categories from load shedding are discussed.

This article provides a benchmark of Eskom's costs in relation to international electricity prices by reviewing some available literature and data on international electricity prices and placing Eskom's current prices in context with international electricity prices.

This paper investigates the impact of traction load harmonic current emissions on the harmonic assessment of renewable power plants. Power flow analog data and field measurements taken from PQ recorders were used to identify periods of locomotive activity on the network. A statistical method is presented to assign harmonic current contributions of RPPs and traction loads which are integrated on a distribution traction network. A harmonic emissions assessment of the RPP is done after the exclusion of the background harmonics generated by traction loads. The investigation results show that traction load harmonic emissions can have a significant impact on the harmonic assessment and that a one point measurement approach will not always provide an adequate harmonic assessment on a network with multiple harmonic sources.

Large-scale renewable power producing plants are being integrated into South African networks. Network operators need to ensure that Renewable Power Plants (RPP) do not negatively affect the power quality levels of their networks, as harmonics amongst others could become a concern. IEC 61000-3-6 details a method for allocating voltage harmonic emission limits for distorting loads. This method works well for the allocation of emission limits; however it does not address the management of harmonic emissions once a plant is connected to the network. The management of harmonic emissions requires that network operators measure or quantify the emissions from loads and generators to determine compliance. Post-connection quantification of harmonic levels and compliance is a challenge for network operators. The question asked is “How should a network operator measure/quantify the harmonic emissions of a load/generator to establish compliance with the calculated limits as per IEC 61000-3-6”. ...

iv CONTENTS v LIST OF FIGURES viii LIST OF TABLES x ACRONYMS xii 1. INTRODUCTION 1 1.1 Improving Transmission Reliability 2 1.2 Objective and Research Hypothesis 3 1.3 Thesis Structure 4 2. CAUSES OF TRANSMISSION LINE FAULTS 6 2.1 Characteristics of Major Fault Causes 8 2.2 Waveform Characterisation for Event Classification 17 2.3 Statistical Pattern Recognition and Classification 22 2.4 Classification of Power System Events 24 Fred Nicolls 14/2/27 5:36 PM Deleted: 5

Power quality on South Africa’s low voltage networks is largely unmonitored and not well understood. Regulatory requirements in South Africa requires utilities to monitor power quality at every 1 in 20 000 customers. Smart grids and smart metering is an ever-evolving field with the number of smart meters rising rapidly. This paper introduces the concept of monitoring power quality parameters on the low voltage networks using smart meters. Utilizing smart meters to monitor power quality on low voltage networks will allow utilities to comply with regulatory requirements in a cost-effective way. In this paper an experimental meter is used to evaluate the capabilities of smart meters to perform Fourier transforms on voltage and current to calculate harmonics. Experimental results prove this capability.

South Africa has introduced renewable energy generation to its grid by means of a competitive bidding process. This has been successful as it has quickly introduced renewable generation and has reduced the cost generation significantly over the three rounds of bids submitted. The introduction of distributed renewable generation has consequences for the operation and regulation of its Distribution networks. This paper reviews international practices to establish the cost and benefits of distributed generation to Distribution System Operators as well as regulatory rules that affect them. Impact studies for several European Distribution System operators are discussed and the main impacts of Distributed Generation on Distribution networks are identified as being voltage rise, increased fault levels, losses, reduced power flows upstream and the deferral of investments. Regulation of renewable generation in South Africa is compared with a range of European countries. South Africa has implemented a shallowish network charge regime for distributed generators. This lowers costs for generators connecting to the network, however this has introduced the risk of projects being unable to connect due to deep transmission networks that require funding.

This paper investigates the characterization of voltage dips with aim of selecting suitable feature extraction tools for the analysis of events. The symmetrical component method, ABC classification and the voltage dip segmentation method are discussed and a list of characteristics identified. Signal processing tools are reviewed and the Kalman filter and Ziarani algorithm selected as suitable feature extraction tools based on the analysis requirements of the dip segmentation method.

... 74 10.4.2 Implementation and Development Issues 74 ... A load topology is proposed with supporting theory. The introduction of a programmable load to the PQ Testlab will enhance ... torque is Nm. • Speed is the rotational velocity of the driving shaft. It is measured in ...

The performance of variable electricity generation sources such as solar PV and wind is an important consideration in their integration into a power system. The expected performance may affect a number of decisions related to network planning, tariff determinations, energy planning as well as future policy decisions. This study analyses the capacity factor performance of utility scale solar PV and wind on the South African power system. Measures of capacity factor relative to electricity demand are considered and performance is assessed during Eskom's seasonal peak and off-peak demand periods.

In 2016, NERSA approved a Cost of Unserved Energy methodology as stipulated by the requirements of both the Transmission and Distribution Grid Codes. The methodology utilises a macroeconomic method to provide Cost of Unserved Energy values across a range of economic sectors as well as the residential sector. The development of a COUE methodology based on macroeconomic principles and data provides a basis for investment decision-making in South Africa's power system which is consistent with the macroeconomic considerations used in national planning decisions. NERSA has proposed that the COUE model be used as a basis for COUE for all licensed distributors in South Africa as 1) it is based on a model that has been tested and accepted by NERSA 2) it relieves the need for municipalities having to develop complex economic models and 3) it provides a common basis for economic decision-making across the power system supply chain in South Africa.

The power quality requirements for RPPs created significant debate when the first RPPs started connecting to the grid. The purpose of this paper is to capture some of the debates around the harmonic emission limits and assessment methods as well as the resulting update to the RPP grid code.

Cost of unserved energy provides an economic measure of the cost of electricity interruptions to electricity customers. These values inform investment and refurbishment decisions related to the power system, with the aim of optimizing network reliability. This paper reports on the development of an economic model to estimate the value of electricity reliability in South Africa by Eskom to meet regulatory requirements. The model allows for the scalability of COUE from national level to more detailed resolutions. The impact is that decisions for power system investment can be made to meet the needs of planning and regulatory applications.

The introduction of renewable power plants has introduced challenges to the management and regulation of power quality in South Africa. These challenges have been addressed by establishing power quality compliance criteria in line with local circumstances and by the introduction of a Power Quality Guideline for renewable power plants. South Africa has seen significant growth in renewable energy generation in recent years. The rapid addition of solar PV and wind generation to the South African grid presents challenges to the management and regulation of power quality due to the potential power quality (PQ) impact of these generation technologies. South Africa has a long record of managing and regulating power quality, with the local NRS048-2 standard being one of the first national power quality standards adopted by any country. The standards locally have been primarily focused on the responsibilities of utilities and customers consuming electricity. The power quality regulatory framework in South Africa includes standards guiding utilities on compatibility levels and limits for PQ parameters-NRS048-2, technical practices for network services providers (NSPs)-NRS 048-4, power quality instrument specifications-SABS1816, as well as application practices for customers to deal with power quality on their plant-NRS048-7. None of these standards, however, were developed with renewable generation in mind, additionally the South African Grid Code for Renewable Power Plants (SAGCRPP) [1] stipulates PQ requirements that generators should meet, however, with the connection of the first round of RPPs it became evident that there were challenges relating to 1) the process for proving compliance to PQ requirements and 2) agreement on principles pertaining to calculating and assessing the emissions of these plants. This has resulted in some of these standards being revisited to be inclusive of the role and impact of RPPs on the grid e.g. the revision of NRS048-4: Application guideline for network service providers was done specifically with distributed RPPs in mind and suitable changes made to the document. Local Circumstances The development of power quality rules and compliance requirements is ideally done with local circumstances in mind. Relevant to connecting RPPs in a developing country, such as South Africa, some of these factors include a) limited skills, b) long rural radial feeders with low fault levels and c) aging and under-maintained network infrastructure. Any compliance requirement that is set should keep in mind that it should be practical and feasible to evaluate against these requirements. A second factor informing the development of power quality compliance rules is the need to keep the cost burden to a minimum, so as not to unnecessarily drive up generation costs while simultaneously ensuring that NSP power quality staff are not inundated with a larger number of complex applications which would require significant time and resources to process, ultimately clogging the system and prohibiting generators from connecting to the network or receiving grid code compliance. Meeting these local challenges entailed a process comprising a) defining suitable PQ grid code requirements for generators, b) the development of a guideline to assist RPPs to meet their PQ obligations and c) adaptations to the way network service providers (NSPs) manage PQ in general. Some of the unique challenges for NSPs in managing the contribution to PQ of RPPs in South Africa are: a) The bidding process used in the REIPPP requires that grid code compliance be granted for a 20 year window up front. This means that the NSP carries the risk and mitigation costs should a PQ problem manifest itself during this 20 year window. b) Determining whether RPPs meet their emission limits. The measurement of the emissions contributed by a single source of distortion is a challenge in a real-life power system. With different sources of distortion located all over a network and a continuous changing network configuration, single-point measurements of harmonic active power (for example) cannot be used in the assessment of harmonic emissions contributed by the distorting source under investigation. c) Managing the expected influx of smaller renewable generators on the South African grid. Establishing Power Quality Requirements The specific power quality parameters monitored and regulated may be quite wide ranging and it is common practice internationally for customers and generators to be required to monitor and report on: a) voltage fluctuations-flicker

Cost of Unserved Energy (COUE) is used to provide an economic value to the cost of electricity interruptions to electricity customers and the economy as a whole. These values are used to inform a number of investment and refurbishment decisions on the electrical power system, with the aim of optimising the reliability of the network.

This research demonstrates that transmission line faults can be classified automatically according to their underlying cause, and lays a foundation for operational classification of transmission line faults in system control centres. The transmission line fault waveforms are characterised by instantaneous symmetrical component analysis to describe the transient and steady state fault conditions. Using a large fault record and waveform database, classification features based on the waveform and external environmental characteristics have been identified to develop single-nearest-neighbour classifiers that identify the underlying cause of transmission line faults, and good classification accuracy has been achieved.

South Africa has introduced renewable energy generation to its grid by means of a competitive bidding process. This has been successful as it has quickly introduced renewable generation and has reduced the cost generation significantly over the three rounds of bids submitted.The introduction of distributed
renewable generation has consequences for the operation and regulation of its Distribution networks.
This paper reviews international practices to establish the cost and benefits of distributed generation to Distribution System Operators as well as regulatory rules that affect them. Impact studies for several European Distribution System operators are discussed and the main impacts of Distributed Generation on Distribution networks are identified as being voltage rise, increased fault levels, losses, reduced power flows upstream and the deferral of investments. Regulation of renewable generation in SouthAfrica is compared with a range of European countries. South Africa has implemented a shallowish network
charge regime for distributed generators. This lowers costs for generators connecting to thr network, however this has introduced the risk of projects being unable to connect due to deep transmission networks that require funding.

Large-scale renewable power producing plants are being integrated into South African networks.
Network operators need to ensure that Renewable Power Plants (RPP) do not negatively affect the power quality levels of their networks, as harmonics amongst others could become a concern.
IEC 61000-3-6 details a method for allocating voltage harmonic emission limits for distorting loads.
This method works well for the allocation of emission limits however; it does not address the management of harmonic emissions once a plant is connected to the network. The management of harmonic emissions requires that network operators measure or quantify the emissions from loads and generators to determine compliance. Post-connection quantification of harmonic levels and
compliance is a challenge for network operators. The question asked is: “How should a network
operator measure/quantify the harmonic emissions of a load/generator to establish compliance with the
calculated limits as per IEC 61000-3-6?”
This paper reviews, within a South African context, methods of assessing harmonic emission levels and then evaluates these methods by means of field data. Opportunities for improvement are identified and operational requirements discussed.

Electricity customers in developing countries have different needs to those in developed countries. In particular, in Sub-Saharan Africa only 24% of people have access to electricity. Electricity networks in developing countries are often characterised by thin radial networks, geographically dispersed customers and a lack of generation capacity. These conditions are markedly different from developed nations with high levels of urbanisation, large industrial capacity and high electrical consumption per capita. These varying demands and investment in infrastructure means that different expectations and requirements exist for customers, network operators and regulators. The primary focus of the electricity sector in developing countries such as Sub-Saharan Africa is on the expansion of access to electricity and increased generation. In the context of limited resources to achieve expansion of supply and provide energy for economic expansion the regulation of power quality requires an approach that is adjusted to the varying requirements within these countries. Customers may range from industrial customers to off-grid supplied households who are receiving electricity for the first time. A uniform standard of requirements for such diverse needs is neither desirable nor feasible. This paper reviews approaches in place to regulate power quality in Sub-Saharan Africa and discusses approaches to standardisation, monitoring and regulation of power quality that meets these specific needs.

A country‘s ability to sustain and grow its industrial and commercial activities is highly dependent on a reliable electricity supply. Electrical faults on transmission lines are a cause of both interruptions to supply and voltage dips. These are the most common events impacting electricity users and also have the largest financial impact on them. This research focuses on understanding the causes of transmission line faults and developing methods to automatically identify these causes.
Records of faults occurring on the South African power transmission system over a 16-year period have been collected and analysed to find statistical relationships between local climate, key design parameters of the overhead lines and the main causes of power system faults. The results characterize the performance of the South African transmission system on a probabilistic basis and illustrate differences in fault cause statistics for the summer and winter rainfall areas of South Africa and for different times of the year and day. This analysis lays a foundation for reliability analysis and fault pattern recognition taking environmental features such as local geography, climate and power system parameters into account.
A key aspect of using pattern recognition techniques is selecting appropriate classifying features. Transmission line fault waveforms are characterised by instantaneous symmetrical component analysis to describe the transient and steady state fault conditions. The waveform and environmental features are used to develop single nearest neighbour classifiers to identify the underlying cause of transmission line faults. A classification accuracy of 86% is achieved using a single nearest neighbour classifier. This classification performance is found to be superior to that of decision tree, artificial neural network and naïve Bayes classifiers.
The results achieved demonstrate that transmission line faults can be automatically classified according to cause.

This paper investigates the characterization of voltage dips with aim of selecting suitable feature extraction tools for the analysis of events. The symmetrical component method, ABC classification and the voltage dip segmentation method are discussed and a list of characteristics identified. Signal processing tools are reviewed and the Kalman filter and Ziarani algorithm selected as suitable feature extraction tools based on the analysis requirements of the dip segmentation method.

Eskom as a utility is mandated by its licence conditions to monitor, manage and report on the quality of supply that is being delivered to its customers. This paper aims to give an overview of the evolution of the quality of supply measurement program since its inception in the early 1990’s to the possible direction that it may take into the future.

Specifies product requirements for instruments, the functions of which include measuring and monitoring of power quality parameters in a.c. power systems. Can be used in, for example, the generation, transmission and distribution of electricity and related telecommunication systems, e.g. inside a power station or a substation, or a distributed generator connection, or at the interface point between the installation and the network, e.g. in order to check the compliance to the connection agreement with a network operator.

Voltage dips (also known as “voltage sags”) are short-duration reductions in voltage magnitude. Their
duration is typically between a few cycles of the power-system frequency and a few seconds. The interest in
voltage dips is mainly due to their impact on end-user equipment. Industrial processes may malfunction or
shut down due to a voltage dip resulting in significant financial losses.
Voltage dips are due to short-duration increases in current magnitude, whereas voltage dips due to short circuits and earth faults are of most concern for customers. This report presents the results from an international working group sponsored by CIGRE, CIRED and UIE aimed at improving the understanding of the compatibility between installations and the electricity supply.

Prior to the load-shedding events, customers were fairly used to power interruptions which were primarily caused by lightning or cable theft events. Since these events, many people associate any form of interruption with ‘load-shedding'. This article considers the other event types and their impact on quality of supply; specifically voltage regulation and voltage continuity (more commonly referred to as reliability of the supply).

The Voltage Dip Test Facility at the University of the Witwatersrand utilises a resistive load during testing of variable speed drives. This method produces valuable results regarding the performance of drives under dip conditions. It has been shown that load type does influence the performance of drives and this variation cannot be tested under current conditions as only linear loading is attainable with resistive loads. This thesis proposes a programmable load based on the concept of field-oriented control of an induction motor. The concepts involved with field-oriented control are discussed and shown to be suitable for this application. An implementation strategy utilising custom-designed software and an off-the-shelf VSD is developed and executed. The performance of the programmable load is analysed under both steady-state and dynamic conditions.

This book explains the significance of Power Quality (PQ) or Quality of Supply in the context of today’s electricity supply systems. It begins by exploring the history and technical scope of PQ, how it forms a subset of the broader topic of Electromagnetic Compatibility, and how and why it has developed into a distinct technical discipline during the past 20 to 25 years. The theoretical aspects of a given technical component of PQ are introduced in the main body of the book in dedicated chapters; in each case, the experience gained (by Eskom) is then used to illustrate how the principles of PQ are being effectively applied in modern electric networks.

The book encapsulates the knowledge and unique insights gained by Eskom over the years during the implementation of a comprehensive PQ measurement survey. The objectives of the survey were firstly, to determine the levels of PQ being attained, and secondly, to establish how the results could be used to set realistic design and performance criteria for each component of PQ. Key drivers in the evolvement of PQ into a discipline include the increased sensitivity of customer equipment to deleterious electrical effects, the need for operational efficiency, the move to privatise utilities, and increasingly tight regulatory requirements in many countries.

The formal integration of PQ by means of the standardisation of limits for voltage fluctuations (which comprise primarily voltage surges, voltage regulation, dips, notches, flicker, harmonics, unbalance) and frequency control as the key components of PQ, has greatly helped to consolidate PQ as a stand-alone discipline in today’s power utility. By elaborating on the foregoing aspects, this book will thus be useful to a diverse spectrum of persons, including specialist practitioners, grid planners, consultants, academics, power utility managers and regulatory authorities.​