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Enhancing Urban Resilience to Electricity Disruptions

The Case of Kisumu Central Sub–County, Kenya

Presentation / Essay (Pre-University) 2017 49 Pages

Geography / Earth Science - Demographics, Urban Management, Planning

Excerpt

Table of Content

1 Introduction
1.1 Problem Statement
1.2 Research Objectives and Questions
1.3 Significance of the Research Study

2 Measuring Urban Resilience to Electricity Disruptions
2.1 The Sociotechnical and Socioecological Aspects of Urban Resilience
2.1.1 Sociotechnical Resilience
2.1.2 Socioecological Resilience

3 Research Design, Methods and Data
3.1 Research Design
3.2 Case Study Design
3.3 Data Collection
3.3.1 Quantitative Data
3.3.2 Qualitative Data – Semi–structured Expert Interviews
3.4 Sampling

4 References

Appendix 1

Appendix 2

1 Introduction

When Thomas Edison came up with the first electric utility system, in 1879, his intention was to compete against gas for customers. The idea at the time was to make electricity a commercial alternative for the energy historically provided by gas, steam, hydraulics, direct heating and cooling, and light.[1] Two centuries later, electricity has become an integral part of human society; it drives sociotechnical and economic developments while wielding the ability to destroy human society – without it, life comes to a grinding halt, while a slight excess of the same can lead to wanton destruction of valuable property and loss of lives. It is the quality of electricity that determines whether electricity will sustain or destroy property and life.

Ideally, a.c. voltage should always be supplied via a resistance free distribution network, as a perfect sinusoidal wave, with an amplitude and frequency that is either preset by (inter)national standards or system specifications.[2] Unfortunately, this is hardly ever the case, in real life that is. This reality can be attributed to the fact that all vertically integrated traditional powers systems (consisting of generation, transmission, distribution and, retail sub–systems) are always exposed to disturbances. Disturbances, regardless of whether they emanate from within or without the power grid, cause power quality problems (or electricity disruptions as is the preferred expression in this study). For example, a blackout, a type of quality problem, is likely to be experienced in the events that flash floods, strong winds, or landslides bring down a transformer; a power surge, also a power quality problem, is likely to be experienced when lightning strikes or when a rodent gets into a transformer. All types of electricity disruptions, no matter how minute, are hazardous. For example, power surges can fry every piece of equipment connected to the power line, plastics included, and have been known to cause destructive fires while power outages can lead to heavy economic losses.[3]

1.1 Problem Statement

Most Kenyans have at one point or another experienced a power disruption of some sort; with those who have yet to, probably being among the many Kenyans who either still depend on biomass (e.g. firewood, charcoal and agricultural wastes) or use it as a substitute for expensive electricity. These include rural communities, the urban poor, and the informal sector. As of 2014/15, Kenya relied on biomass (68%), hydrocarbons (22%), electricity (9%), solar and other forms of energy (1%) for its energy needs with petroleum and electricity dominating commercial energy. Poverty is the main reason behind this high reliance on biomass, instead of clean electricity. Appendix 1 gives an overview of Kenya’s energy trends, from generation capacity, number of consumers, demand, cost, all the way to reliability and quality of the supplied electricity, for the period starting 2010/11 to 2014/15.

Regardless, Kenya has seen an increase in demand for electricity, especially in the last couple of years. For instance, this demand increased from a peak value of 1,443MW in Jul 2014 to 1,512MW in Jun 2015. According to the Energy Regulatory Commission (ERC), this observed increase in demand, albeit meagre, can be attributed to: “a combination of normal growth, increased connections in urban and rural areas as well as the country’s envisaged transformation into a newly industrialized country as articulated in Vision 2030.”[4] The ERC expects this demand to continue growing at an annual rate of 11%, shooting to 2,834MW by 2020 and continuing along the same trajectory for the foreseeable future. ERC attributes this forecast to the country’s projected growth in population, urbanization and GDP.

While the demand for electricity has been increasing, so has its supply. For example, as of July 2014, Kenya had an installed electricity generation capacity of 1,665MW. Come Jun 2015, this nominal generation capacity had increased to 2,299MW (38.07%), 2,234MW (97.18%) of which was grid–connected i.e. effective capacity. This wide gap, between what is supplied and what is actually being consumed, also contributes towards the many electricity disruptions.[5]

The other factor contributing towards the frequent electricity disruptions in Kenya has to do with hydro being a major contributor to the country’s electric capacity. The generated electricity as of Jun 2015 comprised of thermal (827MW), hydro (821MW), geothermal (598MW), co–generation (26MW), wind (25.5MW), and solar (0.57MW). Since hydro accounts for a large percentage of this capacity and is reliant on unpredictable weather conditions, the result is a high frequency of power outages experienced by Kenyans, 33% (compared to an average of 1% for Mexico, China and South Africa).

Furthermore, though it may appear as if the supplied electricity by far exceeds the demand, the country’s electric power market still remains unbalanced i.e., the supplied electricity has yet to fully satiate the actual demand. This is so because as of Jun 2015, there were only 3,614,744 electricity consumers connected to the national grid, less than 10% of the population. This number stood at 907,795 in Jul 2014 and was much lower in the previous years. Illegal connections are inevitable in a situation where millions of potential consumers find themselves locked out of the national power grid. Couple this high demand with the high cost of electricity and electricity disruptions, especially in urban sprawls, become a near everyday occurrence.[6]

Take Kisumu city for instance, where the Kenya Power and Lighting Company (KPLC) rarely fails to nab individuals whenever it cracks down on unauthorized power connections to clean up its network. At times, those who get arrested include employees from KPLC itself. It is not uncommon for KPLC to carry out such operations considering that the country’s entire distribution network, which stood at 78,907km as at Jun 2015, is under it. This distribution network consists of 66KV feeder lines around Nairobi and 33KV and 11KV medium–voltage lines distributed throughout the country.[7]

According to the 2013 Distribution Master Plan Report, prepared by Parsons Brinckerhoff for Kenya Power and Lighting Company (KPLC), there were 10 132/33 kV bulk supply points (BSPs) in the entire Western region (which included the major urban areas of Kisumu, Nakuru and Eldoret) relying on only one 132 kV transmission system. The Western region’s 33 kV network comprised of 52 radial feeders, 71 primary substations and approximately 2000 33/0.4kV distribution transformers. Prior to 2017, the Kisumu 132/33 kV BSP supplied all the primary substations in Kisumu County, including the two 33/11 kV primary substations at Kisumu East and Obote Road feeding Kisumu city’s entire 11 kV network. Realizing that these substations would exceed their N–1 capacity come 2018, Parsons Brinckerhoff proposed the creation of another 33/11 kV primary substation in the city. Like all the others before it, this new substation would be supplied from the Kisumu BSP but with an alternative feed, still from Kisumu BSP, for security of supply during outages. But even before this could happen, the 7.5 MVA transformer at Obote Road 33/11 kV substation was expected to exceed 100% of its rated capacity by the end of 2012. At the time, the Obote Road substation configuration was two 33/11 kV transformers rated 1x23 MVA and 1x7.5 MVA; which meant that this had to be reconfigured to 2x23 MVA.[8] The Kisumu East 33/11 kV substation is situated along the KisumuAhero road about 3 km from Kisumu city. Its 2x23 MVA transformers supply Kano, Dunga and Milimani areas. The Obote Road 33/11kV substation is situated along the KisumuBusia highway, within Kisumu city. One of its 33/11 kV transformers feeds 11 kV transformers located in the CBD, Industrial area, Mamboleo, and at Prestige House. The same also supplies a ring feeder and a circuit protective conductor (CPC). The other 33/11 kV transformer supplies 11 kV transformers located near Jaramogi Oginga Odinga Teaching and Referral Hospital, Kisumu International Airport, Kondele, Pipeline, Sabuni Road, and another CPC.[9]

This study focuses on Kisumu’s electricity distribution network for several reasons but mainly so because:

1. it is one of the city’s most critical infrastructures that often gets affected whenever disasters, both acute and chronic, strike

Blackouts and power surges, to name but a few, are some of the challenges Kisumu residents, especially the poor, experience frequently. Unfortunately, it is only when floods and other catastrophes strike that these near everyday occurrences get media coverage.

2. the effects emanating from all manners of electricity disruptions, be they planned or unplanned, often have the adverse effect of affecting, both directly and indirectly, the physical, environmental, social, and economic aspects of the city and Kenya at large.

Incidences of children being electrocuted to death are common in the city, especially in slums like Manyatta, Nyalenda and Kondele, which are notorious for their vast networks of illegal power connections. In 2014, when the KPLC took note of the city’s electricity linked challenges, it launched a KES 100 million (approx. USD 1 million) project dubbed Operation Boresha Umeme [Improve Electricity] Kisumu. Through this project, which commenced on 12 Jul 2014, the KPLC aimed to improve the town’s power supply system and minimize its power outages. To accomplish this fete, in a span of two days as was intended, the KPLC marshalled over 700 of its staff members who went on to carry out master repair works on existing power substations in Kisumu and its environs; extend power networks; create additional transformation and distribution capacities to cater for critical services such as hospitals; construct four new dedicated lines to serve Kisumu’s Central Business District, Industrial Area, Nyahera, and Manyatta estates and; install 12 new while refurbishing 50 existing transformers to enhance their performance and prevent technical breakdowns.[10]

Regardless, just a month following KPLC ’s initiative, on 20 Aug 2014 to be precise, a three year old girl was electrocuted to death, in Nyalenda slums, after touching a barbed wire fence, not knowing that a live wire was in contact with the metallic hedge. This happened as she went about playing outside her parents’ house.[11] Then on the night of 20 Dec the same year, when torrential rains descended on the city, a loose electric cable electrocuted a little boy, killing him on the spot.[12] The heavy rains also rendered hundreds of Kisumu residents homeless with many more being left to endure several nights in the dark courtesy of the raging floods destroying parts of the city’s power distribution network. More recently, between 1 Jan and 18 May 2017, Manyatta estate alone, lost four of its residents to electrocutions, including a little boy who perished while his mother got electrocuted as she struggled to rescue him.[13] What these incidences serve to show is that without the results of a well–structured and properly conducted research study, it would be challenging to empirically tell whether or not Operation Boresha Umeme Kisumu accomplish its objective, or not; and by how much.

1.2 Research Objectives and Questions

The overall objective of this research is to generate empirical findings that establish the resilience of Kisumu city to electric disruptions and how this can be enhanced. Thus, in order to realize this objective, the following primary research question is posed:

How can the resilience of Kisumu city to electricity disruptions be enhanced?

The research’s main objective is divided further into three key sub–objective: 1) establishing the resilience of Kisumu’s Electricity distribution network; 2) establishing the vulnerability of Kisumu city residents to the impacts of electricity disruptions and; 3) how this can be enhanced. From these two sub–objectives, the following sub–questions are derived:

1. How resilient is Kisumu’s electricity distribution network to disruptions?
This is a compound question in that it seeks to answer the following sub–sub–questions:
1.1. What power quality problems affect the city’s distribution network e.g., blackouts, overvoltages, sags etc.?
1.2. How often does each type of power quality problem occur?
1.3. How long does each power quality problem last when it occurs?
1.4. What is the nature of the relationship between the occurrence of each power quality problem and the time of its occurrence (day/night, month)?
1.5. What is the nature of the relationship between the occurrence of each power quality problem and the prevalent weather conditions (rain, temperature, humidity) at the time?
1.6. How frequently do different neighbourhoods experience the different power quality problems?

2. What causes electricity disruptions in Kisumu city?

This involves identifying factors that contribute towards lowering the quality of electricity distributed in the city (make the city’s power distribution network susceptible to disruptions). These can be classified into physical, social, economic, environmental, institutional and human factors.

3. How vulnerable are Kisumu city residents to the impacts of electricity disruptions?

This sub–question requires the use of different indicators to quantify the several aspects of vulnerability i.e.:

3.1. multidimensional (defined by physical, social, economic, environmental, institutional and human factors);

3.2. dynamic (changes over time);

3.3. scale dependent (can be expressed at different scales from human to household to community to country resolution) and;

3.4. site specific (varies from one location to the next)

4. What strategic actions (mitigation) should be adopted in order to enhance the city’s resilience to electricity disruptions ?

This seeks to first identify the challenges stakeholders encounter while striving to enhance their individual, and the city’s overall, resilience against electricity disruptions. For the most part, answers to this sub–question will be informed by answers to the previous sub–question. The second part will involve proposing resiliency measures based on inputs from power distributors, the county administration, and consumers (both industrial and residential).

1.3 Significance of the Research Study

The findings of this study will redound to the benefit of society considering how important electricity is to contemporary society. The global urgency to mitigate against climate change, by replacing biogas and fossil fuels, justifies the need to have resilient electric power grid systems. Additionally, the risks posed by the high and ever increasing demand for clean electricity, in the rapidly urbanizing human settlements found in developing economies, adds further credence to the importance of this study. It is important to grasp the resilience of Kisumu city to electricity disruptions not only because it is one such rapidly urbanizing city; but it is also one of the oldest, hence historically significant. Furthermore, of Kenya’s three major cities (others being Nairobi and Mombasa), Kisumu is the one situated in the most strategic location when it comes to Kenya’s relations with other East African nations. Therefore, Kisumu’s resilience to electricity disruption is also important to East Africa’s social and economic development; and a matter of national security for Kenya. The findings of this research will also enable the ERC, KPLC, the county and national governments to institute disaster mitigation and response mechanisms that would minimize the loss of or damage to lives, livelihoods, property, infrastructure, economic activity and the environment in the event of power disruptions. This research also aims to ensure that disaster relief, response, and humanitarian institutions have a clearer grasp on the realities of electricity disruptions within major cities. To researchers, the findings of this research will inform sustainable and resilience oriented urban planning debates and activities within East Africa with the potential of being replicated in rapidly urbanizing cities in other developing regions. Hence, it can act as a blueprint for research activities that intend to adopt the methodology applied herein or want to come up with more robust and comprehensive frameworks for studying the resilience of critical urban infrastructures and communities.

2 Measuring Urban Resilience to Electricity Disruptions

In attempting to define urban resilience, Sara Meerow, Joshua Newell, and Melissa Stults reviewed 25 definitions of the concept, from the different publications in which they appeared. From these, they observed “that urban resilience is a contested concept and lacks clarity due to inconsistencies and ambiguity.” The many definition of the concept, they asserted, could be attributed to, “the challenges associated with defining and characterizing “urban” and “resilience” individually, and the numerous disciplines engaged in this field of study”. The problem with having multiple definitions of the same concept is that these lead to conceptual tensions. When it comes to the definition of urban resilience, the six conceptual tensions identified by the authors were: 1) characterization of urban; 2) notion of equilibrium; 3) resilience as a positive concept; 4) pathway to resilience; 5) understanding of adaptation and; 6) timescale of action. A proper definition of urban resilience, they asserted, should at the least attempt to incorporate these conceptual tensions (or take an explicit stance against them). This proper definition should also ensure that it does so in a flexible and inclusive way so as to allow different perspectives and emphases to flourish. Unfortunately, a majority of the 25 definitions reviewed failed to take a clear position on at least one of these six conceptual tensions. In the end, the trio resorted to defining urban resilience as thus:

Urban resilience refers to the ability of an urban system – and all its constituent socio–ecological and socio–technical networks across temporal and spatial scales – to maintain or rapidly return to desired functions in the face of a disturbance, to adapt to change, and to quickly transform systems that limit current or future adaptive capacity. [14]

This definition is worded in a manner to articulate a position on each of the six conceptual tensions: 1) an urban system is characterized by two systems – a) socioecological and; b) sociotechnical networks, across temporal and spatial scales; 2) the notion of equilibrium is to maintain a desired state in the face of a disturbance; 3) resilience is a positive concept which involves returning to a desired state, albeit different from the original one, in the face of a disturbance; 4) the pathway to resilience entails adapting to change, transforming systems, and capacity building, and; 6) “quickly” is the timescale of action.

2.1 The Sociotechnical and Socioecological Aspects of Urban Resilience

The integrated definition of urban resilience implies that the resilience of cities should always be viewed as being determined by the interplay between the different types of networks across spatial and temporal scales, including the social networks that create and maintain technical networks.[15] In other words, urban resilience, UR should be regarded as being a function of socioecological (SER) and sociotechnical (STR) resilience.[16] Mathematically, this relationship, between UR, SER and STR can be expressed as thus:

Though both perceive resilience as the ability to maintain system structure and function in the face of both shocks (short term disruptions) and stresses (long term), they differ in the following respects. 1) Sociotechnical regimes are not as place–bound as socioecological systems. 2) While the objective of socioecological research is to support the resilience existing in desired systems, or transform such systems into more desirable states, sociotechnical research usually focuses on explaining and doing away with negative resilience and faulty systems all together. 3) Structures are regarded as being synonymous with functions in socioecological resilience while sociotechnical research acknowledges that functional sustainability is best achieved through structural transformation, intrinsically making a clear distinction between the two and. 4) Socioecological resilience conflates responses to shock and stress while sociotechnical resilience makes systematic discriminations between them.[17] Consequent to these contrasts, different approaches, employing different tools, are required to measure them separately.

For starters, the concept of sociotechnical systems stresses the reciprocal relationship between humans and technology – social processes shape the development and use of technology while technology opens up possibilities for new social practices. In the urban context, sociotechnical resilience can be perceived as the degree to which artificial structures can survive shocks. The focus here is on the hazards and their impacts; measured using an engineering or a technology–based approach. For example, the System Average Interruption Duration Index (SAIDI) is often used to measure the resilience of an electricity system to power outages. SAIDI is calculated by taking the total number of customer–minutes of lost power and dividing this with the total number of customers. That being the case, SAIDI will not be adopted for this research. Instead, an integrated engineering resilience approach will be used to establish the resilience of Kisumu’s electricity distribution system.

The socioecological concept on the other end emphasises how humans rely on and influence the ecosystem as it influences them back. Consequently, socioecological resilience measures how well members of a community cope with the effects of ecological related disruptions e.g., floods, earthquakes etc. The focus here is on vulnerability, to be measured using a community based approach. Therefore, to empirically ascertain the vulnerability of Kisumu city residents to the impacts of electricity disruptions, an Integrated Vulnerability and Risk Assessment Model will be used.

Another point worth noting is that these two variables are mutually reinforcing – they influence one another but how and by how much, is at this point a matter of intellectual speculation. Even so, consider these two situations

1. High sociotechnical, low socioecological resilience: a city is highly vulnerable to acute shocks when it is made up of sound structures, but its foundation is set on weak social capital. This is so because in times of stress, people naturally retreat back to their social groups i.e., places where they feel at home. These include families, friends, religious communities etc. While this is happening, the other bridging links – the city’s lifelines (e.g. economic, political, etc.) – suffer. It takes time to reestablish these bonds, an aspect that depends on how deep the city’s social bonds run – the deeper the connections, the faster these get restored and vice versa. Therefore, a city with weak socioecological ties will likely have a hard time readjusting to unexpected shocks. Nevertheless, low socioecological resilience in a technically resilient city does not necessarily translate into doom in the event of a disaster, it however means a longer reorganization period.

2. High socioecological, low sociotechnical resilience: a city made of unsound structures is still vulnerable to shocks regardless of how strong its social bonds may be. Structures that are vulnerable to disasters are hazardous because when disasters strike, it is these very same structures that end up killing, maiming, and destroying the lives of city dwellers. The effects of low sociotechnical resilience, in a city with high socioecological resilience, often manifest themselves immediately when a disaster strikes. These carry on into the recovery phase and might even spell doom for the city in the long run.

2.1.1 Sociotechnical Resilience

The object of resilience in sociotechnical research can either be one of two things: 1) structure – the level of decline and consequent susceptibility of a structure to transformation or; 2) function – the ability of a structure to maintain requisite levels of functionality when subjected to either a shock or stress.[18] Since the focus is on measuring the quality of electricity supplied by Kisumu’s electricity distribution network, and not its level of decline after being exposed to a series of shocks and stresses, then function is the object of this research. This will be measured using an integrated engineering resilience (IER) approach.

The IER was first proposed in a Discussion Paper on Risk and Uncertainty Modeling in Energy Systems. The paper was as a result of discussions at a NATO Advanced Network Workshop “Resilience–Based Approaches to Critical Infrastructure Safeguarding”, held in Ponta Delgada, from 26 to 29 Jun 2016. The IER builds on research work conducted at the Reliability and Risk Engineering Laboratory, ETH Zurich. In the IER approach, relevant aspects that determine a system’s performance during and after a disruption are quantified, measured, and then combined into one metric resilience factor, IER.[19]

By first establishing what any electricity network is expected to do, one can compile a list of appropriate indicators to measures its performance. For example, the main purpose of any power network is to power electrical equipment, be they at home or elsewhere. But the network’s ability to power electric equipment is just one part, the other, even more crucial aspect, is concerned with the quality of supplied electricity. Power quality encompasses voltage, frequency, and waveform. Theoretically, good electric power quality means that the supplied voltage is steady and within the prescribed range; that the a.c. frequency is also steady and within a fraction of a percent to its nominal value; and that the shape of the voltage curve versus time resembles a smooth sine wave (no distortions). In practice, however, owing to exposure of the electric grid and its consequent susceptibility to disruptions, Alexandra von Meier advises that it would be practical to consider electric power quality as a measure of compatibility between what comes out of an electric outlet and the load (e.g. bulb, electronic, machine etc.) that is plugged into it.[20] In other words, the quality of electricity is a description of how properly a connected load functions. These loads are usually connected to the power grid via the electricity distribution system, a vital infrastructure which carries electricity from the transmission system to the consumers.[21] What this implies is that the overall quality of electricity flowing through any power grid, can be determined from the voltage, frequency, and sinusoidal characteristics of electricity captured in the distribution section of the power network.

2.1.1.1 Types of Power Quality Deviations

The supply voltage varies along with power flows in the transmission and especially the distribution system – as consumption and thus line current increases, there is an increasing voltage drop along the power lines according to Ohm’s law. This means that the difference between the voltage supplied at the generation end and that injected into a given load varies continuously depending on demand, both system–wide and local.[22] Unfortunately, even though suppliers may attempt to correct for this variance, at least at the distribution level, they cannot do so perfectly. Therefore, the traditional norm has always been to work within the standards set by the International Electrotechnical Commission (IEC).

According to the IEC, the supply terminals voltage [23] should not differ from the nominal voltage[24] of the system by more than . It is also important to note that voltage drops measured at the supply terminal may occur within the loads themselves. For low–voltage installations like voltmeters, the IEC advices that this value should always be limited to 4 % of the nominal voltage. Therefore, at the end of the transition period, a utilization voltage range of should be factored into the equation in order to determine the true nominal voltage of the electricity distribution system. For a.c. transmission, distribution and utilization systems with standard frequencies 50 Hz and 60 Hz, this nominal voltages should be 120/240 V for single–phase three–wire systems. Here, the lower value, 120 V, is the voltage between a live and neutral terminal; while the higher value, 240 V, is the voltage between two live lines.[25]

Overvoltage is a condition that occurs when this supply voltage rises above the nominal voltage by 110% for more than 1 minute. Overvoltage can be caused by switching off a large load, switching on a capacitor bank, a weak system, or inadequate controls in the electrical system. Undervoltage occurs when the supply voltage drops below the nominal voltage by 90% for more than 1 minute. Undervoltage can be caused by switching on a heavy load, switching off a capacitor bank, overloaded circuits, and loss of a major distribution line. Voltage fluctuations (also flicker) is a situation where the supply voltage keeps on oscillating, be it randomly or periodically, between 90% and 100% of the nominal voltage. Power outages (blackouts) are also a power quality problem that occur when there is zero supply voltage.

Beyond the nominal voltage, of concern in power quality is also voltage swells; experienced when the supply voltage exceeds the nominal voltage by 10% to 80% for 0.5 cycle to 1 minute. Voltage swell that last for microseconds are often referred to as impulses or spikes and while those that span over a millisecond are called surges. Voltage swells are often caused by events on the distribution system such as lightening strikes, connection or disconnection of large inductive loads, or faults on nearby distribution circuits. Voltage swell can cause equipment failure, system lock–up, data corruption, data loss, or even result in fires depending on how high the swell is, and how long it lasts. To protect against these obvious risk, surge arresters, filters and isolation transformers are used.[26]

Voltage sags/dips also affect power quality. Dips are experienced when the supply voltage drops below the nominal voltage by 10% to 90% for 0.5 cycle to 1 minute; and they cause electronic loads to either shut off or behave strangely (e.g. motors to stall and over heat). Solutions to voltage sag problems involve the use of equipment like ferroresonant transformer, voltage regulators, energy storage technology, uninterruptible power supply (UPS), and dynamic voltage restorer (DVR).[27]

Frequency also affects power quality. Variations in frequency occur when the frequency of the connected load and that of the electric power generator are not synchronized.[28]

Waveform distortion, a steady–state deviation from the ideal sinusoidal wave, also affects power quality. The main types of waveform distortions are harmonics, notching, inter–harmonics, DC offset and noise. Harmonics are sinusoidal voltages or currents having frequencies that are integer multiples of the fundamental frequency while inter–harmonics have frequency components that are not integer multiples of the fundamental frequency. DC offset refers to the presence of a d.c. voltage or current in an a.c. system. Noise is unwanted electrical signals with broadband spectral content lower than 200 kHz, superimposed upon the power system voltage or current in phase conductors, or found in neutral conductors or signal lines.[29]

[...]


[1] (Borbely & Kreider, 2001)

[2] (Meier, 2006)

[3] (Küfeoğlu, 2015)

[4] (ERC, 2013, p. 18)

[5] (ERC, 2016)

[6] (Kenya Power Corporate Communications Dept., 2016)

[7] (ERC, 2016)

[8] (Fraser, et al., 2013)

[9] (Kadala & Saidi, 2014)

[10] (Otieno, 2014)

[11] (Kimani, 2014)

[12] (Alal, 2014)

[13] (Mijungu, 2017)

[14] (Meerow, Newell, & Stults, 2016, pp. 40, 45)

[15] (Ernstson, et al., 2010)

[16] (Meerow, Newell, & Stults, 2016)

[17] (Smith & Stirling, 2010)

[18] (Smith & Stirling, 2010)

[19] (Sansavini, 2016)

[20] (Meier, 2006)

[21] (Nordgård, Sand, & Wangensteen, 2010)

[22] (Meier, 2006)

[23] Supply voltage: the voltage reading taken at the point where the distribution system of the electricity supply authority (the Kenya Power and Lighting Company (KPLC)) and the electrical system of the consumer are connected.

[24] Nominal voltage: the highest and lowest voltages of an electrical system (excluding transient or abnormal conditions) which are expected under normal operating conditions at any time and at any point on the electrical system.

[25] (International Electrotechnical Commission (IEC), 2002)

[26] (Fathi, 2012)

[27] (Fathi, 2012)

[28] (Fathi, 2012)

[29] (Fathi, 2012)

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Pages
49
Year
2017
ISBN (eBook)
9783668499355
ISBN (Book)
9783668499362
File size
751 KB
Language
English
Catalog Number
v371577
Grade
Tags
Electricity

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Title: Enhancing Urban Resilience to Electricity Disruptions