Fjärrvärme är en väletablerad teknik i Sverige, i dagsläget kommer 50% av uppvärmningen i Sverige från fjärrvärme. I Kiruna står Tekniska Verken som leverantör av fjärrvärme, där hela 90% av alla fastigheter är anslutna till nätet. LKAB:s gruvverksamhet i Kiruna har lett till världens största stadsflytt, till följd av sprickbildningar och rörelser i marken som uppkommer i samband med brytningen efter järnmalmen. Stadsflytten samt reparationer av befintliga ledningar som går sönder som konsekvens av rörelserna i marken, har gjort att identifieringen samt underhållet av fjärrvärmenätets undercentraler har hamnat i skymundan. En underpresterande undercentral har många negativa konsekvenser för fjärrvärmenätet. Syftet med arbetet är att underlätta för Tekniska Verken att hitta de underpresterande undercentralerna. För det så har en applikation tagits fram, som kommunicerar med deras befintliga system för att sedan presentera relevant information till handhavande personal. De undercentraler som applikationen presenterar fyller de förutbestämda kriterierna: Flöde på 1000 [l/h] eller högre och en returtemperatur på 60 ºC eller högre. Vidare så har beräkningar utförts med den data som den framtagna applikationen tog fram, där befintlig returtemperatur från undercentralerna ersattes med en ny önskad returtemperatur. Beräkningarna utfördes för varje kvartal. Dygnsdata hämtades från 5 dagar från varje månad under våren, sommaren, hösten och vintern. För att göra beräkningarna mer hanterbara valdes 5 dagar istället för månadens alla dagar. Varje månad identifierades ett antal undercentraler enligt kriterierna ovan. För dessa undercentraler antogs en ny returtemperatur på 47 ºC för att motsvara åtgärder. Beräkningarna som utfördes ledde till besparingar i form av en kostnadsreduktion för pumpen och en utsläppsminskning av CO2 –ekvivalenter. För hela året blev kostnadsreduktionen för pumpen 97758 kr och utsläppsminskningen 7,32 tCO2e. Fler fördelar via rökgaskondenseringen uppnås också till följd av den sänkta returtemperaturen. Ett fjärrvärmesystem är väldigt dynamiskt, när en variabel ändras (i detta fall returtemperaturen) så påverkas indirekt flertalet andra. Någon exakt data för pumpen erhölls ej, endast snittförbrukningen per månad. Gällande trycket gjordes en uppskattning efter diskussioner med Tekniska Verken. Därefter gjordes ett antal antaganden för att kunna fullfölja uppskattningen av det nya systemet efter åtgärder på de underpresterande undercentralerna. / District heating is a well-established technology in Sweden; currently, 50% of heating in Sweden comes from district heating. In Kiruna, Tekniska Verken stands as the supplier of district heating, with a staggering 90% of all properties connected to the network. LKAB's mining operations in Kiruna have led to the world's largest urban relocation, due to ground fractures and movements arising from the extraction of iron ore. The city relocation and repairs of existing pipelines damaged by ground movements have diverted attention from the identification and maintenance of the district heating network's substations. Underperforming substations have many negative consequences for the district heating network. The purpose of the work is to facilitate Tekniska Verken in identifying the underperforming substations. To achieve this, an application has been developed that communicates with their existing system to then present relevant information to operational staff. The substations presented by the application meet predetermined criteria: a flow rate of 1000 [l/h] or higher and a return temperature of 60 ºC or higher. Furthermore, calculations have been performed using the data generated by the application, where the existing return temperature from the substations was replaced with a new desired return temperature. The calculations were conducted for each quarter. Using daily data from five days each month in spring, summer, autumn, and winter as the basis. To make the calculations more manageable, 5 days were chosen instead of all the days of the month. Each month a number of substations were identified based on the aforementioned criteria. For these substations a new return temperature of 47 ºC was assumed to correspond to actions. The calculations that were performed resulted in savings in the form of a cost reduction on the pump and a decrease of CO2 eqvuivalent emissions. For a year the calculations resulted in a cost reduction of the pump of 97758 SEK and a decrease of emissions: 7,32 tCO2e. More benefits via flue gas condensation are also achieved as a result of the lowered return temperature. A district heating system is highly dynamic; when one variable changes (in this case, the return temperature), several others are indirectly affected. No exact data for the pump was obtained, only the average consumption per month. Regarding pressure, an estimate was made after discussions with Tekniska Verken. Subsequently, a number of assumptions were made to complete the estimation of the new system after actions on the underperforming substations.

Call number: LD2668 .T4 1984 S625 / Master of Landscape Architecture

A dissertation submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering in the High Voltage Research Group School of Electrical and Information Engineering Johannesburg, June 2017 South Africa / Servitude availability in space-constrained built-up areas within the Johannesburg or Central Load Network (CLN) poses every-day challenges for power system engineers. Strengthening the backbone 88/275 kV transmission system within the CLN becomes even more difficult when multi-circuit transmission lines are required for increased power transfer capabilities. When uprating is considered to increase the power transfer capability, the withstand levels of existing external insulation demands an optimisation to find a new stress versus strength balance that allows reliable operation of substations at higher voltages. The research includes primarily an investigative simulation study to evaluate the current Eskom available design clearances in terms of their withstand capability when subjected to over-voltage transients. Two voltage range classes were evaluated and the results are discussed. For voltage range 1, it was found that the over-voltage stress was low enough to allow for a higher nominal operating voltage while maintaining the existing clearances. For voltage range 2, existing clearances are also found to be conservative and smaller safety margins will most likely be acceptable. From a transient analysis evaluation, voltage uprating is considered as a very attractive option to increase the power transfer capability of existing substations. Current Eskom clearances for 88 kV and 275 kV are expected to perform well during transients generated in uprated systems. Electrode grading to improve the field gradients in the substation will require attention to increase gap factors. Additional surge arresters are considered to be a cost effective solution to control over-voltages throughout the whole uprated substation. The physical modification of substations to replace strung conductors with tubular conductors, ensuring sufficient outage time to refurbish and rebuild with new equipment will be the most challenging part of uprating existing substations. / MT 2017

Os objetivos deste trabalho são apresentar e avaliar o projeto de uma subestação focando o compartilhamento da instalação, dos equipamentos e particularmente das informações entre empresas de transmissão e distribuição de energia, o que gera implicações relativas à segurança de acesso aos dados, à segurança na manutenção e operação e à divisão das responsabilidades técnicas. A necessidade desse tipo de projeto vem se tornando frequente no estado de São Paulo à medida que cresce o acesso ao sistema de transmissão pelas usinas térmicas das empresas do setor sucroalcooleiro, em concordância com as resoluções normativas da Agência Nacional de Energia Elétrica. O trabalho propõe a configuração de funções de supervisão e proteção utilizando a troca de informações entre os agentes através do serviço de mensagens prioritárias previsto na norma IEC 61850, em substituição aos relés auxiliares e ao painel de interface que utiliza cabos de cobre. Tendo a segurança como ponto principal de discussão quando se deseja conectar duas redes de comunicação de empresas diferentes, são avaliadas, através de simulações, as operações das lógicas de proteção, o acesso aos dados, e a troca de informações de supervisão. Algumas tecnologias apresentadas já são amplamente utilizadas na área de Tecnologia da Informação, como os requisitos de segurança digital e que, se utilizados em sistemas baseados na IEC 61850 sem impactar significantemente na performance e nos custos, apresentam enormes vantagens para os sistemas digitalizados das subestações. Por fim, são apresentadas as diferenças e os benefícios de se utilizar os recursos da norma para um projeto tão particular. / The aims of this study are to present and to evaluate the design of a substation, focusing on the sharing of the installation, equipments, and particularly on the information between transmission and distribution energy companies. This will highlight implications for data access security, along with the security concerning maintenance and operation of a substation and the division of technical responsibilities. The need for this type of project is becoming common in the state of São Paulo as the access to the transmission system by thermal power plants of sugar companies increases, in accordance with the normative resolutions of the Agência Nacional de Energia Elétrica. The study proposes the configuration of supervision and protection functions using exchange of information between agents via priority messaging service provided by IEC 61850 instead of the auxiliary relays and panel interface that uses copper wires. When connecting two communication networks of different companies while considering safety as the main issue, simulations are conducted to evaluate protection logic operations, data access and supervision data exchange. Certain technologies presented here are already widely used in Information Technology, such as the cyber security requirements. When utilized in IEC 61850 based systems without significantly impacting performance and costs, these cyber security requeriments present great advantages for the substations digitalized systems. Finally, differences and benefits are considered for the use of the resources of the norm for such a particular project.

Os objetivos deste trabalho são apresentar e avaliar o projeto de uma subestação focando o compartilhamento da instalação, dos equipamentos e particularmente das informações entre empresas de transmissão e distribuição de energia, o que gera implicações relativas à segurança de acesso aos dados, à segurança na manutenção e operação e à divisão das responsabilidades técnicas. A necessidade desse tipo de projeto vem se tornando frequente no estado de São Paulo à medida que cresce o acesso ao sistema de transmissão pelas usinas térmicas das empresas do setor sucroalcooleiro, em concordância com as resoluções normativas da Agência Nacional de Energia Elétrica. O trabalho propõe a configuração de funções de supervisão e proteção utilizando a troca de informações entre os agentes através do serviço de mensagens prioritárias previsto na norma IEC 61850, em substituição aos relés auxiliares e ao painel de interface que utiliza cabos de cobre. Tendo a segurança como ponto principal de discussão quando se deseja conectar duas redes de comunicação de empresas diferentes, são avaliadas, através de simulações, as operações das lógicas de proteção, o acesso aos dados, e a troca de informações de supervisão. Algumas tecnologias apresentadas já são amplamente utilizadas na área de Tecnologia da Informação, como os requisitos de segurança digital e que, se utilizados em sistemas baseados na IEC 61850 sem impactar significantemente na performance e nos custos, apresentam enormes vantagens para os sistemas digitalizados das subestações. Por fim, são apresentadas as diferenças e os benefícios de se utilizar os recursos da norma para um projeto tão particular. / The aims of this study are to present and to evaluate the design of a substation, focusing on the sharing of the installation, equipments, and particularly on the information between transmission and distribution energy companies. This will highlight implications for data access security, along with the security concerning maintenance and operation of a substation and the division of technical responsibilities. The need for this type of project is becoming common in the state of São Paulo as the access to the transmission system by thermal power plants of sugar companies increases, in accordance with the normative resolutions of the Agência Nacional de Energia Elétrica. The study proposes the configuration of supervision and protection functions using exchange of information between agents via priority messaging service provided by IEC 61850 instead of the auxiliary relays and panel interface that uses copper wires. When connecting two communication networks of different companies while considering safety as the main issue, simulations are conducted to evaluate protection logic operations, data access and supervision data exchange. Certain technologies presented here are already widely used in Information Technology, such as the cyber security requirements. When utilized in IEC 61850 based systems without significantly impacting performance and costs, these cyber security requeriments present great advantages for the substations digitalized systems. Finally, differences and benefits are considered for the use of the resources of the norm for such a particular project.

This report documents an MSc Thesis work of sub-transmission reliability study using PSS/Eperformed at Vattenfall. The network that is examined in this thesis is a sub-transmission network.Vattenfall Distribution Sweden is going to invest and rebuild the network in their 70 and 130 kVmeshed sub transmission network. To invest and rebuild in a network is very expensive. The gridowners want a reliable system that has a high reliability at a low cost.The main focus in this thesis is to examine different substation layouts. Calculating the failureintensities and unavailability for the different substation layouts gives the opportunity to do a life cyclecosts (LCC) on the different substations. With help of LCC calculations it is possible to find thesubstation that gives the lowest cost during a life time. Choosing right equipment in the grid will helpthe Vattenfall network company lower their equipment costs.The thesis work consists of mainly three parts as follows. Network modeling in PSS/EA subset of the existing sub transmission network was used in the project. This subset was taken outfrom the complete network model and modeled in PSS/E. Validation of PSS/E reliability modulesPSS/E reliability modules were new and have not been used earlier by the Vattenfall networkcompany. To be sure that the program calculates correctly a validation was performed. The main focusof the validation has been in looking if the program calculates the interrupted power correctly. Reliability analysis of different substation layoutsFor each of the substation layout the reliability was calculated. On component level (e.g. breaker,disconnector) different types of configuration were studied. To find out the best layout from aneconomical point of view a LCC calculation was also performed.The LCC calculation on the different substation layouts showed that the investment costs affect theresult very much. When the active power through the substation is low it is preferred to use asubstation that has low investment costs. At active power that is 30 MW or higher it is preferred to usethe substation with higher reliability (having higher investment cost). The result shows that using acombined breaker and disconnector instead of circuit breaker could lower the failure intensity andunavailability of substations.

A problem in the field of district heating is the oil burners needed to provide power when a peak load occurs. One possible way of reducing the needed amount of oil is to reduce the power demand for space heating in the district-heating substations when the need for district heating water exceeds a certain limit. This can be done by use of a locally working controller function. In this Thesis the options concerning load priority are evaluated. To evaluate the potential for using controller functions concerning peak load priority an experiment was brought out in a chosen district-heating substation. The impact on the indoor thermal comfort during a heat reduction was also taken into account. With simulations and mathematical models the building and the indoor air cool down was evaluated. Also a survey was given to the residents to validate how the indoor thermal climate was affected during the experiment. Possible savings by using these kinds of functions were also accounted for. The result demonstrates that a simple controller function provides a possible way of reducing the power demand, but is not sufficiently reliable. This is mainly due to the used regulating parameter. With modifications or by adding additional regulating parameters such as water flow into the controller, the functionality can be improved. The result from the survey shows that during the experimental period the residents experienced a minor impact on the thermal comfort. Parameters, such as ventilation and heat losses also have a major impact on the building´s thermal inertia, especially at the lowest occurring outdoor temperatures. The simulations confirm the theory regarding the building heat capacity to prevent a negative impact on indoor thermal comfort. In addition, the indoor air temperature can initially decrease faster than the building framework, especially under the influence of ventilation. This must be taken into account when applying functions for load priority. Calculations indicate that the economical benefits by adapting functions for load priority are primarily for the heat-producer, due to reduced oil dependence and also other system aspects. The current ownership structure in Uppsala provides for a possible obstacle when it comes to expanded use of load priority functions. More incentives for the consumer are needed to provide for an increased usage of load priority functions in their district-heating substations.

Thesis (M.S.)--Ohio University, November, 2009. / Title from PDF t.p. Includes bibliographical references.

M. Tech. Electrical Engineering. / In this work, the Current Limiter Technologies lifetime of a power transformer is developed and analysed. The general overview of the different techniques of limiting fault currents in an electric power system have been analysed, with an emphasis being placed on the research regarding two types of current limiters: one based on passive magnetic, and the other on high temperature, superconducting materials.

ADLash® is the trade name for an optical fibre cable attached to a transmission line shield wire using aramid-reinforced bands. The installation of this type of optic fibre cable has been considered for the HVDC line from the Songo hydroelectric scheme at Cahora Bassa in Mozambique, to Apollo substation in South Africa. The impact that installation of this cable will have on the onset of corona is examined. The shield wire with and without ADLash attached is modelled for both the actual line configuration and for corona cage studies. The electric field is calculated using the Method of Images and the Boundary Element Method to predict the electric field enhancements and to estimate the corona onset gradient. Corona onset gradients and phenomena for smooth and stranded conductors are researched to aid the prediction of voltage onset magnitudes for the corona cage. Estimated values are compared with observed values for both AC and DC applied voltages. Different patterns of corona and different corona onset voltages are observed for AC and negative DC applied voltages. The relative permittivity of the ADLash is higher than the surrounding air and this is shown to lead to greatly enhanced electric fields at the air/ dielectric/ shield wire interfaces that are significant enough to cause corona at the rated operating voltage. The corona will bombard the ADLash and probably damage it. Some alternative methods of installing fibre optic cables are reviewed for further research because the use of ADLash cannot be recommended. / Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2005.