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.

The present thesis tackles the problem of on-line steady state security assessment in electric power transmission networks. The contingencies examined include generation shift as well as line (transformer) outages. / The methodology developed is Pattern Recognition-motivated although not entirely within the frame of traditional statistical Pattern Recognition. / Due to the fact that training samples are rather expensive to obtain in electric power engineering, our first concern was to develop and implement algorithms carrying out the task of intelligently acquiring training points. It is found that these algorithms, permit to substantially reduce the amount of off-line computational effort while, at the same time, the coherency and impartiality of the information contained in the training sets is enhanced. / A new scheme for security assessment (equally applicable for real time security screening) was developed based on the concept of the hyperellipsoids of confidence. It is shown that by proper utilization of the hyperellipsoids of confidence, uncertainty in real time decision making (directly related to the misclassification error) is circumvented. The results of the new methodology were verified by full scale ac simulations. / Finally, the usefulness and potential applicability of the new scheme is demonstrated for EHV equivalents. Its merits are simplicity and reliability in real time environment.

Thesis (M.Ing.)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: The application of cycloaliphatic epoxide (CE) insulation in the Republic of South Africa is investigated within this thesis. There was a request from industry to evaluate the product and indicate its suitability for application within the various geographic and climatic zones typical of the RSA. An extensive survey was conducted into the historic origins of the material, and the experiences of international utilities applying the insulation medium in respect of polluted conditions. The properties of the Automatic Pressure Gelation (APG) CE insulator manufacturing process are discussed with reference to the manufacture of glass and porcelain insulation, and typical areas for concern are discussed with reference to insulators found to deviate from specification. Typical insulators were obtained from the manufacturers and utilities associated with the product, and were subjected to electrical, material and visual examination tests. The electrical tests included AC wet and dry, lightning impulse, clean fog, salt fog, mould release resiliency and the IEC 1109 voltage test. The material tests included the identification of the epoxide systems in use in the RSA, ultraviolet radiation aging simulation, water hydrolysis and salt deposit density tests. The main findings are: • CE insulation is sensitive to marine pollution and continuous-wetting pollution types. • The use of CE insulation is promoted in respect of inland and medium industrial pollution types. • Class B pin-type CE insulation is prone to partial discharge related failures. • Surface roughening on the insulator surfaces leads to reduced AC wet flashover voltages and increased pollution catch. Additionally: • A comprehensive aging hypothesis was developed detailing three independent aging stages/modes applying to CE insulation. • A hypothesis was developed for a new evaluation method for documenting changes on insulator surfaces due to the action of aging mechanisms: The Surface Area Index. / AFRIKAANSE OPSOMMING: Die aanwending van sikloalifatiese epoksied (SE) isolasie in die Republiek Van Suid Afrika word in hierdie skripsie ondersoek. Hierdie ondersoek is geloods op versoek van die elektrisiteitsbedryf om die toepaslike aanwending van die produk onder die verskeie heersende streeksweersomstandighede binne die RSA te evalueer. Breedvoerige navorsing is gedoen om die geskiedkundige oorsprong van die materiaal vas te stel, sowel as om die prestasie daarvan as insulasiemiddel te boekstaaf. Daar is veral gelet op die prestasie van die materiaal onder besoedelende omstandighede en ondervinding wat opgedoen is deur intemasionale ondememings. Die eienskappe van die automatiese drukjelvormings-vervaardigingsproses (APG) word behandel met verwysing na die maak van glas en porselein insulators. Tipiese probleemareas word bespreek van insulators wat afwyk van spesifikasie af. Verteenwoordigende isolators is vanaf vervaardigers en ondememings verkry wat met die produk bemoei is. Hulle is blootgestel aan elektriese, materiaal en visuele toetse. Die elektriese toetse het die volgende behels: nat en droog wisselstroom, skoon waterdamp, sout waterdamp en die IEe 1109 spanningstoets. Die effek van die verlies van die anti-kleefmiddel (gebruik tydens die gietproses) as gevolg van veroudering is ook in detail behandel. Die materiaaltoetse het ingesluit: die uitkenning van die epoksied stelsels in gebruik in die RSA, gesimuleerde veroudering deur ultravioletligbestraling, water hidroliese en soutlaag digtheids toetse. Die hoofbevindings is: • SE isolasie word bemvloed deur seelug besoedeling sowel as volgehoue benatting. Die gebruik van SE isolasie word voorgestel vir binnelandse gebruik sowel as in gebiede met mediumvlak nywerheidsbesoedeling. • Klas B pen-tipe SE isolasie is geneig tot deelontladings wat dan tot faling lei. • Oppervlakvergroffing lei tot In verminderde wisselstroom orvonksspanning onder nat toestande sowel as verhoogde vangs van besoedeling. Bykomend hiertoe is: • 'n breedvoerige SE verouderingshipotese ontwikkel wat drie onafhanklike stadia en modusse van die verouderingsproses uitgewys het. • 'n hipotese ontwikkel vir In nuwe evaluasiemetode om die verandering in die isolatoroppervlak as gevolg van veroudering te dokumenteer: Oppervlakte- Area Indeks (SAl).

Thesis (Master of Engineering in Electrical Engineering)--Cape Peninsula University of Technology, [2018]. / Introduction of IEC 61850 standard defined substation automation system communication. The need of interoperability among the relevant devices coming from different vendors is a necessity to ensure utilities/municipalities obtain value for money. Vendors used their own proprietary tools to achieve communication in a substation. This caused an Intelligent Electronic Device (IED) from vendor A could not communicate with an IED from vendor B. Utilities/municipalities are forced to depend on single vendor solutions in a substation automation system. IEC 61850 systems tout Interoperability as a major gain in the Substation Automation System (SAS) environment. The implementation of interoperable systems in SAS environment requires extensive testing and careful selection of vendors. This involves extensive testing to meet the required requirements of a certain SAS. Interoperability implementation and testing methods need to be formulated and tested rigorously with various scenarios of interoperability in an SAS. GOOSE messages form the foundation of IEC 61850 standard as they are responsible for the copper-less connections for peer to peer communications. GOOSE messages are based on peer to peer communications to enable interoperability at the bay level which is called horizontal communication. IEDs need to be carefully selected to ensure GOOSE messaging interoperability is achieved. Test methods are equally important as methodology to achieve interoperability. The purpose of this research is to perform an investigation on interoperability of IEC 61850 conformant IEDs based on evaluation of their protection functions. The research looks at various vendors on how each has interpreted the IEC 61850 standard. Also an analysis on requirements to achieve interoperability is conducted. Investigation on various vendor independent system configuration tools to ease the implementation burden of a multivendor application is done. Evaluation into flexible object modelling and naming conventions in order to achieve interoperability is performed. Various tests using different tools to assess the integrity of interoperability are completed. The research delivers a methodology to evaluate and implement GOOSE message interoperability. The interoperability methodology can be used for improvement of interoperability applications. The methodology can also be implemented as procurement requirement to ensure interoperability. The evaluation/implementation of interoperability can be included in Factory Acceptance Test (FAT). The methodology to achieve interoperability is only usefully when requirements are clear with regard to what needs to achieved by SAS.

Made available in DSpace on 2016-02-05T18:29:44Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-08-31. Added 1 bitstream(s) on 2016-02-05T18:33:07Z : No. of bitstreams: 1 000857581.pdf: 1412939 bytes, checksum: a0bc976f0ed13945de0da1c095f5ed56 (MD5) / Este trabalho aborda o problema de planejamento da expansão da rede de transmissão (PERT) e utiliza o modelo CC no horizonte de planejamento estático, em duas variações: com restrições de segurança N-1 (PERTES) e a formulação usual, sem restrições de segurança (PERTE). As meta-heurísticas busca tabu, GRASP e busca local iterada foram implementadas utilizando o framework ParadisEO e os parâmetros foram ajustados com auxílio do software paramILS. Os algoritmos foram testados em 42 sistemas teste divididos em 6 grupos de sistemas: Garver 6 barras (4 sistemas teste), IEEE 24 barras (10 sistemas teste), Sul Brasileiro 46 barras (4 sistemas teste), Sudeste Brasileiro 79 barras (4 sistemas teste), Nordeste Brasileiro 87 barras (8 sistemas teste) e Colombiano 93 barras (12 sistemas teste). Os testes verificaram a viabilidade de utilizar o framework ParadisEO para implementação de meta-heurísticas para o PERT. Além disso, foi criado um conjunto de informações de referência para utilização em trabalhos futuros com os problemas PERTE e PERTES / This work deals with the energy network transmission expansion planning problem (TEP) and uses two variations of the CC model on the static planning horizon: with N-1 security constraints (STEPS) and the usual formulation, without security constraints (STEP). The meta-heuristics tabu search (TS), GRASP and iterated local search (ILS) were implemented using the framework ParadisEO and the parameters tunning were made with the aid of paramILS. The algorithms were tested in 42 test systems divided into 6 groups: Garver 6 bars (4 test systems), IEEE 24 bars (10 test systems), 46 South Brazilian bars (4 test systems), Brazilian Southeast 79 bars (4 test systems), Brazilian Northeast 87 bars (8 test systems) and Colombian 93 bars (12 test systems). The tests showed the viability of ParadisEO framework to implement meta-heuristics for the TEP problem. In addition, a large benchmark for use in future STEP and SSTEP works was created.

Thesis Submitted in fulfilment of the requirements for the degree Master of Technology: Electrical Engineering in the Faculty of Engineering at the Cape Peninsula University of Technology, 2012 / The widespread deregulation and restructuring of electric power utilities throughout the world and the surge in competition amongst utility companies has brought about the desire for improved economic efficiency of electric utilities and the provision of better service to energy consumers. These end users are usually connected to the distribution network. Thus, there is a growing research interest in distribution network fault detection and diagnosis algorithms for reducing the down-time due to faults. This is done so as to improve the reliability indices of utility companies and enhance the availability of power supply to customers. The application of signal processing and computational intelligence techniques in power systems protection, automation, and control cannot be overemphasized. This research work focuses on power system distribution network and is aimed at the development of versatile algorithms capable of accurate fault detection and diagnosis of all fault types for operation in balanced/unbalanced distribution networks, under varying fault resistances, fault inception angles, load angles, and system operating conditions. Therefore, different simulation scenarios encompassing various fault types at several locations with different load angles, fault resistances, fault inception angles, capacitor switching, and load switching were applied to the IEEE 34 Node Test Feeder in order to generate the data needed. In particular, the effects of system changes were investigated by integrating various Distributed Generators (DGs) into the distribution feeder. The length of the feeder was also extended and investigations carried out. This was implemented by modelling the IEEE 34-node benchmark test feeder in DIgSILENT PowerFactory (DPF). In the course of this research, a hybrid combination of Discrete Wavelet Transform (DWT), decision-taking rule-based algorithms, and Artificial Neural Networks (ANNs) algorithms for electric power distribution network fault detection and diagnosis was developed. The integrated algorithms were capable of fault detection, fault type classification, identification of the faulty line segment, and fault location respectively. Several scenarios were simulated in the test feeder. The resulting waveforms were exported as ASCII or COMTRADE files to MATLAB for DWT signal processing. Experiments with various DWT mother wavelets were carried out on the waveforms obtained from the simulations. In particular, Daubechies db-2, db-3, db-4, db-5, and db-8 were considered. Others are Coiflet-3 and Symlet-4 mother wavelets respectively. The energy and entropy of the detail coefficients for each decomposition level based on a sampling frequency of 7.68 kHz were analysed. The best decomposition level for the diagnostic tasks was then selected based on the analysis of the wavelet energies and entropy in each level of decomposition. Consequently, level-1 db-4 detail coefficients were selected for the fault detection task, while level-5 db4 detail coefficients were used to compute the wavelet entropy per unit indices which were then used for fault classification, fault section identification, and fault location tasks respectively. Decision-taking rule-based algorithms were used for the fault detection and fault classification tasks respectively. The fault detection task verifies if a fault did indeed occur or not, while the fault classification task determines the fault class and the faulted phase(s). Similarly, Artificial Neural Networks (ANNs) were used for the fault section identification and fault location tasks respectively. For the fault section identification task, the ANNs were trained for pattern classification to identify the lateral or segment affected by the fault. Conversely, the fault location ANNs were trained for function approximation to predict the location of the fault from the substation in kilometres. Also, the IEEE 13 Node Benchmark Test Feeder was modelled in RSCAD software and batch mode simulations were carried out using the Real-Time Digital Simulator (RTDS) as a ‘proof of concept’ for the proposed method, in order to demonstrate the scalability, and to further validate the developed algorithms. The COMTRADE files of disturbance records retrieved from an external IED connected in closed-loop with the RTDS and the runtime simulation waveforms were used as test inputs to the developed Hybrid Fault Detection and Diagnosis (HFDD) method. Comparison of the method based on entropy with statistical methods based on standard deviation and Mean Absolute Deviation (MAD) has shown that the method based on entropy is very reliable, accurate, and robust. Results of preliminary studies carried out showed that the proposed HFDD method can be applied to any power system network irrespective of changes in the operating characteristics. However, certain decision indices would change and the decision-taking rules and ANN algorithms would need to be updated. The HFDD method is promising and would serve as a useful decision support tool for system operators and engineers to aid them in fault diagnosis thereby helping to reduce system down-time and improve the reliability and availability of electric power supply. Key words: Artificial neural network, discrete wavelet transform, distribution network, fault simulation, fault detection and diagnosis, power system protection, RTDS.

Orientadores: Ernesto Ruppert Filho, Carlos Alberto Baldan / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-13T08:37:22Z (GMT). No. of bitstreams: 1 Freitas_RafaelCassiolatode_M.pdf: 4732668 bytes, checksum: 0819e8d6aca546a3c44b407acd86b0a9 (MD5) Previous issue date: 2008 / Resumo: O crescimento da demanda de energia elétrica nos centros urbanos e industriais tem levado à necessidade de expansão dos sistemas de energia elétrica o que tem causado aumento nos níveis de curto-circuito, atingindo o limite da capacidade dos sistemas de proteção existentes exigindo sua substituição por outros de maior capacidade. Nessa situação nem sempre a recapacitação dos sistemas de proteção resolve o problema sendo necessário duplicar circuitos. Para postergar investimentos ou para funcionar na rede juntamente com o disjuntor ou ainda, para proteger os circuitos existentes quando conectados a geradores distribuídos, os limitadores de corrente instalados em série com os disjuntores atuais permitem limitar a corrente de falta, principalmente nos primeiros 100ms até a atuação do sistema de proteção. Dentre os diversos tipos de dispositivos limitadores de corrente elétrica existentes no mercado e também ainda em pesquisa atualmente, os construídos a partir de materiais supercondutores possuem a vantagem de proporcionar limitação de corrente elétrica praticamente instantânea causando mínima interferência no funcionamento normal dos sistemas de energia elétrica. Neste trabalho foram estudadas diversas configurações de limitadores de corrente elétrica utilizando fitas de materiais cerâmicos supercondutores de alta temperatura crítica (HTS), de modo especial os limitadores resistivos em forma de bobinas helicoidais enroladas com fita supercondutora BSCCO. Foi desenvolvida metodologia para o cálculo eletromagnético, projeto, construção e ensaio das bobinas supercondutoras do limitador de corrente, bem como se procurou caracterizar eletricamente a fita HTS sob influência de campo magnético externo com o objetivo de determinar as condições de corrente elétrica e de campo magnético sobre ela aplicado para a transição do estado supercondutor para o estado condutor normal do material ("quench"). Ao final do trabalho foram construídos e ensaiados dois protótipos limitadores de corrente elétrica supercondutores mostrando que, apesar da fita HTS de BSCCO ainda não possuir características adequadas para aplicação em limitadores de corrente, com a esperada evolução destes materiais já existe disponível a técnica para projetá-los e construí-los. / Abstract: The growth in demand of electric energy in urban and industrial centers has lead to the need of expansion of the electrical systems which has caused increase in short circuit levels, reaching the limit capacity of the existing protection systems requiring its replacement by others of greater capacity. In these situations the upgrade of protection systems does not always solve the problem being necessary the circuit's duplication. To postpone investments, to operate together in the electrical system with the circuit breakers or even to protect the existing circuits when connected to distributed generators, fault current limiters should be installed in series with the circuit breakers allowing to limit fault currents, specially in the first 100m until the protection system is triggered. Among the many different types of fault current limiter devices existing in the market and which are under development, the ones made of superconducting materials have the advantage of providing practically instantaneous fault current limitation causing minimum interference in the normal operation of the electrical systems. In this work many configurations of electric fault current limiters were studied using superconducting ceramic materials of high transition temperature (HTS), specially the resistive superconducting fault current limiters in form of helical coils with BSCCO superconducting tapes. The methodology for the electromagnetic calculation, project, construction and tests of the superconducting coils of the fault current limiter was carried out along with the HTS tape characterization under external magnetic field influence in order to determine the conditions of electric current and magnetic field for the transition from superconducting state to normal conducting state (quench). At the end of this work two fault current limiters were built and tested showing that, although BSCCO HTS tapes yet do not have good characteristics for fault current limiters application, when these materials which tend to be developed reach applicability level, the technique to design and built them is already available. / Mestrado / Energia Eletrica / Mestre em Engenharia Elétrica

Over the last the last three decades, there has been a significant and documented decrease of power engineering curriculum within U.S. electrical engineering programs. Development of lifelong learners capable of critical and independent thinking is required to replace the large number of upcoming retirees from the industry and to prepare for the engineering challenges new technologies, laws and regulations are bringing to the electrical power system. In response to these challenges, Portland State University redesigned its BSEE and MSECE power engineering programs in order to create a launching pad for successful power engineering careers. A course series on power system protection is part of the requisite curriculum for both programs. Due to the complex and applied nature of this subject, the course features a laboratory component. This thesis addresses the pedagogical and engineering problems associated with developing power systems protection laboratory curriculum. Laboratory equipment and curriculum design were guided by outcomes defined by ABET EC2000 and specific outcomes defined for the laboratory that we adopted from research commissioned by ABET. Hands-on experience with industry equipment and software enhances classroom-based course curriculum, expanding student understanding of the complexities of the subject of power system protection. Intergroup and intragroup communication is required in the laboratory, as are weekly written reports synthesizing subject material and experimental results. The outcomes of the laboratory are evaluated through a combination of grading rubrics and student participation in individual laboratory assignment surveys. The laboratory is comprised of three stations consisting of electromechanical (EM) relays and digital relay equipment. The practical experience with industry standard relays types happens in concert with a software-based simulation program. There are three phases of development; Phase I includes the design of the physical laboratory and the procural, or design and fabrication, of necessary equipment. Phase II involves the teaching term of the laboratory and the active assessment. Phase III involves the design and specification of a model-scale laboratory, to be built in future terms, which will provide students with the ability to test power system protection equipment in a physically simulated environment. This model-scale system will also provide a platform for future expansions of the power system protection laboratory in terms of distance protection, generation control, phasor measurement units, and system control schemes.

No description available.

No description available.