The objective of the research is to formulate and demonstrate protection schemes for radial and loop systems, an active distribution system, and a microgrid. The schemes are composed of a) A new loop scheme by utilizing voltage, current, and time (VIT) reclosers and sectionalizers and b) A new protection scheme, the dynamic state estimation-based protection, for active distribution systems and microgrids. The first part of the research explores the closing onto a fault during the conventional loop sectionalizing scheme and provides a VIT scheme that can solve the problem. The immediate benefit of the VIT schemes is a reduction of the nuisance trips because of the fault closing onto a fault. Moreover, the number of protection zones is increased by the application of the VIT sectionalizers. This thesis demonstrates the VIT protection scheme for a traditional distribution system and presents numerical experiments using various test scenarios with various fault locations. The simulation results verify that the protection scheme successfully performs the automatic load transfer scheme for a loop system. The second part of the research identifies the increased number of protection issues according to the installation of distributed generations (DGs) and provides solution to the problem. To solve the issue, a new fault detection scheme, dynamic state estimation-based protection scheme, is illustrated in this thesis based on synchronized measurements. The method uses dynamic state estimation, based on the dynamic model of the component that accurately reflects the nonlinear characteristics of the component. Numerical experiments show that the protection of active distribution systems and microgrids is feasible in real time.

<p>I samband med de ökade kraven på ett vädersäkrat nät har funderingar kring att placera ut fler frånskiljare/brytare i luftledningsnätet för att reducera medelavbrottstiden för anslutna kunder (SAIDI) kommit fram. I Finland använder man till stor del fjärrmanövrerade apparater för att reducera SAIDI. Rapportens inledande avsnitt innefattar en förstudie om ursprunget till avbrottstid och SAIDI-statistik i Vattenfall Eldistributions nät. En jämförelse med Eldistributions nät och klimatet i Finland utförs och av detta fås olika förutsättningar för nätet i de olika länderna. Som en generell slutsats av väderjämförelsen mellan Sverige och Finland fastställs att Eldistribution i Sverige har sämre förutsättningar vädermässigt när det gäller luftledningsnät. Resultaten från beräkningarna på sex exempelnät visar att den maximala reduceringen av SAIDI uppgår till 36 % och den minimala med 17 % i exempelnäten. Om alla nät skulle gå att bygga om enligt liknande principer skulle det innebära en reducering av Eldistributions mellanspännings-SAIDI med cirka 12 % ifall de 200 sämsta linjerna ur SAIDI-synpunkt kompletterades med fjärrfrånskiljare i motsvarande grad som exempelnäten. Jämförelser av investeringskostnader mellan fjärrfrånskiljaralternativ och kablifieringsalternativ visar att det är mer kostnadseffektivt att bygga om med fjärrfrånskiljare och därför är detta lämpligt om önskan är att så billigt som möjligt reducera SAIDI. Som en allmän rekommendation bör reservmatningar i nätet vara fjärrmanövrerade och dessutom bör linjer ha minst en fjärrfrånskiljare utlokaliserad. Då delas linjen upp i fler fjärrsektioneringsområden vilket förbättrar kundavbrottstiden för linjen. Ifall en linje inte har reservmatningmöjligheter bör det utredas ifall det är möjligt att med acceptabelt stora resurser bygga ihop nätet med ett annat nät för att möjliggöra en reservmatningsväg. Om det finns fler platser på linjen som är lämpliga för komplettering med fjärrfrånskiljare bör dessa utnyttjas för att så prisvärt som möjligt få ner SAIDI på den aktuella linjen. Ett allmänt råd angående antalet fjärrfrånskiljare per linje är svårt att ge men generellt sett är den första fjärrfrånskiljaren mycket mer kostnadseffektiv än de efterföljande. Stolpbrytare (reclosers) bör placeras ut där goda förutsättningar finns för att det skall bli lönsamt. Exempel på sådana platser kan vara vid övergång från kabel till luftledningsnät och innan en sträcka där fel ofta inträffar.</p> / <p>An alternative approach in Vattenfall Eldistribution’s network has evolved from the increased demands on reducing network downtime. Eldistribution are using remote controlled disconnectors / reclosers in Finland to reduce the system average interruption duration index (SAIDI). The initial section of the report includes a study on the source of downtime and SAIDI-statistics in Eldistribution’s network. A comparison with network and the climate in Finland is carried out which indicate different conditions in the two countries. The weather comparison shows that it’s more difficult to use non-insulated overhead-lines in Sweden because of the climate conditions. The result shows a maximum reduction of SAIDI by 36% and a minimum of 17% based on calculations on six example-lines. If all the lines would be possible to build under similar principles it would result in a reduction of Eldistributions SAIDI by approximately 12 % if the 200 worst lines was supplemented with remote controlled disconnectors with a corresponding amount of reduced SAIDI-minutes. Comparisons with cable alternatives show that it’s more cost-effective to invest in remoted controlled disconnectors if the target is a quick and cheap reduction of SAIDI. As a general recommendation the backup powering of a network should be remote controlled and the lines should have at least one outsourced remote controlled disconnector. This will split the line in multiple remote controlled areas, which will reduce disruption time for customers connected to the line. If a line doesn’t have any backup powering it should be investigated whether it’s possible to connect the line to another line to ensure backup-feeding if this is possible to do at acceptable costs. If there are more locations on the line suitable for supplementation of remote controlled disconnectors, those places should be used to get as much reduced SAIDI as possible at a cost-effective level. It's difficult to give a general advice concerning the number of remote controlled disconnectors but the first disconnector is generally more cost-effective than the subsequent ones. Reclosers should be deployed at appropriate locations to be equally costefficient as remoted controlled disconnectors. Examples of such places can be when switching from cable to non-insulated line and before a section where errors often occur.</p>

I samband med de ökade kraven på ett vädersäkrat nät har funderingar kring att placera ut fler frånskiljare/brytare i luftledningsnätet för att reducera medelavbrottstiden för anslutna kunder (SAIDI) kommit fram. I Finland använder man till stor del fjärrmanövrerade apparater för att reducera SAIDI. Rapportens inledande avsnitt innefattar en förstudie om ursprunget till avbrottstid och SAIDI-statistik i Vattenfall Eldistributions nät. En jämförelse med Eldistributions nät och klimatet i Finland utförs och av detta fås olika förutsättningar för nätet i de olika länderna. Som en generell slutsats av väderjämförelsen mellan Sverige och Finland fastställs att Eldistribution i Sverige har sämre förutsättningar vädermässigt när det gäller luftledningsnät. Resultaten från beräkningarna på sex exempelnät visar att den maximala reduceringen av SAIDI uppgår till 36 % och den minimala med 17 % i exempelnäten. Om alla nät skulle gå att bygga om enligt liknande principer skulle det innebära en reducering av Eldistributions mellanspännings-SAIDI med cirka 12 % ifall de 200 sämsta linjerna ur SAIDI-synpunkt kompletterades med fjärrfrånskiljare i motsvarande grad som exempelnäten. Jämförelser av investeringskostnader mellan fjärrfrånskiljaralternativ och kablifieringsalternativ visar att det är mer kostnadseffektivt att bygga om med fjärrfrånskiljare och därför är detta lämpligt om önskan är att så billigt som möjligt reducera SAIDI. Som en allmän rekommendation bör reservmatningar i nätet vara fjärrmanövrerade och dessutom bör linjer ha minst en fjärrfrånskiljare utlokaliserad. Då delas linjen upp i fler fjärrsektioneringsområden vilket förbättrar kundavbrottstiden för linjen. Ifall en linje inte har reservmatningmöjligheter bör det utredas ifall det är möjligt att med acceptabelt stora resurser bygga ihop nätet med ett annat nät för att möjliggöra en reservmatningsväg. Om det finns fler platser på linjen som är lämpliga för komplettering med fjärrfrånskiljare bör dessa utnyttjas för att så prisvärt som möjligt få ner SAIDI på den aktuella linjen. Ett allmänt råd angående antalet fjärrfrånskiljare per linje är svårt att ge men generellt sett är den första fjärrfrånskiljaren mycket mer kostnadseffektiv än de efterföljande. Stolpbrytare (reclosers) bör placeras ut där goda förutsättningar finns för att det skall bli lönsamt. Exempel på sådana platser kan vara vid övergång från kabel till luftledningsnät och innan en sträcka där fel ofta inträffar. / An alternative approach in Vattenfall Eldistribution’s network has evolved from the increased demands on reducing network downtime. Eldistribution are using remote controlled disconnectors / reclosers in Finland to reduce the system average interruption duration index (SAIDI). The initial section of the report includes a study on the source of downtime and SAIDI-statistics in Eldistribution’s network. A comparison with network and the climate in Finland is carried out which indicate different conditions in the two countries. The weather comparison shows that it’s more difficult to use non-insulated overhead-lines in Sweden because of the climate conditions. The result shows a maximum reduction of SAIDI by 36% and a minimum of 17% based on calculations on six example-lines. If all the lines would be possible to build under similar principles it would result in a reduction of Eldistributions SAIDI by approximately 12 % if the 200 worst lines was supplemented with remote controlled disconnectors with a corresponding amount of reduced SAIDI-minutes. Comparisons with cable alternatives show that it’s more cost-effective to invest in remoted controlled disconnectors if the target is a quick and cheap reduction of SAIDI. As a general recommendation the backup powering of a network should be remote controlled and the lines should have at least one outsourced remote controlled disconnector. This will split the line in multiple remote controlled areas, which will reduce disruption time for customers connected to the line. If a line doesn’t have any backup powering it should be investigated whether it’s possible to connect the line to another line to ensure backup-feeding if this is possible to do at acceptable costs. If there are more locations on the line suitable for supplementation of remote controlled disconnectors, those places should be used to get as much reduced SAIDI as possible at a cost-effective level. It's difficult to give a general advice concerning the number of remote controlled disconnectors but the first disconnector is generally more cost-effective than the subsequent ones. Reclosers should be deployed at appropriate locations to be equally costefficient as remoted controlled disconnectors. Examples of such places can be when switching from cable to non-insulated line and before a section where errors often occur.

The objective of the dissertation is to develop simplified analytical models for typical linear-motion and rotary-motion energy-conversion systems under active DC excitation without tedious numerical-simulation effort, and provide practical implementation of the models in optimal-design and thermal-protection aspects. The model of a vacuum automatic circuit recloser (a typical linear-motion system under DC excitation) is first developed in the form of a non-linear discontinuous eighth-order dynamic system. The model is then used to simulate the transient mechanical and electromagnetic performance during the opening and closing movements of the recloser. Such a model is not found in the literature. Although the model is based on certain simplifying assumptions, the result is validated by high-speed-camera measurements. In addition, the impact of key design variables is explored, based on which an improved recloser design is proposed, and helps to optimize capital and production costs without degrading performance. Further analytical investigation is carried out in modeling an inverter-fed induction motor (IM) (a typical rotary-motion system) with active DC injection. The IM is closed-loop controlled via two popular motor-control algorithms, namely, the direct-torque-control (DTC) algorithm and field-oriented-control (FOC) algorithm. Quantitative relationships between the changes of various machine variables during the active DC excitation are provided in the theoretical analysis. The developed DC-injection model is further simplified for practical implementation. The developed IM model under DC injection results in practical ways to excite a proper amount of DC current directly or indirectly into IM stator windings via different closed-loop motor-control algorithms. In a DTC motor-drive system, the modeling work makes it possible to excite the DC current indirectly inside the motor by superimposing a stator-flux-linkage-bias command in the flux-control loop or a torque-ripple command in the torque-control loop. The proposed flux-linkage-injection and torque-injection methods are the first novel efforts to implement the DC-signal-injection method in a DTC motor-drive system. In addition, the analysis carried out in a standard FOC drive system brings about an improved DC-current-injection approach: the torque ripple in this method is significantly mitigated compared to all existing DC-injection methods in FOC systems. The proposed DC-injection methods, either in a DTC or an FOC system, lead to a simple, low-cost, accurate, and non-invasive thermal-monitoring scheme for closed-loop-controlled IMs, where the stator temperature is indirectly estimated from stator resistance. Furthermore, considering inverter non-idealities, there is a challenge for a typical inverter drive to accurately estimate the DC component of motor terminal voltages. The existing methods are extended to provide a complete study of the real-time signal-processing technique for both DTC and FOC algorithms, and are finally implemented in a custom-built programmable motor-drive system. The experimental results demonstrate that the proposed technique gives accurate and robust stator-temperature estimation, regardless of the operating conditions and cooling modes. The analytical modeling method for the linear-motion and rotary-motion energy-conversion systems can be further extended to other power devices with similar mechanisms, and implemented in optimal design, control, and thermal-protection areas.

The distribution system which forms the final connection between customers and power source plays a vital role in an electrical network. Different studies show that substantial proportion of the customer interruptions occurs due to the failures on distribution network. The ongoing privatization process of the electrical distribution services in Turkey raises the importance of reliable and continuous electricity supply significantly. The new regulations come up with this privatization process and the electrical distribution companies are strictly required to comply with these regulations to ensure the reliability of the distribution network. The legal framework and severe punishments applied to the electrical distribution companies exceeding the continuity of supply indices force them to invest on their network in order to increase the reliability of their system. As the reliability of electricity supplied increases, investment cost also increases. However, low system reliability causes higher outage frequency and duration which will increase the damage of these outages to customers and also increases the cost of the distribution company as a result of the penalty payments. This tradeoff between Outage Cost and Utility Cost requires consideration of an optimization when determining the optimal reliability level. In rural areas where electrical distribution network consists of long radial overhead lines in arborescent structure, continuity of supply is a major problem due to the high failure rates. The implementation of protection devices having reclosing capability and automated sectionalizing switches enhances the continuity of supply on rural networks substantially. The balance between the cost associated with installation of switches and the reduction on Outage Cost is an important optimization issue for distribution network operators. In this thesis study an algorithm is developed in order to determine the optimum number and locations of the sectionalizing switches on a rural electrical distribution network in Turkey which gives an optimum investment level with an optimum Outage Cost.

The aim of this Master’s Thesis is to describe protections for overhead lines in distribution networks. Here are described requirements for the protection and the basic protections. Protections are divided according to their protective function. For each protection is given its use and its power plans. It is stated in the work setting of protection in the real network. On this network is simulated place with short-circuit and described the action of protection. The work also deals with the coordination of protection with automatic circuit breakers. This chapter shows that, given the selectivity is not possible to deploy two or more reclosers (remotely-operated switches) to the core network management. The next chapter describes two representatives reclosers available on the Czech market OSM 27 and GVR 27. Chapter describes and compares their performance characteristics. Conclusion the work includes a proposal protected the lead in incorporating automatic circuit breakers (remotely operated circuit breakers and reclosers). The proposal is based on two different levels of annual number of interruptions and duration of annual general interruption of electricity supply. For these levels the company EGÚ Brno, a.s. proposed several variants of the use of remote-controlled in terms of reducing the cost of the penalty. Our task was to choose a variant that would be applicable in the real network. Reducing costs is feasible only in the limits Ln = 6 failures / year and Lt = 720 min / year, where the selected option No. 4. The limits Ln = 8 failures / year and Lt = 1,080 min / year, not in the real network may no option in terms of selectivity.