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This thesis describes the development of a new directional relay for the ultra-high-speed protection of EHV transmission lines. The work has been carried out by utilising digital computer simulations, and the relay has been developed assuming that it would be implemented by micro-computer. This has enabled the use of a new digital filtering structure, which has been specifically devised to extract the superimposed quantities that the directional principle is concerned with. A modal transformation is utilised within the relay in order to define decoupled wave signals for a multi-conductor system, the transformation is also shown to provide significant hardware economies in the final design. In order to study the characteristics of the new relay, a number of new primary system digital simulations have been devised and are described in the thesis. These simulations include single and double-circuit multi-terminal systems with advanced fault capabilities. The novel decision process, in combination with the digital filter, enables the relay to provide a secure directional decision within typically, 2.5 ms of a fault occurring. Such an operating time will enable ultra-high-speed clearance of faults to be achieved, if the most recent circuit breaker developments and wide-band communication equipment are also employed.

Master of Science / Department of Electrical and Computer Engineering / Noel Schulz / New applications are continuously emerging in the ever-changing field of power systems in the United States and throughout the world, consequently causing new pressures on grid performance. Because power system protection is a fundamental aspect of the system, their operation must be addressed when a system is under high stress or when a high demand of energy is required. An extreme example is the transmission protection of a system because it transports large amounts of power. Transmission lines in a power system are frequently exposed to faults and generally protected by distance relays. If a faulted segment of transmission lines is not cleared in a short period of time, the system becomes unstable. The basic function of distance protection is to detect faults in buses, transmission lines, or substations and isolate them based on voltage and current measurements. Power system protection has previously focused on matching automation and control technologies to system performance needs. This report focuses on project activities that run simulations to determine settings for a protective relay for pilot overreaching transfer tripping and then test the settings using hardware equipment for various scenarios. The first set of scenarios consists of five faults in the system; two faults are in the protected line, and the remaining faults are outside the protective line. The second set of scenarios consists of instrument transformer failures in which the current transformer (CT) of one relay fails to operate while the other relay is fully operational. The second scenario consists of a failure of the voltage transformer (VT) of one relay while the other relay remains fully operational. Finally, the third and fourth scenarios consist of the failure of both CTs and VTs for each relay.

Instrument transformers are a crucial component of power system protection. They supply the protection system with scaled-down replicas of current and voltage signals present in a power network to the levels which are safe and practical to op- erate with. The conventional instrument transformers are based on electromagnetic coupling between the power network on the primary side and protective devices on the secondary. Due to such a design, instrument transformers insert distortions in the mentioned signal replicas. Protective devices may be sensitive to these distortions. The inuence of distortions may lead to disastrous misoperations of protective devices. To overcome this problem, a new instrument transformer design has been devised: optical sensing of currents and voltages. In the theory, novel instrument transform- ers promise a distortion-free replication of the primary signals. Since the mentioned novel design has not been widely used in practice so far, its superior performance needs to be evaluated. This poses a question: how can the new technology (design) be evaluated, and compared to the existing instrument transformer technology? The importance of this question lies in its consequence: is there a necessity to upgrade the protection system, i.e. to replace the conventional instrument transformers with the novel ones, which would be quite expensive and time-consuming? The posed question can be answered by comparing inuences of both the novel and the conventional instrument transformers on the protection system. At present, there is no systematic approach to this evaluation. Since the evaluation could lead to an improvement of the overall protection system, this thesis proposes a comprehensive and systematic methodology for the evaluation. The thesis also proposes a complete solution for the evaluation, in the form of a simulation environment. Finally, the thesis presents results of evaluation, along with their interpretation.

The primary goal of this work is to develop a PSCAD/EMTDC simulation model which can emulate the reclosing capabilities of an actual reclosing relay. The first part of this work will demonstrate the capabilities of a commercially available, microprocessor-based reclosing relay, the SEL-551c. Next, a computer simulation model of this relay's reclosing capability will be developed in PSCAD/EMTDC and validated. The performance of the model will be compared to the performance of the SEL-551c. Because it is impractical to test the relay operation under fault conditions in a real distribution system, fault characteristics will be determined in PSCAD. Utilizing a test system for the SEL relay, we can show the accuracy of the PSCAD recloser model compared to the SEL-551c relay for similar fault scenarios. The validation is done by analyzing the data from the simulation and experiment. The results show that both the PSCAD recloser model and SEL-551c operate close to the expected theoretical values. The primary contribution of this work is the development of a PSCAD recloser model and validation with a real world reclosing relay. In previous works where recloser analysis was done in PSCAD, such as [14], recloser operation was manually accomplished. However, the recloser model developed in this work allows the user to enter any standard TCC equation that may be programmed into an actual relay and achieve similar results. The model is useful when analyzing larger distribution systems with multiple reclosers. Additionally, validating the PSCAD recloser model with a real world device provides confidence that the simulations provide reasonable and meaningful results. / text

Following the introduction of the microprocessor into the power system protection field, modern microprocessor based numeric relays have developed very rapidly in the last 20 years, and modern power system protection schemes are virtually all based on microcomputers technology. The International Electro-technical Commission (IEC) recently launched the standard IEC61850, “Communication Networks and System in Substation”, which is having a major impact on the structure of new protection systems and schemes. In itself it describes the concepts for sub-station communications covering protection, control and metering functions. However, although it is going to have a major impact on the power systems communications, it will also influence the design of future protection systems. There will also be a host of other opportunities and advantages that can be realised. These include easier upgrading, refurbishment and replacement of sub-station protection. They also provide for greater use of general purpose Intelligent Electronics Devices (IEDs), self-healing systems, and plug and play type facilities. The Ethernet based communication network for data transfer between process level switchyard equipment and bay level IEDs, the process bus, is defined in IEC61850 Section 9-2. This process bus facilitates the communication of two types of real-time, peer-to-peer communication messages. Generic object-oriented substation event messages, the GOOSE messages and the data sample values, SVs which include the measured currents and voltages. Although this standard describes the message structures and the timing requirements, it does not describe the process bus topology. This work describes different LAN topologies that can be used in the design of process bus for protection systems. It considers the implications of the different structures on the operation of the protection scheme and how these relate to the operational strategy of different operators. It provides an assessment of the data handling capabilities of the system and how the demands of the protection system can be met. Several potential problem areas are identified and analyzed. The probabilistic nature of these systems is discussed and the implications explained. It also provides an insight into the implementation of the alternative topologies and their performance when applied to a transmission line feeder protection and transformer protection. The digital substation and the implementation of IEC61850 are fundamental to the future of protection ‘relays’. There are many pointers to the potential directions that these systems will develop and the skills required for the protection engineers of the future. This project is seeking to overcome some of the ownership challenges presented by modern protection and control (P&C) devices, which have an inherent short life due to their dependence on modern electronics and software.

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Future all-electric warships with an integrated power system (IPS) are capable of unlocking large amounts of power dedicated to propulsion and redirecting this power for service loads, weapon loads, and other loads. The IPS for all-electric ships combines the power generation system, electric propulsion system, power distribution system, and power control and management system all together. The move to IPS design will significantly improve efficiency, effectiveness, and survivability. To meet the needs of the US Navy, enhancing survivability by reducing susceptibility to damage, a IPS prefers decentralized reconfiguration system is preferred for IPS instead of traditional reconfiguration techniques used for terrestrial power grids. A multi-agent system (MAS) is a loosely coupled network composed of several agents. These agents interact with their environments and communicate with each other to solve problems that are beyond the individual capabilities or knowledge of each single agent. Because of its decentralized feature and lack of a global control feature, MAS appears to be the best candidate for IPS reconfiguration. This research work proposes a new model of an IPS, based on the Naval Combat Survivability, DC Distribution Test-bed (NCS DCDT). The new model combines the electric power generation system, electric propulsion system, and AC-DC zonal distribution system. To decrease the probability of distribution zones losing power, the new model modifies original design of the zonal distribution system in NCS DCDT. Another main endeavor of this research work is to design a MAS for reconfiguration of an IPS with AC-DC zonal distribution system. The MAS consists of three sub-MAS, named power generation MAS, propulsion MAS, and distribution MAS, and includes forty-one different agents which are instances of nineteen different abstract agent classes. The MAS is implemented with JAVA/JADE software and simulated on a platform of JADE 3.4.1 and JAVA jdk 1.5.0_08. Simulation results show that the MAS can execute reconfiguration functions such as fault area isolation, automatic switching, and load shedding.

Developing microgrids is an attractive solution for integrating inverter-based resources (IBR) in the power system. Distributed control is a potential strategy for controlling such microgrids. However, a major challenge toward the proliferation of distributed control is cybersecurity. A false data injection (FDI) attack on a microgrid using distributed control can have severe impacts on the operation of the microgrid. Simultaneously, a microgrid needs to be protected from system faults to ensure the safe and reliable delivery of power to loads. However, the irregular response of IBRs to faults makes microgrid protection very challenging. A microgrid is also susceptible to faults inside IBR converters. These faults can remain undetected for a long time and shutdown an IBR. This dissertation first proposes a method that reconstructs communicated signals using their autocorrelation and crosscorrelation measurements to make distributed control more resilient against FDI attacks. Next, this dissertation proposes a protection scheme that works by classifying measured harmonic currents using support vector machines. Finally, this dissertation proposes a protection and fault-tolerant control strategy to diagnose and clear faults that are internal to IBRs. The proposed strategies are verified using time-domain simulation case studies using the PSCAD/EMTDC software package. / Doctor of Philosophy / Renewable energy resources, such as wind, solar, and geothermal, are interfaced with the grid using DC-to-AC power electronic converters, popularly known as inverters. These “inverterbased resources (IBR)” are mostly distributed and located near consumers. During outages, IBRs can be used to provide power to customers. This gives developers the idea of integrating IBRs in microgrids. A microgrid is a miniature grid that consists of IBRs and customers. A microgrid is normally connected to the grid but can disconnect from the grid and operate on its own. To run efficiently, a microgrid uses fast and reliable communication between IBRs to create a high-performance distributed control strategy. However, this creates cybersecurity concerns for microgrids. This dissertation proposes a cybersecure distributed control strategy to make sure microgrids can keep their advantages. This dissertation also proposes a protection method that relies on machine learning to clear short circuits in the microgrid. Finally, this dissertation proposes a strategy to diagnose failures inside IBRs and ride through them. The proposed solutions are verified using the industry-grade simulation software PSCAD/EMTDC.