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- Genre: Masters Thesis
Description
This research work describes the design and validation of protection schemes developed to solve the problem of communication with an ability to detect and sectionalize the fault. Protection schemes have been designed according to the requirements of the Future Renewable Electric Energy Delivery and Management (FREEDM) system. Due to the presence of distributed generation (DG), power flow in the loop is bi-directional and conventional protection schemes may face the problem of unwanted tripping. Hence customized protection schemes have been developed specific to the FREEDM system. Former FREEDM students at ASU have developed ultrafast pilot differential protection using fast analog communication (Ethercat communication) and modified it in various ways to speed up the fault detecting capability of the algorithm. However, the National Science Foundation (NSF) criticized the use of Ethernet communication, as it is not compatible for long distances. FREEDM loop uses a fault current limiter (FCL) to limit the fault current and the substation solid state transformer (SST) reduces the system voltage to limit the fault current to 2 per unit. This allows the protection scheme to detect fault current in 2-3 cycles. However a much delayed fault detection is not encouraged as it will disrupt the power supply to healthy parts of the system for a longer duration. Time inverse directional overcurrent protection, pilot directional protection and PMU based protection are developed in this thesis work addressing the communication problem and at the same time with the ability to quickly detect the faults. Validation of the protection scheme is performed on the Real Time Digital Simulator (RTDS) at the Center for Advanced Power Systems (CAPS) using SEL relays and simulation models are developed in PSCAD.
ContributorsMandava, Pavanchandra (Author) / Karady, Dr. George (Thesis advisor) / Ayyanar, Dr. Raja (Committee member) / Holbert, Dr. Keith (Committee member) / Arizona State University (Publisher)
Created2014
Description
This research work describes the design of a fault current limiter (FCL) using digital logic and a microcontroller based data acquisition system for an ultra fast pilot protection system. These systems have been designed according to the requirements of the Future Renewable Electric Energy Delivery and Management (FREEDM) system (or loop), a 1 MW green energy hub. The FREEDM loop merges advanced power electronics technology with information tech-nology to form an efficient power grid that can be integrated with the existing power system. With the addition of loads to the FREEDM system, the level of fault current rises because of increased energy flow to supply the loads, and this requires the design of a limiter which can limit this current to a level which the existing switchgear can interrupt. The FCL limits the fault current to around three times the rated current. Fast switching Insulated-gate bipolar transistor (IGBT) with its gate control logic implements a switching strategy which enables this operation. A complete simulation of the system was built on Simulink and it was verified that the FCL limits the fault current to 1000 A compared to more than 3000 A fault current in the non-existence of a FCL. This setting is made user-defined. In FREEDM system, there is a need to interrupt a fault faster or make intelligent deci-sions relating to fault events, to ensure maximum availability of power to the loads connected to the system. This necessitates fast acquisition of data which is performed by the designed data acquisition system. The microcontroller acquires the data from a current transformer (CT). Mea-surements are made at different points in the FREEDM system and merged together, to input it to the intelligent protection algorithm that has been developed by another student on the project. The algorithm will generate a tripping signal in the event of a fault. The developed hardware and the programmed software to accomplish data acquisition and transmission are presented here. The designed FCL ensures that the existing switchgear equipments need not be replaced thus aiding future power system expansion. The developed data acquisition system enables fast fault sensing in protection schemes improving its reliability.
ContributorsThirumalai, Arvind (Author) / Karady, George G. (Thesis advisor) / Vittal, Vijay (Committee member) / Hedman, Kory (Committee member) / Arizona State University (Publisher)
Created2011
Description
In the future electrical distribution system, it can be predicted that local power generators such as photovoltaic panels or wind turbines will play an important role in local distribution network. The local energy generation and local energy storage device can cause indeterminable power flow, and this could cause severe protection problems to existing simple overcurrent coordinated distribution protection system. An accurate, fast and reliable protection system based on pilot protection concept is proposed in this thesis. A comprehensive protection design specialized for the FREEDM system - the intelligent fault management (IFM) is presented in detail. In IFM, the pilot-differential protective method is employed as primary protection while the overcurrent protective method is employed as a backup protection. The IFM has been implemented by a real time monitoring program on LabVIEW. A complete sensitivity and selectivity analysis based on simulation is performed to evaluate the protection program performance under various system operating conditions. Followed by the sensitivity analysis, a case study of multiple-terminal model is presented with the possible challenges and potential limitation of the proposed protection system. Furthermore, a micro controller based on a protection system as hardware implementation is studied on a scaled physical test bed. The communication block and signal processing block are accomplished to establish cooperation between the micro-controller hardware and the IFM program. Various fault cases are tested. The result obtained shows that the proposed protection system successfully identifies faults on the test bed and the response time is approximately 1 cycle which is fast compared to the existing commercial protection systems and satisfies the FREEDM system requirement. In the end, an advanced system with faster, dedicated communication media is accomplished. By verifying with the virtual FREEDM system on RTDS, the correctness and the advantages of the proposed method are verified. An ultra fast protection system response time of 4ms is achieved, which is the fastest protection system for a distribution level electrical system.
ContributorsLiu, Xing (Author) / Karady, George G. (Thesis advisor) / Farmer, Richard (Committee member) / Ayyannar, Raja (Committee member) / Arizona State University (Publisher)
Created2012