الفهرس 
Phase Shifting TransformersOnly 14 pages are availabe for public view
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Abstract
Phase shifting transformers have various applications in power flow control, power electronics applications and limiting the levels of short circuit currents. Phase shifting transformers are characterized by their variable phase shift and, hence, CT connection cannot solve this problem for current differential protection relays. The proposed technique is based on developing a methodology that depends on the relations of magnetically coupled and electrically connected circuits. This technique can be applied to single core Phase Shifting Transformers (PSTs) such as delta hexagonal phase shifting transformer. Conventionally, the differential current is calculated by comparing a measured quantity with another similar measured, or calculated, value. This concept is modified to calculate the differential current by comparing a calculated quantity with another calculated one. According to this concept, the excitation currents are calculated twice: the first one is from the relations of the magnetically coupled circuits and the other one is from Kirchhoff’s current law. These calculated currents are used for obtaining the operating and restraining currents of the differential protection relay. The modelling and simulation of the delta hexagonal phase shifting transformer is accomplished using Matlab/Simulink® software package. The algorithm is examined for ideal transformers as well as when considering the iron core characteristics for both the phase shifting transformer and the current transformers. The system is investigated with shunt faults and series faults such as turns faults. IV A Transmission system is designed and fabricated with a voltage rating up to 390 V containing the single core delta hexagonal phase shifting transformer. The transformer has been checked with various shunt and series faults similar to those used during the simulation process. The results confirm the validity of the proposed protection algorithm for delta hexagonal phase shifting transformer and it represents a promising direction for protection of other types of phase shifting transformers.