Use Of Phase Shifting Transformers Research Articles

Feasibility of using phase-shifting transformers to increase the throughput of interconnected power transmission systems

This paper discusses measures aimed at improving the efficiency of power systems by increasing the capacity of power transmission lines. To that end, a FACTS technology based on a phase-shifting transformer was used. The feasibility of using phase-shifting transformers to increase the throughput capacity of interconnected power transmission systems was investigated by determining the maximum allowable cross-section flows of the United Energy System of the Urals – the United Energy System of Siberia. The studied cross-section included 500 kV transmission lines and the extended 220 kV Nizhnevartovskaya GRES – Tomskaya transit. Calculations were performed for normal and various post-emergency schemes using the RastrWin3 software package. The regulation of phas e-shifting transformer branches and the direction of power flow in the section were taken into account. For the considered cross -section, the use of a phase-shifting transformer was shown to provide for the 220 kV transit operation in a closed mode. This i mproved the reliability of power supply in the region and allowed the maximum allowable overflow to be increased by 35 – 71%. In addition, similar calculations were carried out for the option of strengthening the 220 kV transit through the construction of a parallel 500 kV line. The effect of increasing the capacity of this option was established to reach 20 –35%. The decisive factor limiting the maximum permissible cross-section flows during 220 kV transit short circuit in the normal and reinforced versions was found to be the current overload of the head sections. Recommendations on the preferable use of an open transit mode are formulated. In conclusion, the efficiency of power systems can be improved by increasing the transmission capacity of power lines through the use of phase-shifting transformers. A segment of the Unified National Power Grid of Russia, where such devices are technologically expedient, was identified.

Developing of functioning algorithm ofinformation-control system for phase-shifting devices in power lines

The article is devoted todevelopment of afunctioning algorithm of the control systemof phase-shifting devices in double-circuit overhead power lines, as well as to the formulation of the main tasks of this system. Based on these, functional schemes for controllingphase-shifting devices were developed.The developed system will allow, through the use of phase-shifting transformers, which belong to the flexible alternating currenttransmission system (FACTS)technology, to change the value of phase shift angle of the voltage and current vectors of one circuit relative to anotherthat.Thiswill lead to a change in the value of the wave impedance of double-circuit lines, due to the emergence of new electromagnetic connections between the conductors of the two circuits. The main task of the developed system is to support the operation of power lines in the matched load mode, when the value of the wave imped-anceis equal to the value of the load impedance. It follows from the analysis that this mode provides the lowest losses in the trans-mission of electricity through power lines.The implementation of this control system is planned by using the Internet of Things in-formation technology, that is, the formation of a wireless connection between the main elements of the system for data transmission.The developed system can be attributed to information systems, as well as the current concept of SmartGrid.Thus, a method has been proposed to increase efficiency by reducing losses during the transmission of electricity through double-circuit power lines through the use of the concept of Smart Grid.

A universal mathematical model of a three-phase transformer with a single magnetic core

A universal mathematical model of a three-phase transformer with a single magnetic core for different variants of primary and secondary winding connections using wye and delta schemes at each of 12 phase shifts using clock notation is described. Such a model design is necessitated by the requirements of GOST (State Standard) 30830-2002 (IEC 60076-1-93) and by the wide use of phase-shifting transformers as elements of schemes for feeding power semiconductor converters. Examples of simulation results for cases of three-phase transformers of Y/Y-8 and Y/Y-4 schemes and vector groups are shown. The proposed model allows the working regimes to be investigated of a three-phase transformer with unbalanced sets of parameters for its phases or phases of load, as well as in cases of feeding from a source with an asymmetrical voltage, including a nonsinusoidal one. Taking into into account nonlinearity of magnetization curve at each phase separately allows one to correctly simulate the harmonic composition of currents and voltages.

Voltage Distortion on an Electrical Distribution System

This article described a harmonic analysis study that determined that the proposed midfrequency welder would produce unacceptable voltage distortion on the utility electrical distribution system, especially an adjacent manufacturing facility with extensive electronic controls as well as on the house load associated with the midfrequency welder. The voltage distortion was characterized by significant notching and false zero crossings, both of which could affect electronic control circuits, while the latter could affect timing circuits such as the welder. The article then showed that the installation of line chokes in combination with a fifth harmonic single-tuned filter improves voltage distortion to within acceptable limits. Finally, the article explained that additional enhancements including the use of phase-shifting transformers to achieve a 12pulse or 24-?ulse effective system may entirely eliminate the need for installing a filter. This knowledge of the harmonics nature of the midfrequency welder load and effective harmonic mitigation methods provided valuable data to the welder manufacturer so that changes could be made in the design stage to achieve the utility criteria.