Abstract
The Sen Transformer (ST) provides an economical solution for power flow control and voltage regulation. However, fault analysis and evaluation of the performance of the transmission protection system in the presence of a ST have not been investigated. Hence, a short-circuit model of the ST using the phase coordinate method is proposed in this paper. Firstly, according to the coupled-circuit ST model, the nodal admittance matrix between the sending end and receiving end of the ST was deduced. Subsequently, a fully decoupled mathematical model was established that can reflect three characteristics, including its winding connection structure, electrical parameters, and ground impedance. Thus, with the help of the phase-coordinate-based solving methodology, a short-circuit ST model may be built for various short-circuit faults. The MATLAB and PSCAD/EMTDC software were employed to carry out simulated analyses for an equivalent two-bus system. The short-circuit currents obtained from the time-domain simulation and the analytic calculation utilizing the proposed model reached an acceptable agreement, confirming the simulation’s effectiveness. Moreover, the variation of the fault currents with the variation of the compensating voltage after single-phase-to-ground and three-phase short-circuit faults was demonstrated and used to analyze the effect of the ST on the fault currents.
Highlights
With the rapidly growing penetration of renewable energy sources and the everincreasing complexity of electrical systems, transmission lines are becoming overloaded and experiencing reduced stability, increased voltage variation, and loop-flow of power
The MATLAB and PSCAD/EMTDC software were employed to carry out simulated analyses for an equivalent two-bus system
It may be an effective way to accurately calculate the short-circuit currents when a Sen Transformer (ST) is installed in a power system, with the aid of the phase coordinate method
Summary
With the rapidly growing penetration of renewable energy sources and the everincreasing complexity of electrical systems, transmission lines are becoming overloaded and experiencing reduced stability, increased voltage variation, and loop-flow of power. The electromagnetic transient ST models proposed in the existing literature can be used for short-circuit analysis, the electromagnetic transient calculations are tedious and time-consuming, especially in large-scale and complex power systems. It may be an effective way to accurately calculate the short-circuit currents when a ST is installed in a power system, with the aid of the phase coordinate method. This paper proposes a short-circuit model of the ST, utilizing the phase coordinate method according to the different fault types. MMooddeelliinngg ooff SSTT ffoorr PPhhaassee CCoooorrddiinnaattee MMeetthhoodd. .LLaa,,LLbb,, aannddLLcc ddeennote tthhee sseellff-iinndduuccttaanncceessffoorrththeepprrimimaaryrywwininddininggssininpphhasaessesAA, B, ,Ba,nadndC,Cr,ersepsepceticvtievlye.lyL.aL1,a1L,aL2a,2L, aL3a;3;LLbb11,, LLbb22,, LLb33;; aand LLcc11,,LLcc22, ,aannddLLc3c3ddeennooteteththeesseellff--iinndduuccttaanncceess ffoorr the STT sseeccoonnddaarryy wwiinnddiinnggssiinn pphhaasseessAA,,BB,,aannddCC,,rreessppeecctitviveelyl.yM. Uss’sAs,’AU, sUs’Bs,s’aBn, danUdssU’C sss’tCansdtafnodr ftohretsheeriseesr-iceosn-cnoencnteedctecodmcopmenpseantisnagtinvgolvtaoglteasgfeosr ftohrethtreantrsamnsismsiiossniolinnelinine ipnhpasheasseAs,AB,, Ba,nadnCd,Cr,esrepsepceticvtievlyel.yi.pAip, Aip,B,ipaBn,danipdC irpeCprreepsernestetnhtethexeecxitciintigngcucrurrernetnstfsofrotrhteheSTSTininphpahsaessesAA, B, ,Ba, nadndCC, r,ersepspecetcitvievleyl.y.is’iAs’,Ais,’Bi,s’aBn, danids’Ciss’tCansdtanfodr ftohre tchuerrceunrtrsenotfs tohfethtreatnrsamnsismsiiossniolinnleinaet atht ethreerceeciveiivnigngenedndofofththeeSSTTininpphhaasseess AA,, BB,, aanndd CC,, rreessppeeccttiivveellyy
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