Question

infinite bus through a step-up transformer Consider a synchronous generator connected to an Given the single phase equivalent circuit information EZS= generator phase to neutral EMF VZ0 infinite bus phase to neutral voltage referred to the generator side of the step-up transformer generator synchronous reactance Zg jX, jX, transformer impedance referred to the generator side of the transformer Z, a) Sketch the capability diagram of a synchronous generator. Label all boundaries and explain their significance. Show clearly the safe operation area (Note: the capability diagram is on the Q-P plane). (70 marks) b) Derive a formula in terms of E, V, Xg and X for the radius of the rotor thermal limit circle which 1 appears on the capability diagram. (70 marks)

Answer 1

sngle EDD Line dingems Lo 9nfiaifebus Gi'scuit So per phase equvatent Ia qmature Cument +serfet]fe eèer ELS Capabikty C4sve P P (mar) steady Sm4t state .s (mas) limit E(maA) 3VE S O O N -P (ts), 9-No ( VAR's) Here om s (VA) MN keypoints Constant Cen tre O adius operation is Grcle S O M. Constant excitation operution cirde o radius wi be 3 VE Constant P opeTation wil lie on atis Parallel to 6o ax as shoon above

enutal minimum operalon Coruponds to he limit Specfied by on the eft Side is from the transient stability 6(mat) from o'. point of vieo. inding So extifed by field Rotor is themal imit deided by field current (muy" (Et) a field Cumnt » Controlled by Ef In the a bove pes phase eguivalent iruit ELS-VLo Ia J(te) infinife to Complex power deli vered bt generatos bus se Pet9e ven by Se VIa means EIS VLo So Comples anjgete Se= V E L8-90y 40 Sea (x So Se, b7---07 ten

So Pe=VE Sin Ye- -v2 cos et v2 VE CoS Squering and adding 2- VE Qet V 2 Pet (+x+ bx equatons beiome - for 3phase the above 2 3 WE Pe + - Se Constant E that So See we -3v2 Centered at Cirue of saduus 3vE Ra tor the maf limit. & this specifis the adius of

Ep (mar) Lous -3v2 aduis 3VE qution of p 93v2 2 3VE