Calculo De La Reactancia De Potier

CONSTRUCTION OF GENERATOR CAPABILITY C CA A T CURVES S
USING THE NEW METHOD FOR DETERMINATION OF POTIER REACTANCE

M.M. Kostić*, M. Ivanović*, B. Kostić*, S. Ilić** and D. Ć Ćirić** Electrical Engineering Institute Nikola Tesla, Belgrade, SERBIA* TPPsTPPs-OCMs "Kostolac", Kostolac, SERBIA **

Abstract
The capability (P-Q) curve of generator can be determined only on (P p plant, the base ofexaminations in the power p , i.e. on the base of: The Potier reactance (XP) for the 3-4 points of the relevant values (X 3of reactive loads are determined, and then the capability (PG-QG ) curve of the generator is being constructed. (P This method is verified for experimental regimes of active and reactive power around the nominal values, on the example of turbo generator 348 MW in power plant"Kostolac B . Kostolac B". The significant deviation in relation to the P-Q curve of the drive manufacturer's documentation generator were established, and it i i is recommended to update P-Q curves every 5-6 years or after d d d 5f major repairs. Similar deviations of P-Q curves were observed during the g extensive testing and research for newer generators in U.S.
the no-load test, i. e. ifl(el)dependence, and nothe reactive load test, i.e. characteristic points Ai (if , u)

Introduction

Capability C bili curves, PG-QG curves, Figure 1, are necessary to the i h operating stuff. The most important part of the curve is the part with coordinates (QG ≥ QG,N, PG ≤ PG,N) which defines the generator regime with increased reactive power. Significant deviations of capability curves,compared to manufacturers’, were obtained during the extensive testing and , g g research for generators in U.S. (Figure 1).

Introduction

Figure 1: Comparison chart of actual capability (P-Q) curves with the manufacturers' generator capability curves (P-

BASIC PRINCIPLES FOR THE DESIGN OF CAPABILITY CURVE
Capabi ity curve of generator Capability cu ve o ge e ato with unsaturated magneticcircuit u sa u a ed ag e c c cu
Generator is sized to reach the nominal temperature at the rated values of (pn) and (qn) p (p (q powers (the point R) i.e.:
for induct currents, ia = ian = Const., φ ≤ φn, Const., and curve if = Const. and φ > φn, i.e., q ≥ qR, with a Const. reduced active power p ≤ pR

Figure 2: Vector diagram of generator electromotive forces and the excitation currents (withcorresponding scaling ratio)

BASIC PRINCIPLES FOR THE DESIGN OF CAPABILITY CURVE
Vector diagrams of excitation currents of saturated machine
The curve of saturated machine, derived from no-load test, if0(e) noIt is particularly difficult to quantify additional magnetic saturation on the p part of the rotor of loaded machine, i.e. ifl = f(el). d d c , . . ( ) Influence of additional saturationof the rotor magnetic circuit is taken into account by introduction of Potier reactance (xP > xl , xl is stator leakage (x reactance) which results in increased EMF (eP = u+xP·i > u+xl i = el ) t ) hi h lt i i d (e + i ).

Figure 3: Magnetization curves if0(e) and ifl(el); diagrams of excitation currents: ifa,n = xd-xP and ifR=ifP+ifa,n

BASIC PRINCIPLES FOR THE DESIGN OF CAPABILITY CURVECapabi ity curve of generator Capability cu ve o ge e ato with saturated magnetic circuit sa u a ed ag e c c cu
The increase part of saturation current
Δif (eP) = Δifu+ Δifs+ Δifr (Figure 3) ( ( g ) beginning point Cuns goes down for Δif(eP) (CR,C1,C2 and CM) the corresponding arches ifi = Const. are moved Const down as well.

Thus, for pure reactive load (p = 0), (p
instead of point q'M, pointqM < q'M is obtained q'M - reactive load maximum for generator with saturated magnetic circuit.

Figure 4: Diagrams of electromotive forces and excitation currents for generator with saturated magnetic circuit

DETERMINATION OF GENERATORS POTIER REACTANCE
Potier reactance is not constant in given range of voltage and load. It is necessary to determine the Potier reactance dependence...