Estimation of Quadrature Axis Synchronous Reactance Using the Constant Excitation Test

Bortoni, Edson C.; Araujo, B. T.; Jardini, J.A.

doi:10.1109/jpets.2016.2537274

Cited by 3 publications

(2 citation statements)

References 20 publications

(15 reference statements)

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“…The Constant Excitation Test was introduced in [15] and for a synchronous machine connected to the grid operating as a generator, it consists in performing active power variation, keeping the excitation current constant.…”

Section: The Constant Excitation Testmentioning

confidence: 99%

Estimation of the armature leakage reactance using the constant excitation test

Araujo

Han

Kawkabani

et al. 2016

2016 XXII International Conference on Electrical Machines (ICEM)

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--The adoption of the best available estimate for the stator Leakage reactance is the first step in several equivalent circuit of synchronous machine parameter estimation. However, there is no specific test for its direct measurement. This paper presents a simple and riskless procedure to estimate the Leakage reactance using the information obtained from the Constant Excitation Test. The method theory is described and is applied to several machines from laboratory to hydro power plants. In the absence of absolute values of the Leakage reactance, the estimates are compared to the Potier and sub-transient reactances.Index Terms--Synchronous machines, leakage reactance, parameter estimation. I. NOMENCLATURE E Induced voltage (pu) ILoad current (pu) Quadrature axis synchronous reactance (pu) X l Leakage reactance (pu) Power angle (rad) Power-factor angle (rad) II. INTRODUCTIONHE ARMATURE leakage may be defined as the reactance due to the difference between the total flux produced by an armature current and the flux in the airgap produced by the same armature current. There are a number of components of stator leakage. Each component represents flux paths that do not cross the airgap linking into the rotor.The leakage inductance, or its referred reactance, is the summation of the most pronounced components, commonly referred to as slot, zigzag, belt, skew and end-winding leakage paths, and are well described in [1].The determination of the equivalent circuit parameters of a synchronous machine is strongly dependent of the leakage reactance value; otherwise, an infinity number of circuits could be obtained to represent stator quantities. In fact, no matter which value of leakage reactance is adopted, with consequent variation of the equivalent circuit parameters, that the traditional parameters values will always be preserved. This issue was early pointed in [5] and formally treated in [6][7].Therefore, the great majority of the machine modeling techniques starts with the adoption of the best available estimate for the stator leakage reactance which, in general, is considered as a given or assumed value [2][3][4]. This value is of utmost importance for the machine operation prediction, in both steady and transient states. Though, inappropriate specification of the leakage reactance also implies severe consequences on the saturation evaluation as the mutual reactances will vary accordingly [8].For more than a century, the determination of the leakage reactance have fascinating researchers who work with synchronous machines modeling and parameters determination. This because the leakage reactance is neither easy to calculate nor a direct measurable quantity on the assembled machines. Therefore, many methods and tests for the leakage reactance estimation have been proposed along the years.The Potier reactance has been largely employed as a substitute of the armature leakage reactance. It is obtained from the Potier triangle constructed with information from the open circuit, short circuit, and zero power factor ...

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Section: The Constant Excitation Testmentioning

confidence: 99%

Estimation of the armature leakage reactance using the constant excitation test

Araujo

Han

Kawkabani

et al. 2016

2016 XXII International Conference on Electrical Machines (ICEM)

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“…T O BE able to analyze the transient behavior and dynamics of hydropower plants to ensure power system stability, a precise knowledge of the characteristic quantities of the wound-field synchronous machine (WFSM) is required [2], [3], [4], [5], [6], [7]. Moreover, the estimation of the saturated sub-transient reactances x ′′ d and x ′′ q are essential for calculating the electrical and mechanical integrity of the machine and its shaft line during severe transients such as under three-phase or two-phase short-circuits.…”

Section: Introductionmentioning

confidence: 99%

Evaluating the Precision of the DC Decay Test Method for Characterizing Wound-Field Synchronous Machines in Power Plants

Maurer,

Øyvang,

Nøland

2023

IEEE Open J. Power Energy

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The sudden short-circuit test is the gold standard for determining the equivalent diagram of wound-field synchronous machines (WFSMs). Only a single measurement is needed while the machine is in saturated mode. However, this destructive test can significantly reduce the lifetime of the stator winding. Moreover, determining the equivalent diagram in the q-axis is more complicated and is often not performed. DC-decay tests are low-power alternatives that allow for the determination of the equivalent diagram in both axes without damaging the machinery. Until recently, they required the rotor to be aligned with the axes, which is not feasible in large power plants. A recent breakthrough eliminated the need for rotor alignment by proposing a DC-decay test that can be performed with the rotor in any position. However, numerous independent measurements are needed to obtain the equivalent diagram in both axes. This paper addresses the question of the minimum number of independent measurements needed for the DC-decay test to be practical for industrial use. Around 10 measurements are sufficient for reasonable precision, while 5 of high quality are sufficient using the symmetry of the root locus. Finally, a comparison against the short-circuit test shows that the DC-decay test is a valid alternative.INDEX TERMS DC decay methods, parameter identification, pole estimation, equivalent diagrams, synchronous machines, current measurement, transient analysis, three-phase short-circuit.

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