Ocheretnaya Viktoriya
Electrotechnical faculty
Speciality "Electrical Systems and Networks"
The influence of saturation on the totality of electromagnetic parameters of synchronous machines and its consideration in the modeling of transient processes of
Scientific adviser: Arcady Larin
Biography
Abstract on the theme of master's work
Accounting of complex phenomena of magnetic saturation and the displacement current in the array of rotor is a complex problem which is solved in a rigorous approach using the theory of electromagnetic field. [1].Meanwhile, generally accepted that by solving design problems in electrical systems, the permissible error in determining the short circuit current (CC) is adopted at the level of 10%. Synthesis of the equivalent circuit of a substitution synchronous machine (SM) to solve the problem in this case determines the adoption of the following assumptions:
- accounting considered phenomena only in the longitudinal axis of the rotor;
- ensuring
the requirements of accuracy of the calculation short circuit currents
only in the initial stage of the transition process (within the cut-off
time of damage by high-speed relay protections);
- neglect of the
influence of excitation control device that allows to take into account
the influence of displacement current and saturation on the parameters
of equivalent circuits of the rotor without separating them taken into
account of technological functions;
- adoption of
the recorded phase current of stator winding by the analysis of the
initial experimental data of sudden short-circuit as its component
along the longitudinal axis of the rotor synchronous machine.
At the Department of ESIS Don NTU dependences of parameters of the contour, reflecting the impact damper system for turbogenerator TBB-160-2 were obtained. It was assumed equivalent circuit of the longitudinal axis of the rotor, which took into account the various mutual inductive coupling between contours, as shown in Fig. 1.
By receipt of this circuit as a drive winding contour having the greatest time constant was taken.
The influence of satiation was integral estimated by finding of frequency characteristics and parameters of equivalent circuits according to a series of experiments performed at different source voltages. The latter were chosen so that the initial values of the periodic component of the current wine and cognac plant was approximately 2,0 3,0 and 4,0 r.u., but not more than the maximum value of 0.7 Unom regulated in accordance with GOST 10169-77.
Figure 1 - Equivalent Circuit of SM in the longitudinal axis of the rotor resistance, taking into account the scattering of mutual induction between the OECS and the equivalent damping system
The received analytic dependences in this case does not take into account the actual distribution of currents between the drive winding and the equivalent damping system, since the synthesis of equivalent circuits was carried out only on the basis of the adequacy of the input admittance of the stator windings. Therefore, they can be used to account for the influence of satiation on the results of the calculation of the current in the stator winding.[2].
To obtain similar dependences for the correct accounting distribution of currents in the rotor is necessary structural detailing equivalent circuit by allocating circuit winding.[3]. This can be done using the method of synthesis of equivalent circuits, in which the GEW appears independent multiloop circuit.
Figure 2. shows the amplitude and phase frequency characteristics of integrated participation rates, calculated in accordance with (1) and (2) according to the processing of aperiodic currents in the excitation winding for different source voltages.
(1)
(2)
Their analysis indicates that in the frequency of current in the rotor from 0 to 0.01 r.u. they differ among themselves within the measurement error and processing of transition functions. In the same slip of the rotor from 0,1 to 1,0 r.u. holds regular changes of the analyzed characteristics with increasing voltage in the experiments of wine and cognac plant. However, obtaining an analytical coefficient as a function of primary voltage or short-circuit to be able to use in the synthesis of equivalent circuits is difficult.[4].
Figure 2 - Amplitude-phase frequency characteristics of the coefficient of turbogenerator TIA-160-2
It would be better to do it directly for the parameters of equivalent circuits of substitution. Let us analyze the ratio of (3) of the admittance winding scheme made by a branch of the magnetization (Fig. 3) presented in Figure 4.
(3)
Figure 3 - Equivalent Circuit of SM in the longitudinal axis of the rotor made by a branch of the magnetization in the allocation of GEW multiloop circuit.
Figure 4 - Amplitude-phase frequency characteristics of the conduction yf (js) turbo-generator TBB-160-2 1 - at U = 0.25Unom;
2 - at U = 0.47Unom 3 - at U = 0.7Unom
Comparison of characteristics
obtained at
different levels of saturation, shows their practical coincidence of
frequencies from 0 to 0.1 r.u., ie in the area in which there is the
influence of OECS. For large slides holds negligible, within 5-8%
change unit values of the investigated parameter. However, in the rotor
slip, large 0.1 r.u. much more pronounced effect of the damper system.
Figure 5 are obtained by (4) the frequency characteristics of the
equivalent conductance, reflecting the impact of massive structural
elements of the rotor turbine.
(4)
Figure 5 - Amplitude-phase frequency
characteristics of the conduction system of the equivalent damping of
turbogenerator TIA-160-2 yd(js) 1 - at U=0.25Unom; 2 – at U=0.47Unom;
3 – at U=0.7Unom
(animation: volume - 181 kb; size - 857х420; consist of 5 frames; break between frames - 100 мс; break between last and first frames - 100 ms; quantity of cycle reviews - 20)
Analysis of dependencies allows us to establish that the effect of saturation is practically not reflected in changing the properties of the equivalent damping system in sliding less than 0,1 r.u. This means that the circuit parameters having the greatest time constant, almost independent of the initial value of the periodic current stator.[5].
This research demonstrated the feasibility of determining the analytic dependence on short-circuit parameters only one contour, reflecting the influence of the damper system, which has the smallest time constant.If this assumption is independent from the saturation component of the conductivity equivalent circuit T - shaped type is determined by the following relation
If this assumption is
independent from the saturation component of the conductivity equivalent
circuit T - shaped type 
is determined by the
following relation:
(5)
where
-
inductive and active resistance to the first circuit, taking into
account the impact of the massive elements of the rotor in the
experiments performed at a voltage corresponding to the unsaturated
state of the magnetic system of the turbogenerator.
Then the
values of the second damper equivalent circuit can be calculated from
conductivity found from the experimental frequency characteristics: 
[6].
(6)
The parameters of the second damper circuit, corresponding to different levels of open-circuit voltage, are shown in Table 1.
The analysis of dependencies
от
and the initial value of the periodic short-circuit, shown in Fig.6 and
Fig.7, respectively, allowed to obtain analytical expressions for the
dependencies
in the function of stator current with the latest value of more than 1 r.u.
(7)
(8)
where
the values of resistances obtained at a voltage of 0.25 from the nominal.
Figure 6 - Depending on the initial short-circuit current of the active resistance of the second equivalent circuit, the damper system turbine-type TIA-160-2
Figure 7 - Depending on the initial short-circuit current induced drag of the second equivalent circuit, the damper system turbine-type TIA-160-2
Thus, it is shown that for the L-shaped circuit can be established that the parameters of a damper circuit on the initial CS current stator. This would be a mistake to not more than 10 -12% expect transients, taking into account the influence of saturation.[7].
The purpose of my further research is to obtain similar relations for the equivalent circuits of other structures, shown in Fig. 8 and Fig. 9.
Figure 8 - Equivalent Circuit of SM along the longitudinal axis with reference to various mutual inductive coupling between the windings and the representation AVH multiloop circuit
Figure 9 - Equivalent Circuit of SM in the longitudinal axis of the rotor in the presentation of the GW self multiloop circuit
REFERENCES
1. International Electrotechnical Commission (IEC) Standard. Rotating Electrical Machines. Part 4: Methods for determining synchronous machines quantities from tests. Publication 34-4. Geneva, 1985. — 175 p.
2. Машины электрические синхронные трехфазные. Методы испытания. ГОСТ 10169-77. М.:Госкомстандарт СМ СССР, 1977.
3. Казовский Е.Я. Переходные процессы в электрических машинах переменного тока. — М.: Изд-во АН СССР, 1962. — 624 с.
4. Жерве Г.К. Промышленные испытания электрических машин. Л.Энергоатомиздат, 1984. Режим доступа:http://masters.donntu.ru/2002/eltf/tkachenko/diss/lib1.htm
5. Харченко В.А. О разбросе значений параметров синхронной машины, находимых из опыта внезапного короткого замыкания. // Изв. РАН. Энергетика. 1996. №2. С. 127-137.
6. Харченко В.А. Еще раз о разбросе значений параметров синхронной машины, находимых из опыта внезапного короткого замыкания. // Изв. РАН. Энергетика. 1999. №1. С. 142-151
7. Ларин А.М., Рогозин Г.Г. Синтез параметров эквивалентной схемы замещения массивного ротора турбогенератора градиентным методом. / Электричество, 1976, № 11. С.10-13.
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