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Section 12. Technical sciences
Section 12. Technical sciences Секция 12. Технические науки
Kuprienko Victor Vladimirovitch, Orenburg State University, associate Professor, the Faculty of Electrical Engineering E-mail: ogu15210@mail.ru
About the algorithms of the formation the differential protection’s bias signal
Abstract: The analysis of the algorithms of forming differential protection’s bias signal for the purpose of estimation of stability of functioning in the article. The research was carried out taking into account the saturation current transformers.
Keywords: biased differential protection, bias signal, stability of functioning.
The choice of the method of forming the bias signal (BS) is one of the most important issues for the relay biased differential protection (BDP). Herewith, as a rule, complexity of the circuit realization, dependence of the BS level on the error of the current transformers (CT) and on the short-circuiting (SC) point location (inside or outside the protected area) are considered. BS equal to the arithmetic sum of the side currents, used in serial relay, often does not let to perform the requirements of both selectivity and sensitivity simultaneously. BS equal to the difference between arithmetic and geometric sums of side currents, is studied in a number of works as a more effective as well as deceleration of the maximum and minimum amounts of positive or negative halfwave side currents. Objective conclusion about the effectiveness of a particular type of BS can only be made taking into account all factors that reduce the sensitivity of the differential relay (phase displacement, inequality of side currents, presence of load currents et al.).
This article describes the methodology and results of the study of the relay differential protection operation with different types of BS in steady state at the internal and external SC taking into account the saturation of CT. Options of the steady-state mode are assumed to be equal to the limit values of the transient mode.
At CT saturation in the case of an external SC of BS and therefore rebuilt differential relays which is widely used are significantly reduced. Increasing of biased coefficient (Cb) reduces the sensitivity of the protection. BS variations obtained by combining the phase currents
should be more stable as simultaneous saturation of CT of all three phases is less probably.
Variety of BS. The analysis was performed for relay with the following BS: arithmetic sum (I) and the difference between arithmetic and geometric sums (II) of the side currents with the phase segregated implementation of differential and bias paths; arithmetic sum (III) and the difference between arithmetic and geometric sums (IV) of the side currents of the three phases with the union of differential phase circuits; arithmetic sum (V) and the difference between arithmetic and geometric sums (VI) of the side currents of the three phases with phase-by-phase implementation differential circuits; maximum side current with phase-by-phase implementation differential circuits (VII) and with the union of differential phase circuits (VIII); minimal (IX) and maximal (X) sums of positive or negative half-waves side currents with phase-byphase implementation differential and brake circuits; minimal (XI) and maximal (XII) sums of positive or negative half-waves side currents of the three phases with the union of differential phase circuits; minimal (XIII) and maximal (XIV) sums of positive or negative halfwaves side currents of the three phases with phase-byphase implementation differential circuits. The biasing by circulating current and by components of differential current was not considered as these BS were not spread because of their inherent limitations.
The choice of method study. The stability of the differential relay’s operation is determined by the ratio
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Секция 12. Технические науки
of the differential and bias signals with external SC accompanied by saturation of CT and with internal SC, taking into account a phase shift in the current and protect the side of the currents flowing into the load. Biased coefficient Cb is convenient to use as a parameter characterizing rebuilt of the differential biased relay with external SC. The ratio ofthe C values in modes ofexternal
b
and internal SC can serve as a criterion ofthe stability level under the taken assumptions in design conditions.
The analytical dependence Cb of the CT total error (e) are known. However, due to the fact that differential and bias currents are nonsinusoidal at saturation of CT, expressions are complicated and inconvenient for analysis. Getting specified dependencies taking into account the actual shape of the secondary currents is possible using computing technique that is beyond the scope of this article.
Analytical expressions for the secondary side currents of the differential protection significantly simplifies themselves if we assume that only one side CT are saturated. Considering the fact that this CT have e=1 (which is equivalent to the precipice of the secondary circuit) and CT of other side works without the error, mentioned expression can be greatly simplified because differential and bias currents are sinusoidal. The analysis was performed for a simple two-side differential protection. The expression of relay bias characteristic was used as an original one
Id = I o + Cb1 , (1)
where Id, Ib — currents in the differential and bias circuits of relay respectively when it is activated;
I — current of relay operation in the absence of
biasing.
Comparison BDP rebuilt with different BS with external SC. The ratio of bias coefficients of different BDP relay options is of interest provided equal rebuilt with the external SC. The last one takes place if operating currents in the absence ofbiasing for all relay options are taken as equal.
Phrasing for Cb can be written using (1) and considering the algorithm for forming BS. As an example, the phrasing for I relay variant looks the following way:
У" Ij
j=1 j
Уn Ij
j=i I j
(2)
where n — amount of sides; j — number of differential protection side.
Such formulas determine design calculated bias coefficient (Cb ak), necessary for the detuning from the external SC upon saturation of one, two or three CT. So, for relay with BS I:
C
b calc.
(3)
where I — excitation current of saturated CT;
I2 -secondary current of CT, working without error (acting signification).
Calculated bias coefficient (Cb cak) significations for all considered variants are shown in table 1. The variant II has the lowest built with external SC, and the highest one — V, XIII, XIV. The variants I, VII, IX, X have the most stable C .
b calc.
Table 1. - Comparison of the significances of the bias coefficient of internal and external SC for different relay variants
Kind of bias signal Differential circuits Cb calc. at saturation of CT Cb b lim. C K b calc. Cb lim. at saturation of CT
one two three one two three
I S-P 1,00 1,00 1,00 0,30 3,33 3,33 3,33
II S-P Го Го Го 0,58 ro ro ro
III T-P 0,20 0,50 1,00 0,30 0,67 1,67 3,33
IV T-P 0,25 1,00 ro 0,58 0,43 1,72 ro
V S-P 0,20 0,25 0,33 0,10 2,00 2,50 3,30
VI S-P 0,25 0,50 ro 0,19 1,32 2,63 ro
VII S-P 1,00 1,00 1,00 0,61 1,64 1,64 1,64
VIII T-P 1,00 2,00 3,00 1,83 0,55 1,09 1,64
IX, X S-P 1,00 1,00 1,00 0,46 2,17 2,17 2,17
XI, XII T-P 0,20 0,50 1,00 0,46 0,43 1,09 2,17
XIII, XIV S-P 0,20 0,25 0,33 0,15 1,33 1,67 2,20
Notes: S-P — single-phase differential circuit; T-P — three-phase differential circuit.
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Section 12. Technical sciences
Comparison of BDP’s sensitivity with different BS with internal SC. The level of rebuilt with external SC cannot be used as the one criterion of relay technical perfection. More informed conclusions about the benefits of a particular variant can be made only on the basis of estimates of the relay sensitivity taking into account the load currents and the currents of the phase shift at an sides protection. The phase displacement of side currents with internal SC reduces the differential current. The load current, being a cross-cutting, additionally increases BS.
Dependence of the single-phase differential circuit displacement angle between sides currents (ф) from the ratio of these currents (p) takes the most complete picture of the technical perfection of the differential relay.
It is possible to determine the limiting bias coefficient Ch iim wherein required relay sensitivity, equal for all variants (sensibility coefficient Cs = 2) is provided. The ratio of C . with external SC taking into account the saturation of CT and C under internal SC is sufficiently objective criterion sustainability of BDP.
Differential current
Id - V!гх + IY + 2IxIr cos9, (4)
where IX, IY -acting significations of currents leaking to the SC point from X and Y sources.
On the basis of (1), (4) with the algorithm of BS formation it can be written for variant I
_ [1 .o. + Сы (x + h)] -(X + ly ) (5)
tyj = arccos -
Кxh
The same performance in relative units (IX = 2I —
base current, taking into account the load current, equal
to rated I = I )
= arccos
[c • Cs + CbI (p + 2d +1)] -(p2 +!)
2 p
(6)
Where
p =—; d =IsaL; c = 1-1^-
i 1Y Iy Iy
If the maximum significant of the angle ф, wherein the relay works is equal to the significant of phase-differential protection (PDP), 90 0, limit significant of bias coefficient for the variant I can be determined from (6)
- c • Cs
Cb
p + 2d +1
(7)
The expressions of the form (6) and (7) for other variants are obtained in a similar way. The significants of limiting bias coefficient Ch т (with р = 1, d = 0,5, с = 0,25, Cs = 2) are shown in table 1, dependences of ф (р) (with Cb = Ch iim) — on the picture 1.
As it follows from the data in table. 1, the variant VIII of BDP is the most technically perfect, it is characterized by relatively small significants of the coefficient K and its minor changes in the saturation of the different number of BS. However, as for reasons of ensuring the reliability of operation the single-phase performance of relay is more expedient, the preference should be given to the variant VII. As for variant III, it has the biggest area of sustainable response (pic. 1).
Pic. 1. Dependences of ф (р) for BDP relay with different BS with Cb = Cblim
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Секция 12. Технические науки
Conclusions
1. The comparison of the stability of functioning of relay differential and phase-differential protections in a steady mode should be made taking into account the actual significants of bias coefficient. It guarantees, on the one hand, reliable rebuilt ofprotections from external SC, followed by deep cores saturation of CT and, on the other hand, reliable operation with internal SC taking into account load current and phase displacement between side
currents while providing the same sensitivity of different relay variants.
2. Relay variants III and VII are more technically perfect, at that variant III can be expediently used in cases when saturation ofCT is unlikely and the high sensitivity is required (BDP of reducing transformers, remote from the power supply); variant VII is preferable with a high probability of CT saturation. The BDP relay, performed using variant VII, provides the highest rebuilt with external SC.
Godina Elena Dmitrievna, FGAOU VPO Technical Institute (branch) "North-Eastern Federal University named after MK Ammosova", Neriungri, civil engineering E-mail: godina-elena@mail.ru Ukhanov Alexandr Petrovich, VPO "Penza State Agricultural Academy", Penza
Mustard oil as a diesel biocomponents composite propellant
Abstract: The paper presents the data of the physical properties and the net calorific value of mustard oil and Biomineral based compounds and the results of studies of diesel engine D-243 at work on mustard-fossil fuel as a percentage of 25:75, 50:50, 75:25 and 90:10 in volume and sonicated species.
Keywords: tractor, diesel, fuel analysis, index.
Година Елена Дмитриевна, ФГАОУВПО Технический институт (филиал) «Северо-Восточный федеральный университет имени М. К. Аммосова», г. Нерюнгри E-mail: godina-clena@mail.ru Уханов Александр Петрович, ФГБОУВПО «Пензенская ГСХА», г. Пенза
Горчичное масло как биокомпонент дизельного смесевого топлива
Аннотация: В статье приведены данные физических свойств и низшей теплоты сгорания горчичного масла и биоминеральных композиций, а также результаты моторных исследований дизеля D-243 при работе на горчично-минеральном топливе в процентном соотношении 25:75, 50:50, 75:25 и 90:10 в натуральном и обработанном ультразвуком видах.
Ключевые слова: трактор, дизель, топливо, горчичное масло, анализ, показатель.
Биотопливо — это топливо, из биологического сырья получаемое в результате переработки стеблей сахарного тростника или семян рапса, кукурузы, сои.
Причинами поиска альтернативных видов моторного топлива является ограниченность запасов нефти и природного газа. По прогнозам исследований, в ближайшие 25 лет ожидается резкое падение
их добычи, постоянный опережающий рост тарифов и цен на минеральное топливо и электроэнергию по сравнению с ценами на сельскохозяйственную продукцию. Увеличение численности автотракторной техники обостряет экономические проблемы, связанные с использованием традиционных моторных топлив. Поэтому в последние годы особое
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