RU2006124C1 - Method of phase failure and kind of fault detection on power transmission line - Google Patents

Abstract

FIELD: power engineering. SUBSTANCE: emergency components of no-zero phase currents are measured, differential current of each pair is determined and divided by same current as that not included in this pair thereby determining three relative currents; modules of relative currents are compared with minimum and maximum setting currents and reactive components of relative currents are compared with intermediate setting current; if one of modules is below minimum setting current, single-phase fault is stated in phase not included in respective pair; if one module is higher than setting current, two-phase fault is stated in phases included in respective pair; if one of reactive components is between intermediate and maximum setting currents, it means that respective pair of phases is at ground fault. EFFECT: facilitated procedure. 3 cl, 9 dwg

Description

 The invention relates to electrical engineering, specifically to relay protection and system automation, and can be used in distance protection, automatic restart devices, fault locators.

 A known method of selecting damaged phases by measuring the symmetrical components of the currents and comparing them in phase.

 Due to the influence of load currents, especially on the direct sequence, this method is not sufficiently selective.

 To increase the selectivity, emergency current components are determined that are equal to the differences between the currents of the new (emergency) and old (pre-emergency) modes. This method is implemented in a number of devices where emergency components of currents are also used and through their conversion, damaged phases of the power line are identified.

 However, only the angular relations between the purely emergency currents of the forward and reverse sequence do not clearly distinguish between different faults, since small currents of the forward and reverse sequence, due to errors in the corresponding filters, can give a ratio whose argument belongs to any angle sector. Known disadvantages are inherent in the very procedure of separation of direct and reverse sequences. This is the inertia of the filters of symmetrical components and their frequency error.

 A known method for identifying damaged phases, not associated with the separation of direct and reverse sequences, which is also based on the emergency components of the currents, but not on the symmetrical components, but on phase non-zero currents. This method is included as part of a more general method of distance protection, the very concept of non-zero currents and complex equivalent circuits in the system of zero and non-zero components is introduced into the prototype. The specified method for determining damaged phases is to measure the emergency components of non-zero currents and their pairwise transformation. The conversion consists in comparing the measured current modules with each other and with the setpoint.

 However, this conversion is not enough to reliably distinguish all types of faults, in particular, there is no sufficiently clear criterion for distinguishing between phase faults and two-phase earth faults.

The purpose of the invention is to increase the selectivity of the method, i.e., the reliability of determining each of the three possible types of short circuit: single-phase (K ⁽¹⁾ ), two-phase (K ⁽²⁾ ) and two-phase to ground (K ^(1,1) ), and also definitions of damaged phases.

.This is achieved by the fact that the known method for determining the damaged phases and the type of damage to the power line by measuring the emergency components of phase non-zero currents, composing three phase pairs from them and converting the currents of each pair is supplemented by a number of operations that exclude non-selective operation. The essence of the matter lies in the determination of specific quantities called relative currents, for which it seems possible to clearly distinguish between the response areas for different types of short circuits, and these areas are specified in the coordinates of the active and reactive components, i.e., on the complex plane. The sequence of additional operations begins with determining the difference current of each of the three pairs, for which the leading current included in this pair is subtracted from the lagging one. By dividing each difference current by a non-zero current that is not included in this pair, three relative complex currents are determined. These operations form a common part of the proposed method. Subsequent operations are designed to identify primarily a single-phase fault, then interphase and, finally, two-phase to ground. Relative current modules are compared alternately with the minimum setting. If one of them yields to the setpoint (it turns out to be less than it), then a single-phase circuit is detected in a phase whose current does not go into the corresponding pair of currents, giving such a small module. Otherwise, when all modules are above the minimum setting, compare them with another, maximum setting. If one of them exceeds the setting, an interphase closure of the pair of phases that gives such a large module is detected. Finally, if all the modules are between the minimum and maximum settings, the reactive components of the relative currents are compared with the third, intermediate, and, if one of them exceeds it, a ground fault is detected for those phases that are part of the couple that gives the given relative current. Otherwise, we can talk about a three-phase circuit or simply switching three phases. The preferred intermediate setting value is

.

 It is also proposed that instead of comparing the current modules with the settings, a comparison is made with the same settings of the active and reactive components of the currents, while the results of the comparison determining the single-phase circuit are taken into account in the logical circuit AND, and the two-phase circuit according to the OR circuit.

 The main information parameters of the proposed method is the relative currents, which is the ratio of the difference of two non-zero currents to the third non-zero current. Their invariance is manifested in the complete informativeness of each of the three relative currents. This property was first established in this application and previously neither in relay protection, nor in adjacent areas.

и

. Измеряемые величины - токи в начале электропередачи

, ν = A, B, C, где ν - обозначение произвольной фазы линии. Токи в месте повреждения

, равно как и в конце линии, неизвестны.In FIG. 1 shows a schematic model of a power line with an arbitrary short circuit; in FIG. 2 is a schematic model for emergency components of non-zero currents; in FIG. 3 is a schematic model for the emergency component of the non-zero current of only one phase ν; in FIG. 4 is a schematic model of damage during a two-phase earth fault connected to a line circuit for emergency components; in FIG. 5 is a comprehensive network equivalent circuit for emergency components of non-zero values in a two-phase earth fault; in FIG. 6 - response area with three types of circuit; in FIG. 7 is a structural diagram of the proposed method; in FIG. 8 is a diagram of a comparison unit; in FIG. 9 is a diagram of a logical block. A controlled power transmission line 1 connects the transmitting 2 and receiving 3 electrical systems. Damage 4 is an unknown load 4 connected to a line at an unknown location. Electrical systems 2 and 3 contain sources

and

. Measured quantities - currents at the beginning of power transmission

, ν = A, B, C, where ν is the designation of an arbitrary phase of the line. Currents at the site of damage

, as well as at the end of the line, are unknown.

 The structural scheme of the method consists of subtraction blocks 5-10, (subtracters), fundamental harmonics filters 11-13 (filters of orthogonal components), division blocks 14-16, and comparison block 17 having response characteristics (see Fig. 6). This block has two groups of conclusions: conclusions 18 of the signals of a special phase and conclusions 19 of signals of the type of damage, which are the conclusions of the device that implements the proposed method.

Comparison block 17 consists of three identical threshold blocks 20-22 and logic block 23. Each threshold block contains five threshold elements 24-28, of which the first two elements 24 and 25 define the minimum setting η _min , the second two elements 26 and 27 - the maximum setting is η _max and the last element 28 is an intermediate setting of η _mid , as well as logic elements NOT 29-31, AND 32 and 33, OR 34. Logic block 23 consists of six three-input logic elements OR 35-40. The first three elements 35-37 are each connected to the outputs of one of the threshold blocks 20-22, and the second three elements 38-40 are connected to the outputs of the same type of all three threshold blocks. Each threshold block has three outputs corresponding to different types of faults: single-phase K ⁽¹⁾ , two-phase K ⁽²⁾ or two-phase to ground K ^(1,1) , while each threshold block itself corresponds to a certain phase ν = A, B, C.

 The method is based on the following premises.

- комплексы основной гармоники тока произвольной фазы, измеренного в аварийном режиме, а

- ток этой фазы в доаварийном режиме. Аварийная слагающая тока определяется как разность

=

-

. (1)
Безнулевые токи получаются удалением из фазных токов нулевой последовательности

. (2)
Безнулевые токи всех трех фаз уравновешены

+

+

= 0. (3)
Аварийные слагающие безнулевых токов определяются в соответствии с (1) и (2)

=

-

-

; (4)
они также подчиняются соотношению (3).Let be

- complexes of the fundamental harmonic current of an arbitrary phase, measured in emergency mode, and

- current of this phase in pre-emergency mode. The emergency current component is defined as the difference

=

-

. (1)
Non-zero currents are obtained by removing zero sequence from phase currents

. (2)
Non-zero currents of all three phases are balanced

+

+

= 0. (3)
The emergency components of non-zero currents are determined in accordance with (1) and (2)

=

-

-

; (4)
they also obey relation (3).

=

-

, (5) где ν - 1 и ν - 2 - обозначения фаз, отстающей и соответственно опережающей фазу ν , и относительными токами

=

/

. (6)
Соотношение (3) устанавливает следующие взаимосвязи между относительными токами разных фаз

=

,

=

, (7) следовательно, независим только один из относительных токов, а раз так, то он и несет всю имеющуюся информацию о режиме контролируемой сети и в определении двух других токов нет необходимости, разве что для большей надежности распознавания характера повреждения.The proposed method operates with differential currents
Δ

=

-

, (5) where ν - 1 and ν - 2 are the designations of phases lagging behind and correspondingly ahead of phase ν, and relative currents

=

/

. (6)
Relation (3) establishes the following relationships between the relative currents of different phases

=

,

=

, (7) therefore, only one of the relative currents is independent, and if so, it carries all the available information about the mode of the monitored network and there is no need to determine the other two currents, unless for more reliable recognition of the nature of the damage.

. Источниками аварийных слагающих безнулевых токов являются неизвестные токи повреждения

(см. фиг. 2). Схеме, в которой действуют эти токи, присуще важное свойство. Если линия и системы симметричны, то безнулевые токи действуют автономно, т. е. ток

в начале линии определяется только током повреждения

данной конкретной фазы и не зависит от токов других фаз (см. фиг. 3). Отсюда следует, что граничные условия, связывающие безнулевые токи в месте повреждения, автоматически распространяются и на аварийные слагающие безнулевых токов в любом другом месте.Sources of emergency components operate at the site of damage. They can be represented as unknown current sources

. The sources of emergency components of non-zero currents are unknown fault currents.

(see Fig. 2). The circuit in which these currents act has an important property. If the line and systems are symmetrical, then the non-zero currents act autonomously, i.e., the current

at the beginning of the line is determined only by the fault current

this particular phase and does not depend on the currents of other phases (see Fig. 3). It follows that the boundary conditions connecting non-zero currents in the place of damage automatically extend to the emergency components of non-zero currents in any other place.

=

= 0, откуда с учетом (2), (3)

=

= -0,5

, а указанное выше свойство позволяет записать и для токов в начале линии

=

= -0,5

.Since any phase of the line can be special, the notation is introduced: ζ is a special phase; ζ -1 is the phase lagging behind the special one; ζ -2 is the phase ahead of the special one. With a single-phase circuit, boundary conditions

=

= 0, whence, taking into account (2), (3)

=

= -0.5

, and the above property allows you to write for currents at the beginning of the line

=

= -0.5

.

=

-

= 0.In accordance with (5), (6), differential and relative currents are obtained for a single-phase circuit

=

-

= 0.

=

-

= 1,5

. (8)

=

-

= -1,5

= 0,

= -3,

= 3 , что подтверждает общую взаимосвязь между относительными токами (7).

=

-

= 1,5

. (8)

=

-

= -1.5

= 0,

= -3,

= 3, which confirms the general relationship between relative currents (7).

= 0,

= -

, а поскольку

= 0,
то

= 0

= -

, следовательно, и в начале линии должны наблюдаться аварийные слагающие безнулевых токов

= 0

= -

.With two-phase circuit

= 0,

= -

, and since

= 0,
then

= 0

= -

therefore, at the beginning of the line, emergency components of nonzero currents should be observed

= 0

= -

.

= -2

=

(9)

=

∞,

= 1,

= -1, что также согласуется с (7).Accordingly, the difference and relative currents (5), (6) are determined

= -2

=

(9)

=

∞,

= 1,

= -1, which also agrees with (7).

= 0 и равенству (3) отвечает комплексная схема замещения по фиг. 5. В схеме действуют ЭДС, равные напряжениям на соответствующих фазах в доаварийном режиме

=

,

=

. (10)
Напряжения в том режиме симметричны, поэтому

= a

,

=

, (11) где a= expj2 π /3. Кроме того, комплексная схема фиг. 5 содержит входные сопротивления прямой последовательности

и нулевой

, определяемые относительно места повреждения. Они так же неизвестны, как и параметры R_в и R_д, но диапазоны изменения суммарных сопротивлений

=

+R_в,

=

+R_в+3R_д можно очертить, так как его границы поддаются оценке.With a two-phase earth fault, the relationship is more complicated (see FIG. 4). The generally accepted circuit model of damage, consisting of two identical phase resistances R _in and earth R _d . Boundary condition

= 0 and equality (3) corresponds to the complex equivalent circuit of FIG. 5. In the circuit, EMFs equal to the voltages at the respective phases in the pre-emergency mode operate

=

,

=

. (10)
The voltages in that mode are symmetrical, therefore

= a

,

=

, (11) where a = expj2 π / 3. In addition, the integrated circuit of FIG. 5 contains direct sequence input impedances

and zero

defined relative to the place of damage. They are as unknown as the parameters R _in and R _d , but the ranges of variation of the total resistances

=

+ R _in ,

=

+ R _at + 3R _d can be outlined, since its boundaries are measurable.

= -

=

+

= -

+

, l а с учетом условий (10), (11)

=

·

= -

+j

+

= -

-j

+

, где К= К_R+jK₁= K α = Z_0Σ / Z_Σ . (12)
Разностные токи в месте повреждения

= j

/

= -

j

+

, а относительные токи в силу сформулированного выше положения в месте измерения таковы же, как и в месте повреждения.The calculation of the complex equivalent circuit of FIG. 5 gives the following values of non-zero currents at the site of damage

= -

=

+

= -

+

, l and taking into account conditions (10), (11)

=

·

= -

+ j

+

= -

-j

+

, where K = K _R + jK ₁ = K α = Z _0Σ / Z _Σ . (12)
Differential currents at the fault location

= j

/

= -

j

+

, and relative currents, by virtue of the position stated above, at the measurement site are the same as at the damage site.

= j

(1+2

) или с учетом (12)
l_{ζ *}}l ₌

_{+ j}

(13)
a_ζ= R_eI

= -2

K_I
b_ζ= I_m

=

(1+2K_R) (14)
Обращаем внимание на мнимые части комплексов относительных токов. По формулам (7) находим
b_ζ-1= I_m

=

(15)
b_ζ-2= I_m

=

. (16)
В (12) бесспорно лишь то, что K_R>0, так как оба сопротивления

и

- активно-индуктивного характера
0<arg

<90^о, 0<arg

<90^о,
следовательно, из (14)
b_ζ>b_{ζ min}=

. (17)
Значение b_ζmin достигается при K_R= 0. Последнее предполагает, что
arg

= 90^o, arg

= 0, - случай, возможный лишь чисто теоретически. Тем не менее, значение b_ζminнеобходимо знать, чтобы гарантировать минимальный уровень мнимой части относительного тока особой фазы. Как видно из (15), (16), мнимые части двух других относительных токов тоже положительны, но с ростом параметров | К_I| и | K_R| и, следовательно, с ростом также и параметров | a_ζ| и | b_ζ| параметры b_ζ-1 и b_ζ-2 уменьшаются. Значения a_ζ , при которых b_ζ-1 и b_ζ-2 достигают максимума, различаются
b_{ζ - 1}< b_{ζ - 1, max} = 4 / b_ζ (18)
при
a_ζ = -1, (19)
и
b_{ζ - 2} < b_{ζ - 2, max} = 4 / b_ζ (20)
при
a_ζ = 1. (21)
Если, абстрагируясь от реальности, считать К_I произвольной алгебраической величины, а К_R - произвольной положительной величиной, то придется согласиться с тем, что значения (17) и (19) или (21) могут быть достигнуты одновременно, тогда
b_ζ-1,max= b_ζ-1,max= b_max= 4/

= 2.31 и оказывается, что b_max> b_{ζ min} . Тогда в диапазоне значений
1,73<b<2,31 могут находиться мнимые части любого из трех относительных токов. Но в области b>2,31 может оказаться только значение b_ζ , а b_{ζ - 1} и b_{ζ - 2} - ни при каких обстоятельствах. Однако реально mod

> mod

, поэтому mod

= K>1, в связи с чем при K_R= 0 неправомерно считать | K_I | <1. Выясняем, может ли реальное значение b_{ζ - 1} или b_{ζ - 2} достигать уровня

при b_ζ = b_{ζ min} . Из (15) и (16) находим

,
откуда
| a_ζ| ≥ 2
или

K

1/

= 0.578.First one

= j

(1 + 2

) or taking into account (12)
l _{ζ *}} l ₌

_{+ j}

(thirteen)
a _ζ = R _e I

= -2

K _i
b _ζ = I _m

=

(1 + 2K _R ) (14)
We draw attention to the imaginary parts of the complexes of relative currents. By formulas (7) we find
b _ζ-1 = I _m

=

(fifteen)
b _ζ-2 = I _m

=

. (sixteen)
In (12), it is indisputable only that K _R > 0, since both resistances

and

- active-inductive nature
0 <arg

<90 ^o , 0 <arg

<90 ^o
therefore, from (14)
b _ζ > b _{ζ min} =

. (17)
The value of b _{ζmin is} achieved at K _R = 0. The latter suggests that
arg

= 90 ^o , arg

= 0, is a case that is possible only purely theoretically. Nevertheless, the value of b _ζmin must be known in order to guarantee the minimum level of the imaginary part of the relative current of the special phase. As can be seen from (15), (16), the imaginary parts of two other relative currents are also positive, but with increasing parameters | To _I | and | K _R | and, therefore, with the growth of the parameters | a _ζ | and | b _ζ | the parameters b _ζ-1 and b _ζ-2 decrease. The values of a _ζ at which b _ζ-1 and b _ζ-2 reach a maximum differ
b _{ζ - 1} <b _{ζ - 1, max} = 4 / b _ζ (18)
at
a _ζ = -1, (19)
and
b _{ζ - 2} <b _{ζ - 2, max} = 4 / b _ζ (20)
at
a _ζ = 1. (21)
If, abstracting from reality, we consider K _{I as} an arbitrary algebraic quantity, and K _R as an arbitrary positive quantity, then we have to agree that the values (17) and (19) or (21) can be achieved simultaneously, then
b _{ζ-1, max} = b _{ζ-1, max} = b _max = 4 /

= 2.31 and it turns out that b _max > b _{ζ min} . Then in the range of values
1.73 <b <2.31 can be imaginary parts of any of the three relative currents. But in the region b> 2.31, only the value of b _ζ can turn out to be, and b _{ζ - 1} and b _{ζ - 2} - under no circumstances. However real mod

> mod

, therefore mod

= K> 1, and therefore, for K _R = 0, it is unlawful to consider | K _I | <1. We find out whether the real value of b _{ζ - 1} or b _{ζ - 2 can} reach the level

for b _ζ = b _{ζ min} . From (15) and (16) we find

,
where from
| a _ζ | ≥ 2
or

K

1/

= 0.578.

гарантированно разделяет значения параметра b_ζ , который превосходит

, и параметров b_{ζ - 1} , b_{ζ - 2} , которые располагаются ниже этого уровня.For real networks, the latter condition is quite acceptable, therefore, the statement is true that with two-phase earth fault level

guaranteed to share the values of the parameter b _ζ , which exceeds

, and parameters b _{ζ - 1} , b _{ζ - 2} , which are located below this level.

<I

<∞ (24) можно утверждать, что произошло замыкание двух фаз на землю, и ν = ζ . Таким образом, на комплексной плоскости относительных токов зоны разных замыканий четко разграничены (см. фиг. 6): при однофазном замыкании зона локализована в окрестности начала координат, при двухфазном - все точки, достаточно удаленные от начала координат, а при двухфазном замыкании на землю конечная часть плоскости выше уровня j

принадлежит току I $\genfrac{}{}{0ex}{}{\text{′}}{\text{ζ}}$ _*. Что же касается двух других токов, то, хотя их зоны здесь не исследуются, очевидно, что они не захватывают зоны иных замыканий, так как в силу равенств (7) независима лишь зона одного из относительных токов, другие же служат ее конформным отображением.Summing up the results obtained for different types of short circuit, we conclude that the relative current I $\genfrac{}{}{0ex}{}{\text{′}}{\text{ζ}}$ _* at each fault it is located on the complex plane in a certain area where other relative currents do not fall (see Fig. 6). So, discovering that some current I $\genfrac{}{}{0ex}{}{\text{′}}{\text{ν}}$ _* meets the condition
I $\genfrac{}{}{0ex}{}{\text{′}}{\text{ν}}$ _* = 0, (22), in accordance with (8), it can be argued that there is a single-phase circuit with a special phase ζ = ν. Finding that some current I $\genfrac{}{}{0ex}{}{\text{′}}{\text{ν}}$ _* meets the condition
I $\genfrac{}{}{0ex}{}{\text{′}}{\text{ν}}$ _* - >> ∞ (23) should be accepted according to (9) that there is a two-phase circuit with a special phase ν = ζ (phases ν <+><196> 1 and ν - 2 are damaged). And finally, making sure that the imaginary part of the complex current I $\genfrac{}{}{0ex}{}{\text{′}}{\text{ν}}$ _* meet the condition

<I

<∞ (24), it can be argued that two phases were shorted to ground, and ν = ζ. Thus, on the complex plane of the relative currents, the zones of different faults are clearly demarcated (see Fig. 6): in a single-phase fault, the zone is localized in the vicinity of the origin, in two-phase faults, all points are sufficiently far from the origin, and in two-phase fault to the ground part of the plane above level j

belongs to current I $\genfrac{}{}{0ex}{}{\text{′}}{\text{ζ}}$ _* . As for the other two currents, although their zones are not studied here, it is obvious that they do not capture the zones of other faults, since, due to equalities (7), only the zone of one of the relative currents is independent, while the others serve as its conformal mapping.

The implementation of the proposed method (see Fig. 7) solves the problem of identifying the type of circuit and the special phase ζ, based on conditions (22) - (24). The initial operation — the formation of emergency component currents — is shown in the block diagram of FIG. 7 is not reflected. One of the possible implementations of this operation is the subtraction of currents shifted in time by a period. If the pre-emergency mode is periodic, then the result coincides with the emergency component during the first period after the moment of closing t _K3 :
i _{ν p} (t) = i _ν ((t) -i _ν (tT), t _K3 ≅ t <t _K3 + T.

Further, the currents i _Ap , i _Bp , i _{Cp are} considered as input values of the block diagram of FIG. 7. The fourth input quantity is the zero sequence current i _o . The first of the operations performed by this structure is the formation of non-zero currents carried out by blocks 5-7
i $\genfrac{}{}{0ex}{}{\text{′}}{\text{A}}$ _p = i _Ap -i _o , i ^′ _Bp = i _Bp -i _o, i $\genfrac{}{}{0ex}{}{\text{′}}{\text{C}}$ _p = i _Cp -i _o .

= (I^′ _Bp -I^′ _Ap )/I^′ _Cp = a_C+jb_C

= (I^′ _Cp -I^′ _Bp )/I^′ _Ap = a_A+jb_A

= (I^′ _Ap -I^′ _Cp )/I^′ _Bp = a_B+jb_B.The second operation is the selection of the main harmonics of non-zero currents, carried out by filters of 11-13 orthogonal components. Each filter is made with two outputs - according to the number of orthogonal components, and the output values can be represented as complexes
I $\genfrac{}{}{0ex}{}{\text{′}}{\text{A}}$ _p = I $\genfrac{}{}{0ex}{}{\text{′}}{\text{A}}$ _Re + jI $\genfrac{}{}{0ex}{}{\text{′}}{\text{A}}$ _Im i $\genfrac{}{}{0ex}{}{\text{′}}{\text{B}}$ _p = I $\genfrac{}{}{0ex}{}{\text{′}}{\text{B}}$ _Re + jI $\genfrac{}{}{0ex}{}{\text{′}}{\text{B}}$ _Im i $\genfrac{}{}{0ex}{}{\text{′}}{\text{C}}$ _p = I $\genfrac{}{}{0ex}{}{\text{′}}{\text{C}}$ _Re + I ^′ _CIm , where the indices R _e and I _m denote the active and reactive (real and imaginary) components. The third operation is the formation of differential complex currents carried out by four-input blocks 8-10, at the outputs of which signals I appear $\genfrac{}{}{0ex}{}{\text{′}}{\text{B}}$ -I $\genfrac{}{}{0ex}{}{\text{′}}{\text{A}}$ , I $\genfrac{}{}{0ex}{}{\text{′}}{\text{C}}$ -I $\genfrac{}{}{0ex}{}{\text{′}}{\text{B}}$ , I $\genfrac{}{}{0ex}{}{\text{′}}{\text{A}}$ -I $\genfrac{}{}{0ex}{}{\text{′}}{\text{WITH}}$ . The fourth operation is the formation of relative currents carried out by dividing blocks 14-16

= (I ^′ _Bp -I ^′ _Ap ) / I ^′ _Cp = a _C + jb _C

= (I ^′ _Cp -I ^′ _Bp ) / I ^′ _Ap = a _A + jb _A

= (I ^′ _Ap -I ^′ _Cp ) / I ^′ _Bp = a _B + jb _B.

The output signals of blocks 14-16 are the absolute values of the active and reactive components of the relative currents | a _ν | , | b _ν | .

, задаваемой пороговым элементом 28. Если выполняются условия
| a_ν| < η_min, | b_ν| < η_min ,
эквивалентные (22) и означающие однофазное замыкание в фазе ν , то пороговые элементы 24 и 25 формируют на своих выходах сигналы низкого уровня, при этом элементы НЕ 28 и 30 формируют сигналы высокого уровня, которые вызывают срабатывание элемента И 32. Выходной сигнал этого элемента несет, таким образом, информацию об однофазном замыкании с особой фазой ν .The final operations of comparison with the settings are carried out by block 17, where for clarity, each relative current is processed independently, and checks for the presence of each type of circuit are performed in parallel. Each of the signals | a _ν | , | b _ν | compared with the minimum setting η _min specified by the threshold elements 24 and 25, and with the maximum setting η _max given by the elements 26 and 27. In addition, the signals | b _ν | compared with setpoint η _mid =

defined by threshold element 28. If conditions are met
| a _ν | <η _min, | b _ν | <η _min ,
equivalent (22) and meaning a single-phase circuit in phase ν, then the threshold elements 24 and 25 form low-level signals at their outputs, while the elements HE 28 and 30 form high-level signals that cause the And 32 element to operate. The output signal of this element carries Thus, information on a single-phase circuit with a special phase ν.

If there is an interphase closure of the phases ν -1 and ν -2, then at least one of the signals | a _ν | or | b _ν | , as can be seen from (23), reaches a high level, i.e., exceeds the maximum setting η _max . In this case, one of the threshold elements 26 and 27 is triggered, or maybe one and the other. As a result, the OR 34 element is triggered, giving a signal about the two-phase closure of the phases ν -1 and ν -2 (special phase ν). In addition, the signal | b _ν | is compared in element 28 with an intermediate setting η _mid , and therefore this element is activated whenever the condition
| b | > η _mid ,
while giving a signal to one input of the AND 33 element. But to the second input, the signal from the NOT 31 element only comes if the OR 34 element does not work. Thus, the response areas of the elements 34 and 33 are clearly demarcated, the OR element is triggered, if
| and _ν | > η _max or | b _ν | > η _max ,
and the element And, if
η _mid , <| b _ν | <η _max,,
The first is adequate (23), and the second is (24).

 Each threshold block 20-22 gives in itself information about the special phase of the damaged network and, in addition, carries within itself information about the type of damage. If one of the elements 32-34 is triggered inside the threshold block of phase ν, then it is reported that the phase ν is special. This circumstance is revealed by the OR elements 35-37 of the logical block 23. The inputs of each of these elements OR are connected to the outputs of only one threshold block 20-22. In contrast, OR 38-40 elements reveal the type of circuit, for which the inputs of each of these elements are connected to the outputs of all three threshold blocks 20-22 of the same type. Element 38 is triggered if a single-phase circuit occurs in the network, element 39 is two-phase and element 40 is two-phase to ground.

 Thanks to the use of new information parameters - relative currents, which have the property of invariance (the ability of one current to fully characterize the state of the network), the proposed method distinguishes single-phase and two-phase faults without a methodical error, and also identifies damaged phases. The distinction between a two-phase short circuit to ground and without ground, although it is not absolute, which is impossible in principle, can be calculated for any value of the transition resistance by selecting the maximum setting.

 (56) Copyright certificate of the USSR N 610224, cl. H 02 H 3/26, 1976.

 USSR copyright certificate N 1417094, cl. H 02 H 3/26, 1987.

 USSR author's certificate N 1001276, cl. H 02 H 3/26, 1981.

 USSR copyright certificate N 1148071, cl. H 02 7/26, 1983.

 USSR author's certificate N 1374324, cl. H 02 H 3/26, 1986.

 Lyamets Yu. Ya. To the analysis of transients in three-phase circuits by the method of symmetrical components. Electricity, 1988, N 12, p. 57-60.

Claims (3)

 1. METHOD FOR DETERMINING DAMAGED PHASES AND A TYPE OF DAMAGE TO THE ELECTRIC TRANSMISSION LINE by measuring the emergency components of phase non-zero currents, composing three different pairs from them and converting the currents of each pair, characterized in that the difference current of each pair of currents is determined by subtracting the leading current from the lagging one; relative currents by dividing each difference current by a non-zero current that is not included in the corresponding pair, the relative current modules with the minimum setting are compared and, if one of them is set According to the set point, a single-phase short circuit is detected in a phase whose current is not included in the corresponding pair; otherwise, the modules are compared with the maximum set point and, if one of them exceeds the set point, the phase-short circuit of the corresponding phase pair is checked; otherwise, the reactive components of the relative currents are compared with intermediate setting and, if one of them exceeds it, the earth faults of the corresponding phases are detected, otherwise, switching is detected in all three phases. 2. The method according to p. 1, characterized in that the intermediate setting is chosen equal

.  3. The method according to PP. 1 and 2, characterized in that the absolute values of the active and reactive components of the relative currents are compared with the settings and, if the absolute values of both components of one of the currents are inferior to the minimum setting, a single-phase fault is detected in the phase corresponding to this relative current, and if any component of one of the currents exceeds the maximum setting, an interphase closure of two phases corresponding to a given relative current is detected.