RU2037246C1 - Method of detection of injured phase and failure zone of power line - Google Patents

Abstract

FIELD: relay protection, automatics. SUBSTANCE: method is based on check of mutual power of three values: measured voltage, reference current and predicted voltage related to end of protected zone. Three pairs are formed from three values. In prototype only two of them are monitored which leads to loss of selectivity if injured phases are unknown in advance. Deficiency of prototype is corrected by determination of sign of mutual reactive power of two mentioned voltages and in proper cases of their mutual active power too. Adaptations of method differ by character of formation of comparable values and measures called for to enhanced its sensitivity and remove "blind zone" in case of close short-circuits. EFFECT: enhanced sensitivity of detection of injured phase and failure zone. 17 cl, 5 dwg

Description

 The invention relates to electrical engineering, namely to relay protection and automation, and can be used in distance protection and selectors of damaged phases.

Many remote methods of relay protection can be divided into two groups [1, p. 147] A distinctive feature of the first group is the specification of the response characteristics on the complex plane. The characteristics remain unchanged for all types of damage, which reduces the functionality of such methods. The methods of the second group possess more general properties, the functioning algorithms of which are not associated with clearly defined characteristics. This group includes methods for constructing multiphase resistance relays, in particular, the Bresler relay [1, p.165, 166] and also the earth-fault relay [1, p.168] All these methods are based on certain patterns of location of a certain number voltage and current vectors, some of which are measured, and the other is determined by converting the former. Measuring bodies constructed by such methods are included in the theory of relay protection under the name of multiphase (three-phase) [2, p. 89-98] These methods and the corresponding measuring organs have a limited scope, acting with well-defined types of damage. So, the Bresler relay operates with two-phase faults, and the Suyar relay [3, p. 121] with earth faults. The methods do not have a common information base, i.e. a single sign that distinguishes a short circuit in the zone from short circuits outside the zone and "behind" (in the opposite direction from the point of observation). They operate with a different number of input quantities: the Bresler relay with three compensated line voltages (currents are not involved), and the Suyar relay with three compensated phase voltages and a zero-sequence current. Known disadvantages of each of them, in particular, the Suyar relay gives excessive tripping when external short circuits and relatively small angles between the EMF at the ends of the line [3, p.136]
The most common distance protection method is known, which also belongs to the second group [4]. It is based on the only and indisputable information sign of a short circuit to the resistive nature of damage, therefore, all private information signs and methods based on them and their implementation, including Bresler relay, and Suyar's relay, follow from it as special cases. In addition to the obvious operations of measuring voltages and currents at the beginning of the line and their components (zero and reverse sequence, non-zero components [4] of the choice of a particular phase, this method includes the conversion of the measured values into three groups of quantities. The first correspond to the voltage at the beginning of the line, the second to voltage at the end of the controlled area, provided that the line is not damaged.The third values are basic, and can vary depending on the type of damage. Two parameters are determined by the formed values as mutual eaktivnuyu power of the first and third and, respectively, second and third values, and then comparing their signs. It is proved that in case of damage parameters opposite signs zone [4]
If this method is implemented in its most complete form, then the parameters are the three-phase reactive power of the damage, assumed once at the beginning and the other at the end of the protected zone. Then the method is free from methodological error. However, in such a complete form, it can not always be implemented. Firstly, it is not always possible to set more or less realistically the parameters of the receiving system. Secondly, when choosing the alleged damage currents as reference values, a lot of operations have to be performed related to the determination of linear currents to the right of the damage location. It is possible to resort to simpler reference values in the form of linear current components to the left of the damage site, but it is necessary to first identify the type of damage. In case of earth faults, such a simple reference value could, for example, be a zero sequence current.

 Another drawback of the full (three-phase) form of this method is that as a result of its application, a damage zone is determined, which may be sufficient for distance protection, but the type of damage and damaged phases remain unknown, which is necessary for phase voters and generally represents valuable information about the state of the monitored line.

If this method is used to protect the line from earth faults, it would seem that it is possible to simplify it by reducing the number of operations and choosing the zero sequence current as the reference value, but this poses a serious problem. The first and second parameters are determined differently depending on the type of circuit of a single-phase (K ⁽¹⁾ ) and two-phase to ground (K ^(1,1) ), and it may happen that with a single-phase circuit outside the zone, signs of a two-phase in the zone are detected ( different signs of the corresponding parameters), and vice versa. In other words, the known method has the disadvantage that, when simplified, it loses selectivity.

 The purpose of the invention is the elimination of this drawback, i.e. the construction of a simple and at the same time selective method for determining the damaged phases and the damage zone of the power line.

 This goal is achieved by the fact that to the known operations of measuring voltages and currents at the beginning of the line and their components, selecting a particular phase, converting the measured values to first values corresponding to voltages at the beginning of the line, second values corresponding to voltages at the end of the controlled area of the undamaged line, and in the third reference quantities, the definition of the first parameter as the mutual reactive power of the first and third quantities and the second parameter as the mutual reactive power of the second and third quantities, is compared When the signs of two parameters are added, the following operations are added: determining another, third parameter as the mutual reactive power of the first and second quantities, comparing the signs of the third parameter with the signs of the first and second parameters, and if the signs of the first and third parameters coincide and are opposite to the sign of the second parameter, which is detected logical operations, then there is a fixation of damage in the controlled area.

 For even greater reliability of distinguishing faults of one type in the zone from faults of another type outside the zone, it is additionally proposed to define the fourth parameter as the mutual active power of the first and second quantities, compare the signs of all four parameters and fix the damage in the zone when the first parameter is positive, and three others are negative. In addition, it is proposed to generate fourth values proportional to the components of the measured voltages and fifth values proportional to the components of the measured currents, and define the fifth parameter as the mutual reactive power of the fourth and fifth values and record damage in the zone only with a negative sign of the fifth parameter.

 To reliably eliminate the “dead zone” of insensitivity to close short circuits, possible when the signs of the first and second parameters coincide, it is proposed in cases where the signs of the third parameter are opposite to them, compare the absolute values of the first and second parameters and fix the damage in the controlled area, if absolute prevails value of the second parameter.

 The remaining proposals relate to the specification of the quantities used. So, as the first values, phase voltages at the beginning of the line can be used, as second phase voltages at the end of the zone, determined on the assumption that the line is not damaged, as third currents of the alleged damage.

 The diagram in figure 1 illustrates the properties of a function whose values play the role of two main parameters; figure 2 structural diagram that implements the proposed method; figure 3 its fragment indicating the values supplied when checking the assumption of a single-phase short circuit; figure 4 full conditions for the operation of distance protection, functioning by the proposed method; figure 5 reveals the contents of the quantities that determine the operation with different types of short circuits.

 Figure 1 shows the transmitting and receiving systems 1 and 2, connected by a power line 3, the damage of which is simulated by a transition resistance 4.

 The block diagram consists of filters of orthogonal components 5-12, the inputs of which are connected to voltage and current transformers, forming blocks 13-15, the purpose of which is to predict the voltage at the end of the monitored zone, a reverse sequence current filter 16, combined switching 17 and summing 18 blocks, sensors reactive power 19-22, an active power sensor 23 and a logical unit 24. The circuit also possibly includes a unit for selecting a special phase 25 and a comparison unit 26.

(O)

(O_)

,

(O)

,

(O)

соответствующие комплексы основной гармоники,

(l)

,

(l-)

,

(l)

,

(l-)

предполагаемые величины конца защищаемой зоны, недоступные наблюдению и представляющие собой результат преобразования наблюдаемых величин

,

. Взаимные мощности двух величин
σ_s= σ(o) Im(

) (1)
σ_r= σ(l) Im(

) (2)
σ_u= Im(

) (3)
ρ_u= Re(

) (4)
Q Im(

) (5) где

общее обозначение опорного тока, в качестве которого могут выступать различные составляющие,

сопряженный комплекс.Further, when describing the method, the following notation of electrical quantities is used: x is the coordinate of the point of the power line, ν A, B, C is an arbitrary phase, ζ is a special phase, ζ -1 is lagging and ζ -2 is ahead of a particular, U _ν (x, t), i _ν (x-, t) instantaneous values of voltages and currents at an arbitrary point on the line: U _νs = U _ν (0, t), i _νs i (0, t) observed values at the beginning of the line with coordinate x 0; xl coordinate of the end of the protected zone, U _os , i _{os the} observed voltage and zero sequence current,

(O)

(O_)

,

(O)

,

(O)

corresponding complexes of the fundamental

(l)

,

(l-)

,

(l)

,

(l-)

supposed values of the end of the protected zone, inaccessible to observation and representing the result of the conversion of the observed values

,

. Mutual powers of two quantities
σ _s = σ (o) Im (

) (1)
σ _r = σ (l) Im (

) (2)
σ _u = Im (

) (3)
ρ _u = Re (

) (4)
Q Im (

) (5) where

general designation of the reference current, which can be various components,

conjugate complex.

(x_f) R

(x_f) (6) Иначе
Im[

(x_f)

(x_f)] 0 (7) Если ввести целевую функцию
σ(x) Im[

(x)

(x)] (8) и рассмотреть ее поведение в разных точках линии, то обнаружится, что для линий с реальными параметрами функция (8) пересекает ось х в единственной точке х x_f, как этого требует условие (7). Следовательно, знаки значений, принимаемых целевой функцией в начале и конце линии, противоположны:
sing σ_s≠ sing σ_r. (9) Значения σ_s и σ_r представляют собой реактивные параметры (1) и (2).The inventive method, like the prototype, is based on the only premise of the resistive nature of the damage. As applied to a two-wire line 3 damaged at an unknown point xx _f , this means that the voltage and current complexes in the damage itself are connected by an unknown, but obviously real, resistance R _f

(x _f ) R

(x _f ) (6) Otherwise
Im [

(x _f )

(x _f )] 0 (7) If you introduce the objective function
σ (x) Im [

(x)

(x)] (8) and consider its behavior at different points of the line, it turns out that for lines with real parameters, function (8) intersects the x axis at a single point x x _f , as required by condition (7). Therefore, the signs of the values accepted by the objective function at the beginning and end of the line are opposite:
sing σ _s ≠ sing σ _r . (9) The values of σ _s and σ _r are the reactive parameters (1) and (2).

Im[

(x_f)

(x_f)] 0 (10)
σ(x)

Im[

(x)

(x)] (11) и свойство (9) при этом сохраняется.In a three-phase power transmission, property (7) and, accordingly, the objective function are generalized as follows

Im [

(x _f )

(x _f )] 0 (10)
σ (x)

Im [

(x)

(x)] (11) and property (9) is preserved.

(x_f) в (7) желательно ввести иную величину, достаточно близко совпадающую с ним по фазе, но определяемую без привлечения параметров приемной системы. Это можно сделать, если учесть, что по своей природе

(x_f) чисто аварийный ток повреждения (аварийная слагающая). Аварийная слагающая

произвольного тока IDot есть разность

-I_n, где

доаварийный ток (ток предшествующего режима). В повреждении

(x_f) 0. Взаимосвязь между током

(x_f) и аварийной слагающей тока в месте наблюдения

(0-)=

не зависит от переходного сопротивления. Так как активное сопротивление линии несравненно меньше индуктивного, то
arg

arg

(x_f) (12) Если учесть к тому же, что параметры линии известны и аргумент тока

может быть скорректирован, то равенству (7) можно поставить в соответствие почти столь же точное
Im[

(x_f)

] 0 (13) Соответственно изменится и функция (8)
σ(x) Im[

(x)

] (14)
Аварийная составляющая напряжения

(x_f) представляет собой реакцию на воздействие тока повреждения

(x_f). При слабом влиянии активного сопротивления
arg[-j

(x_f)] ≈ arg

(x_f), что модифицирует критерий 7
Im[

(x_f)j

(x_f)] Re[

(x_f)

(x_f)] 0 (15) и функцию (8)
σ(x) Re[

(x)

(x)] (16)
Трехфазный критерий (10) может быть преобразован аналогичным образом. Введем в рассмотрение безнулевые величины

-

,

-

где

,

, напряжение и ток нулевой последовательности, учтем, что

0,

0 в силу чего

(x)

(x)

(x)

(x)+3

(17) и критерии (10) принимает вид

Im[

(x_f)

(x_f)]+3Im[

(x_f)

(x_f)] (18)
При междуфазных коротких замыканиях двухфазном К⁽²⁾ или трехфазном К⁽³⁾, когда

=0, (18) упрощается

Im[

(x_f)

(x_f)] 0 (19) Если допустимо принять, что влияние активного сопротивления линии невелико, то
arg

(x_f) ≈ arg

(0-) (12a) и обозначая

(0-)=

, можно заменить (20) на еще более простое

Im[

(x_f)

] 0 (13a) что приводит к целевой функции
σ(x)

Im[

(x)

] (14a) С другой стороны, имея в виду, что
arg

(x_f) ≈ arg

(x_f)-π/2 можно придать (20) форму

Im[

(x_f)j

(x_f)] 0 (18)

Re[

(x_f)

(x_f)] 0 (18a) вводя затем соответствующую целевую функцию
σ(x)

Im[

(x)j

(x)] (19)
Если предварительно определить вид короткого замыкания, то трехфазные критерии и целевые функции можно будет заменить столь же простыми выражениями, как (13)-(16), придав им общую форму (7), (8), а далее
Im[

(x_f)

] 0 (20)
σ(x) Im[

(x)

] (21) Так, при однофазном замыкании с особой фазой ζ в месте повреждения выполняются граничные условия

(x_f)

(x_f) 0 (22) упрощающие критерий (10) и функцию (11)
Im[

(x_f)

(x_f)] 0 (23)
σ⁽¹⁾(x) Im[

(x)

(x)] (24) Из (22) вытекают, кроме того, взаимосвязи между составляющими нулевой, прямой, обратной последовательностей и безнулевыми составляющими

(x_f)

(x_f) -

(x_f)

3

(x_f) позволяющие заменить в (23), (24) ток

(x) любой из составляющих

(x),

(x),

(x),

(x). Если принять по аналогии с (12)
arg

arg

(x_f) (25)
arg

≈ arg

(x_f) (26)
arg

≈ arg

(x_f) (27) то из (23)-(27) последуют выражения типа (20), (21), где под

всегда будет подразумеваться

а под током

одна из составляющих

или

, или

' (фиг.5).The determination of currents in the damage itself is complicated by the fact that the parameters of the receiving system 2 can only be set approximately. Therefore, instead of current

(x _f ) in (7), it is desirable to introduce a different quantity that is close enough in phase coincidence with it, but determined without involving the parameters of the receiving system. This can be done, given that by nature

(x _f ) purely emergency fault current (emergency component). Emergency component

arbitrary current idot there is a difference

-I _n where

pre-emergency current (previous mode current). In damage

(x _f ) 0. Relationship between current

(x _f ) and the emergency component of current at the observation site

(0 -) =

independent of transient resistance. Since the line resistance is incomparably less than inductive, then
arg

arg

(x _f ) (12) If we take into account the fact that the line parameters are known and the current argument

can be adjusted, then equality (7) can be matched with almost equally accurate
Im [

(x _f )

] 0 (13) The function (8) will change accordingly
σ (x) Im [

(x)

] (14)
Emergency voltage component

(x _f ) is a response to the effects of fault current

(x _f ). With a weak effect of active resistance
arg [-j

(x _f )] ≈ arg

(x _f ), which modifies criterion 7
Im [

(x _f ) j

(x _f )] Re [

(x _f )

(x _f )] 0 (15) and function (8)
σ (x) Re [

(x)

(x)] (16)
Three-phase criterion (10) can be converted in a similar way. We introduce nonzero quantities

-

,

-

Where

,

, voltage and zero sequence current, we take into account that

0

0 by virtue of which

(x)

(x)

(x)

(x) +3

(17) and criteria (10) takes the form

Im [

(x _f )

(x _f )] + 3Im [

(x _f )

(x _f )] (18)
With interphase short circuits, two-phase K ⁽²⁾ or three-phase K ⁽³⁾ , when

= 0, (18) simplifies

Im [

(x _f )

(x _f )] 0 (19) If it is acceptable to accept that the influence of the line resistance is small, then
arg

(x _f ) ≈ arg

(0-) (12a) and denoting

(0 -) =

, we can replace (20) with an even simpler one

Im [

(x _f )

] 0 (13a) which leads to the objective function
σ (x)

Im [

(x)

] (14a) On the other hand, bearing in mind that
arg

(x _f ) ≈ arg

(x _f ) -π / 2 can be given (20) the form

Im [

(x _f ) j

(x _f )] 0 (18)

Re [

(x _f )

(x _f )] 0 (18a) then introducing the corresponding objective function
σ (x)

Im [

(x) j

(x)] (19)
If you preliminarily determine the type of short circuit, then the three-phase criteria and objective functions can be replaced by as simple expressions as (13) - (16), giving them the general form (7), (8), and then
Im [

(x _f )

] 0 (20)
σ (x) Im [

(x)

] (21) So, with a single-phase circuit with a special phase ζ at the fault location, the boundary conditions

(x _f )

(x _f ) 0 (22) simplifying criterion (10) and function (11)
Im [

(x _f )

(x _f )] 0 (23)
σ ⁽¹⁾ (x) Im [

(x)

(x)] (24) From (22), in addition, the relationships between the components of the zero, direct, reverse sequences and non-zero components

(x _f )

(x _f ) -

(x _f )

3

(x _f ) allowing to replace the current in (23), (24)

(x) any of the components

(x)

(x)

(x)

(x). If we take by analogy with (12)
arg

arg

(x _f ) (25)
arg

≈ arg

(x _f ) (26)
arg

≈ arg

(x _f ) (27) then expressions of the type (20), (21) follow from (23) - (27), where under

will always be implied

and under current

one of the components

or

, or

'(Fig. 5).

(x_f) 0
arg[

(x_f)-

(x_f)] arg[

(x_f)-

(x_f)] (28)
arg[

(x_f)-

(x_f)] arg

(x_f) (29) или

(x_f)

(x_f)+

(x_f)-

(x_f)
(30)
arg[

(x_f) arg[j

(x_f)+

(x_f)/2)]
Соотношения (25), (29) дают основание записать функцию того же вида, что и (21)
σ^(1,1)(x) Im[

(x)

] (31) при

(x)

(x)+

(x)
Хотя соотношения (25), (26), взятые в совокупности, и не означают столь же близкого совпадения аргументов суммы

(x_f)+

(x_f)/2 и

+

/2, все же из-за преобладающего влияния в той сумме тока обратной последовательности такое совпадение практически можно допустить, получая функцию (21) при

(x)

(x),

= j(

+

/2). Если же этого допустить нельзя, то от (21) придется вернуться к более общей функции (8), определяя

(x) как j(

(x)+

(x)/2 при

(x)

(x-)-

(x+)

(x+)

(x)/

(x+)

(x+)

(x-)-

(x+)

(x+)

(x)/

(x+) где смысл токов с аргументом (х+) ясен из фиг.1, а сопротивления с аналогичным аргументом определяются по усредненным параметрам принимающей системы 2.In a two-phase earth fault with a symmetrical nature of damage to the phases ζ-1 and ζ -2, the boundary conditions

(x _f ) 0
arg [

(x _f ) -

(x _f )] arg [

(x _f ) -

(x _f )] (28)
arg [

(x _f ) -

(x _f )] arg

(x _f ) (29) or

(x _f )

(x _f ) +

(x _f ) -

(x _f )
(thirty)
arg [

(x _f ) arg [j

(x _f ) +

(x _f ) / 2)]
Relations (25), (29) give reason to write down a function of the same form as (21)
σ ^(1,1) (x) Im [

(x)

] (31) with

(x)

(x) +

(x)
Although relations (25) and (26) taken together do not mean the same close coincidence of the arguments of the sum

(x _f ) +

(x _f ) / 2 and

+

/ 2, nevertheless, due to the prevailing influence in the sum of the current in the negative sequence, such a coincidence can practically be allowed to obtain function (21) for

(x)

(x)

= j (

+

/ 2). If this cannot be allowed, then it will be necessary to return from (21) to a more general function (8), defining

(x) as j (

(x) +

(x) / 2 for

(x)

(x -) -

(x +)

(x +)

(x) /

(x +)

(x +)

(x -) -

(x +)

(x +)

(x) /

(x +) where the meaning of the currents with the argument (x +) is clear from Fig. 1, and the resistances with a similar argument are determined by the averaged parameters of the receiving system 2.

 The values of the two-phase circuit follow from the previous one as a special case (Fig. 5). And with a symmetric three-phase circuit, you can limit yourself to the results of monitoring one of the phases (Fig. 5), using criterion (13) and function (14).

,

и

иллюстрируют правило знаков. Возможны, хотя и разновероятны, пять вариантов, каждому из которых в таблице отведена отдельная колонка. Заметим, что из трех величин две измеряемые (

и

), а третья получаемая путем преобразования этих двух и других измеряемых величин. Примем для определенности, что проверяется гипотеза об однофазном замыкании с особой фазой А и для этого используется целевая функция
σ $\genfrac{}{}{0ex}{}{\text{(}}{\text{A}}$ ¹⁾(x) Im[

(x)

] Тогда подлежат определению знаки трех реактивных и, может быть, еще одного активного параметра
1) σ $\genfrac{}{}{0ex}{}{\text{(1}}{\text{AS}}$ ⁾ σ $\genfrac{}{}{0ex}{}{\text{(}}{\text{A}}$ ¹⁾(O) Im[

(O)

] Im[

]
2) σ $\genfrac{}{}{0ex}{}{\text{(1}}{\text{Ar}}$ ⁾ σ $\genfrac{}{}{0ex}{}{\text{(}}{\text{A}}$ ¹⁾(l) Im[

(l)

] Im[

]
3) σ $\genfrac{}{}{0ex}{}{\text{(1}}{\text{Au}}$ ⁾ Im[

(O)

(l)] Im[

]
4) σ $\genfrac{}{}{0ex}{}{\text{(1}}{\text{Au}}$ ⁾ Re[

(O)

(l)] Re[

] Входящие в эти выражения величины

и

измеряются непосредственно. Что же касается величины

, то она измерению недоступна и определяется в предположении, что линия не повреждена во всей контролируемой зоне или, иначе говоря, повреждение может иметь место только на границе зоны. Если не учитывать распределенную емкость линии, то

=

-(

+

)l (32) а с учетом емкости

=

ch

l-Z

sh

l+

ch

l-

sh

l (32a) где

и

удельные сопротивления прямой и нулевой последовательностей,

-

,

безнулевые ток и напряжение фазы А,

,

-коэффициенты распространения прямой и нулевой последовательности,

=

=

характеристические сопротивления.The above theoretical justification of the proposed method shows that various modifications are possible. So, applying the three-phase objective functions, it is possible to determine the damage zone regardless of the type of damage and the damaged phases. But this would be a trivial approach, not giving complete information about the state of the power line. The task is to determine not only the zone, but also the type of short circuit. If we single out the definition of a special phase as an independent task, then the following most general task is assigned to the proposed method. There is a ground fault, as evidenced by, for example, a sufficiently high level of current or voltage of the zero sequence. In one way or another, a special phase ζ has been identified. It is required to establish whether a fault has occurred in the controlled area, and also to determine the type of fault (K ⁽¹⁾ ) or K ^(1,1) ) and thereby indicate the damaged phases: ζ at K ⁽¹⁾ ; ζ -1 and ζ-2 at K ^(1,1) . When solving this problem, there are problems associated with the fact that the signs of closure of one species that occurred outside the zone may coincide with the signs of closure of another species that occurred in the zone. These problems are solved by introducing logical operations for comparing the characters indicated in FIG. 4. The vector diagrams shown in the same place

,

and

illustrate the rule of signs. Five variations are possible, although unlikely, each of which has a separate column in the table. Note that of the three quantities, two are measurable (

and

), and the third is obtained by converting these two and other measured quantities. For definiteness, we assume that the hypothesis of a single-phase circuit with a special phase A is tested and the objective function is used for this
σ $\genfrac{}{}{0ex}{}{\text{(}}{\text{A}}$ ¹⁾ (x) Im [

(x)

] Then the signs of three reactive and maybe one more active parameters are to be determined
1) σ $\genfrac{}{}{0ex}{}{\text{(1}}{\text{As}}$ ⁾ σ $\genfrac{}{}{0ex}{}{\text{(}}{\text{A}}$ ¹⁾ (O) Im [

(O)

] Im [

]
2) σ $\genfrac{}{}{0ex}{}{\text{(1}}{\text{Ar}}$ ⁾ σ $\genfrac{}{}{0ex}{}{\text{(}}{\text{A}}$ ¹⁾ (l) Im [

(l)

] Im [

]
3) σ $\genfrac{}{}{0ex}{}{\text{(1}}{\text{Au}}$ ⁾ Im [

(O)

(l)] Im [

]
4) σ $\genfrac{}{}{0ex}{}{\text{(1}}{\text{Au}}$ ⁾ Re [

(O)

(l)] Re [

] The quantities in these expressions

and

measured directly. As for the value

, then it is unavailable to measurement and is determined under the assumption that the line is not damaged in the entire controlled area or, in other words, damage can only occur at the border of the zone. If you do not take into account the distributed line capacity, then

=

- (

+

) l (32) and taking into account the capacity

=

ch

lZ

sh

l +

ch

l-

sh

l (32a) where

and

resistivities of direct and zero sequences,

-

,

non-zero current and phase A voltage,

,

- propagation coefficients of the direct and zero sequence,

=

=

characteristic resistance.

, определяемое путем преобразований (32), является прогнозируемой величиной и, как правило, не имеет ничего общего с реальным, недоступным измерению напряжением в конце зоны. Допустим, речь идет о защите магистральной электропередачи, как это показано на фиг.1. Тогда угол сдвига
δ arg

-arg

между измеряемым напряжением

и неизвестным истинным напряжением в конце линии

по условиям устойчивости не может превышать (по абсолютной величине) 90^о, практически жеδ|< 60^о.Voltage

determined by transformations (32) is a predicted value and, as a rule, has nothing to do with the real, inaccessible measurement of voltage at the end of the zone. Suppose we are talking about the protection of the main power transmission, as shown in figure 1. Then the shear angle
δ arg

-arg

between measured voltage

and unknown true voltage at the end of the line

under stability conditions it cannot exceed (in absolute value) 90 ^о , practically δ | <60 ^о .

и предсказанной величиной

arg

-arg

Когда линия не повреждена, предсказанная величина совпадает с истинной (

=

) и

δ. Но для поврежденной линии преобразования (32) дадут формальный, хотя и несущий в себе полезную информацию, результат и поскольку при этом

≠

,

≠ δ, то вполне вероятно, что

| превысит 90^о, а сам угол δHat не поддается предварительной оценке. Так, при металлическом трехфазном замыкании ток

отстает от напряжения

почти на 90^о и, следовательно преобразование

=

-jX

даст результат, вообще находящийся в противофазе с величиной

. Подобное явление встречается и при иных видах замыканий. Существенно, однако, что взаимное расположение векторов

,

и

тем не менее не произвольно, а подчиняется закономерностям, вытекающим из условия (7). Прежде всего, это закономерность (9), означающая, что при коротком замыкании в контролируемой зоне вектор опорного тока

располагается между векторами напряжений

,

, причем опережающим может быть как вектор

, так и

Однако для селективного определения зоны повреждения одного этого условия недостаточно. Необходимы дополнительные признаки повреждения в зоне. Они существуют и заключаются в следующем. При малых переходных сопротивлениях, когда замыкание близко по своей природе к металлическому, вектор

заведомо опережает и наблюдаемый ток

, и прогнозируемое напряжение

. Даже при обратном направлении мощности доаварийного нагрузочного режима ( δ< 0), данное положение сохраняет свою силу ввиду ограниченности модуля угла δ Тем более оно справедливо для прямой передачи мощности, когда при больших значениях δ может встретиться редкий случай

> 180^о (вариант 3, фиг.4). Все же наиболее типичен вариант 1, когда 0 <

< 180^о. При отрицательном истинном угле предсказанный угол

может быть как положителен, так и отрицателен (вариант 2), но при этом непременно

> δ δ, так как индуктивная аварийная слагающая тока смещает вектор

в отстающем направлении относительно истинного вектора

. Чтобы распознать вариант 1, достаточно сопоставить знаки трех реактивных параметров σ_s,σ_r и σ_u. Связанные с большим числом ограничений варианты 2 и 3 выявляются только с помощью дополнительного активного параметра ρ_u. Пятый, тоже реактивный параметр Q повышает надежность распознавания повреждений в защищаемой зоне и "за спиной", т.е. левее места наблюдения. Повреждению в зоне соответствует отрицательное направление реактивной мощности величин, источник которых располагается в месте повреждения. Эти величины перечислены на фиг.5. Располагая информацией о знаке параметра Q, можно полностью исключить возникновение "мертвой зоны", т.е. понижение чувствительности способа при близких кратких замыканиях, когда величина U_s близка к нулю. В этом случае допускается отступление от правила (9), но взамен проверяется уровень параметров σ_s и σ_r. Имеется в виду, что при близком замыкании функция σ(x) монотонно повышает свой уровень от почти нулевого значения σ_r σ(0) до наибольшего σ_r= σ (l) (фиг.1).The angle between

and the predicted value

arg

-arg

When the line is not damaged, the predicted value coincides with the true (

=

) and

δ. But for the damaged line, transformations (32) will give a formal, albeit bearing useful information, result, and since

≠

,

≠ δ, then it is likely that

| will exceed 90 ^about , and the angle δHat itself does not lend itself to preliminary assessment. So, with a metal three-phase circuit, the current

behind voltage

almost 90 ^about and therefore the conversion

=

-jX

will give a result that is generally in antiphase with a value

. A similar phenomenon occurs with other types of closures. It is essential, however, that the relative position of the vectors

,

and

nevertheless, not arbitrarily, but obeys the laws arising from condition (7). First of all, this is regularity (9), which means that during a short circuit in the controlled zone, the vector of the reference current

located between stress vectors

,

, and leading can be as a vector

so and

However, for the selective determination of the damage zone, this condition alone is not enough. Additional signs of damage in the area are needed. They exist and are as follows. At low transition resistances, when the closure is close in nature to metallic, the vector

obviously ahead of the observed current

, and predicted stress

. Even with the reverse direction of the power of the pre-emergency load mode (δ <0), this position remains valid due to the limited modulus of the angle δ. Moreover, it is true for direct power transmission, when at large values of δ a rare case

> 180 ^about (option 3, figure 4). Nevertheless, option 1 is most typical when 0 <

<180 ^about . At negative true angle, the predicted angle

can be both positive and negative (option 2), but it certainly

> δ δ, since the inductive emergency current component biases the vector

in the lagging direction relative to the true vector

. To recognize option 1, it is enough to compare the signs of the three reactive parameters σ _s , σ _r and σ _u . Variants 2 and 3, associated with a large number of restrictions, are revealed only with the help of the additional active parameter ρ _u . The fifth, also reactive parameter Q increases the reliability of recognition of damage in the protected zone and "behind", i.e. to the left of the observation site. Damage in the zone corresponds to the negative direction of the reactive power of the values, the source of which is located at the site of damage. These values are listed in FIG. Having information about the sign of the parameter Q, we can completely eliminate the occurrence of a "dead zone", i.e. lowering the sensitivity of the method with close short circuits when the value of U _s is close to zero. In this case, a deviation from rule (9) is allowed, but the level of parameters σ _s and σ _{r is} checked instead. It is understood that with close closure, the function σ (x) monotonically increases its level from an almost zero value of σ _r σ (0) to the largest σ _r = σ (l) (Fig. 1).

,

,

,

. Формирующие блоки 13-14 реализуют операцию (32), т.е. предсказывают напряжения

в конце контролируемой зоны. Фильтр обратной последовательности 16 выделяет ток

. Таким образом, на выходах блоков 5-16 образуются все величины, необходимые для реализации критериев поиска повреждений (таблица 2). Не отражено лишь формирование аварийных слагающих

,

. Это отдельная задача, решаемая специальными фильтрами аварийных слагающих.In accordance with the theory, the proposed method is reduced to a sequence of operations implemented by the structural diagram of figure 2. Using filters of orthogonal components 5-12, the input quantities U _ν , i _ν , U _o , i _{o are} converted into complexes

,

,

,

. The forming blocks 13-14 implement the operation (32), i.e. predict stress

at the end of the controlled area. The negative sequence filter 16 emits current

. Thus, at the outputs of blocks 5-16, all the values necessary for the implementation of the damage search criteria are formed (table 2). Only the formation of emergency components is not reflected

,

. This is a separate problem solved by special filters of emergency components.

и

в зависимости от того, критерий какого вида замыкания вводится в действие. Возможны три алгоритма их функционирования. Первый состоит в поочередной проверке критериев различных видов замыканий. Второй в предварительном определении вида замыкания. И, наконец, третий промежуточный в предварительном выявлении частичных признаков того или иного вида замыканий. Именно этот третий путь и реализуется на фиг.2, где предусмотрено выявление особой фазы (блок 25) при земляных замыканиях (К⁽¹⁾ или К^(1,1)). Определяя фазу ζ, блок 25 дает сигнал коммутирующему блоку 17 принять в качестве величины

напряжение особой фазы

а в качестве опорного тока

ток нулевой последовательности

или обратной последовательности

или безнулевую аварийную слагающую тока

(таблица 2). Участия суммирующего блока 18 в этом случае не требуется. В результате, если, например ζ= А, на входы датчиков 19-22 поступят величины, указанные на фиг.3. Возможно, проверка гипотезы об однофазном замыкании даст отрицательный результат. Тогда проверяется гипотеза о двухфазном замыкании на землю фаз ζ-1 и ζ-2. И в этом втором случае коммутирующий блок 17 передает суммирующему блоку 18 напряжения

и

, а также токи

и

, который преобразует их в величины

и

согласно фиг.5.The switching and summing blocks 17 and 18 implements the operation of the formation of quantities

and

depending on what type of closure criterion is put into effect. Three algorithms for their functioning are possible. The first is to test the criteria for various types of faults one at a time. The second in the preliminary determination of the type of closure. And finally, the third intermediate in the preliminary identification of partial signs of a particular type of fault. It is this third way that is implemented in FIG. 2, where it is envisaged to identify a special phase (block 25) during earth faults (K ⁽¹⁾ or K ^(1,1) ). By determining the phase ζ, block 25 gives the signal to the switching block 17 to accept as a quantity

special phase voltage

and as a reference current

zero sequence current

or reverse sequence

or non-zero emergency current component

(table 2). The participation of the summing block 18 in this case is not required. As a result, if, for example, ζ = A, the values indicated in FIG. 3 are received at the inputs of the sensors 19-22. Perhaps testing the hypothesis of a single-phase circuit will give a negative result. Then the hypothesis of a two-phase earth fault of the phases ζ-1 and ζ-2 is tested. And in this second case, the switching unit 17 transmits the summing unit 18 voltage

and

as well as currents

and

which converts them to quantities

and

according to figure 5.

The previous operations were aimed at preparing the necessary values for determining the closure parameters σ _r , σ _s , σ _u , and possibly also ρ _u and Q (Fig. 4). Sensors 19-22 implement operations (1) - (5). The task of the logical block 24 is to analyze the signs of the compared parameters. Checking their compliance with FIG. 4, he determines whether there is a short circuit in the zone. True, the parameters themselves are fed to its inputs, but not only their signs, which allows us to additionally check the level of the difference σ _s −σ _r | to avoid false operation due to interference. Using the comparison unit 26 establish the fact of a significant excess of the parameter σ _r over σ _s , if they are of the same sign. The result of logical operations performed by block 24 is information on the type of circuit (indicating damaged phases) and on the damage zone.

 The use of additional parameters, primarily the mutual reactive power of two voltages, one generated from the measured voltages, and the second, formed from the voltages predicted at the end of the selection of the damaged phases and the damage zone. In this case, it becomes possible to determine the type of circuit by sorting out the criteria of each type.

Claims (17)

 1. METHOD FOR DETERMINING DAMAGED PHASES AND DAMAGE ZONES OF THE ELECTRIC TRANSMISSION LINE by measuring at the beginning of the line the voltages, currents, their components and converting the measured values into three reactive parameters, characterized in that the measured values are previously converted to first values corresponding to the voltages at the beginning of the line, the second values corresponding to the voltages at the end of the controlled area of the undamaged line, and to the third reference values, the first reactive parameter is formed as a mutual reactive power the first and third quantities, the second reactive parameter as the mutual reactive power of the second and third quantities, the third reactive parameter as the mutual reactive power of the first and second quantities, compare the sign of the third parameter with the signs of the first and second parameters and record damage in the controlled area, if the signs of the first and the third parameters are the same and opposite to the sign of the second parameter.  2. The method according to claim 1, characterized in that the fourth parameter is additionally determined as the mutual active power of the first and second quantities, the signs of all four parameters are compared, and damage is recorded in the controlled area if the first parameter is positive and the other three are negative.  3. The method according to PP. 1 and 2, characterized in that they additionally form fourth values proportional to the components of the measured voltages, fifth values proportional to the components of the measured currents, determine the fifth parameter as the mutual reactive power of the fourth and fifth values, and record damage in the controlled area only with a negative sign of the fifth parameter.  4. The method according to claim 3, characterized in that, if the signs of the first and second parameters coincide and the sign of the third parameter is opposite to them, the absolute values of the first and second parameters are compared and damage is recorded in the controlled area if the absolute value of the second parameter prevails.  5. The method according to PP. 1 to 4, characterized in that the first quantities use phase voltages at the beginning of the line, the second phase voltages at the end of the controlled area of the undamaged line, and the third currents of the alleged damage.  6. The method according to p. 5, characterized in that the zero sequence current is used as the third value.  7. The method according to claims 1 to 4, characterized in that the linear voltage at the beginning of the line and the second linear voltage at the end of the controlled area of the undamaged line are used as the first value.  8. The method according to PP.5 and 7, characterized in that the reverse sequence current offset by a predetermined angle is used as the third quantity.  9. The method according to claims 5 and 7, characterized in that the sum of the zero sequence current and the doubled current of the reverse sequence of the special phase are used as the third quantity.  10. The method according to PP.5 and 7, characterized in that as the third value use the emergency term of the current.  11. The method according to claim 7, characterized in that, as the third value, the difference in currents of the respective phases is used.  12. The method according to claim 3, characterized in that as the fourth and fifth quantities take voltage and zero-sequence current.  13. The method according to claim 3, characterized in that the voltage and current of the negative sequence are received as the fourth and fifth values.  14. The method according to claim 3, characterized in that as the fourth and fifth values take emergency components of voltages and currents.  15. The method according to claim 5, characterized in that the voltage of the zero sequence offset by an undefined angle is used as the third value.  16. The method according to PP.5 and 7, characterized in that the voltage of the reverse sequence of the special phase is used as the third value.  17. The method according to PP.5 and 7, characterized in that as the third value use the emergency component of the voltage, offset by a predetermined angle.