DE1907401A1 - Remote protection device for three-phase networks - Google Patents

Description

Dipl.-Ing. Egon Prince Dr. Gertrud Hauser Dipl.-Ing. Gottfried Leiser

Patent attorneys

Telegrams: Labyrinth Munich

Telephone: 83 15 10 Postal checking account: Munich 117078

8000 some 60,

Ernsbergerstrasse 19

Feb 13, 1969

Our reference: C 2620

COMPANGIE DES COMPTEURS 3, Rue Dosne, Paris 16e / France

Remote protection device for three-phase networks

The invention relates to remote protection devices for three-phase networks at the same time for short-circuits between phases and for earth faults.

There can be several types of faults or faults in such

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909840/0990

Networks

Differentiate networks: for example, three different short circuits between two phases without contact with earth, three Short circuits between two phases with simultaneous earth. Final, three earth faults, which only affect one phase,. and finally a short circuit, which the three phases. concerns (symmetrical conclusion).

There are protective devices known which, on the one hand, a selection system with a trip relay that responds to one of the faulty. ler characteristic electrical quantities, such as the impedance formed by the disturbed loop, and with from have the tripping relay controlled changeover relay and, on the other hand, a single Pern measurement system for all types of errors, which is fed by the selection system at the time the error or short-circuit occurs.

There are also protective devices known which consist of two different Types of relays exist, one type for earth faults and the other type for faults between phases is used.

These different devices have various disadvantages, in particular what the speed of operation and also with regard to occupational safety in the event of a fault between two phases with a simultaneous earth fault.

The invention aims to eliminate these disadvantages, since the device forming the subject of the invention only with the help is realized by static organs. It allows directional remote protection to be achieved without a switching device for all types of short circuits that can occur in a three-phase network: a short-circuit that affects the three phases

909840/0990 (symmetrical

(symmetrical circuit), a circuit between two phases without an earth fault or with a simultaneous earth fault and a Short-circuit between a phase and earth (asymmetrical short-circuit). In addition, the device according to the invention allows in In the case of the latter unsymmetrical conclusion (contact between a phase and earth), the selection of the disturbed phase.

The invention is based on the comparison of the phase shift of two voltages with respect to a third, which is taken as a reference value, and on the comparison of the order of their phases, these three voltages V, V ¹ ^, V being defined by the following relationships;

^V 'a ^{= V} a - ^{Z (I} a ^{+ KI} r ^}

^v 'b ^{= v} b - ^{Z (I} b ^{+ K} V

^V 'c ^{= V} c * ^{Z (I} c ^{+ ΚΙ} γ>

where V, V., V are the simple voltages (voltages between

el D C

see phase and neutral) of a three-phase line are at the point of the protection device and whose three phases are designated A, B, C. I, I., I _n , I are the respectively in the

el D C 2 /

three phases A, B, C and currents flowing in the neutral conductor N when an asymmetrical circuit occurs, Z is a reference impedance, which is the impedance of the line section to be protected represents, and K is the coefficient of earth impedance defined by the well-known relationship:

^ £, a * λ J

y \ mm '' ■ "" - 'YY _%

909610/0990

_ If _

where Z is the positive sequence impedance of the line section to be protected and Z is the homopolar impedance of that section.

The following are the three voltages V ', V'. V "simply

a D c-

before compensated stresses called ".

More precisely, uses the protective device according to the invention comparing the phase shift of these three "simple compensated voltages" and comparing the phase shift one of these compensated voltages with the composite voltage between the other two phases. (e.g. the phase shift of V with respect to the

composite voltage V. - V) with the help of known logic circuits which are combined in such a way that a signal is obtained which indicates the opening of the three-pole Breaker in the case of a three-phase or two-phase short with or without a simultaneous earth fault controls inside the protected section, and that one also receives a signal indicating the defective phase in In the event of a fault between a phase and earth that also occurs inside the protected section and example trip the opening of two corresponding monopolar Interrupt controls.

The protective device according to the invention has a circuit for achieving the three "simple compensated voltages" V ' _a , V' bS V ' _{c with four amplifiers, which behave in a manner known per se} as analog-to-digital converters and their input voltages are each converted into square-wave signals convert whose amplitude only takes two values O and + V, where V is equal to

909840/099 0 voltage

BAD OFHGfNAL

voltage is equal to the logic normal assumed for the logic circuits, the phases of these signals those of the input voltages are related and where three of these amplifiers are each different from the "simple ones" mentioned above compensated voltages "are fed, while the fourth is fed by an inter-phase voltage. The Protection device according to the invention is characterized in that on the one hand the outputs of the three first amplifiers are connected to a first phase comparator and to a second phase comparator and the output of one of these Amplifier and the output of the fourth amplifier are connected to (a third phase comparator, these three phase comparators are formed by combinations of logic circuits, and that on the other hand the outputs these three phase comparators are connected with logical and, neither-nor- and or circuits in such a way that they are independent of the type of circuit a control signal for the three-pole breaker and also a signal which detects the faulty phase in the event of a connection between a phase and earth and, for example, the opening of the controls corresponding single pole breaker.

The invention is explained in more detail, for example, with the aid of the figures. It shows

FIG. 1 shows a circuit diagram of an arrangement for achieving the three "simple compensated voltages" V, V ', V ₉

Figure 2 _3, which includes Figures' 2a to 21, several diagrams in which the position of the vectors of these "simple compensated voltages" is shown in normal operation and with all types of errors,

909840/0990 _{Flp; ur 3}

JHWi -: t

Figure 3 as a puncture of the time t the values of the three "simple compensated voltages "V, V ', V,

Figure 4 is a circuit diagram of an embodiment of the invention Guard and

Figure 5, which includes Figures 5a to 5g, several diagrams, in which the relative phase shift of a "simple compensated voltage" with respect to a composite voltage applied as a reference value in the cases ^ a conclusion of a phase with respect to earth, two phases with respect to Earth and a short circuit between the three phases inside the line section to be monitored is.

In Figure 1, the three phases of a network with A, B, C are designated and its neutral conductor N is connected to earth. The primary windings of three current transformers 21, 22, 23 are each connected to the phase conductors A, B, C through which the currents I, I., I defined above flow

el D C

will.

, One end of its secondary winding is respectively connected to one end of the primary winding • a Bezugsgegeninduktivität 24, 25, 26th These mutual inductances have the same value Z, which represents the impedance of the line section to be protected between the point D of the protective device and the end M of this section. This impedance Z has the same argument as the positive sequence component of the impedance of this section. The secondary windings of the transformers 21, 22, 23 are combined at their other ends. The same

is applicable

909840/0990

applies to the other ends of the primary windings of the mutual inductances 2k _s 25, 26. These two common points are connected via conductors 20, 20 'to the primary winding of a reference mutual inductance 27 with the value Κ · Ζ, where K is the coefficient of the earth fault impedance defined above . Current I flows through this winding when an asymmetrical earth fault occurs.

The primary windings of three voltage transformers 31 » 32, 33 are each of one of the voltages V ₉ V,, V

el D C

fed between a phase and earth. One end of the primary windings of these transformers is each connected to the common point P, which in turn is connected to one end of the secondary winding of the mutual inductance 27. Each of the secondary windings of the voltage transformers 31 j 32 _s 33 is also connected to the secondary winding of one of the mutual inductances 2k , 25, 26 in such a way that three circles are formed, each of which is connected to one of the input terminals of amplifiers 9 ₉ 10, 11. The other end of the secondary winding of the mutual inductance 27 is connected to the other input terminal of this amplifier.

It is obvious that the three voltages V, V., V ¹

actually correspond to the specified relationships (1), (2), (3).

The amplifiers 9 _: 10, 11 are connected in a known manner in such a way that they behave like analog-digital converters, their respective input voltages V, V ', V in

* el D C

Convert square wave signals with two values (0 and + V), whereby the

909840/0990 phases

BATH ORIGINAL

Phases of these signals are related to those of the input voltages.

If a short occurs between a phase (e.g. phase A) and earth, s:
express the following relationship:

Phase A) and earth occurs, the voltage V _Q lets through

el

^V a

If in relation (l) V one is given by his through the

Replacing the value expressed in drawing (4), one obtains after simplification:

^V 'a = ^(Z d - ^Z > ^(I a ^{+ K} V

V · and V ¹ are expressed by analogous relationships.

D C

It can then be seen that in the event of a ground fault on one or two phases at the end M of the protected line section DM, the "simple compensated voltages" of the disturbed phase or the disturbed two phases are zero, since Z = Z. If the same type of fault outside of the line section to be protected, either above or below it, arises, the "simple compensated voltages" remain practically in phase with the corresponding simple voltages. If, on the other hand, this type of fault arises inside the protected line section, Z ^ is smaller than Z, so that the polarity of the "simple compensated voltage" of the disturbed phase or the two disturbed phases is related

909840/0990 -

BAO ORIGINAL

the corresponding simple voltage is constantly reversed. In other words, the same wise regarding the corresponding simple voltages are constantly in opposite phase.

In the case of a short between two phases without an earth fault, for example between phases B and C, the composite compensated voltage V '- V zero if the-

D C

This error occurs at the end M of the protected line section, it is in phase with the composite voltage V, - V for a conclusion outside of this section and g indicates opposite phase to V. - V for a conclusion inside

Q C

within this section.

The diagrams of the voltages V, V ', V in FIG.

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tern the above statements.

Diagram 2a shows the vectors of the three voltages V ',

V ', V during normal operation. The three vectors are mutually

D O

offset by 120 °. I is therefore zero. From the relationships (I) ₃ (2), (3) it follows that the voltages V '", V', V ·

et D C

each equal to V, V,, V minus the voltage drops ZI-

3, DC el

ZI ,, ZI are. These have the same phase angle and essentially the same value.

Diagram 2b shows the vectors of the three voltages V V, V ^f in the case of a three-phase circuit. Each of these vectors has opposite phase to the corresponding vector shown in diagram 2a.

909840 / 099Ü -

- ίο -

The diagrams 2c, 2d, 2e each show the vectors of these voltages in the Pall of a termination of one of the phases A ₃ B or C with respect to earth in the interior of the line section to be protected.

The diagrams 2f, 2g, 2h each show the vectors of the above-mentioned voltages and the vectors of the composite compensated voltage V '-V ₃ V - V, V - V in the event of a short between two phases without a ground fault inside the line section to be protected .

D cc a a c

The diagrams 2j, 2k, 21 each show the vectors of Voltages V, V 'V in the event of an earth fault of

two phases inside the line section to be protected.

FIG. 3 shows the values of the three "simple ones" as a function of time t compensated voltages "V, V ', V. ^. and f,

represent dfe phase shifts of the voltages V ^f _b

and V 'with respect to V. From this example it can be seen c a

lent that V and V 'offset backwards ^{with respect to V 1 3} cb ° a

are and that under these conditions ^. and f are negative.

From Figure 2 it can be seen that this condition in the case of a connection between phase C and the neutral conductor (Figure 2c) or in the event of a ground fault between phases A and B (FIG. 21).

In general, one can see from examining the one shown in FIG Diagrams derive from the following table.

-? 909840/0990 -

- ii -

-Pb -Pc Normal operation or any
Disturbance outside the ge
protected section _ + Three-phase circuit - + No more between a phase
and earth inside the ge
protected section
at
b N
c N +
+ + An end between two phases
and earth inside the ge
protected section
bc N
ac N
from N +
+ + An end between two phases
inside the protected
Section
bc
ac
away +
"+ -

The examination of this table shows, on the one hand, that a summary

909840/0990

meet

meeting a negative «f>, and a positive ψ either

which corresponds to the original operation or a disturbance outside the protected section or a three-phase circuit (symmetrical circuit). Any other combination of positive and negative values of ψ _} and - ^ forms one

Indication of the presence of an asymmetrical termination inside the protected section (termination between a Phase and earth or short-circuit between two phases without contact with earth or with simultaneous earth fault).

It can therefore be seen that the knowledge of the sign of -f and γοη -P is not sufficient to decide between an over-phase circuit in the protected section and a fault outside this section or normal operation. to

For this purpose, the invention provides the use of a single-phase distance relay, which is connected to any flow loop. In addition, the use of a phase comparator _{3 is} provided which determines the sign of the phase shift "P of a ^ simple compensated voltage" (for example V) with respect to the composite

Voltage, in this example V, - V. As explained further below, in particular with reference to the diagrams in FIG. 5, the sign of the phase shift is positive, especially in the case of a three-phase circuit, so that a negative -ß coincides. and a positive -f _c r; o as well as a positive ψ is a sufficient characteristic for a three-phase connection.

When you get between any phase and the Owl Leader to distinguish the relevant asymmetrical disturbances

909840/0990 wishes

BAD ORfGiNAL

wishes, it is necessary, on the one hand, to remove the earth faults from the faults between two phases without an earth fault and on the other hand, to distinguish the connections between two phases and earth from the connections between a phase and earth.

This result is obtained on the one hand with the help of a comparator, which emits a signal during the time interval in which the three "simple compensated voltages" are either positive or negative at the same time, and on the other hand with the help of the above-mentioned comparator, which the sign of the phase shift ψ a "simple compensated voltage" (for example V ') with respect to

borrowed the composite voltage V, - V indicates.

As already mentioned, the "simple compensated voltages" V, V ', V as well as a composite voltage

et D C

tion (for example V, - V _n ) in per se known analog

D C

Digital amplifiers are converted into logic signals and these logic signals are passed into comparators consisting of logic circuits in which the determination of the sign of the phase shifts -f. , -f and "P as well as the

Comparison of the polarities of these signals is carried out. The outputs of these comparators are so with logical And-, neither-nor- and or-circuits connected that one is independent on the nature of the disturbance inside the protected section an output signal is obtained and that in the case a short between any phase and earth receives a selection signal for the defective phase.

In Figure 4, which shows the circuit diagram of an embodiment of the

909840/0990 according to the invention

According to the protective device according to the invention, one sees the analog-digital amplifiers 9, 10, 11, which were already mentioned in the description of FIG. 1 and are each fed _{by the "simple compensated voltages" V 'a} , V ^f _b , V' _c will. An amplifier 12 identical to the previous one is fed with the intermediate phase _{voltage V ß __ c.} The outputs of the amplifiers 9, 10, 11 are connected to the input circuits of phase comparators (or polarity comparators) 6 and 7. The outputs of the amplifiers 9 and 12 are connected to the input circuits of the phase comparator 8. "· ■■." .- ■, -

In the phase comparator (or polarity comparator) J. , The phase shifts ψ. and ψ the logical ones corresponding to the "simple compensated voltages" V 'and V * _

Signals compared with the logical signal which the. "simple compensated voltage" V, which is defined as zero

point for the phase shifts is taken as above executed. ;

This phase comparator (or polarity comparator), which is known per se, has four outputs which _{supply four logic signals £ ', "STg, £ ,, - H 1} , which meet the following conditions:

1) Σ ₁ = 1 and I ₂ = T, = £ ₄ = 0 if * f, is negative and λ is negative;

2) X ₂ = 1 and X ₁ = E ₃ - E ₄ = 0: __ if * f _{b is} positive and ^ negative;

3) I ₃ = 1 and ^ ₁ ~ I ₂ = Σ ₄ = 5 Oy

90984Q70990

\ if

-15 -. '■'. '' ■ ... ■■ '■■. ■■''■ ... ^: .'- ■ "■ -

if ψ . negative and ^ f is positive;

ι and E ^ = ^ ₂ ■ ;; = £ ₃ = o ,:

if f>, is positive and ψ . ■ is positive.

The output terminals of the phase comparison -7-> to which the signals 5_ «. ₃ S ₂ ^un d Σ'κ are each connected to one of the input terminals of logic AND circuits 5, 3 and 4, while the output terminal from which the signal £ is picked up is connected to one of the input terminals.

A logical AND circuit: 2 and with the input terminal a logical neither-nor circuit 2V is connected ..

The outputs of the logic circuits ^ 2 and 2 'are with the logical OR circuit 1 connected. The outcome of this - the latter logic circuit is with a die'Beticherung a three-pole breaker controlling organ connected.

This circuit breaker must operate in the event of short circuits occurring inside the protected cut between two phases, between two phases and earth or between the three phases. . ._ '■■ - -: "..'

The outputs of the logic circuits 3 ₃ ^ and 5 supply a selection signal for the disturbed phase in the case of a fine connection between any phase and earth. _. ^:: -

Each polarity comparator consists essentially of two Lofrian ochaltunp: en, "an And-Schaltunp ·, and a Weder- ■ iloch-öchaltun: - ;;, with three inputs, each of which is divided by the -.: üen" corrected voltages "-V ₃ V ¹ ", V '; un- -

9098A0Y0990

' speaking

BAÖ

- i6 -: ■; ■■

speaking logical signals are fed. The AND circuit outputs a logic signal V = 1 during the time interval in which the three logic signals are positive at the same time. The neither-nor circuit is a logical one Signal V = .1 during the time interval in which the three logic signals are negative at the same time. The outputs of the two logical AND or neither-nor circuits are connected to the two inputs of a third logical OR circuit, which outputs a signal 6 = 1, if one or the other of their input is a logical one Receives signal V = 1. "., ■.-..--" ■

The polarity comparator 6 can also be formed by a single logical AND or neither-nor circuit, what leads to the suppression of the logical OR circuit, but it is much more advantageous,, the three logic circuits, *, namely the and-, the neither-nor- and the or-connection to because you have a much faster response speed., receives. ■. "'Y

How an examination of the diagrams 2c, 2d, 2e, 2;}, 2k, 21. shows, which relates to the position of the vectors of the "simple compensated voltages"V; ^{1st v} 'h * ^v ' _c ^{in the} case of earth faults between a phase or between two phases inside the protected section, the "simple compensated voltage" of each faulty phase is offset by 180 ° with respect to its position during normal operation. Under these circumstances, / is the maximum phase shift between the pairs taken voltages V, V, V is less than l80 ° ,, _so;

that the three vectors V ', V., V ¹ in the same half-plane

CL U C - - -

lie. There is therefore necessarily one. Time interval,

9098 4 0/09 90 meanwhile

meanwhile these three tensions are simultaneously the same have positive or negative polarity *

The logic signal G = 1, which is supplied by the polarity comparator 6 in the event of earth faults between a phase or between two phases inside the protected section, is transmitted to one of the input terminals of the logic AND circuits 5, 3, 4.

In the phase comparator 8, the sign of the phase comparison is

sweet

Shift τ of the "simple compensated voltage" V'-

lent the composite voltage V. - V determined «He supplies a logical signal P = 1 if the voltage V 'is

CL

with respect to the composite voltage V, - V is delayed

(i.e. when f is positive) and a logic signal P = O or P = 1 in the opposite case.

The diagrams 5a, 5b _} 5c of Figure 5 show in solid lines the vectors of the voltages V 'and V. - V _n for the

3. UC

Case of an earth fault of one of the phases A, B or G. The diagrams 5d, 5e, 5f of the same figure show in solid lines the vectors V and V _b ■ - Y _Q for the case of an earth fault of two phases, and the diagram 5g shows the situation these same vectors in the case of a three-phase connection.

The state of the signal P in the various, in the diagrams the failure cases shown in FIG. 5 is indicated below: '",". '

Conclusions ....., a N * f> 0, P = I

b c N

-18 ..-., .- ■■

b e N ~ P < O, P. = o, P = 1 b N ■ *> ■ o _s P. = 0, P = 1 C. a N o _s P. ■ * ■ Ί C. N O, P. = o., f = 1 a b N- O, P. = 1

Three-phase circuit ^; ο, P = I _.:

The polarity comparator 8 has two outputs, one of which one of them supplies the signal P and one of the three inputs the logic circuit 3 and with one of the two inputs the logic circuit 2 is connected, and -of which the others deliver the signal - "P and with one of the three inputs of logic circuits 4 and 5 is connected.

The phase comparators 7 and 8 are not discussed in detail wrote as it is the subject of the French patent specification 1 447 510 are. '

A three-phase circuit inside the protected section is established on the one hand by outputting a signal C- * = 1 and signals ^ ₁ = Σ = Σ ^ = 0 at the output terminals of the phase comparator 7 and on the other hand by outputting a signal P = 1 at the output terminals of the Phase comparator 8 determined. These two signals are received in the logical AND-Sehaltung 2 and on the logical OR circuit. 1 transferred. In other words, a three-phase connection corresponds to the logical equation P * Σ-, = 1.

The asymmetrical disturbances inside the protected section are caused by the emission of signals ^ ₁ + Ip. + X ₁ . = as well as J, -, = 0 determined at the output terminals of the phase comparator. .

90984 0/0990

- ■ '■ ""' '* "That

The signal 2l is also applied to the logical Weder-Noeh circuit. 2 ^l transferred. The output signal Σ. - * This logic circuit, whose state "1" corresponds to all asymmetrical internal disturbances, is transferred to the OR circuit 1 .; ■ "-"; ■ -.

In other words, any internal unsymmetrical inference or error corresponds to the logical equation Σ.-, ~ 1.

The logical equation which defines the Peststellung any kind of interference or circuits inside the protected portion of _s can be expressed as follows: Σ + Σ-, .p.

An internal short between phase A and earth is determined by the output signal of the AND circuit 3, which _{receives 3 signals P 3} E ₂ and G, this output signal having the logical equation G · P · Σ. ₂ ⁼ 1 must satisfy, which characterizes this disturbance well with the exclusion of all other asymmetrical disturbances.

In fact, as stated above, G-1 is for each earth fault of one phase or two phases, whereby the faults between two phases are switched off without an earth fault. P = I applies in the event of a connection between phase A and earth and in the case of a connection between phases A, B and earth and between phases A, C and earth. £ ₂ = l _s if "-f.- is positive and tf _c · negative, which is particularly evident in the case of a conclusion between phase A and earth.,

An internal conclusion between phase B and earth is made by the

0/09 90. 'Output signal

Output signal of the logic and management 4 determined, which receives three signals Ih, F and G, this being Output signal the logic equation G · F · Σ. ^ = 1 meet must, which identifies this error with the exclusion of all other asymmetrical errors.

In fact, G = I for every earth fault of one or two phases. F = I applies in the event of a connection between phase B and earth and in the case of a connection between phase C and earth and between phases B, C and earth. 5L ₁ , = I ₃ if ^, and «f are positive, uras themselves

in the event of a termination between phase B and earth.

A short between phase C and earth is determined by the output signal of the logical AND circuit 5, which _{receives three signals JE 1} , F and G, this output signal having to satisfy the logical equation G · F · S. = 1,

which identifies this error with the exclusion of all other asymmetrical errors, where E _{1 is} equal to 1 if ψ. and \ P are negative, which is particularly the case in the case of an inference

■ C ...

applies between phase C and earth.

If one does not wish to carry out the detection of the disturbed phase in the event of a short-circuit between a phase and earth, the phase comparator 6 and the logic circuits 3, ² I and 5 are of course omitted.

909840/09 9 0 claim

Claims (1)

Claim Remote protection device for three-phase networks, which on the one hand compensated a circuit to achieve three simple ones Voltages of the form V - Z (I + KI), where V is a simple voltage, I the current flowing in the phase, I the current flowing in the neutral conductor when an asymmetrical circuit occurs, Z a reference impedance and K the Is the coefficient of the earth impedance, and on the other hand has four amplifiers working as analog-to-digital converters, three of which are each fed by one of the three simple compensated voltages, while the fourth is fed by an intermediate phase voltage, characterized in that on the one hand the outputs of the first three Amplifier with a first phase comparator (or polarity comparator) and with a second phase comparator (or polarity comparator) are connected and that the output of one of these amplifiers and the output of the fourth Amplifier which differs from the intermediate phase voltage opposite to the supply voltage of the previous amplifier is fed, connected to a third phase comparator (or polarity comparator), these three comparators are formed by known combinations of logic circuits, and that on the other hand the outputs these three comparators are connected with logical and, neither-nor- and or circuits in such a way that independent of the type of short-circuit, a control signal for a three-pole breaker and in the case of a short-circuit between a phase 909840/0990 _and and 'earth is obtained a signal _s which detects the faulty phase, and can control the opening of a corresponding single-pole breaker. 909840/0996 * 3: Empty page