SU1742752A1 - Method of one-sided determination of a distance to the point of single-phase short circuit - Google Patents

Abstract

The invention relates to power line condition monitoring techniques. The device that implements the method contains 2 meters of active and reactive components of voltages (1, 2, 3), 2 formers of symmetric components (3, 4), 1 selector of the damaged phase (5), 2 current switches (6, 7) , 1 switch of phase voltages (8), 2 multiplication blocks (9, 11), 1 adder (10), arithmetic unit (12). 1-3-9-10, 1-4-7-12, 1 6-10-12, 4-5-7, 2-8-12. 1 il.

Description

The invention relates to power engineering and can be used to determine the distance to a short circuit (SC) on overhead lines (OHTL) of power transmission networks of super high voltage (330 kV and above), operating with a grounded neutral.

The known methods for one-sided determination of the distance to the fault location have insufficient accuracy caused by the effect of the transient resistance at the fault location. The error arises due to the difference in the currents flowing on the lines with two-way power in the place of measurement and in the place of short-circuit through the transient resistance.

The closest to the proposed method, according to which the active and reactive components of the phase voltage of the damaged phase are measured, form and measure the active and reactive components of the current zero

sequence, as well as the phase current of the damaged phase, compensated by the zero sequence current and the characteristic impedance of the monitored transmission line turned through the angle, and then the resistance of the short-circuit loop, which is proportional to the distance to the damage site, reduces the measurement error. is achieved by introducing into the calculation the current of the zero sequence, the phase of which at the place of measurement is close to the phases current flowing through the transition resistance at the site of RS. If these phases are equal, then the effect of transient resistance is removed.

However, in the ultrahigh voltage lines, the phase of the zero-sequence current at the measurement site begins to differ significantly from the current phase in months (L

WITH

those KZ. The reason for this difference is a slower decrease in the active resistivity of the zero-sequence overhead line compared to the forward (reverse) sequence with increasing wire cross-section. The similar nature of the change in resistance is explained by the presence in the active resistivity of a zero-sequence constant component, which takes into account the loss of active power in the ground and is independent of the cross-section of the wire.

The aim of the invention is to improve the accuracy of determining the distance to a single-phase short circuit. At the same time, the process of finding the place of damage and restoring the efficiency of power transmission lines is accelerated.

The essence of the invention is to measure the active and reactive components of the phase voltage of the damaged phase, to form and measure the active and reactive components of the zero-sequence current, as well as the phase current of the damaged phase, compensated for the zero-sequence current and turned on the angle of the characteristic resistance of the monitored transmission line, in the additional formation and measurement of the active and reactive components of the current negative sequence of the damaged phase and in the calculation of a special mathematical expression for the resistance of a short-circuit loop proportional to the distance to the damage site.

The drawing shows a block diagram of a device allowing to implement a method for determining the distance to a single-phase short circuit.

A device that implements a method for determining the distance to a single-phase short circuit location contains the first meter 1 active and reactive components of the phase currents, the second meter 2 active and reactive components of the phase voltages, the first driver 3 of the symmetrical zero sequence components, the second driver 4 of the symmetrical components negative sequence, selector 5 faulty phase, the first switch 6 phase currents, the second switch 7 negative sequence currents, the third switch 8 phase n straight zheny first multiplier 9, an adder 10, a second multiplier 11, an arithmetic unit 12.

The input blocks of the device are the first meter 1, whose inputs are connected to current transformers, and the second meter 2, whose inputs are connected to voltage transformers, and the outputs to the information inputs of the third switch 8, whose output is connected to

one input of the arithmetic unit 12 (output block), in addition, the outputs of the first meter 1 are connected to the inputs of the first generator 3, the output of which is connected to one input of the selector 5 not directly and through the first multiplication unit 9 to one input of the adder 10, to another input connected to the output of the first switch 6, the information inputs of which are connected to the outputs of the first meter 1, and to the inputs of the second driver 4, the outputs of which are connected to the information inputs of the second switch 7 and to other inputs of the selector 5, the outputs of which are connected to the inputs of the control of the first switch 6, the third switch 8 and the second switch 7, the output of which is connected to another input of the arithmetic unit 12, the third input of which is connected to the output of the second block

5 multiply 11, the input of which is connected to the output of the adder 10.

A device that implements a method for determining the distance to a single-phase short circuit works as follows.

0 The second meter 1 measures the orthogonal (active and reactive) components of the input voltages UA, UB, Uc - respectively UAX and UAY, UBX and UBY, Ucx and UCY, which from the outputs of the second measure 5 liters 2 sprinkled on the information inputs of the third switch 8 Similarly, the first meter 1 measures the orthogonal components of the input currents d, IB, ic, respectively AX and IAY, IBX and IBY, cx and lev.

0 which from the outputs of the first meter 1 are fed to the inputs of the first shaper 3, the first switch 6 and the second shaper 4. At the output of the first shaper 3, which represents the so5 filter of the symmetrical components of the zero sequence, the current of the zero sequence oh and IOY, which enters one of the inputs of voter 5 directly and through the first

0 multiplication unit 9, which multiplies the zero-sequence current by the compensation coefficient K (the compensation coefficient is, according to a well-known dependence, based on the characteristic con fi guration of the zero line and the direct sequence K .- (Zo-ZiA) / ZiA, to one of the inputs of the adder 10 At the output of the second driver 4, which is a three-phase filter of symmetrical components of the negative sequence,

reverse sequence currents I2AX And I2AY, I2BX And I2BY, I2CX And I2CY are generated, which are fed to the information inputs of the second switch 7 and other inputs of the voter 5. The voter 5 selects the damaged phase and affects the corresponding control output of the switches 6 , 7, 8. In this case, the voltage of the faulty phase, for example, UAX and UAY, goes to one input of the arithmetic unit 12, to the other input of which the negative sequence current of the damaged phase I2AX and I2AY comes from the output of the second switch torus 7. From the output of the first switch b, the damaged phase IAX and IAY current is fed to another input of the adder, where it is summed with the zero-sequence current multiplied by the compensation coefficient, and the phase current of the damaged phase, compensated by the zero-sequence current IAKX and IAKY, is obtained. From the output of the adder 10, this current is fed to the input of the second multiplier 11, which rotates the characteristic impedance of the monitored transmission line argZ, by an angle. At the output of the second multiplier 11, the phase current of the damaged phase is compensated by the zero-sequence current KI0 and turned by the characteristic resistance angle of the monitored transmission line IAKX and IAKY, which is fed to the third input of the arithmetic unit 12, the arithmetic unit performs elementary mathematical operations. The result of the calculations carried out in the arithmetic unit 12 is the determination of the resistance of the short-circuit loop, which is proportional to the distance to the fault.

Consider obtaining a mathematical expression implemented by an arithmetic unit. The voltage of the damaged phase (for definiteness of phase A) at the place of measurement is equal to

yA ZK (lA + K.lo) + jKRn, (1)

where UA is the phase voltage; ZK resistance of the power line from the measurement point to the short circuit; K is the compensation coefficient, and K (Zo, -Zi) Jp is the zero-sequence current at the measurement site; k is the current flowing through the short circuit; Rn - transient resistance in place short-circuit.

The current IK can be expressed through its symmetrical components. Wherein

JK 3J2AK 3K2J2A, (2)

rflej2AK-reverse sequence flowing in place of short circuit through the transition

Rn resistance; K2 is the current distribution coefficient (the ratio of the current at the fault location to the current at the measurement site) for the reverse sequence circuit at a fixed fault location.

Substituting (2) into (1) after dividing by I2A and separating the imaginary parts of the equality sides makes it possible to obtain

t 3Jb 12D

Lm

and

BA

 one

m

 + & lo - J2A

I

i2A

about;

Since the negative sequence currents in the place of damage and in the place of measurement are usually close in angle, then argK2 irO and expression (3) takes the form

(four)

Y A 7 LA + K10

L t f-

Mr. AI 2 A

one

Resistance to the fault location can be represented as a module and the angle ZK ZK argZ / l; rfle argZA is the angle of the characteristic resistance of the line. After substitution of this value in (4), the last one after transformation takes the form

 GUA1

I rTlA + KTTlargZ, tr - -

(five)

Currents and voltages can be expressed through their orthogonal (active and reactive) components.

UA UAX + JUAY;

OA + KI0) argZ / rjAKargZA JAK SAKX + - VARNISH;

J2A I2AX + JI2AY.

Substituting these components into the numerator and denominator of dependence (5) allows to obtain

bUAYI2AX L / Axl2AY.

, - -, (6)

t2- "t2

12АХ Д2АУ

L

t

The joint solution of equations (5), (6) and (7) allows to obtain the dependence implemented by the arithmetic unit 12:

7 - UAYl2AX- UAXJ2AY

Claims (1)

to IA to YI 2 A x - IA to x I 2 AY The invention The method of one-sided determination of the distance to a single-phase short circuit, which consists in measuring the active and reactive components of the phase voltage of the damaged phase, form and measure the active and the reactive components of the zero-sequence current form and measure the active and reactive components of the phase current of the damaged phase, compensated by the zero-sequence current and the characteristic impedance of the control power line, and the distance to the damage site is judged by the resistance of the short circuit loop, characterized in that, in order to improve accuracy, the active and reactive components of the reverse phase of the damaged phase are also formed and measured, and the loop resistance short circuit is determined by the expression z U AY I 2AX -C AX I 2AY I AKY I2AX-I AKX I 2AY where UAX and UAY are respectively active and reactive components of the phase voltage of the damaged phase; IAKX + JIAKY (U + K10) argZA - respectively, the active and reactive components of the phase current of the damaged phase, compensated for the zero sequence current .1 Kp and the characteristic resistance of the controlled transmission line argZA turned through the angle; I2AX and J2AY are respectively active and reactive components of the negative phase current sequence of the damaged phase. -SH