RU2468378C2 - Method of measurement of distance to fault location - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: orthogonal components of minimal line-to-line voltages in various points of branched high-voltage line are measured simultaneously under line-to-line fault, at the same time minimal line-to-line vector values are measured. Using known values of complex resistance between these points maximum vector values of phase current difference on these sections are determined. Using these values maximum difference of phase current of faulted section close to fault point is determined. Distance to fault point from the closest voltage measurement point where obtained current passes is determined. During such calculation unfaulted phases load currents are considered and accuracy of distance calculation increases. Currents measurement is not required and there is no necessity to use current transformers operating in nonlinear modes under high fault currents.

EFFECT: increasing accuracy of measurement of distance to fault location in branched high-voltage lines.

4 dwg

Description

The invention relates to the field of electrical engineering and can be used when measuring the distance to the place of a short circuit in high voltage lines.

In the known method, implemented in the device [Locking resistance indicator FIS / A.I. Eisenfeld, V.N. Aronson, V.G. Glovatsky. M .: Energoatomizdat, 1987. - 64 pp., Ill. - (Electrical Engineer; Issue 595)], the input voltage and current of the short circuit are measured and the distance to the short circuit is determined by dividing the reactive component of the voltage by current. To reduce the error from the presence of load currents, the pre-emergency load current is subtracted from the emergency current. The source of the error in this case is the inequality of the currents of the undamaged feedings of the feeder in emergency and pre-emergency modes.

The disadvantage of this method is the presence of an error due to load currents. The source of the error is also the need to measure a current that varies over a fairly wide range (0-1000 A), which is technically related to the presence of sufficient non-linearity in the conversion of the current transformer at large current values.

The objective of the invention is to improve the accuracy of measurements.

This goal is achieved in that by measuring the distance to the short circuit in high-voltage electrical networks, including measuring the minimum value of the emergency voltage vector and determining the ratio of the reactive component of voltage to current, according to the invention simultaneously measure the minimum interfacial vector values of line voltage at various points and with using the known values of the complex resistances between these points determine the maximum vector values differently the phase currents in these sections, using which they find the maximum phase current difference of the damaged section located in the immediate vicinity of the short circuit point; determine the distance to the short circuit point from the voltage measuring point closest to it where the received current flows.

An embodiment of the device that implements the proposed method is depicted in FIG. 1a, where the basis is a known device (Short circuit directional lock. Patent No. 2238752, Russian Federation, IPC H02G 7/16; G01R 31/00, No. 2005128914; claimed 15.09. 2005; published July 10, 2008. Bull. No. 19. Gadzhibabaev GR, Gaydarov PM) transmission of information about the phase-to-phase fault section.

FINKZ consists of receiving (PrU1) installed at the substation and transmitting (PU2, PU3, PU4) devices installed on the supports of the L5 high-voltage line. PU and PrU are connected to the phases of the line through high-voltage resistors (BBC) 4-6 mOhm. In the operating mode of the line, the control panel receives power through them. In case of a short circuit at point K1, the magnetic field of the short circuit current covers PU3 and, when it is activated, after disconnecting the line due to the accumulated energy, it sends DC voltage pulses to the line for a predetermined time interval counted from the moment of short circuit, and by this sign PrU1 distinguishes triggered PU .

Unlike FINKZ, in the proposed device, all PUs of the disconnected feeder are triggered by the fact that the interfacial voltage drops below the setpoint and, according to FIG. 1a, the magnetic field of the short-circuit current covers only PU3 and its output voltage U ₂ according to FIG. 2 has a positive sign, and the voltage U ₁ , U _{3 of the} remaining transmitting devices have a negative sign.

In transmitting devices, when the interfacial voltage drops below the setpoint, the minimum values of the interfacial voltages are measured and stored in the form of orthogonal values measured after a quarter of the industrial current period (vector values).

With a short circuit of phases A and B at point K1 and with unsuccessful automatic reconnection of the line (AR) at time t ₁ , the channel of the receiving device with a logical voltage of 1 U ₄ opens and at intervals t ₃ -t ₂ and t ₄ -t ₃ PU2 sends In a line, the DC voltage signals U ₁ and the duration of the indicated time intervals are linearly dependent on the values of the orthogonal components. Similarly, signals U ₂ and U ₃ are transmitted to the line at the opening intervals of the corresponding channels of the receiving device with voltages U ₅ and U ₆ .

The measurement of the corresponding orthogonal voltage components at the substation is made by the receiving device.

The schematic diagram of the line section according to figa is shown in fig.1b, where the maximum values of the phase current differences are determined by the measured minimum values of the voltage vectors U _AB1 , U _AB2 , U _AB3 and the values of the complex resistances of the line sections Z ₁ , Z ₂ , Z ₃ expressions

I _AB1 = I _A1 - I _B1 = ( U _AB1 - U _AB2 ) / Z ₁

I _AB3 = I _A3 - I _B3 = ( U _AB2 - U _AB3 ) / Z ₃

I _AB2 = I _A2 - I _B2 = ( I _A1 - I _B1 ) - ( I _A3 - I _B3 ).

Further, according to the known values of current I _AB2 , voltage U _AB2 , specific reactance x _beats of the line section with resistance Z ₂ , the distance L from the point of voltage measurement U _AB2 to the place of short circuit is determined according to the well-known formula

L = U _AB2 * sinφ ₂ / (I _AB2 * x _beats ) = z ₂ * sinφ ₂ / x _beats (km),

- действующее значение комплексного напряжения U _AB2=А_AB2+jB_AB2 с действительной и мнимой частями A_AB2 и В_AB2 (они являются ортогональными составляющими, измеренными передающим устройством ПУ2);Where

- the effective value of the complex voltage U _AB2 = A _AB2 + jB _AB2 with the real and imaginary parts A _AB2 and B _AB2 (they are orthogonal components measured by the transmitting device PU2);

- действующее значение комплексного тока I _AB2=I _A2-I _B2=(C_A2 +jD_A2)-(C_B2 +jD_B2)=(C_A2-C_B2)+(D_A2-jD_B2)=C_AB2 +jD_AB2 с действительной и мнимой частями C_AB2 и D_AB2; φ₂ - аргумент комплексного сопротивления Z₂+R_п, определяемый как разность начальных фаз напряжения ψ_u и тока ψ_i, т.е. φ₂=ψ_u-ψ_i, где

- the effective value of the complex current I _AB2 = I _A2 - I _B2 = (C _A2 + jD _A2 ) - (C _B2 + jD _B2 ) = (C _A2 -C _B2 ) + (D _A2 -jD _B2 ) = C _AB2 + jD _AB2 with real and imaginary parts C _AB2 and D _AB2 ; φ ₂ is the argument of the complex resistance Z ₂ + R _p , defined as the difference between the initial phases of the voltage ψ _u and current ψ _i , i.e. φ ₂ = ψ _u -ψ _i , where

ψ _u = arctg B _AB2 / А _AB2 , ψ _i = arctg D _AB2 / С _AB2

As in the prototype, the active resistance R _p at the point of short circuit does not introduce errors when measuring distance.

The above calculations show that in the absence of branches between the points of measurement of interphase voltages, the error in determining the distance to the short circuit point is absent in the presence of load currents of intact solders, while in the prototype they cause quite large errors.

The source of error reduction is also the lack of the need to measure current.

A variant of the transmitting device that implements the proposed method is shown in Fig.3.

It consists of high-voltage resistances VVS6-VVS8, rectifier V9, source of information signal IIS10, storage capacity C11, keys K12-K21, logic elements HE22-HE24, analogue adders SUM25-SUM28, AC to DC converters PR29-PR33, comparators KP34- KP36, logic gates OR37, OR38, logic gates I39, I40, waiting multivibrators ЖМ41-ЖМ43, differentiating devices ДУ44, ДУ45, memory devices ЗУ46, ЗУ47, voltage converter to pulse duration PNDI48.

The principle of operation of the transmitting device is as follows.

Three phases L5 with phase voltages U _A , U _B , U _{C are} connected to VVS6, VVS7, VVS8, forming voltage dividers with SUM25, SUM26, SUM27, at the outputs of which high-voltage line voltage signals are allocated (key K12 is open). These sinusoidal signals are converted at the outputs of PR29, PR30, PR31 into constant voltages proportional to the line voltages U _AB , U _BC , U _CA. According to the scheme, KP34 and KP35 compare signals U _AB , U _BC and U _BC , U _CA, respectively. The presence at the outputs of comparators KP34, and KP35 logical 1 signal indicates compliance ratios U _AB> U _BC and U _BC> U _CA and therefore the lowest phase voltage is U _CA. Similarly, subject to the ratios U _AB <U _BC and U _BC <U _CA, we get logic 0 at the outputs of the comparators and the voltage U _AB is the least. If there is a logical 1 at the output of KP34 and a logical 0 at the output of KP35, the voltage U _BC is the least. With these ratios, logical 1s respectively appear at the outputs of I39, HE24 (via OR37) and I40 (through HE23). The output signals of these elements are fed to the control inputs of the keys K14, K15 and K16, the information inputs of which receive linear voltage signals U _AB , U _BC , U _CA from the outputs SUM27, SUM25, SUM26, respectively. The outputs of these keys are connected to the inputs of SUM28 and, as described above, the minimum phase-to-phase voltage in the form of a sinusoidal signal during a short circuit in the line is allocated at its output. Further, this sinusoidal voltage is converted to constant at the output of PR32, supplied to the input of KP36. Upon the fact that the interfacial voltage drops below the setpoint (u _mouth ) of KP36, the logic signal 1 appears at the output of the latter, opening K17, and the output voltage SUM28 is repeated at its output. The PR33 element converts the alternating output voltage K17 into a constant one and a short-term pulse appears at the output of the DU44 at the front edge of its appearance, opening K18 and, therefore, an almost instantaneous value (the first orthogonal component) of the emergency voltage is recorded in the Z46. At the same time, the ZhM41 element is triggered by the output pulse DU44, which forms a short-term pulse at the output of DU45 after a quarter of the industrial current period and through K19 in ZU47 the second orthogonal component is recorded. The output pulse ДУ44 also starts ЖМ42 and ЖМ43, which at fixed intervals (for ПУ2 t ₂ and t ₄ in Fig. 2) from the moment of short circuit open К21 and К20, respectively, and the recorded orthogonal components go to the input OR38 and then to the PNDI48 input. In PU2, the t ₃ -t ₂ intervals are proportional to the first, and t ₄ -t _{3 the} second orthogonal component due to the modulation of the time interval in the PNI48 element. Similar conversions occur in PU3 and PU4. The output signal of logical 1 PNDI48 closes K12 and opens K13. In the normal mode of operation of the line, when the positions of these keys are reversed, capacitors IIS10 (to a voltage of 200-400 V transmitted to the line) and C11 (power to the circuit in the signal transmission mode) are charged through B9. When K13 is open, at the above intervals, DC voltage is transmitted to the line through the VVS8, received by PrU1 at the substation (this method of signal transmission has been tested in the aforementioned FINKZ device).

In Fig.3, a separate block for selecting the minimum interfacial voltage (BVMMN49) is separately highlighted.

A variant of the receiving device that implements the proposed method is shown in Fig.4.

It consists of VVS50-VVS52, BVMMN53, PR54, NE55, ZhM56-ZhM60, low-pass filter LPF61, DU62, DU63, K64-K71, ZU72, ZU73, I74-I76, converters of duration to voltage PDN77-PDN79, triggers Tg80-Tg82 , executive elements IE83-IE90.

The principle of operation of the receiving device is as follows.

Elements VVS50-VVS52 are connected to L5 and their second leads are connected to the input terminals of BVMMN53 (it has an identical circuit with BVMMN49 in figure 3) in the same way as in the transmitting device. The BVMMN50 output (K17 output in Fig. 3) is connected to the elements PR54, ЖМ56, ДУ62, ДУ63, К64, К65, ЗУ72, ЗУ73, operating similar to the elements of Fig. 3, and as a result, the orthogonal voltage components L5 are recorded at the substation displayed by IE83 and IE 84.

From the other output of the BVMMN53 (see the output of KP35 in Fig. 3), the signal is fed to the input HE55 and when the line is disconnected, the phase-to-phase voltage disappears and a logical zero signal appears at its input, and a logical 1 goes to the input ZhM57 and the signal appears at its output logical 1 at time t ₁ . At time t ₆ , a logic 0 signal appears at its output and, from the fall of the trailing edge of the pulse, the LM58 is triggered. According to figure 3, for the interval t ₆ -t _{1 the} signal U ₄ is equal to logical 1. At intervals t ₃ -t ₂ and t ₅ -t ₄ at the output of the low-pass filter 61 a constant voltage of logical 1 U ₁ from the output PU2 is supplied to the output I74, because there are logical 1 at both its inputs. At the output of PDN77, the signals of the orthogonal components of PU2 are then allocated to the information inputs K66 and K67. From the leading edge of the output voltage of the low-pass filter 61 (moment t ₂ in FIG. 2), logic 1 is supplied to the control input K66 at the top output of Tg80. At time t _{4, the} leading edge of the pulse at the lower output Tg80 is set to logical 1, which is fed to the control input K67. Thus, signals proportional to the orthogonal components of PU2 through K66 and K67 are recorded by IE85 and IE86. At time t ₆ from the trailing edge of the output pulse, the ZhM58 is triggered by the ZhM59 and then the orthogonal components of PU3 are recorded in IE87 and IE88 similarly to the recording of orthogonal components of PU2. The orthogonal components of PU4 are also recorded in IE89 and IE90.

Claims (1)

A method for measuring the distance to a short circuit in high-voltage electric networks, which consists in measuring the minimum value of the emergency voltage vector and determining the ratio of the reactive component of voltage to current, characterized in that the minimum interfacial vector values of line voltages are measured at different points and using known values the complex resistances between these points determine the maximum vector values of the difference in phase currents at these sites kah, using which, find the maximum phase difference of the damaged area located in the immediate vicinity of the short circuit point; determine the distance to the short circuit point from the voltage measuring point closest to it, where the received current flows.

Images