RU2330298C2 - Method for detection of damage point in power transmission and communication lines and device for its implementation - Google Patents

Abstract

FIELD: power engineering.

SUBSTANCE: probing voltage pulses are sent to the line. Damage point is determined by time delay of reflected pulse in respect to the probing one. Then quazi-continuous oscillating signal is generated, which represents voltage pulses, the instant values of voltage of which are received by sum of harmonic components of two and more frequencies. Reflected signal is received in moments of time, which correspond to preliminarily determined point of damage. Distance to damage point is specified by phase-frequency spectrum. Device contains computing unit and the following devices connected to it - generator of probing pulses, receiver, indication unit, controlled switch with control channel from computing unit. Switch is arranged with the possibility of connection to controlled power transmission or communication line. At that at least one outlet of probing pulses generator and one inlet of receiver are connected to the switch.

EFFECT: expansion of functional resources.

5 cl, 5 dwg

Description

The invention relates to the electric power industry and can be used to create devices for determining the location of damage (OMP) of power lines and communications (power lines and S).

Known methods of OMP power lines and C [A.S. USSR No. 1385108, A.S. USSR No. 1531037, RF Patent No. 2073253] are based on the pulse method without the use of modulation: unmodulated sounding signals are sent to the line, signals reflected from inhomogeneities of fault locations are received, and the damage location is determined by the time delay of the signals reflected from the fault location relative to the sounding ones.

The disadvantage of these known methods is the low accuracy of the measurements.

The closest technical solution to the proposed method and device is the OMP power transmission line and C and a device for its implementation [RF Patent No. 2073253, Cl. G01R 31/11, 1997]. The method is based on sending probing voltage pulses to the line, receiving reflected pulses, storing the voltage values from the line for each time delay value, determining the place of damage by the time delay of the reflected pulse relative to the probing one. In order to increase the reliability and accuracy of measurements, to eliminate spurious reflections from the input line, the output impedance of the probe pulse generator is matched with the line impedance cyclically: in the first cycle, half the amplitude of the probe pulse is stored when the line is turned off, and in the second cycle, the probe pulse amplitude is measured at an arbitrary value output resistance at the input of the connected line, subtract from it the value stored in the first matching cycle , the sign and value of the subtraction result are stored, in the third matching cycle, the wave resistance value is calculated from the measurement results of the first and second cycles and the output resistance of the probe pulse generator is set with its digital code with a given accuracy.

A device for implementing the method comprises a synchronization unit, a computing unit, a probe pulse generator, made in the form of a series-connected probe pulse generator and a controlled output impedance unit, an indication unit.

This method and its device also have low measurement accuracy.

The objective of the invention was to increase the accuracy of measuring the distance to the place of damage.

This problem is solved by the method of power transmission line OMP and C, which consists in sending voltage probes from the generator to the line while matching the output impedance of the latter with the wave impedance of the line in accordance with a given range of wave impedances and the required accuracy of matching, receiving reflected pulses, determining the location of damage by time delay reflected pulse relative to the probing, then additional probing voltage pulses are emitted, instantaneous voltage values are oryh prepared one or a sum of several harmonic components further receiving reflected pulses at timings corresponding to the predetermined site of injury, is subjected to additional pulses received reflected spectral analysis and information about the fault location specify values for phase-frequency spectra.

The essence of the method consists in the additional use of pulses for OMP power lines and C, allowing to implement phase methods of radio range-finding and to clarify the distance to the place of damage, determined previously on the basis of pulse methods [Radio engineering: Encyclopedia / Ed. Yu.L. Mazor, E.A. Machusky, V.I. Pravda. - M .: Publishing house "Dodeca - XXI", 2002. - S.472-474].

Since the error in measuring the range with WMD is directly related to the error in measuring the time delay, it is possible to characterize the increase in the accuracy of measuring the range by reducing the errors in measuring the time delay.

It is known [Theoretical Foundations of Radar. Ed. Shirmana Y.D. Textbook for High Schools - M .: Soviet Radio, 1970, p. 190] that the standard error (standard deviation) of the measurement of the delay time is determined by the expression

where q is the signal-to-noise ratio, P _E is the effective signal bandwidth.

Moreover, for pulsed measurements without modulation, the band of P _E1 signal [Theoretical basis of radar. Ed. Shirmana Y.D. Textbook for High Schools - M .: Soviet Radio, 1970, pp. 340-343] is determined by the pulse duration

таким образом

in this way

When using phase ranging methods using, for example, two-frequency radiation (f ₁ , f ₂ ), the effective signal band P _E2 has the largest width [Theoretical fundamentals of radar. Ed. Shirmana Y.D. Textbook for High Schools - M .: Soviet Radio, 1970, p. 191] and is equal to

P _E2 = π (f ₂ -f ₁ ),

where π = 3.1415926, and the potentially achievable accuracy,

Let us find the ratio σ _τ1 / σ _τ2 , showing an increase in the accuracy of measurements of the delay time using phase methods

In the paths of high-frequency processing of power lines, probing signal radiation is possible within the band П _u = (f ₂ -f ₁ ) = 10 ⁶ Hz = 1 MHz [G. Shalyt Determination of places of damage in electrical networks. - M .: Energoatomizdat, 1982].

Thus, the phase methods of radio range-finding have π = 3.1415926 times higher potential accuracy of measuring the delay time and, therefore, the accuracy of OMP. For example, with the same signal to noise ratio q, for pulsed measurements without modulation with a signal bandwidth P _E1 = 500 kHz, the error in the OMP according to the expression

σ _R = υσ _τ ,

where σ _R is the error in the distance to the place of damage, υ≈0.98c≈294000000 m / s,

υ is the propagation velocity of electromagnetic waves in power lines and C, s is the speed of light,

will be 588 meters, and when using phase ranging methods using two-frequency radiation (f ₁ -f ₂ ) = 500 kHz, it will be 187 meters.

On the other hand, in the proposed OMP method for power transmission lines and C, pulse and phase ranging methods are used sequentially, which have different and independent instrumental errors. Therefore, their joint use will increase the accuracy of measuring the range of weapons of mass destruction.

The proposed method can be implemented using a device containing a computing unit and a probe pulse generator associated with it, a receiver and an indication unit, in which a controllable switch with a control channel from the computing unit is installed, configured to be connected to a power line or communication, at least one output of the probe pulse generator and one receiver input are connected to the indicated switch.

The probe pulse generator can be assembled from the following elements: a controlled resistance block (available in the prototype), a memory block, a digital-to-analog converter, and a power amplifier.

It is advisable to use a microcomputer containing an address, data and control bus, a processor module, a keyboard control device and a memory module as a computing unit, and a device containing a mixer and an analog-to-digital converter with controlled amplification as a receiver.

The claimed technical solution is illustrated by drawings.

Figure 1 presents a block diagram of a device for determining the location of damage to power lines and communications. Figure 2 and 3 presents the device, respectively, of the computing unit and the receiver. Figures 4 and 5 show examples of quasicontinuous oscillations.

A device for determining the location of damage to power and communication lines contains a probe pulse generator 1, consisting of a control output impedance block 2, a memory block 3, a digital-to-analog converter 4 and a power amplifier 5, a receiver 6, a computing unit 7 (for example, a microcomputer), an indication unit 8 controlled switch 9.

The receiver 6 (figure 3) contains a mixer 10 and an analog-to-digital Converter with controlled gain 11.

Computing unit 7 (figure 2) in the General case may be a microcomputer containing a bus address, data, control 12, the processor module 13, the keyboard control device 14, the memory module 15.

The device operates as follows. At the first stage, the operation of the device is similar to the prototype and unmodulated pulse signals (unmodulated probe pulses) are used.

Before the OMP power line or C procedure, the output impedance of the probe pulse generator 1 (Fig. 1) is matched with the wave impedance of the line connected through the controlled switch 9 to the output of the controlled output impedance block 2. The matching mode is set by block 14 of computing unit 7 (Fig. 2) in accordance with a given range of wave impedances and the required accuracy of matching.

The controlled switch 9 is switched to a mode in which the input of the receiver 6 is blocked for the duration of the emission of the unmodulated probe pulse.

After the process of matching the output impedance of the generator 1 is completed under the influence of the instructions of the microcomputer unit 14, the processor module 13, with the participation of the software stored in the memory module 15, calculates digital codes of discrete values of the unmodulated pulse of a given duration t _u . Digital codes from output 1 of the microcomputer 7 enter the memory unit 3 of the probe pulse generator 1, where they are recorded and stored. The parameters of the probe unmodulated pulse (for example, amplitude, duration, carrier frequency) are selected based on the required measurement accuracy, taking into account the power transmission line and C. Under the influence of control signals from the first output of the microcomputer 7, the digital codes of the samples of the unmodulated pulse are sent to a digital-to-analog converter 4 onwards to a power amplifier 5, at the output of which a probe pulse is formed. Passing through the controlled output impedance block and the controlled switch 9, the pulse enters the line, and from the output of the power amplifier 5, if necessary, to the first input of the receiver and participates as a reference signal for the mixer 10.

In the case of specular reflection from the place of damage (for example, the location of a short circuit in the power transmission line), the reflected pulse will arrive at the input 2 of the receiver 6 with a time delay t _s in relation to the emitted pulse (time of the probe pulse generator start-up). Possible demodulation (conversion to a lower frequency of high-frequency filling) in the mixer 10 of the receiver 6 using the reference signal of the probe pulse generator. From the output of the mixer 10, the reflected signal is fed to the analog-to-digital conversion (ADC) module with a control gain 11 for amplification and digitalization. The gain is controllable, since the gain of module 11 can change under the influence of signals from the input / output of the microcomputer 7 to the input / output of the receiver 6. Digital samples of the received signal through the input / output and address bus, data, control 12 are supplied to the processor module 13 for preliminary calculating the distance to damage. A rough calculation of the distance R to damage is made according to the time delay t _s between the emitted and received unmodulated impulses fixed by block 7 of the microcomputer according to the formula

where υ is the propagation velocity of electromagnetic waves in power lines.

The results of a preliminary calculation of the distance to the place of damage can be displayed on display unit 8.

To clarify a rough estimate of the distance to the place of damage, it is possible to emit several single unmodulated pulses or their bursts with subsequent joint processing. For each of these radiations, it is advisable to use the procedure of matching wave impedance.

At the second stage, the operation of the device is based on the use of phase ranging methods.

Range measurement by phase methods is based on measuring the phase increment of the emitted harmonic oscillations of the stabilized frequency during the delay time of the reflected signal [Radio engineering: Encyclopedia / Ed. Yu.L. Mazor, E.A. Machusky, V.I. Pravda. - M: Publishing house "Dodeca-XXI", 2002 - p. 473].

For example, the transmitter emits a sinusoidal frequency oscillation f ₀ with some initial phase φ ₀

φ _per = 2πf ₀ t + φ ₀ .

The reflected signal enters the receiver with phase

φ _CR = 2πf ₀ (tt _h ) + φ ₀ + Δφ,

where Δφ is the phase shift upon reflection (as a rule, it is close to 180 °).

The delay time t _s , which uniquely determines the distance to the place of damage R, is calculated as

and the phase advance will be

Given the well-known Δφ, we arrive at the equations

or

linking the desired range to damage R with the measured phase difference θ '= θ + Δφ.

называются масштабными, поскольку от них зависит масштаб измерения дальности, т.е. коэффициент между измеряемым фазовым сдвигом θ' и дальностью до места повреждения R.Frequency f ₀ and wavelength

are called large-scale, since the scale of measuring distance depends on them, i.e. the coefficient between the measured phase shift θ 'and the distance to the place of damage R.

Through the phase intervals θ '= 2π, the harmonic oscillation, and with it the phase meter readings are repeated, while the range of the unambiguous range measurement will be

Choosing the wavelength in accordance with this expression, it is possible to provide measurements of the distance to the place of damage in any ranges. So, for example, for R _max = R _od = 300 km, a wavelength of λ = 600 km and a corresponding scale frequency f ₀ = 500 Hz are required. In this case, the instrumental accuracy of the range measurement turns out to be measured and amounts to 0.8 km for each degree of the phase meter scale.

An essential feature and methodological limitation of the application of phase methods for the power transmission line OMP and C is the need for diversity reception - transmission during the emission of continuous oscillations. It is impossible to realize simultaneous emission and reception of harmonic oscillations at a fixed frequency in power lines [Theoretical Foundations of Radar. Ed. V.E.Dulevich. - M .: Owls. Radio, 1964, p. 25]. To overcome this limitation, the authors propose the use of quasi-continuous oscillations [Shirman Y.D., Manzhos V.N. The theory and technique of processing radar information against the background of interference, - M .: Radio and communications, 1984, p.114] (for example, Fig.4, 5) with the subsequent restoration of continuous oscillation.

In this case, the initial continuous oscillation is replaced by the corresponding periodic segments (pulses) (Figs. 4, 5). The period of following the segments (pulses), their duration and duty cycle is determined depending, for example, on the length of the power line or C, the estimated distance to the place of damage, the required accuracy of the OMP power line and C.

The disadvantages of the simplified phase method:

- a small range of unambiguous range measurement when using high-frequency oscillations;

- unknown value of the phase shift Δφ upon reflection from unexplained damage;

- are eliminated through the use of multi-frequency signals [Radio engineering: Encyclopedia / Ed. Yu.L. Mazor, E.A. Machusky, V.I. Pravda. - M: Publishing house "Dodeka-XXI", 2002 - p. 473-474].

So, with two-frequency phase ranging use the scale frequency generated as a result of beats [Theoretical fundamentals of radar. Ed. J.D. Shirman. Textbook for universities. - M .: Owls. Radio, 1970, p. 191, Theoretical Foundations of Radar. Ed. V.E.Dulevich. - M .: Owls. Radio, 1964, pp.22-25] of sinusoidal oscillations of two carrier frequencies f ₁ and f ₂ with the initial phases ψ ₁ and ψ ₂ .

In the annex to the proposed device (Fig. 1), a quasi-continuous signal representing pulses of the total oscillations of the frequencies f ₁ and f _{2 is} emitted in the power transmission line (Fig. 5). Blocks 7, 3, 4, 5 participate in the formation of such pulses, and the controlled resistance block 2 and the controlled switch 9 provide their coordinated emission at the required time instants.

The controlled switch 9 is involved not only in the emission of pulsed signals, but also in the reception of reflected signals only at predetermined time periods. These predetermined time periods are determined by the distance R to the damage site, determined at the first stage of the device operation, measurement errors of the damage site of the first stage, taking into account the propagation velocity of electromagnetic waves in power lines υ. Thus, the control switch 9 in accordance with the control signals of the computing unit 7 provides a combination of radiation and reception of signals when implementing the phase methods of OMP transmission lines and C.

The input of the receiver 6 receives the reflected signals from the area of the alleged location of the damage and the following procedures are performed to determine the distance to the damage.

The frequencies f ₁ , f ₂ (for two-frequency phase ranging) are selected close in values and for them the phase shifts due to reflection from the place of damage and delay in the components of the device can be considered the same.

After converting to digital form in the receiver 6, the reflected signal enters the computing unit 7 to calculate the phase-frequency spectrum (PSF). The PSF of the reflected signal can be obtained using, for example, discrete (fast) Fourier transform algorithms. In this case, the phase difference of the components of the PSF of the reflected signal at frequencies f ₁ and f ₂ will be associated with the delay time t _s = 2R / υ and be

φ ₁₁ = 2π (f ₁ -f ₂ ) (t-2R / υ) + (ψ ₁ -ψ ₂ ) = 2πΔf (t-2R / υ) + (ψ ₁ -ψ ₂ ).

The phase difference θ between the frequency components during radiation

φ ₁ = 2π (f ₁ -f ₂ ) t + (ψ ₁ -ψ ₂ ) = 2πΔft + (ψ ₁ -ψ ₂ )

and when receiving the reflected signal φ ₁₁ characterizes the range to the place of damage

θ = φ ₁ -φ ₁₁ = 2πΔf (t-t + 2R / υ) + (ψ ₁ -ψ ₂ ) - (ψ ₁ -ψ ₂ ) = 4πΔfR / υ = 4πR / Δλ.

Thus, when using the two-frequency method, the distance to the place of damage can be calculated by block 7 according to the formula

The calculation results are induced by block 8.

The combined determination of the distance to the place of damage during the phased use of unmodulated radiation and phase methods gives a more accurate result of the OMP of the power transmission line and C.

The device (figure 1) allows you to implement other (multi-frequency) phase ranging methods to increase the accuracy of the OMP of the power transmission lines and C. The choice of method is determined by the requirements for the accuracy of the OMP of the power lines and C and the measurement conditions.

Claims (5)

1. The method of determining the location of damage to power lines and communications, which consists in sending a probe voltage pulse to the line from the generator when matching the output impedance of the latter with the wave impedance of the line in accordance with a given range of wave impedances and the required accuracy of matching, receiving reflected pulses, determining the location of damage by the time delay of the reflected pulse relative to the probe, characterized in that a quasi-continuous oscillating signal is further emitted , which is a voltage pulse, the instantaneous values of which are obtained by the sum of the harmonic components of two or more frequencies, receive the reflected signal at times corresponding to a predetermined location of damage, calculate the phase-frequency spectrum of the reflected signal and specify the distance to the place of damage from the phase-frequency spectrum. 2. A device for determining the location of damage to power lines and communications, comprising a computing unit and a probe pulse generator associated with it, a receiver and an indication unit, characterized in that it comprises a controllable switch with a control channel from the computing unit, configured to connect to a power line or communication, wherein at least one output of the probe pulse generator and one input of the receiver are connected to said switch. 3. The device according to claim 2, characterized in that the probe pulse generator comprising a controlled resistance unit also comprises a memory unit, a digital-to-analog converter and a power amplifier. 4. The device according to claim 2 or 3, characterized in that the computing unit is made in the form of a microcomputer containing an address, data and control bus, a processor module, a keyboard control device and a memory module. 5. The device according to claim 2 or 3, characterized in that the receiver comprises a mixer and an analog-to-digital converter with controlled amplification.

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