Self-zeroing integration circuit, measurement circuit and method for traveling wave measurement of transmission line

Abstract

The present invention discloses a self-zeroing integration circuit for traveling wave measurement of a transmission line, comprising: a high-speed operational amplifier integration circuit, a low-pass filter circuit, and a second high-precision operational amplifier circuit. An external input signal passes through the high-speed operational amplifier integration circuit, the low-pass filter circuit, and the second high-precision operational amplifier circuit in sequence to obtain an amplified signal V3, and the amplified signal V3 is fed back to the non-inverting input terminal of the high-speed operational amplifier integration circuit. The present invention also discloses a measurement circuit and method applied to traveling wave measurement of a transmission line fault. The self-zeroing integration circuit of the present invention automatically eliminates the DC bias caused by the operational amplifier offset voltage, bias current, and temperature drift by compensating the DC bias to the input stage of the integration operational amplifier, improving the measurement accuracy and dynamic range of the traveling wave signal.

Description

Technical Field

[0001] The present invention relates to the field of line fault measurement, and particularly to a self-zeroing integration circuit, a measurement circuit and a method applied to traveling wave measurement of a transmission line fault. Background Art

[0002] After a transmission line fails, the rapid location of the fault is a long-term problem faced by power operation and maintenance units. The traveling wave generated during a transmission line fault can be used for accurate fault location. At this time, the accurate acquisition of the traveling wave signal during a transmission line fault becomes a key factor. The high-voltage transmission line is the lifeblood of the power system. After a line fails, quickly removing the faulty line and promptly finding the fault point for repair is the goal that relay protection workers have been pursuing.

[0003] However, so far, whether the transmission line protection uses power frequency components or transient high-frequency components, it can only determine the area where the fault occurs and can only achieve the purpose of cutting off the fault. Although the microcomputer distance protection can give the fault distance, it cannot meet the production needs due to low accuracy. To promptly find the fault point and repair the line, a special fault distance measurement device still needs to be equipped. The two devices have many similar functional modules, which increases the line investment and the role of the device cannot be fully exerted.

[0004] When a power line transmits electric energy, it propagates in the form of electromagnetic waves. Therefore, traveling waves can be used for fault distance measurement. A traveling wave is a transmission state of a plane wave on a transmission line, and its amplitude changes exponentially along the propagation direction, and its phase changes linearly along the transmission line. The traveling wave distance protection uses the traveling wave after a transmission line fault, so that the protection device has the characteristic of ultra-high-speed operation; moreover, by using the characteristics of traveling wave reflection and refraction, the fault distance can be accurately calculated, and at the same time, it can be used as both the protection action discrimination quantity and the ranging output result, that is, integrating protection and ranging, effectively solving the above problems.

[0005] A Rogowski coil can be used to sense a traveling wave signal. However, the output voltage signal of the Rogowski coil is proportional to the differential of the traveling wave signal, and the voltage signal output by the Rogowski coil needs to be integrated to obtain a waveform that is exactly the same as the traveling wave signal. However, because the frequency range of the traveling wave signal is wide, a high-bandwidth operational amplifier must be selected for the integrator. The offset voltage and bias current of a high-bandwidth operational amplifier are generally large, and a large offset voltage will be formed at the output end after passing through the integrator, which may directly bias to the power supply rail of the operational amplifier during verification, affecting the measurement accuracy and dynamic range of the traveling wave signal. Summary of the Invention

[0006] In view of the above technical problems, the purpose of the present invention is to provide a self - zero - adjusting integration circuit, a measurement circuit and a method applied to traveling - wave measurement of transmission lines, so as to solve the problem that in the prior art, the offset voltage and bias current directly reach the operational amplifier power supply rail when measuring traveling - wave signals, which affects the measurement accuracy and dynamic range of traveling - wave signals.

[0007] The technical solution adopted by the present invention is as follows:

[0008] A self - zero - adjusting integration circuit for traveling - wave measurement of transmission lines includes: a high - speed operational amplifier integration circuit, a low - pass filter circuit and a second high - precision operational amplifier circuit. Among them, an external input signal passes through the high - speed operational amplifier integration circuit, the low - pass filter circuit and the second high - precision operational amplifier circuit in sequence to obtain an amplified signal V3, and the amplified signal V3 is fed back to the non - inverting input terminal of the high - speed operational amplifier integration circuit.

[0009] Furthermore, it also includes a first high - precision operational amplifier circuit, and the high - speed operational amplifier integration circuit is connected to the low - pass filter circuit through the first high - precision operational amplifier circuit.

[0010] Furthermore, it also includes resistors R1, R2, R5, R6, R7, R8, capacitors C1, C2 and C3. Among them, the inverting input terminal of the high - speed operational amplifier circuit is connected to the external input signal through resistor R1, the connection point between the inverting input terminal of the high - speed operational amplifier integration circuit and resistor R1 is connected to the output terminal of the high - speed operational amplifier integration circuit through capacitor C1, the non - inverting input terminal of the high - speed operational amplifier integration circuit is grounded after passing through resistor R2 and is also connected to the external input signal. The output terminal of the high - speed operational amplifier integration circuit is connected to the non - inverting input terminal of the first high - precision operational amplifier circuit. The inverting input terminal of the first high - precision operational amplifier circuit is connected to the output terminal of the first high - precision operational amplifier circuit. The output terminal of the first high - precision operational amplifier circuit is connected to the inverting input terminal of the second high - precision operational amplifier circuit through the low - pass filter circuit and resistor R5 in sequence. The connection point between resistor R3 and resistor R4 is grounded. The connection point between resistor R5 and the inverting input terminal of the second high - precision operational amplifier circuit is connected to the output terminal of the second high - precision operational amplifier circuit through resistor R6. The non - inverting input terminal of the second high - precision operational amplifier circuit is grounded through resistor R7. The output terminal of the second high - precision operational amplifier circuit is connected to the non - inverting input terminal of the high - speed operational amplifier integration circuit through resistor R8.

[0011] Furthermore, the low - pass filter circuit includes resistors R3, R4, capacitors C2 and C3. Among them, the output terminal of the first high - precision operational amplifier circuit is connected to the inverting input terminal of the second high - precision operational amplifier circuit through resistor R3, resistor R4 and resistor R5 in sequence. The connection point between resistor R3 and resistor R4 is grounded through capacitor C2. The connection point between resistor R4 and resistor R5 is grounded through capacitor C3.

[0012] A measuring circuit for traveling wave measurement of a transmission line, comprising the self-zeroing integration circuit and the Rogowski coil. The input end of the Rogowski coil is connected to the transmission line to be measured, the inverting input end of the high-speed op-amp integration circuit is connected to the output end of the Rogowski coil through the resistor R1, and the non-inverting input end of the high-speed op-amp integration circuit is connected to the output end of the Rogowski coil through the resistor R2.

[0013] Further, the Rogowski coil adopts a high-frequency Rogowski coil.

[0014] A method for traveling wave measurement of a transmission line, using the circuit for traveling wave measurement of a transmission line, comprising:

[0015] Inducing the traveling wave signal of the transmission line to be measured through the Rogowski coil;

[0016] The traveling wave signal is successively integrated by the high-speed op-amp integration circuit to obtain the output signal V0, and then successively passes through isolation, filtering and reverse amplification to obtain the amplified signal V3, and the DC bias voltage of the output signal V0 of the high-speed op-amp integration circuit is adjusted by the amplified signal V3 until the DC bias voltage of the output signal V0 is adjusted to zero.

[0017] Further, specifically including:

[0018] Inducing the traveling wave signal of the transmission line to be measured through the Rogowski coil;

[0019] Obtaining the output signal V0 through the high-speed op-amp integration circuit for the induced traveling wave signal;

[0020] Extracting the DC signal V1 from the obtained output signal V0 through the high-precision op-amp circuit;

[0021] Obtaining the DC signal component V2 of the DC signal V1 through the low-pass filter circuit for the extracted DC signal V1;

[0022] Obtaining the amplified signal V3 through the high-precision op-amp circuit for reverse amplification of the obtained DC signal component V2;

[0023] Adjusting the DC bias voltage of the output signal V0 of the high-speed op-amp circuit by the amplified signal V3 until the DC bias voltage of the output signal V0 is adjusted to zero.

[0024] Further, the step of adjusting the DC bias voltage of the output signal V0 of the high-speed op-amp circuit by the obtained amplified signal V3 includes:

[0025] Feeding back the amplified signal V3 to the non-inverting input end of the high-speed op-amp integration circuit.

[0026] Further, the amplified signal V3 is -5 times the DC signal component V2.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] By setting up a self-zeroing integration circuit, the present invention compensates the DC bias to the input stage of the integrating operational amplifier, automatically eliminates the DC bias caused by the operational amplifier offset voltage, bias current and temperature drift, and improves the measurement accuracy and dynamic range of the traveling wave signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a schematic diagram of the measurement circuit for measuring the traveling wave of the transmission line of the present invention;

[0030] Figure 2 is a schematic flow chart of the method for measuring the traveling wave of the transmission line of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] Next, in combination with the drawings and specific embodiments, the present invention will be further described. It should be noted that, on the premise of no conflict, the following-described embodiments or technical features can be arbitrarily combined to form new embodiments.

[0032] Embodiment:

[0033] Please refer to Figure 1-2 As shown, a self-zeroing integration circuit for measuring the traveling wave of a transmission line includes: a high-speed operational amplifier integration circuit, a low-pass filter circuit, and a second high-precision operational amplifier circuit. The external input signal passes through the high-speed operational amplifier integration circuit, the low-pass filter circuit, and the second high-precision operational amplifier circuit in sequence to obtain an amplified signal V3, and the amplified signal V3 is fed back to the non-inverting input terminal of the high-speed operational amplifier integration circuit.

[0034] Furthermore, it further includes a first high-precision operational amplifier circuit, and the high-speed operational amplifier integration circuit is connected to the low-pass filter circuit through the first high-precision operational amplifier circuit.

[0035] Specifically, the self-zeroing integration circuit for traveling wave measurement of a transmission line includes a high-speed operational amplifier integration circuit, a first high-precision operational amplifier circuit, a second high-precision operational amplifier circuit, a low-pass filter circuit, resistors R1, R2, R5, R6, R7, R8, capacitors C1, C2, and C3. The inverting input terminal of the high-speed operational amplifier integration circuit is connected to an external input signal through resistor R1. The connection point between the inverting input terminal of the high-speed operational amplifier integration circuit and resistor R1 is connected to the output terminal of the high-speed operational amplifier integration circuit through capacitor C1. The non-inverting input terminal of the high-speed operational amplifier integration circuit is grounded after passing through resistor R2 and is also connected to the external input signal. The output terminal of the high-speed operational amplifier integration circuit is connected to the non-inverting input terminal of the first high-precision operational amplifier circuit. The inverting input terminal of the first high-precision operational amplifier circuit is connected to the output terminal of the first high-precision operational amplifier circuit. The output terminal of the first high-precision operational amplifier circuit is sequentially connected to the inverting input terminal of the second high-precision operational amplifier circuit through the low-pass filter circuit and resistor R5. The connection point of resistors R3 and R4 is grounded. The connection point between resistor R5 and the inverting input terminal of the second high-precision operational amplifier circuit is connected to the output terminal of the second high-precision operational amplifier circuit. The non-inverting input terminal of the second high-precision operational amplifier circuit is grounded through resistor R6. The output terminal of the second high-precision operational amplifier circuit is connected to the non-inverting input terminal of the high-speed operational amplifier integration circuit.

[0036] The design idea of the present invention mainly stems from the following advantages and disadvantages of the high-speed operational amplifier integration circuit: it can respond to high-frequency signals, but has large offset voltage, bias current, and temperature drift, which will cause a DC bias in the integrated output signal V0.

[0037] The high-precision operational amplifier circuit has the following advantages and disadvantages: very small offset voltage, bias current, and temperature drift, but narrow frequency range, but can accurately extract the DC signal we care about.

[0038] Therefore, the automatic zeroing circuit of the present invention compensates the bias to the input stage of the integrating operational amplifier, and can automatically eliminate the bias voltage caused by the offset voltage, bias current, and temperature drift of the operational amplifier.

[0039] Further, the low-pass filter circuit includes resistors R3, R4, capacitors C2, and C3. The output terminal of the first high-precision operational amplifier circuit is sequentially connected to the inverting input terminal of the second high-precision operational amplifier circuit through resistors R3, R4, and R5. The connection point of resistors R3 and R4 is grounded through capacitor C2. The connection point of resistors R4 and R5 is grounded through capacitor C3.

[0040] A circuit applied to traveling wave measurement of transmission line faults, please refer to Figure 1As shown, it includes the self-zeroing integration circuit and the Rogowski coil. The Rogowski coil is a high-frequency Rogowski coil. The input end of the Rogowski coil is connected to the transmission line to be measured. The inverting input end of the high-speed operational amplifier integration circuit is connected to the output end of the Rogowski coil through a resistor R1, and the non-inverting input end of the high-speed operational amplifier integration circuit is connected to the output end of the Rogowski coil through a resistor R2.

[0041] The working principle of the circuit of the present invention applied to the traveling wave measurement of transmission line faults is as follows: The signal output by the high-frequency Rogowski coil passes through a high-frequency operational amplifier integration circuit to obtain an output signal V0. Due to the high offset voltage, bias current, and temperature drift of the high-speed operational amplifier integration circuit, and the high gain of the integration circuit itself for DC signals, the output signal V0 may have a large offset voltage. The output signal V0 is isolated by the first high-precision operational amplifier circuit to reduce the influence of the automatic zeroing circuit on the high-speed operational amplifier integration circuit, and a DC signal V1 with the same waveform as the output signal V0 is obtained.

[0042] Then, the DC signal V1 passes through a low-pass filter circuit. The low-pass filter circuit includes a resistor R3, a resistor R4, a capacitor C2, and a capacitor C3. The DC signal V1 is filtered through the capacitors C2 and C3, and the DC signal component V2 in the DC signal V1 is extracted by the voltage division of the resistors R3 and R4.

[0043] The DC signal component V2 is inversely amplified by 5 times through the second high-precision operational amplifier circuit to obtain an amplified signal V3 with an amplitude opposite to that of the DC signal component V2 and an amplitude 5 times that of the DC signal component V2. Finally, the amplified signal V3 is compensated to the non-inverting input end of the high-speed operational amplifier integration circuit to achieve automatic zeroing.

[0044] The specific zeroing process is as follows:

[0045] Step S1: When the DC bias of the output signal V0 of the high-frequency operational amplifier integration circuit is positive, assume that the output signal V0 of the high-frequency operational amplifier integration circuit has a DC bias of 100 mV. Then, the DC signal V1 also has a DC bias of 100 mV. The DC signal component V2 after passing through the low-pass filter circuit is 100 mV DC, and the inversely amplified amplified signal V3 is -500 mV, which is directly compensated to the non-inverting input end of the high-frequency operational amplifier integration circuit, causing the bias of the output signal V0 of the high-frequency operational amplifier integration circuit to change towards the negative end.

[0046] Step S2: During the process of changing towards the negative end, when the DC bias of the output signal V0 of the high-frequency operational amplifier integrating circuit is negative, if the bias of the output signal V0 is compensated to -50 mV, then the DC signal V1 also has a DC bias of -50 mV. The DC signal component V2 after low-pass filtering is -50 mV DC, and the amplified signal V3 after inverting amplification is 250 mV, which is directly compensated to the non-inverting input terminal of the high-frequency operational amplifier integrating circuit, causing the bias of the output signal V0 of the high-frequency operational amplifier integrating circuit to change towards the positive end, repeating the situation when the DC bias is positive in Step S1.

[0047] In this way, the self-zeroing integrating circuit of the present invention can finally stabilize in only one situation, where the DC bias of the high-frequency operational amplifier integration output is 0 mV, and the zeroing process ends.

[0048] Moreover, when the temperature of the circuit changes, it will cause a change in the bias voltage, resulting in a change in the DC bias of the output signal V0 of the high-frequency operational amplifier integration. After the changed DC bias passes through the isolation, filtering, and inverting amplification of the subsequent circuit, it is fed back to the input terminal, forcibly eliminating the DC bias of the output signal V0, thus completing a self-zeroing integrating circuit that can also achieve self-zeroing when the temperature changes.

[0049] A method applied to the measurement of traveling waves in transmission line faults, using the circuit applied to the measurement of traveling waves in transmission line faults as described above, please refer to Figure 2 as shown, including the following steps:

[0050] Induce the traveling wave signal of the transmission line to be measured through a Rogowski coil;

[0051] Obtain the output signal V0 by passing the induced traveling wave signal through a high-speed operational amplifier integrating circuit;

[0052] Extract the DC signal V1 from the obtained output signal V0 through a high-precision operational amplifier circuit;

[0053] Obtain the DC signal component V2 of the DC signal V1 by passing the extracted DC signal V1 through a low-pass filter circuit;

[0054] Obtain the amplified signal V3 by inverting and amplifying the obtained DC signal component V2 through a high-precision operational amplifier circuit;

[0055] Adjust the DC bias voltage of the output signal V0 of the high-speed operational amplifier circuit through the amplified signal V3 until the DC bias voltage of the output signal V0 is adjusted to zero.

[0056] Preferably, the step of adjusting the DC bias voltage of the output signal V0 of the high-speed operational amplifier circuit through the obtained amplified signal V3 includes:

[0057] Feed back the amplified signal V3 to the non-inverting input terminal of the high-speed operational amplifier integrating circuit.

[0058] Preferably, when the amplified signal V3 is -5 times the DC signal component V2, i.e., V3 = -5V2, the DC bias voltage can be quickly adjusted to zero.

[0059] By setting an integrator automatic zeroing circuit, the present invention compensates the bias to the input stage of the integrating operational amplifier, automatically eliminates the offset voltage caused by the operational amplifier offset voltage, bias current and temperature drift, and improves the measurement accuracy and dynamic range of the traveling wave signal.

[0060] For those skilled in the art, various corresponding changes and deformations can be made according to the technical solutions and concepts described above, and all these changes and deformations should fall within the protection scope of the claims of the present invention.

Claims

1. A self - zeroing integration circuit for traveling - wave measurement of a transmission line, characterized in that, Comprising: A high-speed operational amplifier integrating circuit, a low-pass filter circuit, a first high-precision operational amplifier circuit, and a second high-precision operational amplifier circuit. An external input signal passes through the high-speed operational amplifier integrating circuit, the low-pass filter circuit, and the second high-precision operational amplifier circuit in sequence to obtain an amplified signal V3, and the amplified signal V3 is fed back to the non-inverting input terminal of the high-speed operational amplifier integrating circuit; the high-speed operational amplifier integrating circuit is connected to the low-pass filter circuit through the first high-precision operational amplifier circuit; The self-zeroing integrating circuit for transmission line traveling wave measurement further includes a resistor R1, a resistor R2, a resistor R5, a resistor R6, a resistor R7, a resistor R8, a capacitor C1, a capacitor C2, and a capacitor C3. The inverting input terminal of the high-speed operational amplifier circuit is connected to the external input signal through the resistor R1. The connection point between the inverting input terminal of the high-speed operational amplifier integrating circuit and the resistor R1 is connected to the output terminal of the high-speed operational amplifier integrating circuit through the capacitor C1. The non-inverting input terminal of the high-speed operational amplifier integrating circuit is grounded after passing through the resistor R2 and is connected to the external input signal. The output terminal of the high-speed operational amplifier integrating circuit is connected to the non-inverting input terminal of the first high-precision operational amplifier circuit. The inverting input terminal of the first high-precision operational amplifier circuit is connected to the output terminal of the first high-precision operational amplifier circuit. The output terminal of the first high-precision operational amplifier circuit is connected to the inverting input terminal of the second high-precision operational amplifier circuit through the low-pass filter circuit and the resistor R5 in sequence. The connection point between the resistor R3 and the resistor R4 is grounded. The connection point between the resistor R5 and the inverting input terminal of the second high-precision operational amplifier circuit is connected to the output terminal of the second high-precision operational amplifier circuit through the resistor R6. The non-inverting input terminal of the second high-precision operational amplifier circuit is grounded through the resistor R7. The output terminal of the second high-precision operational amplifier circuit is connected to the non-inverting input terminal of the high-speed operational amplifier integrating circuit through the resistor R8; It further includes a Rogowski coil. The input terminal of the Rogowski coil is connected to the transmission line to be measured. The inverting input terminal of the high-speed operational amplifier integrating circuit is connected to the output terminal of the Rogowski coil through the resistor R1, and the non-inverting input terminal of the high-speed operational amplifier integrating circuit is connected to the output terminal of the Rogowski coil through the resistor R2.

2. The self-zeroing integration circuit for traveling wave measurement of a transmission line according to claim 1, wherein The low-pass filter circuit includes a resistor R3, a resistor R4, a capacitor C2, and a capacitor C3. The output terminal of the first high-precision operational amplifier circuit is connected to the inverting input terminal of the second high-precision operational amplifier circuit through the resistor R3, the resistor R4, and the resistor R5 in sequence. The connection point between the resistor R3 and the resistor R4 is grounded through the capacitor C2, and the connection point between the resistor R4 and the resistor R5 is grounded through the capacitor C3.

3. The self-zeroing integration circuit for traveling wave measurement of a transmission line according to claim 1, wherein The Rogowski coil adopts a high-frequency Rogowski coil.

4. A method for traveling wave measurement of a transmission line, characterized in that, Using the self-zeroing integrating circuit for transmission line traveling wave measurement as described in claim 1, comprising: Inducing the traveling wave signal of the transmission line to be measured through the Rogowski coil; Integrating the voltage of the traveling wave signal through the high-speed operational amplifier integrating circuit in sequence to obtain an output signal V0, then passing through isolation, filtering, and reverse amplification in sequence to obtain an amplified signal V3, and adjusting the DC bias voltage of the output signal V0 of the high-speed operational amplifier integrating circuit through the amplified signal V3 until the DC bias voltage of the output signal V0 is adjusted to zero.

5. The method for measuring traveling waves on a transmission line according to claim 4, wherein the method for measuring traveling waves on a transmission line is characterized in that Specifically including: Obtaining an output signal V0 from the induced traveling wave signal through the high-speed operational amplifier integrating circuit; The obtained output signal V0 is passed through a high-precision operational amplifier circuit to extract the DC signal V1; The extracted DC signal V1 is passed through a low-pass filter circuit to obtain the DC signal component V2 of the DC signal V1; The obtained DC signal component V2 is reversely amplified through a high-precision operational amplifier circuit to obtain the amplified signal V3; The DC bias voltage of the output signal V0 of the high-speed operational amplifier circuit is adjusted by the amplified signal V3 until the DC bias voltage of the output signal V0 is adjusted to zero.

6. The method for traveling wave measurement of a transmission line according to claim 5, characterized in that, The step of adjusting the DC bias voltage of the output signal V0 of the high-speed operational amplifier circuit by the obtained amplified signal V3 includes: The amplified signal V3 is fed back to the non-inverting input terminal of the high-speed operational amplifier integration circuit.

7. The method for traveling wave measurement of a transmission line according to claim 4, characterized in that, The amplified signal V3 is -5 times the DC signal component V2.

Images