CN216411412U - Multiport transmission tower ground resistance measuring equipment - Google Patents
Multiport transmission tower ground resistance measuring equipment Download PDFInfo
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- CN216411412U CN216411412U CN202122639964.9U CN202122639964U CN216411412U CN 216411412 U CN216411412 U CN 216411412U CN 202122639964 U CN202122639964 U CN 202122639964U CN 216411412 U CN216411412 U CN 216411412U
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Abstract
The utility model relates to a multi-port transmission tower ground resistance measuring device which comprises a control operation unit, a power source and a plurality of current measuring units, wherein the power source and the plurality of current measuring units are respectively in signal connection with the control operation unit; the outputs of the Rogowski coil current sensor and the clamp-on current sensor are respectively connected with the input of the control arithmetic unit and are used for respectively measuring induced current signals at different positions of the tower grounded multi-terminal network; the control operation unit is used for controlling and outputting the excitation voltage signal and collecting and calculating the measured induced current signal. The utility model can carry out current measurement of different mode combinations and current measurement of different positions, realizes measurement of current loops with different sizes on site, and has wider applicability.
Description
Technical Field
The utility model relates to the technical field of lightning protection grounding, in particular to a grounding resistance measuring device for a multi-port transmission tower.
Background
Design, handover acceptance and preventive test standards and regulations related to the multi-port transmission tower all require measurement of power frequency grounding resistance. At present, the main method for measuring the grounding resistance of the grounding device of the power transmission line tower is a tripolar method and a clamp meter method, wherein the tripolar method is a principle method, but in the implementation process, due to the hidden engineering characteristics of the grounding device, the unreasonable arrangement of wiring and measuring electrodes brings about larger errors, and in addition, the on-site wiring path is limited, the working strength is high, and the actual operability of the tripolar method is poor. The clamp meter method is popular due to simple operation, and the clamp meter method is actually used for measuring the loop impedance formed by the tower grounding impedance, the tower overhead ground wire and the grounding impedance close to the tower, and is approximate to the grounding impedance of the grounding device of the measured tower under certain conditions. Under the condition that the grounding system is in good contact, the clamp meter method can accurately measure the grounding resistance of the whole leakage channel, and the method is simple, small in workload and high in efficiency. However, when the contact is poor, the measurement error is large, the whole measurement loop is related to a plurality of resistance values, and the position where the overproof resistance value is generated cannot be judged, so that the method has great limitation. In addition, when the traditional clamp meter method is used for testing, the voltage injection coil and the current measurement coil are integrated in the same clamp opening, the mutual inductance effect between the coils cannot be ignored, and the interference degree of the mutual inductance effect can sufficiently influence the measurement precision; the internal diameter of the jaw is small, but the span of the grounding wire grounding body used by most of the existing transmission line towers and electrical equipment is large, and the caliber of the common single-jaw type measuring instrument cannot be measured. And due to principle errors caused by shunt of self resistance and mutual resistance of a tower natural grounding body, the traditional clamp meter method can only be used as an auxiliary measurement method and is limited to use or even forbidden in many places.
In the traditional measurement mode, the transmission tower grounding device is regarded as a single centralized impedance model, so that the measurement mode of the existing grounding impedance measurement equipment is single, and the multi-branch measurement mode is limited. With the continuous understanding and perfection of the grounding circuit model of the transmission tower in the industry, different grounding circuit refinement models are provided, for example, the grounding of a pole foot of the tower is tested when the grounding resistance of the transmission tower is measured, the grounding lead-in wire of the tower is tested, and different test objects have different requirements on test equipment. In view of the above, there is a need to develop a structure of a transmission tower ground impedance measuring apparatus having multiple measuring modes and multiple measuring ports.
SUMMERY OF THE UTILITY MODEL
The utility model provides a multi-port transmission tower grounding resistance measuring device aiming at the technical problems in the prior art, solves the problem that different test objects have different test requirements on a grounding resistance test site, and can carry out different combinations on the measuring means and modes to realize different current measurements and current measurements at different positions.
The technical scheme for solving the technical problems is as follows:
a multi-port transmission tower grounding resistance measuring device comprises a control arithmetic unit, a power source and a plurality of current measuring units, wherein the power source and the plurality of current measuring units are respectively connected with the control arithmetic unit through signals, each current measuring unit comprises a Rogowski coil current sensor and a clamp-shaped current sensor,
the input of the power source is connected with the output of the control arithmetic unit and is used for outputting an excitation voltage signal to the measurement loop;
the outputs of the Rogowski coil current sensor and the pincerlike current sensor are respectively connected with the input of the control operation unit and are used for respectively measuring induced current signals at different positions of a tower grounded multi-terminal network;
the control operation unit is used for controlling and outputting the excitation voltage signal and collecting and calculating the measured induced current signal.
Furthermore, the control operation unit comprises an integral amplification unit, a multi-way switch K, an active filter unit, an analog-to-digital conversion unit and a central processing and control unit which are connected in sequence, the output of the current measurement unit is connected with the input of the integral amplification unit,
the integral amplification unit is used for carrying out integral amplification on the current signal acquired by the current measurement unit;
the multi-way switch K is used for controlling the on-off of the induced current signal acquisition channel;
the active filtering unit is used for filtering clutter interference on the collected induced current signals;
the analog-to-digital conversion unit is used for performing analog-to-digital conversion on the acquired induced current signals to generate digital signals;
the central processing and control unit is used for calculating and displaying the acquired digital signals.
Furthermore, the integral amplification unit comprises an integral circuit and a current-voltage conversion circuit, the output end of the integral circuit and the output end of the current-voltage conversion circuit are connected with the plurality of signal acquisition channels of the multi-way switch K in a one-to-one correspondence manner, the input end of the integral circuit is connected with the output end of the Rogowski coil current sensor, and the input end of the current-voltage conversion circuit is connected with the output end of the pincer-shaped current sensor; the integrating circuit comprises a resistor R1, a capacitor C1 and an operational amplifier U1, wherein the inverting input end of the operational amplifier U1 is connected with the output end of the Rogowski coil current sensor, the non-inverting input end of the operational amplifier U1 is grounded, the output end of the operational amplifier U1 is connected with the multi-way switch K, and the resistor R1 and the capacitor C1 are respectively connected between the inverting input end of the operational amplifier U1 and the output end of the operational amplifier U1 in parallel; the current-voltage conversion circuit comprises a resistor R2 and an operational amplifier U2, the non-inverting input end of the operational amplifier U2 is grounded, the inverting input end of the operational amplifier U2 is connected with the output end of the pincerlike current sensor, the output end of the operational amplifier U2 is connected with the multi-way switch K, and the resistor R2 is connected between the inverting input end of the operational amplifier U1 and the output end of the operational amplifier U2 in parallel.
Further, the active filtering unit comprises a band-stop filter and a low-pass filter which are connected in series, the input end of the band-stop filter is connected with the output end of the multi-way switch K, and the output end of the low-pass filter is connected with the input end of the analog-to-digital conversion unit; the band-stop filter comprises a resistor R3, a resistor R4, a resistor R5, a capacitor C2, a capacitor C3, a capacitor C4 and an operational amplifier U3, wherein one end of the resistor R3 is connected with a multi-way switch K, the other end of the resistor R3 is connected with the non-inverting input end of the operational amplifier U3 after being connected with a resistor R4 in series, the common point of the resistor R3 and the resistor R4 is connected with a capacitor C2 in series and then grounded, one end of the capacitor C3 is connected with the multi-way switch K, the other end of the capacitor C3 is connected with a capacitor C4 in series and then connected with the non-inverting input end of the operational amplifier U3, the common point of the capacitor C3 and the capacitor C4 is connected with the resistor R5 in series and then grounded, and the inverting input end of the operational amplifier U3 is connected with the output end of the operational amplifier U3; the low-pass filter comprises a resistor R6, a resistor R7, a capacitor C5, a capacitor C6 and an operational amplifier U4, one end of the resistor R6 is connected with the output end of the band elimination filter, the other end of the resistor R6 is connected with the non-inverting input end of the operational amplifier U4 after being connected with a resistor R7 in series, the non-inverting input end of the operational amplifier U4 is connected with the capacitor C6 in series and then grounded, the common point of the resistor R6 and the resistor R7 is connected with the inverting input end of the operational amplifier U4 after being connected with a capacitor C5 in series, the inverting input end of the operational amplifier U4 is connected with the output end of the operational amplifier U4, and the output end of the operational amplifier U4 serves as the output end of the active filter unit.
Further, the power source comprises an excitation voltage generator, a voltage control unit and a power amplification unit which are connected in sequence, the excitation voltage generator, the voltage control unit and the power amplification unit are respectively connected with the output of the control operation unit,
the excitation voltage generator is used for generating an excitation voltage signal;
the voltage control unit is used for adjusting the frequency of the excitation voltage signal;
the power amplification unit is used for adjusting the amplitude of the excitation voltage signal and then outputting the excitation voltage signal.
Further, the voltage control unit comprises a first voltage follower and a second voltage follower which are connected in parallel, the input ends of the first voltage follower and the second voltage follower are respectively connected with the two output ends of the excitation voltage generator, and the output ends of the first voltage follower and the second voltage follower are respectively connected with the input end of the power amplification unit; the first voltage follower comprises an operational amplifier U8, the non-inverting input end of the operational amplifier U8 is connected with the output end of the excitation voltage generator, the inverting input end of the operational amplifier U8 is connected with the output end of the operational amplifier U8, and the output end of the operational amplifier U8 is connected with the input end of the power amplification unit; the second voltage follower comprises an operational amplifier U9, the non-inverting input end of the operational amplifier U9 is connected with the output end of the excitation voltage generator, the inverting input end of the operational amplifier U9 is connected with the output end of the operational amplifier U9, and the output end of the operational amplifier U9 is connected with the input end of the power amplification unit.
Further, the power amplifying unit comprises a voltage power amplifying circuit and a current source circuit, the voltage power amplifying circuit comprises resistors R8-R10, a triode Q1, a triode Q2 and an operational amplifier U5, the non-inverting input end of the operational amplifier U5 is connected with the output end of the first voltage follower, the non-inverting input end of the operational amplifier U5 is connected with the resistor R8 in series and then grounded, the inverting input end of the operational amplifier U5 is connected with the resistor R9 in series and then connected with the output end of the second voltage follower, the output end of the operational amplifier U5 is connected with the control end of a triode Q1 and the control end of a triode Q2, the triode Q1 is connected with a triode Q2 in series, the input end of the triode Q1 is connected with a positive power supply, the output end of the triode Q2 is connected with a negative power supply, the common end of the triode Q1 and the triode Q2 is connected with the reverse-phase input end of the operational amplifier U5 after being connected with a resistor R9 in series, and the common end of the triode Q1 and the triode Q2 serves as the output end of the voltage power amplifying circuit; the current source circuit comprises resistors R11-R20, an operational amplifier U6, an operational amplifier U7, a power switch tube Q3 and a power switch tube Q4, wherein a non-inverting input end of the operational amplifier U6 is connected with a resistor R14 in series and a non-inverting input end of an operational amplifier U7 is connected with an output end of a first voltage follower respectively after being connected with a resistor R16 in series, an inverting input end of the operational amplifier U6 is connected with a resistor R15 in series and an inverting input end of an operational amplifier U7 is connected with an output end of a second voltage follower respectively after being connected with a resistor R17 in series, a non-inverting input end of the operational amplifier U6 is connected with a positive power supply after being connected with a resistor R13 in series, a non-inverting input end of an operational amplifier U7 is connected with a negative power supply after being connected with a resistor R18 in series, an output end of the operational amplifier U6 is connected with a control end of a power switch tube Q3, an output end of the operational amplifier U7 is connected with a control end of the power switch tube Q4, the power switch tube Q4 is connected with a positive power switch tube Q4 in series, the input end of the power switch tube Q3 is connected with the inverting input end of the operational amplifier U6 after being connected with the resistor R12 in series, the output end of the power switch tube Q4 is connected with the negative power supply after being connected with the resistor R20 in series, the output end of the power switch tube Q4 is connected with the inverting input end of the operational amplifier U7 after being connected with the resistor R19 in series, and the common end of the power switch tube Q3 and the power switch tube Q4 serves as the output end of the current source circuit.
Further, the output end of the power source is provided with a voltage coupling output element and a current output port, the voltage coupling output element is connected with the output end of the voltage power amplifying circuit, and the current output port is connected with the output end of the current source circuit.
Further, the voltage coupling output element is a large-caliber jaw.
Furthermore, the control operation unit is provided with an input unit and a display unit for setting system parameters and displaying test data.
The utility model has the beneficial effects that: 1. the special Rogowski coil current sensor and the clamp-on current sensor can realize the measurement of current loops of different sizes and different types on site, and have wide applicability.
2. According to the specific structure of the tower footing of the on-site tower, the input measurement mode of multiple current sensors is adopted, and the support of on-site measurement and state evaluation can be provided for the multi-port network state circuit model of the grounding device of the transmission tower.
Drawings
FIG. 1 is a schematic view of a tested transmission tower grounding device according to the present invention;
FIG. 2 is a schematic diagram of the principle of measuring the tower power frequency grounding resistance according to the present invention;
FIG. 3 is a schematic view of a tower leg current test of a transmission tower according to the present invention;
FIG. 4 is a functional structure composition schematic block diagram of the present invention;
FIG. 5 is a circuit structure diagram of the present invention.
In the drawings, the components represented by the respective reference numerals are listed below:
1. the device comprises a Rogowski coil current sensor, a clamp-shaped current sensor, a power source, a large-caliber jaw 302, a current output port and a control operation unit, wherein the Rogowski coil current sensor 2, the clamp-shaped current sensor 3, the power source 301, the large-caliber jaw, the current output port and the control operation unit 4 are connected in series.
Detailed Description
The principles and features of this invention are described below in conjunction with the following drawings, which are set forth by way of illustration only and are not intended to limit the scope of the utility model.
Fig. 1 is a top view of the grounding device of the tower base of the transmission tower, wherein A, B, C, D is four tower legs mounted on the tower base. Typically the down conductor is connected to the tower legs, to an artificial earth (e.g. the horizontal module electrodes in figure 1) and laid in radial fashion. When the traditional grounding measurement is carried out, the tower grounding is regarded as a single centralized resistance model by the circuit model of the grounding resistance. Because a single tower in reality has a plurality of tower legs, each tower leg corresponds to one tower footing, and the grounding down lead mode of each tower footing is different, if a single measurement mode or single sensing measurement is adopted, the refined tower grounding circuit cannot be comprehensively measured and evaluated. Therefore, the detection equipment has a multi-port measurement function and a flexible installation mode, so that different tower circuit models can be measured, and the real transmission tower grounding impedance can be measured better and accurately. In order to measure the shunt conditions of the tower footing of the transmission tower specifically, the measuring instrument is objectively required to have a multi-port current input testing function, and the design of the sensing unit has good anti-interference capability.
Therefore, the present embodiment provides a multi-port transmission tower ground resistance measuring device as shown in fig. 2, which includes a control arithmetic unit 4, and a power source 3 and a plurality of current measuring units respectively connected to the control arithmetic unit 4 through signals. The current measuring unit is in a non-contact measuring mode and comprises a special Rogowski coil current sensor 1 and a special clamp current sensor 2 shown in figure 2. According to the actual use requirement, the number of the current measuring units can be flexibly set, and fig. 2 exemplifies two sets of rogowski coil current sensors 1 and two sets of clamp current sensors 2.
The input of the power source 3 is connected with the output of the control arithmetic unit 4 and is used for outputting an excitation voltage signal to the measuring loop. As shown in fig. 2, the power source 3 is respectively disposed on the tower leg connected to the natural ground electrode and the ground down-lead connected to the tower leg, and is configured to provide an excitation voltage signal when measuring the natural ground resistance and the artificial ground resistance of the tower leg.
The outputs of the Rogowski coil current sensor 1 and the pincerlike current sensor 2 are respectively connected with the input of the control arithmetic unit 4 and are used for respectively measuring induced current signals at different positions of a multi-terminal network of the tower grounding. As shown in fig. 2, due to the diversification of the grounding circuit model of the tower to be tested, the tower which is naturally grounded can be tested by using the flexible rogowski coil current sensor 1, that is, the tower can be used for measuring the current of the metal framework; and the clamp-on current sensor 2 can be used for testing the grounding down lead of the tower. The pincerlike current sensor 2 is suitable for a jaw with an iron core and can be used for measuring the current of a grounding down conductor branch.
The control arithmetic unit 4 is used for controlling and outputting the excitation voltage signal and collecting and calculating the measured induced current signal. The control operation unit 4 is provided with a plurality of input interfaces to realize simultaneous testing of a plurality of tower legs, for example, simultaneously testing the tower leg a and the tower leg B in fig. 2, and similarly, simultaneously testing the tower leg a, the tower leg B, the tower leg C, and the tower leg D of one tower can be performed to improve the testing accuracy.
The current sensor measurement installation for the particular tower footing and grounded down conductor is shown in fig. 3. The traditional clamp meter type measuring instrument only has one clamp meter or two separated clamp meters, and the clamp meters are small in size. The existing ground wire of the power transmission line tower mostly adopts flat steel type flat opening ground wires, and the width of the flat opening ground wires is 25 mm-40 mm. The traditional circular jaw is inconvenient on site and even cannot measure on a wider flat grounding wire, and even if the traditional circular jaw can be used, the measurement precision is influenced because the gap of the jaw is too large to cause magnetic leakage. As shown in fig. 3, in this embodiment, the dedicated pincerlike current sensor 2 is used to test the artificial grounding electrode of the tower, and the triangular, rectangular, elliptical, and circular pincerlike current sensors 2 can be flexibly set according to the shape and size of the artificial grounding electrode to perform the test. In addition, when measuring the tower main body with a larger caliber, the embodiment adopts the special flexible rogowski coil current sensor 1, and the rogowski coil current sensor 1 is sleeved on the periphery of the tower main body, so that the convenient installation and measurement on the spot can be realized.
In the field actual measurement process, current measurement may be performed by shunting different branches of the transmission tower, so that the novel multi-port transmission tower ground resistance test equipment provided by the embodiment not only meets the portability of the traditional clamp-on-meter method, but also can realize simultaneous measurement of different branch currents, accurately measures the true value of the ground impedance according to different refined tower ground circuit models, and can comprehensively evaluate the ground state of a tower foundation according to the refined circuit models.
For the above purpose, a specific functional structure diagram of the apparatus is shown in fig. 4.
In this embodiment, the power source 3 includes an excitation voltage generator, a voltage control unit, and a power amplification unit, which are connected in sequence, the excitation voltage generator, the voltage control unit, and the power amplification unit are respectively connected to the output of the control operation unit 4,
the excitation voltage generator is used for generating an excitation voltage signal;
the voltage control unit is used for adjusting the frequency of the excitation voltage signal;
the power amplification unit is used for adjusting the amplitude of the excitation voltage signal and then outputting the excitation voltage signal.
As shown in the circuit diagram of fig. 5, the voltage control unit includes a first voltage follower and a second voltage follower connected in parallel, input ends of the first voltage follower and the second voltage follower are respectively connected to two output ends of the excitation voltage generator, and output ends of the first voltage follower and the second voltage follower are respectively connected to an input end of the power amplification unit. Specifically, the first voltage follower comprises an operational amplifier U8, a non-inverting input terminal of the operational amplifier U8 is connected to an output terminal of the excitation voltage generator, an inverting input terminal of the operational amplifier U8 is connected to an output terminal of the operational amplifier U8, and an output terminal of the operational amplifier U8 is connected to an input terminal of the power amplification unit; the second voltage follower comprises an operational amplifier U9, the non-inverting input end of the operational amplifier U9 is connected with the output end of the excitation voltage generator, the inverting input end of the operational amplifier U9 is connected with the output end of the operational amplifier U9, and the output end of the operational amplifier U9 is connected with the input end of the power amplification unit. The operational amplifier U8 and the operational amplifier U9 are used as two voltage buffer circuits for respectively performing voltage buffering on two paths of output of the excitation voltage generator. Because the drive capability of the digital-to-analog conversion circuit of the excitation voltage generator is weak, two voltage followers are formed by the operational amplifier U8 and the operational amplifier U9 so as to drive a voltage power amplification circuit and a current source circuit in a subsequent power amplification unit.
As shown in fig. 5, the power amplifying unit includes a voltage power amplifying circuit and a current source circuit, the voltage power amplifying circuit comprises resistors R8-R10, a triode Q1, a triode Q2 and an operational amplifier U5, the non-inverting input end of the operational amplifier U5 is connected with the output end of the first voltage follower, the non-inverting input end of the operational amplifier U5 is connected with the resistor R8 in series and then grounded, the inverting input end of the operational amplifier U5 is connected with the resistor R9 in series and then connected with the output end of the second voltage follower, the output end of the operational amplifier U5 is connected with the control end of a triode Q1 and the control end of a triode Q2, the triode Q1 is connected with a triode Q2 in series, the input end of the triode Q1 is connected with a positive power supply, the output end of the triode Q2 is connected with a negative power supply, the common end of the triode Q1 and the triode Q2 is connected with the reverse-phase input end of the operational amplifier U5 after being connected with a resistor R9 in series, and the common end of the triode Q1 and the triode Q2 serves as the output end of the voltage power amplifying circuit; the current source circuit comprises resistors R11-R20, an operational amplifier U6, an operational amplifier U7, a power switch tube Q3 and a power switch tube Q4, wherein a non-inverting input end of the operational amplifier U6 is connected with a resistor R14 in series and a non-inverting input end of an operational amplifier U7 is connected with an output end of a first voltage follower respectively after being connected with a resistor R16 in series, an inverting input end of the operational amplifier U6 is connected with a resistor R15 in series and an inverting input end of an operational amplifier U7 is connected with an output end of a second voltage follower respectively after being connected with a resistor R17 in series, a non-inverting input end of the operational amplifier U6 is connected with a positive power supply after being connected with a resistor R13 in series, a non-inverting input end of an operational amplifier U7 is connected with a negative power supply after being connected with a resistor R18 in series, an output end of the operational amplifier U6 is connected with a control end of a power switch tube Q3, an output end of the operational amplifier U7 is connected with a control end of the power switch tube Q4, the power switch tube Q4 is connected with a positive power switch tube Q4 in series, the input end of the power switch tube Q3 is connected with the inverting input end of the operational amplifier U6 after being connected with the resistor R12 in series, the output end of the power switch tube Q4 is connected with the negative power supply after being connected with the resistor R20 in series, the output end of the power switch tube Q4 is connected with the inverting input end of the operational amplifier U7 after being connected with the resistor R19 in series, and the common end of the power switch tube Q3 and the power switch tube Q4 serves as the output end of the current source circuit.
The resistors R8-R10, the triodes Q1-Q2 and the operational amplifier U5 form a voltage power amplifying circuit, and because the output voltage ratio of the digital-to-analog conversion circuit is small, generally 1-2V, and the load capacity is poor, a small signal needs to be amplified to 20V through the voltage power amplifying circuit, and the small signal is used for driving a voltage coupling output element, such as a voltage coupling sensor, of a subsequent output end. The resistors R11-R20, the power switch tube Q3, the power switch tube Q4, the operational amplifier U6 and the operational amplifier U7 form a current source circuit which is used for converting weak voltage signals into large current signals. Because the output voltage of the digital-to-analog conversion circuit is relatively small, generally 1-2V, and the load capacity is poor, a small voltage signal needs to be converted into a current signal through a current source circuit for being directly output to a tested grounding object.
In this embodiment, the output end of the power source 3 is respectively provided with a voltage coupling output element and a current output port 302, and the voltage coupling output element is connected to the output end of the voltage power amplifying circuit and is used for outputting an amplified voltage signal; the current output port 302 is connected to the output end of the current source circuit, and is used for directly outputting the converted current signal.
Further, the voltage coupling output element is a large-caliber jaw 301, and the requirement of applying induced potential on a tower metal framework is met.
The multi-port transmission tower ground resistance testing device is provided with a current output port 302, a measuring loop can be disconnected, and the current output port 302 is connected in series with the measuring loop, so that current is directly output and applied to the measuring loop; or an excitation voltage is generated in the measuring loop by means of inductive coupling using the large-diameter jaw 301. The device is controlled by a central processing and control unit of the device, and the excitation voltage generator unit, the voltage control unit and the power amplification unit are used for setting the output frequency and the amplitude. Further, the frequency of the excitation voltage signal output by the power source 3 is 50 Hz-1 kHz.
The frequency of the conventional clamp meter method tester is 1-3 kHz and is far higher than 50 Hz. The high frequency is mainly used for filtering the power frequency interference in the measuring circuit through a high pass filter, and meanwhile, the power of the exciting circuit is small in order to induce measuring current in the exciting loop more easily, and the induced current is generally in the mA order.
The improved excitation source can firstly reduce the frequency of an excitation signal, and in addition, a power amplification unit is used for inducing a larger current signal in a measuring loop when an excitation voltage signal is provided for the measuring loop in a voltage coupling output mode. The frequency of the excitation voltage signal can be between 50Hz and 1kHz, so that the power frequency can be avoided, the measurement result can be closer to the power frequency, and the power frequency equivalence of the measurement result is improved. The power amplification unit greatly improves the energy of the induction signal, and induces a measurement voltage with the magnitude of more than 20mV in the measurement loop. When the direct current output is used for providing an excitation voltage signal for the measuring loop, the current of more than 100mA can be applied to the measuring loop, and the signal-to-noise ratio is further improved.
As shown in fig. 4, in this embodiment, the control operation unit 4 includes an integration amplification unit, a multi-way switch K, an active filtering unit, an analog-to-digital conversion unit, and a central processing and control unit, which are connected in sequence, an output of the current measurement unit is connected to an input of the integration amplification unit,
the integral amplification unit is used for carrying out integral amplification on the current signal acquired by the current measurement unit;
the multi-way switch K is used for controlling the on-off of the induced current signal acquisition channel so as to realize measurement in multiple modes;
the active filtering unit is used for filtering clutter interference on the collected induced current signals;
the analog-to-digital conversion unit is used for performing analog-to-digital conversion on the acquired induced current signals to generate digital signals;
the central processing and control unit is used for calculating and displaying the acquired digital signals.
As shown in fig. 4 to 5, the integral amplifying unit includes an integrating circuit and a current-voltage converting circuit, the output end of the integrating circuit and the output end of the current-voltage converting circuit are connected to the multiple signal collecting channels of the multi-way switch K in a one-to-one correspondence, the input end of the integrating circuit is connected to the output end of the rogowski coil current sensor 1, and the input end of the current-voltage converting circuit is connected to the output end of the clamp current sensor 2. Specifically, the integrating circuit includes resistance R1, electric capacity C1 and operational amplifier U1, the output of rogowski coil current sensor 1 is connected to the inverting input end of operational amplifier U1, the non inverting input end ground connection of operational amplifier U1, the output of operational amplifier U1 is connected multi-way switch K, resistance R1 and electric capacity C1 connect in parallel respectively between the inverting input end of operational amplifier U1 and the output of operational amplifier U1. The capacitor C1, the resistor R1, the operational amplifier U1 and the internal resistance of the rogowski coil current sensor 1 form an integrating circuit, and the integrating circuit is used for integrating the signal input from the rogowski coil current sensor 1 to obtain an output voltage proportional to the primary current. The current-voltage conversion circuit comprises a resistor R2 and an operational amplifier U2, the non-inverting input end of the operational amplifier U2 is grounded, the inverting input end of the operational amplifier U2 is connected with the output end of the pincerlike current sensor 2, the output end of the operational amplifier U2 is connected with the multi-way switch K, and the resistor R2 is connected between the inverting input end of the operational amplifier U1 and the output end of the operational amplifier U2 in parallel. The resistor R2 and the operational amplifier U2 form a current-voltage conversion circuit, the clamp current sensor 2 outputs a current signal in a turn ratio relation with primary current, and the current signal needs to be converted into a voltage signal through the circuit for measurement.
As shown in fig. 5, the active filtering unit includes a band-stop filter and a low-pass filter connected in series, an input end of the band-stop filter is connected to an output end of the multi-way switch K, and an output end of the low-pass filter is connected to an input end of the analog-to-digital converting unit; the band-stop filter comprises a resistor R3, a resistor R4, a resistor R5, a capacitor C2, a capacitor C3, a capacitor C4 and an operational amplifier U3, wherein one end of the resistor R3 is connected with a multi-way switch K, the other end of the resistor R3 is connected with the non-inverting input end of the operational amplifier U3 after being connected with a resistor R4 in series, the common point of the resistor R3 and the resistor R4 is connected with a capacitor C2 in series and then grounded, one end of the capacitor C3 is connected with the multi-way switch K, the other end of the capacitor C3 is connected with a capacitor C4 in series and then connected with the non-inverting input end of the operational amplifier U3, the common point of the capacitor C3 and the capacitor C4 is connected with the resistor R5 in series and then grounded, and the inverting input end of the operational amplifier U3 is connected with the output end of the operational amplifier U3; the low-pass filter comprises a resistor R6, a resistor R7, a capacitor C5, a capacitor C6 and an operational amplifier U4, one end of the resistor R6 is connected with the output end of the band elimination filter, the other end of the resistor R6 is connected with the non-inverting input end of the operational amplifier U4 after being connected with a resistor R7 in series, the non-inverting input end of the operational amplifier U4 is connected with the capacitor C6 in series and then grounded, the common point of the resistor R6 and the resistor R7 is connected with the inverting input end of the operational amplifier U4 after being connected with a capacitor C5 in series, the inverting input end of the operational amplifier U4 is connected with the output end of the operational amplifier U4, and the output end of the operational amplifier U4 serves as the output end of the active filter unit.
The capacitor C2, the capacitor C3, the capacitor C4, the resistor R3, the resistor R4, the resistor R5 and the operational amplifier U3 form a double T wave trap, namely a band elimination filter, which is used for filtering power frequency interference signals in the detected signals; the capacitor C5, the capacitor C6, the resistor R6, the resistor R7 and the operational amplifier U4 form a second-order low-pass filter, and the second-order low-pass filter is used for filtering high-frequency noise signals generated by modules such as a switching power supply and a digital circuit in a system and improving the signal-to-noise ratio of the system.
In this embodiment, the control operation unit 4 is provided with an input unit and a display unit, and is used for setting system parameters, inputting control instructions, displaying test data, and the like.
In this embodiment, the control operation unit 4 is provided with a synchronization unit, and is configured to identify and calculate the phase time difference of the induced current signals measured by the plurality of current measurement units, where the calculation mode of the phase time difference adopts the prior art.
In this embodiment, the control arithmetic unit 4 is provided with a communication unit for communicating with an upper computer.
In the aspect of a measuring jaw of the clamp-on current sensor 2, most of the existing clamp meters do not use a shielding layer or only use one shielding layer, the current jaw is very easily influenced by an external electromagnetic field in actual measurement, and particularly when the current jaw is close to a voltage jaw, the coupled interference can seriously distort an induction signal. The clamp-on current sensor 2 of the embodiment of the application adopts the design of multiple shielding layers, so that the co-channel interference in a voltage clamp used as a power source 3 and the electromagnetic interference in the external environment can be effectively isolated or weakened. However, materials with high magnetic permeability are used for obtaining high shielding performance, saturation is easy to occur in a strong magnetic field environment of a power transmission line, materials which are not easy to saturate are selected, the magnetic permeability is low, and the shielding requirement cannot be met. To solve this contradiction, the present embodiment employs a triple magnetic shield layer structure. The first magnetic shielding layer is made of a material with high saturation magnetic flux and low magnetic permeability, and the intensity of the interference magnetic field is attenuated to a lower level; the second magnetic shielding layer is made of a low saturation magnetic flux high magnetic permeability material and plays a main shielding role. The third layer adopts a high-conductivity layer for realizing electric field shielding. The smaller the resistance of the shielding material is, the larger the eddy current generated is, the larger the diamagnetic field is, and the better the shielding effect is. Meanwhile, the good conductor has larger reflection loss to the low-frequency electric field. The shielding layers are respectively connected with different grounds, and air needs to be separated or other insulating media need to be filled between the shielding layers.
In the aspect of measuring circuits, the measuring circuit with wide range and high resolution is designed, the measuring circuit is not saturated and distorted under the background of large power frequency interference current, and relatively weak effective measuring signals can be respectively obtained. The measuring current path inputs the collected induced current signal to the central processing and control unit mainly through the integral amplifying unit, the multi-way switch K, the special active filtering unit and the high-speed analog-to-digital conversion unit. The test equipment carries out final test circuit evaluation according to different field measurement requirements and different impedance calculation methods set by testers. In addition, the test equipment of the embodiment also has a display unit, a communication unit, an input unit and a synchronization function among different modules. The synchronization unit can realize the phase time difference identification calculation among multiple devices, and provides a hardware support for expanding the impedance phase angle calculation of the shunt branch.
The embodiment can perform different combinations of current measurement and current measurement at different positions aiming at different measurement means and modes on the site, the special flexible rogowski coil current sensor 1 can be used for measuring a natural grounding electrode with a larger size, such as a pole tower, and the clamp-shaped current sensor 2 can realize measurement of current loops with different sizes on the site, such as measurement of an artificial grounding electrode, and compared with the traditional grounding resistance test equipment, the embodiment has wider applicability. According to the specific structure of the tower foundation of the on-site tower, an input measurement mode of multiple ports of various current sensors is adopted, and support of on-site measurement and state evaluation can be provided for a multi-port network state circuit model of the grounding device of the transmission tower.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the utility model, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (10)
1. A multi-port transmission tower grounding resistance measuring device is characterized by comprising a control arithmetic unit (4), a power source (3) and a plurality of current measuring units, wherein the power source (3) and the plurality of current measuring units are respectively connected with the control arithmetic unit (4) through signals, each current measuring unit comprises a Rogowski coil current sensor (1) and a pincer-shaped current sensor (2),
the input of the power source (3) is connected with the output of the control arithmetic unit (4) and is used for outputting an excitation voltage signal to the measurement loop;
the outputs of the Rogowski coil current sensor (1) and the pincerlike current sensor (2) are respectively connected with the input of the control arithmetic unit (4) and are used for respectively measuring induced current signals at different positions of a multi-terminal network of the tower grounding;
the control arithmetic unit (4) is used for controlling and outputting the excitation voltage signal and collecting and calculating the measured induced current signal.
2. The multi-port transmission tower grounding resistance measuring equipment according to claim 1, wherein the control operation unit (4) comprises an integral amplification unit, a multi-way switch K, an active filtering unit, an analog-to-digital conversion unit and a central processing and control unit which are connected in sequence, the output of the current measuring unit is connected with the input of the integral amplification unit,
the integral amplification unit is used for carrying out integral amplification on the current signal acquired by the current measurement unit;
the multi-way switch K is used for controlling the on-off of the induced current signal acquisition channel;
the active filtering unit is used for filtering clutter interference on the collected induced current signals;
the analog-to-digital conversion unit is used for performing analog-to-digital conversion on the acquired induced current signals to generate digital signals;
the central processing and control unit is used for calculating and displaying the acquired digital signals.
3. The multi-port transmission tower grounding resistance measuring equipment according to claim 2, wherein the integral amplifying unit comprises an integrating circuit and a current-voltage converting circuit, the output ends of the integrating circuit and the current-voltage converting circuit are connected with the plurality of signal collecting channels of the multi-way switch K in a one-to-one correspondence manner, the input end of the integrating circuit is connected with the output end of the Rogowski coil current sensor (1), and the input end of the current-voltage converting circuit is connected with the output end of the clamp-type current sensor (2); the integrating circuit comprises a resistor R1, a capacitor C1 and an operational amplifier U1, wherein the inverting input end of the operational amplifier U1 is connected with the output end of the Rogowski coil current sensor (1), the non-inverting input end of the operational amplifier U1 is grounded, the output end of the operational amplifier U1 is connected with the multi-way switch K, and the resistor R1 and the capacitor C1 are respectively connected between the inverting input end of the operational amplifier U1 and the output end of the operational amplifier U1 in parallel; the current-voltage conversion circuit comprises a resistor R2 and an operational amplifier U2, the non-inverting input end of the operational amplifier U2 is grounded, the inverting input end of the operational amplifier U2 is connected with the output end of the clamp current sensor (2), the output end of the operational amplifier U2 is connected with the multi-way switch K, and the resistor R2 is connected between the inverting input end of the operational amplifier U1 and the output end of the operational amplifier U2 in parallel.
4. The multi-port transmission tower ground resistance measuring equipment as claimed in claim 2, wherein the active filtering unit comprises a band-stop filter and a low-pass filter which are connected in series, an input end of the band-stop filter is connected with an output end of the multi-way switch K, and an output end of the low-pass filter is connected with an input end of the analog-to-digital conversion unit; the band-stop filter comprises a resistor R3, a resistor R4, a resistor R5, a capacitor C2, a capacitor C3, a capacitor C4 and an operational amplifier U3, wherein one end of the resistor R3 is connected with a multi-way switch K, the other end of the resistor R3 is connected with the non-inverting input end of the operational amplifier U3 after being connected with a resistor R4 in series, the common point of the resistor R3 and the resistor R4 is connected with a capacitor C2 in series and then grounded, one end of the capacitor C3 is connected with the multi-way switch K, the other end of the capacitor C3 is connected with a capacitor C4 in series and then connected with the non-inverting input end of the operational amplifier U3, the common point of the capacitor C3 and the capacitor C4 is connected with the resistor R5 in series and then grounded, and the inverting input end of the operational amplifier U3 is connected with the output end of the operational amplifier U3; the low-pass filter comprises a resistor R6, a resistor R7, a capacitor C5, a capacitor C6 and an operational amplifier U4, one end of the resistor R6 is connected with the output end of the band elimination filter, the other end of the resistor R6 is connected with the non-inverting input end of the operational amplifier U4 after being connected with a resistor R7 in series, the non-inverting input end of the operational amplifier U4 is connected with the capacitor C6 in series and then grounded, the common point of the resistor R6 and the resistor R7 is connected with the inverting input end of the operational amplifier U4 after being connected with a capacitor C5 in series, the inverting input end of the operational amplifier U4 is connected with the output end of the operational amplifier U4, and the output end of the operational amplifier U4 serves as the output end of the active filter unit.
5. The multi-port transmission tower grounding resistance measuring equipment according to claim 1, wherein the power source (3) comprises an excitation voltage generator, a voltage control unit and a power amplification unit which are connected in sequence, the excitation voltage generator, the voltage control unit and the power amplification unit are respectively connected with the output of the control operation unit (4),
the excitation voltage generator is used for generating an excitation voltage signal;
the voltage control unit is used for adjusting the frequency of the excitation voltage signal;
the power amplification unit is used for adjusting the amplitude of the excitation voltage signal and then outputting the excitation voltage signal.
6. The multi-port transmission tower ground resistance measuring device according to claim 5, wherein the voltage control unit comprises a first voltage follower and a second voltage follower which are connected in parallel, input ends of the first voltage follower and the second voltage follower are respectively connected with two output ends of the excitation voltage generator, and output ends of the first voltage follower and the second voltage follower are respectively connected with an input end of the power amplification unit; the first voltage follower comprises an operational amplifier U8, the non-inverting input end of the operational amplifier U8 is connected with the output end of the excitation voltage generator, the inverting input end of the operational amplifier U8 is connected with the output end of the operational amplifier U8, and the output end of the operational amplifier U8 is connected with the input end of the power amplification unit; the second voltage follower comprises an operational amplifier U9, the non-inverting input end of the operational amplifier U9 is connected with the output end of the excitation voltage generator, the inverting input end of the operational amplifier U9 is connected with the output end of the operational amplifier U9, and the output end of the operational amplifier U9 is connected with the input end of the power amplification unit.
7. The multi-port transmission tower ground resistance measuring device as claimed in claim 6, wherein the power amplifying unit comprises a voltage power amplifying circuit and a current source circuit, the voltage power amplifying circuit comprises resistors R8-R10, a transistor Q1, a transistor Q2 and an operational amplifier U5, the non-inverting input terminal of the operational amplifier U5 is connected with the output terminal of the first voltage follower, the non-inverting input terminal of the operational amplifier U5 is connected with the resistor R8 in series and then grounded, the inverting input terminal of the operational amplifier U5 is connected with the output terminal of the second voltage follower in series and then connected with the resistor R9, the output terminal of the operational amplifier U5 is connected with the control terminal of the transistor Q1 and the control terminal of the transistor Q2, the transistor Q1 and the transistor Q2 are connected in series, the input terminal of the transistor Q1 is connected with the positive power source, the output terminal of the transistor Q2 is connected with the negative power source, the common terminal of the transistors Q1 and Q2 is connected with the inverting input terminal of the resistor R9 in series and then connected with the inverting input terminal of the operational amplifier U5, the common end of the triode Q1 and the triode Q2 is used as the output end of the voltage power amplifying circuit; the current source circuit comprises resistors R11-R20, an operational amplifier U6, an operational amplifier U7, a power switch tube Q3 and a power switch tube Q4, wherein a non-inverting input end of the operational amplifier U6 is connected with a resistor R14 in series and a non-inverting input end of an operational amplifier U7 is connected with an output end of a first voltage follower respectively after being connected with a resistor R16 in series, an inverting input end of the operational amplifier U6 is connected with a resistor R15 in series and an inverting input end of an operational amplifier U7 is connected with an output end of a second voltage follower respectively after being connected with a resistor R17 in series, a non-inverting input end of the operational amplifier U6 is connected with a positive power supply after being connected with a resistor R13 in series, a non-inverting input end of an operational amplifier U7 is connected with a negative power supply after being connected with a resistor R18 in series, an output end of the operational amplifier U6 is connected with a control end of a power switch tube Q3, an output end of the operational amplifier U7 is connected with a control end of the power switch tube Q4, the power switch tube Q4 is connected with a positive power switch tube Q4 in series, the input end of the power switch tube Q3 is connected with the inverting input end of the operational amplifier U6 after being connected with the resistor R12 in series, the output end of the power switch tube Q4 is connected with the negative power supply after being connected with the resistor R20 in series, the output end of the power switch tube Q4 is connected with the inverting input end of the operational amplifier U7 after being connected with the resistor R19 in series, and the common end of the power switch tube Q3 and the power switch tube Q4 serves as the output end of the current source circuit.
8. The multi-port transmission tower grounding resistance measuring equipment as claimed in claim 7, wherein the output end of the power source (3) is provided with a voltage coupling output element and a current output port (302), the voltage coupling output element is connected with the output end of a voltage power amplifying circuit, and the current output port (302) is connected with the output end of the current source circuit.
9. The multi-port transmission tower ground resistance measuring device according to claim 8, wherein the voltage coupling-out element is a large-diameter jaw (301).
10. The multi-port transmission tower grounding resistance measuring equipment according to claim 1, wherein the control arithmetic unit (4) is provided with an input unit and a display unit for setting system parameters and displaying test data.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116539963A (en) * | 2023-04-28 | 2023-08-04 | 烟台国网中电电气有限公司 | Method for detecting grounding resistance of grounding down conductor of power transmission line tower |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116539963A (en) * | 2023-04-28 | 2023-08-04 | 烟台国网中电电气有限公司 | Method for detecting grounding resistance of grounding down conductor of power transmission line tower |
| CN116539963B (en) * | 2023-04-28 | 2023-11-21 | 烟台国网中电电气有限公司 | Method for detecting grounding resistance of grounding down conductor of power transmission line tower |
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