CN115166338A - Hydropower station ground grid shunt vector testing method - Google Patents
Hydropower station ground grid shunt vector testing method Download PDFInfo
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Abstract
The invention discloses a hydropower station grounding grid shunt vector testing method which comprises the steps of determining a shunt path of a tested hydropower station grounding grid in the grounding grid impedance testing process according to the environment; respectively carrying out split-flow test preparation based on pilot frequency current injection aiming at each path for generating split flow; synchronously acquiring multichannel shunting data synchronously aiming at each shunting generation way; and carrying out shunting vector calculation based on the multi-channel shunting data synchronous acquisition result to obtain a shunting vector test result. The method aims at the specific type of the hydropower station grounding grid, and determines the shunting way of the tested hydropower station grounding grid in the grounding grid impedance test process according to the environment, so that the method is favorable for comprehensively excavating the shunting way, reduces errors caused by imperfect shunting way consideration, and improves the test precision of shunting vectors.
Description
Technical Field
The invention relates to the field of engineering measurement, in particular to a hydropower station ground grid shunt vector testing method.
Background
With the demand of long-distance, large-capacity and extra-high voltage alternating current transmission in China, the grounding short-circuit current flowing through the grounding grid is larger and larger. In order to ensure the safety of personnel and equipment and maintain the reliable operation of a power system, a transformer substation grounding grid becomes important equipment for ensuring the safety of a power grid. According to the relevant regulations in DL/T475-2017, the guide on the characteristic parameter measurement of grounding devices and GB50150-2006, the standard of the test for handing over electrical equipment in electrical device installation engineering, the characteristic parameter index of the grounding impedance (including shunt test) of large grounding devices must be kept below the design limit. However, the grounding grid used as a hidden project of the transformer substation has the characteristics of one-time construction and high difficulty in later maintenance, and the establishment of the testing method of the shunting vector is very important after the grounding grid is put into operation. The actual current flowing into the ground through the grounding grid is obtained through a shunt test, so that the grounding impedance value is corrected, and the safe operation state is evaluated. The current shunting test technology mainly focuses on shunting caused by overhead ground wires and cable sheaths, and is quite rare in the study of shunting of hydropower stations with special geographic environments, and a large-scale grounding grid shunting model of the hydropower station lacks environmental influence components, so that a real shunting vector of the hydropower station is difficult to obtain.
Disclosure of Invention
The technical problems to be solved by the invention are as follows: aiming at the specific type of the hydropower station grounding grid, the invention determines the shunting way of the tested hydropower station grounding grid in the grounding grid impedance test process according to the environment, is beneficial to comprehensively excavating the shunting way, reduces the error caused by imperfect shunting way consideration and improves the test precision of the shunting vector.
In order to solve the technical problems, the invention adopts the technical scheme that:
a hydropower station ground net diversion vector testing method comprises the following steps:
s101, determining a shunt path of a tested hydropower station grounding grid in the grounding grid impedance test process according to the environment;
s102, respectively carrying out shunt test preparation based on pilot frequency current injection aiming at each path for generating shunt;
s103, synchronously acquiring multichannel shunting data aiming at each shunting generation path;
and S104, performing shunt vector calculation based on the multi-channel shunt data synchronous acquisition result to obtain a shunt vector test result.
Optionally, the step S101 of determining that the shunt is generated in the hydropower station grounding grid in the grounding grid impedance test process includes a shunt I generated by the 1 st to m th overhead outgoing line lightning conductor 11 ～I 1m The shunt I is generated by the 1 st to n cable outer sheaths and other metal conductors connected with the hydropower station grounding grid 21 ～I 2n And diversion I generated by river channel 3i And m is the number of overhead outgoing line lightning conductors, and n is the number of cable outer sheaths and other metal conductors connected with the hydropower station grounding network.
Optionally, the separately performing, in step S102, a split test preparation based on pilot frequency current injection for each split generation path includes:
s201, deploying a power source A1 at a grounding down lead position of main equipment of a grounding network, and respectively installing Rogowski coils for m overhead outgoing line lightning conductors, n cable outer sheaths and other metal conductors connected with a hydropower station grounding network so as to collect and shunt; determining a measured grounding grid edge point A and a hydropower station current pole B along a river channel, and deploying a power source A2 and a frequency modulation universal meter V2 between the measured grounding grid edge point A and the hydropower station current pole B to monitor the voltage between the measured grounding grid edge point A and the hydropower station current pole B;
and S202, respectively connecting the Rogowski coil and the frequency modulation multimeter V2 into the multi-channel shunt vector measuring device.
Optionally, the distance between the measured grounding grid edge point A and the hydropower station current pole B is 4-5 times of the maximum diagonal length of the tested hydropower station grounding grid.
Optionally, step S103 includes:
s301, monitoring the voltage between the edge point A of the grounding grid to be detected and the current pole B of the hydropower station by using a frequency modulation universal meter V2;
s302, injecting a pilot frequency current with a frequency different from that of the power frequency current between the edge point A of the grounding network to be detected and the current pole B of the hydropower station through the power source A2, and determining a resistor R between the edge point A of the grounding network to be detected and the current pole B of the hydropower station AB ；
S303, carrying out satellite time service synchronization on the multi-channel shunt vector measuring device, the power source A1 and the power source A2;
s304, outputting pilot frequency currents with different frequencies from the power frequency current through the power source A1 and the power source A2 respectively, testing pilot frequency current signals output by the power source A1 and the power source A2 and recording zero-crossing time; aiming at a power source A1 and a power source A2, respectively judging whether the output pilot frequency current signal and the GPS second pulse edge of satellite time service are synchronous, if not, adjusting the output frequency until the pilot frequency current signal and the GPS second pulse edge of satellite time service are synchronous;
s305, periodically outputting different-frequency current with different frequency from the power frequency current through a power source A1, and injecting different-frequency current with different frequency from the power frequency current between a detected grounding grid edge point A and a hydropower station current pole B through a power source A2;
s306, synchronously acquiring shunt data of each shunt generation way at the time when the GPS second pulse of the multi-channel shunt vector measuring device during satellite time service is 0 degrees along the corresponding phase, and obtaining a shunt I generated by 1-m overhead outgoing line lightning conductors 11 ～I 1m The shunt I is generated by the 1 st to n cable outer sheaths and other metal conductors connected with the hydropower station grounding grid 21 ～I 2n And the voltage vector between the edge point A of the grounding network to be detected and the current pole B of the hydropower station according to the voltage vector between the edge point A of the grounding network to be detected and the current pole B of the hydropower station and the resistor R AB Deducing a diversion vector I generated by the river channel 3i 。
Alternatively, in step S305, the frequencies of the pilot frequency currents output by the power sources A1 and A2 are different from each other.
Optionally, in step S305, one of the frequencies of the pilot frequency currents output by the power source A1 and the power source A2 is 45Hz, and the other frequency is 55Hz.
Optionally, step S104 includes: according to the voltage vector between the edge point A of the grounding network to be detected and the current pole B of the hydropower station and the resistance R between the edge point A of the grounding network to be detected and the current pole B of the hydropower station AB Deducing a diversion vector I generated by the river channel 3i And respectively obtaining the amplitude and the initial phase of the shunt vector through Discrete Fourier Transform (DFT) operation, and further calculating the sum of the shunt vector.
Optionally, in step S302, a resistance R between the edge point a of the ground grid to be measured and the current pole B of the hydropower station is determined AB Firstly, representing a river channel by adopting an ellipsoid curved surface coordinate system to determine a shape parameter theta of an ellipsoid curved surface; then, on the basis of determining the shape parameter theta, solving and calculating the resistance R between the edge point A of the detected grounding grid and the current pole B of the hydropower station by adopting a numerical integration mode according to the following formula AB ：
In the above formula, ρ 1 Is the earth resistivity of the land, p 0 Is the river water resistivity.
Optionally, the functional expression represented by the ellipsoid curved surface coordinate system is:
in the above formula, (x, y, z) is a point coordinate on the ellipsoid curved surface, a is the channel length, b is the channel width, c is the channel depth, and θ is a shape parameter of the ellipsoid curved surface.
Compared with the prior art, the invention mainly has the following advantages
1. The method comprises the steps of determining a way for shunting the grounding grid of the tested hydropower station in the grounding grid impedance test process according to the environment; respectively carrying out split-flow test preparation based on pilot frequency current injection aiming at each path for generating split flow; synchronously acquiring multichannel shunting data synchronously aiming at each shunting generation way; the method and the device have the advantages that the shunting path generated by the tested hydropower station grounding network in the grounding network impedance test process is determined according to the environment aiming at the specific type grounding network of the hydropower station grounding network, so that the shunting path can be comprehensively excavated, errors caused by imperfect shunting path consideration can be reduced, and the testing precision of the shunting vector can be improved.
2. The multi-channel shunt vector testing device dynamically monitors the data acquired by the Rogowski coil, extracts the amplitude and the phase of each shunt signal in parallel, shortens the time of comparing the shunt signal with the data of a source end test signal, and improves the shunt vector testing efficiency.
Drawings
FIG. 1 is a schematic diagram of a basic flow of a method according to an embodiment of the present invention.
FIG. 2 is a schematic diagram of a determined approach to generating a split stream in an embodiment of the present invention.
Fig. 3 is a schematic structural diagram of a pilot current injection-based shunt test system according to an embodiment of the present invention.
Fig. 4 is a schematic diagram of a multi-channel data synchronous acquisition process of source table GPS signal synchronization in the embodiment of the present invention.
Fig. 5 is a schematic flow chart of the shunt vector calculation based on the remote synchronous measurement in the embodiment of the present invention.
FIG. 6 shows a resistance R measured according to an embodiment of the present invention AB Schematic diagram of the principle of (1).
Detailed Description
As shown in fig. 1, the method for testing the diversion vector of the earth network of the hydropower station in the embodiment includes:
s101, determining a way for shunting the grounding network of the tested hydropower station in the grounding network impedance test process according to the environment;
s102, respectively carrying out shunt test preparation based on pilot frequency current injection aiming at each shunt generation path;
s103, synchronously acquiring multi-channel shunting data aiming at each shunting generation way;
and S104, performing shunt vector calculation based on the multi-channel shunt data synchronous acquisition result to obtain a shunt vector test result.
The model connected with the large-scale ground net is drawn through specific survey of the surrounding environment of the large-scale ground net, so that a way for generating shunt in the process of testing the impedance of the ground net is comprehensively excavated, and the later stage design of a specific implementation scheme of shunt testing is facilitated. The states of the grounding grid of the transformer substation are roughly divided into the following three types: 1) If the grounding grid is independent, namely the grounding grid is not electrically connected with other metallic grounding bodies, all test current can flow into the ground through the grounding grid to be tested, and the measurement result reflects the real grounding resistance of the grounding grid. 2) If the grounding grid to be tested is electrically connected with other metal grounding bodies, part of the test current flows out through the other metal grounding bodies, namely the other grounding bodies shunt the test current, and the test current flowing through the grounding bodies is reduced, so that the grounding resistance measurement result is smaller. 3) If the transformer substation grounding grid is expanded, the grounding grid comprises a main grounding grid and an expansion grid, so that the other metal grounding bodies can generate shunting, and contribution can be made to shunting under the condition that the special geographic environment is conductive. Shunting the test current will directly affect the measurement result of the ground impedance.
The hydropower station grounding grid consists of a dam body grounding grid, a booster station grounding grid and other scattered grounding grids, and the diversity of shunting influence factors is determined by the composition of the grounding grids and the complexity of the geographic environment. Therefore, before the shunt test of the hydropower station grounding grid, a grounding grid shunt model needs to be established, and a shunt path needs to be comprehensively excavated, as shown in fig. 2. Referring to fig. 2, in step S101 of this embodiment, the way of determining that the shunt is generated in the ground grid impedance test process of the hydropower station grounding grid includes a shunt I generated by the 1 st to m th overhead outgoing line lightning conductors 11 ～I 1m The branch generated by the 1 st to n cable outer sheaths and other metal conductors connected with the hydropower station grounding gridStream I 21 ～I 2n And diversion I generated by river channel 3i And m is the number of overhead outgoing line lightning conductors, and n is the number of cable outer sheaths and other metal conductors connected with the hydropower station grounding network. As can be seen from the shunting model shown in FIG. 2, the overhead outgoing line lightning conductor connected with the grounding grid, the cable sheath connected with the grounding grid and other metal conductors are limited by geographical conditions when the hydropower station ground grid is tested, the current line is generally arranged along a small path beside a river channel, the current pole can be driven to the roadside and is very close to the river, the special geographical environment and the arrangement mode of the current pole of the hydropower station can shunt the test current, and the comprehensive excavation of the shunting path is beneficial to improving the accuracy of the shunting vector calculation. The vector set of the shunt generated by the overhead outgoing line lightning conductor is I 1 ＝{I 11 ,I 12 ,...,I 1m H, the shunt vectors generated by the cable outer sheath and other metal conductors are set to be I 2 ＝{I 21 ,I 22 ,...,I 2n The diversion generated by special geographical environments such as river channels is I 3 ＝{I 31 ,I 32 ,...,I 3i Obtaining a set of shunting vectors I = { I) through modeling 1 ,I 2 ,I 3 }. Wherein m represents the number of overhead outgoing line lightning conductors; n represents the number of metal conductors such as the cable outer sheath; i represents the number of channels.
The shunt measurement implementation method based on pilot frequency signal injection comprises the steps of configuring a required power source, a shunt vector testing device, a frequency modulation multimeter, a connecting cable and the like according to a specific test shunt scene, and establishing a shunt measurement specific implementation method. Wherein the power source outputs a constant current source test signal synchronous with the pulse per second edge; the split-flow vector testing device acquires the amplitude and the phase of each split-flow vector based on the GPS second pulse edge signal; the frequency measurement range of the frequency modulation multimeter is 40 Hz-60 Hz, the stepping amplitude is 1Hz, and the frequency modulation multimeter is used for measuring voltage values of different frequencies between two points of a river channel. The step S102 of separately performing pilot frequency current injection-based shunt test preparation for each shunt generation path includes:
s201, deploying a power source A1 at a grounding down lead position of main equipment of a grounding network, and respectively installing Rogowski coils for m overhead outgoing line lightning conductors, n cable outer sheaths and other metal conductors connected with a hydropower station grounding network so as to collect and shunt; determining a measured grounding grid edge point A and a hydropower station current pole B along a river channel, and deploying a power source A2 and a frequency modulation universal meter V2 between the measured grounding grid edge point A and the hydropower station current pole B to monitor the voltage between the measured grounding grid edge point A and the hydropower station current pole B;
and S202, respectively connecting the Rogowski coil and the frequency modulation multimeter V2 to the multi-channel shunt vector measuring device.
In this embodiment, step S103 includes:
s301, monitoring the voltage between the edge point A of the grounding grid to be detected and the current pole B of the hydropower station by using a frequency modulation universal meter V2;
s302, injecting different-frequency current with different frequency from the power frequency current between the edge point A of the detected grounding grid and the current pole B of the hydropower station through the power source A2, and determining the resistance R between the edge point A of the detected grounding grid and the current pole B of the hydropower station AB ；
S303, carrying out satellite time service synchronization on the multi-channel shunt vector measuring device, the power source A1 and the power source A2;
s304, outputting pilot frequency currents with different frequencies from the power frequency current through the power source A1 and the power source A2 respectively, testing pilot frequency current signals output by the power source A1 and the power source A2 and recording zero-crossing time; aiming at a power source A1 and a power source A2, respectively judging whether the output pilot frequency current signal and the GPS second pulse edge of satellite time service are synchronous, if not, adjusting the output frequency until the pilot frequency current signal and the GPS second pulse edge of satellite time service are synchronous;
s305, periodically outputting different-frequency current with different frequency from the power frequency current through a power source A1, and injecting different-frequency current with different frequency from the power frequency current between a detected grounding grid edge point A and a hydropower station current pole B through a power source A2;
s306, synchronously acquiring shunt data of each shunt generation way by the multi-channel shunt vector measuring device at the time when the corresponding phase of the GPS second pulse of satellite time service is 0 degree, and obtaining a shunt I generated by the 1 st to m th overhead outgoing line lightning conductors 11 ～I 1m The shunt I is generated by the 1 st to n cable outer sheaths and other metal conductors connected with the hydropower station grounding grid 21 ～I 2n And the voltage vector between the edge point A of the grounding network to be detected and the current pole B of the hydropower station according to the voltage vector between the edge point A of the grounding network to be detected and the current pole B of the hydropower station and the resistor R AB Deducing a diversion vector I generated by a river channel 3i 。
The pilot frequency current injection method is a power frequency-like small current measurement technology recommended by a power guide rule, can strip a tested pilot frequency current from a field interference current signal, and avoids adverse effects of the interference signal on a final shunt vector because the interference signal does not participate in a ground grid shunt vector test. Therefore, the frequencies of the pilot frequency currents output by the power sources A1 and A2 in step S305 are different from each other.
As an optional implementation manner, in the step S305 of this embodiment, one of the frequencies of the pilot frequency currents output by the power source A1 and the power source A2 is 45Hz, and the other frequency is 55Hz. Research has shown that the conductivity of water and soil below 1kHz and the resistivity of soil are constants that do not change with frequency, so R AB-55Hz ＝R AB-45Hz Namely, the equivalent water resistance R can be obtained by measuring with 55Hz AB Then, the same value is used for calculating the shunt vector corresponding to the water resistance in the 45Hz shunt measurement. In the test, two different frequencies of 45Hz and 55Hz which are different from the power frequency of 50Hz are selected as the current output frequency of the power source, the size of a different frequency injection small current test signal is controlled within the range of 3-20A, the output signal is stable, the test time of the large-load operation on site is longer, the safety of testers can be ensured, the site wiring and taking up are simple, and the reliability of the test result is high. In this embodiment, when multi-channel data synchronous acquisition based on source meter GPS signal synchronization is performed, a non-master-slave mode based on GPS source meter synchronization is adopted, and source meter GPS synchronous time service is adopted, the split-flow vector testing apparatus includes a master control unit, an acquisition unit, and a data processing unit, wherein the master control unit manages and controls all the test meters, an output end of a GPS second pulse signal is connected to a test meter control unit to provide a second pulse signal, each channel of the acquisition unit of the test meter is controlled based on the GPS second pulse signal, and channels of the acquisition unit perform measurementAnd shunting vectors of each sampling point in different places.
In the embodiment, the distance between the edge point A of the tested grounding grid and the current pole B of the hydropower station is 4-5 times of the maximum diagonal length of the grounding grid of the tested hydropower station, a specific implementation method of the shunt vector test of the large grounding grid is established based on the selected pilot frequency signal and the established shunt model, as shown in figure 3, a power source signal access point and a sampling point of a test instrument are designed according to the shunt model, tool preparation and personnel arrangement are well made, and a foundation is laid for smooth implementation of data acquisition work of each shunt path.
Referring to fig. 3, the steps of establishing a test implementation of the shunt vector of the large-scale ground grid include: sampling point equipment deployment: deploying a power source A1 at the position of a grounding down lead (such as a transformer grounding down lead) of main equipment of a grounding network, and installing a test instrument and a Rogowski coil on an overhead outgoing line lightning conductor, a cable outer sleeve or other metal conductors; and (3) wiring along the side highway of the river channel, and deploying a frequency modulation universal meter V2 for monitoring voltage and power source A2 injection current between two points AB of the river channel by using a four-terminal wiring method. Test signal injection selection: because the resistance of the river channel is unknown, the power source A2 is required to inject a 55Hz pilot frequency current signal I from the point A or the point B of the river channel 55 Calculating the equivalent resistance between two points AB of the river; the power source A1 injects 45Hz pilot frequency current I through the grounding down lead of the grounding network main equipment 45 Obtaining the distribution current I = { I) in the grounding grid model 1 ,I 2 ,I 3 }.2 the pilot frequency signal of way can effectively avoid the influence of power frequency interference. Data acquisition communication inspection: the wireless communication of the test instrument connected with the Rogowski coil at each sampling point is checked by utilizing the self-checking function of the multi-channel shunt vector testing device, the fact that the Rogowski coil collects data can be normally transmitted back to the shunt vector testing device is determined, and the fact that communication connection of each channel in the device is normal and stable is guaranteed. On the basis of the establishment of the shunt approach comprehensive mining and shunt test implementation method, the ground grid shunt vector test needs to synchronously trigger power source signal output and Rogowski coil shunt sampling, and multichannel data synchronous acquisition based on source meter GPS signal synchronization is shown in FIG. 4. The GPS signal synchronization technology of the global positioning system is utilized to realize the GPS time service signal synchronization of the source meter, and each GPS module can be used for every secondOutputting a PPS second pulse signal, receiving a GPS signal transmitted by a satellite, synchronizing all measurements once every 10 second pulses, and starting the acquisition of each shunt vector at the same moment if the received second pulse rising edge with a time label of the GPS is taken as a trigger signal for the acquisition and conversion of each shunt vector signal.
In this embodiment, step S104 includes: according to the voltage vector between the edge point A of the grounding network to be detected and the current pole B of the hydropower station and the resistance R between the edge point A of the grounding network to be detected and the current pole B of the hydropower station AB Deducing a diversion vector I generated by the river channel 3i And respectively obtaining the amplitude and the initial phase of the shunt vector through Discrete Fourier Transform (DFT) operation, and further calculating the sum of the shunt vector. In this embodiment, when a shunt vector is calculated based on remote synchronous measurement, the data processing unit of the shunt vector testing apparatus performs parallel processing on the acquired shunt vector data, triggers sampling of a pilot frequency shunt signal to load based on a GPS second pulse edge signal according to information such as configured sampling point numbers, sampling intervals, and sampling durations of each channel, obtains an amplitude and an initial phase of the shunt vector through Discrete Fourier Transform (DFT) operation, and further calculates a sum of the shunt vector.
Because the GPS module provides synchronous signals for the control trigger of the total test current and the sampling trigger of each shunt vector, the zero crossing point of the test signal of the power source is synchronous with the second pulse edge of the GPS, the phase of the test signal at the moment corresponding to the second pulse edge is 0 degree, and the phase difference of each different frequency shunt signal acquired by the multi-channel shunt vector testing device relative to the second pulse edge is the phase of each shunt vector. As shown in fig. 5, the step of calculating the shunt vector based on the displaced synchronization measurement in this embodiment is as follows: 1) Loading path information of a multi-channel configuration file (cfg) in a shunt flow measurement testing device; 2) Acquiring analog quantity channel information in the configuration file according to the path of the acquired cfg configuration file; 3) Calculating the number of rows of channel information according to the obtained channel information of the cfg configuration file; 4) According to the data file format transmitted by each channel, directly extracting the related quantity and storing the related quantity into corresponding variable names, such as channel information, trigger time, sampling interval, sampling duration, data file name and the like; 5) Reading sampling data in a csv data file with an extension name; 6) Triggering sampling pilot frequency shunt signal loading based on GPS second pulse edge signals, and obtaining the amplitude and initial phase of each channel shunt signal through DFT operation; 7) The split vector sum is calculated.
Because of the particularity of the geographical environment of the hydropower station, the water in the river channel has the conductive characteristic, the river channel resistance is necessarily related to the depth and the length of the river water, in order to measure the river channel resistance as accurately as possible, the water needs to be wired along roads at two sides of the river channel and covers the distance between a point A (the point A is not connected to the ground net) at the edge of a grounding grid of the current raising station and a point B of a current electrode, the 55Hz different-frequency current injected by a power source A2 is effectively prevented from being shunted by the ground net, the AB two electrodes are placed into the river channel and the river water, and the constant 55Hz current I is applied by the power source A2 55 And measuring the resistivity of the river water of the river channel. In this embodiment, in step S302, the resistance R between the edge point a of the ground grid to be measured and the current pole B of the hydropower station is determined AB Firstly, representing the river channel by an ellipsoid curved surface coordinate system to determine a shape parameter theta of an ellipsoid curved surface; then, on the basis of determining the shape parameter theta, solving and calculating the resistance R between the edge point A of the detected grounding grid and the current pole B of the hydropower station by adopting a numerical integration mode according to the following formula AB ：
In the above formula, ρ 1 Is the earth resistivity of the land, p 0 Is the river water resistivity.
In this embodiment, the functional expression expressed by the ellipsoid curved surface coordinate system is:
in the above formula, (x, y, z) is a point coordinate on the ellipsoid curved surface, a is the channel length, b is the channel width, c is the channel depth, and θ is a shape parameter of the ellipsoid curved surface. A resistance R between the edge point A of the detected grounding grid and the current pole B of the hydropower station AB The derivation process of equation (1) is as follows:
s401, an ellipsoid curved surface coordinate system is established to express, as shown in formula (2):
s402, making the intermediate variable:
implementing Hamiltonian on the shape parameter theta of the ellipsoid curved surface
And (3) operation:
in the above formula, M 2 Is M n With n = 2.
Due to formula (7):
independent of xyz, the ellipsoid of the surface of formula (2) can represent an equipotential surface, so the potential V associated with θ can be written as:
in the above formula, A and B are the positions of the edge point A of the grounding grid to be detected and the current pole B of the hydropower station respectively.
S403, at infinity the potential is 0, i.e.:
b =0 is available. Thus, there are:
s404, let theta =0, the potential V is set to be V 0 Therefore, the following are:
s405, in which formula (10) is substituted with B =0 and formula (11):
s406, let the charge amount of the ellipsoid be Q, and the electric field strength at infinity be:
when θ → ∞ is satisfied, x 2 +y 2 +z 2 ＝r 2 ＝θ，
The substitution formula (13) is:
s407, comparing equation (13) with equation (14) includes:
Q＝-8πεA， (15)
therefore, the ellipsoidal ground resistance is:
where ρ is the resistivity of the medium.
And S408, considering half of ellipsoids and doubling the grounding resistance for the actual river channel. Let the channel length a ', width b ', depth c ', rho 0 Is the river water resistivity, p 1 Is the earth's earth resistivity, p 0 And ρ 1 Can be obtained in the field by using a conventional measuring method. By using the formula (16), the resistance R between the edge point A of the grounding grid to be measured and the current pole B of the hydropower station can be obtained AB The formula (1). In the formula (1), the first term on the right side is a ground resistance correction term considering the earth resistivity, and represents the ground resistance that the river is approximately equivalent to an ellipsoid, and the second term on the right side is a ground resistance term considering the river resistivity, and represents the ground resistance that the river center is equivalent to a long conductor ellipsoid with the radius of 1 cm. The river channel resistance calculation formula is in an infinite integral form, and can be solved by using a numerical integration method. It should be noted that the numerical integration method solves the problem as the conventional solution method, and therefore, the detailed implementation process thereof is not described in detail herein.
In summary, the hydropower station ground grid shunt vector testing method of the embodiment is based on a hydropower station large-scale ground grid shunt model, and is used for comprehensively excavating a shunt path; based on a pilot frequency current injection mode, effectively separating a test signal from field power frequency interference influence, and establishing a specific shunt measurement implementation method; a source meter GPS signal synchronization technology is adopted to synchronously control the signal emission of a power source and the data acquisition of scattered sampling points; amplitude values and initial phase measurement values on all the shunt branches are obtained through remote synchronous measurement, and measurement of shunt vectors of the large-scale ground nets of the hydropower stations is finally achieved. The hydropower station ground grid shunt vector testing method is based on a shunt model of large-scale ground grid grounding impedance, is beneficial to comprehensively excavating a shunt path, adding geographic environment factor components, reducing errors caused by imperfect shunt path consideration and improving the testing precision of shunt vectors; according to the hydropower station land grid shunt vector testing method, injected 55Hz pilot frequency current and the voltage between two points AB of a river channel monitored by a frequency-selective multimeter are utilized to calculate the equivalent resistance between the two points AB of the river channel, and then the voltage of a 45Hz pilot frequency current signal on the equivalent resistance of the river channel is detected, so that a 45Hz shunt vector in the river channel is calculated, and a new method is established for the hydropower station river channel shunt vector test with the second generated energy; the hydropower station earth screen shunt vector testing method is based on source meter GPS signal synchronization, phase information of testing signals does not need to be transmitted to each testing meter to serve as reference, the delay problem caused by data transmission between source meters is solved, the multichannel shunt vector testing device dynamically monitors data collected by the Rogowski coil, the amplitude and the phase of each shunt signal are extracted in parallel, the time for comparing the shunt signals with the source end testing signal data is shortened, and the shunt vector testing efficiency is improved.
The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments, and all technical solutions belonging to the idea of the present invention belong to the protection scope of the present invention. It should be noted that modifications and adaptations to those skilled in the art without departing from the principles of the present invention should also be considered as within the scope of the present invention.
Claims (10)
1. A hydropower station ground grid shunt vector testing method is characterized by comprising the following steps:
s101, determining a shunt path of a tested hydropower station grounding grid in the grounding grid impedance test process according to the environment;
s102, respectively carrying out shunt test preparation based on pilot frequency current injection aiming at each shunt generation path;
s103, synchronously acquiring multi-channel shunting data aiming at each shunting generation way;
and S104, carrying out shunting vector calculation based on the multi-channel shunting data synchronous acquisition result to obtain a shunting vector test result.
2. The method for testing the shunt vector of the hydropower station ground grid according to claim 1, wherein the step S101 of determining the way of the shunt generated in the hydropower station ground grid in the process of testing the ground grid impedance comprises the step of leading out the 1 st to m th aerial conductorsShunt current I generated by line lightning conductor 11 ～I 1m The shunt I is generated by the 1 st to n cable outer sheaths and other metal conductors connected with the hydropower station grounding grid 21 ～I 2n And diversion I generated by river channel 3i And m is the number of overhead outgoing line lightning conductors, and n is the number of cable outer sheaths and other metal conductors connected with the hydropower station grounding network.
3. The hydropower station earth grid shunt vector test method according to claim 1, wherein the step S102 of preparing a shunt test based on pilot frequency current injection for each shunt generation path respectively comprises:
s201, deploying a power source A1 at a grounding down lead position of main equipment of a grounding network, and respectively installing Rogowski coils for m overhead outgoing line lightning conductors, n cable outer sheaths and other metal conductors connected with a hydropower station grounding network so as to collect and shunt; determining an edge point A of a detected grounding grid and a current pole B of a hydropower station along a river channel, and deploying a power source A2 and a frequency modulation universal meter V2 between the edge point A of the detected grounding grid and the current pole B of the hydropower station to monitor the voltage between the edge point A of the detected grounding grid and the current pole B of the hydropower station;
and S202, respectively connecting the Rogowski coil and the frequency modulation multimeter V2 to the multi-channel shunt vector measuring device.
4. The hydropower station ground net shunt vector testing method according to claim 3, wherein the distance between the edge point A of the tested ground net and the current pole B of the hydropower station is 4-5 times the maximum diagonal length of the tested hydropower station ground net.
5. The hydropower station earth grid diversion vector testing method of claim 4, wherein the step S103 comprises:
s301, monitoring the voltage between the edge point A of the grounding grid to be detected and the current pole B of the hydropower station by using a frequency modulation universal meter V2;
s302, injecting different frequencies with different frequencies from the frequency of the power frequency current between the edge point A of the grounding grid to be detected and the current pole B of the hydropower station through the power source A2Determining the resistance R between the edge point A of the grounding network to be tested and the current pole B of the hydropower station AB ；
S303, carrying out satellite time service synchronization on the multi-channel shunt vector measuring device, the power source A1 and the power source A2;
s304, outputting pilot frequency currents with different frequencies from the power frequency current through the power source A1 and the power source A2 respectively, testing pilot frequency current signals output by the power source A1 and the power source A2 and recording zero-crossing time; aiming at a power source A1 and a power source A2, respectively judging whether the output pilot frequency current signal and the GPS second pulse edge of satellite time service are synchronous, if not, adjusting the output frequency until the pilot frequency current signal and the GPS second pulse edge of satellite time service are synchronous;
s305, periodically outputting different-frequency current with different frequency from the power frequency current through a power source A1, and injecting different-frequency current with different frequency from the power frequency current between a detected grounding grid edge point A and a hydropower station current pole B through a power source A2;
s306, synchronously acquiring shunt data of each shunt generation way by the multi-channel shunt vector measuring device at the time when the corresponding phase of the GPS second pulse of satellite time service is 0 degree, and obtaining a shunt I generated by the 1 st to m th overhead outgoing line lightning conductors 11 ～I 1m The shunt I is generated by the 1 st to n cable outer sheaths and other metal conductors connected with the hydropower station grounding grid 21 ～I 2n And the voltage vector between the edge point A of the grounding network to be detected and the current pole B of the hydropower station according to the voltage vector between the edge point A of the grounding network to be detected and the current pole B of the hydropower station and the resistor R AB Deducing a diversion vector I generated by the river channel 3i 。
6. The hydropower station earth network shunt vector testing method of claim 5, wherein in the step S305, the frequencies of the pilot frequency currents output by the power source A1 and the power source A2 are different from each other.
7. The hydropower station earth grid shunt vector testing method of claim 6, wherein in the step S305, one of the frequencies of the pilot frequency currents output by the power source A1 and the power source A2 is 45Hz, and the other frequency is 55Hz.
8. The hydropower station earth grid diversion vector testing method of claim 5, wherein the step S104 comprises: according to the voltage vector between the edge point A of the detected grounding network and the current pole B of the hydropower station and the resistance R between the edge point A of the detected grounding network and the current pole B of the hydropower station AB Deducing a diversion vector I generated by the river channel 3i And respectively obtaining the amplitude and the initial phase of the shunt vector through Discrete Fourier Transform (DFT) operation, and further calculating the sum of the shunt vector.
9. The method for testing the shunt vector of the ground grid of the hydropower station according to claim 5, wherein the resistance R between the edge point A of the tested ground grid and the current pole B of the hydropower station is determined in step S302 AB Firstly, representing a river channel by adopting an ellipsoid curved surface coordinate system to determine a shape parameter theta of an ellipsoid curved surface; then, on the basis of determining the shape parameter theta, solving and calculating the resistance R between the edge point A of the grounding network to be measured and the current pole B of the hydropower station by adopting a numerical integration mode according to the following formula AB ：
In the above formula, ρ 1 Is the earth resistivity of the land, p 0 Is the river water resistivity.
10. The hydropower station earth network shunt vector testing method of claim 9, wherein the functional expression expressed by the ellipsoid curved surface coordinate system is as follows:
in the above formula, (x, y, z) is a point coordinate on the ellipsoid curved surface, a is the channel length, b is the channel width, c is the channel depth, and θ is a shape parameter of the ellipsoid curved surface.
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