CN109188088B - A kind of vertical demixing electric resistance of soil nonlinear characteristic test method - Google Patents
A kind of vertical demixing electric resistance of soil nonlinear characteristic test method Download PDFInfo
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- 239000002689 soil Substances 0.000 title claims abstract description 145
- 238000010998 test method Methods 0.000 title claims abstract description 6
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims abstract description 43
- 229910052802 copper Inorganic materials 0.000 claims abstract description 43
- 239000010949 copper Substances 0.000 claims abstract description 43
- 238000012360 testing method Methods 0.000 claims abstract description 32
- 238000011156 evaluation Methods 0.000 claims abstract description 10
- 238000005259 measurement Methods 0.000 claims abstract description 5
- 238000005192 partition Methods 0.000 claims description 18
- 238000011084 recovery Methods 0.000 claims description 12
- 238000004364 calculation method Methods 0.000 claims description 8
- 239000002131 composite material Substances 0.000 claims description 6
- 230000007246 mechanism Effects 0.000 claims description 6
- 238000013517 stratification Methods 0.000 claims description 5
- 238000009413 insulation Methods 0.000 claims description 4
- 238000004891 communication Methods 0.000 claims description 3
- 238000001816 cooling Methods 0.000 claims description 3
- 238000012544 monitoring process Methods 0.000 claims description 3
- 230000000630 rising effect Effects 0.000 claims description 3
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- 230000005684 electric field Effects 0.000 description 2
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- 238000011160 research Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
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- 239000004020 conductor Substances 0.000 description 1
- 230000007123 defense Effects 0.000 description 1
- 230000032798 delamination Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
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- 238000002474 experimental method Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000010248 power generation Methods 0.000 description 1
- 230000035939 shock Effects 0.000 description 1
- 238000004088 simulation Methods 0.000 description 1
- 230000001052 transient effect Effects 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
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Abstract
A kind of vertical demixing electric resistance of soil nonlinear characteristic test method, the soil chamber interior wall of test platform are provided with temperature control device, and left and right side walls are provided with left copper electrode and right copper electrode；Impulse current generator output end is connected to the high-voltage end of divider, and the high-voltage end of divider is connected to left copper electrode；Right copper electrode is connected to the ground terminal of impulse current generator, and ground terminal is connected to earthing or grounding means；Current acquisition module is for measuring the electric current for flowing through left copper electrode and right copper electrode；Further include insulating barrier, when insulating barrier is inserted into soil case, soil case is divided into more than two spaces from bottom to up.Test method includes soil filling and set temperature, voltage and electric current of the measurement pedotheque in Current Temperatures and assesses electric resistance of soil nonlinear characteristic.The present invention can effective analogue ground system surrounding soil vertical demixing operating condition, and accurate evaluation is carried out to vertical demixing electric resistance of soil nonlinear characteristic.
Description
Technical Field
The invention belongs to the field of grounding analysis of power systems, and particularly relates to a vertical stratification soil resistance nonlinear characteristic test method.
Background
When the power transmission line tower is struck by lightning, a very high potential can be generated on the tower body due to the existence of the tower grounding resistance, and the over-high potential can cause the tower to impact the power transmission line, so that the power transmission line is short-circuited, and the stability and the reliability of a power system are reduced. The main function of the grounding device of the transmission line tower is to effectively discharge lightning current into the ground when the tower top or the lightning conductor is struck by lightning, so that the current flowing through the grounding device is mainly lightning impulse current. The lightning current amplitude is large, so that local breakdown of soil around the grounding body is easy to occur, the conductivity of the soil is increased, the resistivity of the soil is reduced, and in addition, when the electric field intensity generated by the scattered current in the soil exceeds the critical breakdown field intensity of the soil, a spark discharge process similar to air breakdown can occur in the soil around the grounding body. The potential of each point on the grounding body and the potential difference between each point of the grounding body can be obviously reduced by the soil spark discharge, and the grounding device has obvious effects on reducing the tower top potential of a transmission line tower and the transient potential rise on a grounding grid of a power generation substation and a transformer substation. Therefore, the research on the lightning impulse characteristics of the grounding device of the power transmission and distribution tower has important significance for establishing an advanced and reliable power transmission and distribution network and a power supply system in an intelligent power grid and perfecting a power grid safety guarantee and defense system.
Because the grounding electrode of the power transmission line tower is buried in the soil, the impact characteristic of the grounding electrode is closely related to the impact characteristic of the soil around the grounding body. At present, the domestic research on the nonlinear characteristics of soil resistance mainly simulates the nonlinear characteristic process of soil resistance and the spark discharge phenomenon through computer simulation, and the nonlinear characteristics of soil resistance under the impact current are influenced by many factors, such as: the impact characteristics of the soil under the action of high-frequency large impact current become more complicated due to the impact current amplitude, the soil composition and structure, the soil density, the water content, the temperature, the external electric field intensity and the like, so that the nonlinear characteristics of the soil resistance are difficult to accurately simulate during simulation. Therefore, in order to accurately analyze the nonlinear characteristic of the soil resistance, an intelligent measurement and control device is urgently needed to be established, the influence of vertical layering of the temperature and the soil can be considered, and the intelligent measurement and control device has the test and analysis of the nonlinear characteristic of the vertical layering of the soil resistance under different temperatures and is used for safety assessment of a power transmission and distribution system.
Disclosure of Invention
The invention aims to provide a method for testing the nonlinear characteristic of the resistance of vertically layered soil.
The technical scheme for realizing the purpose of the invention comprises the following steps:
the first step is as follows: constructing a vertical layered soil resistance nonlinear characteristic test platform, which comprises a soil box; the inner wall of the soil box is provided with a temperature control device; the left side wall of the soil box is provided with a left copper electrode and a control mechanism for controlling the left copper electrode to move transversely; the right side wall of the soil box is also provided with a right copper electrode; the left copper electrode and the right copper electrode are both vertical circles; the left upper part, the right upper part, the left lower part and the right lower part of the soil box are respectively provided with a first temperature sensor, a second temperature sensor, a third temperature sensor and a fourth temperature sensor, and further comprise a shock current generator and a voltage divider;
wherein: the first temperature sensor, the second temperature sensor, the third temperature sensor and the fourth temperature sensor are respectively connected to the input end of a temperature analyzer, and the output end of the temperature analyzer is respectively connected to the digital controller and the upper computer; the digital controller is connected to the temperature control device;
the output end of the impulse current generator is connected to the high-voltage end of the voltage divider, and the high-voltage end of the voltage divider is connected to the left copper electrode through a high-voltage cable and a cable joint; the right copper electrode is connected to the grounding end of the impulse current generator through a lead, and the grounding end is connected to a grounding device; the grounding end of the voltage divider is connected to the grounding device, and the voltage measuring end of the voltage divider is connected to the upper computer; the communication end of the current acquisition module is connected to the upper computer, and the test end of the current acquisition module is connected to the lead;
the soil box also comprises more than one insulating partition plate, and the insulating partition plates can be horizontally inserted into or pulled out of the soil box; when the insulating partition plate is inserted into the soil box, the soil box is divided into more than two spaces from bottom to top.
The second step is that: filling soil and setting temperature: opening a left panel of the soil box, and controlling the distance between the left copper electrode and the right copper electrode through a control mechanism; according to the thickness ratio of the soil to be tested, the soil box is layered by using an insulating partition plate, and soil samples are sequentially filled after layering; removing the insulating partition plate to enable the soil samples to be attached together; covering the left panel; monitoring the temperature through a first temperature sensor, a second temperature sensor, a third temperature sensor and a fourth temperature sensor; setting the test temperature to be T, and if the measured temperature exceeds the allowable upper limit T of the errormaxIf so, the digital controller starts a cooling mode of the temperature control device to cool; if the temperature is lower than the lower limit of the allowable error limit TminDigital controllerStarting a temperature rising mode of the temperature control device to rise the temperature; controlling the temperature of a soil sample in the soil box within a permissible range of a test temperature T error;
the third step: the voltage and current of the soil sample at the temperature T1 were measured: when the measured temperature of the soil sample is stabilized within the allowable range of the test temperature T error, starting an impulse current generator, measuring the voltage between a left copper electrode and a right copper electrode through a voltage divider and transmitting the voltage to an upper computer, and measuring the current flowing through the left copper electrode and the right copper electrode through a current acquisition module and transmitting the current to the upper computer;
the fourth step: evaluating the nonlinear characteristic of soil resistance: obtaining a voltage and current obtained by an upper computer to obtain an impulse resistance full time domain R (t) waveform curve, and extracting R (t)min，R(t)maxTime of fall Δ t1And effective recovery time Δ t2Calculating the average descending speed k of the soil under the impact current,
wherein R (t)minIs the minimum value of resistance in the R (t) waveform curve, R (t)maxIs the maximum value of resistance in the R (t) waveform curve, t1Denotes R (t) from the maximum value R (t)maxDown to a minimum value R (t)minThe time interval of (c);
calculation of R (t)minComposite evaluation factor q with k1：
Calculation of R (t)minAnd t1Composite judgment factor q of2：
The minimum radius of curvature γ is calculated approximately:
wherein,
in the formula, tm∈[ta+1,tb)，taIs R (t)maxCorresponding time tbIs R (t)minCorresponding to the time, the above formula shows that the R (t) wave curve is calculated in the descending time period from taAt the +1 moment, calculating the curvature radius of each moment at intervals of 0.1 mu s, and calculating the minimum curvature radius;
calculating a correction coefficient k considering the temperature and the minimum radius of curvature from the minimum radius of curvature1：
Wherein T is the test temperature;
calculating judgment remainders:
q3＝0.03258log(0.26Δt1+0.625Δt2-41.3)
-0.0953log(R(t)min+1.38)
in the formula, t2Denotes R (t) from R (t)minRising to effective recovery resistance R (t)effThe time of (d); wherein R (t)eff＝R(t)min+0.8(R(t)max-R(t)min),R(t)effDenotes the minimum value of R (t) from the resistance R (t)minGradual recovery, when the recovery amount is 80% of the maximum decrease difference (R (t))max-R(t)min) A resistance value corresponding to the time;
by combining the above calculations, the soil nonlinear characteristic evaluation factor of the soil under the impact current and temperature is:
q＝k1(q1+q2)+q3
according to the value range of q, the nonlinear characteristic of the resistor is represented;
the fifth step: and (3) testing the nonlinear characteristics of soil resistance at different temperatures: and setting different temperatures according to test requirements, repeating the third step and the fourth step, and performing nonlinear characteristic evaluation on the vertical stratified soil resistance at different temperatures.
The beneficial effect of the invention is that,
1) the soil is vertically layered, and the nonlinear resistance characteristic of the vertically layered soil is measured, so that the vertical layering working condition of the soil around the grounding system can be effectively simulated;
2) the full-time-domain change waveform curve of the vertical stratification soil resistance under the action of the impact current can be effectively obtained, and the nonlinear characteristic of the vertical stratification soil resistance can be accurately evaluated by using the evaluation factor;
3) the main operation and control are completed by an upper computer, the precise control of the vertical layering soil temperature is realized by combining a digital controller and a temperature control device, and the nonlinear characteristic of the resistance of the vertical layering soil at different temperatures can be effectively measured;
4) the experimental device is convenient to operate, safe and reliable, and has universality on tests of vertical multilayer soil.
Drawings
FIG. 1 is a schematic diagram of the general structure of the present invention;
FIG. 2 is a schematic structural view of the soil box of the present invention;
FIG. 3 is a flow chart of an experimental method in the invention;
FIG. 4 is a graphical illustration of a full time domain variation waveform of the impact resistance reflecting the dynamic resistance characteristics of the soil.
Detailed Description
The following further describes embodiments of the present invention with reference to the drawings. The method comprises the following steps:
the first step is as follows: building a vertical layered soil resistance nonlinear characteristic test platform
As shown in fig. 1 and 2, the test platform of the present invention comprises: a soil box (06); the inner wall of the soil box (06) is provided with a temperature control device (08); the left side wall of the soil box (06) is provided with a left copper electrode (05) and an operating mechanism (04) for controlling the left copper electrode (05) to move transversely; the right side wall of the soil box (06) is also provided with a right copper electrode (07); the left copper electrode (05) and the right copper electrode (07) are both vertical discs; the left upper part, the right upper part, the left lower part and the right lower part of the soil box are respectively provided with a first temperature sensor (01a), a second temperature sensor (01b), a third temperature sensor (01c) and a fourth temperature sensor (01d), and the soil box further comprises an impact current generator (12) and a voltage divider (13).
Wherein: the first temperature sensor (01a), the second temperature sensor (01b), the third temperature sensor (01c) and the fourth temperature sensor (01d) are respectively connected to the input end of a temperature analyzer (14), and the output end of the temperature analyzer (14) is respectively connected to the digital controller (15) and the upper computer (18); the digital controller (15) is connected to the temperature control device (08); the output end of the impulse current generator (12) is connected to the high-voltage end of the voltage divider (13), and the high-voltage end of the voltage divider (13) is connected to the left copper electrode (05) through a high-voltage cable (19) and a cable joint (03); the right copper electrode (07) is connected to the grounding end of the impulse current generator (12) through a lead (20), and the grounding end is connected to the grounding device (11); the grounding end of the voltage divider (13) is connected to the grounding device (11), and the voltage measuring end of the voltage divider (13) is connected to the upper computer (18); the communication end of the current acquisition module (17) is connected to the upper computer (18), and the test end of the current acquisition module (17) is connected to the lead (20); the soil box also comprises more than one insulation partition plate (09), and the insulation partition plates (09) can be horizontally inserted into or pulled out of the soil box (06); when the insulating partition plate (09) is inserted into the soil box (06), the soil box (06) is divided into more than two spaces from bottom to top, the number of layers is the limited number of layers of actual soil, if the actual soil is divided into 3 layers, each layer is limited in thickness, the thickness ratio of the soil can be obtained, the insulating partition plate (09) separates the soil in the soil box (06) according to the thickness ratio along the direction perpendicular to the surface of the electrode, and after the soil sample is filled, the insulating partition plate (09) is drawn out, and each layer of soil is tightly attached.
The second step is that: soil filling and temperature setting
Opening an upper panel of the soil box (06), and controlling the distance between the left copper electrode (05) and the right copper electrode (07) through a control mechanism (04); according to the thickness ratio of the soil to be tested, the soil box (06) is layered by using an insulating partition plate (09), and soil samples are sequentially filled after layering; and removing the insulating partition (09) to enable the soil samples to be attached together.
If the soil in a certain area is vertically layered, the thickness of the first layer of soil is 7m, the soil resistivity is 200 omega m, the thickness of the second layer of soil is 20m, the soil resistivity is 1000 omega m, the thickness of the third layer of soil is 39m, the soil resistivity is 500 omega m, and a soil area with infinite thickness is arranged outside the third layer of soil; the vertical delamination thickness ratio is 7: 20: and 39, if the distance between the upper box wall and the lower box wall of the soil box is s, dividing the distance according to the thickness ratio, layering the distance by using an insulating partition plate (09), and putting a soil sample into the soil sample, wherein the resistivity of each layer of soil of the soil sample is the same as that of the actual soil layer.
Covering the left panel; monitoring the temperature by a first temperature sensor (01a), a second temperature sensor (01b), a third temperature sensor (01c) and a fourth temperature sensor (01 d); setting the test temperature as T1, calculating the average value of the measured temperatures of the four sensors by the temperature analyzer, and if the allowable error of the temperature test is plus or minus 0.5 ℃, determining that the average value of the temperatures exceeds the allowable upper limit of the error TmaxIf so, the digital controller (15) starts the cooling mode of the temperature control device (08) to cool; if the average temperature value is lower than the lower allowable error limit TminIf so, the digital controller (15) starts the temperature rising mode of the temperature control device (08) to rise the temperature; controlling the temperature of the soil sample in the soil box (06) within the tolerance of the test temperature T1 (T)min～Tmax)。
The third step: measuring the voltage and current of a soil sample at a temperature T1
When the soil sample measurement temperature is stabilized within the error allowable range of the test temperature T1, the impact current generator (12) is started, the voltage between the left copper electrode (05) and the right copper electrode (07) is measured through the voltage divider (13) and transmitted to the upper computer (18), and the current flowing through the lead (20) is measured through the current collection module (17) and transmitted to the upper computer (18).
The fourth step: evaluating soil resistance non-linear characteristics
Obtaining a full time domain R (t) waveform curve of the impulse resistance through the voltage and the current obtained by an upper computer, and extracting a minimum value R (t) of the resistancemin(in Ω), maximum resistance R (t)max(unit is. omega.) belowFall time Δ t1(measured in mus) and effective recovery time Δ t2(measured in mus), calculating the average rate of fall k of the soil under the impact current:
wherein R (t)minIs the minimum value of resistance in the R (t) waveform curve, R (t)maxIs the maximum value of resistance, Δ t, in the R (t) waveform curve1Denotes R (t) from the maximum value R (t)maxDown to a minimum value R (t)minThe time interval of (c);
calculation of R (t)minComposite evaluation factor q with k1：
Calculation of R (t)minAnd t1Composite judgment factor q of2：
The minimum radius of curvature γ is calculated approximately:
wherein,
in the formula, tm∈[ta+1,tb)，taIs R (t)maxCorresponding time tbIs R (t)minCorresponding to the time, the above formula shows that the R (t) wave curve is calculated in the descending time period from taAt the +1 moment, calculating the curvature radius of each moment at intervals of 0.1 mu s, and calculating the minimum curvature radius;
calculated from the minimum radius of curvatureCorrection factor k taking into account temperature and minimum radius of curvature1：
Calculating judgment remainders:
q3＝0.3258log(0.26Δt1+0.625Δt2-41.3)
-0.0953log(R(t)min+1.38)
in the formula, t2Denotes R (t) from R (t)minRising to effective recovery resistance R (t)effThe time of (d); wherein R (t)eff＝R(t)min+0.8(R(t)max-R(t)min),R(t)effDenotes the minimum value of R (t) from the resistance R (t)minGradual recovery, when the recovery amount is 80% of the maximum decrease difference (R (t))max-R(t)min) A resistance value corresponding to the time;
by combining the above calculations, the evaluation factor of the nonlinear resistance characteristic of the soil under the impact current and the temperature is as follows:
q＝k1(q1+q2)+q3
and (5) representing the nonlinear characteristic of the resistor according to the value range of q.
The fifth step: soil resistance nonlinear characteristic test at different temperatures
And setting different temperatures according to the test requirements, repeating the test, and performing the nonlinear characteristic test of the vertical stratified soil resistance at different temperatures. If T2 and T3 vertical stratification soil resistance nonlinear characteristics need to be tested, after the T1 test is finished, after a certain time interval, the set temperature of the temperature analyzer (14) is set to be T2, the third step and the fourth step are repeated, the soil resistance nonlinear characteristics at the temperature of T2 are tested, and after a certain time interval, the soil resistance nonlinear characteristics at the temperature of T3 are tested.
Claims (1)
1. A vertical stratification soil resistance nonlinear characteristic test method is characterized by comprising the following steps:
the first step is as follows: a test platform for building nonlinear characteristics of vertical layered soil resistance comprises
A soil box (06); the inner wall of the soil box (06) is provided with a temperature control device (08); the left side wall of the soil box (06) is provided with a left copper electrode (05) and an operating mechanism (04) for controlling the left copper electrode (05) to move transversely; the right side wall of the soil box (06) is also provided with a right copper electrode (07); the left copper electrode (05) and the right copper electrode (07) are both vertical circles; the left upper part, the right upper part, the left lower part and the right lower part of the soil box are respectively provided with a first temperature sensor (01a), a second temperature sensor (01b), a third temperature sensor (01c) and a fourth temperature sensor (01d), and further comprise an impact current generator (12) and a voltage divider (13);
wherein: the first temperature sensor (01a), the second temperature sensor (01b), the third temperature sensor (01c) and the fourth temperature sensor (01d) are respectively connected to the input end of a temperature analyzer (14), and the output end of the temperature analyzer (14) is respectively connected to the digital controller (15) and the upper computer (18); the digital controller (15) is connected to the temperature control device (08);
the output end of the impulse current generator (12) is connected to the high-voltage end of the voltage divider (13), and the high-voltage end of the voltage divider (13) is connected to the left copper electrode (05) through a high-voltage cable (19) and a cable joint (03); the right copper electrode (07) is connected to the grounding end of the impulse current generator (12) through a lead (20), and the grounding end is connected to the grounding device (11); the grounding end of the voltage divider (13) is grounded, and the voltage measuring end of the voltage divider is connected to the upper computer (18); the communication end of the current acquisition module (17) is connected to the upper computer (18), and the test end of the current acquisition module (17) is connected to the lead (20) and used for measuring the current flowing through the left copper electrode (05) and the right copper electrode (07); the soil box also comprises more than one insulation partition plate (09), and the insulation partition plates (09) can be horizontally inserted into or pulled out of the soil box (06); when the insulating partition plate (09) is inserted into the soil box (06), the soil box (06) is divided into more than two spaces from bottom to top;
the second step is that: soil filling and temperature setting: opening a left panel of the soil box (06), and controlling the distance between the left copper electrode (05) and the right copper electrode (07) through a control mechanism (04); according to the thickness ratio of the soil to be tested, the soil box (06) is layered by an insulating partition plate (09) and then filled with a soil sample; removing the insulating partition (09) to make the soil sampleThe products are adhered together; covering the left panel; monitoring the temperature by a first temperature sensor (01a), a second temperature sensor (01b), a third temperature sensor (01c) and a fourth temperature sensor (01 d); setting the test temperature to be T, and if the measured temperature exceeds the allowable upper limit T of the errormaxIf so, the digital controller (15) starts the cooling mode of the temperature control device (08) to cool; if the temperature is lower than the lower limit of the allowable error limit TminIf so, the digital controller (15) starts the temperature rising mode of the temperature control device (08) to rise the temperature; controlling the temperature of the soil sample in the soil box (06) within the allowable range of the test temperature T error;
the third step: measuring the voltage and current of the soil sample at the temperature T: when the soil sample measurement temperature is stabilized within the test temperature T error allowable range, starting the impulse current generator (12), measuring the voltage between the left copper electrode (05) and the right copper electrode (07) through the voltage divider (13) and transmitting the voltage to the upper computer (18), measuring the current flowing through the lead (20) through the current acquisition module (17) and transmitting the current to the upper computer (18);
the fourth step: evaluating the nonlinear characteristic of soil resistance: obtaining a voltage and current obtained by an upper computer to obtain an impulse resistance full time domain R (t) waveform curve, and extracting R (t)min，R(t)maxTime of fall Δ t1And effective recovery time Δ t2Calculating the average descending speed k of the soil under the impact current,
wherein R (t)minIs the minimum value of resistance in the R (t) waveform curve, R (t)maxIs the maximum value of resistance, Δ t, in the R (t) waveform curve1Denotes R (t) from the maximum value R (t)maxDown to a minimum value R (t)minThe time interval of (c);
calculation of R (t)minComposite evaluation factor q with k1：
Calculating R (t))minAnd Δ t1Composite judgment factor q of2：
The minimum radius of curvature γ is calculated approximately:
wherein,
in the formula, tm∈[ta+1,tb)，taIs R (t)maxCorresponding time tbIs R (t)mAt the time corresponding to in, the above formula shows that the waveform curve of R (t) is calculated in the descending time period from taAt the +1 moment, calculating the curvature radius of each moment at intervals of 0.1 mu s, and calculating the minimum curvature radius;
calculating a correction coefficient k considering the temperature and the minimum radius of curvature from the minimum radius of curvature1：
Wherein T is the test temperature;
calculating judgment remainders:
q3＝0.03258log(0.26Δt1+0.625Δt2-41.3)
-0.0953log(R(t)min+1.38)
in the formula, t2Denotes R (t) from R (t)minRising to effective recovery resistance R (t)effThe time of (d); wherein R (t)eff＝R(t)min+0.8(R(t)max-R(t)min),R(t)effDenotes the minimum value of R (t) from the resistance R (t)minGradual recovery, when the recovery amount is 80% of the maximum decrease difference (R (t))max-R(t)min) A resistance value corresponding to the time;
by combining the above calculations, the soil nonlinear characteristic evaluation factor of the soil under the impact current and temperature is:
q＝k1(q1+q2)+q3
according to the value range of q, the nonlinear characteristic of the resistor is represented;
the fifth step: and (3) testing the nonlinear characteristics of soil resistance at different temperatures: and setting different temperatures according to test requirements, repeating the third step and the fourth step, and performing nonlinear characteristic evaluation on the vertical stratified soil resistance at different temperatures.
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