What instrument is the most accurate way to measure the soil resistivity of a power station?

Venner quadrupole method, when the maximum diagonal d of the tested grounding device is large, or in some areas (mountainous or urban areas) it is difficult to arrange the current pole and voltage pole according to the requirements, the two-phase wire of the primary transmission line of the substation can be used as the current line and voltage line. The four poles refer to the grounding device G to be measured, the current pole C and the voltage pole P for measurement, and the auxiliary electrode S. The distance of the auxiliary electrode s from the edge of the grounding device to be tested dgs = 30 100m.

The principle wiring diagram of the quadrupole method for measuring soil resistivity, the distance between the two electrodes a should be equal to or greater than 20 times the electrode burial depth h, i.e. a 20h. From the measured value r of the grounding resistance measuring instrument, the apparent soil resistivity of the measured site = 2 ar is recommended to use a round steel with a diameter of not less than or an angle steel of 25 25 4, the length of which is not less than 1000px. The depth of the current field in the soil of the measured site, i.e., the depth of the soil being measured, is closely related to the distance a between the poles.

When the area of the measured field is large, the distance between the poles a should be increased accordingly. In order to obtain a more reasonable data of soil resistivity, it is best to change the distance between the poles a, and obtain the relationship curve = f(a) between the apparent soil resistivity and the distance a between the poles, the value of the distance between the poles can be m, and the maximum distance between the poles can be two-thirds of the maximum diagonal of the proposed grounding device. The calculated value of soil resistivity obtained by the Wenner quadrupole method test should be corrected according to the seasonal coefficient at the time of measurement.

When calculating the soil resistivity of the grounding device, the maximum soil resistivity should be taken when there is no rain during the thunderstorm season. <>

Analog method, analog method is also called three-pole method, where the three poles refer to the measured grounding device g, the voltage pole p and the current pole c for measurement. The distance between the current pole c and the voltage pole p to be measured from the edge of the measured grounding device g is dgc=(4 5)d and dgp=(, d is the maximum diagonal length of the measured grounding device, and the point p can be considered to be in the actual zero potential region. If you want to find the actual zero potential region more accurately, you can move the voltage pole three times in the direction of the connection line between the measuring current pole and the grounding device to be measured, and the distance of each movement is about 5% of the DGC, and the voltage between the voltage pole P and the grounding device G can be measured.

If the relative error between the three indications of the voltmeter does not exceed 5%, the intermediate position can be used as the position of the voltage pole for measurement. Divide the indicated value ug of the voltmeter by the indicated value i of the ammeter to obtain the power frequency grounding resistance RG of the grounding device under test. If it is difficult to take the (4 5)d value of DGC when measuring the power frequency grounding resistance, then when the soil resistivity around the grounding device is relatively uniform, the DGC can take the 2D value and the DGP take the D value; When the soil resistivity around the grounding device is not uniform, the dgc can take the 3d value and the dgp value.

If the resistivity of the soil around the grounding device is relatively uniform, the power frequency grounding resistance can also be measured by arranging the electrodes in a triangle. The angle between the connecting wire of the equivalent center of the voltage pole and the grounding device and the connecting wire of the equivalent center of the current pole and the equivalent center of the grounding device is generally taken as dgp dgc=2d, 30°. When the maximum diagonal of the grounding device is small, and the power frequency grounding resistance value is greater than that, the grounding resistance can also be measured with a grounding resistance measuring instrument, but its voltage pole and current pole should be arranged according to the previously mentioned requirements.

The simulation method for measuring soil resistivity is to drive a vertical ground body into the measured site, and measure the grounding resistance value r of the grounding body with a grounding resistance measuring instrument. <>

The simulation method is only suitable for sites with more uniform soil resistivity. Due to the inhomogeneity of the soil structure, the measuring electrodes should be placed on uneven soils with obvious rocks, cracks, and slopes. In order to obtain more reliable measurement results, the nine-point method (i.e., the measured field is divided into nine panels, multiple measurements are made, and the soil resistivity table is taken as the average of the measurement results).

The nine-point method is usually used to measure soil resistivity at nine points at the four corners of the designed grid, the midpoint of the four outer edges and the center point of the grid. The calculated value of soil resistivity obtained by the simulation method should be corrected according to the situation at the time of measurement. <>

There are three pole method and four pole method for soil resistivity test.

1. Three-pole method to measure soil resistivity (rarely used in engineering practice): where soil resistivity needs to be measured, the grounding body with the geometric size of the self-knowledge is embedded, and the grounding resistance of the grounding body is measured according to the voltage and current method.

The grounding body used for measurement is a steel pipe with a length of 3m and a diameter of 50mm; or 3m long, 25mm diameter round bar; or 10 15m long, 40mm 4mm flat bar, which is adjusted into the depth m.

The round steel is used vertically driven into the soil, and when the grounding resistance is measured, the voltage pole can be 20m away from the current pole and the measured grounding body. Once the ground resistance is measured, the soil resistivity can be calculated. i.e., (2 hrg) [1N(4h d)].

When measuring the soil resistivity on the standby side by the tripolar method, the soil near the grounding body plays a decisive role, and the measured soil resistivity only reflects the soil resistivity near the grounding body to a large extent.

2. Four-pole method to measure soil resistivity: when the four-stage method is used to measure soil resistivity, current i is introduced from the outer electrode C1 and C2, if the buried depth of the electrode is H and the distance between the electrodes is Ah, then the voltages on P1 and P2 are respectively U2 I 2 [1 1 2]; u'2＝ρi／2π[1／2α－1／α]

And the potential difference between the two poles is: u2 u'2＝ρh／2πα。Therefore [2 (u2 u'2)]／i＝2πα(u／i)＝2παrg (1-1)。

Use.

The following precautions are taken when measuring by the three- and quadrupole method:

1. When measuring the soil resistivity by the tripolar method, the soil near the grounding body plays a decisive role, and the measured soil resistivity only reflects the soil resistivity near the grounding body to a large extent.

2. When the soil resistivity measured by the running substation is measured, because the current is affected by the horizontal grounding body in the ground, it is necessary to find a place with the same soil quality away from the grounding grid.

3. In order to fully understand the horizontal distribution of resistivity, it is necessary to find different 4 6 points in the range to be tested.

4. In order to understand the stratification of the soil, several different A values should be changed for measurement, such as A m, etc.

5. When measuring soil resistivity, try to avoid underground pipelines, so as not to affect the test results.

6. Do not measure soil resistivity when the soil is wet after rain. When measuring, if the soil is relatively dry, the lower value in the table is used for calculation; If the soil is more humid, the higher value is used.

What is Conductivity? As the name suggests, conductivity is the ability to conduct electricity, and measuring conductivity (or conductivity for short) is the most commonly used electrochemical analysis method after measuring pH.

The EM38-MK2 geodetic conductivity meter is a precision instrument designed for agricultural surveys of soil salinity, and can quickly cover large areas without grounding electrodes, and can also collect soil conductivity and magnetization data at the same time. It is available in two models, the EM38-MK2-1 and the EM38MK2 model. It can be widely used in agriculture, archaeology and soil science for near-earth exploration, such as soil salinity survey, earth-rock dam leakage channel detection, highway foundation structure, geological structure survey, etc.

Principle: There is a small transmitting coil at the back end of the EM38 conductivity meter, which can generate a primary magnetic field that varies with time, this magnetic field induces a tiny electron eddy current in the earth, and at the same time there is a small receiving coil at the front end, this receiver receives both the magnetic field generated by the transmitter coil and the secondary magnetic field induced by the primary magnetic field, and measures the earth conductivity by measuring the induced secondary magnetic field.

Hello, I am glad to serve you and give you the following answers: soil resistivity is related to ranging, the larger the ranging, the smaller the soil resistivity, this is because the charge in the soil is uneven, when the distance is larger, the more uneven the charge distribution, the smaller the soil resistivity. The solutions to this problem are:

1.First of all, to improve the charge distribution of the soil, soil improvement methods can be adopted, such as applying organic fertilizer, improving the soil structure, etc., to improve the charge distribution of the soil, so as to increase the soil resistivity. 2.

Secondly, reasonable ranging methods should be adopted, such as short-distance ranging, to reduce the ranging distance, so as to improve soil resistivity. 3Finally, it is necessary to adopt reasonable measurement methods, such as multi-point measurement methods, to reduce measurement errors and thus improve soil resistivity.

Personal Tips:1When measuring soil resistivity, attention should be paid to improving the charge distribution of the soil to increase soil resistivity.

2.When measuring the resistivity of soil resistance, it is necessary to pay attention to the use of reasonable ranging methods to reduce the ranging distance and improve the soil resistivity. 3.

When measuring soil resistivity, it is necessary to pay attention to the use of reasonable measurement methods to reduce the measurement error and improve the soil resistivity.

Soil resistivity depends mainly on soil properties and ranges from marshy to rocky 300002·m or even higher.

Calculated from the formula r=l a, it usually refers to the resistance of 1m3 of land. The magnetic coupling between transmission lines and communication lines is mainly dominated by the zero-sequence component (the zero-sequence component is an order of magnitude or more larger than the positive sequence component), so soil resistivity is a key parameter affecting the mutual impedance of the two lines.

Soil resistivity depends mainly on soil properties and ranges from marshy to rocky 300002·m or even higher. The typical value of soil resistivity for general applications is 100 ·m. It should be noted that the resistivity of most lands is not constant, but only one constant value is often used in the calculations.

Method of measuring soil resistivity: the grounding resistance is measured on the grounding body, and after the grounding resistance is measured, the soil resistivity is calculated according to the following formula:

1. When using steel pipe or round steel as the grounding body: =2 RJL (LN(4L D))=RJL (. l is the length of the steel pipe or round steel into the ground, in m; d is the diameter of the steel pipe or round bar, in m; rj is the measured ground resistance value in units.

2. When using a flat steel as a grounding body: =2 RJL (LN(2L 2 (BH)))RJL (. l is the length of the flat bar, in m; b is the thickness of the flat bar, in m; h is the burial depth, unit m.

The soil resistivity is as follows:

Soil resistivity is the average value of soil resistance per unit length in ohms-meters. Soil resistivity is a commonly used parameter in grounding engineering calculations, which directly affects the size of the grounding resistance of the grounding device, the ground potential distribution of the ground grid, the contact voltage and the step voltage.

Soil resistivity is an important factor in the resistance of the grounding body in the final draft, and in order to reasonably design the grounding rough device, the soil resistivity must be measured, so that the measured resistivity can be used as the calculation parameter of the grounding resistance. One of the ways to measure soil resistivity is to measure the grounding resistance of the grounding body, measure the resistance of the grounding body, and then calculate the soil resistivity according to the following formula.

When using steel pipe or round steel as the grounding body, =2 RJL (LN(4L D))=RJL (. where l is the length of the steel pipe or round steel into the ground, the unit is the diameter of the steel pipe or round bar, and the unit is the measured grounding resistance value, unit.

When using a flat bar as a grounding body: =2 RJL (LN(2L 2 (BH)))RJL (。 where l is the length of the flat bar, the unit is the thickness of the flat bar, the unit is the depth of burial, and the unit is m.

The four-pole electric bathymetry method has passed the practical test, and its accuracy can fully meet the requirements of engineering calculation, and this measurement method requires less instrumentation and equipment, and the simple operation has become a commonly used method in engineering design. Therefore, four-electrode bathymetry is recommended to measure soil resistivity.

Note: The value of a is the burial depth of the grounding body A is generally taken 5m, and for the building with a deep foundation, the foundation is a part of the grounding body, then a can be taken 10m.

The four poles are laid out in a straight line, and the poles are equally spaced apart by a.

When wiring, disconnect the short-circuit pieces between the P2 and C2 terminals on the instrument.

The connection order between Pole and the terminal blocks on the meter cannot be reversed.

The depth of each pole should not exceed 1 20 of the pole spacing a.

In order to avoid the interference of the metal objects buried in the ground to the measurement, the direction of the grounding rod arrangement can be perpendicular to the direction of the underground metal objects (pipelines) under the condition of understanding the position of the underground metal objects.