阅读说明：本技术 一种多点分布阳极接地网阴极保护方法 (Cathode protection method for multipoint distribution anode grounding grid ) 是由 邵洪平 熊杰 陈亮 马列中 李学腾 于 2019-10-09 设计创作，主要内容包括：本发明提供一种多点分布阳极接地网阴极保护方法,包括以下步骤：步骤一：等间距安放参比电极；步骤二：安放牺牲电极,配备好填包料；步骤三：连接三电极系统；步骤四：开路电位测试；步骤五：恒电流阶跃测试；步骤六：恒电位阶跃测试；步骤七：多点开路电位分布测试；步骤八：汇总数据,分析并得出结论。本发明多点分布阳极接地网阴极保护方法用于开发电化学信号的接地网检测与分析方法,检测不同位置的极化阻力的差异,利用建立的方法检测不同位置是否存在局部腐蚀,通过计算电流分布特征,实现现场不开挖检测,对检测数据建立分析方法,得到表征反映腐蚀状况的参数,实现腐蚀的预测,实现在保护阴极的情况下分析电位分布规律。(The invention provides a multipoint distribution anode grounding grid cathode protection method, which comprises the following steps: the method comprises the following steps: placing reference electrodes at equal intervals; step two: placing a sacrificial electrode and preparing a packing material; step three: connecting a three-electrode system; step four: testing open circuit potential; step five: constant current step test; step six: constant potential step test; step seven: testing the distribution of the multipoint open-circuit potential; step eight: the data is summarized, analyzed and concluded. The multipoint distribution anode grounding grid cathode protection method is used for developing a grounding grid detection and analysis method of electrochemical signals, detecting the difference of polarization resistance at different positions, detecting whether local corrosion exists at different positions by using the established method, realizing on-site trenchless detection by calculating current distribution characteristics, establishing an analysis method for detection data, obtaining parameters representing and reflecting corrosion conditions, realizing corrosion prediction and realizing analysis of potential distribution rules under the condition of protecting cathodes.)

1. A multipoint distribution anode grounding grid cathode protection method is characterized in that: the method comprises the following steps:

the method comprises the following steps: placing reference electrodes at equal intervals;

step two: placing a sacrificial electrode and preparing a packing material;

step three: connecting a three-electrode system;

step four: testing open circuit potential;

step five: constant current step test;

step six: constant potential step test;

step seven: testing the distribution of the multipoint open-circuit potential;

step eight: the data is summarized, analyzed and concluded,

the three-electrode system comprises a reference electrode, an auxiliary electrode and a working electrode, wherein the reference electrode is a saturated copper sulfate electrode, and the auxiliary electrode is 316L stainless steel.

2. The method of claim 1, wherein the method comprises the following steps: the magnesium alloy sacrificial anode is connected to the grounding grid and serves as a working electrode, and the magnesium alloy sacrificial anode is placed in a net shape.

3. The method of claim 2, wherein the method comprises the following steps: the filling material is mainly formed by mixing 75% of calcium sulfate, 20% of bentonite and 5% of sodium sulfate.

4. The method of claim 3, wherein the method comprises the following steps: the magnesium alloy sacrificial anode is set to be arranged one by one in 20kg of grounding grid.

5. The method of claim 4, wherein the method comprises the following steps: the saturated copper sulfate electrodes are placed in a net-shaped sequence and connected to a ZF-10B data acquisition memory to sequentially acquire electrochemical signals.

Technical Field

The invention relates to the field of grounding grid cathodic protection, in particular to a multipoint distribution anode grounding grid cathodic protection method.

Background

The grounding grid is an electrical facility buried for preventing grounding short circuit current from endangering the safety of people and equipment, plays a role in current leakage and voltage sharing on lightning, static electricity and fault current, and is a powerful guarantee for safe and reliable operation of a power system and the safety of electrical equipment and people. However, since the grounding device runs underground for a long time, the running environment is severe and corrosion is easy to occur. In recent years, the problem of exposure of the grounding grid is more and more prominent, and the grounding grid is generally rotten for 10 years and is rotten for 4 years according to surveys of Guangdong, Shandong, Jiangsu, Anhui and the like. Carrying out excavation inspection on a grounding grid in Guangdong province, and finding that the grounding grid of the substation which runs for more than 20 years is seriously corroded; after the grounding grid of the 35-220 kV transformer substation which operates for more than 10 years is excavated by Guangxi province, corrosion of different degrees is found; hubei province finds that the grounding grid operating for 5 years has corroded, and the grounding grid operating for 30 years has very serious corrosion. Meanwhile, similar corrosion phenomena are found after excavation inspection in Jiangxi province, Jiangsu province, Anhui province and other provinces.

The good grounding of the power generation and transformation station is the fundamental guarantee of the safe operation of the power system, and is the unification of lightning protection grounding, protection grounding and working grounding. In recent years, with the development of power systems, the current flowing through the earth grid during a fault is increasing, and accidents caused by the defects of grounding measures are also frequent, and the grounding problem is generally regarded.

At present, when transformer substation grounding grid design and construction are carried out in China, related corrosion data manuals are generally consulted first, and the size and the number of grounding grid materials are calculated according to design service life requirements. The data of the handbooks are all from specific areas where the samples are buried, and the searched data has no good guiding effect on each specific transformer substation because different areas have different climatic conditions and the physical and chemical properties of the soil generally have larger difference. Therefore, it is necessary to investigate and predict soil erosion based on the soil properties of different areas. In the method, test points are selected in a region needing to be predicted, a tablet burying test is carried out, and meanwhile, the soil chemical components of each test point are detected, wherein the test period is one year to two years. After the test is finished, the test material is taken back, the corrosion rate is calculated through a weight loss method, regression analysis is carried out through a statistical method of stepwise regression analysis, and a regression equation is established to predict the corrosion rate. Because of adopting the embedded test, the test period needs one to two years, and the test period is longer. The motivation of regression analysis is to hopefully find a function to replace a data set, but it assumes that the variables of the data set have a causal relationship, and generally needs to give a mathematical undetermined basis function, and calculate the undetermined parameter of the mathematical basis function according to the causal relationship of the variables in the data set. This method of assuming beforehand that the data follows some distribution is not reasonable for some unknown worlds of interpretation, as this assumption may be wrong. Therefore, the problem of predicting the corrosion rate of the grounding grid cannot be well solved by a parameter analysis method.

Generally, the grounding grid has a large area, a long extension distance and a complex corrosion condition, so that great difficulty is caused in corrosion detection. The problem of detecting the corrosion of the grounding grid is not completely solved, and the reasonable and accurate detection of the corrosion condition of the grounding grid is the development direction of safe operation of the grounding grid. Meanwhile, the research on the cathodic protection technology in the typical soil environment is carried out, and the method has important academic value and practical significance.

Disclosure of Invention

Based on the defects of the prior art, the invention aims to provide a multipoint distribution anode grounding grid cathode protection method which comprises the following steps:

the method comprises the following steps: placing reference electrodes at equal intervals;

step two: placing a sacrificial electrode and preparing a packing material;

step three: connecting a three-electrode system;

step four: testing open circuit potential;

step five: constant current step test;

step six: constant potential step test;

step seven: testing the distribution of the multipoint open-circuit potential;

step eight: the data is summarized, analyzed and concluded,

the three-electrode system comprises a reference electrode, an auxiliary electrode and a working electrode, wherein the reference electrode is a saturated copper sulfate electrode, and the auxiliary electrode is 316L stainless steel.

As an improvement of the cathodic protection method of the multipoint distribution anode grounding grid, the cathodic protection method of the multipoint distribution anode grounding grid further comprises a magnesium alloy sacrificial anode, the magnesium alloy sacrificial anode is connected to the grounding grid and serves as a working electrode, and the magnesium alloy sacrificial anode is placed in a net shape.

As an improvement of the multipoint distribution anode grounding grid cathodic protection method, the filling material of the multipoint distribution anode grounding grid cathodic protection method is mainly formed by mixing 75% of calcium sulfate, 20% of bentonite and 5% of sodium sulfate.

As an improvement of the multipoint distribution anode grounding grid cathodic protection method, the magnesium alloy sacrificial anode of the multipoint distribution anode grounding grid cathodic protection method is set to be arranged every 20kg of grounding grid. .

As an improvement of the multipoint distribution anode grounding network cathode protection method, the saturated copper sulfate electrodes of the multipoint distribution anode grounding network cathode protection method are placed in a net-shaped sequence and connected to a ZF-10B data acquisition memory to sequentially acquire electrochemical signals.

Compared with the prior art, the multipoint distribution anode grounding grid cathode protection method has the following beneficial effects: the method comprises the steps of detecting the difference of polarization resistance at different positions, detecting whether local corrosion exists at different positions by using an established method, realizing on-site trenchless detection by calculating current distribution characteristics, establishing an analysis method for detection data, obtaining parameters representing and reflecting corrosion conditions, realizing corrosion prediction, and realizing analysis of potential distribution rules under the condition of protecting a cathode.

Drawings

Fig. 1 is a schematic flow chart showing the steps of the cathode protection method of the multipoint distribution anode grounding grid according to the preferred embodiment of the invention.

Fig. 2 is an equivalent circuit diagram of the potentiostatic corrosion system of the preferred embodiment of the method of cathodic protection of a multipoint distribution anodic grounding grid of the present invention.

Fig. 3 is the constant potential charging curve diagram of the preferred embodiment of the multipoint distribution anode grounding grid cathodic protection method of the present invention.

Fig. 4 is the equivalent circuit of the constant current corrosion system of the preferred embodiment of the multipoint distribution anode grounding grid cathodic protection method of the present invention.

Fig. 5 is the constant current charging curve diagram of the preferred embodiment of the multipoint distribution anode grounding grid cathodic protection method of the present invention.

Fig. 6 is a constant current charging curve when the dielectric resistance is negligible according to the preferred embodiment of the method for protecting the cathode of the multi-point distribution anode grounding grid of the present invention.

Fig. 7 is a schematic diagram of the 316L stainless steel auxiliary electrode according to the preferred embodiment of the multipoint distribution anode grounding grid cathodic protection method of the present invention.

Fig. 8 is a schematic view of the saturated copper sulfate reference electrode in the preferred embodiment of the multipoint distribution anode grounding grid cathodic protection method of the present invention.

Fig. 9 is a schematic view of the sacrificial anode according to the preferred embodiment of the cathode protection method of the multipoint distribution anode grounding grid of the present invention.

Fig. 10 is a schematic diagram of the electrode wiring of the preferred embodiment of the cathode protection method of the multipoint distribution anode grounding grid of the present invention.

Fig. 11 is a top view of the electrode wiring of the preferred embodiment of the multi-spot distribution anode grounding grid cathodic protection method of the present invention.

FIG. 12 is the potential change at different distances of 5mA constant current step in the preferred embodiment of the method for cathodic protection of a multipoint distribution anode grounding grid of the present invention.

FIG. 13 is the potential variation at different distances of constant potential of 200mV for the preferred embodiment of the multi-spot distribution anode grounding grid cathodic protection method of the present invention.

Fig. 14 is a distribution diagram of the potential of the anode grounding grid without sacrificial layer according to the preferred embodiment of the cathode protection method of the anode grounding grid with multi-point distribution of the invention.

Fig. 15 is a diagram of the distribution of the potential of the grounding grid when the sacrificial anode is connected according to the preferred embodiment of the cathode protection method of the multipoint distribution anode grounding grid of the present invention.

Detailed Description

The multipoint distribution anode grounding grid cathode protection method is suitable for trenchless corrosion determination of the grounding grid.

Referring to fig. 1, fig. 2, fig. 3, fig. 4, fig. 5, fig. 6, fig. 7, fig. 8, fig. 9, fig. 10, fig. 11, fig. 12, fig. 13, fig. 14, fig. 15, a preferred embodiment of the multipoint distribution anode grounding grid cathodic protection method of the present invention is described in detail.

In this embodiment, the method for protecting the cathode of the multipoint distribution anode grounding grid of the present invention includes the following steps:

the method comprises the following steps: placing reference electrodes at equal intervals;

step two: placing a sacrificial electrode and preparing a packing material;

step three: connecting a three-electrode system;

step four: testing open circuit potential;

step five: constant current step test;

step six: constant potential step test;

step seven: testing the distribution of the multipoint open-circuit potential;

step eight: the data is summarized, analyzed and concluded,

the three-electrode system comprises a reference electrode, an auxiliary electrode and a working electrode, wherein the reference electrode is a saturated copper sulfate electrode, and the auxiliary electrode is 316L stainless steel.

In an embodiment, the linear polarization technique, the galvanostatic step and potentiostatic step test principle are as follows:

linear polarization, also known as polarization resistance, is achieved by applying a small signal to the test system to maintain the potential near the corrosion potential, the change in current and potential can be viewed as approximately linear, and the slope of the line is known as the polarization resistance, and is denoted by Rp:

the corrosion current density can then be calculated by the linear polarization equation, namely the Stern-earth equation:

in the formula: betaa, betac-the anodic and cathodic tafel slopes of the erosion electrode.

The equivalent circuit of the corrosion system at the constant potential step is shown in FIG. 2. Because the applied polarization potential E is small, both Rp and Cd can be considered constant.

I＝I_C+I_R(1)

By bringing formulae (2) and (3) into formula (1), can be obtained

R is a parallel resistance of Rp and R1

Bringing formula (5) into formula (4) then

Equation (6) is a first order linear non-homogeneous differential equation whose solution is:

when t is 0, I is E/R1, taken into formula (7), to give

In the carry-over (7), the following are obtained:

(9) the equation is a constant potential charging curve equation, and the relationship of I-t is shown in FIG. 3

(9) The two limiting cases of formula are:

when t is equal to 0, the reaction solution is,

as t approaches infinity, the time t approaches infinity,

if a symmetrical square wave potential is applied to the system, the relation equation of I-t is as follows:

wherein T is the period of applying a constant potential square wave and R is given by formula (5).

Constant current step test

When a small constant current I is applied to the corrosion system, resulting in a small polarization, the equivalent circuit of the corrosion system is shown in fig. 3.

As can be seen from fig. 3:

I＝I_C+I_R(11)

E＝IR₁+E₁(12)

establishing a differential equation, because the polarization is very small, it can be considered that Cd and Rp are constants

By substituting formulae (13) and (14) for formula (12), it is possible to obtain:

this equation belongs to a first order linear non-homogeneous differential equation whose solution is:

in the limit case: when t is 0, E1 is 0, the formula (16) is substituted to obtain a-IRp, and the formula (16) is further substituted

Carry on to formula (12) to obtain

Equation (18) is the constant current charge curve equation. FIG. 4 is a graph of E-t curve.

The limiting case of equation (18) is:

when t is 0, E0 is IR1

When t approaches infinity, E_∞＝IR₁+IR_p。

Therefore, the value of the resistance R1 of the medium can be calculated according to the instantaneous jump value of the E-t curve through the constant current step.

If the dielectric resistance R1 is small and negligible, equation (18) can be simplified to

The corresponding E-t curve for the case of equation (19) is shown in FIG. 5, which corresponds to the limiting case

When t is 0, E0 is 0

When t approaches infinity, E_∞＝IR_p

By changing τ to R_rC_dCalled the time constant of the corrosion system. This time constant is a parameter used to reflect the ease with which the system reaches steady state. In general, when t is 4 τ, the potential reaches 98% of the steady state value, and when t is 5, the system substantially reaches the steady state. The larger the time constant τ, the less likely it is to reach steady state. Therefore, the lower the corrosion rate is, the larger Rp is, the larger the time constant tau is, the longer the time for the system to reach the steady state is, and the more difficult the test is, in this case, the electrochemical parameters such as Rp, Cd can be directly solved by the equation analysis of the charging curve through the curve when the constant current charging curve does not reach the steady state.

When a constant current square wave is applied to the corrosion system, the E-t curve equation can also be obtained by the same method:

where T is the period of the applied constant current square wave.

The charging curve I-t of constant potential step decreases with time, the charging curve E-t of constant current step increases with time, and the time constants are tau-R_rC_d

For the same corrosion system, the electrochemical parameters Rp and Cd are the same, if a constant potential step test is adopted, the time constant of the system is short, and the system is easier to reach a steady state, so the constant potential step test is more favorable for the measurement of Rp than the constant current step test.

It is thus shown that both potentiostatic and galvanostatic step tests can be used to detect corrosion of the earth grid, using the potentiostatic step test if the medium resistance of the soil is particularly high, and vice versa.

In this embodiment, the method for protecting the cathode of the multipoint distribution anode grounding grid further includes a magnesium alloy sacrificial anode, the grounding grid is connected to the magnesium alloy sacrificial anode to serve as a working electrode, and the magnesium alloy sacrificial anode is placed in a mesh shape.

In this embodiment, the packing material of the method for protecting the cathode of the multipoint distribution anode grounding grid of the present invention is mainly formed by mixing 75% of calcium sulfate, 20% of bentonite and 5% of sodium sulfate.

In this embodiment, the magnesium alloy sacrificial anode of the cathode protection method of the multipoint distribution anode grounding grid of the present invention is set to be disposed one per 20kg of grounding grid.

In this embodiment, the saturated copper sulfate electrodes of the multipoint distribution anode grounding grid cathode protection method of the present invention are placed in a mesh sequence, and are connected to a ZF-10B data acquisition memory to sequentially acquire electrochemical signals.

In this embodiment, the method is mainly used for testing a plurality of small magnesium alloy sacrificial anodes inserted in the range of the grounding grid, and detecting the potential distribution of the grounding grid to confirm the corrosion state of the grounding grid. Firstly, a plurality of magnesium alloy sacrificial anodes are buried under soil and connected with a grounding grid. Then the auxiliary electrode is buried at one end of the grounding grid, the position of the reference electrode is continuously changed to realize potential detection of the grounding grid at different positions, when the grounding grid is corroded to cause failure, the potential of the grounding grid is obviously reduced, the position and corrosion degree of corrosion can be confirmed, and constant potential square wave and constant current square wave experiments can also be carried out on the grounding grid connected with the sacrificial anode. A three-electrode system is adopted in the experiment, a grounding grid is used as a working electrode, a stainless steel electrode is used as an auxiliary electrode, and a saturated copper sulfate electrode is adopted as a reference electrode. The auxiliary electrode is arranged right above one end of the grounding grid, a plurality of reference electrodes are arranged right above the grounding grid at equal intervals, the first reference electrode is positioned on one side of the auxiliary electrode, the rest reference electrodes are distributed in a straight line along the sample, and the interval between every two saturated copper sulfate copper electrodes is equal. And (3) connecting a ZF-100 electrochemical test system with a working electrode, an auxiliary electrode and a reference electrode at the end, respectively carrying out open-circuit potential test, constant-potential square-wave test and constant-current square-wave test, applying constant potentials of 20mV and 200mV to the constant-potential square-wave test for 10 seconds, then applying constant potentials of-20 mV and-200 mV to the constant-potential square-wave test for 10 seconds, circulating for 3 times, and reading corresponding currents. The constant current square wave is applied with the corresponding current for 10 seconds and then the current is turned off for 10 seconds, and the cycle is repeated 3 times. The acquisition interval was 0.2 seconds. And (3) using a ZF-10B data acquisition memory, and respectively connecting 4 channels with the working electrode and the corresponding reference electrode to acquire the electric potentials of different positions of the sample. The working mode of the data acquisition unit is a general voltage acquisition working mode, and the acquisition interval is 0.2 seconds.

Compared with the prior art, the invention has the following beneficial effects: the method comprises the steps of detecting the difference of polarization resistance at different positions, detecting whether local corrosion exists at different positions by using an established method, realizing on-site trenchless detection by calculating current distribution characteristics, establishing an analysis method for detection data, obtaining parameters representing and reflecting corrosion conditions, realizing corrosion prediction, and realizing analysis of potential distribution rules under the condition of protecting a cathode.

The above disclosure is only for the purpose of illustrating the preferred embodiments of the present invention, and it is therefore to be understood that the invention is not limited by the scope of the appended claims.