JP2591974B2 - Insulation resistance measurement method for buried pipeline insulated joints - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring the insulation resistance of an insulating joint connected in the middle of a metal pipeline.

[Prior Art] Generally, a pipe insulation joint is inserted between non-corrosion-proof metal pipes to insulate each other in order to apply cathodic protection to a limited area of the buried metal pipe, or to bury a buried metal pipe. Is exposed to a different environment, which causes macrocell corrosion. Therefore, it is used for the purpose of cutting off a corrosion circuit by being inserted between an environment serving as an anode and an environment serving as a cathode.

Therefore, maintaining and managing the insulation performance of the insulated joint is extremely important for effective operation of cathodic protection and prevention of corrosion of the metal pipe.

As a method for maintaining and managing the insulated joint, the gas pipe anticorrosion handbook (page 58 (d) Inspection method for the insulated joint) was used to determine whether two metal pipes sandwiching the insulated joint as shown in FIG. 3 or FIG. There is a method of measuring a potential difference, which is a difference between average ground potentials.

The method shown in FIG.
And 2 are connected to a potentiometer 12, and the potential difference, which is the difference between the average ground potentials of the two metal tubes 1 and 2, is measured. When an effective potential difference is obtained, the insulation effect is evaluated as good.

In addition, the method shown in FIG. 4 is a method in which when the potential difference shows a value close to 0 measured by the method shown in FIG. In this measuring method, a DC voltage E ₀ is applied from a power supply 13 between one of the metal tubes 1 and the ground electrode 5, and a difference in a change in ground potential of each of the metal tubes is measured through a current. This inspection method determines that the insulating joint 3 is in a conductive state when the insulation effect is good when obtained and the potential difference shows a value close to 0.

[Problems to be Solved by the Invention] However, this method has the following problems, and the performance of the insulating joint 3 cannot be accurately evaluated.

First, the problem with the method of FIG.
2 may apply the cathodic protection to each other, and if the anticorrosion currents flowing through the respective metal pipes are equal, or if they are buried in the same soil environment and have the same ground potential, the potential difference at this time depends on the insulation performance of the insulating joint 3. Is 0 regardless of.

 Next, problems in the method of FIG. 4 will be described.

FIG. 5 shows the applied voltage in the measuring circuit in FIG.
E ₀ , ground resistance r ₃ of the ground electrode 5, leakage resistance of the first metal tube 1
This represents an equivalent circuit in which r ₁ , the leakage resistance r _{2 of} the second metal tube 2, and the insulation resistance r ₄ of the insulating joint 3. Here, assuming that the current flowing through the leak resistance r ₁ is I ₁ and the current I ₂ flows through the insulation resistance r ₄ and the leak resistance r ₂ , the relationship between the potential and the current is expressed as follows.

Here, the leak resistance is the sum of the coating resistance of the metal pipe and the resistance in the soil around the metal pipe, and refers to the ground resistance of the metal pipe to the ground.

E ₀ = r ₃ (I ₁ + I ₂ ) + r ₁ I ₁ = r ₃ (I ₁ + I ₂ ) + (r ₂ + r ₄ ) I ₂ (V) (1) From equation (1), r ₁ I ₁ = (r ₂ + r ₄ ) I ₂ (V) (2) On both sides of the equation (2), Multiplied by the following equation.

Further, equation (3) can be expressed as follows.

From equation (4), the potential r ₄ I ₂ at both ends of the insulating joint 3 is obtained by calculating the ratio of the insulating resistance r ₄ of the insulating joint to the leakage resistance r ₂ of the second metal tube 2 and the ground of the first metal tube 1. It is determined by the potential r ₁ I ₁ and does not become higher than this ground potential r ₁ I ₁ .

That Evaluation of insulating joint 3 according to this method, the insulation resistance r ₄ of the insulating joint 3 against leakage resistance r ₂ of the second metal tube 2
Is a relative method that it is sufficient if the potential r ₄ I ₂ at both ends of the insulating joint 3 is close to the ground potential of the first metal tube 1.

However, according to this method, the insulation resistance r ₄ of the insulating joint 3, when the leakage resistance r ₂ of the second metal tube 2 is small, it means may insulating joint r ₄ is small, the second metal tube 2 Insulation performance may not be evaluated correctly depending on the value of the leakage resistance r ₂ of.

The present invention provides an insulation resistance measuring method capable of solving the above problems and accurately knowing the performance of an insulated joint.

[Means for Solving the Problems] The gist of the present invention is to provide an insulation joint 3 having an insulation resistance r ₄ of a pipe to be measured, and a first metal pipe 1 having a leakage resistance r ₁ connected to the insulation joint 3. in the metal pipe made of the second metal tube 2 the leakage resistance r _2, the resistance r _v variable end of the resistor 4 is connected to a first metal tube 1, the ground resistance r ₃ becomes ground electrode and the other end of 5, a power source 6 is connected between the second metal tube 2 and the ground electrode 5, and the other ends of the first metal tube 1, the second metal tube 2 and the variable resistor 4. A bridge circuit in which voltmeters E ₁ , E _2, and E ₃ are respectively connected between the side and the ground reference electrode 8 is formed, and then the signal voltage E ₀ is applied from the power source 6 and the variable resistor 4 insulation resistance measurement of the resistance r _v from the adjustment to obtain equilibrium conditions of a buried pipe insulation joint and obtains the insulation resistance r ₄ of the insulating joint 3 Located in.

Bridge circuit [work for] Figure 1 is to increase or decrease the resistance r _v of the variable resistor, the following equation is obtained from the equilibrium condition a potential E ₁ at both ends of the resistor r ₁ is 0 (V).

r ₄ × r ₃ = r ₂ × r _v …… (5) Also from the equilibrium condition of the bridge circuit, all current I ₃ flowing through the resistor r ₃ flows resistor r _2, (7) and (8) the relationship of Formula obtained.

E ₃ = r ₃ × I ₃ (V), E ₂ = r ₂ × I ₃ (V) ... (7) Further, by substituting equation (8) into equation (6), the resistance
The following equation for r ₄ is obtained.

That is, when the bridge circuit is balanced, the ground and the second
Of the potential difference E ₂ of the metal pipe 2, and requests the insulation resistance value r ₄ by measuring the value of the resistance value r _v at equilibrium potential difference E ₃ and the bridge circuit between the earth and the earth electrode.

Next, an embodiment of the present invention will be described in detail with reference to FIG.

FIG. 2 shows the configuration of this measuring method. A variable resistor 4 is connected to a metal pipe having an insulating joint 3 to be measured between a first metal pipe 1 and a second metal pipe 2. One end is connected to the first metal tube 1 and the other end is connected to a ground electrode 5 having a ground resistance r ₃ , and then a power source 6 is connected between the second metal tube 2 and the ground electrode 5. Potentiometers 9, 10, and 11 are connected between the reference electrode 8 inserted into the soil, the first metal tube 1, the second metal tube 2, and the ground electrode.

In FIG. 2, the leak resistance of the first metal pipe 1 is r ₁ , the leak resistance of the second metal pipe 2 is r ₂ , and the insulation resistance of the insulating joint 3 is
r ₄ , the ground resistance of the ground electrode 5 is r ₃ , and the resistance of the variable resistor 4 is
r _v , the signal voltage output from the power supply 6 is E ₀ , the current flowing through the ground electrode 5 is I ₃ , the potential difference indicated by the potentiometer 9 connected between the reference electrode 8 and the first metal tube 1 is E ₁ , The potential difference indicated by the potentiometer 10 connected between the reference electrode 8 and the second metal tube 2 is
E _2, if reference electrode 8 and E ₃ the potential to direct a potentiometer 11 connected between a ground electrode 5, these developed view is the same as the bridge circuit shown in Figure 1.

If so now predetermine relationship adjusting dial and the resistance r _v of the variable resistor, and adjusting the adjustment dial, the potentiometer 9 equilibrium potential E ₁ becomes 0 (v), the second metal tube 2, and, ground potential E ₂ of the ground electrode 5, and, from the measured values of E _3, it is possible to easily determine the insulation resistance r ₄ of the insulating joint 3 using (9).

In this measuring method, the output signal of the power source 6 may be any one of AC and DC, and the potentials E ₁ , E ₂ and E ₃ are the amounts of change in the ground potential when a signal current is passed.

[Effect of the Invention] According to the measuring method of the present invention, one end of a variable resistor is connected to a metal pipe having an insulating joint to be measured between a first metal pipe and a second metal pipe. And the other end is connected to the ground electrode, then the power supply is connected between the second metal tube and the ground electrode, and furthermore, the reference electrode and the first metal tube inserted in the soil, A potentiometer is connected between the two metal tubes and the ground electrode to form a bridge circuit, and the potential difference between the ground and the second metal tube obtained when the circuit is balanced, and the difference between the ground and the ground electrode. The insulation resistance value of the insulation joint is obtained from the potential difference and the value of the resistance ground which balances the bridge circuit. Even if the two metal tubes which are problematic in the prior art method shown in FIG. Also, the leakage resistance of the second metal tube, which is a problem in the method shown in FIG. At least, the performance of the insulated joint can be accurately evaluated without being affected by these.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a basic principle of the present invention, FIG. 2 is a circuit diagram showing a configuration of an inspection method according to an embodiment of the present invention, and FIGS. 3 and 4 are diagrams of a conventionally proposed insulated joint. FIG. 5 is an equivalent circuit diagram of FIG. 1,2 ... metal tube, 3 ... insulation joint, 4 ... variable resistor,
5 ... ground electrode, 6,13 ... power supply, 8 ... reference electrode, 9,10,1
1,12 ... potentiometer

Claims (1)

(57) [Claims] 1. A dielectric joint 3 will to pipe insulation resistance r ₄ of being measured, the first metal tube 1 of the leakage resistance r ₁ that connects to the insulating joint 3, the leakage resistance r second metal tube 2 of ₂ In one embodiment, one end of a variable resistor 4 having a resistance r _v is connected to a first metal tube 1.
, The other end is connected to a ground electrode 5 having a ground resistance r _3, and a power source 6 is connected between the second metal tube 2 and the ground electrode 5. A bridge circuit in which voltmeters E ₁ , E ₂ and E ₃ are respectively connected between the other end of the second metal tube 2 and the variable resistor 4 and the ground reference electrode 8;
Then, after applying signal voltage E ₀ from the power source 6, buried duct, wherein the equilibrium condition obtained by adjusting the resistance r _v of the variable resistor 4 to determine the insulation resistance r ₄ of the insulating joint 3 Insulation resistance measurement method for insulated joints.