JPH0247836Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] The invention achieves prevention of various electrical accidents caused by high potential differences between iron pipes connected by insulated joints and interference of cathodic protection at insulated joints. This invention relates to an interference prevention device for an insulated joint.

[Conventional technology]

In general, iron pipes (hereinafter simply referred to as iron pipes) that transport fluids such as gases or liquids are used to prevent corrosion with a small anti-corrosion current, and to prevent abnormal currents caused by lightning strikes or other causes that affect the entire iron pipe line. Insulating joints are inserted in the middle of the iron pipeline to prevent mechanically connected iron pipelines for reasons such as preventing intrusion and applying suitable cathodic protection to specific areas of the iron pipeline. There may be cases where it is necessary to electrically interrupt multiple connections.

When an insulated joint is installed on a steel conduit, if high voltage is induced in a part of the conduit due to a lightning strike or other power accident, the high voltage will be removed from the steel pipe and the insulated joint between the pipe and the insulated joint. There are inconveniences such as sparks caused by electrical discharge, interference (so-called jumping phenomenon) through the soil, and even electric shock accidents for people. Ta.

As a conventional technique for solving this problem in the insulating joints of iron pipelines, there is a
There is a method of providing a protection circuit as shown in Japanese Utility Model Publication No. 60-4996.

The conventional technology shown in Utility Model Publication No. 51-38058 is
As shown in FIG. 3, iron pipes 2 and 3 connected by an insulated joint 1 are connected by a protection circuit 4 in which two diodes D ₁ and D ₂ are connected in antiparallel.
When the potential difference between the iron pipes 2 and 3 is lower than the operating voltage of the diodes D ₁ and D ₂ , electrical insulation is maintained between the iron pipes 2 and 3, and in the event of a lightning strike or the like, the iron pipes 2 and 3 When a high potential difference occurs between both iron pipes 2 and 3, electrical continuity is established between both iron pipes 2 and 3.
3 to a certain value or less to prevent an electrical accident from occurring due to a high potential difference in one part of the insulated joint.

In addition, the conventional technology disclosed in Japanese Utility Model Publication No. 60-4996 is a transistor Tr in which a variable resistor VR is connected between the collector and the base, as shown in Figure 4A.
A parallel circuit with a diode D whose current direction is opposite to that of the transistor Tr is inserted and connected between the iron pipes 2 and 3, or a first variable resistor is connected between the collector and the base as shown in Figure 4 (b). A first transistor Tr ₁ with a variable resistor VR ₁ connected thereto, and a second transistor Tr 1 with a second variable resistor VR ₂ connected between its collector and base, whose current direction is opposite to that of the first transistor Tr ₁ . A parallel circuit with ₂ is inserted and connected between iron pipes 2 and 3, and by adjusting and limiting the current flowing through this protection circuit by the action of a variable resistor connected to a transistor, effective cathodic protection for iron pipe 3 is achieved. Retain your sexuality.

[The problem that the idea aims to solve]

However, in the conventional technology shown in Japanese Utility Model Publication No. 51-38058 and the conventional technology shown in Figure 4A of Japanese Utility Model Publication No. 60-4996, the forward voltage of the diode exceeds 0.7V. Since the diode has a forward voltage/current characteristic in which the current rises rapidly, when the diode becomes conductive, an unlimited current flows between the two iron pipes. As a result, depending on the potential situation of the insulated joints of both iron pipes, a problem arises in that the corrosion protection potential of the iron pipes which have been subjected to cathodic protection cannot be maintained.

In addition, in the conventional technology shown in Figure 4B of Japanese Utility Model Publication No. 60-4996, although it is possible to solve the problem of loss of current limiting ability in the diode, the operating voltage between the two iron pipes is Since it is connected with a transistor as low as 0.45V, even if the passing current is limited by adjusting it with a variable resistor, there is no interference with the non-corrosion-protected iron pipe, but corrosion protection is always maintained, albeit slightly. There is a problem in that the corrosion protection current of the side iron pipe is dispersed to the non-corrosion-protected side iron pipe, and the electric corrosion protection effect of the corrosion-protected side iron pipe is reduced.

In this way, conventional interference prevention technology for insulated joints has been designed to reduce the forward rise voltage, that is, the voltage difference between the two The electrical continuity breaking potential difference between the iron pipes is 0.7V.
or 0.45V, it was not possible to select a rise voltage suitable for each insulating joint, and there was a problem that effective cathodic protection could not be provided.

Therefore, the present invention was devised to solve the above-mentioned problems in the conventional technology. The objective is to prevent corrosion that is forced to occur in iron pipes near insulated joints.

[Means to solve the problem]

The means of the present invention for solving the above-mentioned technical problems are provided between a fluid transport iron pipe connected by an insulating joint, a first diode and a second diode bypassing the first diode. 1 of the first side line, a first transistor with a first variable resistor connected between the collector and base, and 2 of the first side line that bypasses this first transistor. A state where the first diode and the first diode are connected in series, a state where the first diode and the first side line 2 are connected in series, and a state where the first side line 1 and the first transistor are connected in series. It has a first current adjustment circuit connected in series with a first circuit switching terminal that switches between the second diode and the second side line that bypasses the second diode, and between the collector and the base. a second transistor connected to a second variable resistor and a second side line 2 bypassing this second transistor; a state in which the second transistor and a second diode are connected in series; A second circuit switching terminal for switching between a state where the second diode and 2 of the second side line are connected in series, and a state where 1 of the second side line and the second transistor are connected in series. A second current regulating circuit connected in series and having a current direction opposite to that of the first current regulating circuit is provided, and the first current regulating circuit and the second current regulating circuit are connected between both transport iron pipes. Connect in parallel.

[Effect]

The first and second current adjustment circuits that control the electrical connection between the two iron pipes mechanically connected by an insulating joint are a series circuit of a diode and a transistor, a circuit of a single diode, or a circuit of a single transistor. Since you can switch to the configuration,
Select and set the circuit configuration according to the installation situation of the insulation joint.

In other words, if an insulated joint is installed that causes interference with the other iron pipe when the potential difference between the two iron pipes exceeds 0.45V, the first electrical adjustment circuit that flows current from one iron pipe to the other The circuit switching terminal connects the first transistor to one of the first side lines.
It is assumed that the first current adjustment circuit is configured only with the first transistor.

In this case, the current I flowing through the first transistor
and the potential difference V between one iron tube and the other iron tube, by adjusting the resistance value of the first variable resistor, as shown in Fig. 2A, Therefore, by increasing the resistance value of the first variable resistor, it is possible to reduce the rate of increase in the direction of arrow A in FIG. 2A, that is, the rate of increase in current I.

In this way, by increasing or decreasing the first variable resistor,
The current I flowing through the first transistor is adjusted to prevent interference on the other iron pipe side.

In addition, when the potential difference between both iron pipes is about 0.45V, no interference occurs on the other iron pipe side, and the potential difference between both iron pipes is
If an insulated joint is installed where interference occurs on the other iron pipe side at around 0.7V, the first diode and 2 of the first side line, and connect this first current adjustment circuit to the first side line.
diodes.

In this case, the potential difference V between the current I flowing through the first diode and the potential difference V between one iron tube and the other iron tube is 0.7V, as shown in FIG.
Since there is a characteristic that the current I will not pass unless the potential difference V becomes 0.7V or more,
Interference between the other iron pipe can be prevented, and the corrosion protection current (current I) of one iron pipe can be saved to a potential difference of 0.7V, which is the rising voltage of the first diode.

Furthermore, if the electrical potential difference between both iron pipes is around 1.15V and an insulated joint is installed that causes interference with the other iron pipe, the
The first transistor and the first diode are connected by the circuit switching terminal of the current adjustment circuit, and the first current adjustment circuit is constituted by the first transistor and the first diode.

In this case, the current I flowing through the first current adjustment circuit
and the potential difference V between one iron tube and the other iron tube, by adjusting the resistance value of the first variable resistor, as shown in FIG. The rate of increase can be varied, and therefore, by increasing the resistance value of the first variable resistor, the rate of increase in the current I in the direction of arrow A in FIG. 2C can be decreased.

In this way, by increasing or decreasing the first variable resistor,
Adjusting the current I flowing through the first transistor to prevent interference on the other iron pipe side,
The corrosion protection current for one iron pipe can be saved to a potential difference of 1.15V, which is the rising voltage of the first current adjustment circuit.

Note that if the other iron pipe side is the high voltage side and a potential difference occurs between the two iron pipes, the settings of the second current adjustment circuit should be adjusted in the same manner as the setting adjustment for the first current adjustment circuit described above. It works in the same way.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

Reference numeral 5 denotes an insulated joint interference prevention device according to the present invention that is electrically connected between a non-corrosion-protected iron pipe 2 and a corrosion-protected iron pipe 3 connected by an insulated joint 1. , the current direction is iron pipe 3
A first current regulating circuit X whose current direction is directed from the iron pipe 2 to
A bidirectional varistor 8 that protects the first and second current adjustment circuits X and Y from surge voltage, and a short circuit switch SW that unconditionally shorts the iron pipes 2 and 3 are connected in parallel between the iron pipes 2 and 3. It is configured by connecting to.

The first and second current adjustment circuits X and Y each include a silicon diode D, an npn type power transistor Tr in which a variable resistor VR is inserted and connected between the collector C and the base B, and side lines 1 and 2. It is composed of circuit switching terminals 6 and 7 that select and set the connection between two pairs of opposing terminals, and the four terminals that make up the circuit switching terminals 6 and 7 are a terminal connected to the cathode of diode D, and a transistor The terminal connected to the collector C of the Tr, the terminal 1 of the side line opposite to the terminal connected to the anode of the diode D, and the side line opposite to the terminal connected to the emitter E of the transistor Tr. There are 2 terminals and 4 terminals.

When the circuit switching terminal 6 or 7 is set to connect the cathode of the diode D and the collector of the transistor Tr, the current adjustment circuit X or Y
is a series circuit of diode D and transistor Tr, and if the circuit switching terminal 6 or 7 is set to connect the cathode of diode D and side line 2, the current adjustment circuit X or Y will only connect diode D. If the circuit switching terminal 6 or 7 is set to connect the side line 1 and the collector C of the transistor Tr, the current adjustment circuit X or Y will be composed only of the transistor Tr. It turns out.

Note that when the short circuit switch SW is turned on to short-circuit iron pipes 2 and 3, both iron pipes 2 and 3
It can be seen how much current flows between the two, that is, the short circuit current. The current/voltage characteristics when the iron pipes 2 and 3 are short-circuited by the short-circuit switch SW are as shown by the broken lines in Fig. 2, A, B, and C.

Therefore, since it is possible to compare the short circuit current and the current in each configuration, it is possible to determine how much corrosion protection current can be saved.

In order to obtain the current/voltage characteristics at the time of a short circuit by shorting the short circuit switch SW and causing a short circuit current to flow, it is necessary to insert a shunt resistor r for measurement.

First current adjustment circuit X and second current adjustment circuit Y
The connection form at the circuit switching terminals 6 and 7,
and the first variable resistor VR ₁ and the second variable resistor
The set resistance value of VR ₂ is not necessarily the same, and depends on the presence or absence of cathodic protection for iron pipe 2 or 3, iron pipe 2,
It is determined according to the burial condition of No. 3.

[Effect of idea]

Since the present invention has the above-described configuration, it has the following effects.

The circuit configuration can be set to suit the installation status of the insulated joint of both iron pipes connected by an insulated joint and the cathodic protection conditions, so that an unlimited current flows between the two iron pipes and the corrosion-protected side iron pipe To reliably prevent the occurrence of inconveniences such as failure to maintain the anticorrosion potential of the iron pipe on the non-corrosion-protected side or dispersion of the anti-corrosion current in the iron pipe on the non-corrosion-protected side to the iron pipe on the non-corrosion-protected side even though there is no interference with the iron pipe on the non-corrosion-protected side. This makes it possible to achieve and maintain reliable and stable cathodic protection of the corrosion-protected side iron pipe.

Since the circuit configuration of the current adjustment circuit can be selected and set according to the potential difference that occurs between the corrosion-protected side iron pipe and the non-corrosion-protected side iron pipe, the anti-corrosion current can be saved and efficient cathodic protection of the iron pipe can be carried out. can do.

For insulated joints of iron pipes that have different buried conditions and cathodic protection conditions, the circuit configuration of the current adjustment circuit can be suitably adapted to the buried conditions and cathodic protection conditions by simple selection and connection at the circuit switching terminal. This makes it possible to easily and appropriately set the circuit configuration of the current adjustment circuit at the work site.

[Brief explanation of the drawing]

FIG. 1 is an electrical circuit diagram showing an embodiment of an insulating joint interference prevention device according to the present invention. Figure 2 A is a characteristic diagram showing the current/voltage characteristics of a current adjustment circuit consisting only of transistors with a variable resistor connected between the collector and base. A characteristic diagram showing the current/voltage characteristics of the adjustment circuit, Figure 2C shows the collector/voltage characteristics.
FIG. 2 is a characteristic diagram showing the current/voltage characteristics of a current adjustment circuit configured by connecting a transistor with a variable resistor connected between its bases and a diode in series. FIG. 3 is an electrical circuit diagram showing a first prior art insulated joint interference prevention device. Fig. 4 is an electric circuit diagram showing a second conventional technique of an insulated joint interference prevention device, in which Fig. 4A shows the first embodiment thereof, and Fig. 4B shows the second embodiment thereof. It is. Explanation of symbols, 1; Insulated joint, 2, 3; Iron pipe,
4, 5; Insulation joint interference prevention device, 6, 7; Circuit switching terminal, 8; Varistor, 9, 10; Side line,
X, Y: Current adjustment circuit, D: Diode, Tr;
Transistor, VR; variable resistor, SW; short circuit switch, r; shunt resistor.

Claims (1)

[Claims for Utility Model Registration] In fluid transport iron pipes 2 and 3 connected by an insulating joint 1, a first diode D ₁ and a first diode D ₁
1 (9-1) of the first side line bypassing the circuit, the first transistor Tr 1 having the first variable resistor VR ₁ connected between the collector and the base, and the first transistor Tr ₁ .
2 (9-2) of the first side route that bypasses Tr ₁ ,
the first transistor Tr ₁ and the first diode
D ₁ is connected in series, the first diode D ₁ and 2 (9-2) of the first side line are connected in series, and the first diode D 1 and 2 (9-2) of the first side line are connected in series;
1) and the first transistor Tr ₁ connected in series at the first circuit switching terminal 6, the second diode D ₂ and the first current regulating circuit X connected in series at the first circuit switching terminal 6. 2 diode D ₂
1 (10-1) of the second side line to be bypassed, and the second transistor Tr ₂ with the second variable resistor VR ₂ connected between the collector and base, and the second transistor Tr ₂ to be bypassed. 2 (10-2) of the second side line, the second transistor Tr ₂ and the second diode D ₂ are connected in series, and the second diode D ₂ and the second side line are connected in series. 2 (10-2) in series, and 1 of the second side route.
(10-1) and the second transistor Tr ₂ are connected in series.The current direction is opposite to that of the first current adjustment circuit X, which is connected in series at the second circuit switching terminal 7. a second current regulation circuit Y, and an insulated joint portion comprising: the first current regulation circuit Anti-interference device.