JPH057241Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a cathodic protection device used for corrosion protection of fluid transport steel pipes buried in the ground.

[Conventional technology] Conventional electrolytic protection equipment uses a transformer to step down the commercial power supply to around 15V, then perform full-wave rectification, and then bury the anode of the DC power supply in the ground so that it is completely grounded. Connect the negative electrode to the steel pipe buried in the soil (hereinafter referred to as the pipe to be protected), and connect the reference electrode at a position slightly away (for example, about 10 cm) from the pipe to be protected. The potential between the corrosion-protected pipe connected to the negative electrode and the reference electrode (hereinafter referred to as reference potential) is compared with a predetermined potential set in advance, and the amount exceeding the predetermined potential is determined. generates a control signal proportional to , and when this control signal is large, controls the output so as to increase the output current, adjusts the current between the corrosion-protected pipe and the corrosion-protection electrode, and performs the verification described above. The potential was maintained below a predetermined potential to prevent electrical corrosion caused by stray currents in the soil.

A thyristor or the like is used to control the output of the conventional cathodic protection device, and the output current is controlled by changing the conduction angle of the thyristor using a trigger pulse whose generated phase position changes according to the control signal. A current having a waveform as shown in FIG. 4 was output from the anode.

FIG. 4 is a diagram showing output control of a conventional cathodic protection device. In the figure, the horizontal axis shows time, the upper row shows the output current, the middle row shows the position of the trigger pulse, and the lower row shows the magnitude of the control signal (voltage). The upper dashed line shows the full-wave rectified waveform, and the shaded part shows the output current.

[Problem to be solved by the invention] The conventional cathodic protection device described above is configured as described above, and its output current has a waveform as shown in FIG. 4, and the frequency is 100Hz or 120Hz.
The amount of output current is not completely proportional to the control signal.

FIG. 5 is a diagram showing the response performance of a conventional cathodic protection device. In the figure, the horizontal axis represents time, and the vertical axis represents reference potential and output current, with the upper graph showing changes in output current, and the lower graph showing stepwise changes in reference potential. As shown in the figure, the response time for conventional cathodic protection equipment is 52.5ms.
It was a long one. Therefore, only an incomplete corrosion protection effect can be obtained not only against rapidly fluctuating stray currents but also against slow fluctuations, and since a transformer compatible with the frequency of the product power supply is used, it is large and difficult to manufacture. The problem was that the cost was also high.

This invention was devised in order to solve these problems, and the purpose was to obtain a cathodic protection device that has good response performance, can perform cathodic protection reliably, is compact, and can reduce manufacturing costs. shall be.

[Means for Solving the Problems] The cathodic protection device according to this invention uses a switching regulated DC power source as its power source, and has a configuration in which the switching is controlled by the reference potential, and the output is controlled. This is what I did.

[Function] In the electrolytic protection device of this invention, the switching of the switching regulated DC power supply is controlled by the above-mentioned reference potential, so it has an extremely quick response performance and the current flowing through the transformer becomes a high-speed wave. Therefore, the transformer can be made smaller.

[Example] FIG. 1 is a block diagram showing a cathodic protection device that is an example of this invention.

In the figure, 13 is a power supply device of the cathodic protection device of this invention, 1 is a corrosion-protected pipe such as a steel pipe connected to the output side cathode 15 of the power supply device 13 and buried in the soil;
2 is a reference electrode made of magnesium, etc., and is buried near the corrosion-protected pipe 1 (for example, about 10 cm) and connected to the reference terminal 16 of the power supply 13; 3 is connected to the output anode 14 of the power supply 13 and is deep underground. Anti-corrosion electrode buried and completely grounded, 4
5 is an error amplifier that amplifies the difference between the reference potential and the reference potential generated by the reference potential generation circuit 4; 6 is the output of the error amplifier 5; A pulse conversion circuit 7 generates a continuous pulse whose pulse width is modulated by a certain control signal.
An oscillator that sends out a reference wave of ~40KHz, 8 a photocoupler consisting of a light emitting element and a light receiving element and installed to electrically isolate input and output, 9 a drive circuit for the switching transistor Q1, and 10 a commercial power supply. , 11 is a full-wave rectifier circuit with diodes connected in a bridge configuration, 12 is a smoothing circuit consisting of a choke coil L and a capacitor C2, 17 is an input terminal of the power supply 13, C1 is a smoothing capacitor, D
1 and D2 are high-speed switching diodes, and T is a transformer for stepping down the voltage from the commercial power supply voltage to, for example, 15 to 20V.

Next, the operation of the cathodic protection device shown in FIG. 1 will be explained.

FIG. 2 is a diagram showing output control of the cathodic protection device shown in FIG. 1. In the figure, the horizontal axis shows time, the upper row shows the current flowing through the primary side of the transformer T, and the lower row shows the magnitude of the control signal (voltage).

The alternating current of the commercial power supply 10 is full-wave rectified by the full-wave rectifier circuit 11 to become direct current, smoothed by the capacitor C1, and supplied to the primary side of the transformer T.
This primary side input is the switching transistor Q1
It is turned on and off by. The switching transistor Q1 is turned on and off as follows.

The reference potential with respect to the corrosion-protected pipe 1 obtained by the reference electrode 2 is compared with the reference potential generated by the reference potential generation circuit 4 by the error amplifier 5, and a control signal proportional to the amount exceeding the reference potential is generated. is sent to the pulse conversion circuit 6. The reference potential is set to a value slightly lower than 650 mV when the reference electrode 2 is made of magnesium. This means that the reference potential above is
If the voltage is maintained below 650mV, galvanic corrosion will be prevented, so there is some safety in mind.

The pulse conversion circuit 6 is oscillated by the oscillator 7.
A pulse signal having a frequency of 20 to 40 KHz and a duty ratio proportional to the magnitude of the control signal is sent to the photocoupler 8. This pulse signal reaches the drive circuit 9 via the photocoupler 8, and the drive circuit 9 turns on/off the switching transistor Q1 according to this pulse signal. Therefore, as shown in FIG. 2, pulsed currents with different duty ratios depending on the magnitude of the control signal flow through the primary side of the transformer T. On the secondary side of the transformer T, the secondary current stepped down at a preset step-down ratio is rectified and smoothed by high-speed switching diodes D1 and D2 and the smoothing circuit 12, and becomes the output of the power supply device 13. It is supplied to the anti-corrosion electrode 3.

Since the anti-corrosion current controlled by the high-speed switching method is supplied to the anti-corrosion electrode 3 as described above, its response speed is extremely high.

FIG. 3 is a diagram showing the response performance of the cathodic protection device shown in FIG. 1. In the figure, the horizontal axis shows time, and the vertical axis shows the reference potential and output current values.
The upper graph shows changes in output current, and the lower graph shows changes in reference potential. As shown in this figure, the response time to a step change in the reference potential, which is the same as that in FIG. 5, was only 9.5 ms.

Although the embodiment using the pulse conversion circuit 6 of the pulse width control method has been described above, it is also possible to use the pulse conversion circuit 6 of the pulse width fixed frequency control method, the pulse width frequency control method, the pulse number control method, etc. Needless to say. Also, the smoothing circuit 12
Even if this is abolished and an unsmoothed output is supplied to the anti-corrosion electrode 3, the effect of preventing electrical corrosion can be achieved.

[Effects of the invention] As explained above, this invention uses a switching regulator type DC power source as the power source for the cathodic protection equipment, and the error amplifier that sends the control signal to the pulse conversion circuit has a reference potential and a reference potential. Since the output is controlled by the above-mentioned reference potential, it is possible to obtain an output that responds extremely quickly to changes in the reference potential, and it is not susceptible to stray currents that change rapidly. It is possible to obtain a highly complete cathodic protection device that can completely prevent galvanic corrosion of anticorrosion pipes, and because it performs high-speed switching, the transformer can be made smaller and manufacturing costs can be reduced. It has excellent effects.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a cathodic protection device that is an embodiment of this invention, Fig. 2 is a diagram showing output control of the cathodic protection device shown in Fig. 1, and Fig. 3 is a diagram showing the cathodic protection device shown in Fig. 1. FIG. 4 is a diagram showing the response performance of the device. FIG. 4 is a diagram showing the output control of the conventional cathodic protection device. FIG. 5 is a diagram showing the response performance of the conventional cathodic protection device. In the figure, 1... Pipe to be corrosion protected, 2... Reference electrode, 3... Corrosion protection electrode, 4... Reference potential generation circuit, 5... Error amplifier, 6... Pulse conversion circuit,
7... Oscillator, 8... Photocoupler, 9... Drive circuit, 10... Commercial power supply, 11... Full wave rectifier circuit,
12...Smoothing circuit, 13...Power supply device, 14...
Output side anode, 15...Output side cathode, 16...Verification terminal, 17...Input terminal, C1...Capacitor,
D1, D2...High speed switching diode, T
...Transformer, Q1...Switching transistor.

Claims (1)

[Scope of utility model registration request] A cathodic protection device used for corrosion protection of steel pipes buried in the ground uses a switching, regulated DC power source as its power source, with a corrosion protection electrode on the output anode and a covered cathode on the output side. One input terminal and the output side of an error amplifier provided to connect the steel pipe that is a corrosion protection body and send a control signal to a pulse conversion circuit that generates pulses for controlling switching of the power source. An electrolytic protection device characterized in that a reference potential generation circuit is interposed between the cathode and the cathode, and a reference electrode buried near the object to be protected is connected to the other input terminal.