PROTECTION SYSTEM FOR PIPELINES

Abstract

A protection system (10) for pipes (12) comprises a cathodic corrosion protection system (18) which comprises a rectifier (22) and a corrosion protection switching element (24) which is electrically conductively connected to the rectifier (22), wherein the cathodic corrosion protection system (18) is set up to switch between a corrosion protection mode and a measuring mode, wherein the rectifier (22) is not connected in the measuring mode. The protection system (10) also includes a decoupler (18) which comprises a first capacitor (28) and a second capacitor (30) and a capacitor switching element (32). The capacitor switching element (32) is electrically conductively connected to the first capacitor (28) in a first switch position when the cathodic corrosion protection system (18) is in the corrosion protection mode. In a second switch position, the capacitor switching element (32) is electrically conductively connected to the second capacitor (30) when the cathodic corrosion protection system (18) is in the measuring mode.

Furthermore, the use of such a protection system is specified.

Claims

1. A protection system (10) for pipes (12), comprising a cathodic corrosion protection system (18) which comprises a rectifier (22) and a corrosion protection switching element (24) which is electrically conductively connected to the rectifier (22), wherein the cathodic corrosion protection system (18) is set up to switch between a corrosion protection mode and a measuring mode, wherein the rectifier (22) is not connected in the measuring mode, and a decoupler (20) which comprises a first capacitor (28) and a second capacitor (30) and a capacitor switching element (32), wherein the capacitor switching element (32) is electrically conductively connected to the first capacitor (28) in a first switch position when the cathodic corrosion protection system (18) is in the corrosion protection mode, and wherein the capacitor switching element (32) is electrically conductively connected to the second capacitor (30) in a second switch position when the cathodic corrosion protection system (18) is in the measuring mode.

2. The protection system according to claim 1, wherein the pipe (12) is a metallic pipe having a coating (14) of an insulating material.

3. The protection system according to claim 1, wherein the capacitor switching element (32) is a power semiconductor switch.

4. The protection system according to claim 1, wherein the protection system (10) is set up to charge the first capacitor (28) to a switch-on potential and to charge the second capacitor (30) to a switch-off potential in a training phase of the protection system (10), and wherein the switch-on potential corresponds to the potential of the pipe (12) to be protected in the corrosion protection mode and the switch-off potential of the second capacitor corresponds to the potential of the pipe (12) to be protected in the measuring mode.

5. The protection system according to claim 4, wherein the switch-on potential is more negative than the switch-off potential.

6. The protection system according to claim 1, wherein the first capacitor (28) and/or the second capacitor (30) has/have a capacitance in the range of 0.1 to 1.0 F.

7. The protection system according to claim 1, wherein the decoupler (20) has a grounding device (34) which is electrically conductively connected to the first capacitor (28) and the second capacitor (30).

8. The protection system according to claim 1, wherein a clipping diode (56) is connected in parallel with the second capacitor (30).

9. The protection system according to claim 1, wherein the cathodic corrosion protection system (18) and the decoupler (20) have switching control elements (60, 62) which are time-synchronized.

10. Use of the protection system (10) according to claim 1 for protecting a pipe (12), wherein the corrosion protection switching element (24) and the capacitor switching element (32) are connected to the pipe (12).

Description

[0051] Further features and characteristics of the invention will become apparent from the description below of exemplary embodiments, which are not to be understood in a restrictive sense, and from the drawings, in which:

[0052] FIG. 1 shows a first embodiment of a protection system for pipes according to the invention in a first operating mode,

[0053] FIG. 2 shows the protection system of FIG. 1 in a second operating mode,

[0054] FIG. 3 shows the protection system of FIG. 1 in a first step of a training phase,

[0055] FIG. 4 shows the protection system of FIG. 1 in a second step of a training phase,

[0056] FIG. 5 shows a second embodiment of the protection system for pipes according to the invention in the second operating mode, and

[0057] FIG. 6 shows a third embodiment of the protection system for pipes according to the invention in the first operating mode.

[0058] FIG. 1 schematically shows a protection system 10 according to the invention for a pipe 12.

[0059] The pipe 12 is a metallic pipe made of stainless steel and having a coating 14 made of an insulating material.

[0060] It is understood that the pipe 12 may also be made of other materials, in particular other metals, as known from the prior art.

[0061] The pipe 12 is buried, for example, i.e. it is laid in the ground below the surface of the earth (not shown) and is thus in contact with the surrounding soil.

[0062] In the embodiment shown, the coating 14 has a defective spot 16, i.e. a damage. At the defective spot 16, the metal surface of the pipe 12 is in direct contact with the surrounding soil, so that the pipe 12 has an increased tendency to corrode at this point.

[0063] In addition, the pipe 12 is located near a high-voltage line system (not shown), which causes an AC voltage in the pipe 12.

[0064] The protection system 10 has a cathodic corrosion protection system 18 and a decoupler 20, the functions of which will be described in more detail below.

[0065] The corrosion protection system 18 includes a rectifier 22, a corrosion protection switching element 24, which in FIG. 1 connects the pipe 12 in an electrically conductive manner to the rectifier 22, and an anode 26 electrically conductively connected to the rectifier 22.

[0066] The rectifier 22 is connected to a voltage source (not shown) which supplies the rectifier 22 with energy.

[0067] The decoupler 20 has a first capacitor 28, also referred to as main capacitor, and a second capacitor 30, also referred to as measuring capacitor.

[0068] The first capacitor 28 and/or the second capacitor 30 has/have a capacitance in the range of 0.1 to 1.0 F, the capacitance of the first capacitor 28 being in particular higher than the capacitance of the second capacitor 30.

[0069] In addition, the decoupler 20 has a capacitor switching element 32 which is electrically conductively connected to the pipe 12.

[0070] In FIG. 1, the capacitor switching element 32 is shown in a first switch position, in which the capacitor switching element 32 is electrically conductively connected to the first capacitor 28.

[0071] The decoupler 20 also includes a grounding device 34.

[0072] The grounding device 34 is electrically conductively connected both to the first capacitor 28 and to the second capacitor 30.

[0073] The pipe 12 is also electrically conductively connected to a voltage measuring system 36.

[0074] The voltage measuring system 36 includes a voltmeter 38 and a reference electrode 40.

[0075] The voltage measuring system 36 can be a component of the protection system 10 according to the invention or can form a separate component. Basically, it is also conceivable that the voltage measuring system 36 is integrated into the cathodic corrosion protection system 18 or the decoupler 20.

[0076] FIG. 1 shows the protection system 10 according to the invention in a first operating mode, in which the corrosion protection switching element 24 is electrically conductively connected to the rectifier 22, i.e. the cathodic corrosion protection system 18 is in a so-called corrosion protection mode and the capacitor switching element 32 is in a first switch position in which the capacitor switching element 32 is electrically conductively connected to the first capacitor 28.

[0077] FIG. 2 shows the protection system 10 according to the invention in a second operating mode, in which the corrosion protection switching element 24 is not connected to the rectifier 22, so that the cathodic corrosion protection system 18 is in a so-called measuring mode and the capacitor switching element 32 is in a second switch position in which the capacitor switching element 32 is electrically conductively connected to the second capacitor 30.

[0078] The corrosion protection switching element 24 and the capacitor switching element 32 are synchronized or coupled to each other, as indicated by the dashed line 42 in FIG. 1 and FIG. 2. For example, the corrosion protection switching element 24 and the capacitor switching element 32 are designed as change-over switches. This means that the capacitor switching element 32 is in the first switch position when the corrosion protection switching element 24 connects the rectifier 22 in an electrically conductive manner to the pipe 12, and the capacitor switching element 32 is in the second switch position when the corrosion protection switching element 24 does not switch on the rectifier 22, i.e. does not connect it to the pipe 12.

[0079] However, the corrosion protection switching element 24 and the capacitor switching element 32 are preferably separate switches which are synchronized or coupled to each other.

[0080] The capacitor switching element 32 is in particular a power semiconductor switch to achieve the shortest possible switching time.

[0081] In the following, the mode of operation of the protection system 10 according to the invention is described in more detail, i.e. the use of the protection system 10 for protecting the pipe 12 and a method of protecting the pipe 12.

[0082] First, the cathodic corrosion protection system 18 and the decoupler 20 are coupled to the pipe 12 to be protected by connecting the corrosion protection switching element 24 and the capacitor switching element 32 in an electrically conductive manner to the pipe 12.

[0083] During its period of use or service life, the pipe 12 is exposed to various influences which can lead to corrosion and thus to damage to the pipe 12. In particular, at the defective spot 16, where the coating 14 is damaged and the metal surface of the pipe 12 comes into direct contact with the surrounding soil, there is a high tendency to corrosion, resulting in a so-called corrosion current.

[0084] To counteract this corrosion current, the cathodic corrosion protection system 18 generates a cathodic protection potential in the corrosion protection mode, which results in a protection current between the anode 26 and the pipe 12, indicated in FIG. 1 by a dotted arrow 44.

[0085] As long as the cathodic protection potential is sufficiently high, for example, a minimum protection potential of 850 mV or less is generated, corrosion of the pipe 12 at the defective spot 16 is reliably prevented.

[0086] As can be seen in FIG. 1, the capacitor switching element 32 is connected to the first capacitor 28 in the corrosion protection mode of the cathodic corrosion protection system 18.

[0087] In this way, AC voltages induced in the pipe 12, for example due to the nearby (not shown) high-current line system, are dissipated via the first capacitor 28 to the grounding device 34, thus reducing the effective AC voltage on the pipe 12.

[0088] Due to the fact that at the same time the cathodic corrosion protection system 18 generates a protection current, a charging current also flows from the pipe 12 to the first capacitor 28 in the first operating mode of the protection system 10, in which the capacitor switching element 32 is in its first switch position, as indicated by a dotted arrow 46 in FIG. 1, until the first capacitor 28 has charged to the same potential as the pipe 12.

[0089] In addition, a switch-on potential, indicated by a double arrow 48 in FIG. 1, occurs between the grounding device 34 and the pipe 12.

[0090] To ensure that the minimum protection potential is guaranteed, i.e. that the cathodic protection potential is sufficiently high to prevent corrosion of the pipe 12, the potential of the pipe 12 to be protected is measured by means of the voltage measuring system 36.

[0091] In particular, the measurement of the potential of the pipe 12 to be protected is repeated at regular intervals by means of the voltage measuring system 36.

[0092] In FIG. 1, a double arrow 50 indicates that the voltage measuring system 36 can only determine the potential respectively present between the pipe 12, in particular at the relevant defective spot 16, and the reference electrode 40.

[0093] However, this value is influenced by the cathodic protection potential of the cathodic corrosion protection system 18 and possible further sources of error such as nearby external protection current systems, equalizing currents, element currents, currents from DC-operated industrial and railway systems and/or earth currents.

[0094] To nevertheless enable a reliable measurement of the potential of the pipe 12 to be protected, the measurement is carried out by the voltage measuring system 36 as a measurement pair, the measurement pair comprising a first measurement which is carried out with the rectifier 22 connected, i.e. while the cathodic corrosion protection system 18 is in the corrosion protection mode (as shown in FIG. 1) and a second measurement, which is carried out with the rectifier 22 not connected, i.e. while the cathodic corrosion protection system 18 is in the measuring mode (as shown in FIG. 2).

[0095] The actual potential of the pipe 12 to be protected is then determined, for example, as the difference between the first measurement and the second measurement, the respective signs of the measured voltage value being taken into account accordingly when calculating the difference.

[0096] If it can be assumed that no further sources of interference are present, it is then possible, as an alternative to determining the cathodic protection potential, to carry out a single measurement with the rectifier 22 not connected, similar to the second measurement.

[0097] To prevent the second measurement from being distorted by the first capacitor 28 discharging, which was previously charged due to the charging current in the first operating mode of the protection system 10, thus to prevent a direct current from being generated between the reference electrode 34 and the pipe 12, the capacitor switching element 32 switches to the second switch position, in which the second capacitor 30 is electrically conductively connected to the pipe 12 instead of the first capacitor 28, in synchronism with the change of the cathodic corrosion protection system 18 to the measuring mode (see FIG. 2).

[0098] Thus, a charging current flows between the pipe 12 and the second capacitor 30 (indicated by a dotted arrow 52 in FIG. 2) only until the second capacitor 30 is charged to the potential of the pipe 12 with the cathodic corrosion protection system 18 deactivated.

[0099] This results in a switch-off potential between the grounding device 34 and the pipe 12, which is indicated by a double arrow 54 in FIG. 1.

[0100] The switch-off potential is usually more positive than the switch-on potential, or the switch-on potential is usually more negative than the switch-off potential, so that the switch-off potential is reached very quickly and after that there is no longer any risk of the protection system 10 influencing the voltage measurement of the voltage measurement system 36.

[0101] At the same time, one of the capacitors of the decoupler 20, i.e. the first capacitor 28 or the second capacitor 30, remains connected to the pipe 12 at all times to discharge any AC voltages induced in the pipe 12 to the grounding electrode 34 and thus limit them.

[0102] To minimize the influences of the charging currents to the first capacitor 28 and to the second capacitor 30 on the voltage measurement even further, the protection system 10 is in particular set up to pass through a training phase, which is shown schematically in FIGS. 3 and 4.

[0103] In a first step of the training phase, which is shown in FIG. 3, the first capacitor 30 is charged to the switch-on potential, which corresponds to the potential of the pipe 12 to be protected in the corrosion protection mode of the cathodic corrosion protection system 18, as indicated by the hatching in FIG. 3.

[0104] In other words, no charging current (see dotted arrow 46 in FIG. 3) flows as soon as the first capacitor 28 has reached the switch-on potential.

[0105] In a second step of the training phase, which is shown in FIG. 4, the cathodic corrosion protection system 18 switches to the measuring mode, causing the capacitor switching element 32 to switch to the second switch position and connect the second capacitor 30 in an electrically conductive manner to the pipe 12.

[0106] Thus, the second capacitor 30 is charged to the switch-off potential, which corresponds to the potential of the pipe 12 when the cathodic corrosion protection system 18 is in the measuring mode.

[0107] As indicated by the hatching in FIG. 4, the switch-on potential in the illustrated embodiment is greater than the switch-off potential.

[0108] During the second step of the training phase, the first capacitor 28 remains charged to the switch-on potential because it is not electrically conductively connected in a closed electric circuit. When the capacitor switching element 32 returns to the first switch position, the second capacitor 30 remains charged to the switch-off potential because the second capacitor 30 is then no longer electrically connected in a closed electric circuit.

[0109] Thus, at the end of the training phase, the first capacitor 28 and the second capacitor 30 have exactly those potentials which are to be expected for the pipe 12 when the cathodic corrosion protection system 18 is in the corrosion protection mode or in the measuring mode.

[0110] Therefore, no more equalizing currents, even short-term ones, are to be expected when switching between the corrosion protection mode and the measuring mode of the cathodic corrosion protection system 18 to determine the cathodic protection potential, apart from unavoidable fluctuations, so that an even more reliable determination is made possible, while at the same time protection of the pipe 12 against undesirably high AC voltages is ensured at all times.

[0111] A second embodiment of the protection system 10 according to the invention is shown in FIG. 5.

[0112] The second embodiment corresponds essentially to the first embodiment, so that only differences will be discussed in the following. Identical reference numerals denote identical or functionally identical components, and reference is made to the above explanations.

[0113] In the second embodiment, a clipping diode 56 is connected in parallel with the second capacitor 30 and between the capacitor switching element 32 and the second capacitor 30.

[0114] The clipping diode 56 serves to limit the charging of the second capacitor 30 to a maximum value predetermined by the clipping diode, for example to a potential in the range of 0.5 to 0.7 V.

[0115] In this way, the desired potential of the second capacitor 30 is reached even faster, so that in the second operating mode of the protection system 10, no equalizing currents (indicated by a dotted arrow 58 in FIG. 5) flow at all after a very short time.

[0116] FIG. 6 shows a third embodiment of the protection system 10 according to the invention.

[0117] The third embodiment corresponds essentially to the first embodiment, so that only differences will be discussed in the following. Identical reference numerals denote identical or functionally identical components, and reference is made to the above discussions.

[0118] In the third embodiment, both the cathodic corrosion protection element 18 and the decoupler 20 have a switching control element 60 or 62.

[0119] The switching control element 60 is set up to control the corrosion protection switching element 24 and thus trigger the change of the cathodic corrosion protection system 18 between the corrosion protection mode and the measuring mode.

[0120] The switching control element 62 is set up to control the capacitor switching element 32 and thus to cause the change between the first switch position and the second switch position.

[0121] In other words, the respective operating mode of the protection installation 10 is determined via the switching control elements 60 and 62.

[0122] The switching control elements 60 and 62 are time-synchronized. This means that the switching control elements 60 and 62 ensure that the switching processes of the corrosion protection switching element 24 and the capacitor switching element 32 have the lowest possible latency with respect to each other.

[0123] To further reduce latency, the switching control elements 60 and 62 include GNSS modules 64 and 66, respectively, which enable the cathodic corrosion protection system 18 and the decoupler 20 to be located, so that the spatial distance between the cathodic corrosion protection system 18 and the decoupler 20 can be taken into account in the switching process, i.e. when changing the operating mode of the protection system 10.

[0124] In addition, the switching control elements 60 and 62 have communication modules 68 and 70, respectively, which enable data exchange between the switching control elements 60 and 62, for example by means of an Ethernet, WLAN and/or mobile radio connection.

[0125] It is understood that such switching control elements 60 and 62 can also be used in the second embodiment.