Protection system for pipelines
Patent Information
- Application Number
- EP2023707334
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-04-25
- Filing Date
- 2023-02-23
- Publication Date
- 2025-03-05
AI Technical Summary
Cathodic corrosion protection systems face challenges in accurately measuring the IR-free potential due to interference from external sources and delimitation units, which can lead to falsified measurements and potentially dangerous contact voltages during pipeline maintenance.
A protection system with a cathodic corrosion protection system that switches between corrosion protection and measuring modes, utilizing a delimitation unit with multiple capacitors that switch between different operating modes to prevent disruptive currents and ensure accurate potential measurement while limiting alternating voltages.
Enables reliable measurement of the cathodic protection potential while effectively dissipating alternating voltages, reducing the risk of high contact voltages and ensuring the pipeline's protection against corrosion, even with damaged insulation.
Smart Images
Figure 1.1
Abstract
Description
[0001] Pipeline protection system
[0002] The invention relates to a protection system for pipelines and the use of such a protection system for protecting a pipeline.
[0003] Over the course of their service life, installed pipelines are exposed to various environmental influences that can lead to corrosion. Particularly in the case of buried metal pipelines, protective measures are therefore necessary to reduce the extent of corrosion or prevent it from occurring.
[0004] Such pipelines are therefore usually covered with an insulating material. The problem is that the coating can be damaged, for example, during installation of the pipeline and / or during necessary assembly or maintenance work. In this case, a particularly high local corrosion current is generated at the damaged area of the coating, also known as the defect, leading to rapid corrosion of the pipeline.
[0005] To prevent this, it is known to provide a cathodic corrosion protection system (also known as a "CCP system"). The corrosion protection system applies a negative direct current (DC) potential to the pipeline to be protected by electrically connecting the pipeline to a rectifier of the cathodic corrosion protection system, which in turn is electrically connected to an anode located near the pipeline. This results in a so-called CCP protection current flowing between the anode and the pipeline, specifically the defect in the pipeline, which counteracts the corrosion current and thus prevents corrosion from occurring. In other words, a cathodic protection potential is generated by the cathodic corrosion protection system.
[0006] To ensure the reliable operation of the planned cathodic corrosion protection, the cathodic corrosion protection system must be monitored and regularly evaluated. Evaluation criteria include, for example, the value of the unaffected pipeline potential, which can be determined by measuring the voltage between the pipeline and a reference electrode, typically a Cu / CuSC>4 electrode. This potential is also referred to as the "IR-free potential." According to DIN EN 12954, the IR-free potential should be less than or equal to a minimum protection potential of approximately -850 mV.
[0007] A problem with this measurement is that the potential measured between the reference electrode of the voltage measuring system and the pipeline can be distorted by various influences, the sum of all these influences being referred to as "IR drop." The relevant influences on the voltage measurement can be due to currents from the protective current system itself, nearby external protective current systems, compensating currents, element currents, currents from DC-operated industrial and railway systems, and / or ground currents.
[0008] In practice, however, the measurement between the reference electrode and the pipeline can only determine the sum of the IR-free potential and the IR drop. Therefore, it is generally intended to eliminate sources of interference that contribute to the IR drop as completely as possible. For this reason, it is common practice to disconnect the rectifier of the cathodic corrosion protection system from the pipeline for a few seconds, for example, approximately three seconds, to measure the IR-free potential. The potential measured during this process is also called the cut-out potential. This procedure is known as the "cut-out technique." As long as no other sources of interference are present, the cut-out potential is equal to the IR-free potential.
[0009] In addition to the corrosion mechanism described above, other adverse effects on pipelines must be considered. Underground pipelines, in particular, are often laid near high-voltage lines. As a result, the electromagnetic field of the high-voltage lines induces an alternating voltage in the pipeline, the magnitude of which depends, among other things, on the relative position of the pipeline to the respective high-voltage line. If this induced alternating voltage exceeds certain limits, for example, an effective alternating voltage of 60 V, measures must be taken to reduce the alternating voltage, as otherwise, for example, alternating current corrosion or dangerously high contact voltages may occur.
[0010] For this purpose, so-called isolation units are known, which divert any alternating voltage to a ground electrode while simultaneously not negatively affecting the direct current potential generated by the cathodic corrosion protection system. Common isolation units incorporate a capacitor that is conductive for alternating voltages but has a high resistance for direct voltages. The larger the capacitor's capacitance, the lower the alternating current resistance, thus improving the diversion of any alternating currents that may occur.
[0011] However, with such a combination of a delimiter and a cathodic corrosion protection system, the problem arises that the measurement of the IR-free potential is distorted by the delimiter. This is due to the high capacitance of the delimiter, necessary for the best possible dissipation of alternating currents, causing a current to continue to flow to the pipeline even after the rectifier of the cathodic corrosion protection system has been disconnected for voltage measurement, since the charged capacitor of the delimiter acts as a DC voltage source. In other words, a stray current is generated that continues until the capacitor of the delimiter is completely discharged.
[0012] To circumvent this problem, it is known to disconnect the isolation unit from the pipeline at the same time as the cathodic protection system's rectifier, preventing any compensating currents from flowing. However, this results in the AC voltage generated on the pipeline no longer being limited for the duration of the measurement, which can lead to dangerously high touch voltages in the pipeline and thus complicate the work and handling of the pipeline.
[0013] It is therefore the object of the invention to provide a protection system for pipelines that both ensures the dissipation of alternating voltages and, at the same time, allows the most accurate measurement of the cathodic protection potential. This object is achieved according to the invention by a protection system for pipelines, comprising a cathodic corrosion protection system that includes a rectifier and a corrosion protection switching element electrically connected to the rectifier. The cathodic corrosion protection system is configured to switch between a corrosion protection mode and a measuring mode, with the rectifier not being connected in the measuring mode. The protection system also has a demarcation unit that includes a first capacitor and a second capacitor, as well as a capacitor switching element.In a first switching position, the capacitor switching element is electrically connected to the first capacitor when the cathodic corrosion protection system is in corrosion protection mode. In a second switching position, the capacitor switching element is electrically connected to the second capacitor when the cathodic corrosion protection system is in measurement mode.
[0014] According to the invention, several capacitors are provided in the isolation unit, between which switching occurs depending on the current operating mode of the cathodic corrosion protection system. This ensures at all times that the pipeline to be protected is connected to one of the capacitors, i.e., the first capacitor or the second capacitor, of the isolation unit and is thus protected against any alternating voltages.
[0015] Furthermore, the capacitor of the demarcation unit, which is not electrically connected to the capacitor switching element, cannot cause any disturbing compensating currents because it is no longer in a closed circuit with the pipeline.
[0016] At the same time, the first capacitor and the second capacitor can be charged to different potentials in order to eliminate or at least minimize compensating currents in the measuring mode of the cathodic corrosion protection system.
[0017] In this way, a reliable measurement of the cathodic protection potential generated by the cathodic corrosion protection system is enabled, while at the same time an alternating voltage present in the pipeline to be protected is limited at any time via the limiting unit.
[0018] This principle is referred to as “switching technology” in contrast to the well-known “switch-off technology” of cathodic corrosion protection systems.
[0019] The first capacitor is also called the “main capacitor” and the second capacitor is called the “measuring capacitor”.
[0020] The main capacitor and the measuring capacitor can be designed differently.
[0021] In particular, the main capacitor, which is connected to the pipeline to be protected for most of the operating time of the barrier unit, can be a capacitor with higher performance characteristics than the measuring capacitor, which is only connected in the measuring mode of the cathodic corrosion protection system, i.e., for comparatively short periods. In this way, the overall costs and the required installation space of the protection system according to the invention can be optimized.
[0022] The pipeline is an electrically conductive pipeline and, in particular, is buried, meaning it is laid in the earth, so that the earth represents a medium through which currents flow. In addition to the earth, other media can also surround the electrically conductive pipeline, which is why it can generally be referred to as an electrically conductive pipeline that is laid in a medium, namely a medium through which currents flow.
[0023] The term “electrically connected” here and in the following means that there is a connection through which an electric current flows.
[0024] The pipeline is, in particular, a metallic pipeline with a covering made of an insulating material. Such pipelines exhibit high mechanical stability and resilience, and their service life is optimized by the covering. At the same time, the protection system according to the invention provides reliable corrosion protection even in the event of any damage to the covering. The compositions of the metallic pipeline and the insulating material are not further restricted, so any materials known in the prior art can be used.
[0025] For example, the metallic pipeline is made of steel or copper.
[0026] To reduce the duration of the switching operation between the first switching position and the second switching position of the capacitor switching element, the capacitor switching element can be a power semiconductor switch. This further improves the ability to ensure that any alternating voltage present on the pipeline remains below a specified limit, even during the switching operation.
[0027] In order to further improve the accuracy of the measurement of the cathodic protection potential, the protection system can be configured to charge the first capacitor to a switch-on potential and to charge the second capacitor to a switch-off potential in a training phase of the protection system, wherein the switch-on potential corresponds to the potential of the pipeline to be protected in the corrosion protection mode and the switch-off potential of the second capacitor corresponds to the potential of the pipeline to be protected in the measurement mode.
[0028] The potential of the pipeline to be protected in the corrosion protection mode of the cathodic corrosion protection system depends on the protection potential generated by the cathodic corrosion protection system. In other words, during the training phase, the first capacitor is charged to the switch-on potential based on the cathodic protection potential and the cathodic protection current of the cathodic corrosion protection system via a charging current flowing through the pipeline. The potential of the pipeline to be protected in the measuring mode, however, is not influenced by the cathodic protection potential, since in the measuring mode the pipeline to be protected is no longer electrically connected to the rectifier of the cathodic corrosion protection element.
[0029] After completion of the training phase, the first capacitor and the second capacitor are thus charged to the potentials of the pipeline to be protected expected in the respective mode of the cathodic corrosion protection system, so that in each switching position of the capacitor switching element it is ensured that no compensating currents are to be expected through the demarcation unit, which could influence the measurement of the cathodic protection potential, apart from unavoidable fluctuations.
[0030] The turn-on potential is, in particular, more negative than the turn-off potential. Accordingly, the second capacitor can be designed more simply in terms of its performance characteristics than the first capacitor, particularly with regard to its maximum capacitance, thereby minimizing the costs and space required for the entire protection system according to the invention.
[0031] The first capacitor and / or the second capacitor may have a capacitance in the range of 0.1 to 1.0 F. With a capacitance of less than 0.1 F, the ability of the capacitors to dissipate alternating currents may be insufficient, while the cost and space requirements increase excessively with a capacitance of more than 1.0 F.
[0032] In particular, the demarcation unit has an earth electrode which is electrically connected to the first capacitor and the second capacitor.
[0033] In other words, only a common earth electrode is used, allowing alternating currents to be diverted. This further reduces the complexity and cost of the protection system.
[0034] In one variant, a limiting diode is connected in parallel to the second capacitor.
[0035] The limiting diode serves to limit the potential to which the second capacitor is charged during use of the protection system, in particular the switch-off potential, to a limit value predetermined by the choice of diode. This is particularly advantageous if the pipeline to be protected has such a high spreading resistance that, despite switching to the second capacitor in measuring mode, it takes so long for the potential of the second capacitor to equalize to the potential of the pipeline to be protected that the measurement of the cathodic protection potential could still be impaired. Furthermore, in this variant, the second capacitor can be selected so that its maximum dielectric strength is only slightly above the limit value predetermined by the diode, even if the pipeline to be protected would have a higher potential in measuring mode.
[0036] The limit value determined by the choice of diode is, for example, in the range of 0.5 to 0.7 V.
[0037] If, in this variant, the protection system goes through the previously described training phase, the expression that the switch-off potential of the second capacitor corresponds to the potential of the pipeline to be protected in the measuring mode means that the switch-off potential of the second capacitor corresponds to the potential of the pipeline to be protected in the measuring mode to the extent that the limiting diode allows.
[0038] To further synchronize the switching operations of the corrosion protection switching element and the capacitor switching element, the cathodic corrosion protection system and the demarcation unit can have switching control elements that are time-synchronized.
[0039] The switching control element of the cathodic corrosion protection system is designed to control the corrosion protection switching element and thus trigger the change of the cathodic corrosion protection system between the corrosion protection mode and the measuring mode.
[0040] The switching control element of the demarcation unit is designed to control the capacitor switching element and thus to effect the change between the first switching position and the second switching position.
[0041] In other words, the switching control element minimizes the latency between switching operations.
[0042] Time synchronization can be achieved taking into account the spatial distance between the cathodic corrosion protection system and the demarcation unit. For this purpose, both the cathodic corrosion protection system and the demarcation unit can have a dedicated GPS module or, more generally, a dedicated GNSS module, which enables the location of the cathodic corrosion protection system or the demarcation unit. The switching control elements can also each have a communication module for data exchange, with the switching control elements being configured to exchange data with each other via the respective communication modules.
[0043] The switching control elements can further be configured to send and / or receive data to a control center by means of the communication modules, for example diagnostic data, protocol data and / or control signals.
[0044] Data exchange can be wired or wireless, for example via Ethernet, a WLAN connection and / or a cellular connection.
[0045] The object of the invention is further achieved by the use of the protection system as described above for protecting a pipeline, wherein the corrosion protection switching element and the capacitor switching element are electrically conductively connected to the pipeline.
[0046] The features and characteristics of the pipeline protection system described above apply accordingly to the use of the protection system to protect a pipeline and vice versa.
[0047] The pipeline is in particular laid underground and is, for example, a pipeline, in particular a gas pipeline.
[0048] Further features and characteristics of the invention will become clear from the following description of exemplary embodiments, which are not intended to be limiting, and from the drawings, in which:
[0049] - Fig. 1 shows a first embodiment of a protection system for pipelines according to the invention in a first operating mode,
[0050] - Fig. 2 shows the protection system from Fig. 1 in a second operating mode,
[0051] - Fig. 3 the protection system from Fig. 1 in a first step of a training phase, - Fig. 4 the protection system from Fig. 1 in a second step of a training phase,
[0052] - Fig. 5 shows a second embodiment of the protection system for pipelines according to the invention in the second operating mode, and
[0053] - Fig. 6 shows a third embodiment of the pipeline protection system according to the invention in the first operating mode.
[0054] Fig. 1 shows schematically a protection system 10 according to the invention for a pipeline 12.
[0055] The pipe 12 is a metallic pipe made of stainless steel with a covering 14 made of an insulating material.
[0056] It is understood that the pipeline 12 may also be made of other materials, in particular other metals, as known in the art.
[0057] The pipeline 12, for example, is laid underground, i.e. in the earth below the earth's surface (not shown) and is thus in contact with the surrounding soil.
[0058] In the embodiment shown, the casing 14 has a defect 16, i.e., a damage. At the defect 16, the metal surface of the pipeline 12 is in direct contact with the surrounding soil, so that the pipeline 12 has an increased tendency to corrosion at this location.
[0059] In addition, the pipeline 12 is arranged near a high-voltage line (not shown), which causes an alternating voltage in the pipeline 12.
[0060] The protection system 10 comprises a cathodic corrosion protection system 18 and a demarcation unit 20, the functions of which will be described in more detail below.
[0061] The corrosion protection system 18 comprises a rectifier 22, a corrosion protection switching element 24, which in Fig. 1 electrically connects the pipeline 12 to the rectifier 22, and an anode 26 electrically connected to the rectifier 22.
[0062] The rectifier 22 is connected to a voltage source (not shown) which supplies the rectifier 22 with energy.
[0063] The demarcation unit 20 has a first capacitor 28, also referred to as the “main capacitor”, and a second capacitor 30, also referred to as the “measuring capacitor”.
[0064] The first capacitor 28 and / or the second capacitor 30 have / has a capacitance in the range of 0.1 to 1.0 F, wherein in particular the capacitance of the first capacitor 28 is higher than the capacitance of the second capacitor 30.
[0065] In addition, the demarcation unit 20 has a capacitor switching element 32 which is electrically connected to the pipeline 12.
[0066] In Fig. 1, the capacitor switching element 32 is shown in a first switching position in which the capacitor switching element 32 is electrically conductively connected to the first capacitor 28.
[0067] The demarcation unit 20 also includes an earthing electrode 34.
[0068] The earth electrode 34 is electrically connected to both the first capacitor 28 and the second capacitor 30.
[0069] The pipeline 12 is further electrically connected to a voltage measuring system 36.
[0070] The voltage measuring system 36 comprises a voltmeter 38 and a reference electrode 40.
[0071] The voltage measurement system 36 can be a component of the protection system 10 according to the invention or form a separate component. It is also conceivable for the voltage measurement system 36 to be integrated into the cathodic corrosion protection system 18 or the barrier unit 20.
[0072] 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 switching position in which the capacitor switching element 32 is electrically conductively connected to the first capacitor 28.
[0073] 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, i.e. the cathodic corrosion protection system 18 is in a so-called “measuring mode”, and the capacitor switching element 32 is in a second switching position in which the capacitor switching element 32 is electrically conductively connected to the second capacitor 30.
[0074] The corrosion protection switching element 24 and the capacitor switching element 32 are synchronized or coupled with 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 changeover switches. This means that the capacitor switching element 32 is in the first switching position when the corrosion protection switching element 24 electrically connects the rectifier 22 to the pipeline 12, and the capacitor switching element 32 is in the second switching position when the corrosion protection switching element 24 does not connect the rectifier 22, i.e., does not connect it to the pipeline 12.
[0075] Preferably, however, the corrosion protection switching element 24 and the capacitor switching element 32 are separate switches that are synchronized or coupled to each other.
[0076] The capacitor switching element 32 is in particular a power semiconductor switch in order to achieve the shortest possible switching time.
[0077] The operation of the protection system 10 according to the invention is described in more detail below, i.e. the use of the protection system 10 for protecting the pipeline 12 or a method for protecting the pipeline 12. First, the cathodic corrosion protection system 18 and the demarcation unit 20 are connected to the pipeline 12 to be protected by electrically connecting the corrosion protection switching element 24 and the capacitor switching element 32 to the pipeline 12.
[0078] The pipeline 12 is exposed to various influences over its service life, which can lead to corrosion and thus to damage to the pipeline 12. In particular, at the defect 16, where the coating 14 is damaged and the metal surface of the pipeline 12 comes into direct contact with the surrounding soil, there is a high tendency to corrosion, resulting in a so-called corrosion current.
[0079] In order to counteract this corrosion current, in the corrosion protection mode of the cathodic corrosion protection system 18, a cathodic protection potential is generated by the system, which results in a protection current between the anode 26 and the pipeline 12, which is indicated in Fig. 1 by a dotted arrow 44.
[0080] 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 pipeline 12 at the defect 16 is reliably prevented.
[0081] 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.
[0082] In this way, alternating voltages induced in the pipeline 12, for example due to the nearby high-current line (not shown), are diverted via the first capacitor 28 to the earth electrode 34, thus reducing the effective alternating voltage on the pipeline 12.
[0083] Because the cathodic corrosion protection system 18 simultaneously generates a protective current, in the first operating mode of the protection system 10, in which the capacitor switching element 32 is in its first switching position, a charging current also flows from the pipeline 12 to the first capacitor 28, as indicated by a dotted arrow 46 in Fig. 1, until the first capacitor 28 has charged to the same potential as the pipeline 12. In addition, a switch-on potential is established between the earth electrode 34 and the pipeline 12, which is indicated by a double arrow 48 in Fig. 1.
[0084] In order to ensure that the minimum protection potential is guaranteed, i.e. the cathodic protection potential is sufficiently high to prevent corrosion of the pipeline 12, the potential of the pipeline 12 to be protected is measured by means of the voltage measuring system 36.
[0085] In particular, the measurement of the potential of the pipeline 12 to be protected is repeated at regular intervals by means of the voltage measuring system 36.
[0086] In Fig. 1, a double arrow 50 indicates that the voltage measuring system 36 can only determine the potential present between the pipeline 12, in particular at the relevant defect 16, and the reference electrode 40.
[0087] However, this value is influenced by the cathodic protection potential of the cathodic corrosion protection system 18 and any other sources of error such as nearby external protective current systems, compensating currents, element currents, currents from DC-operated industrial and railway systems and / or earth currents.
[0088] In order to nevertheless enable a reliable measurement of the potential of the pipeline 12 to be protected, the measurement is carried out by the voltage measuring system 36 as a measurement pair, wherein the measurement pair comprises a first measurement which is carried out with the rectifier 22 switched on, i.e. while the cathodic corrosion protection system 18 is in corrosion protection mode (as shown in Fig. 1) and a second measurement which is carried out with the rectifier 22 not switched on, i.e. while the cathodic corrosion protection system 18 is in measuring mode (as shown in Fig. 2).
[0089] The actual potential of the pipeline 12 to be protected is then determined, for example, as the difference between the first and second measurements, whereby the respective signs of the measured voltage values are taken into account when calculating the difference. If it can be assumed that no other sources of interference are present, then, as an alternative to determining the cathodic protection potential, a single measurement can also be performed with the rectifier 22 not switched on, analogous to the second measurement.
[0090] In order to prevent the second measurement from being falsified by the first capacitor 28, which was previously charged due to the charging current in the first operating mode of the protection system 10, discharging, i.e. in order to prevent a direct current from being generated between the reference electrode 34 and the pipeline 12, the capacitor switching element 32 changes into the second switching position synchronously with the change of the cathodic corrosion protection system 18 into the measuring mode, in which it is no longer the first capacitor 28 but the second capacitor 30 that is electrically conductively connected to the pipeline 12 (cf. Fig. 2).
[0091] Thus, a charging current flows between the pipeline 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 pipeline 12 with the cathodic corrosion protection system 18 deactivated.
[0092] As a result, a switching-off potential is established between the earth electrode 34 and the pipeline 12, which is indicated by a double arrow 54 in Fig. 1.
[0093] The switch-off potential is generally more positive than the switch-on potential, or the switch-on potential is generally more negative than the switch-off potential, so that the switch-off potential is established very quickly and thereafter there is no longer any risk of the protection system 10 influencing the voltage measurement of the voltage measuring system 36.
[0094] At the same time, one of the capacitors of the demarcation unit 20, i.e. the first capacitor 28 or the second capacitor 30, remains connected to the pipeline 12 at all times in order to divert any alternating voltages induced in the pipeline 12 to the earth electrode 34 and thus to limit them.
[0095] In order to further minimize the influence of the charging currents to the first capacitor 28 and to the second capacitor 30 on the voltage measurement, the protection system 10 is particularly designed to go through a training phase, which is schematically shown in Figs. 3 and 4.
[0096] 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 pipeline 12 to be protected in the corrosion protection mode of the cathodic corrosion protection system 18, as indicated by the hatching in Fig. 3.
[0097] In other words, no charging current flows (see dotted arrow 46 in Fig. 3) as soon as the first capacitor 28 has reached the turn-on potential.
[0098] 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, whereby the capacitor switching element 32 changes to the second switching position and electrically connects the second capacitor 30 to the pipeline 12.
[0099] Thus, the second capacitor 30 is charged to the switch-off potential, which corresponds to the potential of the pipeline 12 when the cathodic corrosion protection system 18 is in the measuring mode.
[0100] As indicated by the hatching in Fig. 4, the turn-on potential in the embodiment shown is greater than the turn-off potential.
[0101] During the second step of the training phase, the first capacitor 28 remains charged to the turn-on potential because it is not electrically connected in a closed circuit. When the capacitor switching element 32 returns to the first switching position, the second capacitor 30 remains charged to the turn-off potential because the second capacitor 30 is no longer electrically connected in a closed circuit.
[0102] Thus, at the end of the training phase, the first capacitor 28 and the second capacitor 30 have exactly the potentials that are to be expected for the pipeline 12 when the cathodic corrosion protection system 18 is in the corrosion protection mode or in the measurement mode.
[0103] Therefore, no compensating currents, even short-term ones, are to be expected when switching back and forth between the corrosion protection mode and the measuring mode of the cathodic corrosion protection system 18 for the determination of the cathodic protection potential, apart from unavoidable fluctuations, so that an even more reliable determination is made possible, while at the same time the protection of the pipeline 12 against unwanted high alternating voltages is ensured at all times.
[0104] Fig. 5 shows a second embodiment of the protection system 10 according to the invention.
[0105] The second embodiment is essentially the same as the first embodiment, so only differences will be discussed below. The same reference numerals denote identical or functionally identical components, and reference is made to the above explanations.
[0106] In the second embodiment, a limiting diode 56 is connected in parallel to the second capacitor 30 and between the capacitor switching element 32 and the second capacitor 30.
[0107] The limiting diode 56 serves to limit the charging of the second capacitor 30 to a maximum value predetermined by the limiting diode, for example to a potential in the range of 0.5 to 0.7 V.
[0108] 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, after a very short time no compensating currents (indicated by a dotted arrow 58 in Fig. 5) flow any more.
[0109] Fig. 6 shows a third embodiment of the protection system 10 according to the invention.
[0110] The third embodiment is essentially the same as the first embodiment, so only the differences will be discussed below. The same reference numerals denote identical or functionally identical components, and reference is made to the above explanations.
[0111] In the third embodiment, both the cathodic corrosion protection element 18 and the demarcation unit 20 have a switching control element 60 and 62, respectively. The switching control element 60 is configured 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.
[0112] The switching control element 62 is configured to control the capacitor switching element 32 and thus to effect the change between the first switching position and the second switching position.
[0113] In other words, the respective operating mode of the protective system 10 is determined via the switching control elements 60 and 62.
[0114] The switching control elements 60 and 62 are time-synchronized. This means that the switching control elements 60 and 62 ensure that the switching operations of the corrosion protection switching element 24 and the capacitor switching element 32 have the lowest possible latency relative to each other.
[0115] To further reduce the latency, the switching control elements 60 and 62 have GNSS modules 64 and 66, respectively, which enable the location of the cathodic corrosion protection system 18 and the demarcation unit 20, respectively, so that the spatial distance between the cathodic corrosion protection system 18 and the demarcation unit 20 can be taken into account during the switching process, i.e. when changing the operating mode of the protection system 10.
[0116] 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.
[0117] It is understood that such switching control elements 60 and 62 can also be used in the second embodiment.
Claims
Patent claims 1. Protection system (10) for pipelines (12), comprising a cathodic corrosion protection system (18) comprising a rectifier (22) and a corrosion protection switching element (24) electrically connected to the rectifier (22), wherein the cathodic corrosion protection system (18) is configured to switch between a corrosion protection mode and a measurement mode, wherein in measurement mode the rectifier (22) is not switched on, and a limiting unit (20) comprising a first capacitor (28) and a second capacitor (30) and a capacitor switching element (32), wherein the capacitor switching element (32) is electrically connected to the first capacitor (28) in a first switching position when the cathodic corrosion protection system (18) is in corrosion protection mode, and wherein the capacitor switching element (32) is electrically connected to the second capacitor (30) in a second switching position.when the cathodic corrosion protection system (18) is in measurement mode.
2. Protection system according to claim 1, wherein the pipeline (12) is a metallic pipeline with a covering (14) made of an insulating material.
3. Protection system according to claim 1 or 2, wherein the capacitor switching element (32) is a power semiconductor switch.
4. Protection system according to one of the preceding claims, wherein the protection system (10) is configured to charge the first capacitor (28) to a switch-on potential and the second capacitor (30) to a switch-off potential during a training phase of the protection system (10), and wherein the switch-on potential corresponds to the potential of the pipeline (12) to be protected in corrosion protection mode and the switch-off potential of the second capacitor corresponds to the potential of the pipeline (12) to be protected in measurement mode.
5. Protection system according to claim 4, wherein the switch-on potential is more negative than the switch-off potential.
6. Protection system according to one of the preceding claims, wherein the first capacitor (28) and / or the second capacitor (30) have a capacitance in the range of 0.1 to 1.0 F.
7. Protection system according to one of the preceding claims, wherein the boundary unit (20) has an earth electrode (34) connected to the first capacitor (28) and the second capacitor (30) is electrically connected.
8. Protection system according to one of the preceding claims, wherein a limiting diode (56) is connected in parallel to the second capacitor (30).
9. Protection system according to one of the preceding claims, wherein the cathodic corrosion protection system (18) and the demarcation unit (20) via Switching controls (60, 62) are available that are time-synchronized.
10. Use of the protection system (10) according to one of the preceding claims for the protection of a pipeline (12), wherein the corrosion protection switching element (24) and the capacitor switching element (32) are connected to the pipeline (12).