• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
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    • 专利摘要:
    FAULT DETECTION METHOD AND SYSTEM, AND ENERGY SYSTEM FOR DIRECT ELECTRIC HEATING CABLES FOR SUBMARINE OIL PIPES. The present invention relates to a fault detection system, (213) electrical supply system, fault detection method, program element and computer-readable medium for direct electric heating cables for subsea pipeline. A fault detection system (213) for undersea direct electric heating cables is described, the fault detection system comprising: a first ammeter (227) for the measurement of a first phase current, a second ammeter (228) to measure a second phase current, a third ammeter (229) to measure a third phase current, a first calculation unit (230) to calculate a negative sequence current from the first phase current, the second phase current, and the third phase current, and a first detection unit (231) to detect a change in the negative sequence current. In addition, a corresponding method, program element and computer-readable medium is described.
    公开号:BR112013031038B1
    申请号:R112013031038-3
    申请日:2012-06-20
    公开日:2021-02-17
    发明作者:Damir Radan
    申请人:Siemens Aktiengesellschaft；
    IPC主号:
    专利说明:

    [0001] [0001] The present invention relates to the field of electrical heating of pipeline systems. More particularly, the invention relates to a fault detection system, a fault detection method, program element and computer-readable medium for direct electric heating cables for subsea pipeline. Foundations
    [0002] [0002] Hydrate formation is a well-known problem in subsea production systems for oil and gas. Several options are available to resolve this issue. Traditionally, chemicals have been used. Ultimately, a more effective direct electric heating method is used to heat the pipeline by forcing a high electric current through the pipeline itself. So far, for example, a direct electric heating cable for a subsea pipeline is installed parallel and connected to a distant end of the pipeline as shown in WO 2004/111519 Al.
    [0003] [0003] For example, a power system to supply a direct electric heating cable to a submarine pipeline with power from a three-phase network has been described in WO 2010/031626 Al.
    [0004] [0004] The direct electric heating cable for subsea pipeline has a voltage decreasing linearly, from an input value at its power supply end to zero at the grounded remote end. Consequently, the electrical voltage recorded in the cable insulation also decreases linearly, from a normal operating voltage at the power supply end to zero at the remote end.
    [0005] [0005] A cable failure in the remote region can be initiated by mechanical damage, for example, a cut that extends through the outer sheath and the insulation system, thereby exposing the copper conductor to sea water. As the conductor is earthed at the remote terminal, the fault will deviate its remaining length from the location of the defect to the grounded end. The corresponding change in the conductor current will be small and extremely difficult to detect at the opposite end of a direct electric heating cable from an underwater pipeline. The current measurement will normally be made further upstream, making small changes even more difficult to detect. The current in a conductor of a subsea direct electric heating system is normally greater than 1000 A, and an improper current of 10 A through physical failure will translate into a much smaller change in the power input end due to displacement of phase. Even with the best current measurement equipment available, cable failures near the remote end therefore go unnoticed.
    [0006] [0006] An electrical current that flows out from the surface of a copper conductor and into seawater can cause rapid (alternative current) corrosion of the copper conductor, even at small current levels or voltage differences. If such a failure is not detected, the end result will be a complete rupture by corrosion of the copper conductor. A gap filled with seawater is thus inserted between the two "tips (stubs) of the conductor", however the electrical impedance of this gap may not be large enough to cause a detectable change in the current at the supply end of the DEH system ( Direct Electric Heating). As the gap will not be able to withstand the voltage of the source, an electrical arc is then formed between the two "conductor tips". The temperature associated with such an arc is several thousand degrees Celsius, so there will be a rapid melting of the copper conductor, as well as any polymer in the vicinity. The boiling temperature of sea water at most applicable water depths will be above the melting points of the polymer, so "water cooling" will not prevent the described melt from occurring.
    [0007] [0007] Underwater pipeline direct electric heating cable is normally placed as close as possible to the thermally insulated pipeline. The thermal insulation, therefore, will also be melted by a failure, as described above. Once the steel pipeline is exposed to sea water, it appears as an alternative and probably low impedance return path for improper current. As the copper conductor is continuously eroded and the gap widened between the "stumps" (ends), the pipeline, at some point in time, will become the lower impedance return path. At that time, a new arc will be created between the conductor's tip (feed inlet side) and the steel pipeline. Rapid melting through the steel wall of the pipeline may occur and the pipeline contents may escape, resulting in serious environmental pollution.
    [0008] [0008] In WO 2007/096775 A2 a fault detection system for direct electric heating cables for subsea pipeline has been proposed. The proposed system is based on fiber optic elements included in the electric heating cables direct from the underwater pipeline. Therefore, the known failure detection system is not suitable for existing installations.
    [0009] [0009] WO 2006/130722 A2 discloses an apparatus and a method for determining a defective phase resulting from a failure in a three-phase ungrounded supply system. The known method comprises comparing a phase angle of an operational phasor to a phase angle of a fixed reference phasor. The operational phasor is derived from a digitized sample of the signal from a plurality of measured signals from the power system. The known method also includes comparing a phase angle difference between the operational phasor and the reference phasor fixed to at least one limit to determine the defective phase. The fixed reference phasor can be a phase-to-phase voltage or a positive sequence voltage from the plurality of measured signals from the power system. The operational phasor can be a zero sequence current, a zero sequence voltage or a combination of a zero sequence current and a zero sequence voltage from the plurality of measured signals from the power system.
    [0010] [00010] In addition, EP 0 079 504 A1 describes a method and apparatus for detecting single-phase earth fault in a three-phase electrical system, and for identifying a defective phase. A single-phase earth fault is correctly distinguished from other faults, including faults, phase-to-ground to earth, even with transmission lines, which use capacitors in series, taking into account the phase-to-phase voltage, which are in quadrature with the voltage at ground of the monitored phase.
    [0011] [00011] In addition, US 2004/0032265 Al discloses a double-ended distance to failure location system using positive or negative amounts of time synchronized for a three-phase transmission line.
    [0012] [00012] However, the fault detection systems proposed in WO 2006/130722 A2, EP 0 079 504 Al, and USA 2004/0032265 Al do not take into account the special needs for electric heating of subsea installations. In particular, these fault detection systems do not relate to subsea power consumers, such as direct electric heating cables.
    [0013] [00013] Thus, there may be a need for a fault detection system for direct heating electric cables for subsea pipeline, an electrical supply for direct electrical heating cables for subsea pipeline, a failure detection method for direct electrical heating cables for subsea pipeline, a fault detection program element for direct electric heating cables for subsea pipeline, and a corresponding computer-readable medium that is suitable for both new and existing installations. SUMMARY
    [0014] [00014] This need can be met by the object according to the invention. Advantageous embodiments of the present invention are described in the embodiments.
    [0015] [00015] According to a first aspect of the invention a fault detection system is provided for direct electric heating cables for subsea pipeline, the fault detection system comprising a first ammeter for measuring a first phase current, a second ammeter to measure a second phase current, a third ammeter to measure a third phase current, a first calculation unit to calculate a negative sequence current from the first phase current, the second phase current, and the third phase current , and a first detection unit to detect a change in the negative sequence current.
    [0016] [00016] In this way, a defect can be detected, even at the far end of an electric heating cable straight from the underwater pipeline. The method can also be used for direct electric heating cables for existing subsea pipelines since all measuring equipment can be installed above the surface. This can also reduce costs as no subsea operation may be necessary.
    [0017] [00017] According to a first embodiment of the fault detection system, the fault detection system further comprises a second calculation unit for calculating a positive sequence current of the first phase current, the second phase current, and the third phase current, and a third calculation unit to divide the negative sequence current by the positive sequence current to obtain a relative negative sequence current, wherein the first detection unit is adapted to detect a change in the negative sequence current relative.
    [0018] [00018] The positive sequence current can only undergo minor changes in the event of faults in the direct electric heating cable of the underwater pipeline and can be essentially dependent on the operating voltage of the direct electrical heating cable in the underwater pipeline. Using the relative negative sequence current as a control can allow the definition of a single limit value to detect a fault in a direct electric heating cable of the subsea pipeline even when the direct electric heating cable of the subsea pipeline is operated with different operating voltages . The operation of the direct electric heating cable of the subsea pipeline with different operating voltages can allow a safe transport of fluids through the associated subsea pipeline, when the fluids have different compositions and / or the ambient temperature of the subsea pipeline changes.
    [0019] [00019] According to a second embodiment of the fault detection system, the fault detection system further comprises a fourth calculation unit for calculating an impedance sequence matrix Zs. The sequence impedance matrix Zs can be obtained from the negative sequence current and the positive sequence current. The Zs sequence impedance matrix can then be used to estimate the fault location of the subsea pipeline direct electric heating cable.
    [0020] [00020] In accordance with a further embodiment of the fault detection system, the fault detection system further comprises a second detection unit adapted to receive a signal that indicates a malfunction of the symmetrization unit.
    [0021] [00021] Loads such as subsea direct heating electric cables can be symmetrized by a symmetrization unit before connecting them to a three-phase network. The symmetrization unit can be positioned above sea level and, consequently, can be easily monitored. If a malfunction of the symmetrization unit is detected, this can be communicated via a signal to the fault detection system. The fault detection unit can therefore prevent a change in the negative sequence current due to a malfunction of the symmetrization unit from being erroneously attributed to the direct electric heating system for subsea pipeline. A fault detection system with a second detection unit adapted to receive a signal indicating a malfunction of the symmetrization unit can be more reliable.
    [0022] [00022] According to a further embodiment of the fault detection system, the fault detection system also comprises a third detection unit adapted to receive a signal that indicates a malfunction of a balancing unit.
    [0023] [00023] Electrical loads can comprise resistive impedances, as well as reactive impedances. This load can be balanced by a balancing unit to reduce the cross section of the cable to the mains. A malfunction of the balancing unit can also affect the negative sequence current. The addition of a third fault detection unit adapted to receive a signal indicating a malfunction of the balancing unit can therefore further improve the reliability of the fault detection system.
    [0024] [00024] According to a second aspect of the invention, a power supply for direct electric heating cables for subsea pipelines is provided, the power supply comprises a symmetrization unit to symmetrize a load, and a fault detection system such as has been described previously.
    [0025] [00025] A power supply according to the invention can provide easy and reliable means for energizing a direct electric submarine heating cable with a three-phase electrical network. In particular, the symmetrization unit can reduce the load experienced by the electrical network.
    [0026] [00026] The symmetrization unit can comprise means of a capacitor and means of an inductor both adaptable to the impedance of the subsea direct electric heating cable. The direct electric heating cable can be connected to the first phase and the third phase of the electrical network, to the means of the first capacitor between the first phase and the second phase of the electrical network and the means of the inductor between the second phase and the third phase of the electrical network.
    [0027] [00027] According to a first embodiment of the power supply, the power supply further comprises a balancing unit to balance the load.
    [0028] [00028] A balancing unit can comprise a second capacitor medium to compensate for the reactive part of the load and, therefore, can help improve energy transmission efficiency.
    [0029] [00029] According to a second embodiment of the power supply, the power supply further comprises a local fault detection device. The local fault detection device can allow the detection of malfunction of the symmetrization unit and / or the balancing unit. In particular, the local fault detection device can supply the fault detection system with signals indicating a malfunction of the symmetrization unit and / or the balancing unit. As has been described here before, such signals can prevent an erroneous detection of a direct electric heating cable for subsea pipeline.
    [0030] [00030] In accordance with a third aspect of the invention a failure detection method is provided for direct electric heating cables for subsea pipeline, the failure detection method comprising measuring the first phase current, measuring a second current phase, measuring a third phase current, calculating a negative sequence current from the first phase current, the second phase current, and the third phase current, and detecting a change in the negative sequence current.
    [0031] [00031] This failure detection method for direct electric heating cables for subsea pipeline can be applied to cables already installed for direct electric heating for subsea pipeline. All steps of the method can be performed above sea level. Subsea measurement or detection devices can be omitted.
    [0032] [00032] According to a first embodiment of the fault detection method, the fault detection method further comprises the calculation of a positive sequence current of the first phase current, the second phase current, and the third phase current dividing the negative sequence current by the positive sequence current to obtain a relative negative sequence current, and detecting a change in the relative negative sequence current by detecting a change in the relative negative sequence current.
    [0033] [00033] Such an embodiment may allow selecting only a threshold value for fault detection even if the direct electric heating cable of the underwater pipeline is subject to different operating voltages.
    [0034] [00034] According to another embodiment of the fault detection method, the fault detection method further comprises the calculation of a sequence impedance matrix Zs from the first phase current, the second phase current, and the third phase current, calculating a change in sequence voltages based on the sequence impedance matrix, and calculating a change in load impedance based on the change in sequence voltages.
    [0035] [00035] A determination of the load impedance change can help to estimate the location of the fault in the direct electric heating cable of the subsea pipeline. Consequently, the direct electric heating cable from the subsea pipeline can be repaired faster.
    [0036] [00036] In accordance with the fourth aspect of the invention, a fault detection program element for direct electric heating cables for subsea pipeline is provided.
    [0037] [00037] The said program element can be easily adaptable to new types of power sources for direct electric heating cables for subsea pipeline. In addition, the program element can be executed by a data processor from an existing power supply for direct electric heating cables for subsea pipeline thus providing an easy way to improve the reliability of direct electric subsea pipeline heating.
    [0038] [00038] The program element can be implemented as computer-readable instruction code in any suitable programming language, such as, for example, JAVA, C ++, and can be stored in a computer-readable medium (removable disk, memory volatile or non-volatile, built-in memory / processor, etc.). The instruction code can be operated to program a computer or any other programmable device to perform the desired functions. The program element may be available from a network, such as the World Wide Web, from which it can be downloaded.
    [0039] [00039] The failure detection method can be carried out by means of a computer software program. However, the invention can also be carried out by means of one or more hardware-specific electronic circuits, respectively. In addition, the failure detection method can also be carried out in a hybrid way, that is, in a combination of software modules and hardware modules.
    [0040] [00040] In accordance with a fifth aspect of the present invention, a computer-readable medium is provided, in which a computer program for processing a physical object, the computer program, is stored when it is being executed by a computer processor. data, it is adapted to control and / or perform the fault detection method as described earlier in this document.
    [0041] [00041] The computer-readable medium can be read by a computer or a processor. The computer reading medium can be, for example, but not limited to, an electrical, magnetic, optical, infrared or semiconductor system, device or transmission medium. The computer-readable medium may include at least one of the following media: a computer-distributable medium, a program storage medium, a recording medium, a computer-readable memory, a random access memory, a erasable programmable memory only reader, a computer-readable software distribution package, a computer-readable signal, a computer-readable telecommunications signal, computer-readable printed matter, and a computer-readable compressed software package.
    [0042] [00042] It has to be noted that embodiments of the invention have been described with reference to different matters. In particular, some embodiments have been described with reference to method type embodiments while other embodiments have been described with reference to apparatus type embodiments. However, one skilled in the art will collect from the above and description that follows that, unless otherwise notified, in addition to any combination of characteristics that belong to a single type of subject also any combination of characteristics relating to different subjects , in particular between the characteristics of the method type embodiments and characteristics of the device type embodiments and characteristics of the device type embodiments are considered to be disclosed with this document.
    [0043] [00043] The aspects defined above and other aspects of the present invention are evident from the exemplary embodiments to be described later, and are explained with reference to the exemplary embodiments. The invention will be described in more detail below with reference to exemplary embodiments, but to which the invention is not limited. Brief Description of Drawings
    [0044] [00044] Figure 1 shows an overview of a system for direct electric heating of an underwater pipeline.
    [0045] [00045] Figure 2 is a schematic representation of a power supply according to the invention.
    [0046] [00046] Figure 3 shows changes in the curves of effective voltage, current effective underwater impedance due to an underwater short circuit.
    [0047] [00047] Figure 4 shows the changes in the negative sequence voltage and negative current due to an underwater short circuit. Detailed Description
    [0048] [00048] The illustration in the drawings is schematic.
    [0049] [00049] Figure 1 shows an overview of a system for direct electric heating of a subsea pipeline 100. The subsea direct electric heating cable 101 comprises a part of pipeline 102 that extends along subsea pipeline 100 and is electrically connected to the submarine pipeline 100 at a connection point 103. The other end of the pipeline part 102 is in particular integral, connected to one end of a first part of the riser column 104 of the direct electric heating cable 101. The direct electric heating submarine cable 101 further comprises a second part of the riser column 105 that is electrically connected with one of its ends to the submarine pipeline 100 at a connection point 106. The other ends of the first part of the heating column riser 104 and the second part of the rise column 105 are connected to a power supply 107. Power supply 107 provides the submarine cable direct electric heating 101 energy from a main electrical network 108. Due to the large distance between the connection point 103 and the connection point 106 a defect in the insulation 109 of the part of the pipeline 102 near the connection point 103 is difficult to detect, by conventional means. However, this can not only prevent heating of the remaining part of the subsea pipeline 100, but it can also seriously damage the subsea pipeline 100.
    [0050] [00050] The submarine direct electric heating cable 101 and the part of the submarine pipeline 100 through which the current flows are shown in Figure 2 as a single-phase direct electric heating load 210. This single-phase direct electric heating load is connected via from a 2-wire connection 215 to an electrical supply 207 which in turn is connected to a main power network 208 by means of a 3-wire connection 216. The power supply 207 comprises a balancing unit 211, a symmetrization 212, a fault detection system 213, and a three-phase transformer 214.
    [0051] [00051] The electrical supply 207 is implemented with an IT grounding scheme (Isole Terre). Therefore, none of the three internal phases 217, 218, 219 of the electrical supply 207 is connected to earth. Consequently, a simple insulation defect within the power system is unlikely to cause dangerous high currents.
    [0052] [00052] Three-phase transformer 214 comprises a high-voltage side 220 and a low-voltage side 221 in which a first tap-changer 222 is connected to the high-voltage side 220 of three-phase transformer 214 and a second tap-changer 223 is connected next to the low voltage side 221 of the three-phase transformer 214. The voltage to be supplied for the direct electric heating load can be selected in the minimum to maximum load range by operating the first tap-changer 222 and the second tap-changer 223. Changing the voltage level the heating power level can be increased or decreased. The first tap-changer 222 and the second tap-changer 223 can be operated as long as the direct electric heating load is fully energized.
    [0053] [00053] The first internal phase 217, the second internal phase 218 and the third internal phase 219 on the low voltage side 221 of the three-phase transformer 214 are connected to the symmetrization unit 212. The symmetrization unit 212 comprises a first capacitor 224 and a inductor 225 to distribute the single-phase direct electric heating load 210 symmetrically between the three phases. The first capacitor 224 is connected to the first internal phase 217 and the second internal phase 218. Inductor 225 is supplied between the second internal phase 218 between the second internal phase 218 and the third internal phase 219.
    [0054] [00054] The capacitive and inductive values of the first capacitor 224 and the inductive means 225 can be changed under load, that is, when the supply system is energized. First capacitor means 224 and inductive means 225 can thus be adapted to the impedance of the direct electric heating load 210 to reduce the negative sequence current. Therefore, the power factor of the transformer can be very close to one and the negative sequence current close to zero.
    [0055] [00055] The balancing unit 211 comprises a second capacitor 226 connected to the first internal phase 217 and to the third internal phase 218 on the one hand and to the direct electric heating load 210 on the other part. The balancing unit 211 compensates for the reactive part of the direct electric heating load 210. The capacitive value of the second capacitor 226 can be changed under load.
    [0056] [00056] The fault detection system 213 includes a first ammeter 227, a second ammeter 228 and a third ammeter 229. A first calculation unit 230 is provided for calculating a negative sequence current from the first phase current , the second phase current, and the third phase current measured with said first ammeter 227, second ammeter 228, and the third ammeter 229. The detection unit 231 detects changes in the negative sequence current indicative of failure in the power cable. direct electric heating of an underwater pipeline. In addition, the fault detection system 213 comprises a second calculation unit 232 and a third calculation unit 233 for calculating a positive sequence current and a relative negative sequence current, respectively. A fourth calculating unit 234 can calculate a sequence impedance matrix Zs that can serve to locate a fault in a direct electric heating cable from an underwater pipeline. Finally, the fault detection system 213 includes a second detection unit 235 and a third detection unit 236 to explain the error signal provided by the local fault detection devices 237, 238, 239 of the balancing unit 211 and the symmetrization unit. 212.
    [0057] [00057] Figure 3 shows a simulation of the development of the effective underwater voltage Vs, effective underwater current Is, and underwater impedance Zs over time. In a time interval from t1 to t2 an insulation defect 109 occurs near connection point 103. The distance from connection point 106 to insulation defect 109 is approximately 97 percent of the distance between connection point 109 and the point connection cable 106.
    [0058] [00058] The effective underwater voltage drops from approximately 9850 volts to approximately t1 and rises from approximately 9750 volts to approximately 9850 volts again at t2. Correspondingly, the effective underwater current rises from approximately 1540 amps to approximately 1,560 amps in ti and drops again to 1540 amps in t2. Such a change in the order of 1 percent (voltage) or 1.3 percent (current) is very difficult to detect by conventional measuring equipment. Even the underwater impedance drops only from approximately 6.4 ohms to approximately 6.2 ohms, therefore, only approximately 3.0 percent in the range from t1 to t2.
    [0059] [00059] Figure 4 now shows the corresponding behavior of the negative sequence current IN and negative sequence voltage VN for the same time interval. Even though the power supply symmetrization unit can be adapted to different single-phase direct electric heating loads, a low effective negative sequence current of 5-10 amps and a low effective negative sequence voltage can be present even if there is no defect. in isolation. However, from t1 to t2 the effective negative sequence voltage is approximately 65 volts around 3 times higher than the effective negative sequence voltage of 22 volts without an insulation fault. In the same range the effective current of negative sequence increases from approximately 9 amps to 25 amps. Such changes in voltage and current are easily detectable.
    [0060] [00060] It should be noted that the term "comprising" does not exclude other elements or steps and the use of articles "one" or "one" does not exclude a plurality. Also elements described in association with different embodiments can be combined. It should also be noted that the reference signs in the embodiments should not be interpreted as limiting the scope of the embodiments.
    [0061] [00061] To recap the above described embodiments of the present invention, we can declare: The fault detection system, power supply, fault detection method, and program element claimed for a direct electric submarine heating cable offers substantial advantages about known systems.
    权利要求:
    Claims (12)
    [0001]
    Fault detection system (213) for direct electric heating cables for subsea pipeline, the fault detection system (213) comprising, a first ammeter (227) to measure a first phase current, a second ammeter (228) to measure a second phase current, a third ammeter (229) to measure a third phase current, a first calculation unit (230) for calculating a negative sequence current from the first phase current, the second phase current, and the third phase current, and a first detection unit (231), characterized by the fact that, the first detection unit (231) is adapted to detect a change in the negative sequence current.
    [0002]
    Fault detection system (213) for direct electric heating cables for subsea pipeline, according to claim 1, characterized in that it additionally comprises, a second calculation unit (232) for calculating a positive sequence current from the first phase current, the second phase current, and the third phase current, and a third calculation unit (233) for dividing the negative sequence current by the positive sequence current to obtain a relative negative sequence current, the first detection unit (231) being adapted to detect a change in the relative negative sequence current.
    [0003]
    Fault detection system (213) for direct electric heating cables for subsea pipeline, according to claim 1 or 2, characterized in that it additionally comprises a fourth calculation unit (234) for the calculation of an impedance sequence matrix Zs .
    [0004]
    Fault detection system (213) for direct electric heating cables for subsea pipeline, according to any one of claims 1 to 3, characterized in that it additionally comprises a second detection unit (213) adapted to receive a signal indicating a malfunction of a symmetrization unit.
    [0005]
    Fault detection system (213) for direct electric heating cables for subsea pipeline, according to any one of claims 1 to 4, characterized in that it additionally comprises a third detection unit (236) adapted to receive a signal indicating a malfunction of a balancing unit (211).
    [0006]
    Power supply for direct heating electric cables for subsea pipeline, characterized in that it comprises a symmetrization unit (212) to symmetrize a load and a fault detection system as defined in any one of claims 1 to 5.
    [0007]
    Power supply for direct electric heating cables for subsea pipeline, according to claim 6, characterized in that it additionally comprises a balancing unit (211) to balance the load.
    [0008]
    Power supply for direct electric heating cables for subsea pipeline, according to claim 6 or 7, characterized by additionally comprising a local fault detection device (237, 238, 239) for detecting malfunction of the symmetrization unit ( 212) and / or the balancing unit.
    [0009]
    Power supply for direct electric heating cables for subsea pipeline, according to any one of claims 6 to 8, characterized in that it additionally comprises a three-phase transformer (214).
    [0010]
    Fault detection method for direct electric heating cables of subsea pipeline, the fault detection method comprising, measurement of a first phase current, measurement of a second phase current, measurement of a third phase current, and calculating a negative sequence current from the first phase current, the second phase current and the third phase current, characterized by the fact that the failure detection method additionally comprises, detection of a change in the negative sequence current.
    [0011]
    Failure detection method for direct electric heating cables for subsea pipeline, according to claim 10, characterized in that it additionally comprises the following steps, calculating a positive sequence current from the first phase current, the second phase current and the third phase current, dividing the negative sequence current by the positive sequence current to obtain a relative negative sequence current, and detect a change in the relative negative sequence current by detecting a change in the relative negative sequence current.
    [0012]
    Failure detection method according to claim 10 or 11, characterized in that it further comprises the following steps, calculating a sequence impedance matrix Zs of the first phase current, the second phase current and the third phase current, calculating a change in sequence voltages based on the sequence impedance matrix, and calculation of a change in load impedance based on the change in sequence voltages.
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    法律状态:
    2018-12-11| B06F| Objections, documents and/or translations needed after an examination request according [chapter 6.6 patent gazette]|
    2020-10-06| B06A| Patent application procedure suspended [chapter 6.1 patent gazette]|
    2020-12-08| B09A| Decision: intention to grant [chapter 9.1 patent gazette]|
    2021-02-17| B16A| Patent or certificate of addition of invention granted [chapter 16.1 patent gazette]|Free format text: PRAZO DE VALIDADE: 20 (VINTE) ANOS CONTADOS A PARTIR DE 20/06/2012, OBSERVADAS AS CONDICOES LEGAIS. |
    2021-07-13| B25A| Requested transfer of rights approved|Owner name: SIEMENS ENERGY AS (NO) |
    2022-02-08| B25L| Entry of change of name and/or headquarter and transfer of application, patent and certificate of addition of invention: publication cancelled|Owner name: SIEMENS AKTIENGESELLSCHAFT (DE) Free format text: ANULADA A PUBLICACAO CODIGO 25.1 NA RPI NO 2636 DE 13/07/2021 POR TER SIDO INDEVIDA. |
    2022-02-22| B25A| Requested transfer of rights approved|Owner name: SIEMENS ENERGY AS (NO) |
    优先权:
    申请号 | 申请日 | 专利标题
    EP11172392A|EP2541263A1|2011-07-01|2011-07-01|Fault detection system and method, and power system for subsea pipeline direct electrical heating cables|
    EP11172392.0|2011-07-01|
    PCT/EP2012/061863|WO2013004500A1|2011-07-01|2012-06-20|Fault detection system and method, and power system for subsea pipeline direct electrical heating cables|
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