US20130286548A1 - Subsea Electrical System Having Subsea Penetrator with Integral Current Sensor - Google Patents

Abstract

A system and method for coupling electrical power subsea. The system comprises a subsea penetrator to seal an opening around a conductor extending through a partition or enclosure. The subsea penetrator comprises an integral current sensor operable to produce a signal representative of current through the conductor. The penetrator comprises a boot configured to seal the opening through which the conductor extends. The current sensor may be disposed within the boot.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
• This application claims priority to Provisional patent application No. 61/639,865, filed on Apr. 28, 2012, which is hereby incorporated by reference in its entirety.
BACKGROUND
• 1. Field of the Invention
• The present invention relates generally to subsea electrical systems and, more specifically, to a subsea electrical distribution system comprising a subsea circuit breaker.
• 2. Description of the Related Art
• This section is intended to introduce the reader to aspects of art that may be related to aspects of the present invention, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
• The petroleum industry has seen an increase in interest in the placement of pumping and/or processing equipment for fluids produced from subsea wells on the sea floor. Subsea pumping and processing system are particularly suited for challenging environments, such as the deep sea and Arctic, which are difficult to support from fixed platforms or floating production units. Subsea hydrocarbon production fields may comprise many subsea wells extending over hundreds of square miles. Therefore, subsea pumping and/or processing equipment may be required to be placed at several locations many miles apart.
• Power for the subsea pumping and/or processing equipment must be supplied from a fixed platform, a floating production unit, or from land. Thus, power cables may be needed to cover extreme distances, possibly a hundred miles or more. The greater the number of pumping and/or processing units in a production field, the greater the number of power cables extending over these long distances are needed. Such systems are complicated and expensive.
SUMMARY OF THE INVENTION
• A system and method for coupling electrical power subsea. The system comprises a subsea electrical distribution system having at least one modular circuit breaker assembly. The modular circuit breaker assembly is controlled by a control system that has a plurality of circuit breaker controls. Each circuit breaker is operable to be controlled by a plurality of circuit breaker controls and each circuit breaker control is operable to control a plurality of circuit breakers. Therefore, control of each circuit breaker is maintained even if a circuit breaker control fails. The system has extendable electrical connectors to facilitate connection of subsea electrical distribution system components.
BRIEF DESCRIPTION OF THE DRAWINGS
• Advantages of the invention may become apparent upon reading the following detailed description and upon reference to the drawings in which:
• FIG. 1 is a schematic diagram of a subsea system, in accordance with exemplary embodiments of the present techniques;
• FIG. 2 is a schematic diagram of a modular subsea electrical distribution system, in accordance with an exemplary embodiment of the present techniques;
• FIG. 3 is a schematic diagram of a control and monitoring system for the modular subsea electrical distribution system ofFIG. 2, in accordance with exemplary embodiments of the present techniques;
• FIG. 4 is a block diagram of a subsea circuit breaker and redundant control and monitoring equipment for a modular subsea electrical distribution system, in accordance with exemplary embodiments of the present techniques;
• FIG. 5 is a schematic diagram of a subsea circuit breaker and redundant control and monitoring equipment for a modular subsea electrical distribution system, in accordance with exemplary embodiments of the present techniques;
• FIGS. 6 and 7 are perspective views of a modular subsea circuit breaker assembly for a subsea electrical distribution system, in accordance with exemplary embodiments of the present techniques;
• FIG. 8 is a perspective view of a modular subsea circuit breaker for a modular subsea electrical distribution system, in accordance with exemplary embodiments of the present techniques;
• FIG. 9 is a perspective view of a modular subsea circuit breaker assembly for a modular subsea electrical distribution system, in accordance with exemplary embodiments of the present techniques;
• FIG. 10 is an elevation view of a modular subsea circuit breaker assembly and a pair of power cable harness assemblies having a retractable/extendable connector for a modular subsea electrical distribution system, in accordance with exemplary embodiments of the present techniques;
• FIG. 11 is a perspective view of the power cable harness assembly ofFIG. 10 with the retractable/extendable connector in the retracted position, in accordance with exemplary embodiments of the present techniques;
• FIG. 12 is a perspective view of the power cable harness assembly ofFIG. 10 with the retractable/extendable connector in the extended position, in accordance with exemplary embodiments of the present techniques;
• FIG. 13 is a perspective view of the modular subsea circuit breaker assembly ofFIG. 10 being removed and lifted from the modular subsea electrical distribution system, in accordance with exemplary embodiments of the present techniques;
• FIG. 14 is a perspective view of the power cable harness assembly ofFIG. 10 and an electrical load being removed and lifted from the modular subsea electrical distribution system, in accordance with exemplary embodiments of the present techniques;
• FIG. 15 is a schematic diagram of a subsea modular electrical distribution system for a sea-based wind farm, in accordance with exemplary embodiments of the present techniques;
• FIG. 16 is a simplified schematic diagram of the subsea electrical distribution system, in accordance with exemplary embodiments of the present techniques;
• FIG. 17 is an elevation view of a prior art subsea circuit breaker and bus bar enclosure system
• FIG. 18 is an elevation view of a modular circuit breaker assembly, in accordance with exemplary embodiments of the present techniques;
• FIG. 19 is an elevation view of a penetrator assembly for a modular circuit breaker assembly, in accordance with exemplary embodiments of the present techniques.
• FIG. 20 is a schematic diagram of a subsea system comprising a modular subsea electrical distribution system, in accordance with an alternative embodiment of the present techniques;
• FIG. 21 is a perspective view of a modular subsea circuit breaker assembly, in accordance with an exemplary embodiment of the present techniques; and
• FIG. 22 is an elevation view of a modular subsea electrical distribution system, in accordance with an alternative embodiment of the present techniques.
DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS
• One or more specific embodiments of the present invention will be described below. In an effort to provide a concise description of these embodiments, not all features of an actual implementation are described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill in the art and having the benefit of this disclosure.
• Referring generally toFIG. 1, a system for providing electric power subsea is presented and referenced generally byreference numeral30. In the illustrated embodiment, asurface facility32 provides High voltage alternating current (“HV AC”) electric power and control signals to a subseaelectrical distribution system34 via anumbilical cable36. There is no set voltage value that defines what is “High voltage”. However, in this embodiment, the voltage of HV AC provided by the umbilical is 110 kV AC or greater. In this embodiment, thesurface facility32 is located on land. However, thesurface facility32 may also be an off-shore platform or a vessel, such as a floating production and offloading (“FPO”) vessel. As will be discussed in more detail below, the subsea electrical distribution system is a modular system that may be assembled in different configurations to meet system demands. In the illustrated embodiment, the subseaelectrical distribution system34 is configured to provide power to afirst subsea load38 and asecond subsea load40. The subseaelectrical distribution system34, as well assubsea loads38,40 may be located at extreme distances from thesurface facility32. For example, the subseaelectrical distribution system34 andsubsea loads38,40 may be 150 km or more from thesurface facility32. In addition, the subseaelectrical distribution system34 andsubsea loads38,40 may be located on an ocean floor several thousand feet below the surface of the ocean. Although only twosubsea loads38,40 are shown in this embodiment, it is envisioned that many more subsea loads would receive power through the subseaelectrical distribution system34, rather than receiving power individually from the surface.
• Referring generally toFIG. 2, the subseaelectrical distribution system34 is a modular system having a plurality of circuit breaker modules that may be connected together to form thesystem34. The circuit breaker modules provide thesystem44 with its modularity. The circuit breaker modules may be assembled and connected in a myriad of configurations to meet the demands of the subseaelectrical distribution system34. The circuit breaker modules are provided in the illustrated embodiment to enhance the flexibility and reliability of the subseaelectrical distribution system44.
• In this embodiment, the subseaelectrical distribution system34 comprises a pair of centralcircuit breaker modules42 that are configured to receive power and then distribute the power to a plurality of remotecircuit breaker modules44. The remotecircuit breaker modules44 may be located near the centralcircuit breaker modules42 or at greater distances, such as tens of kilometers away. In this embodiment, the centralcircuit breaker modules42 receive power from a first subsea umbilical46 and a second subsea umbilical48 for reliability. However, a single subsea umbilical may be used. As will be discussed in more detail below, the first and secondsubsea umbilicals46,48 comprise HV AC power cables, High voltage direct current (“HV DC”) power cables, and fiber optic communication cables in this embodiment. As above, the HV AC carried by theumbilicals46,48 in this embodiment is 110 kV AC or greater. However, lower voltages may be provided. As with AC, there is no definitive DC voltage value that defines HV DC. In this embodiment, the HV DC carried by theumbilicals46,48 is between 2-10 kV DC. However, greater or lower DC voltages may be provided. The remotecircuit breaker modules44, in turn, are configured to provide power to a plurality of subsea electric loads50. In the illustrated embodiment, the power received from the first umbilical46 and a second umbilical48 are reduced by a pair of subsea step-downtransformers52. However, power may be received at alower voltage 36 kV), such that subsea step-down transformers are not required.
• In this embodiment, the power received by the subseaelectrical distribution system34 is reduced by a pair of step-downtransformers52 before it is transmitted to the centralcircuit breaker modules42. For example, thesubsea transformers52 may step-down the voltage of the HV AC electrical power from 110 kV AC to 36 kV AC. In this embodiment, the centralcircuit breaker modules42 of the subsea electricalpower distribution system34 comprise a firstcircuit breaker module54 and a secondcircuit breaker module56. However, a single centralcircuit breaker module42 may be used, particularly if only one umbilical is used. In this embodiment, the firstcircuit breaker module54 receives power from the first umbilical46 and the second circuit breaker module receives power from the second subsea umbilical48. The first and secondcircuit breaker modules54,56 comprise a plurality of circuit breakers for selectively supplying electric power. The number of circuit breakers provided in each circuit breaker module may be varied depending upon the system requirements, such as the number of electrical loads to be supplied with power. In the illustrated embodiment, the first and secondcircuit breaker modules54,56 each comprise fivecircuit breaker assemblies57,58,59,60,61. One side of eachcircuit breaker assembly57,58,59,60,61 is connected to acommon bus bar62 and the other side of eachcircuit breaker assembly57,58,59,60,61, the “free side”, may be coupled to a power source or a load depending on the desired configuration. The first and secondcircuit breaker modules54,56 are configured in this embodiment so that the free side ofcircuit breaker assembly57 receives power from one of thesubsea umbilicals46,48. Power passes throughcircuit breaker assembly57 to thebus bar62.Circuit breaker assembly57 is used to selectively connect and disconnect thebus bar62 from power coming from one of thesubsea umbilicals46,48. The free side ofcircuit breaker assemblies58,59,60, and61 of the first and secondcircuit breaker modules54,56 are either coupled to remotecircuit breaker modules44, loads, or not connected to anything for use as a spare.
• The remotecircuit breaker modules44 comprise a thirdcircuit breaker module64 that comprises threecircuit breaker assemblies57,58,59, rather than five. In this configuration, the thirdcircuit breaker module64 is connected to the free side ofcircuit breaker assembly58 of the firstcircuit breaker module54. This enables power to be provided to thebus bar62 of the thirdcircuit breaker module64 from the firstcircuit breaker module54. The free sides ofcircuit breaker assemblies57,58,59 of the thirdcircuit breaker module64 are coupled to loads50. The threecircuit breaker assemblies57,58,59 of the thirdcircuit breaker module64, thus, are operable to selectively connect and disconnect theloads50 and thebus bar62 of the thirdcircuit breaker module64.
• The remotecircuit breaker modules44 are configured to receive power from either subsea umbilical46,48. In this embodiment, the remotecircuit breaker modules44 also comprise a fourthcircuit breaker module66, a fifthcircuit breaker module68, and a sixthcircuit breaker module70.Circuit breaker assembly57 of the fourthcircuit breaker module66 is coupled tocircuit breaker assembly59 of the firstcircuit breaker module54. This enables power to be provided to thebus bar62 of the fourthcircuit breaker module66 from the first subsea umbilical46 viacircuit breaker57 of the fourthcircuit breaker module66. In addition,circuit breaker assembly61 of the fourth circuit breaker module is connected by alink72 tocircuit breaker assembly57 of the fifthcircuit breaker module68.Circuit breaker assembly61 of the fifthcircuit breaker module68 is coupled tocircuit breaker assembly59 of thesecond circuit breaker58. This enables power to be provided to thebus bar62 of the fifthcircuit breaker module68 from the second subsea umbilical48 viacircuit breaker assembly61 of the fifthcircuit breaker module68. Thus, by selectively operatingcircuit breaker assembly57 of the fourthcircuit breaker module66 andcircuit breaker assembly61 of the fifthcircuit breaker module68, power may be provided tobus bars62 of the fourth and fifthcircuit breaker modules66,68 from either the first subsea umbilical46 or the second subsea umbilical48. Alternatively, the sixthcircuit breaker module70 is coupled to both the first and second circuit breaker modules. By selectively operatingcircuit breaker assembly57 andcircuit breaker assembly61 of the sixthcircuit breaker module70, power may be supplied to the bus bar of the sixthcircuit breaker module70 from either the first umbilical46 or the second umbilical48 via the first and secondcircuit breaker modules54,56.
• The subseaelectrical distribution system44 may be used to provide power to a variety ofloads50, rather than routing power directly to eachload50 from the surface. This greatly simplifies power distribution. In this embodiment, each of theloads50 comprises an additional step-downtransformer76 to supply power to a variable speed drive (“VSD”)78. TheVSD78 provides variable speed electric power to amotor80 to drive apump82. Similarly, aload50 may be a variable frequency drive (“VFD”). Thepumps82 may be used to pump fluids from a subsea well to a processing unit, for example. However, the VSDs may be used to drive subsea compressors, as well.
• Referring generally toFIG. 3, operation of the subseaelectrical distribution system34 is controlled by a control andmonitoring system84. In the illustrated embodiment, acomputer system86 is used to enable a user to manage the subseaelectrical distribution system34 via the control and monitoring system's HMI (Human Machine Interface). Thecomputer system86 may be located on-shore or at sea aboard a platform or vessel. Thecomputer86 may be used to transmit the user's close and open circuit breaker orders, automatically vary the speed of the VSDs, and perform other control functions. In addition, sensors may be coupled to thecomputer system86 to provide the user with information to facilitate operation of the subseaelectrical distribution system34 and loads50.
• In the illustrated embodiment, thesubsea umbilicals46,48 also includecommunication lines88, which enable communication between thecomputer system86, the subseaelectrical distribution system34 and loads50. Preferably, thecommunication lines88 are fiber optic cables routed along with HV AC and DC power cables in theumbilicals46,48. Theumbilicals46,48, are terminated at a subsea umbilical termination assembly (“SUTA”)90 in this embodiment. From eachSUTA90,communication lines88 are routed to protection andcontrol modules92 corresponding to each of thecircuit breaker modules54,56,64,66,68,70. Each of the protection andcontrol modules92 has anEthernet switch94 that receives thefiber optic lines88 in the illustrated embodiment. In the illustrated embodiment, the communication is based on use of functionality described IEC 61850. Reports are used to transmit information to the user for monitoring purposes. Control functions are executed by means of Generic Object Oriented Substation Events (GOOSE). GOOSE messages are also used for protection where communication between protection relays is required such as forsubsea cables72,74. The use of IEC 61850 allows all communication required for protection, control and monitoring to transit via the fiber optic cables installed within the umbilicals and subsea cables. This avoids having to install additional cables for protection, monitoring and control.
• In addition, each protection andcontrol module92 comprises aprotection relay96 and one or more programmable logic controller functions (PLCs)98. In addition to the protection functions, theprotection relay96 also comprises monitoring equipment for the subseaelectrical distribution system34, such as circuit breaker conditions, and the plurality ofloads50. The PLC functions98 are used to control thecircuit breaker assemblies58,60. Theprotection relay96 is operable to provide a signal to the PLC functions98 to trip the circuit breakers when an undesired condition is reached, such as an overload condition. The protection relay provides direct tripping of the circuit breaker for electrical faults. The Ethernet switch94 routes communications between thecomputer system86, theprotection relay96, and the PLC functions98. The PLC functions can be housed in discrete pieces of equipment or can be integrated into another electronic device such as a protection relay. The “PLC” function can have different embodiments.
• Referring generally toFIGS. 4 and 5, detailed views of the firstcircuit breaker module54 and its corresponding protection andcontrol module92 are presented.Circuit breakers assembly57 comprises acircuit breaker102. Similarly,circuit breaker assembly58 comprises acircuit breaker104. In the illustrated embodiment, each of thecircuit breakers assemblies57,58 is connected to two protection andcontrol modules92 for redundant protection: afirst control unit106 and asecond control unit108. Thefirst control unit106 andsecond control unit108 are operable to selectively open andclose circuit breakers102,104. If onecontrol unit106,108 fails, theother control unit108,106 can still selectively open and close bothcircuit breakers102,104. Each protection andcontrol module92 has a main relay and an auxiliary relay function that control the opening and closing ofcircuit breakers102,104. For example, thefirst control unit106 has amain relay function110 and anauxiliary relay function112. Similarly, thesecond control unit108 has amain relay function114 and anauxiliary relay function116. The main relay function of a control unit is connected to one circuit breaker, while the auxiliary relay function is connected to a second circuit breaker. For example,main relay function110 of thefirst control unit106 is connected tocircuit breaker102 and theauxiliary relay112 is connected tocircuit breaker104. Similarly,circuit breaker104 is connected to themain relay function110 ofcontrol unit106 and theauxiliary relay function116 ofcontrol unit108. Ifcontrol unit106 fails,circuit breaker102 can still be controlled byauxiliary relay function116 ofcontrol unit108. In the illustrated embodiment the main relay function and the auxiliary relay function are housed in the same piece of equipment, known as a control unit.
• As best illustrated inFIG. 5, circuit breakers are opened and closed by closing coils and trip coils, respectively. Each circuit breaker assembly has a spring-charged mechanism for opening and closing the circuit breaker and the circuit breaker closing coils and trip coils control the spring-charged mechanism. If a circuit breaker is open and the closing coil is energized, the spring-charged mechanism will close the circuit breaker. Similarly, when the circuit breaker is closed and the trip coil is energized, the spring-charged mechanism will open the circuit breaker. In the illustrated embodiment, each circuit breaker has redundant trip coils and closing coils. Surface circuit breakers have only a single closing coil. However, because of the difficulty in removing a circuit breaker module from subsea if the closing coil were to fail, two closing coils are provided in each circuit breaker in this embodiment.Circuit breaker assembly57 has afirst trip coil118 and afirst closing coil120 that are connected to themain relay function110 ofcontrol unit106. In addition,circuit breaker assembly57 has asecond trip coil122 and asecond closing coil124 that are connected to theauxiliary relay function116 of thesecond control unit108. Eithertrip coil118,122 can open thecircuit breaker102 and either closingcoil120,124 can close thecircuit breaker102. A first electric motor126 and a second electric motor127 having separate power supplies are provided to energize the spring-chargedmechanism128 when the spring is discharged. A surface circuit breaker has only a single motor126. However, because of the difficulty in repairing/replacing a subsea circuit breaker if the motor126 fails, motors126,127 with separate power supplies are provided for reliability in this embodiment.
• Referring generally toFIGS. 4 and 5, the protection andcontrol modules92 also are connected to sensors within thecircuit breaker assemblies57,58. For example, themain relay function110 of thefirst control unit106 is connected to a first set of phasecurrent sensors130 and a first zero-sequencecurrent sensor132. Theauxiliary relay function114 of thesecond control unit108 is connected to a second set of phasecurrent sensors134 and a second zero-sequence current sensor136. Similarly, themain relay function114 of thesecond control unit108 is connected to a first set of phasecurrent sensors138 and a first zero-sequencecurrent sensor140 associated with the secondcircuit breaker assembly58. Theauxiliary relay function112 of thefirst control unit106 is connected to a second set of phasecurrent sensors142 and a second zero-sequencecurrent sensor144 associated with thesecond circuit breaker58.
• Referring generally toFIGS. 6 and 7, an embodiment of a modular subseacircuit breaker assembly146 for housing acircuit breaker assembly147 for use in the subseaelectrical distribution system34 ofFIGS. 1-5 is presented. Thecircuit breaker assembly147 is housed within a water-tight enclosure148. Theenclosure148 protects the internal components from seawater. One end of theenclosure148 has agas sealing barrier149 and the other end has a circuit breakeroperating mechanism enclosure150. The circuit breakeroperating mechanism enclosure150 has a series ofconnections151 for connection to the control andmonitoring system84. In addition, theenclosure148 has three sealedopenings152 called “penetrators” to which each phase of a three-phase power cable may be connected for connection to thecircuit breaker assembly147. In addition, in this embodiment, theenclosure148 is filled with sulfur hexafluoride (SF₆) gas to a pressure of two atmospheres for electrical insulation between thecircuit breaker assembly147 and theenclosure148.
• In the illustrated embodiment, thecircuit breaker assembly147 is a three-phase circuit breaker. Each phase of the three-phase power has its owncircuit breaker pole153. Within eachcircuit breaker pole153 is SF₆gas to quench arcing between contacts when opening and closing the circuit breakers due to the large voltages utilized in the subseaelectrical distribution system34. A circuit breaker pole using vacuum for arc quenching can also be used. External electrical power cables are connected to thepenetrators152 on theenclosure148 for internal connection to threeterminals154 on thecircuit breaker assembly147. Eachcircuit breaker pole153 has aconductor155 that extends through thegas sealing barrier149 of theenclosure148 into a bus bar compartment to which the modularcircuit breaker assembly146 is secured.
• Referring generally toFIG. 8, an embodiment of the firstcircuit breaker module54 is presented. In this embodiment, the firstcircuit breaker module54 comprises five modularcircuit breaker assemblies146 connected to abus bar assembly162 housing the bus bar59 (not shown). Thebus bar assembly162 is comprised of twoend assemblies164 connected to acentral assembly166. However, additionalcentral assemblies164 may be connected together to extend thebus bar assembly162. The interior of thebus bar assembly162 is insulated with SF₆gas in this embodiment. As will be discussed in more detail below, the use of SF₆gas for insulation, rather than oil, enables a smallerbus bar assembly162 to be used, as well as requiring fewer penetrations through barriers that have to withstand differential pressure. Each of the modularcircuit breaker assemblies146 has aconnector168 for connecting to a power cable. Each of theconnectors168 is connected to apenetrator152 which seals the opening in theenclosure148.
• In the illustrated embodiment, the firstcircuit breaker module54 comprises a first modularcircuit breaker assembly170, a second modularcircuit breaker assembly172, a third modularcircuit breaker assembly174, a fourth modularcircuit breaker assembly176, and a fifth modularcircuit breaker assembly178. In this embodiment, circuit breaker57 (not shown) is housed within the first modularcircuit breaker assembly170. Circuit breaker58 (not shown) is housed within the second modularcircuit breaker assembly172. Circuit breaker59 (not shown) is housed within the third modularcircuit breaker assembly174. Circuit breaker60 (not shown) is housed within the fourth modularcircuit breaker assembly174. Finally, circuit breaker61 (not shown) is housed within the fifth modularcircuit breaker assembly176. Opposite the third modularcircuit breaker assembly174 is a spare space for an additional modular circuit breaker assembly. This would bring the total number of circuit breakers to six if this spare space was used.
• Referring generally toFIG. 9, the firstcircuit breaker module54 is housed within a supportingstructure180 in the illustrated embodiment. The supportingstructure180 comprises a frame182 in which the firstcircuit breaker module54 is supported. In addition, the supportingstructure180 is adapted to route power to and from each of the modularcircuit breaker assemblies146 of the firstcircuit breaker module54. The firstcircuit breaker module54 is configured by routing power either to or from each modularcircuit breaker assembly146.Connector assemblies184 are disposed around theframe182. The supportingstructure180 also comprises a plurality ofpower cables186 that extend between theconnector assemblies184 and theconnectors168 on thecircuit breaker assemblies170,172,174,176,178 to route power to and from the modularcircuit breaker assemblies170,172,174,176,178. Eachconnector assembly184 is configured with three wetmate power connectors188 together with alignment guides190. The alignment guides190 align thepower connectors188 with a corresponding external wet mate connector assembly (not shown). Eachpower cable186 is routed between a wetmate power connector188 and awet mate connector168 on acircuit breaker assembly170,172,174,176,178 in this embodiment. In addition, the supportingstructure180 has a plurality ofguides191 for alignment purposes. Acable clamp192 is mounted on the circuit breaker module to support the cable at itsconnection168. The clamp192 is designed to securely hold the cable at varying external pressures from sea level to the final installation depth under water.
• Referring generally toFIGS. 10-12, in the illustrated embodiment, eachcircuit breaker assembly170,172,174,176,178 is connected to an external component of the subsea electrical distribution network via asubsea cable208 by connecting acable harness assembly200 having a set ofwet mate connectors202 that may be extended and retracted to that modular circuit breaker assembly'sconnector assembly184. Theconnector202 ofFIG. 11 and the left side ofFIG. 10 is shown in the retracted position. Theconnector202 ofFIG. 12 and the right side ofFIG. 10 is shown in the extended position. In this embodiment, thecable harness assembly200 also comprises aframe204, and acable harness206 for securingpower cables208 to thecable harness assembly200. Theframe204 has a plurality ofguides209 for alignment purposes.
• To connect thepower cables208 of thecable harness assembly200 to the circuitbreaker module assembly180, theframe204 of thecable harness assembly200 is disposed adjacent to theframe182 of the circuitbreaker module assembly180 so that theconnector202 is generally aligned with, and proximate to, theconnector assembly184. In this embodiment, theframe182 of the circuitbreaker module assembly180 and theframes204 of thecable harness assemblies200 are disposed on atemplate210. Thetemplate210 has guideposts (not shown) configured to receive theguides191 in theframe182 of the supportingstructure180 and theguides209 of thecable harness assemblies200 so that thecable harness assemblies200 and supportingstructure180 are in proper alignment. Each cable harness assembly is independent of theframe182 and all other cable harnesses.
• An ROV (not shown) is used to extend theconnector202 towards theconnector assembly184 of thecircuit breaker module180 to make the connection. Thecable harness assemblies200 have aconnector guide assembly211 comprising a fixedportion212 secured to theframe204 and amovable portion213 secured to thepower cables208. The ROV (not shown) may secure to theframe204 and grab themovable portion213 and either pull or push themovable portion213, andpower cables208, relative to the frame to retract or extend theconnectors202. As theconnector200 is extended, guide pins214 on theconnector200 engage theguides190 on theconnector assembly184 of the circuitbreaker module assembly180. The engagement between the guide pins214 and theguides190 brings thewet mate connectors214 of theconnector200 into alignment withwet mate connectors188 of the firstcircuit breaker module54. Eventually, as theconnector202 is extended, theconnectors214 of theconnector202 of thecable harness assembly200 connect to theconnectors188 of the first circuitbreaker module assembly54, electrically coupling thepower cables208 to thecables186 of the supportingstructure180 of the first circuitbreaker module assembly54. Similarly, to disconnect thepower cables208 of thecable harness assembly200 from the circuitbreaker module assembly180, an ROV (not shown) is used to retract theconnector202 to disengage from theconnector assembly184 of the supportingstructure180 of the firstcircuit breaker module54.
• Referring generally toFIG. 13, because thecable harness assemblies200 are selectively connectable to the supportingstructure180, a circuitbreaker module assembly180 may be removed from the subseaelectrical distribution system34 for repair/modification without requiring removal ofloads50 orother cables208 routed to and from the circuit breaker modules. In this view, the circuit breaker module and supportingstructure180 are guided into and out of position by anROV219 on to thetemplate210. In addition, thecable harness assemblies200 may be disconnected to facilitate fault detection. For example, after aconnector202 has been disconnected, an ROV may connect to theconnectors202 to perform test to identify if a fault exists in thepower cable208 or if the fault exists in thecircuit breaker module54. Alternatively, the ROV can check power cable electrical characteristics.
• Referring generally toFIG. 14, similarly, acable harness assembly200 and connected cable208 (not shown) may be removed from the subseaelectrical distribution system34 for repair/modification without requiring removal of the first circuitbreaker module assembly54 orother cables208 routed to and from the circuit breaker module. To remove acable harness assembly200 from the subseaelectrical distribution system34, the retractable/extendable connector202 for itscable harness assembly200 is retracted; this disconnects thecable harness assembly200 andconnected cable208 from the circuitbreaker module assembly180. Thecable harness assembly200, and thecables208 connected to thecable harness assembly200 may then be raised to the surface for repair/modification. Thecable harness assembly200 is guided into and out of position by the ROV onto thetemplate210. If theload50 remains connected to thecable208 then it may be raised to the surface for repair/modification together with thecable harness assembly200 andconnected cable208.
• Referring generally toFIG. 15, awind farm250 having a modular subseaelectrical distribution network252 is presented. In the illustrated embodiment, thewind farm250 comprises a plurality of wind turbine-generators254. In this embodiment,groups256 of wind turbine-generators254 are electrically connected to a “local” modular subseacircuit breaker assembly258. The modular subseacircuit breaker assemblies258 have the features and characteristics as described above in respect toFIGS. 2-14, as described above. In this embodiment, each wind turbine-generator254 is connected to acorresponding circuit breaker260 within a modular subseacircuit breaker assembly258. In turn,groups262 of modular subseacircuit breaker assemblies258 are connected to a “regional” modular subseacircuit breaker assembly264. The “regional” modular subseacircuit breaker assemblies264 are connected to a “central hub” modular subseacircuit breaker assembly266. The “central hub” modular subseacircuit breaker assembly266 is connected to a step-uptransformer268 to increase the voltage of the power generated by the wind turbine-generators254 to a high-voltage for transmission over a subsea umbilical270 to ashore facility272.
• Referring generally toFIG. 16, in addition to HV AC power and communications lines, the subseaelectric system30 also couples HV DC to, and through, the subseapower distribution system34. In this embodiment, HV DC is typically between 2 kV and 10 kV. Previously, HV DC was coupled to subsea loads in either a separate umbilical or produced subsea from HV AC transmitted subsea via an umbilical. However, in the illustrated embodiment, the first umbilical46 is configured with HV AC power cables, HV DC power cables, and fiber optic cables for communication. At theSUTA90, HV AC power is coupled from the umbilical46 to provide power toloads50 via a HVAC power cable300. In addition, HV DC power is coupled from the umbilical46 to a protection andcontrol module92 by a HVDC power cable301. Finally, communication capability is coupled from the umbilical46 to the protection andcontrol module92 by afiber optic cable302. Communication capability is provided to processequipment303 from the protection andcontrol modules92 via afiber optic cable302 and asubsea communication interface304. In addition, the protection andcontrol module92 provides DC auxiliary power to the process equipment via an auxiliaryDC power cable305.
• Referring generally toFIG. 17, a representative subsea breaker and bus bar assembly is disclosed, and represented generally byreference numeral310. The illustratedassembly310 has afirst circuit breaker312 and asecond circuit breaker314. Thefirst circuit breaker312 has anenclosure316 and thesecond circuit breaker314 has anenclosure318. The interiors of bothenclosures316,318 is pressurized with SF₆gas320. The pressure of thegas320 may be near atmospheric pressure. Therefore, there will be a large differential pressure between the interior of theenclosures316,318 and theseawater322 pressure surrounding theassembly310 when theassembly310 is located subsea. Theassembly310 also comprises abus bar324 housed within a two-stagepressure compensation housing325. Thebus bar324 is housed within afirst enclosure326. Thefirst enclosure326, in turn, is housed within asecond enclosure328. Thefirst enclosure326 is filled with afirst oil330 and thesecond enclosure328 is filled with asecond oil332. The viscosities of theoils330,332 may vary. The pressure compensation reduces, if not eliminates, the pressure differential between the interior of thefirst enclosure326 andseawater322. However, it produces a pressure differential between theoil330 within the interior of thefirst enclosure326 and the SF₆gas320 within the interior of thecircuit breaker enclosures316,318, which may lead to leaks of oil into the interior of thecircuit breaker enclosures316,318. In addition, this requires two sealed penetrations, a first penetration334 and asecond penetration336, to connect to thebus bar324, creating potential leak paths.
• Referring generally toFIG. 18, a simplified drawing ofcircuit breaker module54 ofFIG. 8 is presented. In this embodiment, rather than pressure compensating theinterior338 of thebus bar assembly162 to seawater pressure, theinterior338 of thebus bar assembly162 is pressurized with SF₆gas320 to a pressure of two atmospheres. The SF₆gas320 is a better electrical insulator thanoil330,332. Therefore, theinterior338 of thebus bar assembly162 requires less volume for electrical insulation between thebus bar62 and theenclosure340 of thebus bar assembly162. Thus, the size of theenclosure340 may be reduced. In addition, the differential pressure between the gas-filledinterior338 of thebus bar assembly162 and the gas-filledinterior342 of thecircuit breakers assemblies168,170 is reduced, if not eliminated, reducing potential for leaks between thebus bar assembly162 and thecircuit breaker assemblies168,170. This also reduces the number of sealedpenetrations344 needed between thebus bar62 and acircuit breaker57,58 by one, reducing potential leak paths.
• Referring generally toFIG. 19, an embodiment of apenetrator344 is presented. In this embodiment, aconductor155 from acircuit breaker57,58, etc., extends through anopening346 in thepressure barrier149 between the interior and exterior gas or fluids at various pressure ratings. In this embodiment, thepenetrator344 comprisesinsulation348 surrounding theconductor155 and abody350 that completes the seal against theopening346 in thepressure barrier149. Thebody350 also comprises aboot352. In this embodiment, theboot352 also comprises a firstcurrent sensor354 and a second current sensor356 integrated into theboot352. Thecurrent sensors354,356 comprise asensor core358, a sensor winding360, andsensor insulation362. Thecurrent sensors354,356 may be current transformers.
• Referring generally toFIG. 20, a subsea system is presented and represented generally byreference numeral400. In this embodiment, thesubsea system400 comprises a modular subseaelectrical distribution system402 operable to provide HV AC, Low voltage alternating current (“LV AC”), HV DC, Low voltage direct current (“LV DC”), and fiber optic communication lines to power and control subsea loads.
• In the illustrated embodiment, a HVAC power cable300, a HVDC power cable301, and a fiberoptic communication line302 are coupled to a modular HV Subsea Substation (“HVSS”)404 comprising acircuit breaker module406 and a protection andcontrol module408. The HVAC power cable300 is coupled to the subseacircuit breaker module406. The subseacircuit breaker module406 comprisescircuit breaker assemblies57,58,59,60,61, and abusbar assembly62, as described above inFIG. 2. The HVDC power cable301 and fiberoptic communication line302 are coupled to a control andmonitoring module408. In this embodiment, the control andmonitoring module408 comprises a HV DC power and fiber opticcommunication line interface410. DC power and communication signals are coupled to a protection andcontrol module412. The protection andcontrol module412 is, in turn, coupled to thecircuit breaker module406. The protection andcontrol module412 is similar to protection andcontrol module92 described above inFIGS. 3-5.
• In this embodiment, the subseaelectrical distribution system402 comprises a LV subsea distribution (“LVSD”)module414 operable to supply LV AC power to various loads from the HV AC power and/or the HV DC power supplied by the umbilical46. HV AC power from the HVSS is coupled to asubsea transformer416 viacircuit breaker assembly61. Thetransformer416 steps-down the HV AC from approximately 33 kVAC to approximately 690 VAC, which is coupled to theLVSD module414. The illustrated embodiment of theLVSD module410 comprises afirst busbar assembly418 and asecond busbar assembly420 coupled together by a cross-connectcircuit breaker assembly422. LV AC power from thetransformer416 is coupled to thefirst busbar assembly418 by a first inletcircuit breaker assembly424. LV AC power is supplied to thesecond busbar assembly420 from an uninterruptable power supply (“UPS”)module426 through acircuit breaker assembly428 in theLVSD module414. The UPS receives HV DC power and fiber optic communication lines from the HV DC power and fiber opticcommunication line interface410. In addition, in the illustrated embodiment, theUPS module426 comprises anemergency battery430 operable to provide emergency DC power if power from the umbilical46 is lost. TheUPS module426 comprises a DC to AC power supply432 that converts DC power from either the umbilical46, via the communication andmonitoring module408, or theemergency battery430 to LV AC. In addition, theUPS module426 comprises a DC toDC power supply434 for providing DC power to loads from either umbilical, via the communication andmonitoring module408, or theemergency battery430
• TheLVSD module414 comprises a plurality ofcircuit breaker assemblies436. Some of the circuit breaker assemblies are coupled to thefirst busbar assembly418 and some are coupled to thesecond busbar assembly420. Depending upon the position of the cross-connectcircuit breaker assembly422, power may be supplied to thecircuit breaker assemblies436 from theHVSS404 and/or theUPS module426. In this embodiment, the power supplied by theUPS module426 is considered as “Secure Power” meaning that it is available when the normal AC power has failed. In this embodiment, during normal operation, thecross-connect circuit assembly422 is open andcircuit breaker assembly428 is closed so that the circuit breaker assemblies are supplied power by theHVSS404 and the UPS432. However, when there is a loss of power from the UPS module432, the cross-connect422 is closed andcircuit breaker assembly428 is opened so that the AC power from theHVSS404/umbilical46 may supply power to critical loads that must remain energized. In this embodiment, eachcircuit breaker assembly436 couples power to subsea loads via anisolation transformer438. The outgoing circuits of theLVSD module426 are provided withisolation transformers438 in order to allow loads to continue to be supplied should an earth fault occur on the load side of theisolation transformer438.
• The monitoring and control of the devices within theLVSD module414 is performed viafiber optic cables302 connected to theCMM408. In addition, sensors installed on the step-downtransformer416 are connected to the LVSD module viasubsea cable440. TheLVSD module414 converts signals from these sensors to optical signals for transmission via thefiber optic cables302 connecting theLVSD module414 to theCMM408 and, thus, to other subsea equipment and the shore station.
• Thesubsea system400 also comprises asubsea heating system442. The subseaelectrical distribution system402 comprises a heat tracing module (“HTM”)444 for supplying LV AC power to theheating system442. TheHTM444 is a LV AC switchgear module dedicated to thesubsea heating system442. High powersubsea heating circuits446 used for initial heating are supplied by theHVSS404 via apower cable450 coupled to thefirst busbar418 of theLVSD module414.Lower power circuits448 used for maintaining a temperature are supplied by apower cable452 coupled to thesecond busbar420 of theLVSD module414 and, therefore, may be supplied by theUPS module426 if power from theHVSS404 is lost. TheHTM444 also comprises a plurality ofisolation transformers454. Theisolation transformers454 in theHTM444 are used for two purposes. The first purpose is to allow continued operation in case of an earth fault on the load side of thetransformer454. The other purpose is to adapt the output voltage to that required by theheating system442. For example, theheating system442 may require voltages of greater than 1000 V AC. This second purpose may be a new idea for a subsea heating power supply. TheLVSD module414 also communicates with theHTM442 viafiber optic cables302. This allows theHTM444 to be monitored and remotely controlled in the same manner as theLVSD module414. Similarly any sensors in theheating system442 can be connected to devices within theHTM444 and converted to optical signals for transmission to other subsea equipment or to the shore station.
• LV AC also is supplied to aVFD assembly456 in this embodiment. TheVFD assembly456 receives main HV AC power form theHVSS404. In the illustrated embodiment, LV AC from thefirst busbar418 of theLVSD module414 is provided to theVFD assembly456 to power a pre-charge and pre-magnetization transformer458 located within theVFD assembly456. This transformer458 must be energized before main AC power from the HVSS is energized. In previous subsea VFD systems, power to a pre-charge and pre-magnetization transformer of a VFD was provided from a subsea or topside UPS. In this embodiment, only normal AC power is required, not secure power. LV AC power from theHVSS404 via thefirst busbar418 is provided tosecondary functions460. Secure power from thesecond busbar420 is provided toprimary functions462, such as the control electronics of the VFD and for cooling fans, if provided. Apower cable464 is provided to couple LV AC power from thefirst busbar418 to the secondary functions and aseparate power cable466 is provided to couple secure LV AC power from thesecond busbar420 to themain functions462.
• Thesubsea system400 also comprises a magnetic bearing module (“MBM”)480, which supplies power to amagnetic bearing482 for a rotating device. TheVFD456 is used to power anelectric motor80, which, in turn, may be used to drive a number of different rotating devices, such as asubsea pump483 orsubsea compressor484. Thesubsea pump483 may be used to pump production fluids from a subsea well to a platform, vessel, or shore facility. Thesubsea compressor484 may be used to compress production gases from a subsea well, which may be piped to a platform, vessel, or shore facility. Themagnetic bearing482 provides support for the rotating shafts of the rotating devices powered by theVFD456. In this embodiment, theMBM480 may receive DC power from theUPS module426 or LV AC from theLVSD module414. ADC power cable486 couples DC power from theUPS module426 to theMBM480. AnAC power cable488 couples AC power from theLVSD module414 to theMBM480.
• In the illustrated embodiment, thesubsea system400 comprises a subsea control module (“SCM”)500. TheSCM500 controls the subsea production and processing equipment. In this embodiment, theSCM500 comprises a subsea electrical module (“SEM”)502. In previous designs, theSCM500 and its embodiedSEM502 received power directly from a shore facility via a separate power cable. In this embodiment,main function controller504 of theSEM502 receives secure power from thesecond busbar420 of theLVSD module414.Secondary function controller506 receives power from thefirst busbar418 of theLVSD module414. As noted above, secure power from thesecond busbar420 of theLVSD module414 may be LV AC power stepped-down from the HV AC power of the umbilical46 or AC power converted either from the HV DC power in the umbilical46 oremergency battery430 in theUPS module426. Apower cable510 is provided to couple LV AC power from thefirst busbar418 to thesecondary function controller506 and a separate power cable512 is provided to couple secure LV AC power from thesecond busbar420 to themain function controller504.
• In addition, the subseaelectrical distribution system402 provides power to motor-operated valves and actuators, represented generally byreference numeral520. One or more of the motor-operated valves andactuators520 may be powered by LV AC from thefirst busbar418 of theHVSS414. In addition, one or more of the motor-operated valves andactuators520 may be powered by secure power from thesecond busbar420 of theLVSD module414. Secure power may be LV AC power stepped-down from the HV AC power of the umbilical46 or AC power converted either from the HV DC power in the umbilical46 oremergency battery430 in theUPS module426. Apower cable522 is provided to couple LV AC power from thefirst busbar418 to the motor-operated valves andactuators520 and aseparate power cable524 is provided to couple secure LV AC power from thesecond busbar420 to the motor-operated valves andactuators520.
• In addition, in this embodiment, the subseaelectrical distribution system402 provides power to asubsea tree530 via a power cable532. Thesubsea tree530 monitors and controls the production of fluids from a subsea well. Thesubsea tree530 is secured to a subsea wellhead (not shown) of a completed subsea well. Thesubsea tree530 has valves that control the flow of fluids flowing from the subsea well or gas or water injected into the subsea well. In this embodiment, the valves controlling flow to, from, and through thesubsea tree530 are operated using electric operators powered from the power cable532 of the subseaelectrical distribution system402. However, the electric operators may be powered with DC power from theDC module426. In addition, afiber optic cable302 is routed to thesubsea tree530 to enable thesubsea tree530 to be controlled from the surface.
• Referring generally toFIG. 21, an embodiment of a modular subsea circuit breaker assembly for use with the subsea electrical distribution system described above is presented and represented generally byreference numeral700. In this embodiment, a subseacircuit breaker assembly702, such as one of thecircuit breaker assemblies54,56,64,66,68,70 ofFIG. 2, is supported by aframe704. In addition, a protection andcontrol module706, such as protection andcontrol module92 ofFIG. 3, is supported by aframe708. The protection andcontrol module706 may be connected to thecircuit breaker assembly702 by disposing the protection andcontrol module706 andframe708 proximate to thecircuit breaker assembly702 andframe704 and connecting cables between the protection andcontrol module706 and thecircuit breaker assembly702. Either the protection andcontrol module706 orcircuit breaker assembly702 may be replaced by disconnecting the cables connecting them together and lifting the device to be replaced to the surface. A replacement device may be lowered to the position of the original device and the electrical cable re-connected. Subsea cables and flying leads are connected and disconnected by means of an ROV (not shown).
• Referring generally toFIG. 22, an alternative embodiment of a modular subseaelectrical distribution system800 is presented. As above, thebusbar assembly800 comprises abusbar802 housed within a sealedhousing804. Also as above, thehousing804 is pressurized with SF₆gas. However, in this embodiment, an inputelectrical power cable806 is connected directly to thebusbar802, rather than to a supply-side circuit breaker, such ascircuit breaker57 inFIG. 2. Thecable806 extends through a sealedpenetration808 in thehousing804. The end of thecable806 opposite thebusbar802 is connected to anelectrical connector810. Circuit breaker assemblies may be connected to thebusbar802 to couple power from thebusbar802 to electrical loads. Alternatively, additionalelectrical cables806 may be connected directly to thebusbar802 and routed to supply electrical loads. Thebusbar housing804,cable806, cableelectrical connector810, etc., are supported by aframe812.
• As noted above, one or more specific embodiments of the present invention were provided above. In an effort to provide a concise description of these embodiments, not all features of an actual implementation were described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill in the art and having the benefit of this disclosure.

Claims (17)

What is claimed is:

1. A subsea electrical device, comprising:

a subsea enclosure having an opening through a wall of the enclosure;

a conductor extending through the opening in the wall of the enclosure; and

a penetrator forming a seal between the conductor and the wall of the enclosure, the penetrator comprising:

a sealing boot configured to form a seal against the wall of the enclosure; and

a current sensor operable to produce a signal representative of current flowing through the conductor.

2. The subsea electrical device ofclaim 1, comprising a subsea busbar disposed in the subsea enclosure, the conductor being electrically coupled to the subsea busbar.

3. The subsea electrical device ofclaim 2, comprising sulfur hexafluoride (SF₆) gas to pressurize the subsea enclosure.

4. The subsea electrical device ofclaim 2, comprising a subsea circuit breaker disposed externally to the enclosure, the conductor extending through the opening in the enclosure to electrically coupled the subsea circuit breaker to the busbar.

5. The subsea electrical device ofclaim 1, comprising an insulator disposed around the conductor, the sealing boot extending around the insulator.

6. The subsea electrical device ofclaim 5, wherein the current sensor is disposed within the sealing boot.

7. The subsea electrical device ofclaim 6, wherein the current sensor comprises a current transformer.

8. A subsea electrical assembly, comprising:

a subsea electrical device;

a subsea enclosure housing the subsea electrical device, wherein an opening is formed in the subsea enclosure;

a conductor extending through the opening in the subsea enclosure and electrically coupled to the subsea electrical device; and

a penetrator forming a seal between the conductor and the opening in wall of the enclosure, the penetrator comprising:

a sealing boot configured to form a seal against the wall of the enclosure; and

a current sensor operable to produce a signal representative of current flowing through the conductor.

9. The subsea electrical assembly ofclaim 8, comprising an insulator disposed around the conductor, the sealing boot extending around the insulator.

10. The subsea electrical assembly ofclaim 8, wherein the current sensor is disposed within the sealing boot.

11. The subsea electrical device ofclaim 10, wherein the current sensor comprises a current transformer.

12. The subsea electrical assembly ofclaim 8, comprising a second current sensor operable to produce a signal representative of current flowing through the conductor, the current sensor being oriented on a first side of the enclosure and the second current sensor being disposed on a second side of the enclosure.

13. The subsea electrical device ofclaim 8, wherein the current sensor is coupled to a subsea protection circuit.

14. The subsea electrical device ofclaim 8, wherein the subsea electrical device comprises a subsea circuit breaker.

15. The subsea electrical device ofclaim 14, wherein the current sensor is coupled to a subsea protection circuit operable to control operation of the subsea circuit breaker.

16. A subsea penetrator assembly, comprising:

an electrical insulator configured to extend around a conductor extending through an opening;

a boot configured to surround the insulator and seal the opening in the enclosure; and

a current sensor disposed within the boot, the current sensor being operable to produce a signal representative of current flowing through the conductor.

17. The subsea penetrator assembly ofclaim 16, wherein the current sensor comprises a current transformer.

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