Open Industrial Workshop Technical Requirements for Subsea High Voltage Direct Current Connectors

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1 Open Industrial Workshop Technical Requirements for Subsea High Voltage Direct Current Connectors RPSEA Project GE Global Research Nov 19, 2014 Imagination at work.

2 Safety Minute 2

3 Agenda Date: November 19, 2014 (Houston) 7:15 7:45 Welcome (Coffee and light breakfast) Qin Chen/Jeff Sullivan (GE) James Pappas (RPSEA) 7:45 8:15 Project introduction Qin Chen (GE) Update on preliminary study (UDW 8:15 9:45 requirement, electrical system, connector specs) 9:45 10:00 Break Qin Chen (GE) Xu She (GE) 10:00 11:00 Discussion General needs for subsea processing All participants 11:00 11:30 Discussion Electrical systems All participants 11:30 12:30 Lunch & GE introduction Jeff Sullivan (GE) 12:30 13:15 Discussion Electrical systems (continued) All participants 13:15 14:15 Discussion Connector requirements All participants 14:15 15:00 Wrap up All participants 3

4 Participants Organization BP Chevron ExxonMobil GE Oil & Gas GE Global Research NETL RPSEA Shell Statoil TOTAL Name Michael Scroggins Lyndon Bowen, David Wendt (DORIS) Xiaolei Yin, Kevin Corbett Svend Rocke, Aslaug Melbo, Gorm Sande, Jan Erik Elnan-Knutsen Paul Doucette (GE Corporate) Qin Chen, Jeff Sullivan, Di Zhang Xu She, Rui Zhou, Joe Suriano, Weijun Yin, Konrad Weeber, Ibrahima Ndiaye, Liwei Hao, Rob Sellick, Pat Irwin, Gary Yeager, Chris Calebrese Michael Vanderwerken Roy Long, Bill Fincham, Gary Covatch James Pappas David Liney Jeswin Joseph Khalid Mateen 4

5 Acknowledgement The material contained in this presentation is based upon work supported by the Department of Energy, and RPSEA under RPSEA Subcontract and DOE Prime Contract DE-AC-07NT

6 Contacts Principal Investigator: Qin Chen GE Global Research Project Manager: Bill Fincham Technical Coordinator: James Pappas (281)

7 Project Introduction

DC for subsea processing: Drivers for subsea processing New Fields Long offsets Deeper waters Complex reservoir Brown fields Increased production rates Increased recovery Removal of

8 DC for subsea processing: Drivers for subsea processing New Fields Long offsets Deeper waters Complex reservoir Brown fields Increased production rates Increased recovery Removal of topside facilities DC for long distance, high power, Subsea DC connectors Subsea available (AC connectors) DC available (land-based) Subsea + DC not available Gas/ Oil Power Control Chemicals 8

9 DC for long distance and high power Cable Transmission capability (MW) Power [MW] kv 185 mm 2 88 kv 240 mm 2 88 kv 300 mm 2 88 kv 400 mm Distance [mi] Voltage limit Length of the cable (mile) Example of AC Power transfer capability vs Distanc *Cable too long -> most of the AC current needs to charge/discharge cable capacitor Two ways to reduce/eliminate transmission loss are: Additional compensation for reactive power Make ω 0: LF AC or DC 9

10 Subsea cable connectors: AC vs. DC Insulation AC Insulation Field is capacitive graded, i.e., determined by dielectric constant, which for typical ac insulation, is nearly independent of field & temperature : Field distortion by space charge is a secondary effect Aging and life data available for AC insulation, including field experiences with subsea installations Electrical stress distribution in connector is insensitive to cable properties DC Insulation Field is resistive graded, i.e., determined by electric conductivity, which is strongly (and nonlinearly ) field- & temperature- dependent: (E,T)= 0 e T+ E Space charge (both trapped and mobile charges) could significantly alter local field, and might lead to early insulation failure Limited aging and life data available for DC insulation, especially under influence of subsea conditions; lacking field data Electrical stress distribution in connector can be highly sensitive to cable properties Mechanical challenges cannot be overlooked! 10

Types of connectors Dry Mate Connector (DM) Submerged in sea water Connected/disconnecte d at topside Typically the split is made between a barrier part and a cable termination part (wall of the

11 Types of connectors Dry Mate Connector (DM) Submerged in sea water Connected/disconnecte d at topside Typically the split is made between a barrier part and a cable termination part (wall of the power consumer is not opened) Wet mate connector Wet Mate Connector (WM) Submerged in sea water, Connected/disconnecte d in a submerged condition. Example of arrangement (with topside VSD): Penetrator (PEN) Enables HV conductors to pass through a partition such as a wall or a tank The means of attachment flange or fixing device, to the partition, forms part of the penetrator. Includes bulkhead mounted connector assembly components. Includes a cable termination, attaching the cable to the penetrator. Connection typically made in a controlled environment. PEN PEN WM WM DM DM PEN 11

12 Electric field in wet mate connector AC vs. DC Cable termination AC Oil Epoxy Steel = ground DC Equipotential lines (denser -> higher field) Cond. Rubber = ground Wet-mate chamber AC rubber Copper Copper = high voltage XLPE Steel = ground Epoxy DC axis Oil axis Copper = high voltage Challenge with field control in wet-mate chamber Beyond field control -- challenges of contamination, surface discharge, axis 12

Wet-mate chamber configurations Power conducto r Oil Clean

cleaner is better Zig-zag path helps prevent DC surface breakdown

voltage Power conducto r Easier DC breakdown along straight

13 Wet-mate chamber configurations Power conducto r Oil Clean environment DC conduction & breakdown are sensitive to contaminants cleaner is better Zig-zag path helps prevent DC surface breakdown Ground Solid insulation Water=Ground Oil Unmated Stab type Mated High voltage Power conducto r Easier DC breakdown along straight interfaces Rubber bellow Oil Solid insulation Unmated Water=Ground Mated Ground High voltage 13

14 RPSEA Project Subsea High Voltage Direct Current Connectors Project overview: Objective: develop electrical prototype mock-up, retire DC + subsea technical risks Funding: $2.9 MM (with 20% GE costshare) Duration: 06/20/14 to 09/30/16 Phase 1: 06/14 to 02/15, $800K Major deliverables: Phase 1: Technical requirements Technical gap analysis Phase 2: Dry-mate (DM) & Wet-mate (WM) connector electrical design (tentative 50kV DC) WM electrical prototype mock-up Phase 2: 03/15 to 09/16, $2100K Ambient condition test results Simulated subsea condition test results 14

RPSEA Project 12121-6302-01 Subsea High Voltage Direct Current Connectors Scope highlight: Electrical focus: (new) DC electrical + (existing) AC mechanical Wet-mate focus: DC cable termination

15 RPSEA Project Subsea High Voltage Direct Current Connectors Scope highlight: Electrical focus: (new) DC electrical + (existing) AC mechanical Wet-mate focus: DC cable termination Wet-mate chamber Past work: RPSEA MSDC project ( ), DC connector task 50kVDC WM conceptual design, basic materials tests Termination L ~ 2 m D ~ 0.25 m Rating: 50kV/500A DC Wet-mate chamber 50kV/500A DC WM electrical conceptual design: compatible with geometry & tooling for MECON 36kV/500A 3-phase AC 15

16 Team Introduction GE Global Research NAME Role Chris Calebrese Materials Scientist Di Zhang Power Electronics Engineer Dong Dong Power Electronics Engineer Gary Yeager Chemist Ibrahima Ndiaye HV Engineer Jeff Sullivan Manager - Dielectrics Lab Konrad Weeber Chief Engineer Liwei Hao HV Engineer Michael VanderWerken Business Development Manager Pat Irwin HV & VPI Systems Initiatives Leader Phil Cioffi Power Electronics Engineer (Mechanical) Qin Chen Electrical Engineer, PI Rob Sellick Manager - HV lab Rui Zhou Manager - High power conversion systems lab Weijun Yin Principle Engineer Xu She Power Electronics Engineer GE Subsea Systems (in GE Oil and Gas) NAME Role Aslaug Melbo Engineering Manager Gorm Sande Principle Engineer Jan Erik Elnan Knutsen Engineering Manager Kristin Elgsaas Senior Product Manager Svend Rocke Chief Consulting Engineer Working Project Group NAME Xiaolei Yin (Champion) David Liney Edouard Thibaut Herve DE NAUROIS Khalid MATEEN Kevin Corbett Gorm Sande Svend Rocke James Pappas Technical Coordinator Roy Long Bill Fincham Program Manager Qin Chen PI COMPANY Exxon Mobil Shell TOTAL TOTAL TOTAL Exxon Mobil GE Subsea Systems GE Subsea Systems RPSEA DOE NETL DOE NETL GE Global Research University of Connecticut (subcontractor; team leader: Prof. Yang Cao) Dr. Steven Boggs (technical consultant) 16

regulations Power system design options (electrical

requirements Industrial workshop No. 1 2.

need Preliminary technical evaluation Industrial workshop No.

17 Phase I approach 1. Technical requirement Oil & Gas industry application needs & regulations Power system design options (electrical performance, fault protection, packaging) Derive connector requirements Industrial workshop No Technical gap Assess state of the art Estimate development need Preliminary technical evaluation Industrial workshop No. 2 Example of subsea DC electric power system Example of subsea AC connectors (GE MECON) WM 36kV/500A, 3-phase DM 36kV/700A DM 145kV/700A 17

method Design test on small coupons and down-scaled geometries 2.

18 Phase II, stage gate 2-1: design & construction 1. Design Electrical design analysis (WM & DM connectors) Assessment of compatibility with subsea mechanical design Qualification test method Design test on small coupons and down-scaled geometries 2. Construction To be coordinated by GE Subsea Systems (AC connector experiences; established fabrication methodology; quality assurance) Preliminary 50kV/500A DC WM connector design Structure of WM connector Voltage distribution 36kV/500A MECON WM (AC) prototype under assembly 18

acceleration Rated load current & load cycles Transient DC waveforms (e.g.

19 Phase II, stage gate 2-2: ambient condition test As-fabricated prototypes Test system to be assembled Short term electrical tests (e.g. capacitance & loss, resistance, hi-pot, partial discharge) Long term DC electrical test Cable loop Excessive DC voltage for acceleration Rated load current & load cycles Transient DC waveforms (e.g. polarity reversal) Superimposed impulses Detailed test conditions to be designed & reviewed Sub-component tests Outline of long term DC test system Example of subcomponent electric measurement 19

with termination chambers In-situ measurement of electrical parameters Conditioning process design supported by

20 Phase II, stage gate 2-3: simulated deep sea condition test Simulated subsea conditioning WM chamber exposed to high pressure sea water Flushing by processing liquids Expose to processing liquids at high pressure Assemble with termination chambers In-situ measurement of electrical parameters Conditioning process design supported by materials tests (e.g. diffusion, surface absorption) Short term & long term DC electrical test Sub-component tests 20

21 Project schedule Tasks Collect VOC Tech. requirement Gap analysis Design analysis 1 st design Modeling study Revised design Construction 1 st prototype 2 nd prototype Materials and simple geometry tests Experiment Dry Test 1 st prototype Dry Test 2 nd prototype Simulated deep sea test Project start 1 st open worksho p 2 nd open workshop GO/NO-GO Prototyping & drytest report out GO/NO-GO Project end Note: parallel tasks arranged due to shortening of performance period 21

22 Technical Requirement Preliminary Studies

23 Contents Definition of technical requirements Subsea processing needs from the industry Subsea DC electrical systems Challenges and requirements for DC connectors 23

24 Technical requirements for subsea DC connector Operational conditions (depth, temperature, etc) Electrical ratings (focus on DC) Mechanical ratings General requirements (life, maintenance-free, etc) Specific requirements for wet/dry mate connectors and penetrators Test requirements (to be finalized in Phase II) Focus on defining requirements related to DC electrical operation 24

25 Summary key connector electrical ratings Parameter RPSEA Governing factor prototype Rated voltage ± 50 kv System power, distance Rated current 500 A System power, distance Overvoltage 2.5 U 0 Cable ground fault, with high impedance grounding Short circuit current Polarity reversal 15 I 0 (0.5 sec) Cable ground fault DC system short circuit Protection mechanism Full reversal in 1 msec System ground fault 25

26 Technical requirements - Approach General requirements Distance Power Depth, etc. Connectors will also set requirements for system specs Electrical system System topology Fault analysis Connector requirements Electrical requirements Non-electrical requirements 26

Typical subsea processing systems Boosting Increase

subsea wells Separation Remove water from oil

reservoir Compression Drive gas from matured subsea

27 Typical subsea processing systems Boosting Increase oil recovery and production rate from maturing subsea wells Separation Remove water from oil stream at the seabed and re-inject back into reservoir Compression Drive gas from matured subsea wells to host Pump Pump + Separator Pump + Separator + Compressor 27

28 Power ratings for subsea power systems System Max. Power (kw) Voltage (kv) Current (A) Frequency (Hz) Control systems (incl. all electric) /3-60 Small pump 1, Large pump 5, Compressor 15, Transmission & Distribution 2,500 70, , 16 2/3 /50/60 Data based on existing systems Future perspectives? 28

29 Overview of subsea power system Higher Power rating Deployed Pilot-tested, not deployed New system, similar concept Depth: up to several kms M M M M M Top side Subsea New concept Top side AC Subsea AC 50/60Hz Subsea AC Low frequency Subsea DC Longer step out * Data from 2014 subsea electrification survey 29

30 Example of subsea AC system 30

31 Example of subsea DC system 31

32 Subsea electrical network components Cable AC transformer (pressure compensated) Source: wikipedia ( e_island_wind_project_submarine_power_cable.jpg) Cable connectors 145kV AC, single-conductor DM connector DC converter (1 atmosphere) Other components: motors, switches, 32

33 Electrical system analysis for DC connector requirements Focus on generic system, instead of a specific system with detailed design Focus on transmission side more challenging for connectors than distribution side (distribution voltage is lower, and system protection will be coordinated to meet current ratings for connectors) 33

34 Generic models - voltage source system Centralized source and load Stacked source and centralized load Centralized source and stacked load Stacked source and load Source controls voltage, load determines current 34

35 Generic models - current source system Centralized source and load Stacked source and centralized load Centralized source and stacked load Stacked source and load Source controls current, load determines voltage 35

36 DC transmission options for subsea On shore Sending end - centralized or stacked structure Off shore Receiving end - stacked structure preferred Stacked subsea receiving end Rationale: 1. Redundancy leads to higher reliability 2. Smaller packaging size 3. Easier installation and individual module retrieval High voltage wet mate DC connector needed Source Load 36

37 Fault scenarios under investigation Voltage source system Current source system Transmission side fault scenarios: 1. Cable ground fault 2. DC voltage short circuit fault 3. Ground fault between the stacked modules 4. Fault within the individual modules 37

38 Studied voltage source DC system Load Source Dry mate connector Wet mate connector System parameters: Parameters Value DC voltage 150kV (+/-75kV) Load power rating 60MW Step out distance 180km Generic system architecture under study Connector locations for illustration only; actual locations depends on system architecture and mechanical packaging. Grounding schemes affect fault behavior, only selected cases presented. No protection is considered in generic system architecture. 38

39 Mechanism of over-voltage Model under study Overvoltage at ground fault Vao=2Vdc Vbo=0 Voltage doubling under worst case system design 39

4X) V C1 Voltage: kv Overvoltage due to ground fault Current path under fault

40 Ground fault of the cable I RE Current: ka Generic model Time: sec Wet mate DC connector current (1.4X) V C1 Voltage: kv Overvoltage due to ground fault Current path under fault Time: sec Wet mate DC connector voltage (~2.1X) (common mode voltage may see polarity reversal) *Note: fault response depends on cable impedance 40

41 Mechanism of over-current I fault L r V dc Short the capacitance, e.g. cable capacitance Dynamic response determined by: 0 Loop inductance value will affect the transient current 41

Ground fault next to DC connector Overcurrent due to ground fault Current: ka I RE25 I RE1 Generic model Time (sec) Wet mate DC connector current (5X) V in1 Voltage (kv) V

42 Ground fault next to DC connector Overcurrent due to ground fault Current: ka I RE25 I RE1 Generic model Time (sec) Wet mate DC connector current (5X) V in1 Voltage (kv) V in2 to V in5 Current path under fault *Note: Fault response dependent on cable impedance and receiving module inductance Time (sec) Differential voltage of connector (1.25X) 42

43 Ground fault within the module Current: ka I RE1 Time: sec Generic model Wet mate DC connector current (3X) V in1 Voltage: kv V in2 to V in5 Time: sec Differential voltage of connector (1.4X) Current path under fault * Note: Fault response dependent on cable impedance and receiving module 43 inductance

44 Transmission DC short circuit fault DM connector overcurrent due to short circuit Current: ka I SE 0.16pu inductance in the source Time: sec Generic model Dry mate DC connector current (9X): Break in 5ms: >4x, Break in 50ms: >7x Current: ka I RE Time: sec Current path under fault Wet mate DC connector current Short circuit current depends on total inductance in the loop and available breaker technology. Wet mate connector is very unlikely to experience this current 44

45 Studied current source DC system Dry mate connector Wet mate connector System parameters: Parameters Value DC voltage 150kV (+/-75kV) Load power rating 60MW Step out distance 180km Generic model (MSDC system) Connector locations are for illustration only; actual locations depend on system architecture and mechanical packaging. Grounding schemes will affect the fault behavior, only selected cases are presented. 45

Ground fault of transmission cable Source Load V PCM RE1 SE1 V NCM SE2 RE2 Polarity reversal due to ground fault SE6 RE8 Generic model Common mode voltage of connector Differential voltage surge

46 Ground fault of transmission cable Source Load V PCM RE1 SE1 V NCM SE2 RE2 Polarity reversal due to ground fault SE6 RE8 Generic model Common mode voltage of connector Differential voltage surge (not concern for singleconductor connectors) Current path under fault Differential mode voltage of connector (3.5X, voltage reverse) *Note: Overvoltage highly dependent on receiving module inductance 46

47 Bypass event of one module Icon1-Icon4 ICON (ka) Generic model Time (sec) Wet mate DC connector current (1.7X) Vcon2-Vcon3 VCON (kv) Time (sec) Differential voltage of DC connector (1.4X) Current path under fault *Note: Overcurrent dependent on the distribution cable and other impedance. 47

48 Ground fault within the module SE1 I RE I 1 RE1 SE2 Source RE2 Load I 2 I 3 SE6 RE8 Generic model Wet mate DC connector current (3X) Current path under fault Fault current is highly dependent on the transmission cable 48

49 Summary subsea electrification general needs Total system power: MW (>100 MW future) Loads pumping, boosting, water injection, compression Unit load power : up to 5 MW for pumps; up to 15 MW for compressors Distance: up to 400 km (>600 km future) Depth: up to 3000 m 49

50 Summary need for connectors Receiving end module (from top side) Power 4 5 electronics Transmission cable Distribution cable (to loads) Transmission network Distribution network Location Type AC or DC? Voltage Current 1 Dry-mate DC High Medium 2 Wet-mate DC High Medium 3 Penetrator DC High Medium 4, 5, (distribution side) Dry-mate, wetmate, penetrators DC and AC Low to Medium High (but not exceeding AC connectors) 50

51 Summary electrical system Transmission system rating Voltage & current depend on power & distance, cost vs. technical challenge tradeoff Example: 60MW, 180 km ±75 kv, 400 A (or ± 50kV, 600 A) Modularized subsea DC power conversion Redundancy -> high reliability Smaller packaging (easier cooling, easier deployment, cost) Individual retrieval Greatest electrical challenge: wet-mate connector at transmission voltage level 51

52 Summary electrical system fault analysis Generic voltage-sourced and current-sourced system models analyzed Focus on transmission-side risks, due to high voltages & stored energy Fault response dependent on system design, protection schemes, & system fault tolerance Major impact on connectors: Overvoltage Short circuit current Polarity reversal 52

53 Summary key connector electrical ratings Parameter RPSEA Future need Governing factors prototype Rated ± 50 kv ± 150 kv System power, distance voltage Rated 500 A A System power, distance current Overvoltage 2.5 U U 0 Cable ground fault, with high impedance grounding Short circuit current Polarity reversal 15 I 0 (0.5 sec) Full reversal in 1 msec 15 I 0 (0.5 sec) Cable ground fault DC system short circuit Protection mechanism Full reversal in 1 msec System ground fault 53

54 DC connector technical requirement Operational requirements (for WM/DM/Penetrator) Value Unit No. of connection 10 times Maximum water depth 3000 m External temperature range -5 to 20 deg C Internal temperature range -5 to 60 deg C Storage temperature -25 to 60 deg C Service life 25 years Maintenance need Maintenance free Min. onshore storage time 1 year Min. subsea storage time 1 year No. of water sealing barriers between seawater and live parts 2 Electrical Rating (for WM/DM/Penetrator) Voltage rating (U0) ± kv kv Current rating (I0) A Maximum transient current 2.5*I0 (to be updated) A Duration of transient current (to be updated) sec Short circuit current 15*I0 A Duration of short circuit current 0.5 sec Overvoltage 2.5x U0 kv Polarity reversal time 1 msec Requirements for WM Connectors No. of matings 50 times Orientation during operation horizontal, vertical, tilted Tolerence against deposits calcium deposit, marine growth, debris Tolerence against contaminations sand, silt Tolerence against cleaning acidic cleaning (e.g. citric acid), mechanical brushing Requirements for DM Connectors Tolerence against harsh offshore environment (e.g. humidity, Mating environment salt) Requirements for Penetrators +/- 10 (with pressure compensation) Up to 300 (no pressure compensation, depending on water Differential pressure rating (ISO standard) depth) bar 54

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