Concept Design Review (CoDR)

1. Concept Design Review (CoDR) Shore Station DC Breaker Cable model Transient Analysis Components

2. NEPTUNE

3. Shore Station

4. Configuration of Shore Station

5. SHORE STATION…Power supply Selection • Off-the-shelf Buck regulator. • General ratings: • Output Voltage = 10 kV DC • Output Range = 9 – 15 kV • Voltage tolerance within 2%. • Output Power = 200 kW • Current Limiting Capability = twice the rated current = 20 A. • Local and remote control functions • Self diagnostics capabilities

6. SHORE STATION…Power supply Selection Potential vendor for shore stations Manufacturer: Diversified Tech Model: Custom made. Specifications: • Input: 3 phase 13.8 kW service. • Output: 10kV / 200kW using the HV buck regulator technology. • Over current protection: Above 40A. Solid state system will act as current limiter. • Dimensions: 40” by 36” by 42” estimated.

7. SHORE STATION…Surge Protection • Spark gap arresters • Metal oxide varistor (MOV) • ceramic, polymer or silicon rubber insulator • Surge arresters are selected based on several ratings • Energy absorption capability (or energy withstand capability) • Maximum continuous operating voltage (MCOV) • Temperature rise.

8. SHORE STATION…Vacuum Switches (Breaker) • Types: • Air • Air-blast • Magnetic quencher • Oil • Sulfur hexafluoride gas (SF6) • Vacuum • Solid-state

9. SHORE STATION…Vacuum Switches • Vacuum breaker is used for systems under 36 kV. • Pollution-free • Fast • Reliable • Compact • Light weight • Requires small energy to operate.

10. SHORE STATION…Vacuum Switches Potential manufacturer: Kilovac or Jennings Specifications: • Contact Arrangement: Normally Open. • Rated Operating Voltage:28kV • Max. Current: 40A. • Max. Contact Resistance: 0.02 ohm. • Release time < 20 ms • mechanical lifetime > 2 million cycles.

11. DC Circuit Breaker

12. S2 S3 S4 R1 R2 S1 C DC CIRCUIT BREAKER

13. S1 S4 R1 R2 DC CIRCUIT BREAKER…Stage 1- Normal closure S2 S3 C

14. S4 R1 R2 S1 C DC CIRCUIT BREAKER…Stage 2 - Interruption S3 S2 Current is routed through C Size of C is selected to prevent restrikes

15. S2 S3 S4 R1 R2 S1 C DC CIRCUIT BREAKER…Stage 3 – Discharging of Capacitor Cap is discharged through R2 to set the circuit for next switching

16. S2 S3 S4 R1 R2 S1 C DC CIRCUIT BREAKER…Stage 4 – Soft Starting Soft starting resistance R1 reduces the inrush current during energization

17. S1 S4 R1 R2 DC CIRCUIT BREAKER…Stage 5 – Normal closure S2 S3 C

18. Components Selection Vacuum Switches • Voltage Rating • Withstanding Voltage > 25kV • Continuous Current Rating • 20A or higher • Release time • Faster release time means smaller capacitor is required. Release time < 20 ms • Lifespan, measured in cycles of operation • Millions of operations

19. Components Selection Capacitor • Voltage Rating • 15-20kV rating • Capacitance • 1-10μF, depending on node location • Size • up to 600 cubic inches • Lifespan • Measured in hours of operation

20. Components Selection Resistors • 2 Resistors: soft close and capacitor discharge • Resistance value: Both are currently specified at 1kΩ • Peak Voltage Rating: 10-20kV • Peak Energy Rating • Power dissipation more important in this application than average power, as resistors will be used for brief (less than one second) intervals

21. Components Selection Diodes

22. Components Selection Diodes • VRRM (maximum repeat reverse voltage): 20-25kV • Continuous forward current • Based on normal operation > 50 A • Maximum Transient Current > 300A • di/dt ratings > 100A/s • Reverse leakage current ~ A • Type: Stacked Hockey Puck

23. Cable Model

24. Cable Model…inductance

25. Cable Model…inductance • flux linkages theory a) the core b) the sheath. c) the insulation.

26. Cable Model…inductance • Cable Inductance Where: = Total flux associated with the cable. = Total cable current.

27. Cable Model…Resistance • The resistance per unit length of a tubular conductor is given by: The total cable resistance is thus given by:

28. Cable Model…Capacitance • The cable capacitance per unit length can be calculated by the formula: Where,  is the permittivity of the insulator. d is the outer radius of insulator c is the inner radius of insulator.

29. Cable Model…Seawater • The current return is through the seawater. • In near DC conditions the sea-water resistance and inductance are calculated as: R = 0.098 m/km. L = 2.221 mH/km. • These values are frequency dependent.

30. Cable Model…Composite model • For transient simulation, the steel core and copper sheath can be modeled as a composite conductor comp = 5.1753*10-8 m. comp = 9.0788

31. Results …

32. Transient Simulation Normal Switching Fault

33. TRANSIENT ANALYSIS…ATP

34. TRANSIENT ANALYSIS…What isATP? • ATP is a universal program system for digital simulation of transient analysis of transmission systems. • ATP has extensive modeling capabilities including power electronics, control, protection, etc.

35. Simulation Circuit… Normal Switching

36. N1 N2 N3 N4 Simulation Circuit… Switching Timing 0.1 0.4 0.7 1.0 1.2 1.5 1.8 2.1

37. Current at the input of Node 3

38. Voltage at the input of Node 3

39. Voltage across the left diode in Node 3

40. Simulation Circuit… Fault Condition

41. Voltage across load in Node 2

42. Current entering Node 2

43. Simulation Circuit… Restrike

44. t = topen t = (topen-t) t =( topen +t) Switch closed Switch open: initial arcing Capacitor charging Simulation Circuit… Restrike

45. Voltage Vmax RESTRIKE topen Time Initial Arcing Simulation of Restrikes

46. Simulation Results

47. Fault Simulation with restrike

48. Fault Simulation without restrike

49. Fault Simulation without restrike