Concept Design Review (CoDR)

Shore StationDC Breaker Cable modelTransient AnalysisComponents

NEPTUNE

Explorer Plate

Pacific Plate

Gorda Plate

Juan de Fuca Ridge

North American Plate

Nedonna Beach

Junction Box

Cable

study area

Plate

Juan de Fuca

Shore Station

Configuration of Shore Station

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

SHORE STATION…Power supply Selection

Potential vendor for shore stations

Manufacturer: Diversified TechModel: 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.

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.

SHORE STATION…Vacuum Switches (Breaker)

Types: Air Air-blast Magnetic quencher Oil Sulfur hexafluoride gas (SF6) Vacuum Solid-state

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.

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.

DC Circuit Breaker

DC CIRCUIT BREAKER

R1 R2S1

S2 S3

S4

C

S2 S3

R1 R2

S1 S4

C

DC CIRCUIT BREAKER…Stage 1- Normal closure

S2

R1 R2S1

S4

C

S3

DC CIRCUIT BREAKER…Stage 2 - Interruption

Current is routed through C Size of C is selected to prevent restrikes

R1 R2S1

S2 S3

S4

C

DC CIRCUIT BREAKER…Stage 3 – Discharging of Capacitor

Cap is discharged through R2 to set the circuit for next switching

R1 R2S1

S2 S3

C

S4

DC CIRCUIT BREAKER…Stage 4 – Soft Starting

Soft starting resistance R1 reduces the inrush current during energization

S2 S3

R1 R2

S1 S4

C

DC CIRCUIT BREAKER…Stage 5 – Normal closure

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

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

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

Components Selection Diodes

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

Cable Model

Cable Model…inductance

SteeltubeØ: 2.3 mm

Optical

fibers

Compositeconductor

Steel wiresstrand

Thixotropic

J elly

Insulating sheath Ø 17mm

Cable Model…inductance

flux linkages theory a) the core b) the sheath. c) the insulation.

Cable Model…inductance

Cable Inductance

cable

cable

iL

Where:

cable = Total flux associated with the cable.

cablei = Total cable current.

Cable Model…Resistance

The resistance per unit length of a tubular conductor is given by:

22 abR

condcond

The total cable resistance is thus given by:

custcable RRR ||

Cable Model…Capacitance

The cable capacitance per unit length can be calculated by the formula:

mF

cd

C /ln

2

Where, is the permittivity of the insulator.d is the outer radius of insulator c is the inner radius of insulator.

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.

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

Results …

Transient Simulation

Normal SwitchingFault

TRANSIENT ANALYSIS…ATP

TRANSIENT ANALYSIS…What is ATP?

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.

Simulation Circuit… Normal Switching

100km

100km

100km

100km

100km

N2 N3 N4N1

LOAD LOAD LOAD LOAD

Node #3

R

R

C

S1

S2S3

S4

Load

VaIa

D1 D2

Simulation Circuit… Switching Timing

0.1 0.4 0.7 1.0

N1

N2

N3

N4

1.2 1.5 1.8 2.1

Current at the input of Node 3

1

2

34

5

Voltage at the input of Node 3

1

23 4

5

Voltage across the left diode in Node 3

3

4

5

Simulation Circuit… Fault Condition

Sf LOAD LOAD LOAD

100 km

100 km

50 km

N2 N3 N1 50 km

V1

Voltage across load in Node 2

1

2

3

Current entering Node 2

1

2

3

Simulation Circuit… Restrike

Simulation Circuit… Restrike

t = (topen-t)

Switch closed

t = topen

Switch open: initial arcing

t =( topen +t)

Capacitor charging

Simulation of Restrikes

topen

VmaxRESTRIKE

Initial Arcing

Time

Voltage

Simulation ResultsMaximum voltage across

switch Release Time Minimum value of

capacitor to prevent restrikes (F)

15 kV 5 ms 2

15 kV 10ms 5

15 kV 18 ms 10

25 kV 15 ms 1

25 kV 18 ms 1

25 kV 20 ms 1

Fault Simulation with restrike

1

2

3

Fault Simulation without restrike

1

2

Fault Simulation without restrike

1

2