New proposed BU circuit and control logic design University of Washington.

New proposed BU circuit and control logic design

University of Washington

Outline

• Current BU circuit design • Proposed BU circuit design• Current sequence of operation • Proposed sequence of operation • Implementation issues• BU controller design• Lab test• High voltage circuits (component requirements

and availability)• Transient process simulation in network scenario

Current BU circuit design

ControlControl

To Science

Problems with current BU circuit• Shunt branch current:

– The current in shunt branch must be high enough to drive one controller and two solenoids.

• When the system is energized with fault, the low voltage in the system may not close the switches.

• In some simulation cases, even without fault, if the solenoid current is 100mA, the backbone current could exceed 10 A.

• Shunt resistance:– It is always connected to the system, a constant source of

unwanted heat dissipation. – It is hard to compute the fault location with the resistances in the

circuit

Problems with current BU circuit• Memory

– The sequence of operation needs to be stored in the controller.

• Controller command is needed to close the switches.– Controllers must be powered before taking any switching actions.

New proposed BU circuit design

Controller

Controller

Science Node

Advantages of proposed circuit

• No storage of – switch status– Previous modes of operation.

• Less zeners are used. • Controller intervention is not needed to close the switches.

It is only used to isolate a fault. • Diode in shunt branch blocks the current when shore

station voltage is negative.– Power consumption in the shunt resistance is only temporary

during the closing process.– Fault is easier to be located without shunt resistances in the

network.

Proposed Sequence of Operation

Startup mode

Assume a fault exists

Fault identification

Delay T1

Normal mode

Normal mode with some switches open

Fault isolation

Delay T2

-5kV

+5kV

-10kV-5kV

-10kV

No fault Fault exists

Sequence of Operation

Startup without fault

StartupFault

IdentificationDelay T1 Normal

+5 kV -5kV -10kV

Startup with fault

StartupFault

IdentificationDelay T1

Fault Isolation

Delay T2Normal with

open switches

+5KV -5kV -10kV

Actions of

PMACS

Fault location measurements

Measurement to identify

faulty cables

Description of operations

• Startup: Energize the network at a positive voltage to close all switches without controller intervention (a lower voltage might be needed to limit the backbone current to 10A if there is a fault in the network).

• Fault identification: – System is energized at low negative voltage– If |V| >1kV inhibit any switching action (opening) because fault is

not within one cable section.– If |V| <1kV, BU computes V/I in all directions and compare with

thresholds. The threshold is related to the cable length.• Fault isolation:

– System is energized at low negative voltage– Open switches after a delay based on the V/I ratio

• Normal: Energize the system at –10kV.

Proposed BU Control Actions

• The closing of the science load and backbone switches is done simultaneously without controller intervention.

• Controller is only active during fault identification and isolation modes.

• Controller can differentiate between faults in spur cable and in the backbone

BU controller

• Main function: – Opening switches in the fault isolation mode

when low voltage (under 1kV) is detected

• Task modules:– System mode detection– Fault identification– Fault isolation

BU controller

• Microprocessor + peripherals

• logic circuit + relays

BU controller function and design

• The controller can be implemented using microprocessor or logic circuit and relays.

• Advantage of using microprocessor:– Only software programming is needed.– Qualified microprocessor maybe available.

• Advantage of using logic circuit and relay:– Simpler– Cheaper

Laboratory Test(Ann Tran)

Voltage and current sensing

Controller

Controller

Science Node

Measurement requirements

• Voltage measurement:– Ranges from –10kV to +10kV. Accuracy is not a big

concern.– Input/output isolation is required. Isolation level >

10kV.

• Current measurement:– Ranges from –10A to +10A. Accuracy is not a big

concern.– Input/output isolation is required (considering the

current measurement from the other end of the switch to the controller). Isolation level > 10kV.

Measurement availability

• Hall effect voltage transducer with voltage divider– LEM LV 100-4000:

• Measuring range: -6000V ~ +6000V

• Isolation: RMS voltage for AC, 50Hz 12kV

• Without voltage divider: ?• Current Transducer LEM APR50B10:

– Measuring range: 10,25,50A

– Isolation: RMS voltage for AC, 50Hz 5kV

Transient simulation

Simulation network

1 2 3

4

5

Transient simulation

BU simulation circuit

Transient process simulation in network scenario

1

2

3

Capacitor voltage

Solenoid current

Transient process simulation in network scenario

1

4

5

Capacitor voltage

Solenoid current

Current control logic design

• Concept of operations in Boston report:

Voltage Mode m(Meaning)

Operation to be performed

+500* Fault location Close all BB breakers. Disconnect all science nodes

- 500* Fault clearing Open breaker closest to fault

-1000 Connect Science Node

Measure resistance of spur cable to science node: close switch if good

-5000 (or more)

Normal Internal monitoring only: No switch operations at full voltage

* These mean current-limit operation at the shore station

Appropriate sequencing gives unambiguous operation

Concept of operations

Un-powered +500V

Fault Locating Mode, + 500 V

• Initial switch state is unknown

• Shore station is in current limit operation

• Regardless of whether a fault is present– Positive voltage is sensed

– Backbone breaker is closed

– Science node connection is opened

• If there is a fault, its location is measured from shore

• Return to unpowered state after fault location determined


Un-powered

-500V

Fault Clearing Mode, -500V

• Initial BB switch state is closed

• Shore station is in current-limit operation

• If a fault is present– Time-coordinated protection

begins when current becomes non-zero

– Unit closest to fault trips first

• If no fault is present– Backbone breakers remain

closed

• In either case, status is stored


- 500V -1000V

Science Connecting Mode, -1000 V

• Initial science node switch state is open

• Shore station is constant voltage operation

• Spur cable resistance is measured at low current– If no fault detected, spur

switch closes

– If fault detected, spur switch stays open



-1000V -10kV

Normal Mode, -6000 V to – 10,000 V

• The control knows what the switch status is

• The control knows that is is in the Normal Mode

• If a fault occurs during Normal Mode operation– No switch action results

– Shore station enters current limit mode


Un-powered

-10kV

Controlled shutdown from normal mode

• Shore station shuts the system down

• There is no change in the state of any switch

• The location of faults, if any, is not known to the shore station

• If the shutdown is not because of a fault, the fault location step can be omitted

Proposed control logic design

• Concept of operations:

Voltage Mode m(Meaning)

Operation to be performed

+5000* Reset process Close all BB breakers. Disconnect all science nodes

- 5000* Fault clearing Open breaker closest to fault

-6000 (or more)

Normal Internal monitoring only: No switch operations at full voltage

* These mean current-limit operation at the shore station

No sequencing info is stored in the controllers


Un-powered +5000V

Startup (Fault Locating Mode), + 5000 V

• Initial switch state is unknown

• Shore station is in current limit operation

• Regardless of whether a fault is present– Positive voltage is sensed

– Backbone breaker is closed

– Science node connection is closed (opened)

• (If there is a fault, its location is measured from shore)

• Return to unpowered state (after fault location determined)


Un-powered

-5000V

Fault identification and isolation (Clearing) Mode, -5000V

• Initial BB switch state is closed

• Shore station is in current-limit operation

• If a fault is present– Time-coordinated protection

begins when current becomes non-zero and voltage lower than 1kV.

– Unit closest to fault trips first

• If no fault is present– All (Backbone) breakers

remain closed

• (In either case, status is stored)


- 500V -1000V

(Science Connecting Mode, -1000 V)

• Initial science node switch state is open

• Shore station is constant voltage operation

• Spur cable resistance is measured at low current– If no fault detected, spur

switch closes

– If fault detected, spur switch stays open



-1000V -10kV

Normal Mode, -6000 V to – 10,000 V

• The control knows what the switch status is

• The control knows that it is in the Normal Mode

• If a fault occurs during Normal Mode operation– No switch action results

– Shore station enters current limit mode


Un-powered

-10kV

Controlled shutdown from normal mode

• Shore station shuts the system down

• There is no change in the state of any switch

• The location of faults, if any, is not known to the shore station

• If the shutdown is not because of a fault, the fault location step can be omitted

What will happen if fault exists during startup mode?

Fault in radial branch during reset process

7kV0V

38

37

3635

34

27

26

25

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20

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15

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3943 44 45

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3

2

1

30 2928

1617 18 Nedonna beach

shore station

Port AlberniShore station

100

97.8

29.5

75.3

26.6

66.4

74.3

70.4

64.5

64.9

63.7

63.5

58.2

54.8

57.2

56.2

51.2

50.8

73.929.5

73.572.449.6

79.6

91

52.8

59.4

36.1

40.5

81.7

98.962.7 62.7

76.238.4

633.29

Node 5

Fault in radial branch during reset process

1kV0V

•Rest of radial cable is isolated.•The section behind the fault has no impact on fault location algorithm.

38

37

3635

34

27

26

25

19

20

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22

23

24

5

15

33

32

31

40

3943 44 45

46

41 42

47

48

4

3

2

1

30 2928


shore station


100

97.8

29.5

75.3

26.6

66.4

74.3

70.4

64.5

64.9

63.7

63.5

58.2

54.8

57.2

56.2

51.2

50.8

73.929.5

73.572.449.6

79.6

91

52.8

59.4

36.1

40.5

81.7

98.962.7 62.7

76.238.4

633.29

Fault in the loop during reset process

8kV 7kV

38

37

3635

34

27

26

25

19

20

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22

23

24

5

15

33

32

31

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3943 44 45

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41 42

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4

3

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1

30 2928


shore station


100

97.8

29.5

75.3

26.6

66.4

74.3

70.4

64.5

64.9

63.7

63.5

58.2

54.8

57.2

56.2

51.2

50.8

73.929.5

73.572.449.6

79.6

91

52.8

59.4

36.1

40.5

81.7

98.962.7 62.7

76.238.4

633.29

38

37

3635

34

27

26

25

19

20

21

22

23

24

5

15

33

32

31

40

3943 44 45

46

41 42

47

48

4

3

2

1

30 2928


shore station


100

97.8

29.5

75.3

26.6

66.4

74.3

70.4

64.5

64.9

63.7

63.5

58.2

54.8

57.2

56.2

51.2

50.8

73.929.5

73.572.449.6

79.6

91

52.8

59.4

36.1

40.5

81.7

98.962.7 62.7

76.238.4

633.29

Fault in the loop during reset process

1kV 2kVA

Voltage at A could be low but should still be above the SIDAC break over voltage. The switch behind the fault still can be closed.

Fault between shore station and the network

10kV

38

37

3635

34

27

26

25

19

20

21

22

23

24

5

15

33

32

31

40

3943 44 45

46

41 42

47

48

4

3

2

1

30 2928


shore station


100

97.8

29.5

75.3

26.6

66.4

74.3

70.4

64.5

64.9

63.7

63.5

58.2

54.8

57.2

56.2

51.2

50.8

73.929.5

73.572.449.6

79.6

91

52.8

59.4

36.1

40.5

81.7

98.962.7 62.7

76.238.4

633.29

Fault between shore station and the network

• The network will lose one energy source. However, the switches should be able to close with the voltage from the other source.

10kV

38

37

3635

34

27

26

25

19

20

21

22

23

24

5

15

33

32

31

40

3943 44 45

46

41 42

47

48

4

3

2

1

30 2928


shore station


100

97.8

29.5

75.3

26.6

66.4

74.3

70.4

64.5

64.9

63.7

63.5

58.2

54.8

57.2

56.2

51.2

50.8

73.929.5

73.572.449.6

79.6

91

52.8

59.4

36.1

40.5

81.7

98.962.7 62.7

76.238.4

633.29

0V

Conclusion

• The network will be closed as expected in any case.

Component requirements: Capacitance

• Voltage: voltage over capacitor will not exceed SIDAC break over voltage, which should be within 100V. It is a low voltage capacitor.

• Capacitance: solenoid of latching switch needs to be energized over a certain time (5-10ms) with a current over a certain value. Capacitance needs to meet both of these requirements, typically around 1e-4 F.

Component requirements: SIDAC

• Break over voltage VBO: – This is the maximum voltage that will be added across

the two solenoids in series. It needs to meet the requirement of the solenoid to close the switch.

– The voltage is also the lowest voltage under which BU could close its switches in startup mode. It needs to be as low as possible.

– Proper value is around 40~100V.

• Current: – Maximum current is VBO/ (Rsolenoid *2). It should be

below 1A.

Component requirements: Diode

• Voltage: diode needs to withstand 10kV in the normal situation.

• Current: – There will be current in the diode only when the network is

positively energized. – The current is equal to BU voltage divided by shunt resistance. – Its value will influence the capacitance charging time, thus the

time to close the switches.– If we can bear a longer time to close all the switches in the

network, this current could be set to a very low value by using a big shunt resistance or low shore station voltage. A reasonable value is around 0.2 A.

Component requirements:Shunt resistance

• Resistance: – Value of resistance decides the charging current of capacitance

– And the voltage variation range in the network, which is shown below.

0 5 10 15 200

1

2

3

4

5

6

7

8

9

10

Equivalent shunt branch resistance (k )

Vo

lta

ge

(k

V)

Lowest backbone voltage under 10kV shore station voltage

Component requirements:Shunt resistance

• The bigger the resistance, the smaller the voltage variation in the network. But the cap charging time will be increased. Around 50,000 ohms is recommended. (Equivalent shunt branch resistance is 25,000 ohms.)

• Power: When using 50,000 ohms resistance, the biggest shunt resistance current will be 0.2 A, assuming the shore station voltage is 10kV. So the maximum power dissipated by it is 2 kW. And it will only last tens of seconds.

Component availability

• This will be presented by Ann.

New proposed BU circuit and control logic design University of Washington.

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