dc arcs

Aditya Shekhar (TU Delft) Electric Arcs in DC Systems June 25, 2015 1 / 35

Electric Arcs in DC SystemsCharacterization, Detection and Extinction

Delft University of Technology

Aditya Shekhar

June 25, 2015

Outline

1 Load-side Series Arc Detection in Low Voltage DC Microgrids

Proposed Arc Detection Algorithm

Choice of Filter Time Constants

Impact of Circuit Parameters

Experimental Validation

2 Bus Transfer Switching with HVDC GIS Disconnector

Experimental Setup and Simulation Model

Parameter Estimation

Recovery and Re-strike Voltage

Analysis of Bus Transfer Experiments

3 The Big Picture


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3 The Big Picture


Fundamental Concept

Iarc

Ldc

Vdc

Rdc Rarc

Cload

LOAD

Vload

Equivalent Circuit−1 0 1 2 3 4 5 6 7 8 9 10

50

60

70

80

90

100

110

Time (ms)

Load

Vol

tage

(V

) Initial electrode dependentvoltage drop to be detected

Measured load voltage: drop of 13.3 V.

• Detection of series arcs from load voltage drop (plug out).

• Selectivity in parallel load.



Vload

1

1

ss

If ΔV > Vdetect

–

+

ΔV

Detach load to eliminate arc

1

1

sf

Vflp

Vslp

Fast Low Pass Filter

Slow Low Pass Filter

Band Pass Filter


Selectivity for Parallel Loads

Idc Ldc

Vdc

Rdc Rcab1

Rcab2

Rarc1

Rarc2

Icab1 CL1

CL2Icab2

Constant

Power

Constant

Power

Lcab1

Lcab2 IL2

IL2

Vcom VL1

VL2


Validation - Simulation Results

−1 0 1 2 3 4 5 6 7 8 9 100

1

2

3

4

5

Time (ms)

Cur

rent

(A

)

Load Current 1Load Current 2

−1 0 1 2 3 4 5 6 7 8 9 1075

80

85

90

95

100

105

Time (ms)

Vol

tage

(V)

Load 1 VoltageLoad 2 VoltageV

slp, Load 1

Vflp

, Load 1

Load 2 keeps running

Arc extinguished

Arc detected

Vdetect

=10 V

τflp

=0.0001 s

Load 1 selectively ramped to zero on arc detection

τslp

= 0.001 s


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3 The Big Picture


Intuitive Understanding: Filter Time Constants

0 2 4 6 8 10−2

0

2

4

6

8

10

12

14

Time (ms)

Vol

tage

(V)

∆V with Fast LPF Tc=1 ms

0 2 4 6 8 10−2

0

2

4

6

8

10

12

14

Time (ms)

Vol

tage

(V)

∆V with Fast LPF Tc=0.5 ms

0 2 4 6 8 10−2

0

2

4

6

8

10

12

14

16

18

Time (ms)

Vol

tage

(V)

∆V with Fast LPF Tc=0.1 ms

Slow LPF Tc=0.01 s

Slow LPF Tc=0.02 s

Slow LPF Tc=0.03 s

Slow LPF Tc=0.05 s

Slow LPF Tc=0.07 s

Slow LPF Tc=0.1 s

Slow LPF Tc=0.4 s

Vdetect

=10V

• It would be nice to have:• High value of slow LPF time constant.• Low value of fast LPF time constant.

• 150 Hz to 1.5 kHz bandpass is chosen nally...


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3 The Big Picture


Frequency Domain Analysis

0 200 400 600 800 10000

2000

4000

6000

8000

10000

12000

14000

16000

Inductance (µH)

Nat

ural

Fre

quen

cy (

Hz)

Capacitance= 10 µFCapacitance= 22 µFCapacitance= 47 µFCapacitance= 100 µFCapacitance= 215 µFCapacitance= 464 µFCapacitance= 1000 µF

Magnitude Response

0 1 2 3 4 50

0.5

1

1.5

2

2.5

3

3.5

Normalized Frequaency (f/f0)

Mag

nitu

de R

espo

nse

(|Vc|/|

|Vi|)

Q=0.25Q=0.5Q=1Q=2Q=3


RL

C

f = 1

2π√LC Q = 1

R

√L

C

Detection Voltage at Discrete BPF Output

0.5 0.501 0.502 0.503 0.504 0.5050

5

10

15

Time (s)

Vol

tage

(V)

Grid Inductance=47 µH, Resistance=0.125 Ω

0.5 0.501 0.502 0.503 0.504 0.5050

5

10

15

Time (s)

Vol

tage

(V)


0.5 0.501 0.502 0.503 0.504 0.5050

5

10

15

Time (s)

Vol

tage

(V)


0.5 0.501 0.502 0.503 0.504 0.5050

5

10

15

Time (s)

Vol

tage

(V)

Grid Inductance=465 µH, Resistance=1 Ω

0.5 0.501 0.502 0.503 0.504 0.5050

5

10

15

Time (s)

Vol

tage

(V)

Grid Inductance=1000 µH, Resistance=2 Ω

Load Capacitance=10 µFLoad Capacitance=22 µFLoad Capacitance=47 µFLoad Capacitance=100 µFLoad Capacitance=216 µFLoad Capacitance=465 µFLoad Capacitance=1000 µF


Maximum Detection Voltage

0

5

10

0

5

100

5

10

15

Natural Frequency (kHz)Quality Factor

Max

imum

Det

ectio

n V

olta

ge (

V)

0 2 4 6 8 100

2

4

6

8

10

12

14

Natural Frequency (kHz)

Max

imum

Det

ectio

n V

olta

ge (

V)

2

4

6

8

10

12


RL

C

Voltage to Band pass

filter

Detection Boundary

0 1 2 3 4 5 6 7 8 9 100

2

4

6

8

10


Qua

lity

Fact

or

Threshold Voltage = 7 V

0 1 2 3 4 5 6 7 8 9 100

2

4

6

8

10


Qua

lity

Fact

or


0 1 2 3 4 5 6 7 8 9 100

2

4

6

8

10


Qua

lity

Fact

or


0 1 2 3 4 5 6 7 8 9 100

2

4

6

8

10


Qua

lity

Fact

or


0.2

0.4

0.6

0.8

1

DetectionTime (ms)

Black indicates no detection


RL

C

Voltage to Band pass

filter

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3 The Big Picture


Real Time Arc Detection

−4 −2 0 2 4 6 870

80

90

100

Time (ms)

Vol

tage

(V

)Threshold Voltage = 6 V

0

2

4

Vol

tage

(V

)

−4 −2 0 2 4 6 870

80

90

100

Time (ms)

Vol

tage

(V

)


0

2

4

Vol

tage

(V

)

−4 −2 0 2 4 6 870

80

90

100

Time (ms)

Vol

tage

(V

)


0

2

4V

olta

ge (

V)

Voltage Across Load CapacitorDetection Signal from C2000

−5 0 5 1070

75

80

85

90

95

100

Time (ms)

Vol

tage

(V

)


0

1

2

3

4

Vol

tage

(V

)

Tdetect

=2 ms

Tdetect

=2.5 ms Tdetect

=2.8 ms

Tdetect

=1.25 ms

6.2 ms 5.5 ms

4.2 ms 2.3 ms


Iarc

Ldc

Vdc

Rdc Rarc

Cload

LOAD

Vload

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3 The Big Picture


Bus Transfer in HVDC Substations

Feeder 1 Feeder 1 Feeder 1Feeder 2 Feeder 2 Feeder 2

DS1 DS1 DS1DS2 DS2 DS2

Before making DS2, current

(green) flows from feeder 1 to

feeder 2 via busbar coupling (BC).

With both DS1 and DS2 closed,

parallel buses share current from

feeder 1 to feeder 2

After breaking DS1, current (red)

flows from feeder 1 to feeder 2 via

busbar coupling (BC).

BC BC BC

R1

R2

L1

L2

VDS

Itot

I2

I1

Vbus


Experimental Setup

Bus 1

InductanceBus 2

Inductance

GIS

Disconnector

Oscilloscope

Box

Motor

Controller

Power

Supply

Manual

Grounding

Stick

Automatic

Grounding

Stick

Control

Room


Equivalent Circuit

Lnn

CnnVC

Rm

R1

R2

L1

L2

VDS

Itot I2

I1

Vbus

Lm

Dn

Sn

n = 3 n = 3

Vout

Rnn

Ibn


Next Subsection











3 The Big Picture


Developed Graphical User Interface

1.3.

2.

4.


Equivalent Circuits for AnalysisInductances with GIS Open

Lnn

Rm

R1

L1

Itot

I1

Lm

Vout Vbus

Rnn

Currents and voltages are falling

exponentials.

Inductances with GIS Closed

L11

Rm

R1

R2L1

L2

VDS

Itot I2

I1

Vbus

Lm

Lds

Rds

R11

Currents and voltages are sum of

two exponentials.


Inductance Computation

dI1dt(1) I1(1)

dI1dt(2) I1(2)

. .

. .

dI1dt(n) I1(n)

L1R1

=

Vbus(1)

Vbus(2)

.

.

Vbus(n)


Inductance of GIS Disconnector

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

x 10−4

−1.2

−1

−0.8

−0.6

−0.4

−0.2

0

0.2

Time (s)

Vol

tage

(V

)

Lds

VdsL

dI2

dt+ RI2

LdI2

dt

RI2

• Voltage Drop across this due to current gradient must be

removed to estimate the actual arc voltage.


Corrected Arc Voltage

7.4 7.5 7.6 7.7 7.8 7.9 8 8.1 8.2 8.3 8.4

x 10−3

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Time (s)

Vo

lta

ge

(p

.u.)

Disconnector VoltageU

arc,fast

Uarc,lp

Restrike


Comparison of Measured and Simulated Results

0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 0.0450

200

400

600

800T

ota

l C

urr

en

t (A

)

Time (s)

0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 0.045−100

−50

0

50

100

150

200

Bu

s V

olta

ge

(V

)

Time (s)

0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 0.0451100

1200

1300

1400

1500

Ca

pa

cito

r V

olta

ge

(V

)

Time (s)

0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 0.0450

100

200

300

400

Vo

lta

ge

(V

)

Time (s)

Simulated CurrentMeasured Current

Simulated Bus VoltageMeasured Bus Voltage

Simulated Capacitor VoltageMeasured Capacitor Voltage

Simulated Buck Output VoltageMeasured Buck Output Voltage


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3 The Big Picture


Derived Analytical Expression

Recovery voltage is the voltage that appears across the electrodes ofthe GIS disconnector at the instant of arc extinction.

Restrike Voltage is the voltage across the disconnector just be-fore the instant of arc reignition.

Vbus =

(Itot

τm− I1

τ1

)(Lm

(1

Lin+ 1

Lm

))−(∑3

n=1Pn

Lnn

)VC − Itot

τm+∑3

n=1

(Ibn

τnn

)1

Lm− Lm

(1

Lm+ 1

L1

)(1

Lin+ 1

Lm

)


Eect of Capacitor Voltage and Source

Inductance

4 4.5 5−200

0

200

400

600

800

1000

1200

Bus

Vol

tage

(V

)

Time (ms)

(a)

4 4.5 5−200

0

200

400

600

800

1000

1200

Bus

Vol

tage

(V

)

Time (ms)

(b)

4 4.5 5−200

0

200

400

600

800

1000

1200

Bus

Vol

tage

(V

)

Time (ms)

(c)

L

nn=0.1 mH

Lnn

=0.2 mH

Lnn

=0.5 mH

Lnn

=1.5 mH

Lnn

=5.5 mH


Eect of Switching Frequency and Source

Inductance

4 4.5 5−200

−100

0

100

200

300

400

500

600

700

Bus

Vol

tage

(V

)

Time (ms)

(a)

4 4.5 5−200

−100

0

100

200

300

400

500

600

700

Bus

Vol

tage

(V

)

Bus Voltage (V)

(b)

4 4.5 5−200

−100

0

100

200

300

400

500

600

700

Bus

Vol

tage

(V

)

Time (ms)

(c)

L

nn=0.1 mH

Lnn

=0.2 mH

Lnn

=0.5 mH

Lnn

=1.5 mH

Lnn

=5.5 mH


Next Subsection











3 The Big Picture


Graphical User Interface Developed for Analysis


The Big Picture???


Thank You!


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