Deliverable D6.3.5,
2nd Proof of Concept Demonstrator,
Line fault detector field test at Masala,
with ABB and Fortum
16-19.4.2012
Henry Rimminen, Anu Kärkkäinen
VTT Technical Research Centre of Finland
27/06/2012
Deliverable D6.3.5
The field test results from Masala is analyzed in the following
This document is the deliverable D6.3.5 (2nd Proof of Concept
Demonstrator of the VTT line fault detector)
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3
Background
Fault detectors were designed to measure magnitude of current and
phase of voltage
Combination of these reveal phase change caused by faults
Both measurements are non-contact
Time synchronization enables sum current calculation of three phases with
three detectors
Bluetooth is used for synchronization and data transmission
They harvest operating power from the line current
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Operation
1.
2.
Clocks are synchronized with Bluetooth
Currently all data is transmitted for analysis. Later only alarms are
enough. Sample rate is 1200 Hz (= 24 samples per 50-Hz cycle).
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Photos
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Normal state
In normal state (Wed. morning 9:05), the phase current was measured to be 34 A (all currents are
RMS). At the power station ABB measured ≈ 33 A. The sum current was measured to be 1.1 A. The
three-ball-synchronization worked as planned and required no post synchronization.
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Interpretation of fault recordings
This helps to interpret the following fault recording figures
Topmost figure shows all three line currents (L1, L2, L3) starting
150 ms before the fault.
Middle figure shows sum current (L1 + L2 + L3)
Bottom figure shows synchronization flags for three fault detectors.
After Bluetooth synchronization, the fault detectors maintain their
relative synchronization using the line current waveform. They
slowly adjust their internal clock so that every 24th sample matches
the zero-crossing of the current waveform. Synchronization flag is
up when the internal clock and current match. When mismatch
occurs, flag goes down. This happens always during faults, so the
synchronization flags were used to trigger the recordings. Sum
current is at its minimum when all three flags are up.
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L3, short to ground
L3 shows a current of 38 A before the fault. During the fault it shows 117 A for ~20 cycles and then
returns to 38 A. Sum current is below 2 A before and after the fault and 86 A during the fault.
Phase curents, recording no. 615, time ke10.03
200
L1
L2
L3
Current (A)
100
0
-100
-200
3512.5
3513
3513.5
3514
3514.5
3515
3514
3514.5
3515
Time (s)
Sum current
150
Current (A)
100
50
0
-50
-100
-150
3512.5
3513
3513.5
Time (s)
Ball sync flags (used as recording trigger)
Clock syncd to waveform (1/0)
1.5
L1
L2
L3
1
0.5
0
-0.5
3512.5
3513
3513.5
3514
Time (s)
3514.5
3515
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L2, short to ground
L2 shows a current of 36 A before the fault. During the fault it shows 120 A for ~20 cycles and then
returns to 36 A. Sum current is below 1 A before and after the fault and 89 A during the fault.
Phase curents, recording no. 672, time ke10.10
200
L1
L2
L3
Current (A)
100
0
-100
-200
3950
3950.5
3951
3951.5
3952
3952.5
3951.5
3952
3952.5
Time (s)
Sum current
200
Current (A)
100
0
-100
-200
3950
3950.5
3951
Time (s)
Ball sync flags (used as recording trigger)
Clock syncd to waveform (1/0)
1.5
L1
L2
L3
1
0.5
0
-0.5
3950
3950.5
3951
3951.5
Time (s)
3952
3952.5
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L1, 330 Ω to ground
L1 shows a current of 35 A before the fault. During the fault it shows 62 A for ~20 cycles and then
returns to 35 A. Sum current is below 1.5 A before and after the fault and 26 A during the fault. With
330 Ω resistor, the sum current is more than three times lower than with a 0-Ω fault (26 A v.s. 86-89 A)
Phase curents, recording no. 1128, time ke11.42
A).
100
L1
L2
L3
Current (A)
50
0
-50
-100
9472
9472.5
9473
9473.5
9474
9474.5
9473.5
9474
9474.5
Time (s)
Sum current
40
Current (A)
20
0
-20
-40
9472
9472.5
9473
Time (s)
Ball sync flags (used as recording trigger)
Clock syncd to waveform (1/0)
1.5
L1
L2
L3
1
0.5
0
-0.5
9472
9472.5
9473
9473.5
Time (s)
9474
9474.5
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L1, bare wire on terrain 1
L1 shows a current of 34 A before the fault. During the fault it shows 128 A for ~20 cycles and then
returns to 34 A. Sum current is below 1 A before and after the fault and 94 A during the fault. With
bare wire to terrain, the sum current is similar than with the shorts to ground (94 A v.s. 86-89 A).
Phase curents, recording no. 1, time ke13.47
200
L1
L2
L3
Current (A)
100
0
-100
-200
72
72.5
73
73.5
74
74.5
73.5
74
74.5
Time (s)
Sum current
150
100
Current (A)
50
0
-50
-100
-150
-200
72
72.5
73
Time (s)
Ball sync flags (used as recording trigger)
Clock syncd to waveform (1/0)
1.5
L1
L2
L3
1
0.5
0
-0.5
72
72.5
73
73.5
Time (s)
74
74.5
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L1, bare wire on terrain 2
L1 shows a current of 34 A before the fault. During the fault it shows 129 A for ~20 cycles and then
returns to 34 A. Sum current is below 1 A before the fault, but L3 fails to resync afterwards leaving a
sum current of 9 A. Sum is 90 A during the fault. This is Identical with the first bare wire on terrain test.
Phase curents, recording no. 2, time ke13.54
200
L1
L2
L3
Current (A)
100
0
-100
-200
486.5
487
487.5
488
488.5
489
488
488.5
489
Time (s)
Sum current
150
Current (A)
100
50
0
-50
-100
-150
486.5
487
487.5
Time (s)
Ball sync flags (used as recording trigger)
Clock syncd to waveform (1/0)
1.5
L1
L2
L3
1
0.5
0
-0.5
486.5
487
487.5
488
Time (s)
488.5
489
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L3, bare wire on a small tree 1
L3 shows a current of 33 A before the fault. During the fault it shows 65 A for ~20 cycles and then
returns to 33 A. Sum current is below 1 A before and after the fault. Sum is 30 A during the fault. This
is almost identical to the 330-Ω to ground test (sum is 30 A v.s. 26 A).
Phase curents, recording no. 22, time ke14.27
100
L1
L2
L3
Current (A)
50
0
-50
-100
2470.5
2471
2471.5
2472
2472.5
2473
2472
2472.5
2473
Time (s)
Sum current
Current (A)
50
0
-50
2470.5
2471
2471.5
Time (s)
Ball sync flags (used as recording trigger)
Clock syncd to waveform (1/0)
1.5
L1
L2
L3
1
0.5
0
-0.5
2470.5
2471
2471.5
2472
Time (s)
2472.5
2473
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L3, bare wire on a small tree 2
L3 shows a current of 32 A before the fault. During the fault it shows 64 A for ~20 cycles and then
returns to 32 A. Sum current is below 1 A before and after the fault. Sum is 32 A during the fault. This
is identical with the first small tree test.
Phase curents, recording no. 23, time ke14.32
100
L1
L2
L3
Current (A)
50
0
-50
-100
2808
2808.5
2809
2809.5
2810
2810.5
2809.5
2810
2810.5
Time (s)
Sum current
Current (A)
50
0
-50
2808
2808.5
2809
Time (s)
Ball sync flags (used as recording trigger)
Clock syncd to waveform (1/0)
1.5
L1
L2
L3
1
0.5
0
-0.5
2808
2808.5
2809
2809.5
Time (s)
2810
2810.5
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L1, L2, L3 shorted together
L1, L2, L3 show 34 A before the fault. During the fault they clip at 200 A (peak not rms) for ~10 cycles
and then return to 34 A. The recovery to normal current seems to take 100 ms. Sum current is below 2
A before the fault and remains at 4 A for 500 ms after the fault. Then it goes below 1 A. Sum is 80 A
during the fault but it is not reliable due to clipping.
Phase curents, recording no. 81, time ke15.12
200
L1
L2
L3
150
100
Current (A )
50
0
-50
-100
-150
-200
5190.5
5191
5191.5
5192
5192.5
5193
5192.5
5193
Time (s)
Sum current
150
Current (A)
100
50
0
X: 5192
Y: 0.327
-50
-100
-150
5190.5
5191
5191.5
5192
Time (s)
Ball sync flags (used as recording trigger)
Cloc k s y nc d to wav eform (1/0)
1.5
1
0.5
0
-0.5
L1
L2
L3
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Results
Fault phase Fault resistance
Fault type
(Ω)
L3
0
Ground
L2
0
Ground
L1
330
Ground
L1
0
Terrain
L1
0
Terrain
L3
0
Tree
L3
0
Tree
L1,L2,L3
0
Short together
Phase current (Arms)
Fault
Normal
117
38
120
36
62
35
128
34
129
34
65
33
64
32
200
34
Fault - Normal
79
84
27
94
95
32
32
166
Sum current (Arms)
Fault
Normal
86
2
89
1
26
1.5
94
1
90
1
30
1
32
1
80
2
Clipping?
no
no
no
no
no
no
no
yes
The difference of phase current at normal and at fault state (column “Fault –
Normal”) follows very closely the sum current. Differences may be caused by
magnetic leakage between detectors or the network actually can not maintain
currents of the two normal phases.
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Problems
Tuesday tests did not include one fault detector device (L2)
because it broke down due to rain. L2-device was repaired on
Wednesday morning
Voltage channels of all three detectors recorded blank data during
all tests. This was caused by a code bug. The voltage channels
were tested with 20 kV in laboratory, but the bug was made after
that.
Half of the recordings were missed due to intermittent failures of
the Bluetooth connection. Cause was most likely moist surface of
the device enclosures (the balls), which hindered the quality of the
connection. These were not plotted in the results.
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Energy harvesting
Battery Voltage
3
6
5.8
2.5
Battery voltage (V)
5.6
5.4
2
5.2
Device A
5
1.5
Device B
4.8
1
4.6
4.4
0.5
Device C
Measuring?
4.2
4
0
0
5
10
15
20
25
30
Time (h)
•
•
As seen from the figure, the energy harvesting works as planned. When
idle (Measuring? = 0) the battery voltages rise. The mean harvested
current was approximately 6 mA. The devices consume 3 mA at idle.
When measuring, the battery voltage drops, since the devices consume 25
mA. The devices managed to stay operational while measuring 8 hours
during days and charging at night.
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Discussion
As mentioned before, voltage phase was missing due to a code bug
However, there was indication that the phase of the current changed
during faults, since the detectors fell out of sync during every fault.
They have stable quartz oscillators.
The detectors indicate successful synchronization if zero crossing of
the measured current is within ± 4.4 A (± 5.2º at 34 A). If the criterion is
not fulfilled, the sample clock is incremented or decremented at
constant steps of 35 µs on 20-ms intervals.
In both of the 0-Ω ground faults and in the three-line short fault, the outof-sync flag was on during the whole 400-ms fault duration. The sample
clock can adjust itself 700 µs during that time, which equals 12.1º.
This means that the phase of the current must have changed at least
17.3º (12.1º + 5.2º) during the aforementioned faults
Direction of the phase change cannot be calculated
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Summary
Voltage phase measurement failed due to a code bug and thus the fault phase
calculations were not possible.
Problems with Bluetooth caused large amounts of corrupted data
Current measurement was successful and the measured value matched the value
at the power station. Error was ≈ 1 A, which equals ≈ 0.5% full scale accuracy.
Sum current calculation of three phases succeeded and no post synchronization
was needed
Ground fault resistance at least up to 330 Ω is detectable. Data from higher
resistance faults were corrupted.
Line-to-line faults were detectable
The two fault types can be distinguished (with three detectors)
Energy harvesting was successful
Many lessons were learned, which creates good basis for next demonstrator
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Future work
It is necessary to use flash memory in the detectors to avoid radio
problems. Final product will not need this, since all data is not
stored then.
Currently we let the voltage signal clip and measure only voltage
phase. According to feedback we should keep it sinusoidal and
measure also the voltage waveform. This would reveal amplitude
of the voltage, even tough it might be inaccurate.
Overall reliability must be improved
Possibility of using “lintupallo” as enclosure will be studied
The voltage bug was an easy fix
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VTT creates business from
technology
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