Break Down voltage insulating oil

Test break down voltage
comparison between IEC 60156
and step voltage application method
Pierluigi De Horatiis
Laboratory Quality Manager L.M.P. srl
Statistical measurements: mean, standard deviation.....

Increase voltage: 2 kV/s ± 0,2 kV/s
oil stirring by
magnetic anchor
Waiting time
between tests: 30 s
INSTRUMENT
OPERATING CONDITIONS
Temperature Test: 20°C ± 5°C
Distance between
electrodes: 2.5 mm

OIL TYPE: MINERAL
METHOD OF INTERVENTION
Execution of 10 tests, replicated 10 times on the same sample
Calculation of the mean and standard deviation on each replica
Calculation of the mean and standard deviation on a pair of replicates (20
tests), eliminating the 4 HIGHEST and 4 lower measures of each replica
Calculation of the mean and standard deviation, the median, the mode and
the frequency of the total 100 tests
Water content: 9 mg/kg

1^ 2^ 3^ 4^ 5^ 6^ 7^ 8^ 9^ 10^
Mean 58 60 51 61 58 64 57 58 63 61
St. Dev. ± 8 ± 9 ± 9 ± 4 ± 6 ± 5 ± 6 ± 8 ± 5 ± 4
St. Dev. % 13 15 17 7 11 7 11 8 7 4
Sequences of 10 determinations each
mean St. Dev. St.Dev. %

1^+2^ 3^+4^ 5^+6^ 7^+8^ 9^+10^
mean 58 58 62 56 62
St. Dev. ± 3 ± 5 ± 9 ± 2 ± 2
St. Dev. % 5,8 8,4 2,8 3,3 3
Sequences of 20 determinations each, eliminating the 4 HIGHEST and 4 lowest measures
mean St. Dev. St.Dev. %

100 test
Average St. Dev. St. Dev.
%
Mode Median min.
value
Max
value
59,1 ± 4,3 7,3 56 59,5 39 74
classi frequenza
1 38 42 2
2 43 48 7
3 49 54 14
4 55 60 34
5 61 66 29
6 67 72 12
7 73 78 2
range
Kurtosis= - 0,158
«platicurtica»
Class Range Frequence
BDV FREQUENCE

BDV 100 TEST
Min. value MODE MEAN MEDIAN MAX value

Increase voltage: 2 kV/s ± 0,2 kV/s
Stirring: manual
1^phase: voltage application with a to 10 kV
for 10 seconds
OPERATIVE CONDITION
Temperature Test: 20°C ± 5°C
Waiting time
between tests: 30 s
2nd phase: application of the voltage with
a increase voltage of 2 kV/s ± 0,2 kV/s
until the cancellation of the applied electric
field
electrode distance: 2,5 mm

OIL TYPE: MINERAL
METHODS OF INTERVENTION
Execution of 10 tests, replicated 10 times on the same sample
Calculation of the mean each replica
Calculation of the mean on each pair of replicas (20 tests), eliminating the 4
highest and 4 lowest measures of each replica
Water content: 17 mg/kg
Calculation of the mean on each replica (10 tests), eliminating the 2 highest
and 2 lowest measurements of each replica
electrode distance: 2,5 mm

1^ 2^ 3^ 4^ 5^ 6^ 7^ 8^ 9^ 10^
MEAN 58,6 55,1 53,8 53,8 53,7 52,9 58,9 55,5 56,2 56,1
Sequences of 10 determinations each
1^
SERIES
2^
SERIES
3^
SERIES
4^
SERIES
5^
SERIES
6^
SERIES
7^
SERIES
8^
SERIES
9^
SERIES
10^
SERIES
58 56 58 55 53 51 62 59 51 60
56 52 50 54 56 55 56 57 61 51
68 56 53 47 50 50 59 62 59 60
65 59 51 49 51 55 50 60 57 55
64 58 51 54 61 50 62 50 55 57
59 55 55 56 56 54 62 55 53 52
57 50 50 62 57 55 60 54 62 50
50 61 61 59 55 52 63 51 49 54
54 47 57 50 49 52 54 49 54 62
55 57 52 52 49 55 61 58 61 60
58,6 55,1 53,8 53,8 53,7 52,9 58,9 55,5 56,2 56,1
Mode: Median:
55 55

1^ 2^ 3^ 4^ 5^ 6^ 7^ 8^ 9^ 10^
MEAN 58,2 55,7 53,2 53,5 53,7 53.2 60 55,5 56,5 56,3
Sequences of 10 determinations each eliminate the 2 lowest and 2 highest measures
Mode: Median:
55 55,5
1^
SERIES
2^
SERIES
3^
SERIES
4^
SERIES
5^
SERIES
6^
SERIES
7^
SERIES
8^
SERIES
9^
SERIES
10^
SERIES
58 56 58 55 53 51 62 59 51 60
56 52 50 54 56 55 56 57 61 51
68 56 53 47 50 50 59 62 59 60
65 59 51 49 51 55 50 60 57 55
64 58 51 54 61 50 62 50 55 57
59 55 55 56 56 54 62 55 53 52
57 50 50 62 57 55 60 54 62 50
50 61 61 59 55 52 63 51 49 54
54 47 57 50 49 52 54 49 54 62
55 57 52 52 49 55 61 58 61 60
58,2 55,7 53,2 53,5 53,7 53.2 60 55,5 56,5 56,3

1^+2^ 3^+4^ 5^+6^ 7^+8^ 9^+10^
MEAN 56,7 53,3 53,2 57,6 56,1
Sequences of 20 determinations each eliminate the 4 lowest and 4 highest measurements
Mode: Median:
55 55
1^ + 2^ SERIES 3^ + 4^ SERIES 5^+ 6^ SERIES 7^+ 8^ SERIES 9^ + 10^ SERIES
58 56 58 55 53 51 62 59 51 60
56 52 50 54 56 55 56 57 61 51
68 56 53 47 50 50 59 62 59 60
65 59 51 49 51 55 50 60 57 55
64 58 51 54 61 50 62 50 55 57
59 55 55 56 56 54 62 55 53 52
57 50 50 62 57 55 60 54 62 50
50 61 61 59 55 52 63 51 49 54
54 47 57 50 49 52 54 49 54 62
55 57 52 52 49 55 61 58 61 60

1^+2^ 3^+4^ 5^+6^ 7^+8^ 9^+10^
MEAN 56,7 53,3 53,2 57,6 56,1
St. Dev ± 1,2 ± 1,7 ± 1,2 ± 2,7 ± 1,4
St. Dev.% 2,1 2,1 2,3 4,7 2,1
Sequences of 20 determinations each, eliminating the 4 highest and 4 lowest measurements
TEST BDV FOR STEP
MEAN St. Dev. St.Dev. %

60 tests ( pairs of "truncated" replicas)
Mean Dev.St. Dev.st.
%
Mode Median min.
Value
Max
value
55,4 ± 1,6 2,7 55 55 50 62
Kurtosis= - 0,67
CLASSE RANGE FREQUENZA
1 49-51 7
2 52-54 15
3 55-57 23
4 58-60 13
5 61-63 2
BDV FREQUENCE
Class Range Frequence

Min. value MODE MEAN MEDIAN MAX
value

Mean Dev.St.
55,4 ± 1,6
Dev.st.
Mean
0,028
Dev.st.
Mean
0,072
Mean Dev.St.
59,1 ± 4,3
Graphical representation of coefficient of variation
(standard deviation/mean ratio) versus mean breakdown voltage)
ref. IEC 60156
TEST FOR STEP IEC 60156

Electrode cleaning
electrode distance control oil test cell filling
BEFORE
AFTER

THE TESTS WERE CARRIED OUT AT THE LABORATORY OF:
Team:
PIERLUIGI DE HORATIIS
FABRIZIO PANZAVOLTA
ROBERTO PETROCCHI
FLAVIO CALVANI
00012 Setteville di Guidonia (RM)
Tel. 0774376521 – 0774378693
Email: labchimico@lmpsrl.it
www.lmpsrl.it

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