POM2-3333
Merger Unit Test User
Manual
55
Appendix A Accuracy judgement and assessment
The accuracy tests are based on the standards
IEC60044-7/8 Instrument transformers
– Part 7: Electronic voltage transformer
and
Part 8: Electronic current transformers
C.1 Limits of current error and phase displacement for
measuring current transformer
For classes 0.1 – 0.2S – 0.2 – 0.5S – 0.5 and 1, the current error and phase displacement
at rated frequency shall not exceed the values given in table 1 when the secondary
burden is any value from 25 % to 100 % of the rated burden.
Table 1
Accuracy
class
± percentage current (ratio) error at
percentage of rated current shown
below
± phase displacement at percentage
of rated current shown below
1
5
20
100
120
1
5
20
100
120
0.1
—
0.4
0.2
0.1
0.1
—
15
8
5
5
0.2S
0.75
0.35
0.2
0.2
0.2
30
15
10
10
10
0.2
—
0.75
0.35
0.2
0.2
—
30
15
10
10
0.5S
1.5
0.75
0.5
0.5
0.5
90
45
30
30
30
0.5
—
1.5
0.75
0.5
0.5
—
90
45
30
30
1
—
3.0
1.5
1.0
1.0
—
180
90
60
60
For class 3 and class 5, the current error at rated frequency shall not exceed the values
given in table 13 when the secondary burden is any value from 50 % to 100 % of the rated
burden.
Table 2
Class
± percentage current (ratio error at
percentage of rated current shown below)
At the rated current (%)
Phase displacement
50
100
Not specified
3
3
3
5
5
5
C.2 Limits of error for protective current transformers
At rated frequency and with rated burden connected, the current error, phase
displacement and composite error shall not exceed the values given in table 3
The letter P stands for protection
The current, phase and composite error should not exceed the following values.
Table 3
Accuracy class
Current error (±%) at
rated primary current
Phase displacement (
±′
)
at rated primary current
Composite error (%)
At rated primary
current
Minutes
Centiradians
5P
1
60
1.8
5
10P
3
-
-
10
C.3 Limits of voltage error and phase displacement error
for electronic measuring voltage transformers
The voltage error and phase displacement at the rated frequency shall not exceed the
values
given in table 4 at any voltage between 80 % and 120 % of the rated voltage and with
