Siemens 7SJ85 - Application and Setting Notes

The angle error between voltage transformer and current transformer has a strong influence on the measuring
accuracy. With the parameter (_:2311:101) Angle correction , you can correct the angle error. The
following 2 methods are possible here:
•
Determine the angle error from the transformer test report data. Ask the transformer manufacturer for
these values when you order the transformer.
•
While the generator is connected to the power system, measure to determine the angle error (see
chapter 11.14.2 Primary Test).
The influence on the power-system voltage makes it very difficult to test high-power generators with a meas-
urement while the generator is connected to the power system. In this case, you must determine the angle
error from the transformer test report data (see chapter 6.38.3.2 Application and Setting Notes). Alternatively,
you can use instrument transformers with small angle errors. This is ensured with class 0.2 instrument trans-
formers (voltage and current). The following equation describes the influence of the angle error:
P = 3V
1
I
1
cos(φ
V
+ φ
V,F
- (φ
I
+ φ
I,F
)) = 3V
1
I
1
cos(φ
U
- φ
I
+ (φ
V,F
- φ
I,F
))
The angle error to be corrected results as:
ϕ
Corr
= φ
V,F
- φ
I,F
To rotate in the correct direction, the correction angle is considered with inverted sign inside the unit.
Functional Measured Values
You can use the following functional measured values to check the behavior of the protection function and to
support commissioning. The total power is represented as the measured value.
Measured Value Description
P1fast
Positive-sequence system active power
calculated per cycle
Angle correction influences the measured
value
Q1fast
Positive-sequence system reactive power
calculated per cycle
Angle correction influences the measured
value
P1avg
Positive-sequence system active power
calculated from P1fast over 16 cycles
Input value for Reverse-power protection
Q1avg
Positive-sequence system reactive power
calculated from Q1fast over 16 cycles
–
Application and Setting Notes
In the general functionality, you can adjust the parameter (_:2311:101) Angle correction. The param-
eter results from the angle error of the primary transformer. In SIPROTEC 5, the input transformers are cali-
brated so that the angle error is negligible. You can assume an error of < 0.1°. There is no difference between
a protection input and an instrument-transformer input.
i
i
NOTE
If you use class 0.2 instrument transformers on the primary side to avoid the influence of the angle, you
can connect a protection device with a protection current transformer without any problems.
Class 0.2 voltage transformers have a maximum admissible angle error of 10 min (0.17°). The angle error
of a class 0.2 measuring current transformer at rated current is approximately 10 min, at 0.2 I
rated
= 15 min,
and at 0.05 I
rated
= 30 min.
Parameter: Angle correction
•
Default setting (_:2311:101) Angle correction = 0°
To determine the correction angle via measurement with the primary system, follow the instructions in
chapter 11.14.2 Primary Test.
You can use the method that is explained in the following section to derive the necessary correction angle
from the transformer measuring reports.
6.38.3.2
Protection and Automation Functions
6.38 Reverse-Power Protection
SIPROTEC 5, Overcurrent Protection, Manual 811
C53000-G5040-C017-8, Edition 07.2017