Siemens 6MD85, Manual

Page: 1071 / 1256

Testing the Negative-Sequence Current
When testing, keep in mind that the measured values are standardized. In the setting I
2
/I
rated, obj.
, they are
standardized to the rated current of the protected object. The conversion to secondary transformer values is
accomplished in the device.
EXAMPLE:
The threshold value is set to 10 % of the protected object.
Transformer: 100 A/1 A
Rated current of the protected object: 80 A
Action Steps
²
At a setting of 10 %, the primary negative-sequence current is 80 A • 10 %/100 % = 8 A.
For a current transformer ratio of 100, test with a secondary current of 0.08 A.
²
With a transformer of 100 A/5 A, the test current is higher by the factor 5. Test with 0.4 A. The pickup
value is at 1.1 • 0.4 A = 0.44 A.
²
If deviations occur during the testing, you must check whether the power-system data were entered
correctly.
i
i
NOTE
Keep in mind that the function works starting from the set minimum current.
10.6
Functional Tests
10.6 Testing the Negative-Sequence Current
SIPROTEC 5, High-Voltage Bay Controller, Manual 1071
C53000-G5040-C015-9, Edition 11.2017