Siemens SIPROTEC 7UM62 - Page 95

Functions
2.12 Unbalanced Load (Negative Sequence) Protection (ANSI 46)
SIPROTEC, 7UM62, Manual
C53000-G1176-C149-7, Release date 03.2010
95
Conversion to Secondary Values
The factor K can be derived from the unbalanced load characteristic according to the figure below by reading
the time corresponding to the FACTOR K at the point I
2
/I
N
= 1.
Example:
t
perm
= 20 s for I
2
/I
N
= 1
The constant K
primary
= 20 s determined in this way is valid for the machine side (primary side).
The factor K
primary
can be converted to the secondary side by means of the following formula:
The calculated asymmetry factor K
sec
is set as FACTOR K at address 1704.
Example:
I
N Mach
= 483 A
I
N CT prim
= 500 A
Factor K
primary
= 20 s
Setting value at address1704:
Figure 2-25 Example of an Unbalanced Load Characteristic Specified by the Machine Manufacturer