Rockwell Automation 865 Differential Protection Relay - Manual (Page 104)

4-12 Supporting
Functions
865-UM001A-EN-P – July 2009
Example 1:
If there has been no external sync and the relay's clock is leading
sixty-one seconds a week and the parameter AAIntv has been zero,
the parameters are set as
s AAIntv
Lead AvDrft
9 . 9
61
8 . 604 =
=
=
With these parameter values the system clock corrects itself with
–1 ms every 9.9 seconds which equals 61.091 s/week.
Example 2:
If there is no external sync and the relay's clock has been lagging
five seconds in nine days and the AAIntv has been
9.9 s, leading, then the parameters are set as
6 . 10
3600 24 9
5000
9 . 9
1
1
=
⋅ ⋅
−
=
NEW
AAIntv
Lead AvDrft =
NOTE:
When the internal time is roughly correct – deviation is less
than four seconds – any synchronizing or auto-adjust will never turn
the clock backwards. Instead, in case the clock is leading, it is softly
slowed down to maintain causality.