ABB RELION REB500 Technical Manual page 44

Section 5
Bay protection functions
It is important for an overcurrent starter, which has picked up, to reliably reset at the
maximum load current
Taking due account of the reset ratio of 0.95, the lowest permissible setting is given by:
( Istart
The maximum setting
the end of the next section of line:
( Istart
Should the above relationships result in
underimpedance starters must be used instead.
Underimpedance starters
The underimpedance starters are enabled by selecting
following parameters then have to be set:
• XA
• XB
• RA
• RB
• RLoad
• AngleLoad
The parameters
38
IBmax , if for example the fault is tripped by a downstream protection.

I I

B max A
) 1.25

min
0.95 I
N
(IStart)max is derived from the minimum fault current IK for a fault at

) I I
max K min N
RLoad and AngleLoad define the permissible load area.
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(IStart)max being lower than (IStart)min , the
UZ as the StartMode parameter. The
1MRK 505 406-UEN B
GUID-AB1404EC-2679-4CA9-AA8B-F84A320C432E v1
Bay protection functions REB500
Technical manual