Controller type
Inhibit(s)
SHAFT generator
•
Shaft breaker open
SHORE connection
•
Shore breaker open
3.5.5 [Busbar] under-frequency (ANSI 81U)
Protection
IEC symbol (IEC60617)
ANSI (IEEE C37.2)
IEC 61850
Operate time
Under-frequency
f<, f<<
81U
PTUF
< 50 ms
The alarm response is based on the highest fundamental frequency (based on phase voltage),
from the busbar. This ensures that the alarm only activates when all of the phase frequencies
are below the set point.
For the BUS TIE breaker controller, this is the frequency measured on busbar B.
Set
point
Value
time
Delay
Configure the parameters under
Configure > Parameters > [Busbar] > Frequency protections > Under-frequency #
, where # is
1 or 2.
Table 3.62
Default parameters
Parameter
Range
Busbar under-frequency 1
Busbar under-frequency 2
Set point
80 to 100 % of nominal frequency
96 %
93 %
Delay
0.00 s to 1 h
10.00 s
5.00 s
Enable
Not enabled, Enabled
Enabled
Enabled
Latch
Not enabled, Enabled
Not enabled
Enabled
Action
Warning
Trip [Breaker]*
*Note: For the EMERGENCY genset controller, this alarm action trips the tie breaker to the main busbar. For other controllers: The
controller trips the breaker to the equipment that it controls.
Table 3.63
Default inhibits
Controller type
Inhibit(s)
GENSET
•
Generator breaker open
•
ACM wire break
EMERGENCY genset
•
Generator breaker open
•
Tie breaker open
•
EDG handling blackout
SHAFT generator
•
Shaft breaker open
•
ACM wire break
SHORE connection
•
Shore breaker open
•
ACM wire break
BUS TIE breaker
•
ACM wire break
DESIGNER'S HANDBOOK 4189340911K UK
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