Controller type Inhibit(s)
SHORE connection ACM wire break
BUS TIE breaker ACM wire break
Busbar voltage unbalance example
The busbar has a nominal voltage of 230 V. The L1-L2 voltage is 235 V, the L2-L3 voltage is 225 V, and the L3-L1 voltage
is 210 V.
The average voltage is 223.3 V. The difference between the phase-to-phase voltage and the average is 12.7 V for L1-L2,
2.7 V for L2-L3 and 13.3 V for L3-L1.
The busbar voltage unbalance is 13.3 V / 223.3 V = 0.06 = 6 %
3.5.4 [Busbar] over-frequency (ANSI 81O)
Protection
IEC symbol (IEC60617) ANSI (IEEE C37.2) IEC 61850 Operate time
Over-frequency f>, f>> 81O PTOF < 50 ms
The alarm response is based on the lowest fundamental frequency (based on phase voltage),
from the busbar. This ensures that the alarm only activates when all of the phase frequencies
are above the set point.
For the BUS TIE breaker controller, this is the frequency measured on busbar B.
Configure the parameters under Configure > Parameters > [Busbar] > Frequency protections > Over-frequency #, where # is 1
or 2.
Table 3.60
Default parameters
Parameter Range Busbar over-frequency 1 Busbar over-frequency 2
Set point 100 to 130 % of nominal frequency 105 % 110 %
Delay 0.00 s to 1 h 5.00 s 8.00 s
Enable Not enabled, Enabled Enabled Enabled
Latch Not enabled, Enabled Not enabled Enabled
Alarm 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 it controls.
Table 3.61
Default inhibits
Controller type Inhibit(s)
GENSET • Generator breaker open
EMERGENCY genset
• Generator breaker open
• Tie breaker open
• EDG handling blackout
DESIGNER'S HANDBOOK 4189340911K UK Page 82 of 521
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