In parameter 1512 the timer can be set, and in parameter 1515 this protection is enabled. In parameter 1516 the fail class is
decided. It is also possible to enable two relay outputs when the alarm occurs. The two relay outputs can be set in parameters 1513
and 1514.
3.7 Over-excitation
When heavy inductive loads are connected, over-excitation of the generator can occur. Alternatively, over-excitation can occur if the
load of a generator quickly changes from inductive to capacitive. Over-excitation can also occur in an application with more than one
generator if one of the generators' exciter fails. Over-excitation can overheat windings in the generator and create a failure over
time.
Example: Setting over-excitation
The engine is 2000 kW, and the alternator is 2500 kVA.
Calculate how many kvar the genset can export:
Use the kvar to calculate the percentage for parameter 1531: kvar/kW = 1500/2000 = 75 %.
When parameter 1531 is 75 %, the genset can export up to 1500 kvar. The alarm is activated when the load has crossed
the set point for the time in parameter 1532.
INFO
Option C2 (included in the standard AGC) includes capability curve protection with 12 configurable points. If this simple
over-excitation protection is not good enough, use Option C2.
3.8 Voltage-dependent (restraint) over-current
This protection is used when the generator must be tripped due to a fault situation that creates a reduced generator voltage, e.g. a
voltage collapse. During the voltage collapse, the generator can only produce part of its usual rating. A short-circuit current during a
voltage collapse can even be lower than the nominal current rating.
The protection will be activated based on the overcurrent set point as a function of the measured voltage on the generator voltage
terminals.
The result can be expressed as a curve function where the voltage set points are fixed values and the current set points can be
adjusted (menu 1100). This means that if the voltage drops, the overcurrent set point will also drop.
DESIGNER'S HANDBOOK 4189341275A EN Page 72 of 196
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