Deif AGC-4 Mk II Designers Handbook

3.3 Loss of excitation
To prevent damage to the generator because of a pole slip, the AGC can trip a breaker if loss of excitation occurs. The protection is
configured in menu 1520.
The percentage in parameter 1521 is the maximum percentage of imported kvar compared to the nominal kW of the genset.
Genset example
The genset has a nominal of 1000 kW. Parameter 1521 is 15 %. This means that if the genset is 150 kvar capacitive or
more, the timer in parameter 1522 starts. When the timer expires, an action occurs. This action/fail class is configured in
parameter 1526.
To configure the percentage correctly, a calculation must be made. The operating chart for the generator is needed. An example of
an operating chart for a generator is shown below. The blue block shows the engine overload at a power factor of 0.8.
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18 %
Engine overload region for power factor = 0.8
The alternator 100 % load is the outer circle, and the engine 100 % load is the bottom of the blue block. With the operating chart it is
possible to see where the alternator-safe line is closest to the 1.0 PF line. In this operating chart each vertical line represents 10 %,
and so the point closest to 1.0 PF is 18 %. Use the nominal alternator values and the nominal engine values to do the calculations.
Calculating parameter 1521
The reading of 18 % is used. The alternator has a nominal power of 2500 kVA, and the engine has a nominal power of
2000 kW. The distance between the reading and the 1.0 PF line represents a power: 2500 kVA * 18 % = 450 kvar
The setting of parameter 1521 can now be calculated: 450 kvar / 2000 kW = 22.5 %
INFO
This protection does not prevent engine overload. To protect against engine overload, configure the generator overload
protections in menus 1450 to 1490.
DESIGNER'S HANDBOOK 4189341275A EN Page 69 of 196

Deif AGC-4 Mk II Specifications

General

Brand	Deif
Model	AGC-4 Mk II
Category	Controller
Language	English