tion of the surge arrestors is not allowed to use the
common earth connection of the plant, it shall have
its own earth.
Function: Protecting alternator, it is not doing any
action, which is interfering with the duty, it is neces-
sary to have a counter, where it is possible to see
how many hits it has taken.
Automatic Voltage Regulator AVR
The AVR can be delivered in two versions:
▪ Analogue
▪ Digital
If the analogue AVR is selected, it is necessary to
consider, which type of AVR is used in the existing
generator sets to secure the correct reactive load
shearing.
If the digital AVR is selected, it is necessary to con-
sider it is supplied with the power-factor measure-
ment module.
Stand alone
Is the GenSet running as a “Stand Alone” Type
which means there is the only running a single Gen-
Set, the AVR has to be adjusted for Constant volt-
age.
Parallel running
The GenSet are running in parallel with other Gen-
Sets or the grid.
The AVR has to be equipped with a voltage drop,
compensation lines power-factor regulator.
Parallel running with voltage droop
The AVR has to be equipped with a voltage droop
function; this means the generator AVR is adjusting
(Decreasing the voltage linear) the voltage by
increasing load, the AVR are dropping the voltage
from rated voltage by no-load to max – 2,5% droop
at full load.
Parallel running with the grid by Power
factor (Cos phi)
The AVR has to be equipped with a power factor
regulator; this means the generator is adjusting the
voltage after the Grid voltage and keeping the
“Power factor” from the GenSet constant.
This system can be used in ships or smaller power
plants, in the simple standard version, if the new
GenSet I relation to the total installed power (30%),
and the existing alternators have very old AVR’s .
Parallel running with other GenSets with
Compensation Lines
Older alternators are using compensations lines, the
AVR have to be selected specially for this.
It is not possible to run a standard analogue AVR
with voltage droop in parallel with GenSet plants
using compensations lines.
It is also possible to use digital regulators, they are
then using a power factor mode.
Digital regulators (AVR)
Digital Regulators are equipped with many protec-
tion features to protect the alternator.
But they are not activated automatically. It is neces-
sary to state it in the contract:
Who is responsible for the adjustment: the people
who have the best information about how much the
generator can withstand is the generator manufac-
turer. They shall be forced to make the adjustments
and control the functions before the generator is
leaving the test bench in the generator factory.
The functions from the protection features can be
allocated to some configurable relay outputs (1,2 or
3 pcs with priority) in the alternator AVR, which can
give signals to the supervision system in the Switch-
board.
It has to be decided by the manufacturer, if the out-
puts have to result in an alarm, switch of the main
circuit breaker, or switch of the main circuit breaker
and stop of the GenSet.
The following has to be stated from the generator
buyer by order:
It is recommended to use the protection features in
the alternator AVR and following alarms can be
generated on configurable relay outputs.
▪ Rated voltage UmN (Volt)
▪ Rated current ImN (amp)
▪ Largest inrush current and accepted voltage
drop (amp), (Volt)
▪ Power factor PFmN (pu)
▪ Apperent power SmN (kVA)
MAN Diesel & Turbo
3700383-8.2
Page 3 (6)
Power Management - Alternator protection
B 17 00 0
L23/30DF, L28/32DF, V28/32S, L28/32S, L28/32H, L27/38S, L27/38, L23/30S,
L23/30H, L21/31S, L21/31, L16/24S, L16/24
2015.11.17
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