Reverse Power of Diesel Generator Set
by Starlight Generator dieselgeneratortechThe
reason for reverse power of diesel generators
Generators can not be
synchronized completely at the moment of closing, because the voltage can not
be completely uniform or the phase angle frequency can not be fully
synchronized, and there may be fluctuations in the power grid, it absorbs a
little electricity from the grid, that is, there is a temporary reverse power
phenomenon, but soon when the load is brought up within the delay time of the
reverse power protection settings, reverse power will disappear. But if the
load is too slow, it is likely to expand the reverse power phenomenon and cause
diesel generator tripping.
Another possibility is
that the sudden drop or disappearance of oil pressure or other faults may cause
the main valve to close incorrectly, and at this time, the precise protection
and refusal to operate will lead to the generator terminal switch not tripping,
which will certainly lead to reverse power action.
At present, two sets of
independent reverse power protection devices are generally installed on large
generators, that means program tripping reverse power and simple electrical
reverse power protection, to limit the reverse power of generators, which
generally does not exceed about 10% of rated active power.
Generator reverse power
protection, also known as power direction protection, when the generator
appears reverse power (the external power points to the generator, that is, the
generator becomes the motor working condition), reverse power protection action
circuit breaker will trip. Three-phase voltage and two-phase current signals
need to be collected.
Generally speaking, the
power direction of the generator should be from the generator to the bus, but
when the generator loses excitation or for some other reasons, the generator
may be converted to the motor operation, that is, to absorb active power from
the system. This is the inverse power. When the inverse power reaches a certain
value, the protective action of the generator is either signaling or tripping.
Reverse
power protection action characteristics
1.The stator current
exceeds the normal value and the ammeter pointer will be severely blocked.
2.The pointer of the
stator voltmeter will swing rapidly.
3.Active power meter pointer
swings on the whole dial.
4.Rotor ammeter pointer
fast swing near normal value.
5.The generator emits a
whistle, and the change of the whistle corresponds to the swing frequency of
the instrument pointer.
6.The instruments of
other parallel generators also oscillate accordingly.
It is not certain how
much power the generator absorbs before tripping. It is decided by the setting
value of the protection device, which is usually a quadratic value.
Adjustment
of reverse power phenomenon caused by frequency
If the frequency of two
diesel generator sets is different and larger difference, the instrument
(ammeter, power meter) will show the value, the current of higher speed diesel
generator set will displays positive value, power meter also displays positive
power value. Otherwise, current and voltage value are negative.
At this time, the
generator will adjust the speed (frequency) of one of the diesel genset,
according to the indicator of the power meter, adjust the indicator of the
power meter to zero. Make the power indication of the two units both zero, so
that the rotational speed (frequency) of the two units is basically the same.
However, when the ammeter still has the indication, this is the reverse power
caused by the voltage difference.
Adjustment
of reverse power phenomenon caused by voltage difference
When the power meter
indication of both units is zero, and the ammeter still has the current
indication (i.e., the reverse-positive indication), the voltage adjustment knob
of one of the generating sets can be adjusted. According the indicator of
current meter and power factor to adjust. Adjust current meter indication to
zero, after current meter has not any indication, at this time, according the
indication of power factor meter to adjust power factor to lagging more than
0.5. Generally, it can be adjusted to about 0.8, which is the best state.
Above is our sharing
information about reverse power operation and protection in diesel generator,
hope it is helpful to every one. Starlight Power is a manufacturer of diesel
generator set, such as standby generator, emergency generator etc., covering
Cummins, Perkins, Volvo, Deutz, Yuchai, Shangchai, Weichai etc. Contact us
sales@dieselgeneratortech.com.
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Created on Oct 22nd 2019 01:56. Viewed 228 times.