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The guide is used in the following manner:
Find the point where the
vertical line (determined by the maximum current in any of the phases
and expressed in percent of rated current) crosses the horizontal
line (determined by the minimum current in any of the phases and
expressed in percent of rated current). Ensure the point where these
two lines intersect is within the permissible allowable unbalance region
for safe operation of the generator.
Figure 16 Guide to Allowable Phase Unbalance
Loss of field excitation can result in the unit operating out of
synchronization with the system when operating in parallel. This has
the effect of producing high currents in the rotor, which will cause
damage very quickly. Protective relays should be considered to open
the circuit breaker.
Idling
Unless the voltage regulator has V/Hz protection built in, having the
generator set in operating mode while idling the engine can cause
permanent equipment damage. If engine adjustments require that
the engine be run at idle speed and the regulator does not have V/Hz
protection, make the generator regulating system inoperative during
idling by one of the following methods:
•
When the generator is provided with a voltage shutdown switch,
be sure the switch is set to the idle position while the engine is
running at idle speed.
•
Where the generator set is provided with field circuit breakers,
set the circuit breaker to the off position while the generator is
running at idle speed.
•
Where the generator set is provided with an automatic/manual
control switch that has an off position, switch it to off while the
engine is running at idle speed.
•
Where the generator set does not have any of the above options,
remove the wires from the voltage regulator input power
terminals when the engine is running at less than rated speed.
0
20
40
60
80
100
20
40
60
80
100
Max. current in any phase (% of rated)
Min. current in any phase (% of rated)
Excessive
unbalance
Allowable
unbalance
Содержание 4P10
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