Woodward 2301D, Инструкция по установке и эксплуатации, Страница: 92 / 130

2301D/2301D-EC Digital Control Manual 26247
84 Woodward
When the system load is high, the oncoming generator will load at a fast rate to
assume it share of the load quicker. In the isochronous mode (CB Aux input
closed), closing the load contact ramps the load set point from no-load to the
load sharing setting. Opening the load contact (unload) ramps the load to the
unload trip level setting. At the unload trip level a Circuit Breaker open signal is
issued. Closing the baseload contact ramps the load set point from no-load or the
load sharing setting to the baseload reference. Opening the baseload contact
ramps the load to the load sharing setting. When in baseload operation, the
baseload reference determines the load on the generator without regard to other
units connected to the same load. When the generator is carrying less load than
the base load reference, the load bias is positive and the closed loop path
increases the fuel to the engine. When the generator is carrying more load than
the base load reference, the load bias is negative and the closed loop path will
decrease the fuel to the engine. As the fuel to the engine is changed, the load
and/or speed will change until the engine speed exactly matches the biased
speed reference. At this steady state base load condition, the load bias is
virtually zero and the biased speed reference, rated speed reference, and engine
speed are virtually equal.
Opening the baseload input contact ramps the generator load from base load
back into isochronous load sharing. However, opening the load input contact
(unload) instead, ramps the generator load from the base load setting to the
unload trip level where a breaker trip signal is issued after a tunable time delay.
In isolated bus applications, a brief speed transient may occur when
the load sharing relay closes following transfer from baseload back
into isochronous load sharing.
It is possible for the control to be in base load control while supplying power to a
load which is isolated from the infinite bus. The capability of the engine generator
must be considered when operating this way. As an example consider two
generators, one capable of providing 1200 kW and one capable of providing 600
kW. If the combined load demand to these generators is 750 kW while the 1200
kW generator is in steady state isochronous load sharing and the 600 kW
generator is in steady state base load with a set point of 250 kW, the 1200 kW
generator will again be carrying 500 kW and the 600 kW generator will again be
carrying 250 kW. However, now as the total load demand increases only the
1200 kW generator will respond to the increase. At a combined load demand of
1450 kW, the 1200 kW generator will carry 1200 kW while the 600 kW generator
in base load will still be carrying 250 kW. If the load demand exceeds 1450 kW,
the steady state frequency of the bus will decrease and the load supplied by
each individual generator will increase.
Soft Loading
The load command discrete input contact controls soft loading. If the load
command discrete input is closed when the breaker (CB AUX) input contact
closes, the generator will soft load to the reference level of the mode selected
(load sharing or base load). If the load command discrete input is open (unload)
when the breaker (CB AUX) closes, the generator will immediately load to the
Unload Trip Level set in the KW Setting menu. When the load command discrete
input is closed, the generator will soft load to the reference level of the mode
selected (load sharing or base load). The ramp rate is adjustable.