FULL LOAD REJECTION
Russell W. Patterson
What is a generator full load rejection test?
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Karl Gross
generator set to continue to operate, when the generator output breakers
have been opened or excitation is lost. This results in the machine
attempting to overspeed (no load after the breakers open) and the inlet
and intercept valves (if any) having to immediately modulate to a near
closed or closed position.
Few machines (>1000 MWe) can do this. Some facilities may refer to near
full load rejection as a full load rejection, e.g. a nuclear plant
may continue to carry in-house loads after a load rejection.
A variation on this is the test to assure the boiler/nuclear reactor
system can continue to operate after a load rejection. This requires
some means of dumping the steam being generated to the condenser or the
atmosphere, and quickly ramping power down (heat generation / steam
flow), until the turbine can be restored.
Hope that helps. BTW, these tests are fun to watch! Bang, woooosh,
roar, etc. <grin> "MORE POWER"
Bill Kohn
>A full load rejection test usually refers to the capability of a turbine
>generator set to continue to operate, when the generator output breakers
>have been opened or excitation is lost. This results in the machine
>attempting to overspeed (no load after the breakers open) and the inlet
>and intercept valves (if any) having to immediately modulate to a near
>closed or closed position.
Not for nuclear plants. See below.
>Few machines (>1000 MWe) can do this. Some facilities may refer to near
>full load rejection as a full load rejection, e.g. a nuclear plant
>may continue to carry in-house loads after a load rejection.
Not quite true. GE BWR's for sure, and I'm fairly certain for Western
designed PWRs, can withstand a full load rejection. In this case, this
means that no safety paramenters are exceeded, but the turbine-generator
and the reactor both trip.
>Hope that helps. BTW, these tests are fun to watch! Bang, woooosh,
>roar, etc. <grin> "MORE POWER"
Agreed that these are fun to watch since the main turbine trips and on a
1000+ MW turbine, those stop valves closing are heard/felt throughout
the plant.
Bill Kohn
Oak Ridge, TN
Martin J. Bernard III
phone of the editor of T&D Magazine (they are somewhere in Kansas?).
Thanks!
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Bert Hoffman
>What is a generator full load rejection test?
The generator load is increased to 100%, then the unit circuit breaker
is opened. This typically is used to check over-speed of the unit, and
proper shutdown. It can be very impressive if you are doing a full
load rejection test on an entire powerhouse. It can put barges into a
parking lot.
Bob McNair
: Karl Gross <ka...@indirect.com> wrote:
: >Hope that helps. BTW, these tests are fun to watch! Bang, woooosh,
: >roar, etc. <grin> "MORE POWER"
: Agreed that these are fun to watch since the main turbine trips and on a
: 1000+ MW turbine, those stop valves closing are heard/felt throughout
: the plant.
: Bill Kohn
: Oak Ridge, TN
I've been present for these kinds of tests on hydro generators and
diesel-driven generators.As long as everything goes right, they are
indeed fun to watch. Full load rejection (and its companion load
acceptance or block loading) can really make a 5MW (6500HP) diesel engine
rock (or grunt as the case may be).
For a real good time though, I think full load rejection on a >100MW
turbine in a hydro generating plant is a strong contender. Noise. Dust
rising/falling everywhere. Huge sigh of relief that you're not suddenly
being transported downstream by tons of water. Amazement that tons of
concrete can shake without falling apart. (New construction only - I
don't know if this test is done on old & refurbished units. Don't think
I'd want to be in the plant at the time.)
Probewell
9800, Metcalf Ave., Overland Park, KS 66212-2215
Tel: 913 341-1300
Fax: 913 967-1904
Robert B. Callery
generator set, that while running at full generator electrical output, the
generator breaker is opened, and the turbine (steam, combustion, etc..) does
not overspeed or trip but regulates it's speed at 100% or full speed no load
condition.
The functional test is usually required on new units as a condition of
acceptance during the start-up phase.
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Ming F. Sit
>
> A full load rejection test is,as the name implies, a test of a turbine
> generator set, that while running at full generator electrical output, the
> generator breaker is opened, and the turbine (steam, combustion, etc..) does
> not overspeed or trip but regulates it's speed at 100% or full speed no load
> condition.
>
Depending on your droop setting, the governor actually will regulate the turbine
speed ABOVE the rated speed, assuming no subsequent adjustment to the governor.
E.g. if your droop setting is 4%, the regulated STEADY STATE speed is 104% of the
rated speed after full load rejection. The governor and valves are supposed to act
quickly enough to prevent the overshoot to trigger the overspeed trip (usually
110-111% of rated speed) of the turbine.
The system I used to work is a ~1200MW system with a tie line to a ~3000MW system.
We were commissioning a 350MW coal-fired steam unit. We could not take the risk of
a full load rejection so we did a 30% and 60% rejection and (dangerously)
extrapolate the test result. And we boosted the system frequency to 50.50Hz (50Hz
system) before the test.
AHamil1857
It's not worth the cost of rolaids, pacemakers and
underwear.
Surfing the net from the control room;
68mwARTHUR
eng.ali...@gmail.com
If generator breaker opens at full load, (due to a disturbance on the grid, for example) will the GT typically avoid an over speed trip and instead reduce fuel fast enough to operate at full speed no load?