The screens for the grid
controls show the status of the section and feeder breakers. The following
is a summary of items shown on the screens.
Section Breaker status
Feeder Breaker status
Status of the CHP Mimic Panel
Status of the BMS Panel
Inputs form the Hardwired I/O 11KV Breakers
Inputs for the Hardwired Transducers as listed
Voltage and Frequency of each bus
MW, Amps and Power Factor Alternators 1 & 2
The
following selections are available for operation of the electrical grid.
|
Open Breaker |
Individual Open selections are
provided for each feeder breaker. |
|
Close Breaker |
Individual Close selections are
provided for each feeder breaker and bus coupler. |
Loadshedding
Two graphics are
provided for Load shedding. The screens display the load shed statuses for
the individual devices and feeders. The following information is shown for
each individual device or feeder breaker:
Activate On
the MMI this field is selectable. A device can be manually deactivated
from the Load shed logic. This typically would only be done while
performing maintenance.
Status This field shows
whether the breaker is open (green) or closed (red). If a breaker is open
it is automatically taken out of load shedding.
Trip This field
shows if a breaker has been tripped (flashing red) due to load shedding.
This field will turn off only after a RESET has been issued. This field is
for indication only. The breaker can still be closed even if a RESET has
not been issued.
Load This field
displays the load of each breaker in MW that is expected to be shed in the
event of a load shed. The Feeder Breakers utilize a current sensor.
Priority This field
shows the order in which breakers will be tripped during a load shed. The
priority with the lowest number will be shed first.
Test The field is
selectable on the MMI. When this field is activated and the Master Test
Switch is selected then the breaker will be shed.
There is special logic
for load shedding this will be determined at the functional design
stage of the project .
In a split bus
condition, a device normally powered by a feeder breaker on one side of
the bus is assumed powered through the feeder breaker on the other side of
the bus if the normal feeder breaker is open. For example if a feeder is
normally powered on the right side of the bus is detected running and the
right hand feeder breaker is open then it will be assumed the pump is
powered from the left side of the bus.
The
following selections are available for loadshedding.
|
Loadshed Enable |
This enables or disables the entire
load shedding system. The switch is automatically turned off if the
load shed priorities are entered improperly, or there are generators
connected to both the Main and Reserve buses or a Load shed Test is in
progress. |
|
Reset |
Any breakers that are tripped by
the load shedding system will remain flashing until this button is
selected. |
|
Loadshed Test |
Activating a Test will immediately
trip any breakers that are selected for testing. The Load shed Enable
switch will be turned off. |
|
Breaker Activate
|
This activates or deactivates
individual devices or feeders from the load shed system. |
|
Breaker Test |
This activates or deactivates
individual devices or feeders for the Load shed Test function. |
Generator
Controls
The screen for the generator controls
will show the performance for Alternators 9G-1, 8G-1, 8G-2 units.
Also the system will be able to raise & lower the setting of the AVR
and Governor control from this system. In addition the following will
be displayed.
|
Y.E. 11 KV Incomer No 1
|
KV, KW, FREQ, P.F.,
Current. |
|
Y.E. 11 KV Incomer No 2 |
KV, KW, FREQ, P.F.,
Current. |
|
Alternator 1 |
KV, KW, FREQ, P.F.,
Current. |
|
Alternator 2 |
KV, KW, FREQ, P.F.,
Current. |
|
Alternator 8G-4 |
MVAr & MW |
Synchronization
Synchronizing the section buses can be
accomplished from the Grid Overview 1 screen.
Left/Right Section Breaker
To synchronize and close the Left/Right
Section breaker, select Close on the L1 breaker box on the screen. The
frequency setpoint to the generators that are in Load sharing on the Right
bus will be adjusted to bring the phase to 0 degrees. When the breaker is
in phase, the breaker will be closed. Ten synch check relay have been
included to provide the final control permissive.
Bus Configurations
Bus Configuration
The power capability of each of the
running generators are added together to calculate the system capability.
The megawatt production of each of the
running generators are added together to calculate the system load.
Split Bus Configuration
A split bus configuration is assumed if
the Right / Left bus coupler (L1) is open.
The power capability of the generators
are added together to calculate the left bus capability.
The megawatt production of the
generators are added together to calculate the left bus system load.
The power capability of the generators
are added together to calculate the right bus capability.
The megawatt production of the
generators are added together to calculate the right bus system load.
Instantaneous Load shedding
Instantaneous Load shedding Permissives
The following permissives are required
for instantaneous load shedding:
Load shed Enabled
Either all or none of the online
generators are connected to the Main Bus
Peer to Peer communication healthy to
all UCP’s that are On-Line
Priority list is correctly entered.
Instantaneous Load shedding Logic
If a generator trips, the current
megawatt production is compared to the total capacity of the running
generators. If the megawatt production exceeds approximately 90% of the
total capacity, the excess load will be shed.
The priority of each device is
selectable. Each device priority must be unique and a number from 1 to 30
or load shedding will be disabled. Since this logic concerns load
shedding, the number 1 is the lowest priority and 30 the highest priority.
Therefore Priority 1 is tripped first in a load shed and Priority 30 is
tripped last.
The Megawatt load of each feeder
breaker is estimated from an AC current transducer, power factor is
estimated. Loads that are not measured are manually input based on the
normal operating duty in MW. If the actual current for the individual
loads is not available then the load will be estimated. Only the necessary
amount of load will be shed.
Time
based (Frequency) loadsharing
Time Based
Loadshedding Permissives
The following
permissives are required for time based load shedding:
Loadshed Enabled
Frequency is decreasing
The Time Delay (300 ms) after a Previous Time Based Load shed has expired
Either all or none of the online generators are connected to the Main Bus
Either all or none of the online generators are connected to the Reserve
Bus
Priority list is correctly entered.
Time Based Load
shedding Logic
Time Based or Frequency
Load shedding occurs if the permissives listed above are satisfied and the
criteria below is met:
If the frequency is less than 49.5 hz (96%) then 10% of the load will be
shed.
Progressive Loadshedding
Progressive
Loadshedding Permissives
The following
permissives are required for Progressive load shedding:
Load shed Enabled
Either all or none of the online generators are connected to the Main Bus
Priority list is correctly entered.
Progressive Load Shedding Logic
Progressive Load shedding occurs if the
permissives listed above are satisfied and the criteria below is met:
If the Megawatt Load increases above
95% of the available capacity then an estimated load will be
instantaneously shed to bring the Megawatt Load below 90% capacity.
Auto
Synchronizing - Bus Couplers
A common set of synchronizing hardware
is used for both of the bus coupler breakers. The hardware required for
synchronizing consists of a phase transducer, sync check relay, and a
Multilin relay consisting of three-phase voltage and frequency.
The Right Bus is always connected to
one side of the phase transducers and sync check relay. The other side of
the phase transducer and sync check relay is either connected to the Left
Bus or the Reserve Bus. This is determined by a bus selector relay.
If the Reserve Bus Coupler is detected
closed and the Main / Left Bus Coupler is open then the bus selector relay
is set to the Left Bus. If both Bus Couplers are open then the bus
selector relay remains in the last position. If a breaker close command is
selected and the bus selector relay is in the wrong position then it will
change to the correct position.
If the Right / Left bus coupler (L1) is
open then the frequency setpoint to the right bus generators will be
adjusted to maintain a 0 degree phase angle. The breaker will be closed if
the following are met::
Bus Selector is in the correct position
Sync Check Relay is Energized
If either bus is dead there must be no
generator breakers closed to the bus
If both buses are live then the phase
angle must be within 5 degrees
If both buses are live then the
frequency must be matched within .05 hz.
If the Right / Reserve bus coupler (R1)
is open the breaker can be closed if the following are met:
Bus Selector is in the correct position
Sync Check Relay is Energized
If either bus is dead there must be no
generator breakers closed to the bus
If both buses are live then the phase
angle must be within 5 degrees
If both buses are live then the
frequency must be matched within .05 hz.
If both buses are live it indicates
that generators are connected to both the right and reserve bus. Load
sharing is not permitted in this instance. Therefore the frequency of the
right bus must be manually increased to facilitate the phase angle and
frequency requirements.
Auto synchronizing - Generators
For the most part the Governor control
system for each generator performs the Auto Sync functions.
