Voltage/Protection & Control Flashcards
What does active or real power do
performs the active work
What does reactive power do
builds the magnetic fields that enable power to do the work
Voltage control is the control of what
reactive power flow
Equation to determine shunt capacitor output
MVARactual = MVARrated x {Vactual / Vrated}2
Why are series capacitors used
used to reduce the inductive reactance on transmission line, thus increasing the line transfer power capability
Static VAR compensators can be used for what
control both capacitance and inductance var
can transmission lines be removed / added to service has a form of voltage control
yes, only after engineering has perform studies to determine there will not be a negative impact
what is surge impedence loading (SIL)
SIL is the point where the active power flowing on a power line reguires 0 MVAR from the rest of the system to
what is below SIL
When load is light, the line becomes more capacitive, producing MVAR
what is above SIL
when load is heavy, the line becomes more inductive, absorbing MVAR
under what conditions shall the TO have sufficient reactive resources
under normal and contingency conditions
What happens when a AVR is out of service
the TO will direct the GO to maintain or change either its voltage schedule or it reactive schedule
who notifies who when the status or capability changes of either a generator or AVR
GO notifies TO
Ferranti effect raises the voltage where
on the line and the bus at the closed end
how long does a GO have to notify a TO of generator changes like AVR status
30 mins
what effect is there when you adjust ULTC when there is not enough primary side voltage
Lowers ULTC primary voltage, there is little to no effect on secondary voltage and could lead to voltage collapse
How does reactive power flow
when volatge is on schedule (power angles low, below 10 degress) MVAR will flow from the high to low voltage. When power angles are high MVAR will flow from the low to high voltage
TO’s and GO’s coordinate their voltages schedules to…
ensure they do not burden neighboring TO’s with excessive power flow across the tie lines
What are types of protective relays?
Overcurrent, ground, differential, distance and monitoring (temp alarms)
What are types of auxiliary relays?
tripping, lockout, timers, re-closing and regulating (like AVR)
distance relay
21
sync relay
25
Instantaneous overcurrent
50
timed overcurrent
51
directional overcurrent
67
lockout relay
86
differential relay
87
distance relays remove what kind of fault
phase to phase
what kind of zone is a differential relay
closed zone, power in must equal power out
what is the most frequently type used protection
ground
zones of protection, zone 1 covers how much of the transmission line
90% and trips instantaneously if detects fault within its zone
zones of protection, zone 2 covers how much of the transmission line
120-150%, it is on a time delay and considered a backup to zone 1
zones of protection, zone 3 covers how much of the transmission line
150-300% is on a time delay set longer then zone 2, also backup to zone 1&2
overcurrent relays are used as backup to what relays
distance and differential
what do synch check repays monitor
frequency, voltage and phase angle
who is notified if a protective relay or equipment failure reduces system reliability
the TO shall notify its RC and other affected TO’s and BA’s
transfer trip signals are a form of pilot relaying. what are some communication channels pilot relays use?
pilot wires, lowerline carrier, satellite, fiber optics, microwave and telephone lines
What type of Mvar is ultilized first
Shunt capacitors to increase generator dynamic reactive reserve
