Voltage/Protection & Control

Question 1

What does active or real power do

Answer 1

performs the active work

Question 2

What does reactive power do

Answer 2

builds the magnetic fields that enable power to do the work

Question 3

Voltage control is the control of what

Answer 3

reactive power flow

Question 4

Equation to determine shunt capacitor output

Answer 4

MVARactual = MVARrated x {Vactual / Vrated}2

Question 5

Why are series capacitors used

Answer 5

used to reduce the inductive reactance on transmission line, thus increasing the line transfer power capability

Question 6

Static VAR compensators can be used for what

Answer 6

control both capacitance and inductance var

Question 7

can transmission lines be removed / added to service has a form of voltage control

Answer 7

yes, only after engineering has perform studies to determine there will not be a negative impact

Question 8

what is surge impedence loading (SIL)

Answer 8

SIL is the point where the active power flowing on a power line reguires 0 MVAR from the rest of the system to

Question 9

what is below SIL

Answer 9

When load is light, the line becomes more capacitive, producing MVAR

Question 10

what is above SIL

Answer 10

when load is heavy, the line becomes more inductive, absorbing MVAR

Question 11

under what conditions shall the TO have sufficient reactive resources

Answer 11

under normal and contingency conditions

Question 12

What happens when a AVR is out of service

Answer 12

the TO will direct the GO to maintain or change either its voltage schedule or it reactive schedule

Question 13

who notifies who when the status or capability changes of either a generator or AVR

Answer 13

GO notifies TO

Question 14

Ferranti effect raises the voltage where

Answer 14

on the line and the bus at the closed end

Question 15

how long does a GO have to notify a TO of generator changes like AVR status

Answer 15

30 mins

Question 16

what effect is there when you adjust ULTC when there is not enough primary side voltage

Answer 16

Lowers ULTC primary voltage, there is little to no effect on secondary voltage and could lead to voltage collapse

Question 17

How does reactive power flow

Answer 17

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

Question 18

TO’s and GO’s coordinate their voltages schedules to…

Answer 18

ensure they do not burden neighboring TO’s with excessive power flow across the tie lines

Question 19

What are types of protective relays?

Answer 19

Overcurrent, ground, differential, distance and monitoring (temp alarms)

Question 20

What are types of auxiliary relays?

Answer 20

tripping, lockout, timers, re-closing and regulating (like AVR)

Question 21

distance relay

Answer 21

21

Question 22

sync relay

Answer 22

25

Question 23

Instantaneous overcurrent

Answer 23

50

Question 24

timed overcurrent

Answer 24

51

Question 25

directional overcurrent

Answer 25

67

Question 26

lockout relay

Answer 26

86

Question 27

differential relay

Answer 27

87

Question 28

distance relays remove what kind of fault

Answer 28

phase to phase

Question 29

what kind of zone is a differential relay

Answer 29

closed zone, power in must equal power out

Question 30

what is the most frequently type used protection

Answer 30

ground

Question 31

zones of protection, zone 1 covers how much of the transmission line

Answer 31

90% and trips instantaneously if detects fault within its zone

Question 32

zones of protection, zone 2 covers how much of the transmission line

Answer 32

120-150%, it is on a time delay and considered a backup to zone 1

Question 33

zones of protection, zone 3 covers how much of the transmission line

Answer 33

150-300% is on a time delay set longer then zone 2, also backup to zone 1&2

Question 34

overcurrent relays are used as backup to what relays

Answer 34

distance and differential

Question 35

what do synch check repays monitor

Answer 35

frequency, voltage and phase angle

Question 36

who is notified if a protective relay or equipment failure reduces system reliability

Answer 36

the TO shall notify its RC and other affected TO’s and BA’s

Question 37

transfer trip signals are a form of pilot relaying. what are some communication channels pilot relays use?

Answer 37

pilot wires, lowerline carrier, satellite, fiber optics, microwave and telephone lines

Question 37

What type of Mvar is ultilized first

Answer 37

Shunt capacitors to increase generator dynamic reactive reserve