10 - 22 Flashcards
Which one of the following items would not cause a low lagging power factor:
A) Induction Motor
B) Transformer exciting current
C) Transmission lines
D) Shunt reactors
C) Transmission lines
page 2
In order to maintain losses as low as possible, what would be the best location for sources of VARs?
A) At the generation plant
B) On the high voltage sid of receiving or distributing stations
C) Adjacent to the customer’s equipment
D) All of the above
C) Adjacent to the customer’s equipment
page 7
Which of the following changes in system operating conditions would tend to change a lagging power factor from .85 to .90?
A) A decrease in the field excitation on a synchronous condenser
B) A decrease in the field excitation on a synchronous generator
C) A reduction in the excitation for the available synchronous motors
D) An increase in the field excitation of a synchronous condenser
D) An increase in the field excitation of a synchronous condenser
page 3
A synchronous condenser which is in operation at the time of a system disturbance:
A) Will have no affect on abnormal conditions
B) May tend to aggravate abnormal conditions
C) Will have a stabilizing effect on the system
D) Will relay off the line and shut itself down
C) Will have a stabilizing effect on the system
page 3
During off-peak periods on a power system it may sometimes be necessary to operate synchronous condenser under excited:
A) To help maintain system frequency while generators are shut down.
B) To replace capacitors that have been automatically switched out of service
C) Because long term transmission lines cause static capacitive effect which may over balance the inductive effect of the load during that time
D) So that there is plenty of capacity available to produce VARs in case of system trouble
C) Because long term transmission lines cause static capacitive effect which may over balance the inductive effect of the load during that time
When a synchronous condenser is producing VARs:
A) An increase in DC field current will cause a decrease in Reactive power
B) A decrease in DC field current will cause a decrease in Reactive power
C) An increase in DC field current will cause an increase in reactive power
D) An increase in DC field current will cause no change in reactive power
C) An increase in DC field current will cause an increase in reactive power
Which one of the following statements concerning capacitors is not correct?
A) Capacitors increase the amount of current being carried in a circuit
B) They perform the same function in producing VARs as synchronous condensors
C) Capacitors are generally used where the KVAR requirements are relatively small
D) Capacitors can only produce VARs - never consumes VARs
A) Capacitors increase the amount of current being carried in a circuit
In a system using capacitors for power factor correction:
A) They are installed in parallel
B) They are installed is sufficent number to supply desired amount of reactive power
C) It is not economically practical to correct the power factor to unity
D) All three
D) All three
Capacitors are:
A) Never install in parallel
B) Always install in parallel
C) Never install in series
D) Sometimes installed in series with the distribution circuit
D) Sometimes installed in series with the distribution circuit
From the power triangle diagram below, what would be the power factor of the circuit if a 40 kva capacitor were installed
A) 50%
B) 75%
C) 80%
D) 97%
D) 97%
overall power factor = OM/OP
pf=80/82
pf=97%
page 6
