2ND 10

Question 1

Which one of the following items would not cause a low lagging power factor:

a) induction motors
b) transformer exciting current
c) transmission lines
d) shunt reactors

Answer 1

c) transmission lines

Question 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 side of receiving or distributing stations
c) adjacent to the customer’s equipment
d) all of the above

Answer 2

c) adjacent to the customer’s equipment

Question 3

Which of the following changes in system operating conditions would tend to change a lagging power factor from 0.85 to 0.90?

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

Answer 3

d) an increase in the field excitation of a synchronous condenser

Question 4

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

Answer 4

c) will have a stabilizing effect on the system

Question 5

During off-peak periods on a power system it may sometimes be necessary to operate the synchronous condenser underexcited:

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 transmission lines cause a 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

Answer 5

c) because long transmission lines cause a static capacitive effect which may over balance the inductive effect of the load during that time

Question 6

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 an increase 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

Answer 6

c) an increase in DC field current will cause an increase in reactive power

Question 7

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 condensers
c) capacitors are generally used where the KVAR requirements are relatively small
d) capacitors can only produce VARs – never consume VARs

Answer 7

a) capacitors increase the amount of current being carried in a circuit

Question 8

In a system using capacitors for power factor correction:

a) they are installed in parallel
b) they are installed in sufficient number to supply the desired amount of reactive power
c) it is not economically practical to correct the power factor to unity
d) all three

Answer 8

d) all three

Question 9

Capacitors are:

a) never installed in parallel
b) always installed in parallel
c) never installed in series
d) sometimes installed in series with the distribution circuit

Answer 9

d) sometimes installed in series with the distribution circuit

Question 10

From the power triangle diagram shown below, what would be the power factor of the circuit if a 40 KVA capacitor were installed?

a) 50 percent
b) 75 percent
c) 80 percent
d) 97 percent

Answer 10

d) 97 percent