Deck 12: Transformer Maintenance

Question 1

Pole-mounted distribution transformers are usually oil-filled and require a great deal of maintenance.

Answer 1

False

Question 2

A high-voltage tester, generally referred to as a "HiPot," develops a high voltage and measures any current leakage caused by weak or defective ____.

A) insulation
B) windings
C) connections
D) switches

Answer 2

A

Question 3

In many larger installations, ____ are placed on each side of the transformer after it is deenergized to protect workers.

A) insulating materials
B) wooden walkways
C) grounds
D) plastic walkways

Answer 3

C

Question 4

The outside of the transformer should be cleaned with an approved solvent or cleaner so that rust and corrosion are removed.

Question 5

When maintaining a large industrial dry-type transformer used in a unit substation, weekly inspections when the transformer is first installed will indicate how often the unit will have to be taken out of service for maintenance.

Question 6

When a worker must enter a transformer tank, if the concentration of oxygen is less than ____%, it could be a health threat to the worker.

A) 10
B) 20
C) 60
D) 75

Question 7

If a pad-mounted oil-cooled transformer is equipped with auxiliary cooling equipment, the temperature and pressure switches and gages should be ____ yearly to ensure proper operation.

A) removed and calibrated
B) replaced
C) cleaned
D) tested

Question 8

A ____-volt megger would be used to test the insulation on a transformer with a 480-volt rated winding.

A) 120
B) 240
C) 500
D) 1,000

Question 9

____ permit power to be supplied from another source in the event of equipment failure.

A) Double-connected transformers
B) Generators
C) Remote substations
D) Double-ended substations

Question 10

When maintaining large control transformers supplying a motor control center, these units should be tested ____ with a megger to determine the condition of the insulation.

A) monthly
B) quarterly
C) semi-annually
D) annually

Question 11

In some of the maintenance procedures, it is necessary to enter a transformer tank. When this is part of the maintenance procedure, the atmosphere in the tank must be tested for the presence of sufficient oxygen, but there is no need to test for the presence of combustible and/or toxic gases.

Question 12

When maintaining large industrial dry-type transformers for use in unit substations, be aware that there might be dangerous voltages present in the cubicle for control circuits or space heaters that might not be deenergized when the transformer is deenergized.

Question 13

It would not be uncommon for a transformer winding rated at 24 volts to measure 34 to 38 volts with no load connected.

Question 14

Transformers are usually thought of as stationary objects with no moving parts. Because of this misconception, they are often neglected and left out of routine preventive maintenance schedules.

Question 15

Excessive current draw or a large deviation from the rated voltage of a winding are good indicators of a shorted winding.

Question 16

Transformers that have a gas blanket on top of the insulating oil have pressure switches that actuate an alarm system if the gas pressure on the blanket drops below a certain point.

Question 17

After an oil sample is drawn for testing, it should be allowed to stand for a while to permit any free ____ to settle to the bottom of the sample.

A) dirt
B) bits of insulation
C) water
D) liquid acetylene

Question 18

When inspecting a large industrial dry-type transformer that is used in a unit substation, a(n) ____ inspection of the transformer, connections, and busses, or wiring under normal load conditions, will indicate any trouble spots.

A) visual
B) infrared
C) infrared thermographic
D) quick

Question 19

Even on larger transformers with high-voltage connections, it is generally not necessary to prepare a written switching procedure detailing each step of the process of deenergizing the equipment.

Question 20

The type of maintenance procedures and intervals between procedures are governed by the ____ of the transformer.

A) manufacturer
B) cooling system
C) type of ventilation
D) type, size, location, and application