Vol: 1 Substation & Overhead Flashcards
What is the preferred distribution voltage in the Air Force?
7,200/12,470 volts.
List three functions a substation can perform.
Voltage change, voltage regulation, switching, metering, converting, frequency changing, and so forth
Name six major substation components.
Power transformers, circuit breakers, meters, relays, lightning arresters, and batteries.
Which color indicates that a circuit is energized?
Red.
What two main requirements must a switch in a high-voltage electrical circuit meet?
Must carry its rated current safely without overheating and must have proper clearances and insulation for
its rated voltage.
At least how many lightning arresters must be installed in a substation with one incoming circuit
and one outgoing circuit?
Six
Which type of regulator has the primary or exciting winding connected in shunt and the
secondary or regulating winding connected in series?
An induction-voltage regulator.
Which type of regulator uses taps to regulate the amount of induced voltage?
A step-voltage regulator
Which type of instrument transformer requires the secondary side to be closed at all times when
the primary side is energized?
A current transformer.
What suppresses the arc in an OCB?
Oil.
Name the three main functions of an OCB.
To protect the system by opening the circuit automatically in case of a ground fault or other overcurrent
situation; to restore power automatically for temporary faults; and to provide a means of switching under
load.
Explain the difference between an indoor and outdoor OCB.
Indoor OCBs are made in a cubicle-type construction; outdoor OCB type is normally dome constructed.
SF6 and similar switches have skirted insulator construction.
How many different ways can an OCB operate?
3
State the purpose of the OCB timer port.
During maintenance the timer port is where we place a timing device that is used to see if the OCB opens in
the correct amount of time.
Name the three basic functions of a recloser.
Automatic testing of the line and restoration of service if the fault has cleared, selecting the device to isolate
permanent faults in a coordinated protective system, and interrupting fault currents in minimum time to
protect against conductor burn down and equipment damage
How does a fault make the recloser trip open?
The recloser’s solenoid is set to trip at a certain current. When the fault current reaches that limit, the
increased magnetic field moves the solenoid plunger down through the coil, tripping the contact assembly
to open the contacts and break the circuit
When does the sectionalizer operate?
During the time the recloser has opened the line
Name the main components of a sectionalizer.
A set of contacts, a spring-controlled trip, and a solenoid-operating coil
What piece of equipment must we use to back up a sectionalizer?
A recloser.
How is an air-break switch normally operated?
Manually or automatically.
What equipment does the air-break switch use to break the arc?
Arcing horns.
Where are air-break switches normally mounted?
On substation structures or on poles.
What allows the switches of an air-break switch to open and close at the same time?
A gang-operated switch
How is the arc broken by a vacuum recloser?
The high-voltage contacts are enclosed in a vacuum and, as the contacts separate, the lack of oxygen
extinguishes the arc rapidly.
Which switches operate much like a vacuum switch?
SF6 switches.
Before installing a high-voltage switch, what data plate information must you check?
The voltage rating and current interrupting rating.
How do you position the vehicle before final placement of the high-voltage switch?
So the operator can observe the switch placement.
What is the first connection you make in connecting the high-voltage switch into the circuit?
The ground connection
Why must you never let an OCB trip while the oil tank is lowered?
Without the oil to absorb the shock, equipment damage and personal injury are likely.
What do you look for when you inspect an OCB’s contacts?
Check alignment and firm uniform pressure.
When moisture is in oil-filled equipment, what problem occurs?
Moisture decreases an oil’s insulating strength
What must you ensure before you “top off” oil-filled equipment?
That the liquid being added to the equipment is compatible with the liquid already in it.
Which items do you check visually in inspecting bushings?
Excessive contamination, cracked or broken porcelain, low oil level (oil-filled bushings), broken or
deteriorated seals, fractured metal parts, excessive operating temperature, loose or missing parts, and so
forth.
On what does scheduling maintenance on reclosers depend primarily?
On the severity and number of reclosings incurred and the dielectric strength of the insulating oil
How do you inspect the contacts on vacuum breakers?
Each interrupter has an external indicator called a “wear gap” that provides a way to gauge the amount of
contact erosion.
How can you test vacuum breakers to see if the vacuum is adequate to interrupt current?
We can give vacuum breakers a high-potential test
What piece of equipment can aid your visual inspections of air switches?
Binoculars.
State what you accomplish by repeatedly opening and closing an air-break switch.
You clean the contacts
Field experience indicates that switch interrupters with gas-filled chambers normally need
recharging how often?
Every 2 1/2 to 3 years
How often do you check storage batteries
Monthly
Once you check the storage battery, what do you record?
Record voltage, specific gravity, level of electrolyte, charging rate, internal and nearby temperature,
ventilation, and cleanliness
What is the gravity reading of a fully charged battery cell in stationary standby service?
1200
Explain what you can and can not use as additives to storage batteries.
The only additive is approved distilled water. Items that should not be added are acid, electrolyte, or any
special powder, solutions, or jellies.
What instrument do we most commonly use to test a battery cell charge?
Hydrometer
What contacts can we best clean with a fine burnishing tool or crocus cloth?
Silver.
How often do you check relay settings?
Once a year.
In checking contact resistance of relays, what may be indicated by a high resistance?
Insufficient spring pressure.
What test voltage do you use in dielectric testing of relays that are rated under 6,000 volts?
Twice the rated voltage plus 1,000 volts with a minimum of 1,500 volts AC for 1 minute.
What is the best way to make an operational test of a relay?
With a test current
On what effect do thermostats, thermal overload, and temperature devices operate?
Heating effect of electric current
As a general rule, how often do you inspect mechanically operated substation devices?
Every 6 months
For general maintenance, what type of meter do you use?
A multimeter.
What are you looking for during visual inspection of a voltage regulator?
Leaks, cracked bushings, loose connections, corrosion, and similar problems may be noticed before serious
problems could develop that could affect the continuity of service
When you’re removing a voltage regulator from service for maintenance, what’s your first step in
isolating it?
Place the regulator in the neutral or zero position
What’s the maximum time between dielectric oil tests on voltage regulators?
5 years.
What do you do if two successive monthly cell readings show a particular cell low in either
voltage or specific gravity?
Check to see that this cell gasses properly on charge. If it doesn’t, do not act unless the reading decreases
further the next month. If the reading goes lower, an insufficient charge, a short circuit, or impure
electrolyte is indicated and the trouble should be corrected promptly.
If impurities dissolved in a battery cell’s electrolyte are causing irregular cell operation, how can
you correct the problem?
Replace the electrolyte immediately after flushing the cell thoroughly with distilled or approved tap water.
What must you do to keep storage batteries clean?
Keep the battery, its connections, and the surroundings clean and dry by wiping with a dry rag. Vent plugs
must be in place with their gas escape holes clean. If you spill electrolyte or if surrounding parts are damp
with acid, apply a solution of bicarbonate of soda or baking soda (1 pound of soda to 1 gallon of warm
water), followed by rinsing with water and drying. Scrape clean corroded terminals or connectors, wash
with a soda solution, and thinly coat with petroleum jelly or nonoxide grease.
After repair work on a relay, what must you do before returning the relay to service?
Make complete performance tests on the relay.
How would you test a transformer for a “short”?
By connecting one megger lead to a high-voltage bushing and the other lead to a low-voltage bushing and
observing the reading. Test between all primary and secondary bushings to be certain. A reading of
continuity indicates a short, and a reading of infinity indicates the transformer is not shorted.
What does a reading of zero indicate when testing a transformer winding for an open?
“Zero” indicates no resistance between two points, therefore the winding is good.
Why must you separate the secondary windings of a transformer when testing for opens?
A false reading could be obtained on parallel-connected secondary windings.
When troubleshooting an oil circuit breaker and you find dirty oil, what could be the cause?
Carbonization from many operations.
List causes and remedies for a circuit breaker that’s tripping prematurely.
Causes include a setting that’s too low, repetitive closing and jogging, under voltage device and control
circuit and auxiliary pilot devices affected by operating circuit, and incorrect rating. Remedies include
resetting or increasing the trip setting, checking the load and current peaks against the setting, and checking
the circuits.
Why must you not wear coveralls with the top half wrapped around your waist?
Wearing coveralls in this manner increases the likelihood of injury from clothing getting caught in
machinery
What test requirements must hard hats meet?
20,000 Volts AC for three minutes.
Can you use rubber glove protectors as work gloves?
No
What are the requirements for long sleeves while working on electric lines greater than 50 V?
Sleeves must be rolled down and buttoned.
How often must you clean body belts and safety straps?
Every three months.
What two types of soap can we use to clean leather goods?
A neutral soap and saddle soap.
How often do you oil body belts and safety straps?
Every 6 months.
In regard to oiling, in what condition must leather straps and belts be before the bending test?
The leather should contain enough oil to be soft and pliable.
List some advantages belts made of webbing have over leather belts.
(a) Webbing withstands impact loads better, (b) webbing requires no special care and treatment as leather
would, (c) webbing can be evaluated more accurately by visual inspection.
State two major reasons for pole climbing accidents.
Improper climbing techniques and improper care and maintenance of climbers
How do you store climbers?
Wrapped in pairs in gaff guards and fastened with their straps.
List several things to look for when inspecting climbers.
Your answer might include: Loose or dull gaff; excessively worn, cracked, or torn straps and pads; enlarged
buckle holes in the straps; excessively worn stirrups; defective strap rings.
Name three ways to tell whether gaffs are sharpened properly.
Gauging, plane test, and pole cutout.
What do you need to hone the gaff of a machine-sharpened climber?
A pocket-size, smooth Carborundum stone.
What is the average life of a pair of climbers?
5 years.
Name two tools you need to field sharpen gaffs that aren’t machine sharpened.
A file and a Carborundum stone.
Why must you avoid rocking motions in sharpening a gaff with a file?
This will round the edges of the gaff.
What things must you inspect before attempting to climb a pole?
Climbers, body belt, safety strap, hardhat, leather gloves and pole itself.
To what does the positioning of gaffs on opposite sides of the pole lead?
Gaffs will point away from center of pole. This leads to cutouts and falls.
What is the approximate difference in step length when going up and down a pole?
When descending a pole, your steps should be approximately twice as long as when ascending a pole.
How does attachment of the ground wire affect climbing?
The climber should not use the side of the pole where the ground wire is attached.
What is the proper placement of the safety strap during climbing?
Fasten both ends of the safety strap to the “D” ring; NOT hanging loose.
Which type of manufactured rubber protective equipment is subject to ozone and corona
deterioration?
Type I, natural or polyisoprene synthetic rubber.
List signs of chemical deterioration of rubber protective equipment.
Corona cutting, ozone or sun checking, texture changes such as swelling, softening, hardening, or becoming
sticky or inelastic.
In which ANSI/ASTM specification would you find the in-service inspection requirements for
rubber insulating gloves?
ANSI/ASTM D120, Rubber Insulating Gloves.
What problem would you most likely encounter with rubber gloves that are a little too big for
your hands?
Loss of dexterity.
Why does the leather gauntlet have to be shorter than the rubber glove?
The gauntlet does not have the insulation value that the rubber glove has.
How do you wear rubber sleeves in conjunction with rubber gloves?
Tuck the sleeves inside the rubber gloves.
How often must you field air-test rubber gloves?
Before they are used each day and more frequently if you suspect damage.
How do you store rubber sleeves?
In a bag or rolled up.
What are the items to look for when inspecting a rubber sleeve?
Pinholes, cuts, scratches, abrasions, aging corona cutting, oil markings, or other chemical injuries.
What do you do if you find a petroleum product on a rubber blanket?
Wipe it off immediately.
How do you locate defects in a blanket?
The blanket must be rolled twice on each side so that the second roll is at a right angle to the first roll.
What is the electrical testing requirement for rubber blankets?
Electrically test them upon receipt from manufacturer and retest them at least once a year.
How do you store rubber blankets?
Flat or rolled in blanket rollups or canisters.
How often must the supervisor inspect rubber protective equipment?
Every 6 months.
For what purpose do you use hot-line tools?
To minimize the number of power interruptions or outages.
What is the minimum manufacturer certification test voltage for hot sticks?
75,000 volts AC per foot for 3 minutes on wooden sticks, and 100,000 volts AC per foot for 5 minutes on
fiberglass and epoxy sticks.
Where do you store hot-line tools?
In bins or on racks.
How often do hot sticks require a moisture test?
Upon receipt, and at least every six months, or when you suspect moisture penetration
How often does the supervisor inspect hot-line tools visually?
At least every 6 months.
You find a hot stick that needs cleaning; list the steps in sequence.
(1) Wipe stick surface clean with a clean rag. (2) Clean stick surface with an approved hot-stick pole
cleaner. (3) Wax hot stick with hot-stick wax.
Why must you not use silicone cloths to protect the glossy finish of fiberglass hot sticks?
Silicone has a migrating characteristic and, over a period of time, may hamper refinishing processes.
How many overall electrical tests are required for each stick?
Five, four 1-foot segments and one overall test.
What are the test contacts for the electrical hot-stick test?
Two spiral springs, 5/8 inch to 1 inch in diameter, or clamps which make contact with the entire
circumference of the stick. Springs must be wound of spring steel, 40 (±5) thousandths inch diameter.
Why do you use a plastic bag to cover the “hot” lead while you’re testing a hot stick electrically?
To eliminate corona.
In testing a hot stick electrically, at what rate do you raise the voltage to 80 kV and how long must
you maintain that voltage?
Raise the voltage at a rate of 10 kV per second and hold it for 1 minute.
How often must you test the aerial lift controls?
Each day before use.
How many people make up an aerial crew?
At least two qualified workers
Cite four aerial lift device travel procedures.
(1) Drivers must be alert to the fact the vehicle has exposed equipment above the elevation of the truck cab.
(2) Backing must be done slowly and under the direction of one person on the ground who has an
unobstructed view of the intended path of the vehicle, and of its driver.
(3) A truck must not be moved with the boom elevated.
(4) In traveling to and from job sites, pin-on buckets must either be removed and stored on the truck or
secured in a horizontal position to avoid obstructing the driver’s vision.
What precaution must an operator take before lowering the truck’s jacks?
The operator must be sure no one is close enough to be injured.
When it’s necessary to get within reach of energized conductors with the bucket, what precautions
must the operator take?
The bucket operator must wear rubber gloves and sleeves.
What precaution does the operator use if the aerial bucket is operated from the ground controls?
Workers operating ground controls must be on the vehicle or insulated from the ground using primary
rubber gloves and other protective equipment.
What tests must we perform on all new, stored, or modified aerial lift devices?
Tested in accordance with manufacturer’s specifications and special requirements and do a pretest
inspection and acceptance test.
What test do you make on “in-use” aerial lift devices?
They get a daily pretest inspection and a periodic verification test.
If the fiberglass boom is dirty on the preinspection test, what do you do?
Remove dirt with fiberglass cleaner and then wax and buff with a dry cloth for a glossy finish.
What voltage do you use for the periodic verification test?
The voltage the truck will be working near that day.
What is the maximum allowable leakage for the upper insulated boom moisture test?
No more than 100 times that observed in the dry test—never more than 1.0 milliamperes.
State the purpose of the composite upper boom test.
To assure the collective insulation strength of the combined upper booms, air and hydraulic lines, and
leveling mechanism together
How do you test an aerial lift basket without a liner?
Place the basket in the test tank, fill the tank and basket with water to within 6 inches of the top, and place
the tester circuit ground on the test tank and a jumper to the truck frame. Put the source electrode in the
water inside basket and apply 100 kV DC for 1 minute. Maximum allowable leakage must not exceed 100
μA.
Who is responsible for testing the aerial lift device dielectrically?
Civil Engineering or other people trained to work with high voltage
What size winch cable handles loads of less than 10,000 pounds?
1/2-inch wire rope
What advantages are there in using a fabric winch cable instead of a wire rope cable?
It has no steel strands to cut skin, it’s lighter and more manageable to work with, and is nonconductive.
State the purpose of the boom and winch.
To raise, set, pull, and lower poles; load and unload poles from the pole trailer; and load, unload, raise, or
lower pole line equipment
How many people are needed for boom and winch operations?
At least two people.
How do you position the line truck when the job site is on a crown or slope?
So that you can work on high side.
What can you do if the line truck must be set up on hot asphalt or soft ground?
Place planks under the jack pads.
What piece of equipment do we use to pull a pole?
A pole jack.
