Miscellaneous Flashcards
What is the equation to find Voltage?
E = I x R
What are the polarity bushing markings of a transformer?
H1 - X1
Describe Impedance
Opposition to current flow in an AC Circuit
What best describes transfer of energy in a transformer?
Mutual Inductance
What is the difference between a no-load and a load-tap changer?
Requires the transformer to be de-energized
What is the difference between AC and DC?
DC has a fixed polarity and AC does not
If the high voltage rating of a transformer nameplate read 12000 / 20780 WYE, what voltage would the transformer need across H1 - H2?
12,000
What is the rule of thumb for a 240V single phase transformer?
4A per kVA
Describe how a transformer works
Voltage is induced when a magnetic field moves across a secondary winding
What does a vector represent?
Magnitude and angle
What are the SCE Bulk Transmission voltages?
500kV and 220kV
What is measured in Ohms?
Impedance, Resistance and Reactance
What best describes the difference between AC and DC electricity
AC polarity alternates, while DC polarity does not
What do AC Generators consist of?
- Loop of wire
- Stationary Magnetic Field
- Prime Mover
- Permanent Magnet
What is the displacement between 3 phases of electricity?
120 Degrees
How many interconnected power systems cover parts of both the US and Canada?
4
Which part of the electric system is also referred to as “The Bulk Power System?”
Transmission
Which Substation operates at Distribution-level voltages?
“B” Bank
What is an example of a “B” Bank Substation?
66kV / 12kV
Typically, dry-cooled transformers will not be used above _____ kVA.
50kVA
What type of cooling do SCE Distribution Transformers use?
oil or liquid immersed
What function to potential transformers provide the Edison system?
Provide a proportionate value of voltage for metering
What voltage would you get phase-to-phase when you wire three windings in WYE configuration?
The single winding times 1.73
A 75kVA three-phase, wye-connected transformer has phase-to-neutral voltage of 120V. What is the line voltage?
240V
How do you know if a transformer is additive or subtractive?
Read the Transformer Nameplate
What is harmonic in an electrical system?
A multiple of the fundamental frequency of 60 Hz
What is an advantage of delta transformer connections?
They trap third harmonics
Vectors are useful in expressing electrical systems because they indicate both _____ and ____ of a force or quality
Magnitude and Angle
What is the standard SCE phase sequence?
BAC, CBA
How would current flow in the primary coil and secondary coil of a single phase transformer?
In H1 and out X1
What are guy strain insulators used for?
To break and insulate a guy wire from the ground.
What size guy wire does transmission use for span guys?
9/32”
When would you use an anchor rod extension?
When raised grade changes are expected.
What best describes the function and proper use of guy strain rods?
On tangent poles in wind-prone areas
What is the preferred type of anchor to use in T & D construction?
Power-Installed Screw Anchor
When would you use a plate anchor?
In extremely loose soil, inaccessible areas, and in rock or hard soil where a granite anchor cannot be satisfactorily installed.
The hole for a plate anchor can be dug using___
A Shovel or other handtools or a backhoe
What are overhead splices used at SCE?
- Compression Line Splices
- Jumper Loop Splices
How far apart must line splices be in the same span?
At least 100’
Tools and materials used for overhead Transmission conductor splices include:
Hydraulic pump, press head, and hoses and compression dies
What are the key steps of installing a repair splice?
Center the repair sleeve on the center of the damaged section of the conductor. Mark the center of the sleeve and tape the conductor strands together securely at each end of the sleeve. Make the outer layer of strands as tight as possible.
Under arm PVC is used to
Protect wires
Which of the following transformers are used in the SCE electrical system?
Current; Potential
