AEP Blueprint Reading & Interpretation 3 — Questions and Answers
Question 1: On a transformer nameplate shown in a substation diagram, 'OA/FA' rating indicates:
- Overload Automatic / Fault Automatic
- Oil-immersed Air-cooled / Forced Air-cooled (Correct answer)
- Operating Amps / Full Amps
- Outdoor Application / Forced Application
Correct answer: Oil-immersed Air-cooled / Forced Air-cooled
OA/FA refers to Oil-immersed Air-cooled (self-cooled) / Forced Air-cooled cooling classes for power transformers per ANSI/IEEE standards.
Question 2: In electrical blueprint reading, 'conduit home runs' are indicated by:
- A line running to the panel with an arrow and circuit number notation (Correct answer)
- A double line showing conduit diameter
- A zigzag symbol near the panel board
- A dashed circle at the panel location
Correct answer: A line running to the panel with an arrow and circuit number notation
Home runs are shown as lines with an arrowhead pointing toward the panel, accompanied by circuit number and panel designation.
Question 3: What does 'NTS' written on a blueprint dimension or view mean?
- Not To Scale (Correct answer)
- Neutral Terminal Switch
- Normal Transfer Station
- Night Time Schedule
Correct answer: Not To Scale
NTS means 'Not To Scale,' indicating that the drawing's proportions do not accurately represent actual dimensions and written dimensions must be used.
Question 4: On a relay protection diagram for a transmission line, the designation '21' refers to which type of relay?
- Overcurrent relay
- Distance (impedance) relay (Correct answer)
- Differential relay
- Frequency relay
Correct answer: Distance (impedance) relay
Device number 21 per ANSI/IEEE C37.2 designates a distance or impedance relay, commonly used for transmission line protection.
Question 5: On a structural steel blueprint for a transmission tower, 'W8x31' refers to:
- A wire gauge specification
- A wide-flange steel section 8 inches deep weighing 31 lbs/ft (Correct answer)
- A weld joint rated at 8,000 lbs with 31% duty cycle
- A wind load factor of 8.31 psf
Correct answer: A wide-flange steel section 8 inches deep weighing 31 lbs/ft
W8x31 is the AISC designation for a wide-flange (W-shape) steel beam that is approximately 8 inches deep and weighs 31 pounds per linear foot.
Question 6: Which line type on a mechanical/electrical blueprint indicates a hidden or concealed feature?
- A solid thick line
- A centerline (alternating long and short dashes)
- A dashed line (short equal dashes) (Correct answer)
- A phantom line (long-short-short pattern)
Correct answer: A dashed line (short equal dashes)
Hidden lines are represented by a series of short equal-length dashes, showing edges or features that exist but are not visible from the current view.
Question 7: In AEP substation drawings, bus configurations labeled '6/4' typically refers to:
- Six feeders with four transformers
- A ring bus with 6 breakers and 4 disconnect switches
- A 6-wire / 4-wire wiring scheme
- A breaker-and-a-half scheme with specific bay counts (Correct answer)
Correct answer: A breaker-and-a-half scheme with specific bay counts
In breaker-and-a-half bus configurations, numerical notation often identifies specific bay or bus section counts within that switching arrangement.
AEP Blueprint Reading & Interpretation 3
On a transformer nameplate shown in a substation diagram, 'OA/FA' rating indicates: