Blueprint Reading & Interpretation Flashcards

On a transformer nameplate shown in a substation diagram, 'OA/FA' rating indicates:

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.

In electrical blueprint reading, 'conduit home runs' are indicated by:

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.

What does 'NTS' written on a blueprint dimension or view mean?

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.

On a relay protection diagram for a transmission line, the designation '21' refers to which type of relay?

Answer: Distance (impedance) relay

Device number 21 per ANSI/IEEE C37.2 designates a distance or impedance relay, commonly used for transmission line protection.

On a structural steel blueprint for a transmission tower, 'W8x31' refers to:

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.

Which line type on a mechanical/electrical blueprint indicates a hidden or concealed feature?

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.

In AEP substation drawings, bus configurations labeled '6/4' typically refers to:

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.