Drawing conventions
The design draws its sheets on one layout of paper: a frame with zone references, a drawing area on the left, and a column for the notes and the title block on the right. The single-line diagram (SLD), the electrical key diagram, the yard plan and sections, the earth mat layout and its typical details, the lightning protection plan and the auxiliary supply SLD follow it. The screen, the Portable Document Format (PDF) file and the Drawing Exchange Format (DXF) file are drawn from one model of the sheet, so the three agree.
1Paper
The paper is a property of the standards set. The IEC + CEA / CBIP set draws on A1 landscape, 841 mm × 594 mm. The ANSI / IEEE set draws on ANSI D, 34 in × 22 in (863.6 mm × 558.8 mm), the D size of ASME Y14.1. The title block's SIZE box prints the paper's name.
The notes column keeps its width at the right edge on both papers. On ANSI D the drawing area is 22.6 mm wider and 35.2 mm shorter than on A1. A not-to-scale sheet, such as the SLD, is drawn in the coordinates of the A1 sheet and moved down by the difference in height, so its top stays under the frame.
2Frame and zones
The outer frame is drawn 10 mm inside the edge of the paper, and the inner frame a further 5 mm inside it (Figure 1). The strip between the two frames carries the zone references. The numbers 1 to 8 run left to right along the top and the bottom, and the letters A to F run top to bottom down both sides. A zone reference, a letter and a number, locates an item on the sheet in a comment or a revision note.
A vertical line through the inner frame separates the drawing area from the notes column. The column is 194 mm wide on both papers.
3Views and their scales
A plan or a section is a view: a window on a model drawn at its true size, shown on the sheet at one scale. Above each view is a title band of 12 mm. It holds the view's title with its scale in brackets, for example LAYOUT PLAN (SCALE 1:500), a graphic scale bar at its right end and, on a plan, a north arrow at its left end. North is at the top of a plan.
The scale bar has 4 alternate bars, labelled at its ends and its middle. It reads in metres on A1, in feet on ANSI D, and in inches on a detail drawn at 1 in = 1 ft or larger. The bar stays true when the sheet is printed at another size, where the stated scale does not.
A view takes the largest scale of its list at which it fits its window. The yard sheet places the layout plan and its two sections in one of three arrangements: the sections side by side under the plan, one above the other under the plan, or stacked to the right of the plan. It tries the plan's scales from the largest down and, for each, the sections' scales from the largest down. The lightning protection sheet arranges its plan and sections the same way.
| View | IEC + CEA / CBIP set, A1 | ANSI / IEEE set, ANSI D |
|---|---|---|
| Yard plan and lightning protection plan | 1:500, 1:1000, 1:2000 and 1:2500 | 1″ = 40′-0″, 1″ = 50′-0″, 1″ = 60′-0″, 1″ = 100′-0″ and 1″ = 200′-0″ |
| Yard sections | 1:200, 1:250 and 1:500 | 1″ = 10′-0″, 1″ = 20′-0″, 1″ = 30′-0″ and 1″ = 40′-0″ |
| Earth mat plan | 1:250, 1:500, 1:1000 and 1:2000 | 1″ = 20′-0″, 1″ = 40′-0″, 1″ = 50′-0″, 1″ = 100′-0″ and 1″ = 200′-0″ |
| Lightning protection sections | 1:200, 1:250, 1:500, 1:1000 and 1:2000 | 1″ = 10′-0″, 1″ = 20′-0″, 1″ = 40′-0″, 1″ = 100′-0″ and 1″ = 200′-0″ |
| Typical details of the earth mat | 1:5, 1:10 and 1:10 | 3″ = 1′-0″, 1-1/2″ = 1′-0″ and 1″ = 1′-0″ |
The ANSI / IEEE set uses an engineer's scales for its plans and sections and architectural scales for the details. The SLD, the key diagram and the auxiliary supply SLD are not drawn to a scale, and their title blocks print NTS (not to scale). A sheet with a plan and sections prints both scales in its title block, the plan's first.
Given a new 220 kV project with the default inputs, drawn on A1.
| Sheet | View | Scale |
|---|---|---|
| Switchyard plan and sections | Layout plan | 1:500 |
| Switchyard plan and sections | Sections A-A and B-B | 1:250 |
| Earth mat layout | Plan | 1:500 |
| Lightning protection | Plan | 1:500 |
| Lightning protection | Sections X-X and Y-Y | 1:500 |
| Earth mat typical details | Details A, B and C | 1:5, 1:10 and 1:10 |
| Single-line diagram, key diagram, auxiliary supply SLD | Diagram | NTS |
Result The yard plan fits at 1:500, the largest scale of its list, and its sections at 1:250. The earth mat plan takes 1:500, and the lightning protection plan and sections take 1:500.
4Notes column
The notes column holds titled blocks of notes from its top down. A block's heading is in capitals, for example NOTES, YARD SUMMARY, CLEARANCE CHECKS, EQUIPMENT RATINGS, QUANTITIES or LEGEND. Its notes are sentences in sentence case, and the NOTES block numbers them. Each note is wrapped to the column's width, and a line never breaks between a number and its unit.
The SLD draws its legend under the notes, in two columns of symbol and meaning (Graphical symbols). A sheet edited in Sketch mode prints EDITED AFTER GENERATION with the number of changes above the title block. The calculations follow the inputs and the design rules, not the edits, and the reports name the edited drawings.
Labels on a drawing print in capitals, with their unit symbols as written: 220 kV SWITCHYARD, with kV in its own case.
5Title block
The title block fills the foot of the notes column, 189 mm wide and 101.5 mm high. From the bottom up it has these rows:
- SCALE, SIZE and the sheet number, Sheet 1 of 1
- the drawing number (DRG. NO.) and the revision (REV.)
- the names of the persons who draw, check and approve the drawing, each with the date of the revision, under a NAME and DATE row
- the title on two lines: the sheet's title, and a line that names the substation, for example 220/33 kV POOLING SUBSTATION, 250 MW
- LOCATION, CLIENT and PROJECT, with (not given) where an input is empty
- the revision table, 3 rows under a REV, DATE, DESCRIPTION and BY header
- a header with the company's name, or the project's name when no company is entered
A value too long for its box is printed smaller, then cut with an ellipsis. The drawing number, the revision and the revision table follow the project's document control (Document control).
6Text heights
Text heights are cap heights on paper. Sheet text is real text in one font, so it can be selected and searched in the PDF.
| Text | Height on paper |
|---|---|
| Notes and zone references | 2.5 mm, at a line pitch of 4.0 mm |
| Note block headings | 3.5 mm |
| View titles | 3.0 mm |
| Title block captions (SCALE, DRG. NO., REV.) | 2.0 mm |
| Drawing number, revision and header of the title block | 3.5 mm |
| Sheet title in the title block | 3.0 mm |
| Text in a plan or a section, at least | 2.5 mm |
| Device tags on the not-to-scale diagrams, at least | 2.0 mm |
A label in a plan or a section is drawn in the model at its paper height times the view's scale, so it prints at 2.5 mm or more at any scale. The labels are placed clear of each other and of the conductors.
7Layers and line types
Each line and text of a sheet is on a named layer with its colour, line type and lineweight. The layers can be hidden on the sheet's screen, and they arrive in the DXF file with the same names.
| Layer | What it holds | Line type | Lineweight |
|---|---|---|---|
| FRAME | The frames and the column line | continuous | 0.50 mm |
| TITLE | Lines of the title block, the view titles and the scale bars | continuous | 0.25 mm |
| BUS | HV buses on the SLD (the MV buses have a layer of their own) | continuous | 0.70 mm |
| EQUIP | Equipment and conductors | continuous | 0.35 mm |
| TEXT | Labels and notes | continuous | 0.18 mm |
| DIM | Dimensions | continuous | 0.18 mm |
| FUTURE | Future bays | dashed | 0.25 mm |
| METER | Meters and their connections | dashed | 0.18 mm |
| FENCE | The fence | dashdot | 0.35 mm |
| EARTHMAT | Earth mat conductors | continuous | 0.35 mm |
| ROD | Earth electrodes | continuous | 0.35 mm |
| SHIELD | Shield wires | dashed | 0.35 mm |
| SKETCH | Objects added in Sketch mode | continuous | 0.35 mm |
A future bay is dashed on the SLD and in the yard, so it reads as space kept for a circuit to come (Bays and their equipment). Other layers hold the roads, the building, the structures, the oil containment, the ground line of a section and the parts beyond a section's cut plane.
8DXF and PDF files
The DXF file of a sheet is an AutoCAD R2010 file. Its model space holds the views' models at full size: in millimetres on A1, in inches on ANSI D. A paper-space layout at the paper's size holds the frame, the notes and the title block, with one viewport per view at that view's scale. Dashed lines follow the scale of their viewport. Text uses the OpenSans text style.
The PDF file is the sheet at its true size, with its text as real text and its font embedded. A calculation report or a schedule is an A4 PDF, 210 mm × 297 mm with margins of 18 mm. Its pages carry a running header and Page n of m.