Reference · 8 min read · Updated May 2026

Single-Line Diagram Symbols (IEC + ANSI Cheat Sheet)

Two standards dominate electrical schematic symbols: IEC 60617 (international, used in Europe, China, Australia, Middle East, and most of Asia) and ANSI/IEEE 315 (used in North America). They overlap on many components but differ on others — transformers, motors, and protective devices have visibly different shapes.

This page is a quick visual reference of the most common single-line diagram symbols across both standards. Use it when you need to read a foreign drawing or decide which standard to use for a new project. For full details, refer to the IEC 60617 database or ANSI/IEEE 315-1975 (R1993).

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Sources and supply

IEC	ANSI/IEEE	Name	Notes
		Utility source / grid	Label with voltage and short-circuit MVA if known. Both standards use a plain circle.
		Generator	Circle with "G". Asynchronous generators sometimes use "GS".
		Battery / BESS	IEC uses a box with cell pairs inside; ANSI uses stacked long/short bars. Label kWh capacity.
		PV array	Both standards: a rectangle with diagonal lines indicating "radiation". Label kWp rating.

Switching and protection

IEC	ANSI/IEEE	Name	Notes
		Disconnect / isolator	A break in the line drawn as a switch arm. Label QS (IEC) or DS (ANSI).
		Circuit breaker	IEC: switch with two crossbars indicating make/break. ANSI: a rectangle in the line. Label QF (IEC) or CB (ANSI) + amperage + AIC.
		Fuse	IEC: rectangle in the line. ANSI: zigzag. Label F or FU + ampere rating + class (e.g. CC, J, RK1).
		Ground	IEC uses a filled triangle or a circle; ANSI uses the familiar three-line "earth" symbol.
		Surge protective device (SPD)	Two arrowheads pointing into the line. Both standards similar. Label SPD + class (Type 1, 2, 3) + kA.

Transformers

IEC	ANSI/IEEE	Name	Notes
		Two-winding transformer	IEC: two interlocking circles. ANSI: two coils side by side. Label T + kVA + impedance %.
		Three-winding transformer	Three coupled windings. Used for HV/MV/LV substation transformers. Label primary/secondary/tertiary voltages.
		Y-Δ transformer	Wye (Y) primary, delta (Δ) secondary. Most common config for HV → MV step-down.
		Current transformer (CT)	Single circle on the conductor. Label CT + ratio (e.g. 600:5).

Loads

IEC	ANSI/IEEE	Name	Notes
		Motor	Circle with "M". Asynchronous motors sometimes use "M~". Label HP/kW.
		Load / panel	Triangle pointing down, or a labeled box. IEC convention: triangle with explicit name.
		Capacitor (PFC)	Two parallel plates. Power factor correction caps are usually drawn shunt-connected.

Bus and connection

Symbol	Name	Notes
	Bus bar	A thick horizontal line with feeders branching off. Label voltage and amperage.
	Junction (connection)	A filled dot at the intersection indicates wires are connected. No dot = crossing without contact.

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IEC vs ANSI: how to choose

If you're working in North America, use ANSI. If you're working in Europe, Asia, Australia, or the Middle East, use IEC. Don't mix the two in the same drawing — reviewers will reject it as confusing.

If you have to read a drawing from a foreign engineer, the largest differences are:

Transformer symbols — IEC's interlocking circles vs ANSI's coil pairs
Fuse symbols — IEC rectangle vs ANSI zigzag
Ground — IEC triangle/circle vs ANSI three-line earth
Device prefixes — IEC uses Q (switching), F (fuse), T (transformer), M (motor); ANSI uses CB, FU, T, M plus numeric device numbers per IEEE C37.2 (e.g. 50/51 = overcurrent relay)

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