IEC 60228 Cable

Every power cable depends on its conductor, and IEC 60228 is the international standard that defines how that conductor must be made and how it must perform. Published by the International Electrotechnical Commission and adopted worldwide—often written as BS EN 60228 or VDE 0295—the current version, IEC 60228:2023, applies to nominal cross‑sections from 0.5 mm² to 3 500 mm², for both copper and aluminium conductors in insulated cables.

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The strength of this standard lies in its focus. It deals strictly with the bare conductor, leaving insulation and sheathing to other specifications, which lets it go deep into the electrical details that matter. For each material and cross‑section, IEC 60228 sets a maximum DC resistance at 20 °C — a single, measurable value that becomes the universal benchmark for production testing and quality control. Once that resistance is met, the conductor can be trusted within the thermal and electrical limits of the overall cable design.

IEC 60228 groups conductors into four classes: Class 1 for solid conductors, Class 2 for stranded conductors in fixed power cables, and Classes 5 and 6 for flexible copper conductors suited to movement and tight bending. Aluminium is standardised only in Class 1 and Class 2, while the flexible classes remain exclusively copper. The standard also defines minimum constructional requirements — number of wires, maximum wire diameter, and permitted shapes — so that a “Class 2 stranded copper conductor” delivers consistent performance regardless of the manufacturer, removing uncertainty from specification and procurement.

IEC 60228 Conductor Classes

IEC 60228 Copper Conductor Construction – Core Parameters (Class 2, 5 & 6)

IEC 60228 Standard Conductor Sizes — Metric and AWG Cross-Reference

Class	Construction	Material	Characteristics	Main Applications
Class 1	Solid single wire	Copper or aluminium	Rigid, simple structure, smallest bending radius not suitable for movement	Smallsize fixed wiring, building wires, panel connections
Class 2	Stranded (circular, compacted or sectorshaped)	Copper or aluminium	Semirigid, good conductivity, standard for stationary installation	All stationary power cables — LV, MV, HV, armoured or unarmoured
Class 5	Flexible — multiple fine copper wires	Copper only	Soft, bendable, designed for movement but not extreme flexing	Equipment wiring, control cables, connections subject to vibration
Class 6	Extra flexible — even finer copper wires	Copper only	Very soft, withstands repeated bending and tight routing	Drag chains, cable tracks, portable tools, frequent rerouting

Nominal CrossSection (mm²)	Class 2 Stranded * (Min. Strands × Max. Wire Ø)	Class 5 Max. Wire Ø (mm)	Class 6 Max. Wire Ø (mm)	Max. DC Resistance at 20°C (Ω/km) Bare Cu
0.5	7 × 0.21	0.21	0.16	36.0
0.75	7 × 0.24	0.21	0.16	24.5
1.0	7 × 0.26	0.21	0.16	18.1
1.5	7 × 0.32	0.26	0.16	12.1
2.5	7 × 0.41	0.26	0.16	7.41
4	7 × 0.51	0.31	0.16	4.61
6	7 × 0.63	0.31	0.21	3.08
10	7 × 0.80	0.41	0.21	1.83
16	7 × 1.03	0.41	0.21	1.15
25	7 × 1.29	0.41	0.21	0.727
35	7 × 1.53	0.41	0.21	0.524
50	19 × 1.10	0.41	0.31	0.387
70	19 × 1.29	0.51	0.31	0.268
95	19 × 1.51	0.51	0.31	0.193
120	37 × 1.20	0.51	0.31	0.153
150	37 × 1.34	0.51	0.31	0.124
185	37 × 1.49	0.51	0.31	0.0991
240	37 × 1.70	0.51	0.31	0.0754
300	61 × 1.48	0.51	0.31	0.0601
400	61 × 1.71	0.51	0.31	0.0470
500	61 × 1.92	0.61	0.31	0.0366
630	91 × 1.73	0.61	0.41	0.0283

IEC 60228 Nominal Size (mm²)	AWG / KCMIL Equivalent	Actual CrossSection (mm²)	Construction Standard
0.5	22 AWG	0.324	IEC 60228 Class 1, 2, 5, 6
0.5	20 AWG	0.519	IEC 60228 Class 1, 2, 5, 6
0.75	20 AWG	0.519	IEC 60228 Class 1, 2, 5, 6
1.0	18 AWG	0.823	IEC 60228 Class 1, 2, 5, 6
1.5	16 AWG	1.31	IEC 60228 Class 1, 2, 5, 6
2.5	14 AWG	2.08	IEC 60228 Class 1, 2, 5, 6
4.0	12 AWG	3.31	IEC 60228 Class 1, 2, 5, 6
6.0	10 AWG	5.26	IEC 60228 Class 1, 2, 5, 6
10.0	8 AWG	8.37	IEC 60228 Class 1, 2, 5, 6
16.0	6 AWG	13.3	IEC 60228 Class 1, 2, 5, 6
25.0	4 AWG	21.2	IEC 60228 Class 1, 2, 5, 6
35.0	2 AWG	33.6	IEC 60228 Class 1, 2, 5, 6
50.0	1 AWG	42.4	IEC 60228 Class 1, 2
50.0	1/0 AWG	53.5	IEC 60228 Class 5, 6
70.0	2/0 AWG	67.4	IEC 60228 Class 1, 2, 5, 6
95.0	3/0 AWG	85.0	IEC 60228 Class 1, 2, 5, 6
120.0	4/0 AWG	107.2	IEC 60228 Class 1, 2, 5, 6
150.0	250 KCMIL	126.7	IEC 60228 Class 1, 2
150.0	300 KCMIL	152.0	IEC 60228 Class 5, 6
185.0	350 KCMIL	177.3	IEC 60228 Class 1, 2, 5, 6
240.0	400–500 KCMIL	202.7–253.4	IEC 60228 Class 1, 2, 5, 6
300.0	550–600 KCMIL	278.7–304.0	IEC 60228 Class 1, 2, 5, 6
400.0	700–800 KCMIL	354.7–405.4	IEC 60228 Class 1, 2, 5, 6
500.0	900–1000 KCMIL	456.0–506.7	IEC 60228 Class 1, 2, 5, 6
630.0	1000–1250 KCMIL	506.7–633.4	IEC 60228 Class 1, 2, 5, 6
800.0	1500 KCMIL	760.0	IEC 60228 Class 2
1000.0	1750–2000 KCMIL	886.7–1013.4	IEC 60228 Class 2

Typical Applications of IEC 60228 Cable

Utility Power Distribution
Stable conductors for urban grid networks.
Industrial Manufacturing
Reliable power for heavy-duty machinery.
Underground Cable Systems
Durable cables for buried installations.
Renewable Energy Projects
Efficient transmission for solar and wind.
Commercial Building Wiring
Safe internal distribution for large buildings.
Mining and Harsh Environments
Rugged cables for demanding site conditions.
Railway and Infrastructure
Reliable power for rail and transit systems.
Automation and Moving Equipment
Flexible conductors for dynamic motion use.

Applying IEC 60228 in Cable Selection – Key Benefits

Universal Fit: Standardized cross-sections ensure 100% compatibility with global connectors and lugs.
Performance Guarantee: Mandates Maximum DC Resistance, ensuring accurate voltage drop and heat calculations.
Flexibility Mapping: Classes 1–6 provide a clear technical path to match cable movement needs (fixed vs. dynamic).
Material Integrity: Guarantees high-purity copper/aluminum, preventing the use of inferior, high-resistance metals.
Risk Reduction: Prevents overheating and fire hazards through strict resistance limits.
Global Compliance: Simplifies international project approvals and insurance compliance.
Energy Efficiency: Minimized resistance reduces power loss and long-term operational costs.
Easy Verification: Provides a clear, measurable standard for Factory Acceptance Testing (FAT).

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Frequently Asked Questions

What size wire should be used for an IEC 60228 grounding system?

Wire size for a grounding system is determined by the fault current requirements of the specific installation, not directly by IEC 60228. The standard only ensures that the conductor (often bare copper Class 2) meets strict dimensional and resistance performance criteria. For example, a 120 mm² bare copper conductor must not exceed a maximum DC resistance of 0.153 Ohm/km. You should select the conductor cross-sectional area based on your electrical design needs, and then specify an IEC 60228-compliant conductor of that size.

What’s new in IEC 60228:2023?

IEC 60228:2023 updates conductor classifications, technical definitions, and verification requirements for insulated cable conductors. One important change is the formal removal of the old Class 3 conductor category. The revision also improves consistency for conductor resistance requirements, strand construction references, and testing methods, helping manufacturers and engineers align with current international cable design practices.

What is the difference between IEC 60228 and IEC 60502?

IEC 60228 focuses on the conductors used inside insulated cables, including conductor classes, strand construction, cross-sectional areas, and maximum DC resistance values. IEC 60502, however, covers the complete power cable structure, including insulation, sheath materials, voltage ratings, and testing requirements. In many power cables, IEC 60228 defines the conductor while IEC 60502 defines the cable itself.

What is the maximum DC resistance in IEC 60228?

IEC 60228 standard establishes a direct relationship between a conductor’s maximum DC resistance and its nominal cross-section, material, and construction class. In essence, there is no single maximum resistance value; a larger conductor has lower resistance, and flexible constructions (Class 5/6) made of fine wires have slightly higher resistance than solid or stranded conductors (Class 1/2) of the same size. For instance, the standard requires a 16 mm² Class 2 copper conductor to not exceed 1.15 Ω/km at 20°C, while the maximum for a much larger 630 mm² Class 2 copper conductor is just 0.0283 Ω/km.