What to Send with an Enquiry So a Rating Can Be Calculated

Why there is no ampacity table here

A cable's continuous current rating follows from the 90 °C conductor limit and the rate at which heat escapes into whatever surrounds the cable. Change the surroundings and the same conductor carries a different current.

Because of this, the rating is calculated for each installation rather than read from a generic table. A table quoted without its conditions — in air or in ground, what ambient temperature, what soil thermal resistivity, how many cables grouped — invites misuse, and the error surfaces only after energisation, when it is expensive to fix. For that reason this site publishes the thermal limits and the method rather than a table of numbers.

The six inputs

An enquiry that carries the following can be answered with a calculated rating instead of a placeholder:

1. System voltage and cable rating required — for example 0.6/1 kV, or 12/20 kV for a medium-voltage feeder. This determines which part of IEC 60502 governs the construction.
2. Conductor size and material, and whether a specific conductor class to IEC 60228 is required.
3. Installation method — in air, directly buried, in duct, on tray, or a mix along the route. Each has a different thermal path.
4. Ambient conditions — air or soil temperature, and soil thermal resistivity where the cable is buried.
5. Grouping — how many loaded cables run together and at what spacing. Derating for grouping is frequently the largest single correction applied.
6. The governing standard — IEC 60502, or a national standard such as BS, DIN or ICEA where the project requires one.

Missing items are not blockers, but each one that is absent has to be assumed, and an assumption made at quotation stage has a way of becoming a commitment later.

Fire performance is a separate line

Electrical sizing and fire performance are independent decisions, and conflating them is a common source of rework. Specify separately:

• Flame retardance — the ZR- constructions, tested to the IEC 60332 series (GB/T 18380.3 in the Chinese system)
• Halogen-free and low smoke — the LSOH constructions, with acid gas measured to IEC 60754 and smoke density to IEC 61034
• Circuit integrity under fire — the mica-taped fire-resistant constructions

These are distinct requirements met by different constructions. Naming the hazard the project is managing — evacuation time, equipment corrosion, or circuit survival — is more useful than naming a material, because it allows the right construction to be proposed where more than one would satisfy the wording.

Mechanical and environmental duties

Two further conditions determine the construction rather than the size. If the cable will be exposed to external mechanical force in service, an armoured construction is required — the standard unarmoured YJV build is designed to bear traction during installation but not mechanical force afterwards. If the route is wet or submerged, water-blocking should be specified.

Installation conditions also belong in the enquiry where they are unusual: a route with tight bends needs checking against the minimum bending radius of 20 × overall diameter for single-core and 15 × for multi-core, and a cold-climate installation needs to respect the 0 °C minimum installation temperature. Both are straightforward to accommodate when known in advance.