How to Specify Overhead Conductors in a Tender or RFQ: The Complete Checklist

Every sound conductor specification begins with three linked pieces of information: the conductor type (AAC, AAAC, ACSR or ACSR-AW), the governing standard, and the exact designation under that standard. Code names such as Dog, Wolf or Hawk are shorthand defined within a particular standard family; the same name quoted without its standard pins down neither the stranding, nor the wire diameters, nor the rated strength.

Write the full triplet: ACSR 120/20 to DIN 48204, ACSR Hawk to ASTM B232, or an all-aluminium-alloy conductor to IEC 61089. Where project practice references EN 50182, BS 215, BS 3242 or DIN 48201, name the edition you intend to enforce. This single line removes more ambiguity than any other clause in the document.

State the values you will actually check at acceptance, and take them from the standard itself rather than retyping them from memory or an old file:

RTS and linear mass feed directly into sag-tension calculations. If the figures in the tender disagree with the standard, each bidder must guess which one governs — and they will not all guess the same way, so the bids stop being comparable.

• Nominal aluminium and total cross-section in mm²
• Stranding and nominal wire diameters (e.g. 26/7 for a common ACSR construction)
• Overall conductor diameter with its tolerance
• Linear mass in kg/km
• Rated tensile strength (RTS) of the complete conductor in kN
• Direction of lay and, where the design requires it, lay-ratio limits per layer

The single most important electrical acceptance value is the maximum DC resistance at 20 °C, in Ω/km, for the finished conductor. It is the parameter that ties the product back to the conductivity of the aluminium rod, normally expressed in %IACS; hard-drawn EC-grade wire is commonly specified at around 61 %IACS.

Also state the maximum continuous operating temperature the line design assumes. If the line will run hot, say so explicitly and reference the thermal-rating basis — IEEE 738 is the usual calculation framework — so the manufacturer can confirm that the construction and the grease grade suit that temperature.

For ACSR, specify the steel core explicitly: galvanized steel wire together with its zinc-coating class, or aluminium-clad steel (ACSR-AW) where coastal salt spray or industrial pollution makes plain galvanizing insufficient.

Then settle the grease question: which layers are greased (core only, all layers except the outer surface, or none) and what temperature grade applies — grease with too low a drop point will migrate out of a hot conductor. This is the part of the specification most often left blank, and it is precisely the part that determines service life on aggressive routes.

The contractor's stringing plan is built around drum lengths, so these belong in the RFQ itself, not in a post-award negotiation:

• Standard length per drum with its tolerance, and the total number of drums
• Minimum acceptable length and the allowance for short lengths
• Drum construction (wooden or steel), lagging and protection of the outer conductor layer
• Marking: conductor designation and standard, actual length, gross and net mass, drum number, direction of rolling
• Storage requirements if the conductor will sit outdoors for an extended period

Distinguish clearly between type tests, which prove the design (for example the stress-strain test and the breaking-strength test on the complete conductor), and routine or sample tests, which prove the specific batch being delivered. Then list your demands explicitly:

State acceptance tolerances — diameter, mass, resistance, lay length — by reference to the governing standard, and resist inventing tighter ones without an engineering reason: they add cost without adding value.

• Sample tests per the governing standard: wire tensile strength and elongation, resistivity, mass of zinc coating and wrap test for galvanized core wire, surface condition and dimensional checks
• DC resistance of the finished conductor
• Material certificates for the incoming rod (EC grade, %IACS)
• Test reports traceable to individual drum numbers, plus the calibration status of the test equipment

Say who inspects, when, and against what. A workable minimum: a notification period before final testing, the sampling plan, the list of tests the purchaser or a third-party inspector will witness at the factory, and the documentation package — test reports, certificates, packing list — that must be approved before shipment release. Ambiguity here buys no time; it merely moves the argument from the tender stage, where resolving it is cheap, to the factory floor beside loaded drums, where it is expensive.

The errors that appear most often in conductor tender documents:

As for the perennial buyer's question — why is there no published price list? The honest answer is simple. The dominant share of a conductor's price is metal, priced against the LME aluminium quotation (plus the steel core), which moves daily; conversion cost then depends on the specific construction — the number and diameter of wires — and on order tonnage and drum configuration. Quoting per RFQ is not evasiveness; it is the only way to give a firm, dependable number. The practical consequence for the buyer: the more complete the specification, the faster and firmer the quotation that comes back.

• Quoting a code name with no standard, or a standard with no edition
• Copy-pasting a table from an old tender so that RTS, mass and resistance no longer belong to the same conductor
• Ignoring core coating class and grease for a coastal or industrially polluted route
• Setting tolerances tighter than the standard with no design justification
• Omitting drum lengths, which makes bids non-comparable and breaks the stringing plan