主页/文章/高压设计

波形电缆额定电流

What are waveform cables and where are they used?

Waveform cables are commonly used in the United Kingdom (UK) for low voltage power networks. The term waveform refers to the way the neutral/earth wires are laid around the cores/bedding. Using this configuration enables the neutral/earth wires to be opened so a connection can be made to the conductors anywhere along its length. These cables are multicore cables with a typical voltage rating of 600/1000 V with standard conductor sizes ranging from 35 mm² to 300 mm². Waveform cables are usually insulated using XLPE materials and are sheathed using PVC. These types of cables are suitable for common installation configurations such as unenclosed in air, buried underground or submerged in water, indoor and in cable ducts.

Construction of 3- and 4-core waveform cables

3-core waveform cable is shown in Figure 1 where the following letters denote:

Aluminium conductors – sector shaped
XLPE insulation
Rubber bedding layer
Copper neutral/earth wires
PVC oversheath

4-core waveform cable is shown in Figure 2 where the following letters denote:

Aluminium conductors – sector shaped
XLPE Insulation
Rubber bedding layer
Copper neutral/earth wires
PVC oversheath

How to model waveform cables

A waveform cable can be modelled diagrammatically by hand and equations can be used to calculate the current carrying capacity of these cables. Alternatively, Cable HV^TM software can be used to expedite the process and for better accuracy.

To determine the cable current rating the construction of the waveform cable including the material types and the thicknesses of the layers needs to be known.

The manufacturer datasheet provides the waveform cable construction details required and a cable model is built to match in the editor window of Cable HV^TM software.

The waveform cable construction data for various cable sizes is outlined in Table 1.

	Solid aluminium conductor size
	35 mm²	70 mm²	95 mm²	120 mm²	185 mm²	240 mm²	300 mm²
层数	价值
Insulation: - Material - Temperature Limit - Thickness (mm)	XPLE 90ᵒC 0.9	XPLE 90ᵒC 1.1	XPLE 90ᵒC 1.1	XPLE 90ᵒC 1.2	XPLE 90ᵒC 1.6	XPLE 90ᵒC 1.7	XPLE 90ᵒC 1.8
Filling: - Material - Thickness (mm)	Rubber 1.15	Rubber 0.1	Rubber 0.1	Rubber 0.1	Rubber 0.1	Rubber 0.1	Rubber 0.1
Concentric Neutral/Earth Conductor: - Material - Temperature Limit - Nom. Diameter Of Wires - No. Of Wires	Copper 90ᵒC 1.04 26	Copper 90ᵒC 1.85 16	Copper 90ᵒC 1.85 22	Copper 90ᵒC 1.85 28	Copper 90ᵒC 1.85 41	Copper 90ᵒC 1.85 41	Copper 90ᵒC 1.85 41
Sheath: - Material - Thickness (mm)	PVC 1.8	PVC 1.9	PVC 2.1	PVC 2.2	PVC 2.5	PVC 2.7	PVC 2.8
Approx. Overall Diameter (mm)	26.3	30.5	33.4	35.9	45.3	51.2	53.4

Table 1 – Waveform construction data

Current rating calculation results

After the cable model files were created the current rating for various installation conditions could be investigated using the software. For example, as can be seen from Figure 3 for a 35 mm² cable the maximum permissible current rating is 129 A for the unenclosed in air case.

In Table 2, the results for all the cables sizes and their installation conditions are presented. The cables were modelled based on standard conditions as follows:

Maximum conductor temperature 90°C.
Ambient air temperature 25°C, ground temperature 15°C.
Depth of burial 0.5 m and thermal resistance of soil 1.2°C m/W.

	Max. permissible current rating (A)
	Installation configuration
Cable size (mm²)	Buried	Duct	In Air
35	138	109	129
70	210	168	209
95	251	204	255
120	285	234	296
185	362	305	390
240	420	358	462
300	475	406	532

Table 2 – Waveform cable current

When comparing the cables in terms of cable size, larger cable sizes are able to carrying larger currents. Generally, in-air cables perform the best in terms of current carrying capacity as the heat dissipated from the cable is unrestricted allowing the cable to carry its maximum current for its temperature rating. Cables contained in ducts performed the worst as the heat dissipation from the cables is restricted within the enclosure reducing its current carrying capacity to approximately 80% of its unenclosed equivalent.

免费试用我们的 IEC 60287高压电缆额定值计算软件。

Final words on waveform cable modelling

Waveform cables are ubiquitous for low voltage power network reticulation within the UK. The wave formation of the neutral /earth wires assists in cable stripping when the jointer accesses the phase conductors. The standard construction of waveform cables lends itself well to software modelling and one can easily calculate their current rating for various conductor sizes or specific installation conditions.