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Voltage

Entering the correct voltage for your cable is easy, with just a few points to keep in mind.

Voltage Input

The meaning of voltage value depends on the type of system under consideration:

  • a.c. three phase - is entered as the line-line voltage
  • a.c. single phase - is entered as the line-neutral voltage
  • d.c. - the magnitude of the voltage (L+ to L-)

Calculations

For a.c. systems to convert between line-line and line-neutral voltages we can divide (or multiply) by the square root of 3.  For example, 300V line-line would be 173.2V line-neutral. 

ULN=ULL3 

ULL=3ULN

It should be noted that there are also defined IEC and commonly used voltage ranges (line-line/line-neutral), which are rounded: 400/230V, 660/380V, 11000/6350V etc.  Within myCableEngineering we use these standard ranges if applicable, otherwise the mathematical conversion

Cable Voltage

Traditionally cables have been given two ratings (600/1000 V for example) indicating the maximum line-earth (U0) and line-line (U) voltage.  However, with the rapid growth of d.c. systems (particularly in the renewable industry), manufacturers are rating their cables accordingly (600/1000 V a.c., 1500 V d.c. for example).  Within our cable database, we maintain separate ratings for line-line, line-neutral and d.c for each cable.  In the display of cable ratings, we use the following format:

[U0 / U Vac Udc Vdc]        - for example [600/1000Vac 1500V dc], 6.35/11kVac [11kVdc]

Cable Selection

Determination and selection of cables are carried out primarily based on voltage and system phase.  Typically we will select the next highest rated cables, relative to the system voltage as suitable candidates to use. We further filter the list of cables based on on the number of phases (3-phase, 1-phase, etc.) compared to the number of cable cores.  The way phase and cores affect cable selection are covered in Impedance Calculation.

Additionally, we may apply special rules for certain cases:

  1. For low voltage, systems we select all cables greater than the system voltage and rated less than or equal to 600/1000Vac [1500Vdc].

 

 

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