Morning
This is a query about when 90 deg cable CCCs can be used in the cable calculations.
BS 7671 states that switchgear, protective devices and accessories shall not be connected to conductors intended to operate at a temperature exceeding 70 degrees unless the equipment manufacturer has confirmed that the equipment is suitable for such conditions. Hence we use the 70 deg CCC values when using XLPE 90 deg cable.
The confusion is that the switchgear for example is tested under BS EN 61439-2 which allows a 70 degree rise on the terminals - BUT - with a maximum ambient temperature of 35 degrees. Therefore the terminals during testing could potentially be at 105 degrees...?
We have asked many manufacturer about this and generally get the response that its tested to BS EN 61439-2 which allow for 70 deg above a max ambient of 35 deg.....
Is there a minimum ambient temperature the terminals are tested to?
Thoughts please on when we can use 90deg cable CCC values in calculations?