Answer / kekshavanarayana.g

Derating factor depends on ambient temperature & how u r
laying the cable ie., in Air,Duct,Burried.
normally the current carring capacity of a perticular cable
is calculated at 40*c, but if u lay the cable in air then
it includes the temparture around it,if it increases more
the 40*c then the conductor gets heated up by increasing
the resistance in it thus the current carring capacity of a
given cable decreases, so we will derate the cable

Answer / dkmathur

Apart from higher ambient temperature than 40 degree which
derate cable, the depth of cable for UG Cable, distance
between two parallel cables also derate cable.

Answer / helwan university

type of derating factor:
1-soil thermal resistivity
2-grouping factor(cable distrubtion in trays horizontial
-verticals)
3-temp derating factor
4-burial depth derating factor

Answer / lakhwinder singh

Derating factor =Derated current capacity/cable ampacity

derating facor depends upon :- Ambient temp.
grouping of cable
thermal resistivity of soil
depth of laying.

Answer / amit

Derating factor of cable is depends upon following factor

1)Cable laying depth
2)Ambient temperature
3)Ground temperature
4)Parallel cable distance

Answer / shvetang dave

Die electric factor depends on the temperature around the
cable, method of cable laying etc..if cable is to be design
for 35 deg c and if temperature increases above 35 deg c
then resistance of cable increases (positive temp.
coefficient), so its current carrying capacity will
decreses...So current paseed through cable will decreases,
it menas its capacity will down..it's called derating
current and notrated current...and same effect is done for
cable laying method...By using good insulation and proper
method of cable laying reduces its effect...

Answer / dev bala

derating factor depents on withstand level of ambient
tempreature,when it increase at tat time resistance of
cable is increase so current carrying capacity of cable is
decrease so it will derate the cable rating..
then based on the cable fixed in a cable tray and the
distance between the cable in tray...

Answer / kaustav bhadury

Answer 9 is the most comprehensive...
U get loads of standards based on the country u r in..
If in duct-
1) Soik Thermal resistivity : Basically the max temp in the
surrounding. 40*C is the standard.

2) Conductor grouping : Due to arrangement of multiple
conductors there is a development of an EM field which
opposes the flow and thus we need to consider this factor.

3) Temp. Derating Factor : In this the arrangement of cables
in a conduit is of prime importance. It should be in such a
way that all cables have a minimum space to dissipate heat
into the surroundings. The cables can touch each other but
anyone cable should not be fully surrounded by other cables.

4) Burial Depth : Depends on the length below ground where
the conduit is laid.

Answer / ameer reda

derating factor in the cable means reduction in the current carring capacity of the cable
there are many reasons :
1- ground temp derating factor
2-air temp dearating factor
3-burial depth derating factor
4-soil thermal resisvity derating factor
5-pvc rated temp derating factor
6-trefoil or flat formation derating factor for the three and single core cable laid direct in ground
7- trefoil formaion derating factor for multi core cables laid direct in the ground
8-reduction factors for groups or more than one multi core cable in air to be applied to the current carring capacity fore one multicore cable in free air
9-reduction factors for groups or more than one circuit of single core cables to be applied to the current carring capacity for one circuit for single core cables in free air

Answer / amjad riaz

derating factor is also inverse of thermal temperature.

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