Derating Factors Sprme
1
65 66 Distance from the wall > 2cm Clearance between system = 2d DERATING FACTORS Cables laid on the ground in flat formation 0.95 0.9 0.88 Cables laid on troughs (circulation of air is restricted) 1 2 3 6 0.92 0.87 0.84 0.82 0.89 0.84 0.82 0.80 Number at troughs 0.88 0.83 0.81 0.73 Cables laid on racks in flat formation 1 2 3 5 1 1 1 1 0.98 0.95 0.94 0.93 Number of racks 0.96 0.93 0.92 0.9 Arrangements for which a reduction of the current rating is not necessary Any numbers of systems 2cm 2d 2d d 2cm 2d 2d d <x2Dcm 2cm 2d 2d d <x2Dcm 2cm 2d 2d d <x2Dcm In the case of flat formation which increased distance the reduction in the manual heating is offset by greater sheath losses. It is impossible, therefore, to give data about arrangement for which a reduction is not necessary 25 1.04 1.07 20 1.08 1.12 Air Temperature (°C) XLPE Cables PVC Cables 35 0.95 0.93 30 1.00 1.00 40 0.91 0.87 II.Cables laid in the air Derating factor for variation in air temperature DERATING FACTORS Grouping in Air Distance from the wall > 2cm Clearance between cables - diameter d Cables laid on the ground in flat formation 45 0.87 0.79 50 0.82 0.71 0.92 0.89 0.88 Cables laid on troughs (circulation of air is restricted) 1 2 3 5 0.92 0.87 0.84 0.82 0.89 0.84 0.82 0.80 Number at troughs 0.89 0.83 0.81 0.73 Cables laid on racks in flat formation 1 2 3 5 1 0.97 0.95 0.94 0.97 0.94 0.93 0.91 Number of racks 0.95 0.93 0.92 0.80 Cables arranged on structures or on the wall Touching the wall 0.94 0.91 0.89 0.89 0.85 0.84 Note : * If the ambient temperature is change, apply the derating factor in the table II-1 Table II-1 Table II-2 Single Core Cables in Three-phase Systems These factors are valid only under the condition that the ambient temperature is not perceptibly increased by the heat generated by the cable (see note*) <x2cm <x2cm 20cm <x2cm 20cm <x2cm
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ELECTRICAL
Transcript of Derating Factors Sprme
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65
66
Dis
tance
fro
m t
he w
all
> 2
cm
Cle
ara
nce
betw
een s
yste
m =
2d
DE
RA
TIN
G F
AC
TO
RS
Cab
les
laid
on t
he g
round
in f
lat
form
ati
on
0.9
50.9
0.8
8
Cab
les
laid
on t
roug
hs
(cir
cula
tio
n o
f air
is
rest
rict
ed
)
1 2 3 6
0.9
2
0.8
7
0.8
4
0.8
2
0.8
9
0.8
4
0.8
2
0.8
0
Num
ber
at
tro
ug
hs
0.8
8
0.8
3
0.8
1
0.7
3
Cab
les
laid
on r
ack
s in
fla
t fo
rmati
on
1 2 3 5
1 1 1 1
0.9
8
0.9
5
0.9
4
0.9
3
Num
ber
of
rack
s
0.9
6
0.9
3
0.9
2
0.9
Arr
ang
em
ents
fo
r w
hic
h a
red
uct
ion o
f th
e c
urr
ent
rati
ng
is
no
t nece
ssary
Any
num
bers
of
syst
em
s
2cm
2d
2d
d
2cm
2d
2d
d
