HT COMBIG2, User Manual

Page: 153 / 164

Gx Series
EN - 152
13.11. VERIFY OF THE PROTECTION AGAINST SHORT CIRCUITS – TEST I2T
The I
2
t parameter represents the specific energy (expressed in A
2
s) let through by the
protective device in short-circuit condition.
The
I
2
t energy must be able to be supported both by the cables and by the distribution
bars. For cables, the following relation applies:
 
t I S K
2
2
*

(1)
where:
S = section of the protective conductor in mm
2
K = constant dependent on the material of the protective conductor, on the type
of insulation and the temperature that can be obtained from the tables
present in the standards (the instrument refers to a fixed environment
temperature of 25°C, single cable not buried, no harmonics).
Starting from the evaluation of the three-phase or single-phase
Isc short-circuit current ,
the instrument calculates the maximum value of I
2
t parameter on the basis of the
characteristic curves of the selected protection (MCB or fuse), and runs the comparison
with the previous relation (1).
If the test gives a positive result, the
selected section of the protective conductor is
adequate for the management of the protective device chosen. In case of negative result,
it is not necessary to select a higher value than the section or change the protection.
The following selections (*) are available on the instrument:
 MCB current (B curve) selectable among values:
3,6,10,13,15,16,20,25,32,40,45,50,63,80,100,125,160,200A
 MCB current (C, K, D curves) selectable among values:
0.5,1,1.6,2,3,4,6,10,13,15,16,20,25,32,40,50,63, 80,100,125,160,200A
 Nominal current Fuse BS88-2 selectable among values: 6, 10, 16, 20, 25, 32, 40, 50,
63, 80, 100, 125, 160, 200A
 Nominal current Fuse BS88-3 selectable among values: 5,16,20,32,45,63,80,100A
 Nominal current Fuse BS3036 selectable among values: 5,15,20,30,45,60,100A

Nominal current Fuse BS1362 selectable among values: 3,15A
 Conductor material: selectable between Cu (Copper) and Al (Aluminum)
 Conductor insulation: selectable among PVC , Rub/Butil (Rubber/Butyl rubber) and
EPR/XLPE (Ethylene propylene rubber/Cross-linked polyethylene)
 Conductor section free selectable and possible number of parallel cords (max 99)
CAUTION
The verifies made by the instrument does not replace in any case the
design calculations
(*) The values could be subject to variations