good morning everyone I'm Pro kuku and I'm going to be doing a presentation on cable ampacity and
to begin the process I guess it's fair to say that cable ampacity is really conservation of
thermal limits like any other device that thermal determines how much current you
can put in that device cables are no exceptions except the conditions are not determined solely
by manufacturers or by tables we have to do a lot of work to determine the actual capacities or the
approximate ampacity that we can put in the cable based on the cable construction and the layers of
insulation and and like armor or sheet and so on the way the location of installation and the
weight is installed ambient temperature group in effect the other thermal sources that are
in vicinity of the cables and of course we're not just talking about the fundamental convey
the harmonics would have different temperature rise in the cable so how do we go about doing
this the methods are I guess we can say there are three methods essentially one is actual thermal
calculations and that's one of the methods that we're going to go through one is based
on manufacturer base ampacity and correction factors and the third method is I'm patty tabled
by a standard and we'll cover all three of them during this process the methods that are presented
in a tab are available in eat AB are listed here near my graph and is e60 287 those two methods are
based on thermal analysis then we have I Triple E 399 IC EA p 54 440 NEC VSS tantor 76 71 and I
see six zero three six four and I'd like to cover all of these in half and off so let's see how fast
we can cover them on the thermal calculation we have both methods are for underground dark
banks and direct buried and that is I'm going to switch the e tap actually right now and bring up
a dark Bank and for those of you who have not worked with the dark Bank is it can be in any
shape or any format that you like to have it I am moving this cable over and in this cable cable to
that you see right here is actually a cable in the one-line diagram it's the same cable if I
double-click on it you're going to see the same editor that you double click on a cable from the
one-line diagram the loading page determines how much current is flowing through this cable and
you did you also can select the actual loading of the cable from from the operating current which
can also be from that comes from like load flow or it can be from actual measurements
in the field from real-time data full load am from equipment this cable is speed in a switch
gear and amp rating of the switch gear is 225 so you can say say to that or you can use your
own and pass it as you like defined user-defined so if I say for example hundred twenty amps that
would be useful for the cable sizing of the for this cable the just to show you this cable I can
delete it from here go to the Mon line diagram and I can actually drag and drop this cable from here
I have to be in edit mode I can drop the drag and drop this cable from here
I'm trying to drag and drop it here we go and so you can see the same cable that it's exist
in the bond line diagram is placed right here now here we can on there from the study case
I'm waiting for the okay from the silicates you can see you can select new my graph or
IEC six year old 287 and the process here I can do temperature analysis and as soon as I
do temperature and all set I can look at the temperature of the cables and as you can see
I can have extra external heat sources so for example if I move the external heat source down
here and do the cable and do the temperature now says and you can see lot of cables are over the
limit now over 90 degrees limit that set right here so this is essentially you can do both both
methods for analysis of the I guess I'm done with with the terminal calculations the layers
the cape of layers in 7.1 we have increased a lot of cable layers in the system so it's a lot more
comprehensive as the type of cables we can handle for both of these methods for thermal analysis so
I guess for underground cables you can say this is the most comprehensive method of doing it if
I go to the I see a 440 which is really for cable trays only this method is not really
a table format although it when you look at the standard it looks like a table format but is the
semi thermal calculation you don't have it base ampacity to calculate the related ampacity all
the data that pass is actually calculated by this method for this method if I go to eat up again
if I take the same cable to now I'm going to I'm not going to use thermal analysis I can go
right here and select the standard here on the page ampacity select the I see a 440 and here
the only option you have is type is above ground cable trays I can put the height let's say this is
6 inch height the width is 18 inches and let's say is 30% feel and as soon as I put this the
program calculates 453 amps as the current that I can put in this 750 KC meal cable and you can see
that there is no reference to any base ampacity for this cable so this is I see a 54 for 40 and
you can still have different type of trays and so on we also have additional leading factors
because of the fire protection you can have fire coating fire stop and fire wraps so if
I go for example fire coating I can select from the library we only have plain master for fire
coding and if I put them on each fire coating on there you can see the related ampacity drop to
390 amps automatically you can also have fire wraps additional fire protection or fire stop
when you going through a wall and by doing by doing that the delay that I pass T goes down
as you as you do so so this is the concept on I guess you can say that method is I see a is
semi thermal now the rest of the methods that we have in E cap or the standards are really concept
of de-rating factors you take the base ampacity and multiplying it by JD factor and you get the
related ampacity the bass ampacity could be data provided by the by the manufacturer or
it can be provided by the stand or through tables and I'll go through those as we move
on the delayed in factors depending on the type of installation that you have would be
from based on ambient temperature and conductor temperature our standard for any installation of
course but then depending if you install the cable above ground or on the ground you have
affected in factors and we'll go through those as we go through different methods the first
method is I Triple E 393 339 which is the brown book now arabica 4 is going to be published as I