What is the formula to find out cross sectional area of
cable for certain current rating?
- 1 Answers
- 7031 Views
- MRF, I also Faced
- E-Mail Answers
Answer Posted / tarun aggarwal ymca
what u have to first take into mind what type of cable u want to purchase....then its size matter
usually we use XLPE insulated cable for Power cable and Aluminum or copper its depend upon the cost and loses
mean if u need large length cable you have to prefer aluminum in shorter length copper cable is preferred as its resistivity is less
for example
VLL = 11kV (line volatge)
L = 1.3km
Maximum allowable Vdrop = 2.5% of VLL i.e.Vdrop = 275V
SkVA = 3000kVA (Total Power we have to transfer of to be used by the connected load)
Full load Current If= SkVA/root3 VLL i.e If = 157.5A
Demand factor is what we actually demand the current (it not always full load current what we demand) Let D.F = 80% of If
Id =D.F x If (Demand Current) where D.F = Demand Factor i.e Id = 126.0A
The cable current carrying capacity is always kept larger than the demand current let S.F for Cable in % = 30% Extra Id
Ic= (1+S.F/100) Id i.e Ic = 163.8A
This current is what will be safer current that will be carried out by cable
Now derating factor K is calculated by the following equation
K = Kground x Ktherm.res x Kdepth x Kgroup
Vdrop = 3IdL root(Rac cos􀄳+ Xsin􀄳)
Now cable data is refered
Type 3 Core, Copper Conductor, XLPE insulated, Copper tape Screened, PVC bedded, Steel Wire Armoured, PVC, 8750/15000V.
Parameter -------- 50 mm2---- 70 mm2 ------ 95 mm2------- 120 mm2 ------- 150 mm2 ----- 185 mm2
Irated (A) --------- 187----------- 227- ------------ 267--------------303 -----------------338------------------ 383
Kground----------------0.86
Ktherm.res-- ----------- 1
Kdepth-------------------0.98
Kgroup ------------------0.7
K-------------------------- 0.590
Icor (A) -----------110.32 --------- 133.92----------157.52--------- 178.76-------------199.41------------225…
Rac (ohm/km) --- 0.493 --------0.342------------ 0.247------------0.196---------------0.1… ------------ 0.128
X (ohm/km) --------0.118 --------0.112 ------------0.106------------0.102------…
P.F = Cos--------0.85
(In radian)-------- 0.5548------ 0.5548----------0.5548-----------0.5548-…
Vdrop (V)-----------196.76-------167.73-------…
Considering the values of Ic, Icorrected and Vdrop the best suited cable is 120 mm2
cable for connecting switchyard to substation
Sorry extra long answer but i want to explain in detail
| Is This Answer Correct ? | 7 Yes | 2 No |
Post New Answer View All Answers
Classify milling machines.
Where servomechanism is used?
How is magnetic leakage reduced?
For small size, high frequency coils, the most common core material is- a. )Air b. )Ferrite c.) Powdered ion d.) Steel
HOW DO YOU CAN CHECK A 15KV DIODE, WHETHER IT IS OK OR NOT?
What is meant by analogous system?
how can calculate resistance box for 15 kw, 6 pole, RV-230, RA-42 motor
What is the difference between the relay and the circuit breaker?
armature is that part in which current is induced since in dc motor we supply current to the conductor so why we call it armature?
hey guys i scored 910 on GRE and 67 on TOEFL respectively.I have an aggregate of about 74%in my B tech.For which colleges should i apply for an MS program in electrical engineering.I am looking for colleges in NJ,SC,NC,GEORGIA, NY. Please reply with a good response.....
why the projects getting loss?
why do we carry out winding resistance test?
Why two phase welding machine is used instead of three phase welding machine.
How to calculate MCB Breaking capacity.
solar inverters was not connected to the nuteral link .this nutwral possible to any other systems
