Interested to Buy Any Domain ? << Click Here >> for more details...
Why short circuit calculation is not required in LT cable
sizing and requiredin HT cable sizing only
- 2 Answers
- 12104 Views
- Chemtex, I also Faced
- E-Mail Answers
Answer Posted / sudhanva madhukar mahamuni
Generally LT Cable size are not calculated based on Fault current basis, Due to High Fault current on LT System. For e.g. consider that 2500 kVA Transformer, %Z = 6.25%, 415 Volts at Secondary. Fault Current at Secondary system will be 55.64 kA. Now if we would have to select the Cable size based on Fault current then it would be ---
If √t
A = ----------------- Sq.mm --- For XLPE Cable Aluminum Conductor
0.094
585 sqmm, nearest standard rating of cable is 630 sqmm. Hence Commercially as well as laying point of view the same is not recommended nor as per good engineering practice.
HT Cable Sizing :
Cable sizing based on Fault current is possible In HT System, based practically and commercially point of view. Consider that 11kV system is feeding the power supply. As per IS 2026, 11kV Power system will have max 500MVA Fault Level. It means it will have 26 kA. 300sqmm cable will be sufficient to withstand 26 kA for 1 Sec.
Summary : System Design shall not be strictly as norms, it should be design considering Laying / installation, Practically and Commercially viable.
Regards
Sudhanva Madhukar Mahamuni
electricmahamuni@gmail.com
| Is This Answer Correct ? | 2 Yes | 2 No |
Post New Answer View All Answers
Direction of flow of active power and reactive power with logic?
Where should the lighting arrestor be placed in distribution lines?
What is shunt voltage and u v voltage witch one best
how to electronic energy metter failed in electomagnectic fild passing in the metter and which thing to defect more on metter.
how can service sitting be setted for MCCB?Example for sittings IR (CURRENT RATING),IS(CURRENT STARTING)IO (current operating)?
Explain the following and how these are working with PLC Unit 1 I/O Module Card 2 Adaptor Card 3 Ribbon Adaptor 4 I/O bus 5 I/O Devices
what is capacitor voltage transformer?? how it is different from potential transformer?
What are the advantages and disadvantages of the ac motors?
where does 22kv line starts
how works inductive &capacitive sensors?
We have drive feeding an output contactor for a 5000 hp motor @ 5kV application. The motor FLA is 629amps x 1.25% service factor = 786.25 amps The cable that we current have in place between the drive and the output contactor is 350kcmil- MV-105 (parallel cables). Per the NEC table 310.60 (C) (69). This show the cable ampacity is at 615 amps per cable for a rating of 1230 amps. We have derated the cable for the cable tray and the multiple cables application and our calculations show that after the correction factor factor we are at 922amps. 1230 amps x .75% correction factor factor = 922.5 amps. The customer is driving us to then use another safety factor of .25% off of the already derated cable. Can you please provide a longhand calculation for your solution on this application?
2- What are the percentages between excitation currents in phase (R, S and T) in ∆ and Ỵ connections in excitation Current test in transformers?
What is the physical significant of power factor?
can we do the star delta connection of capacitor for 3- phase motor starter.
HOW TO CALCULATE EARTHING SIZING?
