How to Calculate the Short Circuit Current rating Capacity for Cables??

Just recently i learnt something new..the basic concept of engineering..once again almost forgotten until I was asked this question..."Do you know how to calculate short circuit current rating capacity for cables?", for a moment i stop and think.. i didnt know what is the answer...
*(^-^)* - (embarrased)

From there, i didn't stop but I started checking through my text books, surf internets, discuss with my collegues who in charge with planning, protection schemes and etc..

I finally found the answer..it is just a very simple formula..

Isc = VLN/Sqr. Z^2 ; VLN = Line to Neutral Voltage
Z = Positive sequence impedance of the cable (u can get from the
technical particular of the cable)

Very simple right...wait a minute, don't be mistaken with the other formula where u need to add in the impedance of the transformerr and generators. U need this data when u want to know what would be the the short circuit current when fault occurs on any part of the system..

Authorised Person

Yesterday was the 1st time ever that I take charged for switching off bay in order to carry out works in the switchyard. Luckily everything went smoothly.



This time, we had requested outage for a 132/33kV transformer bay in order to replace the Neutral Earthing Resistor (NER) by the contractor. The work started at 7:00 am and completed at 4:00pm.



So as an Authorised Person in charged, I have to make sure that all safety precaution for the works are in place. So, after the switching whereby the Tx bay was off, isolated, I have to make sure that it was discharged and earthed and remain dead during the entire work. Portable Earthing were installed at both HV and LV side of the transformer.



Confirmed that the bay is safe for working, I gave safety briefing to the workers. Informed them on the coverage of area that was safe for work and are that is Live an dangerous. I also ensure that all workers were wearing Personal Protective Equipment (PPE) such as safety helmet and safet shoes.

Professional Engineer Part 3

Finally the day for the P.I had over. However, I still got few more works to do in order to be a
P.Eng. as i need to submit a clearer schematic drawing to my interviewer. This is because the drawing in my submission earlier was not clear and the fonts are small. So I have to enlarge and make another copy of drawings.

Another things, I have to put more spice into my essays..hehe so needless to say much..just re-do it. At least my interviewer is very sporting and considerate as He gives chance for me to re do and improve. So lucky me! *(^_^)* (Thanking God for that)

Now, I just need a little bit more time to complete my essays and get my mentor to sign new copy enlarged drawing....hopefully i can get it done fast..(too many works to do in the office...duiiigiiiaa I'm so overwhelmed now)