Recent content by ohms

well, is there any recommendation by IEC on such particular cases?

jghrist Infact we have to provide the conductor. :-D thats the reason we dont want to oversize it without any technical reason. From your comments, I understand that you also see both as a separate thing and we can safely consider additional 70% for grid conductor sizing as I said in my above...

Hi every one, In our substation, the route of the HV power cable is through trench and pipe ducts. Pipe ducts consititute 25% of the route. For Cable calculations, how should we consider the laying method of the cable. Trench, Pipe duct or the worst of both. Or we do the calculation...

Thanks for your feedbacks. Infact, our customer wants us to take the Sf as 100% for earthing system design. That we agreed and did the calculation considering full fault current (without considering any dicersion). However, for Earth Mesh, we consider 70% of fault current for conductor sizing...

Hi every one. I am getting confused with the current division factor Sf for system design and the split factor for buried mesh. Can anyone shed some light on it with some references. Many thanks for your time.

yes

Hi guys, Melting point of Tin = 203 Melting point of Cu = 1083 For earthing calculation purpose, when considering tinned-copper wire, can we take 203 degree as the maximum allowable temperature, being on safe side as the MP of Cu is high enough to sustain this temperature. Thanks for helpful...

Yes, ambient temperature. I used the standard temperature coefficient to evaluate the inrease in resistance and therefore the current limit. NGR is rated for 25C and ambient is 50C. But the effect is negligible.

Apart from the standard NGR sizing calculation, do we need to take account the effeect of temperature on NGR sizing as well. Thanks if someone can guide me to calculate this factor.

Thanks, Your replies really helped me.

Hi everyone, We are doing the earthing calculation for 33/6.3kV SS. There are 2 nos. 33/6.3kV , 30MVA transformer Dyn11. For calculating the maximum grid current, should we consider - Maximum switchgear fault current 0r - Transformer 3 phase fault current at Y side thanks for helpful replies.

melon, nope, I definitely need some snap shot tool which support dual screen. Azim

Hi guys, We are providing control system for one station in Qatar. In our system we have one HMI computer with two screens. The desktop is extended to both screen. I have installed a snapshot tool (MV Snap) to capture the whole desktop, however, while capturing the complete desktop, it...

Normally the fuses are used in the current path to isolate the system, when there be any abnormal / high current. Whereas the Links are generally used in the neutral path just to isolate, where the current flow is very low during normal operating condition, and very high during earth fault...

Can anybody tell me, how to calculate the magnetising current for Class 'PS' or 'X' CTs. Required formulae are available for calculating the knee point voltage in the Relay catalogue. But none of the catalogue describes about the magnetising current requirement. I feel the magnetising current...