System simulation vs manual calculations

[14041972]

I work in an engineering department in a manufacturing plant and in two years we will be expanding our power systems to accommodate new machinery. Normally we would out-source such design work but for the obvious reasons we are planning to do it in-house. In endeavours to prepare for this project I am learning how to do these calculations by hand then verify them using software. I have ‘powerworld simulator version 8.0 - Glover & sarma edition’. The idea is to start off by recalculating our existing power system components i.e. transformers rating, cable sizes, fault levels, and switchgears ratings as an exercises.
These are the main components we have in the plant:-
· 2 X 132 KV/11KV, 30 MVA transformers
· 57 X 11 KV/400V, 1.6 MVA transformers
· 5 X 3.3KV/3.3KV 1.2 MVA Transformer
· 9 X switch rooms
· 3 X small lights standby generators (18.2 KVA, 50 KVA, 88KVA respectively)
· No overhead transmission lines – just underground

My question is
1) How many different parameters can I be able to calculate by hand and verify them using software – different parameters like faults, transformer sizes, switchgear sizing etc.
2) Does any one out there know of a site or a file I can use to learn how to do hand calculations or even better software.

Thank you for your kind assistance
Bestboy

 

[jtkirb]

The fact I used G&S's text in college I can assure you that their software is not the best...or even close. SKM software does what you seak, but is expensive.

Manual calcs are OK until you start trying to figure out faults and such which take a lot of time. You should be able to do feeder, transformer, and switchgear sizing with the loads you have and some knowledge of your system.

JTK

 

[davidbeach]

If you want to calculate that system by hand and get results you can use to check a computer program, it may be a good thing you have two years to work it out. The computer will give you all the system parameters for every location in the system. Back when such things were done by hand, only representative calculations would be performed; say the shortest circuit for fault calculations and the longest circuit for voltage drop calculations and those values used throughout.

I've used the SKM software mentioned by jtkirb, and it includes IEC calculations as well as ANSI calculations. There are many others, some more attuned to the ANSI world, others more to the IEC world. A search of this forum should yield many more, particularly the IEC software I'm not familiar with.

jtkirb indicates that the SKM software is expensive, I doubt it is price much differently than other comparable packages, but it may be that it is less expensive than not using it.

 

[jtkirb]

One mistake in switchgear to transformer sizing will pay for the SKM.

JTK

 

[jghrist]

I think it a worthwhile effort to do the calculations by hand first. It will force you to get a better understanding of the analysis and your distribution system. I would invest in a program like MathCad to make the calculations. This allows changing parameters without doing all of the math over. It also allows doing matrix arithmetic without going totally bonkers.

I would recommend buying the IEEE Red Book, IEEE Std 141, Electric Power Distribution for Industrial Plants]/i] and the IEEE Brown Book, IEEE Std 399, Industrial and Commercial Power Systems Analysis.

 

[saladhawks]

Why would you want to do hand calculations first and then verify with software? You should approach this just the opposite.

For an industrial facility of this size, trying to calculate fault current contributions and switchgear ratings considering connected motor loads (greater than 20 hp) will be a daunting "in house" effort.

There are many proven software packages on the market (such as SKM) that will perform all of your needed calculations. Run the software analysis first and then "spot check" certain segments of the system with hand calculations. That should be more than adequate.

 

[Deansharafi]

Trying to calculate fault values on a plant you describe above will be an absolute nightmare. SKM software with 100 or 300 buses will be sufficient and is not expensive compared to the time that you must spend on hand calculations.