Power System Analysis for Overload?
Power System Analysis for Overload?
(OP)
Need some guidance in a study I am trying to attempt as a EE in training.
Background: I work in the O&G industry and we have our own generation, transmission, and distribution. I have a distribution circuit that has high 13.8kV and low 120V. It consists of two substations both of which are 13.8kV. The first substation supplies a 4500HP compressor motor, feeds second substation, and two 120V loads. The second substation just feeds two 120v and two 480v. The circuit are setup for redundancy with normally open circuit breakers, I am not sure what this setup is called.
I am attempting to use ETAP to study this circuit under conditions which may result in equipment being overloaded. We want to know the conditions under which it will be operating above equipments nameplate rating. I am completely new to this and not sure what is the best method to approach this.
I am sure I am not even aware of what is needed to complete such a study. Let alone calling it a study. This is the only place I know to begin.
Background: I work in the O&G industry and we have our own generation, transmission, and distribution. I have a distribution circuit that has high 13.8kV and low 120V. It consists of two substations both of which are 13.8kV. The first substation supplies a 4500HP compressor motor, feeds second substation, and two 120V loads. The second substation just feeds two 120v and two 480v. The circuit are setup for redundancy with normally open circuit breakers, I am not sure what this setup is called.
I am attempting to use ETAP to study this circuit under conditions which may result in equipment being overloaded. We want to know the conditions under which it will be operating above equipments nameplate rating. I am completely new to this and not sure what is the best method to approach this.
I am sure I am not even aware of what is needed to complete such a study. Let alone calling it a study. This is the only place I know to begin.






RE: Power System Analysis for Overload?
First I would suggest sketching a Single Line Diagram (SLD) from the top draw the 13.8kV input ( overhead power line / cable?)
connected to the first substation bus then add the 4500hp feeder circuit and 2 x 13.8kV /120v TX's (A)then draw a 13.8kV feeder to the next substaion bus
and add feeder circuits for 2 x 13.8kV /120v TX's and 2 x 13.8kV / 480v TX's.
I am not sure where the redundancy supplys comes in on a single 13,8KV ? however, should there be two 13.8kV incoming supplies then (A) is the redundancy.
ETAP Modelling
1.The first symbol ia a source symbol which will require info such as the Utility Fault level, X R values, Voltage etc.
2.Then choose acable or power line size to the substation
3. Choose a bus and fill in details
4. Incoming cct breaker symbol
5. Outgoing cct breakers on both subs
6. 4500hp load ( Motor Symbol)
7. TX's Symbols fill in details
8. Unless you know the loads ( put in lump loads)
9. Do the same for other sub.
Connect both substation via cct breakers.
Contact your nearest ETAP service dept for assistance.
I hope this assists you maybe other engineers can give input?
RE: Power System Analysis for Overload?
Also, since you are an EIT, why not ask your supervising eng. for pointers? You can always ask questions, in fact that's the right way to do it and as a future professional your are expected to do so to expand your field of knowledge and expertise. The only thing is not to ask the same question over and over!
As suggested by PadlOck01, start with the SLD. You will then build it in ETAP and run a load flow study that will give you the current passing thru your conductors, transformers etc and help you flag potential overloads for various network configurations (like transfer on the alternate supply). You will also discover that you will need more info like load kVA & power factor, transformer impedance, equipment current carrying capacity etc.
Welcome to the EE job!
Desrod
RE: Power System Analysis for Overload?
Also does ETAP alert on overload?
RE: Power System Analysis for Overload?
RE: Power System Analysis for Overload?
You should also confirm that the nominal ratings of your cables, transformers, generators, etc are site-rated (i.e. suitably derated or uprated for site conditions such as temperature).