ETAP Undervoltage on Bus

[PoliPoliCarps]

Hello Masters and Experts
Can I ask help?
I run calculations with ETAP. I got the marginal and critical warning.
Please see picture below.

I also attached the single line diagram (with Load Flow Analysis and Short Circuit Analysis)
Can you please help me fix the critical errors? What are the possible solutions?
Thank you in advance.

 

[magoo2]

I don't use ETAP so keep that in mind. On your load flow analysis, it looks like you started off with 1.0 per unit voltage and all the voltages downline are naturally lower. Doesn't your 6.6 kV bus normally run around 5% higher? This might keep the resulting voltages above the marginal limit.

On your short circuit analysis, where is the fault? Bus 2 or Bus 3?

 

[PoliPoliCarps]

Hi magoo2.
Actually I already adjusted the tap of the transformer to 5%
Can you explain further?
I tried the fault on both bus.

 

[jghrist]

Reduce load or increase size of feeder conductors to reduce voltage drop.

 

[LionelHutz]

You do know that is just the default warnings? You should be determining what you want from this system, not what Etap uses as defaults.

You have to look at the load flow data and decide where there are issues that you do want to address. Then, you take steps to correct those. For example, bus2 to bus3 is a 4.5% drop so it might be decided to do something about that. So, you would need to look at T2 and Cable4 to see what can be done to increase the loaded voltage on bus3 without causing too much voltage on bus3 when the system is at idle. You might also look at T1 to see if you can increase the voltage on bus2 but once again making sure you don't over-voltage the system at idle. Automatic tap changers might be a solution?

You never said what's wrong with the short circuit analysis, but it must be bus bracing alerts, possibly because you didn't enter it right and left defaults. The only alerts that occur are for bus bracing and protective device capacity, which you have none of. Normally, you do the study to find the fault current the MCC bus needs to support and then you can specify the equipment based on that data. When you open the bus editor under the ratings tab once you pick the type from the dropdown the fault ratings appear and can be entered. 27kA on a 400V MCC bus is not that high a fault current.