Your transformer has a D winding in low voltage as i see in one of your sketch so i will not expect to feed a ground fault. What are the trafo winding settings in ETAP?
G.F.
www.engineering-services.gr
Don't you need anyway an insulation coordination study for the dimensioning of the arrester, taking in mind all possible cases like system symmetrical or asymmetrical faults, switching over voltages, energizing of lines ,load rejections etc?
G.F.
www.engineering-services.gr
Thanks ScottyUK for your comment, you are right.I thought we were talking about an MCCB feeding an MCB. For residential applications the opposite is possible but you throw away your money.
G.F.
www.engineering-services.gr
Have a look on those ABB discrimination tables attached. The case of MCB and MCCB is of course posible.
G.F.
www.engineering-services.grhttp://files.engineering.com/getfile.aspx?folder=71a57748-5484-43f1-80b4-1a41a7e0ab81&file=1sdc007004d0206.pdf
For secondary injections i am using Freja and Omicron. I prefer omicron as it has a big and user friendly test template library for almost all protection relays. With such a template you can automatically perform tests and prepare the relevant documentation.
G.F.
www.engineering-services.gr
Have a look in the attached file. It is from the generator i mention in my previous post.
G.F.
www.engineering-services.grhttp://files.engineering.com/getfile.aspx?folder=66452e3f-a74d-4814-b25c-e666f81c6c1b&file=LRCURVE.jpg
For a detail answer on the time needed for stabilization after starting such a motor you have to ask the generator vendor.
From my experience, a 1,2MW four stroke diesel generator running in lets say 10% load can start without any problems or significant voltage dips a 350kW motor. Depending on...
For the step up transformer you have to see what will be the voltage drop across the impedance for the motor start up current. Use as uk=5% as it is typical until 1000kva. A 1000kva transformer has a short circuit aprox. 28kA. Your motor if we assume it has 6 times nominal it will reach during...
If i was you, i would choose the generator trafo to be Δ in generator side in order to trap currents caused be asymmetries (I2) and the third harmonic caused by the non linear B-H characteristic of the transformer core. The other side is preferred to be Y solidly or earthed via impedance (that...
As far as i understand the 11kV network is ungrounded and delta connected (are you in an old cement factory?). The load flow is from the 33kv to 0,4kv and there is no power generation at low voltage side.
If the loads (motors or whatever) are connected in LV side then all the load asymmetries...
What are the transformer kVA and vector groups? What are the fuse ratings? Do you have any disturbance recordings from a protection relay? When you say hv fuses on the transformers you mean the 11kV side of the 11/0,4kV trafos? It seems very interesting.
G.F.
www.engineering-services.gr
A useful article from Kumblar and Kulkarni.
G.F.
www.engineering-services.grhttp://files.engineering.com/getfile.aspx?folder=41a561fc-e4e7-49aa-83db-d2295b23c949&file=Sympathetic_Inrush.pdf
Maybe this is useful,...
G.F.
www.engineering-services.grhttp://files.engineering.com/getfile.aspx?folder=50b6bd4f-6adc-44e8-acc3-8b2f31195a94&file=1SDC007109G0201.pdf
If i were you, i will do the following (for a 10MWp):
1) Chose at least 7x1250kva kiosks assuming 13,5% losses(or external inverter packs)
2) Place each kiosk or external pack at the middle of each own pv panels field territory (after a lot of studies this configuration has less power losses)
3)...
The MV power network of large scale solar plants follows the same principles as in the case of windparks. Just consider that you have an inverter kiosk instead of having a wind turbine. The same with the substation protection and automation concept. The only think that is different is the solar...
Let me also give some typical numbers in order to help you get an idea on what i mean when i am talking about installation easiness:
1)A typical 6kv N2XSY 1x240 cable has aprox. 3kg/m and maximum bedding radius of 15x40mm=0,6m while,
2)A typical 6kv N2XSEY 3x240 cable has aprox. 11,5kg/m and...
Of course for small cross sections (less than 150mm2) the multi core are preferred as the cost of installation is smaller than the single core (i.e. you you don't have to care about trefoil and similar concerns), so in my opinion labor costs are critical for that kind of comparison.
G.F...
