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Thank you 7another4!

Hello ! Please help me with the equations to calculate the starting time of a WRIM motor, started with an LRS. Data known: -Motor voltage rating; -Shaft power output; -Motor rotor inertia; -Load inertia; -In = I1 at full speed @ full load; -Locked rotor torque: 260% Tn -I2 and V2; -synchronous...

m3ntosan What is the size of the transformer and the winding configuration for the 400/25 kV TX you've mentioned? THX! Stefan

Thank you very much all! David, the application will be an iron ore processing plant. This will have six SAG Mills 25 MW each, 12 Ball Mills 12 MW each, a number of HV supplied pumps and other auxiliary loads. The total plant demand is around 450 MW. Overall, the plant will not be larger than 2...

Hello! It is possible to build a power transformer with these parameters: S=250 MVA V=500 / 30 kV Vector group: Preferably YNd ? What is the maximum transformation ratio a power transformer could have? Thank you in advance! Regards, Stefan

M3ntosan, I’ve dusted a bit my HV OHL theory. Based on a two port network: 1) Vs = AVr + BIr 2) Is = CVr + DIr Where: Vs = V @ sending end and Vr = V @ receiving end. A, B, C and D are OHL parameters. Pr is known, Ps is calculated from expressions 1. & 2. above. 3.) Ps - Pr = Plosses...

Yes, I'd like to know what is (are) typical / acceptable transmission losses for EHV lines, particularly for 400 kV and 500 kV. Thank you !

In terms of OHL efficiency (i.e. Preceiving/Psending [MW]) what is an acceptable value 5%, 8%, 10 %? Thank you m3ntosan! (Multumesc mult!) Thank you all for your help!

m3ntosan, What means SIL ?

Hello! I am working on a feasibility study, where I have to define a concept design and estimate de cost of the project. In this project, the process plant load will be supplied through a transmission line from a hydro power plant. The transmission line should be double circuit, each circuit...

Hello! I have to design an island power plant, maximum 45 MW, with a relatively high fluctuating load. Say continuously maximum 30 MW. The only fuel available is diesel. I am proposing a plant configuration based on 6 x 7.4 MW (N+1) = 37 MW medium speed diesel generators and 6 x 1.6 MW (N+1) =...

Hello! I am looking for advice regarding lightning protection of a tower crane. I have a tower crane, 55 m high. It is the highest structure on a few km around. The crane’s structure is connected at the base to the plant earthing grid (< 1 Ohms). The Client wants to have an lightning rod...

Thank you edison123 and 7anoter4!

Hi ! I am writing this tread to kindly request your opinions. I came across a Client technical specification for low voltage induction motors that states: “Motors shall be able to start under applicable load conditions with 75 % of rated voltage at motor terminals for DOL.” I believe that...

jcroley, If your transformer will always be used to supply 3 wires connected loads, you could save the neutral cable between the transformer and switchgear. However, you may want to consider installing a CT inside transformer’s LV junction box, to supply your earth fault protection scheme.

Jed057, Any 3 Ph. electrical feeder that supplies a load situated in a hazardous area shall be equipped with a 4 poles switching device. This is to mitigate the hazard that may appear due to accidental existence of potential difference between neutral and earth, which can represent a source...

Depends on which part of the world you are. For example, in Australia the AS/NZS 3835/2006 covers this issue. Regards,

Mike6061, In a generation – distribution system the generator is the weakest link from the short circuit withstand point of view. A metallic or bolted Earth Fault close to generator is generally higher than a 3 phase bolted fault @ generator’s terminals (For more details please see IEEE...

Most elevated S/Ss I’ve seen are up to 2 m. I believe that “cooling” of cables is not enough reason for elevating the S/S at 3m. In order to appreciate the elevation required, you have to make detail arrangement drawing, showing the ground level, cable ladders elevation considering HV & large...

Thank you for answers. Slavag, the power plant will work as an island power system, with no connection with a Utility (please see the attached sketch). I have mentioned in IEEE 142/2007, clause 1.7., the following advice regarding overvoltage & insulation stress: “special attention shall be...