cable choosing

You must follow the local regulations, which will specify a minimum size for the conductors. Since we don't know where you're from, can't advise any further.

Hello Progress,

150 amps at what voltage?

is the cable buried?

i am not discouraging you but please do give more details for a better answer.

Cheers.

Must see Electric Code for the Country of yours.

Meters suggest you are not in the USA where they have a table for this selection (Max current allowed by a wire, called ampacity in the USA also a function of other parameters, e.g. temperature).

Next is the check-out for allowable voltage drop.

A selection for voltage drop required: %% limit (e.g. 2%) so >> R = deltaV/Current then find sectional area (squared mm) = R/(2*100 *57). Note 57 is for Cu or 34 for Al material and 2 for single phase (or DC) and 1.73 for three phase.

So you MUST know also system voltage to get deltaV. E.g. for single phase Vnom = 220 V and 2% it would be 4V and two-wire circuit R = 4V/(2*100A) = 20 milliOhms.

Etc. See this is when you did not give all necessary values!

Sorry...There are wrong numbers, I assumed: I = 100A and L=100m assumed, so using drop-Voltage be sure to do change for your values. And be sure is it single phase (2-wire ) or three phase circuit.

The voltage drop, in volts for 150 amps, is equal to (1.73)(12.8)(150)(600) / (circular mils for the conductor). You must calculate this then convert this to a percent yourself based on supply voltage. Generally the NEC does not contain requirements for voltage drop. It exists only as a Fine Print Note only. Fire Pumps are one exception (Article 695) where it is a requirement and there are code rules. Good engineering practice means you should try for no more than 2% drop on this feeder. If the load is 150 amps it would normally be about a 1/0 Cu conductor. Since there is about 600' to travel, if you calculate the need for 2/0 you probably have it correct. As a rule of thumb, anytime the feeder length is about equal to the supply voltage you should think about voltage drop. Examples are for 120 V at a distance of about 100 feet calculate your voltage drop. For 208V think about voltage drop at about 200 feet, for 480 since you are about 600' you are correct to ask about voltage drop. Keep in mind that you can only use the 75 Deg C conductor ratings per Article 110.14.C. Don't try to make this too hard. Copper is expensive but so are motors, and electronics which will eventually burn up. Now calculate the size you need and let me know what you get.

Outside USA (where another NEC and conductors size are in CM apply):

1. Voltage drop (deltaV) = 2 to 5% (select the value according to local rules)

of nominal/rated V phase or V line /1.73 - in three-phase! MUST be given for calculations!

Because deltaV = Current(in A) * Circuit's Resistance (in Ω) = I *R

Where R = L/(gamma *S) - L is cable length in m, gamma for Cu= 57 {m/(mm²*Ω)} and S the cable/wire/conductor area in mm² and, of course deltaV in V (volts) as a function of System Rated Voltage.

S = L*I/(gamma*deltaV) = 200m *150A/ (57 * deltaV), Select nearest greater size of the conductor

2. Check conductor ampacity (max allowable current) from your Code (Electrician's Handbook) for the ambient temperature and conditions. It must be size that at least has 150 A ampacity.

Example for V = 220/380 V system and 2% = deltaV = 4.4 V

and S minimum = 30000/(57*4.4) = 120 mm² (it is NOT a USA sizing standart!). You may check e.g. German VDE/DIN tables for I = 150 A. Most of 120 mm² conductors have over 200 A cont. current allowed. It seems this is your safe selection!!! Next is cable insulation voltage - for this example 1000 V is OK.

For American Wire Gauges (AWG sizing)- see answers from USA.

Please read the earlier threads your answer is already available in CR4. Here is one reply I gave in reply to an earlier thread and I quote below :-

"The selection of suitable cable for any electrical system is the basic job of electrical engineer and a qualifying requirement for carrying out electrical job as per any safety standards. This type of thread is often seen in CR4 and I feel either the people putting up the thread are with out basic technical knowledge or people want a simple answer to attend an interview question. The proper answer to a cable selection or bus bar selection is so elaborate that it needs a minimum of one week's refresher course. Designing any electrical distribution network and electrical switchboard panel is real technical job and not amateur's job as it involves safety of the people operating the system and equipments. Providing a simple formula or calculated figure is improper as the value depend on various parameters. A basic parameters for selection of cable and factors to be considered are listed below .

1. The cable should be rated for the correct voltage rating and size of conductor.
2. The selection of normal current rating will depend on temperature rise on normal conditions. This will depend on :-

(i) The ambient temperature of the location where the cable is laid .

(ii) The type of laying of the cable viz. underground, on cable tray, in air ,in duct etc. each condition has its own de rating factors.

(iii) The type of cable XLPE, PVC, PILC, FRLS etc and material of conductor (Copper, Aluminum). Armored, unarmored

(iv) The type of industry and load chemical, engineering, fixed load , varying load,

(v) The length of cable and depth of lying

(vi) System of back up protection and tripping time delay.

3. Short circuit rating of the conductor

The principle involved here is that the cable selected should withstand the short circuit current with out temperature rise or damage till the time the protective device like fuse ,MCB, MCCB , ACB , OCB, VCB etc. operate to disconnect the faulty system from the mains.

In India we follow the recommendation of IS 3691-1967 Part I, III, III, IV, and V Similar standards are followed in all countries which will provide the required data to select the cable."