2/0 if copper is used; 4/0 if aluminum is used. The neutral and ground are usually smaller.
2/0 is only rated for 185 amps.
3/0 copper is rated for 210 amps, 250 MCM is rated at 215 amps if aluminum is used.
From your answer I am picturing a 400 amp service that is then split into 2 - 200 amp meters and subsequent breaker panels. In residential installations carrying a potential 400 amps you need 400 MCM conductors (MCM is sometimes called kcmils). For 200 amps you will need 2/0 (called "2 ought") conductors. In commercial and industrial installations you will need 500 MCM conductors for 400 amps and 3/0 (called "3 ought") conductors for 200 amps.
There are other requirements for this installation. This is not a job for a novice. If you have not passed a certification exam showing you know how to use the code correctly, do not make this installation.
A 300 MCM copper conductor with an insulation factor of 90 degrees C is rated at 320 amps. That said after the de-rating of the feeder cable because of electrical code regulations the next size up is 350 MCM.A 350 MCM copper conductor with an insulation factor of 90 degrees C is rated at 350 amps.
Nec 310.16
#3 thhn
A three-phase meter can be used for single phase while the reverse is not the case.
is 3 phase Meter electicity to for the measurement of elektricity 3 phase.
Phasing, or the number of phases in an electrical system has nothing to do with the voltage. A single phase and three phase supply could have a voltage supply of any given voltage from virtually 0 to infinity. Most single phase power supplies in the US are 120/208-240 volt. Three phase power supplies are typically 120/208 to 277/480 volt.
The reverse running of a three phase meter is possible when one of the meter's two potential coils fails. This is a problem found typically on a Delta service. A three phase meter in this condition is damaged and will report lower energy use than actual.
A current transformer has to have the same ratio as the meter that it drives. Full scale deflection on the meter is 5 amps which equals the maximum allowed current on the phase that it is reading. A different ratio on the CT to meter would show an erroneous reading on the meter depending on the ratio of the connected CT. To keep costs down the meter is common to all three phases and is read by connecting the meter to the phase CT through a three position switch.
A three-phase meter can be used for single phase while the reverse is not the case.
One feeder will do the job. The definition of a feeder in the electrical trade is a set of conductors that supply a source to a load. The sizing of the feeders will depend on what the load current is. The wire count of the feeder will be dependant upon whether the load is single phase or three phase.
is 3 phase Meter electicity to for the measurement of elektricity 3 phase.
No. For three phase, you need a minimum of a two element meter.
Phasing, or the number of phases in an electrical system has nothing to do with the voltage. A single phase and three phase supply could have a voltage supply of any given voltage from virtually 0 to infinity. Most single phase power supplies in the US are 120/208-240 volt. Three phase power supplies are typically 120/208 to 277/480 volt.
1.2 meter
Your question is rather confusing, as you do not specify what you mean by 'panels'. Your reference to a 'two-phase' supply is also confusing because two-phase supplies are an archaic precursor to 'three-phase' supplies, and it's unlikely you'll come across any two-phase supplies anywhere these days!
A 3-phase meter measures the sum of the power in the three phases, so if power is drawn on one phase only it will still be correctly measured.
As with any IDMT relay the higher the fault current the quicker the trip time.
The reverse running of a three phase meter is possible when one of the meter's two potential coils fails. This is a problem found typically on a Delta service. A three phase meter in this condition is damaged and will report lower energy use than actual.
yes they must be protected individually
there isnt a high leg in a three phase 480v panel only on 240v panels