why there is a cable connecting 2 phase of transmission overhead lines?

Answer 1

Your question is not exactly clear. Transmission (high voltage eg 220,000 volts) will have 3 phases. Sometimes so that more electricity can be carried they duplicate the wires for each phase and join them together, but this still means 3 separate phases of two wires each( or 4 wires each). In distribution systems that supply transformers in the street, there can be 3 phases or two phases supplying the high voltage side of the transformer (sometimes even one in rural areas - single wire earth return systems), is this what you mean ?
If a wire is connected across phases it is a bonder or earth wire, applied to prove that the line is de-energised and safe to work on. These wires should still not be touched unless you are issued with paperwork as they can become alive at any time.
If you mean onto your house, one is the active cable, the other is the neutral(return path) cable.

Answer 2

Power is usually distributed even down to a neighborhood as three phase using three separate wires on the power poles. Sometimes there is a fourth wire for lightning protection. A residence is usually connected to two of the three phases which supplies both 220 volts for stoves and clothes dryers and 110 volts for lighting, etc. The loads in the neighborhood must be fairly balanced avoiding all homes on the same two phases. A machine shop with very large electric motors, etc. would require all three phases to supply 440 volts. Transformers (on power poles) are used to reduce very high cross-country transmission voltages to the lower voltages needed by the customer.

Answer 3

The concept is very simple: 2 phase connection is used because if one phase gets dis-connected maybe due to blowing of a fuse due to over-load, then the second phase can act as back-up for supplying the current.If you have noticed some part of a society building has electricity while the other part is out of supply mainly when there is a power cut.This is due to 2 phase connection.

Answer 4

"Phase," as used here, has two possible meanings. Multi-phase current transmission techniques use two or more conductors carrying AC whose waveforms differ by something less than 180 degrees. In three-phase transmission, the phases are separated by 120 degrees, in two-phase transmission (an obsolete technique,) it's 90 degrees.

Most residences in North America are supplied with single-phase power from a transformer whose secondary winding is center-tapped. The two 'outer' or 'hot' conductors carry currents whose phase varies by 180 degrees. Electricians often refer to these two wires as the two different 'phases,' though the power transmission technique is, in the strictest of terms, 'single phase.'

The strangeness of terminology comes from the fact that multiphase transmission was originally developed to supply the armatures of large AC motors with a rotating magnetic field, making the machines, and thus AC power transmission, a practical proposition. Such motors aren't normally needed in residences, so they use single-phase power.

I believe, however, that many European households are supplied with three-phase power nonetheless.

It certainly gets complicated.

Answer 5

no longer impartial, yet truthfully floor. it extremely is bodily grounded at each and every pylon, especially for lightening risk-free practices. commonly skill is transmitted (however no longer allotted) with 3-section AC, so there is not any impartial, only 3 warm wires.