Electrical question?

On power lines ran from the substation to different streets. If there are three phases  and one goes out. How come the other two keep operating? I notice in a power outage. Some streets still have power.

5 Answers

  • Jim
    Lv 7
    4 weeks ago

    Residential only has single-phase power

    BUT it has 2 sides to the 240 voltage, 120 + 120

    So theoretically half the stuff in your home could still work.

  • 4 weeks ago

    Residential streets do not have three phase power, only 2 phase power. Industrial areas have three phase power.

    Residential areas are divided into zones with fuses in the lines which blow when overloaded cutting off power to the zone.

  • 4 weeks ago

    Because some area could use one phase that still working  out of 3 phase during partial black out period ( like blowing the street high voltage fuse). 

  • 1 month ago

    It depends on the exact equipment configuration.

    eg. In the UK, residential power is often three phase at the street (230 or 240V phase to neutral), with the branches to each house taken from sequential phases to average out the overall load.

    Each main cable to a street or area would be fed from a separate circuit breaker from the substation supplying that area, so a fault could disconnect power from just part of the overall area served by one substation.

    Substations seem to be something like half a mile to a mile apart around here, depending on the housing density.

    Bigger industrial or retail sites etc. generally have their own substations.

    For info: In the UK, an electrical "substation" is a large transformer system in its own enclosure.Local ones are at the last stage in the voltage reduction, providing the industrial or domestic supply voltage from a higher voltage input - the equivalent of a pole transformer in the US, but covering a larger area.

    Something like this:


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  • qrk
    Lv 7
    1 month ago

    For residential power, they use two of the phase lines for single phase take-off for the local transformer. In North America the transformer output is 2-phase (240V center-tapped) which gives you two 120V feeds out of phase. Combining those will give 240V for your high power appliances (stove, water heater, AC).

    You have a 1/3 chance that you'll have power if you loose a phase.

    In a commercial setting where 3-phase is used, if you loose one phase, all sorts of bad things happen. You basically get a brownout on your 120V feeds and 3-phase equipment won't operate properly.

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