- What is the potential/voltage of the power line on a city street?
- Where does the potential/voltage of the line drop to the indoor value, e.g., 120 V in the US?
- If I need to upgrade the whole electric circuitry of a house, do I need to worry about the high voltage and if so, where does the high voltage starts to drop down to the indoor value coming into the house?
- To address the concern expressed in the comment below, I am looking to hire an electrician to upgrade the electric circuitry including the panel, meter, distributor, weather head and riser. I am wondering what are actually involved and what kind of price I would expect to be charged. The house is a single family house in Sacramento county, CA, USA.
The power delivery utility company distributes the AC power to locations away from the power generating stations using high voltages. This is done to help minimize the amount of power loss in the distribution wires and cables. The power loss is always related to the amount of current being distributed to the loads. For each doubling of the voltage used in the distribution network the amount of current for the same load is cut in half.
The voltage levels used will depend in part upon the type, location and distance that section of the power grid needs to deliver electrical power to the consumer loads. Voltages can be in the 1000s of volts.
When high voltage power distribution reaches a residential neighborhood or a business center transformers are used to step the high voltage down to the voltages used in the homes and businesses. Pictures of some typical power transformers are shown below. Typically these transformers are owned and maintained by the power delivery utility company. When you would need service at a particular current level the power company will deploy the proper transformers and then provide a power line connection from the transformer to the electrical usage meter which would be on or adjacent to the home or business.
In most places in the US, residential power comes into the meter at 240V/120V - three conductors, 2 hot and 1 neutral. The hots are 240V apart (there are some situations where they may 208V or some other value, but 240V is most common) and the hots are each 120V from neutral.
Typically there will be a transformer either on a pole or in an underground vault or on a street corner which transforms power from some higher voltage to 240V. But you don't need to worry about that. Your utility provides 240V, and how it gets there is up to them. In some large buildings, that transformer may even be inside the building, but you, as the ordinary consumer, only get 240V/120V.
If you have to upgrade the entire electrical system of a house, the safest thing to do is often to have the utility pull the meter (or lock it out in some fashion). That will make your main electrical panel "dead" so that it can be replaced safely. Once you have a new main panel with a shutoff of some sort (either a main breaker or a separate shutoff switch) then any additional work can be done with the meter connected and power "live" to the house.
What is the potential/voltage of the power line on a city street?
Usually distribution 2300, 4160, 12.47k, or 13.8k, but can be higher. Transmission would be higher and can be run around city streets, but would generally go to a substation.
Where does the potential/voltage of the line drop to the indoor value, e.g., 110 V in the US?
As shown by Michael, there are transformers that convert the higher voltage to lower voltage to your house. The voltage to a residence is 240V, but between two lines. The 120 (110) that you refer to is between one line and neutral.
If I need to upgrade the whole electric circuitry of a house, do I need to worry about the high voltage and if so, where does the high voltage starts to drop down to the indoor value coming into the house?
The lower 240V lines will start at the transformer. This is either on the pole, or on a padmount transformer. In a residence, the voltage would only be 240V.
If you are modifying or updating in your residence, you'll either use 120V (single pole), or 240V (double pole). You would choose based on the need of the line. Generally, you'll always use a single unless it's a high load device such as an electric oven or air conditioner. Devices are built for a voltage and you'll just need to supply what they need. When in doubt, you can ask at a hardware store, or get help from an electrician.