In order to power buildings, generators, and substations, electricity needs to be transmitted from one location to another. These electrical power transmissions have to move a considerable amount of electricity around from a source, such as a power plant, to a substation where it can be harnessed, transformed, and pushed through to consumers and other sites.
Primary Transmission of Power
When electricity is created in a power station, the energy generated usually falls between 11kV and 33kV. This is quite a low output, so before transmitting the electricity elsewhere, it’s sent to a transformer. This transformer allows the voltage to increase significantly – anywhere from 100kV to 700kV – which makes it suitable for long-range transmission. If electricity needs to travel farther, a greater voltage is required.
Electrical power needs to be transformed into a higher voltage level due to the I2r degradation that stems from resistance. I2r is the formula used to determine the electrical efficiency of a current. As a current of electricity flows through something, it faces resistance. I2r outlines this power loss by looking at the flow of current (I) through a resistance (R) that requires power consumption that is twice the existing power.
This is the primary transmission stage of power transfer, and it outlines a movement of large quantities of electricity from an initial source (power plant) to a substation through electrical wires. Sometimes, underground cabling is used but it does cost a lot more than overhead wires, so it is usually only suitable for short distances.
Secondary Transmission of Power
Once electricity has been channeled to a substation, the voltage must be brought back to a standard voltage of 33kV to 66kV. From here, it is carried through transmission lines to other electrical substations to serve cities, urban developments, and large infrastructure.
Once the electricity reaches the second substation, the voltage is once again dropped to around 11kV. At this stage, the electricity is ready to be distributed to consumers to power their properties.
The Main Components of a Transmission Line
As touched on above, most transmission lines for electricity are overhead systems because they are much more cost-effective when compared to underground cabling. Below is a breakdown of the main components of an overhead transmission line:
- Conductors: There are three conductors for a single circuit and six for a double circuit. Conductors must be a specific size which varies depending on the capacity of the line.
- Transformers: Transformers are used to step voltage up or down depending on where they lie in the power transfer. Either way, they are used to adjust the voltage for optimal efficiency.
- Line insulators: These are used to support line conductors and isolate them from support towers.
- Support towers: Support towers are used to suspend line conductors in the air.
- Protective devices: Various protective devices are used to maintain the safe operation of power lines. Examples of these devices include circuit breakers, ground wires and relays.
- Voltage regulators: As the name suggests, these devices ensure that voltage stays within reasonable limits when electricity is received.