Power Transmission Tower

Fundamental Concepts of Electrical Power Transmission

Voltage, current, power, and electrical energy are some of the most frequently used terms when discussing transmission line characteristics.

Voltage: The voltage of a transmission line determines the line’s ability to transmit electricity. This electric force, or electric potential, is measured in volts (V), or more typically in kilovolts (kV);
1 kV = 1,000 V.

Current: The current through a transmission line is a measure of the amount of electricity that is
moving through a conductor. Current flow through a conductor is measured in amperes (amps).

Power: Power flowing through a power station is measured in watts (W), or more typically
megawatts (MW), where 1 MW = 1,000,000 W. Power in an alternating-current system depends on the system voltage and current flow and is comprised of two components: real power and reactive power. If a small circuit has no reactive components (like these found in motors or computer power supplies) and is purely resistive (like those of an incandescent light bulb or toaster), then all power transferred through the circuit is real power (i.e., pure MW). Once a motor, for example, is added to a circuit, a reactive power component (measured in megaVARs [MVAR], for megavolt-amps reactive) is introduced along with the real power component. Both aspects of complex power are present and important in transmission system operations, and the respective amount of each is related to the line’s power factor. Unfortunately, real power is often used synonymously for complex power. This simplification neglects the effects that reactive power can have on system stability and system operation.

Electrical energy: Energy is a measure of the ability to do work. The energy required by a load or provided by a generator is the product of power and time, and is usually expressed in kilowatt hours (kWh).

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