PART 3

The measure of the opposition that a circuit presents to a current when a voltage is applied. Impedance extends the concept of resistance to AC circuits, and possesses both magnitude and phase, unlike resistance, which has only magnitude.

The condition in which there is a sudden load loss in the system which causes the generating equipment to be over-frequency. A load rejection test confirms that the system can withstand a sudden loss of load and return to normal operating conditions using its governor. Load banks are normally used for these tests as part of the commissioning process for electrical power systems.

Electric polarization in a substance (especially certain crystals) resulting from the application of mechanical stress (pressure).

Electric polarization in a substance (especially certain crystals) resulting from the application of mechanical stress (pressure).

Occurs when changing current in one coil induces voltage in a second coil.

A collective term applied to the positive (+) and negative ( - ) ends of a magnet or electrical mechanism such as a coil or battery.

(Ω) A unit of measure of resistance. One ohm is equivilant to the resistance in a circuit transmitting a current of one ampere when subjected to a potential difference of one volt.

The rate at which electrical energy is transferred by an electric circuit. Measured in Watts.

The mathematical equation that explains the relationship between current, voltage, and resistance (V=IR).

The ratio of the actual electrical power dissipated by an AC circuit to the product of the r.m.s. values of current and voltage. The difference between the two is caused by reactance in the circuit and represents power that does no useful work.