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Commonly used terms in the Electrical industry.
power fault arc
an arc through soil extending from a power lines's lightning ground to a buried, grounded structure. These may form when lightning strikes an energized overhead electric power line.
pull-in torque
the amount of torque needed to change a synchronous motor's operation from induction to synchronous when self-started.
pull-out torque
the maximum value of torque that an AC motor can deliver. An induction motor operating at the pull-out torque will operate at maximum slip, and loading it beyond the pull-out torque will cause the motor to stall. Synchronous motors remain at synchronous speed up to the pull-out torque. Exceeding the pull-out torque for a synchronous machine will lead to pole slipping and destruction of the machine.
pull-up torque
the minimum torque generated by an AC motor as the rotor accelerates from rest to the speed of breakdown torque. For an induction motor, this value usually is less than the locked-rotor torque, and thus establishes the maximum load that can be started.
pulse
a sudden change of an electrical value of short duration with a quick return to the original value. A pulse injects a short sharp burst of energy into a system and is usually quantified by its area rather than its amplitude or its duration. In the limit as the amplitude tends to infinity and the duration to zero, it approaches the Dirac delta function whose Laplace transform is unity.
regulation
the change in voltage from no-load to full-load expressed as a percentage of full-load voltage.
regulator
a controller designed to maintain the state of the controlled variable at a constant value, despite fluctuations of the load.
repulsion-induction motor
a single-phase motor designed to start as a repulsion motor, then run as an induction motor. The rotor has a DC-type winding with brushes shorted together, in addition to the normal squirrel cage winding. Although it is an expensive design, it provides excellent starting torque with low starting current (similar to a universal motor) and relatively constant speed under load.
right hand circular polarization
the state of an electromagnetic wave in which the electric field vector rotates clockwise when viewed in the direction of propagation of the wave.
sine-squared pulse
pulse string made from a standard sinewave with an added DC component equal to one-half of the peak-topeak value of the sine wave. The pulse string is, therefore, always positive in value.
single line to ground fault
a fault on a three phase power line in which one conductor has become connected to ground.
single phase to ground fault
See
single line to ground fault
speed regulation
the variation of the output speed of an electromechanical device as the load on the shaft is increased from zero to some specified fraction of the full load or rated load. Usually expressed as a percentage of the no-load speed. A large speed regulation is most often considered as a bad regulation from a control point of view.
static VAR regulator
also called a static VAR compensator. A nonrotating electrical device designed to adjust the reactive power flow of an AC power system. It typically consists of a reactive load (either inductive or capacitive) and a series electronic switch (thyristor) that controls the reactive power.
station insulator
refers to a large-sized insulator used in substations.
strain insulator
an insulator which forms an insulated tensile link between two conductors in overhead line work.
sulfur hexaflouride
a heavy, highly-electronegative gas used as a high-voltage, self-healing insulation.
symmetrical fault
another term for a three-phase fault, a fault in which all three conductors of a three-phase power line are short-circuited together. System faults are symmetrical and can be analyzed by using single phase circuit.
symmetrical fault current
the total current flowing to a fault less the DC offset current. In many cases, fault current calculations are expressed in terms of symmetrical amps.
tap changing under load (TCUL)
a type of transformer in which the output voltage can be adjusted while the load is connected to the transformer. The voltage is adjusted by changing the turns ratio of the primary and secondary coils. That, in turn, is accomplished by bringing out connections (taps) at several points on the coil. Changing from one tap to another either adds or subtracts turns from the coil and raises or lowers the voltage, respectively.