Dictionary of Electrical Engineering

Commonly used terms in the Electrical industry.

surge
a short-duration (microsecond to millisecond) increase in power line voltage.
See spike
surge arrestor
a device that limits overvoltages by conducting large currents in response to an overvoltage. Surge arrestors are typically connected line to ground in transmission and primary distribution systems. They can be employed in a variety of connections in secondary distribution, and can be necessary in communications, sensing, and control circuits.
surge impedance
the ratio of voltage to current on that line for a high speed wave propagating down the line. The surge impedance of a line is a constant which depends on the line geometry and conductor characteristics. On power transmission lines, these waves are typically generated by lightning strokes, circuit breaker switching, etc.
See characteristic impedance
surge impedance loading (SIL)
of a transmission line, the characteristic impedance with resistance set to zero (resistance is assumed small compared to reactance). The power that flows in a lossless transmission line terminated in a resistive load equal to the line's surge impedance is denoted as the surge impedance loading of the line.
surge response voltage
the voltage that appears at the output terminals of surge protection equipment and is seen by loads connected to that device both during and after a surge condition.
surge tank
an empty vessel located at the top of the penstock. It is used to store water surge when the turbine valve is suddenly closed.
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