The Remote Measurement of Phase Angle

Abstract

In the distribution of electricity, it is necessary to
link the outputs of substations, which may be many miles
apart. In order to prevent an excessive surge of current in
the connecting link, the connection between a pair of substations
should not be made until the phase angle between their voltages
is small, There has been, for many years, a need for the
measurement of this phase angle, with the results displayed in
the distribution Control Room, A direct measurement may be
significantly in error, due to the time delay in transmission of
the measurement signals from substation to Control Room. This
error is avoided inthe measurement system described. A test
signal, superimposed on the phase measurement signal, repetitively
measures the transmission path delay, and applies a suitable
correction to the phase angle indication, The system may be used
either with pilot lines or a radio link between substations and
Control Room, An advantage is that the route of a pilot line may
be changed without affecting the accuracy, thus allowing the use of
public telephone lines, if necessary.

A pilot line system has been installed in the Birmingham
Area of the Midlands Electricity Board: the maximum length of
pilot line used is 12 miles, and the measurement error does not
exceed a small fraction of one degree. The equipment has been
designed to possess a high degree of reliability.

Although primarily designed for operation at 50 Hz, the
system could readily be adapted for use at higher frequencies.

Date of Award	1972
Original language	English