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MONITORING THE HEALTH

OF YOUR ELECTRIC POWER GRID Precision PC-Based 60-Hz Frequency Counter
by Doug Criner

Start ý Frequency and Time Errors ý A Struggling Grid ý Only Three Parts ý Sources and PDF

FREQUENCY AND TIME ERRORS

There are two system errors that need to be minimized, the frequency error and time error. The frequency error is just the instantaneous deviation from 60 Hz. The time error, the integral part of the frequency error, is how late or early electric clocks are running relative to true time. System operators (and power system computers) are continually adjusting the system frequency to minimize these two errors.

To monitor the system frequency, you must be able to measure it within 0.01 Hz. If, for example, the system frequency suddenly drops and then recovers after several minutes, it often means that a large power plant has tripped off-line and the load is being picked up by the other generators. The trip may have occurred in New York, but you might detect the frequency change in Chicago.

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