-- The Eastern Interconnection frequency governing
characteristic, sometimes called Beta, has been tracked by one of
the authors for a period of more than 15 years.
While there are
some errors inherent to the process followed, we believe that the
errors do not obscure the overall trend.
We have found that Beta
has been declining and has reached a level of approximately 25
This has important implications in system behavior,
particularly in situations involving islanding.
need to reflect this observed reduction in governing response.
Combined frequency governing characteristic, Beta, Frequency
Response, Generation Governing, Load Governing.
The parameter Beta is the constant of proportionality
between the change in generation or load and the resulting
We will use Beta beginning with an upper
case B to represent Beta for the entire interconnection.
same term beginning with a lower case letter would be the
same parameter for some part of the interconnection, such as a
The upper and lower case Greek letters could
well be used, but we have not done so in this paper.
Tenths of Hz have been used in this context in the past;
however in our large interconnection we routinely speak now
of frequency deviations in milliHertz abbreviated as mHz.
We also suggest that milli is a preferred engineering unit
prefix, and tenths, or “deci,” is not.
The use of milliHertz
results in convenient numbers.
For example, for typical
incident with a loss of 1000 MW and a decline of 31.6 mHz,
the resulting Beta is 31.6 MW/mHz.
For all these reasons, we
will use mHz for frequency changes and MW/mHz as the unit
Dates and times of observed events are the trigger times of
various PMUs and disturbance recorders which are
synchronized using GPS clocks.
No offsets have been applied
to the UTC time scale obtained.
The term we have used for
this Time Zone is “Zulu,” represented by the letter “Z” which
is the preferred term
We believe power system time sequence
data should be recorded using Zulu Time Zone.
James Ingleson is with RLC Engineering, 402 Bond Road, Altamont, NY
12009 USA. (e-mail: firstname.lastname@example.org)
Eric Allen is with NERC, 116-390 Village Blvd., Princeton, NJ 08540
USA. (e-mail: email@example.com)
D. Eastern Interconnection
The Eastern Interconnection is the power system
interconnection that includes the areas of United States and
Canada which are east of the Rocky Mountains.
The state of
Texas and province of Quebec are not part of this
In this work we will speak of
the Eastern Interconnection as simply “the interconnection.”
n the average of somewhat more often than once per day,
there occurs a significant decline in frequency on the
interconnection because of the sudden loss of a single
generating unit or a group of units.
Within several seconds,
the power system arrives at a new lower frequency, and a new
equilibrium state is found.