7.8 Configure Ports – C37.118 Synchrophasor Protocol
59
Estimated Rate, Hz
is the integer number of samples per second. Rate values are different
for 50 Hz (1, 2, 5, 10, 25, 50) and 60 Hz (1, 2, 3, 4, 5, 6, 10, 12, 15, 20, 30, 60).
Cycles Used
is a calculated value based on multiplying the Estimated Rate times the Window
Length in cycles. Cycles used = 20
×
6 = 120 in Figure 7.10. Cycles Used maximum values are
determined by a maximum window length of 16 or less, depending on the value for Estimated Rate.
Maximum cycles is 400 when combining PMU-1 and PMU-2.
Data Format
allows you to set up the computation resolution, however it affects the speed of
which the 1133A processor can send data.
Nominal Frequency
– choose either 50 Hz or 60 Hz nominal
Adaptive Tuning
is used to help eliminate the possibility of losing the signal due to filter
rolloff effects by continuously adjusting the receiver center frequency. Adaptive tuning is disabled
if the error exceeds the limit. Set to
±
2
,
±
5
or
±
10 Hz.
7.8.3
Window Functions
The Model 1133A offers a wide range of of window functions, which may optimize phasor output
for individual applications. Specifically, two values, found in the setup window, combine to provide
windowing function: Estimator Algorithm and Window Length in cycles.
Window functions all serve the same purpose (as a low pass filter) and work in the same basic
way to filter higher frequency components. The main difference is the magnitude of the sideband
lobes, which are peaks in the rejection band.
Window functions are also called “weighting functions” because they work by multiplying the
input signal time record by an equal-length sequence of constants, or weighting factors.
Estimator Algorithms
include nine types, as listed below.
Raised Cosine
Hann
Hamming
Blackman
Triangular
Rectangular
Flat Top
Kaiser
Nutall 4 Term
To better evaluate the Window Functions, use the Window Function application
. Window-
Function.exe provides a graphical view of rolloff and rejection for the various curve selections,
frequency and cycles. Plots of WindowFunction.exe are illustrated in Figure 7.11; these include
two plots of Rejection and Rolloff. Window Function allows you to select Window Length and
Estimator Algorithm.
For additional information on the different window functions please see the C37.118 Synchropha-
sor Specification and the WindowFunction.exe software tool.
Digital Channels
assign the specific DSP Trigger information to be sent along with phasor
data as seen in the configuration window shown in Figure 7.12. Check boxes allow the user to select
for two values:
Normal State
tells whether the specific trigger is normally Active (checked) or Inactive
(unchecked).
Triggered State
tells whether to show the Trigger (checked) or not (unchecked).
1
Estimated rate restriction for the second PMU started.
Example: If PMU-1 was started before PMU-2, both
PMUs set to maximum estimated rate, the estimated rate for PMU-2 is restricted to half the maximum rate due to
processor limitations.
2
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