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Section 9. Events and Diagnostics
operate for both the trip function and the alarm
function)
• The Force Trigger button at the HMI is pressed
by a user
Consequently, waveforms can be captured during
power disturbances or other power system events.
The waveforms, when combined with the sequence
of events log, provides a unique analysis tool to
identify system phenomenon.
The capture duration is 1.0 second on 60 Hz systems
and 1.2 seconds on 50 Hz systems. Up to 64 digital
samples are recorded per cycle. All channels for
the entire system are time synchronized to within
5
s of each other.
µ
Up to 1000 system-wide waveforms can be held in
memory. Therefore, the maximum number of WFC
events held at any time is dependent on the num-
ber of Messengers in the system; there is one
Messenger for each circuit breaker in the
system. The number of WFC events that can be
stored, can be calculated as the integer quotient
of 1000/ n , where n is the total number of
Messengers in the system. The file data are stored
according to the format defined by COMTRADE
(IEEE Std. C37-111-1999).
Waveform captures are viewed using the HMI
screen. To see the waveform data, highlight the
event of interest on the SOE list and then click the
Waveform button.
The waveforms in Figure 9.3 were captured from
Figure 9.4
Instantaneous Values
50
and associated with an overcurrent event. The date
and time of the waveform capture are displayed
at the top of the screen. While the time resolution
is displayed to the nearest microsecond, the system
clock resolution is equal to or better than five
Data associated with the cursors on the analog
waveform chart are displayed below the date and
time. To the right of the date and time are the
slide-bar controls for the moveable cursors and the
time data for the cursor relative to the start of the
WFC event. The slide bars can be used to control
the moveable cursor positions or the actual cursor
on the analog waveform chart can be clicked and
dragged to another location. The color-highlighted
box beneath the slide control shows the length of
time from the start of the record to the cursor. The
color highlights correspond to the blue and green
cursors on the analog waveform chart. The time
difference,
t , between the blue and green cursors
∆
is displayed in the yellow highlighted box. The red
cursor on the analog waveform chart remains
fixed at the time of the event trigger.
The instantaneous values from the analog wave-
form chart are listed in the table to the left of the
analog waveforms. This is a dynamic table. The
color-highlighted values correspond to the instan-
taneous values at the blue and green cursor locations.
These are not rms values, but the instantaneous
values at those points on the analog waveform, as
shown in Figure 9.4. The yellow-highlighted value is
the difference between the blue and green values.
You can move the blue and green cursors to different
Figure 9.5
Waveform Configuration Screen
s.
µ
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