GridSense Line IQ LIQ60, Руководство пользователя, Страница: 15 / 39

000-2166 Rev 3.0 Franklin Grid Solutions LLC
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2.4.3 Operation Modes
For the majority of time that the LIQ-60 is installed it will simply be monitoring and storing its input
values. There will be minimal radio communications during this time, restricted to periodic status requests
from an LIQ-Gateway, unless initiated by an external device such as a Laptop PC using LIQ- LocalLink.
Should an event such as a power outage occur, there will be increased radio communications when the
event is detected.
Normal Operation
During normal operation the LIQ-60 continually samples voltage, current and temperatures.
The raw sample points (measured at 600Hz for voltage and current) are stored in a circular buffer, so
that once an event is detected, the LIQ-60 can
“look backwards in time” and recover pre-fault information.
RMS voltage and current readings are calculated from the raw sample points. These RMS values, which
are updated at the supply frequency (50Hz or 60Hz) are used as inputs to the event detection algorithm.
If load logging is enabled, the current readings are averaged and stored at the end of each Log Average
period.
The voltage and current readings are processed by Fast Filters to provide input signals for the event
detection algorithm, in addition to the per-cycle va lu e s .
The outputs of the voltage and current Fast Filters are further filtered by non-linear Slow Filters. These
filters have a decay time constant of approximately 10 days, but a much faster attack time constant. The
output of the Slow Filters provides a good representation of the normal conductor load profile. The Slow
Filter outputs also provide inputs to the event detection a l g o r i t h m .
Average conductor and ambient temperatures, as well as phase angle and power factor data are stored
at the Log Average interval.
Event Classification
LIQ-60s incorporate a sophisticated event detection algorithm which analyses voltage and current data
and reports the following activity occurring on the conductor:
•
Fault Path (FP)
– a high current event.
•
Short Interruption (SI)
– a brief (less than one minute) loss of power on the conductor.
•
Long Interruption (LI)
– a loss of power on the conductor for at least one minute.
•
Power Return (PR)
– return of power after a Long Interruption (LI).
Some of these activities can occur together.
For example, an LIQ-60 mounted on a conductor upstream (i.e. on the generator side) of a fault which
results in a permanent outage will report a FP-LI event, whereas an LIQ-60 mounted downstream (i.e. on
the load side) of that fault will report a LI event only, because it will not see the fault current. After power
is restored, both LIQ-60s in this example will report a PR event.
A second common example is where the system protection (recloser) operates and clears the fault. In
this case, the LIQ-60 upstream of the fault will report a FP-SI event, whereas an LIQ-60 downstream of
the fault will report a SI only. Since power has only been briefly interrupted, a PR event will not occur.