SATEC EM920 Operation Manual - Manual (Page 119)

Chapter 5 Configuring the EM920
Configuring Recorders
EM920 Power Quality and Revenue Meter 119
adjust the thresholds according to your network conditions
before enabling triggers.
The Current Unbalance trigger has a different calculation
algorithm than the common current unbalance
measurements. Since the unbalance readings give a relation
of the maximum deviation from the average to the phase
average current, the value could produce high readings for
low currents. The Current Unbalance trigger used with the
Fault recorder indicates a relation to the CT rated current and
is not sensitive to low currents.
Configuring Digital Triggers
If you use external triggering through digital inputs, you
should individually link each digital input to the Fault recorder
(see
Configuring Digital Inputs in Chapter 5).
Fault Indication and Cross Triggering
When the Fault recorder is triggered either by the fault
detector or through digital inputs, it generates a number of
specific internal events that can be monitored through the
control setpoints to give a fault indication via relay contacts.
The following describes fault events produced by the Fault
recorder:
FAULT DETECTED - the fault detector has detected a fault
event using the device's own measurements
EXTERNAL TRIGGER - the Fault recorder has been launched
by an external trigger through one of the digital inputs
FAULT EVENT - the Fault recorder has been launched either
by its own fault detector, or by an external trigger
These events can be found under the STATIC EVENTS group
in the setpoint trigger list (STATIC in this context means that
an event is asserted all the time while its fault condition
exists).
The FAULT DETECTED event can be effectively used for cross
triggering multiple fault recorders to simultaneously record
fault data at different locations when one of the devices
detects a fault. Each device should have a setpoint
programmed to close relay contacts on the FAULT DETECTED
event, and one digital input linked to the Fault recorder.
To provide cross triggering, the triggering digital inputs of all
devices should be tied together and connected to the
normally opened relay contacts that indicate a fault. To avoid
self-triggering through its own digital input for the device that
indicates a fault, it is recommended to use a Form C relay
and to connect the digital input through the normally closed
contacts. Thus, the device that indicates a fault disconnects
its digital input before giving a fault out.