SATEC PM180 Operation Manual - Manual (Page 79)

‎Chapter 7 Programming the PM180 Using Control Setpoints
PM180 Substation Automation Unit 77
Using Logical Expressions
Logical operators OR/AND are treated in a simplified manner. They have no specific
priority or precedence rules.
Any trigger condition bound to the logical expression by the OR operator and
evaluated as “true” overrides any preceding condition evaluated as “false”. Similarly,
any trigger condition evaluated as “false” and bound by the AND operator overrides
any condition evaluated before it as “true”.
To avoid confusion, it is recommended not to alternate different logical operators in
one expression. Instead, bring all conditions that use the same logical operator
together at one side of the expression, and the others - at the opposite side.
To explicitly override all other conditions with the critical trigger, put it at the end of
the expression using the OR operator if you want the setpoint to be operated anyway
when the trigger condition is asserted, and with the AND operator, if the setpoint
should not be operated while the critical trigger is not asserted.
Using Numeric Triggers
For numeric (analog) triggers, a setpoint allows you to specify two thresholds for
each trigger to provide hysteresis (dead band) for setpoint operations. The Operate
Limit defines the operating threshold, and the second Release Limit defines the
release threshold for the trigger. The trigger thresholds are always specified in
primary units.
If you use relational operators
as “<=” (under or equal) or “>=” (over or equal), always
specify a correct Release Limit for the trigger. If you do not want to use hysteresis,
set the Release Limit to the same as the Operate Limit.
With the “Delta” operator, the setpoint is operated when the absolute value of the difference
between the last reported value and the current value exceeds the specified threshold
Using Binary Triggers
Binary (digital) triggers, as digital inputs, relays, or internal static and pulsed events,
are tested for ON (closed/set) or OFF (open/cleared) status. Min/Max log parameters
can be tested for a NEW event that is asserted when a new minimum or maximum
value is recorded for the parameter since the last time it was checked.
The binary events are divided into two types: static events and pulsed events. Static
events are level-sensitive events. A static event is asserted all the time while the
corresponding condition exists. Examples are digital inputs, relays and internal static
events generated by the device diagnostics, metering procedures, and Power Quality
and Fault recorders.
Pulsed events are edge-sensitive events with auto-reset. A pulsed event is generated
for a trigger only once when a positive transition edge is detected on the trigger input.
The examples of pulsed events are pulse inputs (transition pulses on the digital
inputs), internal pulsed events (energy pulses and time interval pulses), and events
generated by the interval timers. The logical controller automatically clears pulsed
events at the end of each scan, so that triggers that used pulsed events are
prevented from being triggered by the same event once again.
Using Event Flags and Virtual Relays
The PM180 has 16 common binary flags, called event flags, which can be
individually set, cleared and tested through setpoints or remotely.
Event flags can be used in different applications, for example, to transfer events
between setpoints in order to expand a logical expression or a list of actions that
have to be done for a specific event, or to remotely trigger setpoint actions from the
SCADA system or from a PLC.
In the same way, any of the 32 device relays that is not actually present in your
device (it is called a virtual relay) can be used to transfer events from one setpoint to
others, or to indicate events to the setpoints from the external system.
Using Interval Timers
The PM180 has 16 interval timers that are commonly used for periodic recording of
interval data at the time of the fault or in the presence of other events detected by
setpoints. Some of the timers are factory preset for use with the Power Quality and