• input magnitude selection
• input magnitude processing
• threshold comparator
• two block signal check
• time delay characteristics
• output processing.
The inputs for the function are the following:
• operating mode selections
• setting parameters
• digital inputs and logic signals
• measured and pre-processed power magnitudes.
The function outputs the START, TRIP and BLOCKED signals which can be used for direct I/O
controlling and user logic programming. The function generates general time-stamped ON/OFF events
to the common event buffer from each of the three (3) output signals. In the instant operating mode the
function outputs START and TRIP events simultaneously with an equivalent time stamp. The time stamp
resolution is 1 ms. The function also provides a resettable cumulative counter for the START, TRIP and
BLOCKED events.
The following figure presents a simplified function block diagram of the underpower function.
Figure. 5.3.17 - 145. Simplified function block diagram of the P< function.
Measured input
The function block uses three-phase active power values. A -20 ms averaged value of the selected
magnitude is used for pre-fault data registering. If the protection relay has more than one CT module,
the parameter
Measured side determines which current measurement is used for the power
measurement.
Table. 5.3.17 - 145. Measurement inputs of the P< function.
Signal
Description
Time base
3PH Active power (P)
Total three-phase active power
5ms
A
AQ
Q-M215
-M215
Instruction manual
Version: 2.04
207