Schweitzer Engineering Laboratories SEL-421-4, Instruction Manual

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13.19
Date Code 20171006 Instruction Manual SEL-400 Series Relays
SEL
OGIC
Control Equation Programming
SEL
OGIC
Control Equation Elements
In protection freeform programming, the relay evaluates the timer at execution of
the timer Input SEL
OGIC
control equation (PCT nn IN). The relay loads the Pickup
Time (PCT nn PU) and Dropout Time (PCT nn DO) into the timer when the relay
observes the appropriate edge in the input. If you enter a math expression for
Pickup Time or Dropout Time, the relay uses the value calculated before the
Input SEL
OGIC
control equation. If your Pickup Time or Dropout Time equation
is below the Input equation (has a higher expression line number), the relay will
use the value calculated on the previous SEL
OGIC
control equation execution
interval. Because the relay calculates the last value for pickup or dropout in this
manner, we recommend for most applications that you enter the Pickup Time,
Dropout Time, and Input statements together in the order shown in
Example 13.7 .
You can view the status of the protection conditioning timer output Relay Word
bits using the
TAR PCT nn Q command, where nn is the number of the protection
conditioning timer. You can also view the status of these timer elements through
the relay front-panel LCD display by selecting
RELAY ELEMENTS
from the Main
Menu and scrolling through the rows of Relay Word bits.
Sequencing Timers
NOTE:
Times for protection timers
must not exceed 2,000,000 cycles for
proper operation.
Sequencing timers are useful for sequencing operation. There are two main dif-
ferences between sequencing timers and conditioning timers. First, sequencing
timers integrate pulses of the input to count up a total time. Second, the elapsed
time a sequencing timer counts is visible; you can use this time in other SEL
OGIC
control equation programming or make this time visible through one of the relay
communications protocol interfaces. Sequencing timers are available in the pro-
tection freeform area and automation freeform area as shown in
Table 13.11 .
Sequencing timers have three input parameters and two outputs listed in Table 13.12 .
Example 13.7 Conditioning Timer Programming and Operation (Continued)
Figure 13.7 Conditioning Timer Timing Diagram for Example 13.7
IN101
PSV29
Dropout Pickup
Dropout Time
Pickup
Time
5.375 Cycles
6.0 Cycles
Table 13.11 Sequencing Timer Quantities
Type Typical Quantity Name Range
Protection freeform sequencing timers 32 PST01–PST32
Automation freeform sequencing timers 32 AST01–AST32