Sel SEL-421 - Latch Bits; Latch Bit Quantities; Latch Bit Parameters; Protection Latch Bits

R.3.15
Date Code 20111215 Reference Manual SEL-421 Relay
SELOGIC Control Equation Programming
SELOGIC Control Equation Elements
ASV011 := AMV010 > 13 # Set if greater than 13 kV
# C-phase
AMV010 := VCFIM/1000 # VC in kV
ASV012 := AMV010 > 13 # Set if greater than 13 kV
# Combine phase results
ASV013 := ASV010 OR ASV011 OR ASV012
Latch Bits
Latch bits are nonvolatile storage locations for Boolean information. Latch
bits are in several settings areas of the relay, as shown in Table 3.11. Latch bits
have two input parameters, Reset and Set, and one Latched Value, as shown in
Tab le 3.12.
Latch bits provide nonvolatile storage of binary information. A latch can have
the value of logical 0 or logical 1. Latch bits also retain their state through
changes in the active protection settings group. Because storage of latch bits is
in nonvolatile memory, the state of latch bits remains unchanged indefinitely,
even when power is lost to the relay.
As with logic latches used in digital electronics, each latch bit has a Set input
and a Reset input. The relay evaluates the latch bit value at the end of each
logic processing interval using the values for Set and Reset calculated during
the processing interval. Latch bits are reset dominant. If the Set and Reset
inputs are both asserted, the relay will reset the latch.
Latch bits are available in two different programming areas of the SEL-421.
First, there are 32 latch bits, PLT01–PLT32, that are associated with protection
settings. Second, there are 32 latch bits, ALT01–ALT32, available in
automation free-form programming.
Protection Latch Bits
Program the 32 latch bits, PLT01–PLT32, in the protection free-form
SEL
OGIC control equation programming area. There is a separate protection
free-form SEL
OGIC control equation programming area associated with each
protection settings group. The latches in protection can have separate
programming for Set and Reset in each protection settings group. While each
Table 3.11 Latch Bit Quantities
Type Quantity Name Range
Protection free-form latch bits 32 PLT01–PLT32
Automation latch bits 32 ALT01–ALT32
Tabl e 3 . 12 Lat ch Bi t Pa ra met e rs
Type Item Description Setting
Name
Examples
Input Reset Reset latch when on Boolean SELOGIC
control equation
PLT01R
ALT01R
Input Set Set latch when on Boolean SEL
OGIC
control equation
PLT01S
ALT01S
Output Latched Value Latched Value of 0 or 1 Value for use in
Boolean SEL
OGIC
control equations
PLT01
ALT24