I.5
Date Code 20080213 Instruction Manual SEL-351A Relay
Using the SEL-251 and SEL-267 Relay Settings in the SEL-351A Relay
Other Differences Between the SEL-351A and the SEL-251-3 and SEL-267-5 Relays
Other Differences Between the SEL-351A and the
SEL-251-3 and SEL-267-5 Relays
Protective Functions
Compared to both the SEL-251-3 and SEL-267-5 relays, the SEL-351A has:
➤ More overcurrent elements, and more torque-control options
➤ Over-/underfrequency elements
➤ Ten time-overcurrent curve choices versus four
➤ Neutral channel (IN) overcurrent and time-overcurrent
functions
➤ Individual phase time-overcurrent elements
➤ Ability to handle 50 or 60 Hz systems abc or acb phase
rotation, and wye- or delta-connected PTs, with simple settings
changes (whereas specific models of the SEL-251/SEL-267
relays have to be ordered for these applications).
The SEL-351A uses the letter “G” to refer to residual current and the letter
“N” to refer to the measured IN channel input current. The SEL-251-3 and
SEL-267-5 relays use “N” to refer to the residual current and have no IN
channel.
The SEL-351A does not have the built-in “high-side blown fuse detection”
setting that the SEL-251-3 has, but this feature is easy to implement in
SEL
OGIC control equations using the extra over- and undervoltage elements
that are available.
Compared to the SEL-251-3, the SEL-351A has:
➤ More overvoltage and undervoltage elements
➤ Directional elements
NOTE: The SEL-351A-1 does not
include directional elements.
Compared to the SEL-267-5, the SEL-351A has:
➤ Overvoltage and undervoltage elements
➤ Negative-sequence overcurrent elements
➤ Six settings groups
Reclosing Relay (79)
The SEL-351A reclosing relay is more programmable than the reclosing relay
in the SEL-200 series relays. It features a synchronism check element, plus
drive-to-last shot and skip shot settings.
SELOGIC Control
Equations
The SEL-351A has Advanced SELOGIC control equations, while the
SEL-251- 3 has SEL
OGIC control equations, and the SEL-267-5 has Mask
Relay Logic.
There are 16 Latch Bits and timers in the SEL-351A.
Optoisolated inputs to the SEL-351A are available as Relay Word bits in the
SEL
OGIC control equations, rather than “function assignments” as in the
SEL-251-3. The SEL-267-5 has very limited input programmability.
The expanded Relay Word bits in the SEL-351A can be used in any SEL
OGIC
control equation.
Courtesy of NationalSwitchgear.com
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