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5-24
Applications
Date Code 20011026
SEL-321/321-1 Instruction Manual
For our example, we have to set the minimum trip duration timer and the instantaneous trip time
declaration delay.
TDURD = 9.00
9.00
9.00
9.00
TOPD = 0.00
0.00
0.00
0.00
TXPU = 0.00
0.00
0.00
0.00
TXDO = 0.00
0.00
0.00
0.00
TYPU = 0.00
0.00
0.00
0.00
TYDO = 0.00
0.00
0.00
0.00
TZPU = 0.00
0.00
0.00
0.00
TZDO = 0.00
0.00
0.00
0.00
ITTD = 5.00
5.00
5.00
5.00
- Other Settings Affected
XT, YT, and ZT time delayed SEL
OGIC
control equations variable outputs.
SEL
OGIC
Control Equations
Programming SEL
OGIC
control equations consist of assigning functions to the programmable
inputs, designing the internal logic functions your application requires, expressing the logic in
terms of the relay element and internal logic variables, and finally defining the output functions.
Additionally, you may program intermediate logic points and the output contacts with SEL
OGIC
control equations. This permits you to combine any element in Tables 2.7, 2.9, or 2.10 in
Section 2: Specifications
, use non-dedicated timers for special applications, and assign these
combinations to output contacts.
Logic Variable Equations
Five programmable logic variables are provided which allow you to design your own internal
logic conditions. For our example, these variables are not required.
Tripping Logic Equations
There are three logic equations that must be set for tripping.
The MTCS logic equation determines which elements trip via the communications-based logic.
Typically the overreaching Zone 2 elements are set in the MTCS logic equation.
The MTU logic equation determines which elements trip unconditionally. Typically all direct
tripping and time-delayed tripping elements are set in the MTU logic equation.
The MTO logic equation defines which elements are enabled to trip while SOTFE is asserted.
All elements set in this trip instantaneously, if they assert during the SOTFD time. This is
referred to as the Switch-Onto-Fault logic.
For our example, all of the instantaneous and time delayed tripping elements are set in MTU.
The overreaching Zone 2 elements are set in MTCS. Since the elements set in the MTO are
enabled to trip for SOTFD time, the 50H and all overreaching and underreaching instantaneous
elements are set in this equation.
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