4.185
Date Code 20170927 Instruction Manual SEL-751 Relay
Protection and Logic Functions
Global Settings (SET G Command)
The display instrument expects -20 mA when the IA_MAG current is
0 A primary and +20 mA when it is 3000 A primary.
Station DC Battery
Monitor
The station dc battery monitor in the SEL-751 can alarm for under- or over-
voltage dc battery conditions and give a view of how much the station dc bat-
tery voltage dips when tripping, closing, and other dc control functions take
place. Refer to Station DC Battery Monitor on page 5.15 for a detailed
description and Table 5.9 for settings.
Breaker Monitor
The breaker monitor in the SEL-751 helps in scheduling circuit breaker main-
tenance. Refer to Breaker Monitor on page 5.19 for a detailed description and
Table 5.11 for settings.
Digital Input
Debounce
To comply with different control voltages, the SEL-751 offers dc debounce
modes as well as ac debounce modes. Therefore, if the control voltage is dc,
select the dc mode of operation, and if the control voltage is ac, select the ac
mode of operation. In general, debounce refers to a qualifying time delay before
processing the change of state of a digital input. Normally, this delay applies to both
the processing of the debounced input when you use it in device logic and the
time stamping in the SER. Following is a description of the two modes.
DC Mode Processing (DC Control Voltage)
Figure 4.109 shows the logic for the dc debounce mode of operation. To select
the dc mode of debounce, set IN101D to any number between 0 and 65000
ms. In Figure 4.109, Input IN101 becomes IN101R (internal variable), after
electrical isolation. On assertion, IN101R starts Debounce Timer, producing
Relay Word bit IN101 after the debounce time delay. The debounce timer is a
pickup/dropout combination timer, with debounce setting IN101D applying to
both pickup (pu) and dropout (do) timers, i.e., you cannot set any timer indi-
vidually. For example, a setting of IN101D := 20 ms delays processing of the
input signal by 20 ms (pu) and maintains the output of the timer (do) for 20
ms. Relay Word bit IN101 is the output of the debounce timer. If you do not
want to debounce a particular input, still use Relay Word bit IN101 in logic
programming, but set the debounce time delay to 0 (IN101D := 0).
=>>SET G AO301AQ TERSE <Enter>
Global
AO 301 Settings
AO301 ANALOG QTY (OFF, 1 analog quantity)
AO301AQ := OFF
? IA_MAG <Enter>
AO301 TYPE (I,V) AO301TYP:= I ? <Enter>
AO301 AQTY LO (-2147483647.000 to 2147483647.000)
AO301AQL:= 4.000 ? 0 <Enter>
AO301 AQTY HI (-2147483647.000 to 2147483647.000)
AO301AQH:= 20.000 ? 3000 <Enter>
AO301 LO OUT VAL (-20.480 to 20.480 mA) AO301L := 4.000 ? -20<Enter>
AO301 HI OUT VAL (-20.480 to 20.480 mA) AO301H := 20.000 ? 20<Enter>
AO 302 Settings
AO302 ANALOG QTY (OFF, 1 analog quantity)
AO302AQ := OFF
? END <Enter>
Save changes (Y,N)? Y <Enter>
Settings Saved
=>>
Figure 4.108 Analog Output Settings
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