CHAPTER 8: AUTOMATION AUTOMATION CONTROL
D90
PLUS
LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL 455
Selector switch
The selector switch element replaces a mechanical selector switch. Typical applications
include setting group control or control of multiple logic sub-circuits in user-programmable
logic.
Selector switch operation
The selector switch provides for two control inputs. The step-up control allows stepping
through selector position one step at a time with each pulse of the control input, such as a
user-programmable pushbutton. The three-bit control input allows setting the selector to
the position defined by a three-bit word.
The element allows pre-selection of a new position without applying it. The pre-selected
position gets applied either after time-out or upon acknowledgement via separate inputs
(user setting). The selector position is stored in non-volatile memory. Upon power-up, either
the previous position is restored or the relay synchronizes to the current three-bit word
(user setting). Basic alarm functionality alerts the user under abnormal conditions, for
example, the three-bit control input being out of range.
The following figures illustrate the operation of the selector switch. In these diagrams, “T”
represents a time-out setting.
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