6–120
350 FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL
S4 CONTROLS
CHAPTER 6: SETPOINTS
BLOCK LOGIC
Range: OR, AND, NOR, NAND, XOR, XNOR
Default: OR
This setting defines the gate type for the block inputs.
A Logic Element can be used to provide under-voltage supervision when overcurrent
conditions are detected. The logic from the Logic Element below, see figure:
Example of
Block Logic setting from EnerVista
, shows that overcurrent trip will not be initiated unless
the relay detects either auxiliary or phase under-voltage conditions. In any other cases,
with both under-voltage elements dropped out, Overcurrent trip will not be initiated.
Each Logic Element can include output from another logic element.
Example: Programing an overall breaker alarm using Logic Elements
Figure 6-55: Example of an overall breaker alarm from EnerVista
In this example, all eight trigger sources from Logic Element 1 are programmed into an
OR gate, with operands originating from breaker functions such as Breaker Status,
Breaker Health, Trip Counter, Breaker Coil Monitoring, and Breaker Failure. The Trigger
Logic setpoint is selectable to any boolean operator such as OR, AND, NAND, NOR, XOR,
or XNOR. All four block inputs are programmed with contact inputs 1 to 4, and the Block
logic setpoint is programmed into an OR gate. These inputs may include Maintenance
input, Breaker disconnected input, Protection disabled input, etc.
Output Relay # 3 is selected to energize upon operation of Logic Element 1, to denote a
Breaker Alarm. With pickup time delay set to 2000ms, Logic Element 1 (BKR Alarm)
operation will occur 2 seconds after the operation of any of the trigger sources when no
block is applied.
