Logic Diagrams - GE 845 Instruction Manual

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Logic Diagrams

4–8
• PICKUP: The setpoint selects the threshold equal to or above (for over elements) or
equal to or below (for under elements) which the measured parameter causes an
output from the measuring element.
• PICKUP DELAY: The setpoint selects a fixed time interval to delay an input signal from
appearing as an output.
• DROPOUT DELAY: The setpoint selects a fixed time interval to delay dropping out the
output signal after being generated.
• TDM: The setting provides a selection for Time Dial Multiplier which modifies the
operating times per the selected inverse curve. For example, if an IEEE Extremely
Inverse curve is selected with TDM=2, and the fault current is 5 times bigger than the
PKP level, operation of the element can not occur before an elapsed time of 2.59 s
from Pickup.
• OUTPUT RELAYS: The
<ELEMENT_NAME> RELAYS
operate when the feature generates an output. The range is any combination of the
Auxiliary output relays. The letter "X" denotes the number of auxiliary output relays
defined for the relay's order code.
• DIRECTION: The <ELEMENT_NAME> DIRECTION
features which are subject to control from a directional element. The range is
"Disabled", "Forward", and "Reverse". If set to "Disabled", the element is allowed to
operate for current flow in any direction. There is no supervision from the directional
element. If set to "Forward", the OC element is allowed to operate when the fault is
detected by the directional element in forward direction. In this mode, the OC element
does not operate for fault in reverse direction. If set to "Reverse", the OC element is
allowed to operate when the fault is detected in reverse direction, and does not
operate in forward direction.
• RESET: Selection of an Instantaneous or a Timed reset is provided by this setting. If
Instantaneous reset is selected, the element resets instantaneously providing the
quantity drops below 97 to 98% of the PKP level before the time for operation is
reached. If Timed reset is selected, the time to reset is calculated based on the reset
equation for the selected inverse curve.
• BLOCK: The <ELEMENT_NAME> BLOCK
FlexLogic operands, which when active, blocks the feature from running.
• EVENTS: The
<ELEMENT_NAME> EVENTS
"Disabled". If set to "Enabled", the events associated with the pickup, operation, or
other conditions of the feature are recorded in the Event Recorder.
• TARGETS: The
<ELEMENT_NAME> TARGETS
Reset", or "Latched". If set to "Self-Reset", or "Latched", the targets associated with the
pickup, operation, or another condition of the feature are displayed on the screen of
the 845 relay. The targets disappear from the screen when "Self-Reset" is selected,
and the conditions are cleared. The targets stay on the screen, when "Latched" is
selected, and the conditions are cleared.
To ensure the settings file inside the relay is updated, wait 30 seconds after a setpoint
change before cycling power.
When IP addresses are changed and sent as a Settings file the unit reboots twice.
Refer to the logic diagrams provided for a complete understanding of the operation of
each feature. These sequential logic diagrams illustrate how each setpoint, input
parameter, and internal logic is used in a feature to obtain an output. In addition to these
logic diagrams, the Setpoints chapter provides written descriptions for each feature.
setpoint selects the relays required to
setpoint is available for overcurrent
setpoint selects an operand from the list of
setpoint can be set to "Enabled", or
setpoint can be set to "Disabled", "Self-
845 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 4: SETPOINTS