Current Elements - GE D90 Plus Instruction Manual

CHAPTER 7: PROTECTION

Current elements

Overview of time overcurrent curves
PLUS
D90 LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
Reset Delay
Range: 0.000 to 65.535 seconds in steps of 0.001
Default: 0.000 seconds
This setting specifies a delay for the reset of the load encroachment element between
the operate output state and the return to logic 0 after the input passes outside the
defined pickup range. It is normally set to zero.
Block
Range: any FlexLogic™ operand
Default: Off
Assertion of the FlexLogic™ operand assigned to this setting will block operation of the
load encroachment element.
Events
Range: Enabled, Disabled
Default: Enabled
This setting enables and disables the logging of load encroachment events in the
sequence of events recorder.
The logic for the load encroachment scheme is shown below.
Figure 148: Load encroachment scheme logic
The current element settings are described in this section.
The inverse time overcurrent curves used by the time overcurrent elements are the IEEE,
2
IEC, GE Type IAC, and I t standard curve shapes. This allows for simplified coordination with
downstream devices. If however, none of these curve shapes is adequate, FlexCurves™
may be used to customize the inverse time curve characteristics. The definite time curve is
also an option that may be appropriate if only simple protection is required.
The following overcurrent curve types are available.
• IEEE Extremely Inverse.
• IEEE Very Inverse.
• IEEE Moderately Inverse.
• IEC Curve A (BS142).
• IEC Curve B (BS142).
• IEC Curve C (BS142).
• IAC Extremely Inverse.
• IAC Very Inverse.
GROUPED PROTECTION ELEMENTS
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