GE 889 Instruction Manual page 246

PROTECTION
4–116
BREAK 1
Range: 0.50 to 2.00 x CT in steps of 0.01
Default: 1.50
The setting defines the end of the Slope 1 region and the start of the transition region. It
should be set just above the maximum normal operating current level of the machine.
BREAK 2
Range: 2.00 to 30.00 x CT in steps of 0.01
Default: 4.00
The setting defines the end of the transition region and the start of the SLOPE 2 region. It
must be set to the level at which any of the protection CTs are expected to begin to
saturate. To avoid discontinuity in the cubic spline calculation, the relay applies a
minimum margin of 0.3 CT between BREAK 1 and BREAK 2.
SLOPE 2
Range: 1 to 100% in steps of 1
Default: 95%
The setting is applicable for restraint currents above the BREAK 2 setting. The slope is set
to ensure stability under heavy external fault conditions that could lead to high
differential currents as a result of CT saturation. A setting of 80 to 100% is
recommended. The transition region (as shown on the percent differential characteristic)
is a cubic spline, automatically calculated by the relay to result in a smooth transition
between SLOPE 1 and SLOPE 2 with no discontinuities.
PICKUP DELAY
Range: 0.000 to 10.000 in steps of 0.001
Default: 0.000
This setting defines the pickup time delay of the percent differential element.
BLOCK
Range: Off, Any FlexLogic operand
Default: Off
OUTPUT RELAY X
Range: Do Not Operate, Operate
Default: Do Not Operate
EVENTS
Range: Disabled, Enabled
Default: Enabled
TARGETS
Range: Disabled, Self-reset, Latched
Default: Latched
889 GENERATOR PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 4: SETPOINTS