GE G30 Instruction Manual page 415

CHAPTER 5: SETTINGS
The thermal elements include hottest-spot temperature, aging factor and loss of life. The computation of these elements
follows IEEE standards C57.91-1995: "IEEE Guide for Loading Mineral-Oil-Immersed Transformers" and C57.96-1989: "IEEE
Guide for Loading Dry-Type Distribution Transformers". The computations are based on transformer loading conditions,
ambient temperature, and the entered transformer data.
5.7.3.2 Transformer percent differential (ANSI 87GT)
SETTINGS  GROUPED ELEMENTS  SETTING GROUP 1(6)  TRANSFORMER  PERCENT DIFFERENTIAL
 PERCENT
 DIFFERENTIAL
The calculation of differential (I
by the following block diagram, where "Σ" has as its output the vector sum of inputs, and "max" has as its output the input
of maximum magnitude; these calculations are performed for each phase.
The differential current is calculated as a vector sum of currents from all windings after magnitude and angle
compensation.
The restraint current is calculated as a maximum of the same internally compensated currents.
The element operates if I > PKP and I
d
restraint factor defined by the relays settings Slope 1, Slope 2, and a transition area between breakpoint 1 and breakpoint
2 settings.
G30 GENERATOR PROTECTION SYSTEM – INSTRUCTION MANUAL
PERCENT DIFFERENTIAL

FUNCTION: Disabled
PERCENT DIFFERENTIAL

PICKUP: 0.100 pu
PERCENT DIFFERENTIAL

SLOPE 1: 25%
PERCENT DIFFERENTIAL

BREAK 1: 2.000 pu
PERCENT DIFFERENTIAL

BREAK 2: 8.000 pu
PERCENT DIFFERENTIAL

SLOPE 2: 90%
INRUSH INHIBIT

FUNCTION: Adapt. 2nd
INRUSH INHIBIT

MODE: Per phase
INRUSH INHIBIT

LEVEL: 20.0% fo
OVEREXCITN INHIBIT

FUNCTION: Disabled
OVEREXCITN INHIBIT

LEVEL: 10.0% fo
PERCENT DIFF BLOCK:

Off
PERCENT DIFFERENTIAL

TARGET: Self-reset
PERCENT DIFFERENTIAL

EVENTS: Disabled
) and restraint (I ) currents for the purposes of the percent differential element is described
d r
/ I > K, where PKP represents a percent differential pickup setting and K is a
d r
GROUPED ELEMENTS
Range: Disabled, Enabled
Range: 0.050 to 1.000 pu in steps of 0.001
Range: 15 to 100% in steps of 1
Range: 1.000 to 2.000 pu in steps of 0.001
Range: 2.000 to 30.000 pu in steps of 0.001
Range: 50 to 100% in steps of 1
Range: Disabled, Adapt. 2nd, Trad. 2nd
Range: Per phase, 2-out-of-3, Average, 1-out-of-3
Range: 1.0 to 40.0% of f in steps of 0.1
0
Range: Disabled, 5th
Range: 1.0 to 40.0% of f in steps of 0.1
0
Range: FlexLogic operand
Range: Self-reset, Latched, Disabled
Range: Disabled, Enabled
5
Eq. 5-29
Eq. 5-30
5-201