GE T35 Instruction Manual page 161

5 SETTINGS
If set to "Average", the relay first calculates the average 2nd harmonic ratio, then applies the inrush threshold to the
calculated average. This mode works only in conjunction with the traditional 2nd harmonic function.
• OVEREXCITATION INHIBIT MODE: An overexcitation condition resulting from an increased V/Hz ratio poses a dan-
ger to the protected transformer, hence the V/Hz protection. A given transformer can, however, tolerate an overfluxing
condition for a limited time, as the danger is associated with thermal processes in the core. Instantaneous tripping of
the transformer from the differential protection is not desirable. The relay uses a traditional 5th harmonic ratio for inhib-
iting its differential function during overexcitation conditions.
• OVEREXCITATION INHIBIT LEVEL: This setting is provided to block the differential protection during overexcitation.
When the 5th harmonic level exceeds the specified setting (5th harmonic ratio) the differential element is blocked. The
overexcitation inhibit works on a per-phase basis.
The relay produces three FlexLogic™ operands that may be used for testing or for special applications such as building
custom logic (1-out-of-3) or supervising some protection functions (ground time overcurrent, for example) from the 2nd har-
monic inhibit.
PERCENT DIFFERENTIAL
FUNCTION:
Disabled = 0
Enabled = 1
SETTING
PERCENT DIFF BLOCK:
Off = 0
ACTUAL VALUES
DIFF PHASOR
Iad
Ibd
Icd
ACTUAL VALUES
REST PHASOR
Iar
Ibr
Icr
SETTING
INRUSH INHIBIT
FUNCTION:
Disabled = 0
ACTUAL VALUES
DIFF 2ND HARM
Iad2
Ibd2
Icd2
SETTING
OVEREXC ITN INHIBIT
FUNCTION:
Disabled = 0
5th = 1
ACTUAL VALUES
DIFF 5TH HARM
Iad5
Ibd5
Icd5
GE Multilin
SETTINGS
PERCENT DIFFERENTIAL
PICKUP:
PERCENT DIFFERENTIAL
SLOPE 1:
PERCENT DIFFERENTIAL
BREAK 1:
PERCENT DIFFERENTIAL
SLOPE 2:
PERCENT DIFFERENTIAL
BREAK 2:
AND RUN
Iad
Iar
AND RUN
Ibd
Ibr
AND RUN
Icd
Icr
SETTING
INRUSH INHIBIT LEVEL
FUNCTION & MODE:
RUN
>
Iad2
LEVEL
RUN
>
Ibd2
LEVEL
RUN
>
Icd2
LEVEL
SETTING
OVEREXC ITN INHIBIT
LEVEL:
RUN
>
Iad5
LEVEL
RUN
>
Ibd5
LEVEL
RUN
>
Icd5
LEVEL
Figure 5–42: PERCENT DIFFERENTIAL SCHEME LOGIC
T35 Transformer Management Relay
5.5 GROUPED ELEMENTS
FLEXLOGIC OPERANDS
XFMR PCNT DIFF PKP A
XFMR PCNT DIFF PKP B
XFMR PCNT DIFF PKP C
FLEXLOGIC OPERANDS
XFMR PCNT DIFF OP A
XFMR PCNT DIFF OP B
XFMR PCNT DIFF OP C
AND
FLEXLOGIC OPERAND
AND OR XFMR PCNT DIFF OP
AND
FLEXLOGIC OPERANDS
XFMR PCNT DIFF 2ND A
XFMR PCNT DIFF 2ND B
XFMR PCNT DIFF 2ND C
FLEXLOGIC OPERANDS
XFMR PCNT DIFF 5TH A
XFMR PCNT DIFF 5TH B
XFMR PCNT DIFF 5TH C
828001A5.CDR
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