GE 745 - 7.5.2.11 Energization Detection Scheme

7–22 745 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
PROTECTION SCHEMES CHAPTER 7: COMMISSIONING
FIGURE 7–8: Fifth harmonic restraint testing
 Increase the 5th harmonic component to a value well above the S4
ELEMENTS
 DIFFERENTIAL  5th HARM INHIBIT  5th
HARMONIC INHIBIT LEVEL setting.
 Remove the total current signal and reapply.
The relay should not operate.
 Decrease the 5th harmonic component until the element operates.
 Calculate the percentage 5th harmonic to restrain from the following
equation:
 Compare this value to the relay setting.
7.5.2.11 Energization Detection Scheme
Refer to Differential Element on page 5–48 for a description of this feature. This feature is
activated by up to three inputs: breaker auxiliary switch, current below a threshold, or
absence of voltage. The procedure below tests the current-level enabling feature. A similar
approach can verify the other two enabling functions with the proper test equipment.
 Enable the Energization Detection Scheme by setting
S4 ELEMENTS 
DIFFERENTIAL  ENERGIZATION INHIBIT  ENERGIZATION INHIBIT
FUNCTION
to Enabled.
 Make the following setpoint changes in the
S4 ELEMENTS 
DIFFERENTIAL
 ENERGIZATION INHIBIT setpoints menu:
ENERGIZATION INHIBIT PARMETERS: “2nd”
HARMONIC AVERAGING: “Disabled”
ENERGIZATION INHIBIT LEVEL: “15%”
ENERGIZATION INHIBIT DURATION: “5 s”
ENERGIZATION SENSING BY CURRENT: “Enabled”
ENERGIZATION INHIBIT/MINIMUM ENERGIZATION CURRENT: “0.10
× CT”
 Preset current with harmonic content just above the
ENERGIZATION
INHIBIT LEVEL used during the ‘energization period’.
%5th
100 level of 5th harmonic×
level of fundamental
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