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GE Power Management 745 Transformer Management Relay 5-49

5 SETPOINTS 5.6 S4 ELEMENTS

b) HARMONIC INHIBIT

This section contains the settings of the percent differential harmonic inhibit feature. This the percent differen-

tial element in a particular phase if the 2

harmonic of the same phase exceeds the

HARMONIC INHIBIT LEVEL

setpoint. With harmonic inhibit parameters set to

2nd+5th

, the RMS sum of the 2

and 5

harmonic compo-

nents is compared against the level setting. With harmonic averaging enabled, all three phases are inhibited if

the three-phase average of the harmonics exceeds the level setting.

c) ENERGIZATION INHIBIT

Over and above the standard harmonic inhibit feature programmed above, the 745 contains a harmonic inhibit

feature which is in service only during energization and/or sympathetic inrush.

De-energization and energization of the transformer is detected by any of the following three methods:

1. With energization sensing by current enabled, all currents dropping below the minimum energization cur-

rent indicates de-energization; any current exceeding the minimum energization current indicates energi-

zation. This method is the least reliable method of detecting energization, since an energized and

unloaded transformer will be detected as being de-energized if this method is used alone.

2. With energization sensing by voltage enabled, the voltage dropping below the minimum energization volt-

age indicates de-energization; any

current

exceeding the minimum energization current indicates energi-

zation.

3. With ‘b’ auxiliary contacts from all switching devices (which can be used to energize the transformer) con-

nected in series to a logic input and assigned to the

BREAKERS ARE OPEN

setpoint, the contacts closed indi-

cates de-energization; any current exceeding the minimum energization current indicates energization.

Energization inhibit settings are put in service upon detection of de-energization. Upon energization, the ener-

gization inhibit duration timer is initiated and the settings are removed from service when the time delay

elapses.

y HARMONIC INHIBIT

[ENTER] for more

This message indicates the start of the

HARMONIC INHIBIT

section. To

continue with these setpoints press , or press to go to the

next section.

HARMONIC INHIBIT

FUNCTION: Enabled

Range: Disabled / Enabled

HARMONIC INHIBIT

PARAMETERS: 2nd

Range: 2nd / 2nd + 5th

Select

2nd

to compare only the 2

harmonic current against the

HARMONIC

INHIBIT LEVEL

. Select

2nd+5th

to use the RMS sum of the 2

& 5

harmonic

components. For most transformers, the 2

harmonic current alone will

exceed 20% during energization and the

2nd

setting is sufficient to inhibit the

differential element for inrush current.

HARMONIC AVERAGING:

Disabled

Range: Disabled / Enabled

Select

Enabled

to use the three-phase average of the harmonic current

against the harmonic inhibit setting. For most applications, enabling

harmonic averaging is not recommended.

HARMONIC INHIBIT

LEVEL: 20.0%

ƒο

Range: 0.1 to 65.0 (steps of 0.1)

Enter the level of harmonic current (2

or 2

) above which the percent

differential element will be inhibited from operating. For most applications,

this level should be set to

20%

ENTER

MESSAGE

Brand	GE
Model	745 TRANSFORMER MANAGEMENT RELAY
Category	Relays
Language	English

GE 745 TRANSFORMER MANAGEMENT RELAY User Manual

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GE 745 TRANSFORMER MANAGEMENT RELAY Specifications

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