GE 745 Instruction Manual page 248

METERING
7.4.3 Voltage Input
Note
NOTE
7–10
Since the transformer load is calculated using the maximum current from phases A, B, or C,
the displayed load should be:
% Loading
where
 Verify the harmonic content display in
CONTENT
It should be zero or equal to distortion of input current.
 Verify frequency shown in
SYSTEM
It should be 60 or 50 Hz, as per frequency of input current on Phase A.
 To verify the positive and negative sequence component values, apply
the current signal to Phase A of each winding in series.
Read the values of positive and negative sequence current displayed by
the relay.
1
I -- - × CT Ratio
=
1
3
1
I -- - × CT Ratio
=
2
3
All angles will be 0°. These values are displayed in the
POSITIVE SEQUENCE W1...W2...W3

SEQUENCE W1...W2...W3

 Lower the current amplitude while displaying the system frequency.
 Verify that the frequency is displayed correctly with current levels down
to approximately 50 mA RMS input.
 Decrease current to 0 A.
 Connect an AC voltage to the voltage input (if the input voltage feature
is enabled) to terminals C11 and C12.
 Set the level at the expected VT secondary voltage on the VT for your
installation.
 Remove all current signals from the relay.
 Verify the voltage reading in
LINE-TO-LINE
The reading should be equal to the input voltage × VT ratio.
The displayed system voltage is always the line-to-line voltage regardless of the input
VT signal. Earlier versions of the 745 may display the same voltage as the selected
input, i.e. phase-to-neutral if the input is a phase-to-neutral signal and phase-to-
phase if the input is phase-to-phase.
Actual Current
----------------------------------------------- -
=
Rated MVA Current
Rated MVA Current
=
THD W1...W2...W3.
 
A2 METERING
FREQUENCY.
1
2
× ( I aI a I ) -- - × CT Ratio
+ + =
a b c
3
where a = 1∠120°
1
2
× ( I a I aI ) -- - × CT Ratio
+ + =
a b c
3
and A2 METERING
actual values menus.
A2 METERING
VOLTAGE.
745 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 7: COMMISSIONING
× 100%
MVA
---------------------- -
3kV
L L
–
A2 METERING HARMONIC

FREQUENCY

× I since I I
= =
a b c
× I since I I
= =
a b c
A2 METERING CURRENT

CURRENT NEGATIVE
 
VOLTAGE
 
(EQ 7.2)

0
(EQ 7.3)
0
(EQ 7.4)

SYSTEM