Metering
745
Transformer Management Relay
Commissioning
http://www.GEindustrial.com/multilin
7–7
GE Multilin
1. If you are using a single phase current supply, connect this current signal to all
the input CTs in series, Winding 1, 2 and 3, if using a 3-winding configuration,
and the ground CT input(s). Adjust the current level to 1 A for 1-amp-rated
relays and to 5 A for 5-amp-rated relays.
Some elements may operate under these conditions unless all elements
have been disabled!
2. With the above current signals ON, read the actual values displayed under
ACTUAL VALUES !" A2 METERING ! CURRENT. The actual values can be quickly
read using the enerVista 745 Setup software.
3. Read the RMS magnitude and the phase of the current signal in each phase of
each winding. Note that the Winding 1 Phase A current is used as the
reference for all angle measurements.
I
phase rms displayed
= I
phase input
x CT ratio for that winding
The phase angle will be 0° for all phase currents if the same current is injected
in all phase input CTs. Sequence components will be:
(EQ 7.1)
4. Since the transformer load is calculated using the Phase A current, the
displayed load should be:
where (EQ 7.2)
5. Verify the harmonic content display in A2 METERING !" HARMONIC CONTENT !"
THD !" W1...W2...W3. It should be zero or equal to distortion of input current.
6. Verify frequency shown in
A2 METERING !" FREQUENCY !" SYSTEM FREQUENCY. It
should be 60 or 50 Hz, as per frequency of input current on Phase A.
7. 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.
where a = 1∠120°
(EQ 7.3)
(EQ 7.4)
All angles will be 0°. These values are displayed in the A2 METERING ! CURRENT
!" POSITIVE SEQUENCE !" W1...W2...W3 and A2 METERING ! CURRENT !" NEGATIVE
SEQUENCE !" W1...W2...W3 actual values menus.
8. Now, 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.
Voltage Input 1. 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.
I
1
CT Ratio
I
a
aI
b
a
2
I
c
++
3
----------------------------------------
× 0, all 3 currents in phase, and a 120°∠== =
I
2
CT Ratio
I
a
aI
b
a
2
I
c
++
3
----------------------------------------
× 0, the 3 currents are in phase==
I
zero-sequence
CT Ratio input current×=
I
neutral
3 CT Ratio input current××=
I
ground
Ground CT Ratio input current into Ground CT×=
% Loading
Actual Current
Rated MVA Current
---------------------------------------------------------
100%×=
Rated MVA Current
MVA
3kV
LL–
--------------------------=
I
1
1
3
---
CT Ratio× I
a
aI
b
a
2
I
c
++()×
1
3
---
CT Ratio× I
a
× since I
b
I
c
0====
I
2
1
3
---
CT Ratio× I
a
a
2
I
b
aI
c
++()×
1
3
---
CT Ratio× I
a
× since I
b
I
c
0====
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