Megger MPRT 8430 - Voltage Output Connections

separated by an angle of 60
o
. This is done by setting the V
1
and V
g
potentials equal in
magnitude, setting 0° on V
1
and 300
o
(60 degrees leading assuming that the default phase
rotation is set to 360 Lag) on V
2
, (reference following figure).
Balanced 3θ - 3 Wire Fault Open Delta Connection
If V
f
equals the desired test potential, then:
Set V
1
= V
f
∠ 0
o
Set V
2
= V
f
∠ 300
o
3.4.3.1.1 Voltage Output Connections
When setting up an unbalanced Open-Delta configuration, the desired phase-to-phase fault
voltage, V
1f
is set using voltage channel #1 with its phase angle set to 0°. Phase-to-phase
voltage V
2f
and its phase angle relationship for voltage channel #2, must be calculated using the
Law of Cosines; where For any triangle the following formula applies:
A
β
C B
AB
2
= AC
2
+ BC
2
– 2 x AB x BC x cos ß.
The next figure shows the phase relationships between voltages and an example of the
necessary calculation. For convenience the amplitude and the phase angle settings for the
typical V
f
fault magnitudes are tabulated.
36
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