ABB RET670 - Page 161

• the point RE (R
FwdR
, X
FwdX
)
• a point which is related to the parameter ReachZ1 (boundary between zone 1
and zone 2)
• the point SE (R
RvsR
, X
RvsX
)
The phase angle of the test voltages is equal to:
• arctan (ForwardX/ForwardR) for tests in the quadrant 1 and 2 of the R-X plane
• arctan (ReverseX/ReverseR) -180° for tests in the quadrant 3 and 4 of the R-X plane
• Symmetric three-phase current, where the current is the summation of two currents
that have the same magnitude, but different frequencies.
I I A
tf
t
I
50
2
20918
2
10459= = = =
GUID-F02E8D18-FF87-45BE-8142-E8FA19F6966B V1 EN (Equation 16)
The first current I
50
has frequency 50 Hz, magnitude 10459 A (that is, 1.162 A
secondary) and phase angle 0º.
The second current I
tf
has magnitude 10459 A (that is, 1.162 A secondary), phase
angle 180º (at the starting time of the test) and frequency:
• 49.5 Hz for the test as generator in the quadrant 1 and 2 of the R-X plane
• 50.5 Hz for the test as generator in the quadrant 3 and 4 of the R-X plane
When the trajectory of the impedance, that is seen by the protection
function, traverses the lens characteristic then a pole slipping is detected.
The present procedure avoids tests of points of the line SE-RE that are too
close to the R-axis because in that case the voltage is close to zero and,
therefore, the impedance may approach a not defined quantity 0/0.
The accuracy of the impedance reach is ±2% of the base impedance; that
is considered while evaluating the test results.
For the test as motor the frequency current may have 50.5 Hz in the
quadrant 1 and 2 of the R-X plane and 49.5 Hz in the quadrant 3 and 4.
1MRK 504 165-UUS - Section 11
Testing functionality by secondary injection
Transformer protection RET670 2.2 ANSI 155
Commissioning manual