Test sets usually do not have a feature to simulate a real network during a power swing
and apply the related analog quantities at the terminal of the generator. The scope of
the present test is not a simulation of a real network. Voltages and currents are supplied
in order to measure an impedance that changes in the time and traverses the plane R-
X and, in particular, the area inside the lens characteristic. The test may be performed
by applying:
•
Symmetric three-phase voltage at 50 Hz. The magnitude depends on the point of
the characteristic that needs to be verified. The following three main points of the
line segment SE-RE need to be checked:
•
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.
Section 12
1MRK502053-UEN B
Testing functionality by secondary injection
126
Generator protection REG670 2.0 IEC
Commissioning manual
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