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Section 10
Testing functionality by secondary injection
128
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
•
a point which is related to the parameter ReachZ1 (boundary between zone
1 and zone 2)
•
the point SE (R
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.
20918
I
t
I
I
=
=
=
50
tf
2
2
GUID-F02E8D18-FF87-45BE-8142-E8FA19F6966B V1 EN
The first current I
50
secondary) and phase angle 0º.
The second current I
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.
, X
)
FwdR
FwdX
, X
)
RvsR
RvsX
A
10459
=
has frequency 50 Hz, magnitude 10459 A (that is, 1.162 A
has magnitude 10459 A (that is, 1.162 A secondary), phase
tf
1MRK 506 355-UEN A
(Equation 16)
Line distance protection REL670 2.1 IEC
Commissioning manual
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