en07000127.vsd
U
3N
U
3T
IEC07000127 V1 EN-US
Figure 63: Typical phasor diagram for third harmonic voltages for healthy machine
1.
Inject the following voltages: U
3T
= 15 V, U
3N
= 5 V and the angle between the voltages =
180°. Check the monitored values of the following analogue signals: E3 (the magnitude of
the third-harmonic induced voltage in the stator), U
3N
: 5 V (the magnitude of the third-
harmonic voltage measured at the neutral side of the generator), U
3T
: 15 V (the
magnitude of the third-harmonic voltage measured at the terminal side of the generator)
and ANGLE: 180° (the angle between the third-harmonic voltage phasors U
3N
and U
3T
).
The value of E3 should be close to the following value:
(
) (
)
2
2
3N
3T
3T
E3
U
U
cos(ANGLE)
U
sin(ANGLE)
=
-
×
+
×
EQUATION2070 V1 EN-US
(Equation 100)
2.
Read the value of DU (differential voltage). The value of DU should be close to the
following value:
(
) (
)
2
2
3N
3T
3T
DU
U
U
cos(ANGLE)
U
sin(ANGLE)
=
+
×
+
×
EQUATION2071 V1 EN-US
(Equation 101)
3.
Decrease the value of the injected voltage U
3N
until the signal START3H is activated.
Check that
3
N
DU
U
Beta
=
EQUATION2072 V2 EN-US
(Equation 102)
considering stated accuracy (
beta is a setting parameter)
4.
Increase the voltage U
3N
so that the sart signal falls. After that, switch the voltage U
3N
to
zero and measure the time delay for the activation of the signals TRIP and TRIP3H.
The 100% stator earth fault protection also has a fundamental frequency neutral point
overvoltage function (95% stator earth fault protection). This part of the protection can
be tested separately by means of fundamental frequency voltage injection from a test
equipment.
12.6.6.2
Verifying settings
SEMOD158990-144 v3
1.
With the generator rotating at rated speed but not connected: check the value of the
following analogue signals: E3 (the magnitude of the 3
rd
harmonic induced voltage in the
stator), U
3N
(the magnitude of the third-harmonic voltage measured at the neutral side of
the generator), U
3T
(the magnitude of the third-harmonic voltage measured at the
1MRK 502 067-UEN B
Section 12
Testing functionality by secondary injection
191
Commissioning manual
