ABB Relion 670 series, Installation And Commissioning Manual

Page: 206 / 260

3 N
DU
U
Beta
=
EQUATION2072 V2 EN
(Equation 15)
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.
15.7.6.2 Verifying settings
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 terminal side of the generator) and
ANGLE (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)
= - × + ×
EQUATION2076 V1 EN
(Equation 16)
Make sure that ANGLE has a value bigger than 125°
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)
= + × + ×
EQUATION2078 V1 EN
(Equation 17)
3. Read the value of BU (bias voltage: Beta ·U
3N
). The ratio DU/BU should be
well below 1 for a non-faulted generator.
4. After synchronization of the generator the ratio DU/BU is checked for
different load levels of the generator. These different monitoring of load
levels should be the base for the setting of
beta .
If the function is used with the option of neutral point measurement only the
test is performed by check of this voltage. The operate value should be above
the measured residual third-harmonic voltage in the neutral point at normal
operation (non-faulted generator).
Section 15
1MRK 502 029-UEN A
Verifying settings by secondary injection
200
Installation and commissioning manual