Tettex MIDAS 2881, Руководство по эксплуатации

Страница: 32 / 164

22 Functional Description
GSTgA
Grounded Specimen Test with guarding (V-
potential) connected to A (bypassed). HV
GND and B are used as measuring channels.
V R
X
R
X
C
HL2
+
C
HG
GSTgB
Grounded Specimen Test with guarding (V-
potential) connected to B (bypassed). HV
GND and A are used as measuring channels.
R
X
V R
X
C
HL1
+
C
HG
GST gA+B
Grounded Specimen Test with guarding (V-
potential) connected to A and B (bypassed).
Only HV GND is used as measuring channel.
V V R
X
C
HG
Note: For testing the insulation secondary winding – tank, the HV cable and measuring cables shall
be exchanged. The HV shall be connected to the secondary winding(s) and the measuring cable to
the primary winding. The measured capacitances in the table will change accordingly.
Test Mode „UST” for ungrounded test objects
This test mode is the most common situation when measuring capacitance and dissipation factor.
Various ungrounded capacitances can be measured using this mode, providing that the maximum test
current of the measuring instrument is not exceeded.
When measuring power transformers and HV current transformers, this configuration determines the
capacitance and dissipation factor between the various winding groups.
In this mode the highest measurement accuracy is reached.
Test Mode „GST“ for grounded test objects
This test mode enables the measurement of capacitances that are normally earthed on one side when
in operation. When measuring transformers‚ this configuration measures the capacitance and
dissipation factor between the HV winding and all other windings and the transformer housing.
Test Mode „GST g“ for grounded test objects with guarding (V-potential)
This test mode directly measures the capacitance between the HV terminal and the housing (which is
grounded). The partial capacitances that are undesirable for the measurement are connected to the
V-potential point and thereby rendered ineffective.
When measuring transformers‚ this configuration measures the capacitance and dissipation factor
between the various winding groups and the transformer housing. The windings which are not used
for measurement are connected to the v-potential of the measuring system via the A (or B) measuring
cable and the internal Test Mode Switch.