Garton Effect - GE OTCF Instruction Manual

Instruction Manual
The voltage ratio can be verified by
applying voltage to the bellows flange
of the lower capacitive module with
the tank grounded. For CVT with more
than one capacitive module, it is
recommended to perform the test on
the base unit (tank + lower capacitive
module) by applying the voltage to
the bellows flange of the lower
capacitive module for results with
greater sensitivity.
The formula for determining the
expected voltage at the secondary
terminals is given below:
U
S
Where:
n: Number of capacitive modules of
the complete CVT
V: Applied voltage
R: Voltage ratios stated at nameplate
Us: Expected voltage at secondary
terminals.
Example:
The capacitive divider of a standard
OTCF-362 consists of 2 capacitive
modules. Considering
informed voltage
nameplate is 1800: 1, the expected
voltage between
terminals when 10 kV is applied
between the lower capacitive and the
grounded tank will be 10 V, ie,
2x10,000 / 1800.
If the values obtained are different
than expected, contact the factory,
informing the serial number of the
equipment.

8.5. GARTON effect

© GE Grid Solutions
V
n
 
R
that the
ratio on the
the secondary
Since the synthetic oil used by GE in
the capacitive modules is a powerful
solvent, it is inevitable that the oil
dissolves some material on the
capacitive elements
forming ions.
This fact tends to increase the
dissipation factor when measured at
reduced voltage values (ie, values
equal to or less than 10% of rated
voltage).
For new capacitors, the influence of
the Garton effect, in any case, should
not result in dissipation factor values
equal to or greater than 0.3% with
application of 10% of the rated
voltage.
Measurements above this value may
be indicative of poor oil quality. In this
case, the user must consult the
factory, always informing the serial
number of the unit.
When performing dissipation factor
measurements on capacitors that are
in operation for some time, it is
recommended that the measurement
be performed within 48 hours after
removing it from operation.
Measurements performed after 3
days from operation can result in high
values, of the order of 1%, due to the
following phenomena:
• Ionic concentration in the system,
due to the circulation of oil inside the
capacitor in operation has become
uniform and complete.
• The ions are distributed more
evenly in the thin film of oil between
elements than at the time they were
manufactured.
or insulator