28
8. Periodical inspections
8.1 General
The capacitor-switch is maintenance free during normal service.
The frequency and type of inspections required depend on the
service conditions. Various factors must be taken into account:
frequency of operations, interrupted current values, relative
power factor and the installation ambient.
The following section includes an inspection chart showing the
relevant time intervals.
As far as the time interval between these operations is con-
cerned, it is advisable to comply with the specifications given in
the table, at least during the first check. The optimal time limits
for carrying out the following operations can be set according
to the results obtained during the periodic inspections.
8.2 Checking program
After two years of field operation/or 2,000 CO electrical cycles
check:
− DS1 CO functions with no power (see chapter on “Commis-
sioning - Test with no power, no sync”)
− System pressure
− Contact resistance (see chapter on “Measurement of resist-
ance across closed contacts of poles”).
If DS1 is installed in a polluted and aggressive ambient, it is
advisable to check every year as described above. If DS1 is
installed where a significant quantity of dust is present, clean
all parts every year as preventive maintenance.
It is advisable to contact an ABB service center to have the ap-
paratus checked after 5,000 electrical operations or 10 years.
Every maintenance program must include the following opera-
tions:
− Check that all parts are free from built up dust, dirt, cracks
and discharge traces in the following points:
− Check main bus bar screws tightening torque
− Check apparatus fixing screws tightening torque
− Remove the main cover and check the screws tightening
torque for terminal board connection
− Check all the wiring inside DS1 and its integrity
− Check the synchronization cable.
IMPORTANT
To operate in full safety, all maintenance
inspections must be performed with the
system de-energized, the upstream sup-
ply in safe conditions and the downstream
earth switch correctly connected. Compli-
ance with all additional safety rules is also
mandatory.
8.3 Measurement of air pressure inside
poles
Connect a pressure gauge on the filling valve and measure the
pressure inside the poles.
The value must be 4.7± 0.1 bar abs.
If value is lower, refill the poles up to their nominal pressure
value with dry air, as indicated in the previous section.
8.4 Dry Air filling
DS1 is a pressurized switch filled with dry air. The factory fills
DS1 with air possessing the following characteristics. Comply
with the same characteristics when a filling operation is per-
formed.
H
2
O
< 2 ppm
CnHm < 0.1 ppm
CO
< 1 ppm
CO
2
< 0.2 ppm
8.5 Dry air filling procedure
− Cover the three poles with a protective net
− Using a kit similar to the one shown in the figure below, con-
nect the pneumatic fast connector to the filling valve inlet.
− Open the main valve,
− Adjust the pressure limiter to about 5-6 bar
− Start filling.
− Increase the pressure up to the value of 4.7 bar absolute.
Figure 26. Filling equipment
Provided
by
Northeast
Power
Systems,
Inc.
(NEPSI)
