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G R I D S H I E L D
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9 Inspection, maintenance and adjustment
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The GridShield
37 Contact wear
measurement/
that requires minimal maintenance when handled
adjustment for
properly and based on the frequency of operation
24-pin GridShield 3P
and local environmental conditions.
The safety and proper functioning of any apparatus
or system connected to the recloser largely depend
on the correct installation, commissioning and
programming of the unit.
To help ensure long and reliable service, it is
important to regularly inspect the recloser.
Factors such as operating experience,
environmental conditions, the number
of operations, current magnitude and any
unusual service conditions should guide you
in establishing a maintenance schedule.
Here is a minimum checklist to follow:
1.
Inspect the molded pole assemblies
for external damage and clean them
if contamination is present. You can clean
the poles with a mild detergent, while
the HCEP bushings can be cleaned with
isopropyl alcohol.
2.
Check contact wear (only for 24-pin single-
tank units) — As the vacuum interrupter
continues to switch current, material from the
contact is pushed deeper into the interrupter
by the operating mechanism. The over-travel
spring at the upper end of the operating rod
ensures proper contact pressure in the closed
position. Contact erosion reduces the
compression of the over-travel spring,
increasing contact travel (the actuator's total
travel is fixed). To easily confirm allowable
contact erosion, use the 2.5 mm gauge
provided with the recloser. See figure 37,
and follow these steps:
a. Ensure the recloser is in the open position.
b. Connect an ohmmeter across the H1 and
®
3 P/ 3 S P R E C L O S E R
recloser is a straightforward device
®
H2 terminals.
c. Insert the 2.5 mm gauge into the holes
in the actuator housing.
d. Insert a large screwdriver or punch into
the slot on the actuator shaft.
e. Pry on the screwdriver to raise the shaft
as far as it can move.
f. The ohmmeter should indicate
approximately zero resistance. If the
ohmmeter reads open, it means the contact
erosion limit has been reached, and the
pole needs replacement.
g. Remove the 2.5 mm gauge and screwdriver
from the actuator.
For 32-/42-pin GridShield recloser units and
in general, you can monitor contact wear
through the breaker wear-monitoring function
built into the relay. Contact ABB technical
support to obtain the appropriate life curves
for each type of vacuum interrupter.
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37
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