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6 Maintenance
6.4.11.3 Functional
Check, Anti-Pumping Feature
Circuit-breaker in closed position: (closing spring tensioned)
- Give electrical CLOSE command and keep button pressed in (maintained command)
The circuit-breaker must only switch off.
6.4.11.4 Function Check of Enforced Triple-Pole Operation Feature
Close all three poles of the circuit-breaker and open one of them by actuating the operating trip 18.8 (Fig. 70).
After the time set on the enforced triple-pole operation relay on the plant side has elapsed, the other two circuit-
breaker poles must also be tripped by the enforced triple-pole operation contactor. Carry out this test in a similar
manner on the other two circuit-breaker poles.
6.4.12
Check of Motor Control
Check whether after a closing operation the motor is activated by a limit switch, and, whether after the charging
process of the closing spring the motor is deactivated via a limit switch.
Perform this check at all poles.
6.4.13
Measuring the SF
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Gas Humidity Content
Before putting the breaker into operation, the humidity of the SF
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-gas must be checked. For this a commercially
available dew point measuring instrument with °C scale can be used. The maximum permissible dew point
temperatures at operating pressure corresponding to the permissible humidity are stated below.
Critical humidity limit
-5°C (+23°F)
Maximum permissible humidity
during commissioning/in operation
-10°C(+14°F)
Table 15 Dew point
If the measured dew point temperature lies above -10°C/+14°F, then the SF
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gas must dried using a service unit.
6.4.14 Measuring the SF
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Air Content
When the breaker has been filled with new gas and following maintenance work, the air content should not be
more than 5 % as measured with the SF
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percentage instrument 3-027 from DILO (D-87727 Babenhausen,
Federal Republic of Germany). This instrument measures the SF
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volumetric portion (at least 95 %).