doble TDR900 - Main Contact Timing Tests

Doble TDR900 User Guide
72A-2612-01 Rev. A 09/06
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Related problems which may lead to the above:
• Loss of pressure in SF6 or air systems
• Low quality oil
Simple breaker issues may include:
• Improper spring adjustment
• Excessive friction
• Worn contacts
• Improper stop adjustments
• Malfunctioning shock absorbers, buffers or dash pots
• Synchronization of contacts and phases
Pleas refer to the Doble training notes for detailed discussion of these and other breaker
issues.
4.7 Why Test a Breaker?
Breaker tests are performed to:
• Ensure the breaker is operating correctly
• To detect any conditions which may prevent operation
• To ensure maintenance has been beneficial to the breaker
• To identify any conditions which may be injurious to breaker performance
A breaker is rarely called on to operate to clear a fault. It may only be in “action” for less
than ten minutes in an expected thirty or more years of operation. However, when it is
called on to operate, in fault conditions, it is imperative that the fault is cleared to prevent
system issues which could lead to major incidents – local or widespread loss of service,
for example.
4.8 Main Contact Timing Tests
The breaker main contacts are timed to ensure they perform to specification.
Main contacts are the contacts which carry current during normal operation. When the
contacts open, an arc is formed. The arc is a conductor which needs to be extinguished.
If the breaker is sufficiently large, several breaks may be required for each phase to
ensure that there is no excessive voltage on any one break and arcs produced are
controlled.
As breakers have become larger (higher voltage and higher power), the number of breaks
per phase has increased. As technology has developed, so has the efficiency of arc
quenching improved and the number of breaks per phase has been reduced.
Consequently, there are many different types of breakers with a variety of breaks per
phase.