Siemens WL Type 480V 4000A Circuit Breaker Contact Wear

[kbow364]

Performed an inspection of the arc chutes and contact surfaces on a 4000A WL type breaker. The O&M manual says I should replace the contact assemblies based on the contact wear indicator, but that is a pretty intense evolution involving the complete disassembly of the breaker. Does anyone know how these contact wear indicators are supposed to work? I agree with the indication due to the evidence of some heavy arcing, but I would like to know how they work so I can explain to the higher ups about why we need to spend $10k on breaker parts.

The manual says if the indicator pin is no longer visible in the "big recess", then the contact assembly must be replaced. The breaker we have looks identical to the example given in the manual for all 3 phases.

 

[kbow364]

Here is a photo of the indicator from the inspection

 

[che12345]

I have the following opinion for you consideration
1. This is a 4kA breaker, you should be very careful on the contact ware. My suggestion is you should contact the OEM to carry out the inspection. For inspection only, the charges would not be very high. If need parts replacement, the inspection fees may be deducted from the total parts and service bill.
1.1 Info: As an indication, the 4kA breaker can take up to say 2000 O-C-O operations cycles at say << 1kA; or say 300 O-C-O cycles at 4kA.
2. Attention: if the breaker trips on short-circuit (say > 50kA or unknown value); the contacts should be investigated thoroughly for damage.
2.1 All three poles should be investigated for ware (by checking the contact resistance) and all three poles close simultaneously (by three channel stroke/travel recording).
Che Kuan Yau (Singapore)