During my plant's last pre-CDBI (Component Design Bases Inspection) self assessment (this was performed before I started working here) an issue was discovered in a few of our calcs.
Apparently, it was decided that a statement that contact resistance of hand switches, breakers, limit switches, etc. being negligible was not an acceptable statement without some sort of supporting documentation. The basis for the assumption was that the voltage drop across these contacts would be insignificant when viewed against the voltage drop along the cable connected to these contacts.
These contacts are mostly associated with our 125V vital battery system, so I understand that after a number of hours when the voltage has decreased to near end of life of the batteries, the VD will be higher across the contacts, but this will still be very small in comparison to the VD along the cable.
My question is, how do I justify this statement if my justification as stated above is not acceptable? I have contacted some of the vendors for the SSC's but they are unwilling or unable to supply the information on the contact resistance.
Any thoughts on how to answer this?
Apparently, it was decided that a statement that contact resistance of hand switches, breakers, limit switches, etc. being negligible was not an acceptable statement without some sort of supporting documentation. The basis for the assumption was that the voltage drop across these contacts would be insignificant when viewed against the voltage drop along the cable connected to these contacts.
These contacts are mostly associated with our 125V vital battery system, so I understand that after a number of hours when the voltage has decreased to near end of life of the batteries, the VD will be higher across the contacts, but this will still be very small in comparison to the VD along the cable.
My question is, how do I justify this statement if my justification as stated above is not acceptable? I have contacted some of the vendors for the SSC's but they are unwilling or unable to supply the information on the contact resistance.
Any thoughts on how to answer this?