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Hello,
There is a lot of debate when I talk with other engineers about auxiliary contact failure. Basically, on a main breaker the PLC reads both A and B contacts to see if they are in agreement (always in opposition). Typically, when that is detected, the first course of action is to ensure a source is disconnected. Some engineers measure current to see if the breaker is closed in this condition and do not force a disconnect (which can be odd if the load profile drops, leaving the breaker assumed closed). Additionally, some engineers want to still try to control a breaker when it is in aux fail. I am curious what the industry does under this fault of a main (utility main or tie separating gen source). Is it something that happens often/is it considered?
There is a lot of debate when I talk with other engineers about auxiliary contact failure. Basically, on a main breaker the PLC reads both A and B contacts to see if they are in agreement (always in opposition). Typically, when that is detected, the first course of action is to ensure a source is disconnected. Some engineers measure current to see if the breaker is closed in this condition and do not force a disconnect (which can be odd if the load profile drops, leaving the breaker assumed closed). Additionally, some engineers want to still try to control a breaker when it is in aux fail. I am curious what the industry does under this fault of a main (utility main or tie separating gen source). Is it something that happens often/is it considered?
