i want to understand the deep and detailed meaning of the master protective signal L4 in GE different control systems?

i mean, what is the meaning of L4=1 or 0 , and what is the h/w or s/w behind its value. i know , this question may be so obvious , but forgive me guys... i still new in the field.

thanx

 

I don't know how "deep and detailed" I can get, but here goes!! L4 stands for "L" logic, "4" master contactor. L4 is the master contactor, in logic, that allows the turbine sequence to run. Once the turbine has been given a start, and run permissives are met L4 will go true. It will stay true until either L4T (trip) goes true, or the turbine is given a stop, when L4 will go false as the unit shuts down and flame is lost(usually). Hopefully this helps. If you google "ANSI device designation numbers" you will get a document that shows all ANSI designations, and describes fairly well their meaning. Most GE logic is still based on the old relay type(hardware) controls of long ago.

 

It is simple. For the turbine to run, L4 should be "1". When L4=0, among many events that occur, the most critical one is to immediately cut off fuel.

To know what are the conditions that can set (L4=1) and reset (L4=0)L4 on your unit, start from L4 and trace all "set" inputs and "reset" inputs

 

Thank you guys... answers are clear and sufficient.