Back for another question. This forum seems to be the only source of reliable information on the MK-V that I have found. Tech manuals are severely lacking.
I am trying to better understand the operation of our ST admission/extraction valve during a period of low loading. A little back information:
Plant info:
Cogeneration Plant
7EA GE Gas Turbine (DLN1+)
MKV GE Control System
GE Steam Turbine
When lowering MW to our dispatched rate, we are placing the ST in IPC and then placing the GT in preselect load and lowering to the desired MW output. Tonight for instance, we are dispatched to 71 MW. That puts us at about 45MW on the GT in preselect load, and 30MW on the ST in Plant MW control.
My question is this. During our descent to 71MW, while lowering MW on the GT, our ST reaches V3 uncontrolled extraction pressure, which if I understand correctly just means that the ST is no longer able to maintain the desired LP extraction setpoint. This isn't really a big problem for us, as we can utilize an IP-LP reducer to maintain the LP pressure as long as the IP extraction pressure isn't compromised. I am trying to understand the process the MK-V uses to determine when to shed LP, IP, or MW load to maintain the inlet steam pressure. Also, I am curious what the V3 valve bias does? Operators have noted that when the valve bias reaches 100%, things start going south. If you know what I mean. Sorry to put it that way, but I can't really describe it better than that.
Hopefully, someone out there (paging CSA...lol) will have a link to a training course on the ST controls of a MK-V, because as I stated, the tech manuals I have access to are extremely lacking...
I am trying to better understand the operation of our ST admission/extraction valve during a period of low loading. A little back information:
Plant info:
Cogeneration Plant
7EA GE Gas Turbine (DLN1+)
MKV GE Control System
GE Steam Turbine
When lowering MW to our dispatched rate, we are placing the ST in IPC and then placing the GT in preselect load and lowering to the desired MW output. Tonight for instance, we are dispatched to 71 MW. That puts us at about 45MW on the GT in preselect load, and 30MW on the ST in Plant MW control.
My question is this. During our descent to 71MW, while lowering MW on the GT, our ST reaches V3 uncontrolled extraction pressure, which if I understand correctly just means that the ST is no longer able to maintain the desired LP extraction setpoint. This isn't really a big problem for us, as we can utilize an IP-LP reducer to maintain the LP pressure as long as the IP extraction pressure isn't compromised. I am trying to understand the process the MK-V uses to determine when to shed LP, IP, or MW load to maintain the inlet steam pressure. Also, I am curious what the V3 valve bias does? Operators have noted that when the valve bias reaches 100%, things start going south. If you know what I mean. Sorry to put it that way, but I can't really describe it better than that.
Hopefully, someone out there (paging CSA...lol) will have a link to a training course on the ST controls of a MK-V, because as I stated, the tech manuals I have access to are extremely lacking...