J
What is the exhaust spread trip logic on different GE gas turbines F5, F6, & F9? I am also looking for a trip matrix.
JG,
Actually, there is virtually no difference in exhaust spread trip logic with one little exception: F-class turbines look primarily for hot spots while non-F-class turbines look, primarily, for cold spots.
For non-F-class GE heavy duty gas turbines, most combustion problems are the result of insufficient fuel flow to one or more combustors, or cracked combustion liners or transition pieces or broken hula skirt seals--all of which result in cold spots in the exhaust. About the only way a hot spot can occur in a non-F-Class gas turbine is if a liquid fuel flow divider fails and excess liquid fuel flows into one or more combustors.
F-class gas turbines can have combustion problems where fuel is ignited into a diffusion flame in one or more combustors when it's supposed to be combusted without diffusion flame. Diffusion flame combustion is MUCH hotter than non-diffusion-flame combustion and so hot spots result. But, the same problems with low fuel flow to one or more combustor and cracked liners, transition pieces and hula skirt seals can also happen on F-class turbines. So, they can have both types of combustion problems: hot spots and cold spots more commonly than non-F-class turbines, which primarily experience only cold spots.
But, as far as the mechanism of detecting an excess exhaust temperature spread--there's virtually no difference in GE-design heavy duty gas turbine control philosophy. The Speedtronic sorts the exhaust temperatures into an array from highest to lowest, with another array that lists the location from highest to lowest. The highest and lowest values are compared to each other, and when they exceed limits and are adjacent, then a trip is initiated. There is an algorithm, TTXSPVn, which does the sorting and comparison and generates several logic outputs: L60SP1, L60SP2, L60SP3, L60SP4, L60SP5 and L60SP6. There is then some relay ladder logic that looks at the status of the logic signals and generates alarms and trips based the logic signals.
If you want to know how a specific turbine detects, alarms and trips based on exhaust temperature spreads you need to look at the TTXSPVn block, and use the Control Constants passed to the block to determine how the six logic outputs are toggled, and then look at the rungs that monitor the status of the six logic outputs to annunciate a combustion trouble alarm and a high exhaust temperature spread trip. For non-F-class turbines they are very similar (both the Control Constants and the logic rungs), and there are very slight differences for F-class turbines--but the basics are the same, with the recognition that it's more common for hot spots to develop in F-class turbines as well as cold spots.
The best thing would be to develop your own trip matrix for the machines you are working on. Sometimes small differences in Control Constants can result in large differences in operation. But, again--the basics don't change. The differences between the highest and lowest exhaust thermocouples are compared--and if the highest and lowest thermocouples are adjacent and the differences exceed setpoint, then alarms and trips are generated. The best way to understand this is to develop an understanding of the TTXSPVn block and the logic rungs that look at the six logic outputs of the block.
Actually, there is virtually no difference in exhaust spread trip logic with one little exception: F-class turbines look primarily for hot spots while non-F-class turbines look, primarily, for cold spots.
For non-F-class GE heavy duty gas turbines, most combustion problems are the result of insufficient fuel flow to one or more combustors, or cracked combustion liners or transition pieces or broken hula skirt seals--all of which result in cold spots in the exhaust. About the only way a hot spot can occur in a non-F-Class gas turbine is if a liquid fuel flow divider fails and excess liquid fuel flows into one or more combustors.
F-class gas turbines can have combustion problems where fuel is ignited into a diffusion flame in one or more combustors when it's supposed to be combusted without diffusion flame. Diffusion flame combustion is MUCH hotter than non-diffusion-flame combustion and so hot spots result. But, the same problems with low fuel flow to one or more combustor and cracked liners, transition pieces and hula skirt seals can also happen on F-class turbines. So, they can have both types of combustion problems: hot spots and cold spots more commonly than non-F-class turbines, which primarily experience only cold spots.
But, as far as the mechanism of detecting an excess exhaust temperature spread--there's virtually no difference in GE-design heavy duty gas turbine control philosophy. The Speedtronic sorts the exhaust temperatures into an array from highest to lowest, with another array that lists the location from highest to lowest. The highest and lowest values are compared to each other, and when they exceed limits and are adjacent, then a trip is initiated. There is an algorithm, TTXSPVn, which does the sorting and comparison and generates several logic outputs: L60SP1, L60SP2, L60SP3, L60SP4, L60SP5 and L60SP6. There is then some relay ladder logic that looks at the status of the logic signals and generates alarms and trips based the logic signals.
If you want to know how a specific turbine detects, alarms and trips based on exhaust temperature spreads you need to look at the TTXSPVn block, and use the Control Constants passed to the block to determine how the six logic outputs are toggled, and then look at the rungs that monitor the status of the six logic outputs to annunciate a combustion trouble alarm and a high exhaust temperature spread trip. For non-F-class turbines they are very similar (both the Control Constants and the logic rungs), and there are very slight differences for F-class turbines--but the basics are the same, with the recognition that it's more common for hot spots to develop in F-class turbines as well as cold spots.
The best thing would be to develop your own trip matrix for the machines you are working on. Sometimes small differences in Control Constants can result in large differences in operation. But, again--the basics don't change. The differences between the highest and lowest exhaust thermocouples are compared--and if the highest and lowest thermocouples are adjacent and the differences exceed setpoint, then alarms and trips are generated. The best way to understand this is to develop an understanding of the TTXSPVn block and the logic rungs that look at the six logic outputs of the block.
J
javedg
Dear CSA
Thank you. It was useful.
Thank you. It was useful.
Thank you very much
but which signals to be forced to inhibit the unit trip or delay the trip until transferring loads to the other turbine and stopping the turbine for maintenance.
but which signals to be forced to inhibit the unit trip or delay the trip until transferring loads to the other turbine and stopping the turbine for maintenance.
A. Saad,
I sincerely hope no one responds with the signal names you are requesting
Forcing logic to prevent a turbine trip can cause serious damage, personnel injury--and even death(s).
Please reconsider your plans and take safe actions to resolve the issue(s) without forcing logic to keep the unit running. Even if you know the present condition is an anomaly if you force the logic to keep running and a real condition does occur the unit would not trip--and the results can be deadly as well as costly.
I sincerely hope no one responds with the signal names you are requesting
Forcing logic to prevent a turbine trip can cause serious damage, personnel injury--and even death(s).
Please reconsider your plans and take safe actions to resolve the issue(s) without forcing logic to keep the unit running. Even if you know the present condition is an anomaly if you force the logic to keep running and a real condition does occur the unit would not trip--and the results can be deadly as well as costly.
Thank you very much
