I'm Zihni.

I work in a Power Plant. We have 2 Frame 9E gas turbines and Control systems are Mark V.

I want to learn L3CP contact. This contact is located in circuit L3STCK0 coil. What is this contact? If give me information about this contact, I will be happy.. Thanks..

 

Dear Zihni.

Signal L3CP.
"L"=Logic not a hardware signal but logic.
"3" Ansi designation for checking or interlocking relay.
"CP"= Customer permissive

So L3CP is usually connected to a digital input, its signal will usually be l3cp, lower case is supposed to be a hardware input.

The signal usually comes from a distributed control system(DCS) to signal the turbine that the balance of plant(BOP) equipment is in a condition ready for the turbine to be started. L3CP is usually in a "start check rung" whereas this signal must be true before the turbine is ready to start.

Hope this helps.

 

Thank you very much..

I want to know there is some contacts, for examples L4CT, L52B_SEL, L4_XTP

If you are explain I will be pleased..

 

Hello, Zihni, (from Turkey, if I recall correctly)

I just wanted to add a couple of things to MIKEVI's good explanation, to ensure your happiness.

L3CP, which means "Customer Permissive to Start", is <b>usually</b> a logic signal driven by a discrete (contact) input. If it is, in fact, a discrete input on the turbines at your site you should find it listed in the I/O Report (F:\UNITn\TC2KREPT.TXT) and in the I/O Assignment file (F:\UNITn)IO.ASG), where "n" is 1 or 2 depending on how the operator interfaces are configured.

[The lower-case "l3cp" designations really didn't get started until the advent of Mark VI Speedtronic turbine control systems.]

The <b>INTENT</b> of L3CP is that the "Customer" would supply a contact or circuit that would be
closed when it is permissible to start the gas turbine (this particular input is usually <b>NOT</b> inverted). That's why the contact is in the L3STCK0 rung--it's part of the Start-Check permissives.

This signal is commonly used on most every GE-design heavy duty gas turbine control system--even if the Customer doesn't provide a contact/circuit for the purpose. What's usually done in that case is that a hard-wire jumper (link) is usually placed across the two discrete input terminals and left there indefinitely, which makes L3CP a logic "1" and satisfies the Start-check permissive.

This is one of my least favorite discrete inputs, because, usually no one at the plant knows what "drives" this input (presuming there is actually a contact/circuit connected to the input). So, when there's a problem with this contact/circuit finding the "source" of the signal can be VERY time-consuming.

The commissioning TA/engineer <b>should have</b> edited the I/O Report to put some kind of information in there about where the signal originates in the Customer's plant (from the DCS; or from a switch on an operator's desk; etc.) at a minimum. He/she could also have edited the I/O Assignment file to include similar information in the comments section of that discrete input. And finally, he/she could have edited F:\UNITn\LONGNAME.DAT to put some helpful information in there for future reference. But, usually, that didn't happen, unfortunately.

So, have a look at your I/O Report or I/O Assignment file(s), and you should find the input listed there, which should direct you to the proper discrete input core (<CD>, or <QD1>) and the proper terminal board (DTBA or DTBB) and terminals. Then, you can look at the terminal board and see if there are wires connected to the input or if there is a jumper. That will tell you if there is an external contact/circuit that needs to be located or a possible problem with the wiring between the terminal board and the source of the contact/circuit. If there's just a jumper there, then no contact/circuit was provided by the "Customer."

The worst thing that a commissioning TA/engineer could have done (and I've seen this happen twice, unfortunately) is to invert the input when no contact/circuit was available instead of putting a jumper across the terminals. Why is this bad? Because, when there is AC voltage noise being induced on the discrete input wiring one of the things that can happen if it's really bad is that open circuits can appear to "toggle" (change state)--even if there's nothing connected to the input terminals! But, there are usually other Diagnostic Alarms associated with this problem, and usually 125 VDC battery grounds/alarms, too.

Hope you're happy!

 

Thank you very much..

 

Mark V,

If you work at a site with a Mark V there should be a file in the unit-specific directory (F:\UNIT1, for example) called LONGNAME.DAT. That file should have some good information about signal names. Sometimes though, it doesn't have any information, and as is usually the case, the information provided can be lacking, or even flat-out wrong. But, it's what the OEM provides, and that's the best place to start.

L4CT is another of my least favorite signals, because it is another generic signal that is available to the Customer for tripping the turbine. It is usually driven by a discrete (contact) input that's closed to allow the turbine to run and when the contact/circuit opens the turbine is to be tripped.

Examples of trips connected to this input include boiler drum level hi-hi, and/or boiler drum level low-low, and natural gas compressor tripped, etc. There can be multiple contacts in series/parallel configuration to this one discrete input--and it's not usually known or understood by plant personnel. The Speedtronic commissioning TA/engineer should have marked-up the I/O Report or the comments section of the I/O Assignment file with some useful information, but usually didn't. So, it's usually very difficult to find out what signals in the plant are connected to this input.

[NOTE: This input (L4CT) is not to be used for Emergency Trip Push-buttons; they are to be connected to a different circuit.]

L52B_SEL is a discrete (contact) input to the <P> core that's used to tell the <P> core (specifically the TCEA cards in a Mark V) when the generator breaker is closed. It must be a direct-acting contact from the breaker itself--not from an auxiliary relay, as it used as part of the synchronizing self-adapt correction feature (if enabled). It is separate from L52G or L52GX, which usually come from an auxiliary relay, not from contacts on the breaker it self. If the Mark V is used to synchronize more than one breaker, L52B_SEL can be used as part of the second breaker synchronizing scheme.

L4_XTP is a signal that is called the "cross-trip" signal. When L4_XTP is a logic "0" the emergency trip relays of the <P> core can be energized to allow the fuel shut-off valves to be opened. It is the inverse of L4; when L4 is a logic "1" L4_XTP will be a logic "0", and when L4 is a logic "0" L4_XTP is a logic "1".

L4_XTP is a signal that is used when checking the operation of the fuel shut-off valves when the unit is not running, or when manually stroking or calibrating fuel shut-off valve LVDTs. It must be forced to "0" when checking the fuel shut-off valves, or when stroking or calibrating fuel shut-off valve LVDTs. (Some gas fuel control valves also require forcing L4_XTP to a logic "0" to allow off-line stroking or LVDT calibration.)

Hope this helps!