Testing Spark Plugs of Mark-V Control System

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  • 8/11/2019 Testing Spark Plugs of Mark-V Control System


  • 8/11/2019 Testing Spark Plugs of Mark-V Control System


    reference/output; this is for DLN primary combustion zone re-ignition during a normal fired shutdown. It is a second set of contacts from another relay output (contact output) in the Mark V wired in parallel with the "primary" relay output used duringstarting. I believe this is the L2TVX1A output, but, again, that's just a guess without being able to see the CSP at your site to becertain.)

    The spark plug bodies must be firmly grounded to non-painted metal. (They are bolted to the combustion cans using metal boltswhich serve as the ground during normal operation; usually just laying them on the galvanized metal grating outside the turbinecompartment will suffice.) Personnel working in the area where the spark plugs are laid in the open should be notified and staya couple of meters away from the spark plugs when they are going to be energized.

    Many times the safety procedures for an outage require that the AC source for the spark plugs be isolated (by opening ancircuit breaker or lifting a wire somewhere in the low voltage circuit (120 VAC or 220 VAC, depending onlocale/configuration). I've been to several sites where the maintenance technicians forgot that the AC power to the plugs had

    been isolated during preparations for the outage and were claiming the Mark V wasn't working correctly when they forced thelogic signal to energize the spark plugs because they weren't sparking.... The Mark V just switches an AC source which isexternal to the Mark V to energize the spark plug transformers. The Mark V does NOT provide the AC sources for the spark

    plug transformers; it simply serves to switch the AC source on and off (by closing or opening relay contacts). The AC sourcemust not be isolated during this test.

    Hope this helps--wish I could be more specific about the exact logic signal which drives the relay output at your site, but it'salways best to refer to the documentation for your site (including configuration files).

    Posted by pascal on 22 December, 2013 - 7:14 am


    Just check on your wiring list (or interconnecting diagram) where is your ignition transformer connected it will give you thename of the signal to force, but usually forcing L2TVX will do the job all other signals are some "spare" one (at the time therewere two ignition transformers such as with Frame3 GT).

    I am just a little worry about you last signal L2TVX1A_REF, is your card the VPRO card connecting the ignition transformer?and in that case it would be useful to also force the signal L4_XTP (also sometime named L4NEG) but usually ignitiontransformer are connected to TRLY card.

    Posted by CSA on 22 December, 2013 - 2:31 pm


    Mark V's don't have TRLY cards; Mark VI's and Mark VIe's do.

    The "standard" for discrete outputs for all digital Speedtronic turbine control panels (if adhered to by designers and field people) is to use a separate logic signal name to "drive" an output and NOT to use contacts associated with that logic signalanywhere in logic. That way, when an output is forced the force does only one thing: acts on the output. And does NOTaffect anything else in logic/sequencing/control.

    Sometimes, but not always, the separate logic signal is driven, in a separate rung, by the "main" logic signal, but frequently--especially in Mark V--the output logic signal coil is in configured to be in parallel with the logic that drives the "main" logicsignal (L2TVX in this case). So, just forcing L2TVX will likely NOT force L2TVX1.

    And, if the original poster looks in the CSP no contacts associated with L2TVX1 (and possible L2TVX1A) should be found anywhere else in the CSP--because they are only driving outputs.

  • 8/11/2019 Testing Spark Plugs of Mark-V Control System


    I, too, was surprised to see the L2TVX1A_REF signal, but I wouldn't be surprised to find the signal in a Mark V that'srecently been "upgraded" to a Mark Ve or whatever they're calling it these days, or as some "artifact" of some unused logicsignal that somehow was mistakenly left in the CSP for that site. But, without being able to see the CSP and know moreabout the "Mark V", it's impossible to say for sure.

    In the Mark V, trip solenoid outputs driven by the

    core frequently had _REF signals associated with them, but the spark plug transformers were not usually driven by


    Posted by shyam on 25 December, 2013 - 2:21 am

    Thanks for your valuable reply. for a couple of days i am not in the site so i could not check the TC2KREPT.TXT and IO.ASG files. but as per wiring drawings it is showing there is 2 relays named-L2TVX1 and L2TVX1A. the control signals(relay drive) for L2TVX1 connected to the, DTBD - 61&62 and the control signals (relay drive) for L2TVX1Aconnected to the,

    PTBA- 65&66.

    230V AC taken from the external source and going to the ignition transformer through these relays. ie, phase is goingthrough one relay and neutral is going through another relay. Still i am confusing about the last signal "L2TVXIA_REF".

    Expecting your feed back..

    In my view i think i will have to force both L2TVX1 & L2TVXIA signals to make spark plug activation. can you givefeedback?

    Posted by CSA on 25 December, 2013 - 1:56 pm


    Okay, so part of the mystery is solved. L2TVX1A is assigned to an output of

    core, which explains theL2TVX1A_REF (the Mark V uses the _REF signal as a check to see if the output has, in fact, been energized--or de-energized--when commanded).

    I don't have access to a Mark V Application Manual, GEH-6195, at this writing to know exactly which output is beingused from the

    core. My concern stems from the fact that AC is necessary for the spark plug transformers, and manyof the

    core outputs are hard-wired/configured to pass DC (for trip solenoids). So, I'm a little confused about how the

    panel is configured.

    I would suggest actually tracing wires in the panel to be certain one wire is actually physically connected to the

    core;as was said before, it's extremely common to find documentation that was never updated during installation/commissioningto reflect wiring changes made to the Mark V Panel.

    If, in fact, the spark plug transformers are connected to the

    core the task of energizing them is going to be quite a bitmore complicated. Presuming one leg of the spark plug transformer supply IS connected to the

    core you will need toensure that the emergency trip push-button circuit connected to the

    core is complete (no P/Bs are latched in the trip

    position; many LOTO procedures require at least one E-Stop P/B to be latched and "locked" in the tripped position.

    Next, you will need to force the following signals to the following logic states:

    L2TVX1 = " 1"L2TVX1A = " 1"L4_XTP = " 0"

  • 8/11/2019 Testing Spark Plugs of Mark-V Control System


    If you don't force L2TVX1A_REF the output will work, BUT you will get a Diagnostic Alarm output feedback notagreeing with reference or something to that effect. You could also for L2TVX1A_REF to a logic "1" to prevent thatDiagnostic Alarm, but it's an unnecessary step.

    Without being able to look at a Signal Flow Diagram (in GEH-6195) I can't understand how an AC signal can be passed through a DC circuit (I'm assuming the

    core has a TCTG card, which most GE-design heavy duty gas turbine Mark V control panels use). So, I'm a little leery of whether or not the documentation actually reflects the currentwiring/configuration of the Mark V--but stranger things have happened!

    I would suggest, again, that someone take the time to physically trace the spark plug transformer wiring in the Mark V panel, draw a schematic of the circuit, and use this in the future when wanting to perform this test again. It will likely savea lot of effort--and frustration. This could be part of a procedure that outlined what needed to be forced to what logicstate--again, this could be very helpful in the future.

    Please write back to let us know what you find and how the test worked (what you had to force; etc.).

    Posted by shyam on 26 December, 2013 - 11:25 am

    We successfully tested both the spark plugs simultaneously by forcing L2TVX1, L2TVX1A and L4_XTP. Thanks for your support and feed back.

    Posted by CS A on 26 December, 2013 - 1:47 pm


    You are most welcome!

    Thanks for the feedback, also. 'Feedback is the most important contribution!'(c) here at control.com. It is whatdistinguishes control.com from a lot of other Web-based forums. When posters who receive assistance fromresponders on control.com provide feedback it lets other people who read these posts--now, and in the future--if theinformation provided was helpful, or not (as the case may be).

    I want to be very clear about this particular post, though. It is NOT typical for either leg of the spark plug power source to be connected through the

    core of a GE Speedtronic Mark V turbine control panel, so, it's not generallyrequired to force L4_XTP in order to be able to energize the spark plug transformers/spark plugs.

    It's unclear (to me, anyway) why any leg of the spark plug power source would be assigned to the

    core, unless itwas something demanded during commissioning or by some local technical code or regulation. Even so, it's not clear how an AC source can be routed through the

    core trip solenoid outputs. (I do NOT have access to Mark V SignalFlow Diagrams at this writing, so I'm not clear what function PTBA-65 & -66 are connected to in the


    Again, congratulations on t