This refers to the subject matter , seeking your help in resolution of the problem as described below.

Presently we are facing problems with the ARCNET communication between mark V and Ex-2000 system with our (FFBL Karachi Pakistan) Gas Turbine # 2 (GE MS-5001, Turbine Serial # 296835 and Generator Serial # 335 x 868). The alarm / fault code appeared on EX-2000 display is as under:

418 - LARCRECO

EX2000 details are as follows:

EX2000R
G Frame
GE Requisition - A88G464418
Shop Order - XKV593
D.M. No. R05157
Drawing No.: 259B1399AA

Details of the problem is as under:

On last Thursday, April 29, 2010 we experienced alarm messages on the Mark - V HMI as per following:
<pre>
- STATUS-S COMMUNICATION LINK FAILED 0389 &
- EX-2K DIAGNOSTIC ALARM 0426
</pre>
At the moment of alarm, no fault data of EX-2K was available on HMI and the link status was indicated as " Failed". However, 418 LARCRECO fault code was available on EX-2K local display. Therefore, fault resetting was attempted from the local EX-2K keypad twice along with physical tightness of the arcnet connecting cable at EX-2K end. As a result, the fault data appeared on HMI and was then reset from the same.

On the next day i.e April 30, 2010, the fault appeared again, this time EX-2000 control mode was also shifted from "AUTO" TO "MANUAL (FVR)" mode. The restoration attempt from Mark V HMI was not successful and the mode was restored to auto via EX-2K local key pad. Moreover, frequent switching of "Link OK" and "Failed" was also observed for a short interval of time.

Based on the above problems and in the light of recommendations mentioned in the GE manual, the interconnecting coaxial cable (with BNC Type connectors)between Mark V and Ex-2K was replaced.

After replacement of cable the system run smoothly for around 16 Hrs but the problem again appeared repeatedly on May 01, 2010. On this occasion also , the fault was only possible to reset from EX-2K local key pad as described above, followed by resetting from Mark-V HMI.

Moreover, on May 02, 2010 the system communication again failed and has not been restored to-date. However, the control mode is on "AUTO". Presently, as a next step to resolve the problem we are planning to replace the ARCNET card (DS200ACNA) of Ex-2K.

Your expert opinion / recommendations and clarifications are requested for the following:

- Other probable causes of communication failure and recommended actions for resolution of fault.

- Reason for shifting of AVR mode from AUTO to MANUAL.

- With the communication link failed, is it possible to control the voltage ( or reactive power sharing in case of parallel operation) from EX- 2 K keypad? If yes, please provide details.

- Is there any hazard in operation of one gas turbine with communication link failed in parallel operation with other similar gas turbine?

Moreover, please note that we have experienced the same problem several times in the last years with the same 418 (LARCRECO) fault message but in those cases the fault data was visible at Mark V HMI and was successfully resetted from the same.

Your expert opinion and cooperation regarding the above problem is requested, please.

Appreciate early response.

Thanks

Best Regards,
WAS

 

I'm hoping MIKEVI will add the benefit of his experience here, as I believe they just went through some EX2K communication issues at his site not too long ago.

Amazingly enough, I have seen and heard of more failures of BNC tee connectors and right-angle connectors, and even a couple of termination resistors than I would ever have imagined would have occurred. One would think those things are pretty simple devices, but, they do seem to fail for whatever reason.

I believe one of the reasons they fail is because there are apparently connectors designed specifically for ARCnet LANs, and they're not readily available. But, they do look exactly like the same connectors used for Ethernet 10-Base2 LANs. I think the wrong connectors are quite frequently purchased and used, and they fail over time in the wrong application.

I've personally had problems with an intermittent terminating resistor, which really caused a lot of grief.

Also, I have seen some extremely poorly terminated coaxial cables. Amazingly enough, I've seen a lot of the twist-on BNC connectors used in power plants around the world! (And I'm pretty sure they're not designed for ARCnet LANs, nor for critical applications.)

I'm no Status-S expert nor EX2K expert, but I'm pretty sure that the Mark V is the device which physically communicates with it's "assigned" EX2K and then sends the data to/from the operator interface/HMI. The problem might even be with the CTBA card in the Mark V. Or, the TCCA card (I think that's the one the CTBA communicates with; look at the Signal Flow Diagrams in Appendix D of the Mark V Application Manual, GEH-6195, to be sure).

Please write back and let us know how you fare with your troubleshooting!

 

Dear WAS,

we recently encountered a problem with our ARCNET communication between our EX2000 and the MKVI unit. Our configuration is different from yours since you are MKV, not MKVI but I will recap what we went through/found. In the beginning we were encountering intermittent problems with communication between the MKVI and the EX2000. The problem was very intermittent and never lasted long enough to allow diagnosis. Sometimes the EX2K would set a Fault 418, sometimes not. Since the MKVI does not talk ARCNET we have an intermediate controller that talks ARCNET and converts to EGD data for the MKVI.

We started by using a scope to look at the communication on the ARCNET network, we did this right at the ACNA card (DS200ACNA). This proved that we had good communication out of the EX2K and the ACNA card was ok. In your case I would suggest the same test. I also would suggest pulling and reseating the ARCPL cable that goes from the LDCC card to the ACNA card, there is some special grease supplied with the new ACNA card that is supposed to be applied sparingly (just a little) to these terminals. This was something we did, but it did not help in our case.

As CSA says I would do all you can to verify your ARCNET network cables, TEE's, 90's and terminating resistors are ok. Because our ARCNET network is very small we were able to replace and swap cables/tee's etc to try and cure the problem. I do not know if your ARCNET is setup in a ring configuration or a bus configuration, if its a "ring" there should be two paths from the MKV to the EX2K, so the chances of 1 failed cable stopping communications should be small, unless one side has been failed for a long time and was just working on the other.

I assume from your post that you do not have an operator interface(OC2000) for the EX2K, just the keypad on the EX2K and the MKV HMI. If that is the case you still can control the EX2K from the keypad while communication is down. Like you, in our case communication finally failed completely, but the excitor still ran, we just could not adjust voltage/vars from the HMI. Assuming your keypad is enabled then pressing the "INC" or "DEC" keypad buttons should allow you to control voltage/VARS.

In the end our problem was a failed arcnet card on the intermediate controller which you do not have. I think in your case your next best bet is to replace the ACNA card as you are planning. Although I would suggest a scope check if possible.

I learned a lot during this "lesson". I learned that in our case the EX2K would just broadcast all the data on the "Status S" pages assigned to it, there was no CRC or message checking back from the MKVI. I learned that not a lot of people know a lot about the EX2K, at least to the depth that I needed at the time. But I did find help in lots of places, good luck to you.

Anyway I hope some of this might help you, please write back with more questions/answers as they come up, I like others would be very interested in what you find as the failure.

 

My question is regarding the intermediate controller part number, are you running a DS215UCIB with a PC104 Arcnet Card mated through an IS200PANA board? Or are you using some other intermediate controller?

 

Dear RBG,

not sure if your post is aimed at WAS or me, but in my case with the MKVI and EX2K I am running DS215UCIB with a PC104 Arcnet Card made by contemporary controls mated through an IS200PANA board.