We have 3 GE Frame 9e machines at our site. I am not an E&I guy but since I am in technical services, so I am concerned about out gas turbine tripping so frequently due to EX2000.

Here is what we get from the alarm,

On 6th Jan:

Machine tripped on EX2000 trip alarm at base load of 133 MW.Following alarms enunciated.
Master1- Generic EX2000 trip, Master protective signal, Master protective /turbine trip, Generator
protection trip,EX2K trip,EX2K diag alarm,CTG1C Generator differential trip. Fault code at MarkV EX200
screen was 28 and at EX2000 local panel was 29.

On 7th Jan:

Machine tripped at 134 MW on EX2000 fault. Following alarms and indications noted & View ST saved.
Indication at DGP: 87B, Fault code at Mark V EX2000 screen: 28, Fault code at EX2000 screen(Local):
29. Alarms at MarkV. EXC1-EV17 Master1- Generic EX2000 trip, EXC1_EV19 Master1-field breaker
feed back, Generator protection trip, EX2K diag alarm, EX2K trip.

Machine tripped on several other occasions and each time the card was resetted. DGP was resetted and even changed. The problem was found by our electrical staff (what they claim) but still the machine tripped.

Now we contacted the OEM and they asked us to start the machine and keep it at a preselect load of 80-87 MW.

Can I get a clue from the members what is happening here and why the exciters protection is activating, although our electrical crew claims that they have checked everything but the problem is a GHOST TriP

 

Have you checked the master card of DGP?

 

> Have you checked the master card of DGP?

Yes Sir, master card was checked and even the whole card was replaced from spare but nothing is working.

The machine again tripped in the morning.

GT1C was running at preselect load (90 MW) with all parameters normal when it tripped on “Generic EX2000 trip” alarm followed by generator protection B 87G. Fault code at MarkV EX2000 screen was 28
and at local EX2000 panel was 29 & 16. Following important alarms noted at MarkV.

EXC1-EV17 Master1-Generic EX2000 trip, EXC1_EV19 Master1-field breaker feed back, EXC1_EV29 Master1, L4T Master Protective signal, L4T Master Protective \ Turbine Trip, EXC1_EV18 Master1-generator breaker feed back (from EX2k), Generator protection trip, EX2K diag alarm, EX2K trip

 

When this trip event occurs, what is the frequency of the grid? Is it stable or is it fluctuating? If it's fluctuating, how much is it fluctuating?

What is the VAr indication immediately prior to the trip event? What is the power factor immediately prior to the event?

You keep saying that EX2000 Alarms 28 & -29 are being annunciated when this trip occurs, AND you have also mentioned protective "relay" B 87G.

What are EX2000 Alarms 28 & 29? You must have a cross-reference or something to indicate what these drop numbers mean. Most EX2000 displays on GE Mark V operator interface that I have seen will include a line of text for each EX2000 alarm, just as is done on the Process- and Diagnostic Alarm windows.

You say the B 87G relay is also indicating a problem. "B" indicates either a back-up DGP or redundant 87G relay. If the "A" or primary 87G relay isn't indicating a problem, this might indicate some problem with the "B" device or its inputs or outputs.

You have <b>NOT</b> provided a chronological list of the alarms immediately prior to the trip event and a list of the alarms that were annunciated immediately after the trip event. You have also seemingly included "events" interpreted as alarms. Please provide a chronological list of alarms/events for three seconds prior to the trip event and three seconds after the trip event.

Provide a chronological list of alarms prior to and just after the trip event. And have a look at what actuates the B 87G "relay" and tell us, and tell us what EX2000 Alarms 26, -28 and -29 are.

When writing to ask for help, please tell us what you have done to troubleshoot the problem, and the results of that troubleshooting. It's a waste of everyone's time for us to ask you to do something and then you to tell us, "We already tried that."

I'm not an EX2000 expert, but I would have to believe that there are some conditions that will cause the EX2000 microprocessor to initiate a turbine trip. And, I would imagine that someone has a list of these conditions, and probably one of them is Alarm 28 and/or -29, possibly -16. If there's no list of conditions (which there should be!) then someone should be using the EX2000 software interface to obtain the list and post it for all operators and their supervisors. As well as a cross-reference for EX2000 alarm drops.

This thread is very typical of people blaming the control system for a problem with the inputs from field devices, or for loose wires or terminal screws. A control system is only as good as its inputs, and right now it seems no one is interested in determining if the inputs are working correctly or even what the alarms that are being annunciated by the control system are trying to tell the reader.

If this is a serious problem (and it sounds like it is), please have a qualified service individual visit the site to help with the problem. Here at control.com we can provide help, and the best and quickest help we can provide is when the originator posts as much information as possible and tells us what's been done to troubleshoot the problems.

But for serious issues requiring timely responses it's best to obtain the on-site services of a knowledgeable and qualified individual if none is available on site.

 

Dear MZI, I am looking at a list of EX2K alarms. Most of them are very cryptic, they do not provide a clear description of the problem or the resolution. I am not sure why you see a different alarm number on the MKV than what appears on the EX2K screen.

Alarm #16 refers to a "normally open interlock that is closed. It is an offline trip. This is most likely occurring after the unit has already tripped.

Alarm #28 refers to an "illegal run command", but says this alarm is no longer used.

Alarm #29 refers to the "control on loop open" and indicates it is a trip. This sounds like a good possibility in your case. I do not have access to my prints at this time. You really need to be able to look at your EX2K prints, and generator protection prints and find out what inputs and outputs are terminated to the EX2K. Sometimes it is hard to tell if the EK2K is tripping the unit, or if the EX2K is being tripped by the 86 relay.

As CSA suggests I would be looking at what trips the 86 relay, and trace that back. I will try to look for my drawings and report any more information that might assist.

 

Dear MZI,

I looked further at my prints for the exciter. I do not know if your site wiring will be exactly the same, so you really need to refer to your prints. But there is an enable circuit for the exciter, it enables a "K86" relay on the power supply board. Wires land on the 2TB terminal board screws #1 and #8, and in my case go to normally closed contacts on 86G. This enables the exciter to "run".
In this case it sounds like a device is tripping the 86G lockout, which in turn trips the CTG and the exciter.

I hope you have the time to investigate and answer back, I would be curious to know what devices at your site can roll the 86.

In your post you refer to alarm for "generator protection B 87G", and also for "CTG1C Generator differential trip". This sounds like you really need to look at your protection relays, I should hope there are some flags set that would point to some type of fault, possibly for some phase differential, which may be related to a fault on the generator, or from outside on the grid.

Again as CSA asks it would curious to know what was happening on the grid prior to each of these events.

 

Based on you info and limited knowledge in EX2000, I think the problem probably has something to do with high exhaust temperature (HET) relay operated. It could trip on sustainable HET or it could trip on high temperature spread.

Even if I'm right the mechanic that triggers such tripping can be more complicated. It serve no purpose to talk about it unless my initial guess is correct.

 

Dear All,

I thank all of you for posting. Our Electrical Engineer is back onsite and also OEM rep is here. They are currently doing their testing.

I'll fetch information from them and will get back to you.

I have also shared the forum post with them and your replies are of a great help to our engineer. Lets wait and see what the OEM rep suggests.

Regards,
MZI

 

Whats up now?

 

>Whats up now?

The DGP was faulty and the whole DGP was replaced.

THe OEM adviser saved the day for us.

Thanks all again for the inputs.

Regards,

M/ Zeeshan IQbal