The IDOS MarkV (TMR) of one of our Frame 6B GTs (T4) seems very strange from last few years (from 2021 may be). Last time when we replaced <R> TCEA and TCDA with same EEPROMs (due to DCC IO CARD OBJ#4 and OBJ#15 reset with so many input and out diagnostic alarms), all got A7 status. Then everything was fine. From last week we faced the same thing again in <R> and <S> both at standby condition of the same unit. Replaced IONET cable, everything came back to A7 status. But the problem came back on the next day!!! For test purpose We picked both TCEA and TCDA of R and S and installed to another Unit T3 (Standby), T3 behaved normal!!! Why this is happening?

Note: Measured voltages at test points of each core TCPS, DCC, TCEA, and found all normal.

 

@SaberMPS,

1) Have you ever judiciously applied conductive grease to the ribbon cable ends and stationary cable pins (such as for the power cables supplying power to each of the I/O cards of each core) when replacing cables AND cards?

2) What is the temperature AND humidity of the location where the Mark* V turbine control panels are located?

3) Is it dusty in the location where the Mark* V turbine control panels are located?

4) Do you have a periodic maintenance procedure procedure for judiciously applying conductive grease to all ribbon and cable connectors and/or pins of each and every card (I/O card; I/O terminal board; etc.) on a regular basis (for example, every other year or so)?

I don't remember exactly which OBJ numbers are associated with which I/O cards without digging into notes on an old computer, BUT I can tell you that there are cables that connect each control processor to its associated TCEA and TCDA I/O cards running from the TCQC card to the TCEA card to the TCDA card(s) in <QD1> (and <QD2> if the panel uses a <QD2>. I believe that's the IONET cable you are referring to.

The combination of heat, humidity, dust and other gases/contaminants (we have no idea where these units are located and if they are in proximity to some kind refinery or chemical process plant or even a cement plant) makes for nuisance and intermittent problems over times. It is a well-known fact (identified in a GE PSB (Product Service Bulletin) issued many years ago that the materials used in the making of the pins and connectors of the Mark* V are prone to corrosion and "plating" of the metals and recommending the judicious use of conductive grease to prevent corrosion/plating. It lead to GE providing tubes of conductive grease in the boxes with spare/replacement cards.

BUT, keeping the turbine control panels clean and operating in a proper environment (the Air Conditioners provided with GE-supplied PEECC enclosures ARE NOT for human comfort--they are to maintain a dry environment inside the PEECC enclosures to protect electronics components (so lowering the thermostat temperatures to make it more comfortable for humans in the compartment can lead to moisture condensation on printed circuit cards and contactor magnet faces, etc. especially if the machines are located in a humid environment).

Also, many sites did not properly seal the area below the Mark V turbine control panel where the cables enter/exit the bottom of the Mark* V turbine panel. If there is a cable "vault" below the PEECC and there is any standing water in the bottom of the vault moisture from that water will be drawn up and into the Mark* V turbine control panel and other electrical equipment in the PEECC and cause rust and other issues--like corrosion and plating of connectors and pins of electronic equipment.

Proper maintenance of the environments (temperature, humidity, and dust control) where electrical and electronic equipment is located is VERY important for long-term reliability and availability of electronic equipment. Improper maintenance has led to all manner of nuisance and intermittent problems with electronic equipment as well as medium-voltage contactors, contacts and terminations.

Without knowing a LOT MORE about the location and condition of the equipment at your site these are the most common issues causing nuisance and intermittent problems. The judicious (meaning not just applying gobs of conductive grease) use of conductive grease, and periodically checking the cables/connectors for the presence of grease and removing any excess and/or applying new grease is critical to maintaining reliable equipment operation and performance.

Those control panels, if they use DCCA cards, are pretty old (probably installed in the mid-1990's) and if they haven't been maintained properly then it wouldn't be unusual or even unexpected for nuisance and intermittent problems to be appearing and possibly even becoming more and more "common" without some kind of mitigation. Even properly powering-down the turbine control panels and other sources of voltage/current (PT (Potential Transformers; Current Transformers (if connected to the Mark* V)) and simply logically and methodically unplugging and reconnecting each and every cable connector three or four times to try to clean/displace any corrosion/plating on the connectors/pins would be highly recommended. Applying a thin film of conductive grease to each and every cable connectors (the female connectors, specifically) when doing this would be even MORE highly recommended. Using a non-conductive vacuum brush (available from many electronics suppliers, including Amazon) to clean any dust from the faces of the cards in the panel would also be very highly recommended; difficult to do on the upper-most row of processors in the panel--but not impossible.

So, there are the most common issues and some proven solutions/actions for improving reliability--without knowing a LOT MORE about the condition and maintenance and location of the Mark* V turbine control panels.

By the way, the <I> is simply a method for monitoring, controlling and configuring (and troubleshooting) a Mark* V turbine control panel. (A VERY old method, by the way.) It DOES NOT perform any control or protection functions (unless it employs a very complicated scheme of adjusting the load of two or more machines, a very complicated and almost never-used control scheme that had some serious shortcomings and was not included with many systems). It's a necessary interface for easy human monitoring and control of a machine controlled by a Mark* V turbine control system, but all the monitoring and control functions of a Mark* V driving a generator can be done using the <BOI> in conjunction with the controls on the Generator Control Panel door (meters and switches and knobs). Not very simply or easily--but it is possible and has been done in extreme situations when the <I> was not available. Thank you for telling us the operator interface of the Mark* V turbine control panels at your site are <I>s, but it was not necessary to know for this situation as described.

 

@WTF?

Sorry for being late.

• Recently, we did not apply grease while replacing cards. However, in 2022, we applied conductive grease to the male pins using grease taken from an old GE pack/box that had been supplied since 2001. At that time, we were unaware of its expiry date. This conductive grease was applied only once during its entire service life.

• The TCC room temperature is within a suitable range and typically remains around 24–25°C, although humidity has not been measured. A comparative temperature reading was taken: this unit’s TCQA_CJ_Q is 29°C, while the corresponding readings of the other two units are 27°C and 28°C.
  
  The average local humidity is around 74%, but during the monsoon season it can rise to 90%.
  
  Please note that an additional 3-ton AC unit is operating alongside the original GE-supplied AC system, as the original unit has aged.
  
  If I am not mistaken, the cable vault of the TCC was flooded once, possibly in 2016 or 2017. There is insulation damage on many field cables beneath the floor tiles. Normally, we avoid disturbing these cables because doing so may trigger a 125V DC ground alarm.
  
  
• No.

• We don’t have any periodic maintenance procedure, even we didn’t know about it.

On 2022, we cleaned all boards, cards by dry plastic brush, applied contact cleaner on pins, then after drying up applied grease on IONET, DENET, ribbon, power cable’s pins of R, S and T, QD1 and P. But from TB to Card, we did not apply grease.

I hope this will clarify some of your queries.

 

@SaberMPS,

Most of my questions were intended to cause you to think about the environment where the Mark* V turbine control panel(s) are located and the kind of maintenance and housekeeping they have experienced over their life.

Nothing more. Nothing less.

These are the most common causes of nuisance and/or intermittent problems. I forgot to mention improper storage of spare cards. AND, some of the components on the printed circuit cards (capacitors; resistors; etc.) do not last indefinitely (many capacitors on Mark* V power supply cards have failed because of the nature of materials used and simply life and the conditions they have been exposed to--both in use and during storage).

MOST nuisance and intermittent Mark* V problems *NOT ALL--but many!) can be traced to housekeeping and the use of conductive grease. You also gave no indication of the nearby industrial facilities--if any--or the proximity to high-traffic roads. (Cement plants in humid environments can be particularly problematic if good housekeeping and maintenance procedures are implemented and followed.) MANY cable vaults have some source of near constant water incursion, often because of the pipes used for in-ground conduit and normal cathodic erosion or breakage. Many earthing (grounding) grids installed at combustion turbine locations were not properly installed, and the soils can be highly corrosive to earthing grids buried in them, especially in humid environs.

That's all I can offer.