Along with the Battery 125 vdc ground alarm I'm getting the TCQA P125-N125 overvoltage alarm on R, S & T. Monitoring with the DIAGC program the P125V (80 vdc) is going high and N125V (40 vdc) is going low every once in awhile. So I went out to the 125 vdc power panel and monitored the voltage to ground and it was doing the same thing the DIAGC was reading. Monitoring the logic it is the DC POWER SUPPLY POSITIVE LEG GROUND LOGIC (L64D_P) this is going high causing the alarm. This is taking place while the turbine is running but with it is shut down the P125vdc to ground reads 124 vdc and the N125vdc to ground reads 3 vdc. Could there be a bad solenoid on the unit or would it be a positive lead going to ground in the system somewhere?

I would appreciate any help I could get. Thanks.

 

On our units, the best GND_IMP I've seen is 3500 kohm, that value appearing with
S125P +65 VDC
S125N -65 VDC
S125P_N 130 VDC

Typically moisture in J boxes or switch terminal boards has caused us grief in the ground impedance dept; (we get the alarm at 12 Kohm).

The DC leg ( + or - ) that is closer to 0 is the leg that has the problem (however this could be on the leg of opposite polarity if the field device contacts are closed).

Isolating the "problem child" is a matter of lifting the contact blocks from the CIM's one and a time and monitoring the GND_IMP for improvement (a off-line task) Can be rather labor intensive and frustrating... (be careful & patient).

Typically when our problems have been (finally) found, it is with a switch that is outside (rainwater infiltration) or pressure switch in the cooling system.... seal weeps glycol into the switch during extremely cold weather.

Hope this helps,
Ralph

 

Has the site recently experienced an electrical storm (lightning) or a battery charger problem?

Have you checked for AC ripple on the power supply input?

Has the battery charger been operating properly? Is the output voltage and current stable?

The presumption is that this is a Mark V being powered by a 125 VDC battery and battery charger, and that no AC-DC converter is in service in parallel with the battery/charger (AC-DC converters, called <DACA>s were supplied as options with some Mark V panels, and were usually standard on Mark V steam turbine control panels) and no AC source selector is present.

It sounds as if there is a true overvoltage condition--which is worse than the battery ground condition. At battery supply voltages in excess of approximately 140 VDC, the Mark V processor power supplies will act to shut themselves off to protect the system against damage from overvoltage/overcurrent. It's unlikely that a bad solenoid would be causing an overvoltage condition--a ground possibly, but not an overvoltage condition.

A battery gound condition is monitored by comparing the positive and negative legs of the voltage supply (the battery) to ground, so a ground on the positive leg would be indicated a low or zero voltage on the positive leg with respect to ground. It sounds as if the system has a ground somewhere on the negative leg. The Mark V Application Manual, GEH-6195 (Rev. D is the latest version), Appendix E, has a schematic representation of the 125 VDC input to the Mark V TCPD, which shows the ground reference circuit (two 33K ohm resistors across the 125 VDC input, with the "center" of the two resistors connected to ground through the BJS hardware ("Berg") jumper.

Grounds can be classifed in two groups: "hard" and "soft." Hard grounds are grounds in which the magnitude of one leg or the other of the 125 VDC supply is at or near zero volts DC with respect to ground (polarity will vary with respect to which leg is experiencing the ground). Soft grounds are grounds in which the magnitude of one leg or the other of the 125 VDC supply is at approximately 2-30 VDC with respect to ground (polarity will vary with respect to which leg is experiencing the ground). Soft grounds are almost always caused by moisture (water, lube oil, condensation, etc.) and can get worse (closer to 0 VDC with respect to ground) over time. Hard grounds which appear suddenly are almost always caused by broken conduits or heat which damages the wire/cable insulation.

When AC is powering the battery charger, the charger is supplying the current/voltage required by the Mark V and to power the 125 VDC solenoids connected to the Mark V. For a typical gas turbine-generator TMR Mark V, the off-line current required by the Mark V is approximately 3-5 amperes, and when the unit is on-line (running) the typical current draw is about 7-9 amps (the actual amount of current depends on the number and size of 125 VDC solenoids being powered at any time through the Mark V). One of the failure modes of battery chargers is for the output filter capacitors to allow excessive AC ripple on the output of the charger.

Most versions (except early vintages) of the Mark V turbine control panel included a <CPF> (Conditioning Power Filter), which the AC and DC supplies to the Mark V were connected, and the output of the <CPF> was connected to the TCPD input terminal board. The intent of the <CPF> was to meet regulatory guidelines in certain parts of the world. There are some components (capacitors, MOVs (Metal Oxide Varistors)) on the <CPF> which could fail and cause problems, though over-voltage wouldn't seem to be one of them, but a ground could be.

Troubleshooting grounds on SpeedTronic turbine control panels--especially heavy-duty gas turbine units--is NOT easy. As with any troubleshooting, the first question to ask is: What has changed? Have there been any high compartment temperature alarms (i.e., loss of cooling air fan flow in the turbine-, accessory-, or load compartment(s))? Is the turbine-generator outdoors, and if so, has the site experienced a lot of rain? Has a maintenance outage recently been completed? Wires in conduits have been damaged by high temperatures in compartments where the cooling air fan flow has been interrupted. Water has been known to enter junction boxes which are located outside and which have not been properly closed or not been properly sealed where conduits enter/exit the enclosure. (Poor construction practices were used on many sites, where conduits were connected to outdoor enclosures or junction boxes from the top, instead of from the sides or bottom....) This is why it's really important to troubleshoot grounds as soon as they are annunciated--the longer one waits to investigate the problem, the harder it is to recall what was ocurring at the time the ground was annunciated, and most grounds can be attributed to some occurrence (heavy-footed mechanic using conduit as a step-ladder during a maintenance outage; outdoor junction box or electrical panel door left open after an outage or troubleshooting allowing rain or irrigation water to enter; high compartment temperatures caused by a loss of cooling air fan flow (motor or fan bearing failure, or unintentional fire- or gravity damper closure; battery charger failure--surging output, failed output capacitors, etc.; are just some of the examples).

One more thing to remember about heavy-duty gas turbine SpeedTronic applications is that ANY circuit or device which is powered by the same battery and charger which supplies the SpeedTronic panel and which develops a ground will have the ground annunciated ON THE SPEEDTRONIC PANEL. In other words, even though the battery ground alarm is annunciated by the SpeedTronic Mark V, the ground IS NOT necessarily on a component directly connected to the SpeedTronic control panel (sometimes this is REALLY hard to convince management of... "It MUST be something connected to the Mk V--the alarm is coming from the Mark V!")

markvguy

 

The above information seems to have come from a Mark IV-equipped unit/site. Mark IV panels used an approximation of ground impedance to detect a ground. Mark V units use the magnitude of each leg of the supply voltage with respect to ground to detect and annunciate a battery ground alarm.

The terminal boards in the Mark V cannot be disconnected as they could be in the Mark IV; each wire must be loosened from the high-density terminal boards used in the Mark V (time-consuming and not fun--at all!).

The general information Ralph offers about grounds is very good and accurate!

Has the site recently experienced an electrical storm (lightning) or a battery charger problem?

Have you checked for AC ripple on the power supply input?

Has the battery charger been operating properly? Is the output voltage and current stable?

The presumption is that this is a Mark V being powered by a 125 VDC battery and battery charger, and that no AC-DC converter is in service in parallel with the battery/charger (AC-DC converters, called <DACA>s were supplied as options with some Mark V panels, and were usually standard on Mark V steam turbine control panels) and no AC source selector is present.

It sounds as if there is a true overvoltage condition--which is worse than the battery ground condition. At battery supply voltages in excess of approximately 140 VDC, the Mark V processor power supplies will act to shut themselves off to protect the system against damage from overvoltage/overcurrent. It's unlikely that a bad solenoid would be causing an overvoltage condition--a ground possibly, but not an overvoltage condition.

A battery gound condition is monitored by comparing the positive and negative legs of the voltage supply (the battery) to ground, so a ground on the positive leg would be indicated a low or zero voltage on the positive leg with respect to ground. It sounds as if the system has a ground somewhere on the negative leg. The Mark V Application Manual, GEH-6195 (Rev. D is the latest version), Appendix E, has a schematic representation of the 125 VDC input to the Mark V TCPD, which shows the ground reference circuit (two 33K ohm resistors across the 125 VDC input, with the "center" of the two resistors connected to ground through the BJS hardware ("Berg") jumper.

Grounds can be classifed in two groups: "hard" and "soft." Hard grounds are grounds in which the magnitude of one leg or the other of the 125 VDC supply is at or near zero volts DC with respect to ground (polarity will vary with respect to which leg is experiencing the ground). Soft grounds are grounds in which the magnitude of one leg or the other of the 125 VDC supply is at approximately 2-30 VDC with respect to ground (polarity will vary with respect to which leg is experiencing the ground). Soft grounds are almost always caused by moisture (water, lube oil, condensation, etc.) and can get worse (closer to 0 VDC with respect to ground) over time. Hard grounds which appear suddenly are almost always caused by broken conduits or heat which damages the wire/cable insulation.

When AC is powering the battery charger, the charger is supplying the current/voltage required by the Mark V and to power the 125 VDC solenoids connected to the Mark V. For a typical gas turbine-generator TMR Mark V, the off-line current required by the Mark V is approximately 3-5 amperes, and when the unit is on-line (running) the typical current draw is about 7-9 amps (the actual amount of current depends on the number and size of 125 VDC solenoids being powered at any time through the Mark V). One of the failure modes of battery chargers is for the output filter capacitors to allow excessive AC ripple on the output of the charger.

Most versions (except early vintages) of the Mark V turbine control panel included a <CPF> (Conditioning Power Filter), which the AC and DC supplies to the Mark V were connected, and the output of the <CPF> was connected to the TCPD input terminal board. The intent of the <CPF> was to meet regulatory guidelines in certain parts of the world. There are some components (capacitors, MOVs (Metal Oxide Varistors)) on the <CPF> which could fail and cause problems, though over-voltage wouldn't seem to be one of them, but a ground could be.

Troubleshooting grounds on SpeedTronic turbine control panels--especially heavy-duty gas turbine units--is NOT easy. As with any troubleshooting, the first question to ask is: What has changed? Have there been any high compartment temperature alarms (i.e., loss of cooling air fan flow in the turbine-, accessory-, or load compartment(s))? Is the turbine-generator outdoors, and if so, has the site experienced a lot of rain? Has a maintenance outage recently been completed? Wires in conduits have been damaged by high temperatures in compartments where the cooling air fan flow has been interrupted. Water has been known to enter junction boxes which are located outside and which have not been properly closed or not been properly sealed where conduits enter/exit the enclosure. (Poor construction practices were used on many sites, where conduits were connected to outdoor enclosures or junction boxes from the top, instead of from the sides or bottom....) This is why it's really important to troubleshoot grounds as soon as they are annunciated--the longer one waits to investigate the problem, the harder it is to recall what was ocurring at the time the ground was annunciated, and most grounds can be attributed to some occurrence (heavy-footed mechanic using conduit as a step-ladder during a maintenance outage; outdoor junction box or electrical panel door left open after an outage or troubleshooting allowing rain or irrigation water to enter; high compartment temperatures caused by a loss of cooling air fan flow (motor or fan bearing failure, or unintentional fire- or gravity damper closure; battery charger failure--surging output, failed output capacitors, etc.; are just some of the examples).

One more thing to remember about heavy-duty gas turbine SpeedTronic applications is that ANY circuit or device which is powered by the same battery and charger which supplies the SpeedTronic panel and which develops a ground will have the ground annunciated ON THE SPEEDTRONIC PANEL. In other words, even though the battery ground alarm is annunciated by the SpeedTronic Mark V, the ground IS NOT necessarily on a component directly connected to the SpeedTronic control panel (sometimes this is REALLY hard to convince management of... "It MUST be something connected to the Mk V--the alarm is coming from the Mark V!")

markvguy

 

Which tool shall we use with for check the AC ripple? Multimeter ?oscillograph? or other tools?
Could you express more detail of the function of the <CPF>? Is it a AC filter? I have seen it in the Speedtronic Mark VI.

 

(mkvguy scores a bullseye!) Ours are MKIV units, apologies for not mentioning this important detail earlier...(unaware if the difference MKIV vs MKV CTIM)

humbly,
Ralph

 

One can use an oscilloscope (best method) or one can use a true AC RMS voltmeter (Fluke 87, for example) in AC mode. To use the voltmeter, connector one lead to ground and the other to the positive DC input lead to the <CPF> and from the <CPF> to the <PD> input terminal. do the same for the negative DC input leads.

If you have a doubt about the battery charger output, shut down the battery charger and repeat the test and see if ther AC ripple decreases or increases.

Yes, GE uses the same <CPF> in the Mark VI as was used in the Mk V. The Mk VI System Guide had a very good description of the <CPF>; if you have access to the Instruction Manual for a unit equipped with a Mk VI, you can review the System Guide for details and information. Again, the purpose of the <CPF> (Conditioning Power Filter) was to try to remove ripple and spikes to meet certain regulations in certain parts of the world; rather than supply the <CPF> only for those units delivered in those parts of the world, GE just made it standard equipment for all SpeedTronic turbine control panels.

markvguy

 

Ralph, thanks for the info. There are people with Mk IV panels who read these posts and this is good information for them.

The only reason for pointing out the info was from a Mk IV was that some people would think the signals could be found on a Mk V.

Many people who upgraded their SpeedTronic control panels from Mk IV to Mk V were not happy that the same ground detection scheme was not used. In fact, on a standard Mk V, one cannot see the battery supply voltages without using DIAGC. Many put it on the bottom of their Mk IV displays and were quite accustomed checking it quickly and easily.

markvguy

 

Pls check following thing ,if posible
1st you have to identify source of negative ground.
1) Battery is grounded or field instrument
grounded.
2) If it is grounded in field instrument, it is more dangerous.

I am sure negative is grounded in field and it is solid gound during s/d and grounded wire is making on-off during running due to vibration.It will draw very high current during on-off with high frequency.

POssibility
a)Wire insultion may be demaged in conduit and it may make contact on-off during running machine
b)wire is opened any where and making contact on-off during running machine due to vibration

If it is problem as given above,it is very risky and it can lead to trip the machine on blowing of DTBA supply fuse.

 

Has the site recently experienced an electrical storm (lightning) or a battery charger problem?

Have you checked for AC ripple on the power supply input?

Has the battery charger been operating properly? Is the output voltage and current stable?

The presumption is that this is a Mark V being powered by a 125 VDC battery and battery charger, and that no AC-DC converter is in service in parallel with the battery/charger (AC-DC converters, called <DACA>s were supplied as options with some Mark V panels, and were usually standard on Mark V steam turbine control panels) and no AC source selector is present.

It sounds as if there is a true overvoltage condition--which is worse than the battery ground condition. At battery supply voltages in excess of approximately 140 VDC, the Mark V processor power supplies will act to shut themselves off to protect the system against damage from overvoltage/overcurrent. It's unlikely that a bad solenoid would be causing an overvoltage condition--a ground possibly, but not an overvoltage condition.

A battery gound condition is monitored by comparing the positive and negative legs of the voltage supply (the battery) to ground, so a ground on the positive leg would be indicated a low or zero voltage on the positive leg with respect to ground. It sounds as if the system has a ground somewhere on the negative leg. The Mark V Application Manual, GEH-6195 (Rev. D is the latest version), Appendix E, has a schematic representation of the 125 VDC input to the Mark V TCPD, which shows the ground reference circuit (two 33K ohm resistors across the 125 VDC input, with the "center" of the two resistors connected to ground through the BJS hardware ("Berg") jumper.

Grounds can be classifed in two groups: "hard" and "soft." Hard grounds are grounds in which the magnitude of one leg or the other of the 125 VDC supply is at or near zero volts DC with respect to ground (polarity will vary with respect to which leg is experiencing the ground). Soft grounds are grounds in which the magnitude of one leg or the other of the 125 VDC supply is at approximately 2-30 VDC with respect to ground (polarity will vary with respect to which leg is experiencing the ground). Soft grounds are almost always caused by moisture (water, lube oil, condensation, etc.) and can get worse (closer to 0 VDC with respect to ground) over time. Hard grounds which appear suddenly are almost always caused by broken conduits or heat which damages the wire/cable insulation.

When AC is powering the battery charger, the charger is supplying the current/voltage required by the Mark V and to power the 125 VDC solenoids connected to the Mark V. For a typical gas turbine-generator TMR Mark V, the off-line current required by the Mark V is approximately 3-5 amperes, and when the unit is on-line (running) the typical current draw is about 7-9 amps (the actual amount of current depends on the number and size of 125 VDC solenoids being powered at any time through the Mark V). One of the failure modes of battery chargers is for the output filter capacitors to allow excessive AC ripple on the output of the charger.

Most versions (except early vintages) of the Mark V turbine control panel included a <CPF> (Conditioning Power Filter), which the AC and DC supplies to the Mark V were connected, and the output of the <CPF> was connected to the TCPD input terminal board. The intent of the <CPF> was to meet regulatory guidelines in certain parts of the world. There are some components (capacitors, MOVs (Metal Oxide Varistors)) on the <CPF> which could fail and cause problems, though over-voltage wouldn't seem to be one of them, but a ground could be.

Troubleshooting grounds on SpeedTronic turbine control panels--especially heavy-duty gas turbine units--is NOT easy. As with any troubleshooting, the first question to ask is: What has changed? Have there been any high compartment temperature alarms (i.e., loss of cooling air fan flow in the turbine-, accessory-, or load compartment(s))? Is the turbine-generator outdoors, and if so, has the site experienced a lot of rain? Has a maintenance outage recently been completed? Wires in conduits have been damaged by high temperatures in compartments where the cooling air fan flow has been interrupted. Water has been known to enter junction boxes which are located outside and which have not been properly closed or not been properly sealed where conduits enter/exit the enclosure. (Poor construction practices were used on many sites, where conduits were connected to outdoor enclosures or junction boxes from the top, instead of from the sides or bottom....) This is why it's really important to troubleshoot grounds as soon as they are annunciated--the longer one waits to investigate the problem, the harder it is to recall what was ocurring at the time the ground was annunciated, and most grounds can be attributed to some occurrence (heavy-footed mechanic using conduit as a step-ladder during a maintenance outage; outdoor junction box or electrical panel door left open after an outage or troubleshooting allowing rain or irrigation water to enter; high compartment temperatures caused by a loss of cooling air fan flow (motor or fan bearing failure, or unintentional fire- or gravity damper closure; battery charger failure--surging output, failed output capacitors, etc.; are just some of the examples).

One more thing to remember about heavy-duty gas turbine SpeedTronic applications is that ANY circuit or device which is powered by the same battery and charger which supplies the SpeedTronic panel and which develops a ground will have the ground annunciated ON THE SPEEDTRONIC PANEL. In other words, even though the battery ground alarm is annunciated by the SpeedTronic Mark V, the ground IS NOT necessarily on a component directly connected to the SpeedTronic control panel (sometimes this is REALLY hard to convince management of... "It MUST be something connected to the Mk V--the alarm is coming from the Mark V!")

markvguy

Hello @markvguy, What will be the polarity of the P125V and N125v supply voltage when the BJS jumper is connected?

 

markvguy hasn't posted on Control.com for years and years.

When BJS is removed, all bets are off. BJS, when it's installed, provides a ground reference for the 125 VDC supply. USUALLY, when there's no ground reference and there's no other ground(s) on the system P125V will have some positive voltage with respect to ground, even if it's less than one volt. N125V will have some negative voltage with respect to ground, even if it's less that one volt. But, without a ground reference of any kind (more on that later) there really can't be any meaningful voltage measurement.

The reason one would remove BJS is if there is another ground detection circuit on the 125 VDC supply, like in the battery charger. And if there is another ground detection circuit on the 125 VDC supply there will more than likely be a ground reference--just like the one in the Mark* when the BJS jumper is installed. So, that would mean the P125V would be about +65 VDC with respect to ground, and N125V would be about -65 VDC with respect to ground.

If you hold a DC battery in your hand it is ungrounded. If you use a voltmeter to measure each pole of the battery with respect to ground you will see the same thing as described above when BJS is removed and there is no other ground(s) in the system (including a ground detection circuit).

What prompted you to remove BJS, or is making you consider removing BJS?