CDVR Troubleshooting

7/28/2019 CDVR Troubleshooting

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EAME/CIS TC Conference EP/Petroleum - Malaga, October 2007

CDVR Troubleshooting

October 30, 2007


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Outline

Troubleshooting

If operation is not as expected

Excitation loss (reverse kvar)

Generator over voltage

Generator under voltage

No generator voltage

Exciter diode monitor fault


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Outline (continued)

Troubleshooting

Over excitation fault

Loss of sensing

Field over current

Internal Memory Failure

Internal Watchdog Failure

Unstable Voltage

Poor Transient Response


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CAUTION


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Troubleshooting

If Operations is not as Expected:

Check for Alarms or Shutdown Faults

If Fault LED is lit Continuously Alarm Output Drive Active

If Fault LED is Flashing Shutdown Output Drive Active

Open Communications with CDVR to determine what Alarm /Shutdown is active

Alarm Signal Indicator Visible on all Screens

Go to Metering Screen, look at Alarms area

Check Programmable Settings


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CAT PC Metering Screen


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CAT PC Protection Screen


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Troubleshooting

If Excitation Loss(Reverse kvar) has Occurred:

Verify programmable settings are consistent with application

Check wiring of generator voltage (P12 10 to 12) and Current

Sensing (P12 1 & 2) Check phase rotation, if not consistent with wiring diagram,

modify connections

Check other paralleled generators or voltage sources for over

voltage (this can cause reverse var flow into generator) Replace regulator


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Troubleshooting

If Generator Over Voltage has Occurred:

Check wiring of generator voltage sensing (P12 10 to 12)

Verify that the generator over voltage fault settings are correct

Verify that voltage adjustment is not set too high

Verify that sensing PT (if used) has correct turns ratio

Verify that sensing PT fuses (if used) have not opened

High voltage may occur if operating in droop mode withcapacitive load or if CT connection is backwards or wrong phaserotation

High voltage may occur if operating in line drop compensationmode with a large generator load

Verify auxiliary input voltage is not too high

Replace regulator


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Troubleshooting

If Generator Under Voltage has Occurred:

Check wiring of generator voltage sensing (P12 10 to 12)

Verify that the generator under voltage fault settings are correct

Verify that voltage adjustment is not set too low

Verify that the generator is running at rated speed

Verify that the under frequency setpoint (knee frequency) is notgreater than generator frequency

Verify that sensing PT (if used) has correct turns ratio

Check for correct input power

Low voltage may occur if operating in droop mode with highinductive load

Verify auxiliary input voltage is not too low

Replace regulator


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Troubleshooting

If No Generator Voltage is Present:

Check wiring

Verify that the generator is running at rated speed

Verify that residual voltage applied to the power input is at least6Vac or greater

Verify that the fuse is not open

Verify that CDVR is connected to 24Vdc control power

Verify that common alarm / shutdown LED is not flashing


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Troubleshooting

If No Generator Voltage is Present and an Exciter Diode MonitorFault has Occurred:

Stop machine

Insure power input to CDVR has been removed, unplug P6 Refer to generator manual for instructions on checking the

rotating exciter diodes

If no fault is found with rotating exciter diodes, the EDM trip value

may be too low Increase EDM trip value to a level greater than the ripple current

under normal operation

If rotating exciter diodes are at fault, repair, reinstall P6 then

reset the CDVR using the Fault Reset contact input or cycle the24Vdc control power


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Troubleshooting

If No Generator Voltage is Present and an Over Excitation Fault hasOccurred:

Stop machine

Check generator and load conditions for a fault that could causeexcessive exciter field current

If no fault is found, reset the CDVR using the Fault Reset contact input

or cycle the 24Vdc control power

Verify the over excitation settings are properly adjusted for the

generator, set slightly above the requirement of the application but notso high as to render the protection ineffective

If an exciter diode fault has occurred, the instantaneous trip value of

28A may have been reached. The EDM fault will not indicate this, due toa 5 sec time delay

SR4 &SR4B generator require up to 12Adc for full load. A 10 second

setting is required to insure 300% short circuit requirements


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Troubleshooting

If No Generator Voltage is Present and a Loss of Sensing Fault hasOccurred:

Stop machine

Check wiring Check generator and load conditions for a fault that could cause

sensed voltage to be low

If sensing potential transformers are used, verify that they are

functional and have not blown a fuse Once fault is repaired, reset the CDVR using the Fault Reset

contact input or cycle the 24Vdc control power


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Troubleshooting

If No Generator Voltage is Present and a Field Over Current Faulthas Occurred:

Stop machine

Check wiring Check generator and load conditions for a fault that could cause

a field over current

A field over current fault occurs when output current exceeds

28A (approximately) Once fault is repaired, reset the CDVR using the Fault Reset

contact input or cycle the 24Vdc control power


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Troubleshooting

If No Generator Voltage is Present and an Internal Memory FailureFault has Occurred:

Try resetting the CDVR using the Fault Reset contact input or

cycle the 24Vdc control power If after resetting the CDVR, if another Internal Memory Failure

fault occurs, replace regulator


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Troubleshooting

If No Generator Voltage is Present and an Internal Watchdog FailureFault has Occurred:

Try resetting the CDVR using the Fault Reset contact input or

cycle the 24Vdc control power If after resetting the CDVR, if another Internal Watchdog Failure

fault occurs, replace regulator


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Troubleshooting

Unstable Voltage:

Verify that the governor for the engine is operating properly

Verify that the sensing and power leads are connected securely

Verify that the CDVR stability range is set to the proper range Verify that the stability level (Kg) is properly set


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Troubleshooting

Poor Voltage Response to a Transient Load:

Verify that the governor for the engine is operating properly

Verify that the CDVR stability range is set to the proper range

Verify that the stability level is properly set Tune the CDVR for the application


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Troubleshooting

CDVR PID Tuning:

Perform a step of reference test with 1 or 2% steps

Look at terminal voltage response with chart recorder

Determine if voltage response is acceptable Rise time

Over shoot

Settling time

Damping

If not acceptable, tune the CDVR for the application

Once step of reference test is suitable, verify load application /rejection performance


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Step of Reference Test

Rise Time


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Over Shoot


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Settling Time

+/- 2%


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Damping


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Troubleshooting

CDVR PID Tuning:

Examples of step of reference test results

Tests performed on 300kW, 240V, 60Hz AREP generator

Factory defaults PID calculator

Magic PID values = 80, 20 and 10


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Default PID = 200, 600, 30 with Kg = 50


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PID Calculator, Tdo = 2s, Te = 0.1s

PID &Kg = 25, 43, 2.7 & 50


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PID Calculator, Tdo = 2s, Te = 0.1s

PID &Kg = 25, 43, 2.7 & 200


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PID Calculator, Tdo = 1.5s, Te = 0.1s

PID &Kg = 25, 51, 2.6 & 200


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PID Calculator, Tdo = 1.0s, Te = 0.1s

PID &Kg = 42, 100, 4.5 & 200


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Magic PID Values = 80, 20, 10

Kg = 50


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PID Tuning Conclusion

Must adjust Kg to achieve best results

Factory Default Values result in OK performance

PID Calculator gives very good results but must know Tdo and Te

Magic PID values also very good and it is simple Once step of reference test is suitable, verify load application /

rejection performance


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Information Needed If Replacement of CDVR is Selected

When sending back a CDVR, please provide the following:

Detailed statement of problem including

Symptoms of the failed CDVR

Genset configuration and ratings Operating Conditions (kW, voltage, current etc)

Run time

Anything unique about the installation

Did anything of significance occur just before the failureoccurred? (i.e. sparks, re-wiring, etc.)

Is there any mechanical damage to the CDVR or mounting?


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QUESTIONS?

CDVR Troubleshooting

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