CDVR Troubleshooting

CDVR Troubleshooting October 30, 2007

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

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


Outline (continued) • Troubleshooting – Over excitation fault – Loss of sensing – Field over current – Internal Memory Failure – Internal Watchdog Failure – Unstable Voltage – Poor Transient Response


CAUTION


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


CAT PC Metering Screen


CAT PC Protection Screen


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


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 with capacitive load or if CT connection is backwards or wrong phase rotation – High voltage may occur if operating in line drop compensation mode with a large generator load – Verify auxiliary input voltage is not too high – Replace regulator


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 not greater 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 high inductive load – Verify auxiliary input voltage is not too low – Replace regulator


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 least 6Vac 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


Troubleshooting • If No Generator Voltage is Present and an Exciter Diode Monitor Fault 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 the 24Vdc control power


Troubleshooting • If No Generator Voltage is Present and an Over Excitation Fault has Occurred: – Stop machine – Check generator and load conditions for a fault that could cause excessive 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 not so 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 to a 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


Troubleshooting • If No Generator Voltage is Present and a Loss of Sensing Fault has Occurred: – 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


Troubleshooting • If No Generator Voltage is Present and a Field Over Current Fault has 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


Troubleshooting • If No Generator Voltage is Present and an Internal Memory Failure Fault 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


Troubleshooting • If No Generator Voltage is Present and an Internal Watchdog Failure Fault 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


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


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


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


Step of Reference Test

Rise Time



Over Shoot



+/- 2%

Settling Time



Damping


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


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








PID Calculator, T’do = 2s, Te = 0.1s PID &Kg = 25, 43, 2.7 & 50


PID Calculator, T’do = 2s, Te = 0.1s PID &Kg = 25, 43, 2.7 & 200


PID Calculator, T’do = 1.5s, Te = 0.1s PID &Kg = 25, 51, 2.6 & 200


PID Calculator, T’do = 1.0s, Te = 0.1s PID &Kg = 42, 100, 4.5 & 200


“Magic” PID Values = 80, 20, 10 Kg = 50


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 T’do and Te “Magic” PID values also very good and it is simple Once “step of reference” test is suitable, verify load application / rejection performance


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 failure occurred? (i.e. sparks, re-wiring, etc.) • Is there any mechanical damage to the CDVR or mounting?


QUESTIONS?


CDVR Troubleshooting

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