The Premium Monitoring System provides easy access to test points for diagnostics and preventive maintenance. Rope faults are reported at the bottom of the Premium Monitoring System Application screen. Careful monitoring can reveal indications that are possible fault conditions.
The ground connection test points are tied to the turbine or generator case ground.
The red Voltage test point is connected to the Shaft Voltage Metering Rope.
The green Ground Current conductor running through the faceplate allows the operator to measure ground current with a hand-held, clamp-on style ammeter. To determine the current direction, the left side of the wire is connected to the shaft grounding rope and generator shaft, and the right-hand side of the wire is connected to case ground.
The Metering Rope and Grounding Rope test points connect to each rope’s insulated wear indicator line.
For information on externally verifying waveforms using a separate scope, see EZDP-2039 Cutsforth Premium Monitoring System Signal Confirmation Procedure.
For more information, refer to the following sources:
-
Remote Meter Points Test Point Overview and Usage Instructions in the Cutsforth Manual EZDP-2007 Shaft Grounding and Remote Meter Point Installation Manual
-
Cutsforth Video Remote Meter Point Overview.mp4
-
Appropriate wiring diagram(s) for installed equipment
Cutsforth shaft grounding assembly ropes come equipped with an insulated conductor threaded into the center of the grounding and metering ropes. If the rope has not worn out to its center point, the conductor insulation will be intact and resistance between the wear indicator remote test point and ground will be greater than 500 ohms. When the conductor insulation has worn through, the resistance may vary, but a value less than 500 ohms indicates that a breach of the insulation has taken place. If you observe a value below 500 ohms, inspect the rope. It is likely that rope replacement is required.
The ROPE STATS page displays the live wear indicator value being measured. These are provided for more advanced troubleshooting. If you suspect a false rope alarm, contact Cutsforth to report the condition and learn how to avoid false triggers going forward.
Use the following troubleshooting tree to troubleshoot rope faults. Clear any rope fault that occurs on the ROPE SETTINGS page only after you have inspected or replaced the rope associated with the fault. When you click RESET, the date and time on the HOME page updates to the present time, which indicates when the rope was last replaced.
-
Using a voltmeter, confirm that the wear indicator is not worn out or shorted through the rope.
-
If continuity does not exist (500 Ohms or greater resistance), the rope is not yet in need of replacement. Continue to step 2.
-
If continuity does exist (less than 500 Ohms), the rope is in need of replacement, even if it may not look like it. After you replace the rope, press the REPLACE button on the ROPE SETTINGS page to record the date and time of replacement.
-
-
Confirm that the Premium Monitoring System is properly registering GEN ON and GEN OFF. False rope faults can be the result of the monitoring system not properly sensing the GEN OFF status.
-
If the monitoring system is not sensing GEN ON and GEN OFF properly, contact Cutsforth to discuss adjusting the GEN ON sensing thresholds. Include a screenshot of the Premium Monitoring System HOME page.
-
If the monitoring system is sensing GEN ON and GEN OFF properly, continue to step 3.
-
-
If the above recommendations do not resolve the issue, send screenshots of the Premium Monitoring System HOME page, ROPE GRAPHS page, and ROPE STATS page to Cutsforth. If the monitoring system is connected to the plant’s DCS, also include the shaft voltage zero-to-peak information from the previous 60-days along with the generator output level for the same time period.
Every generator has its own distinct set of normal operating conditions. Normal conditions on one generator may be alarming on another, even if the two units are of the same type. Plant personnel responsible for monitoring the systems should be familiar with normal average and peak levels for each unit. It is also advantageous to periodically view the waveforms on the Premium Monitoring System for each generator and watch for signatures that are markedly different from what has been viewed in the past. A change in a unit’s waveform output can be a powerful indicator that something requires attention within the generator or the grounding system.
The conditions listed in this topic may be fault indications. This is not a comprehensive list, but rather it is intended to draw attention to scenarios that can warrant further investigation.
If you notice an unusual step down in grounding current, it may be a significant event. Has something else contacted the shaft, or has a bearing lost insulation allowing alternate paths to ground? Is the rope-to-shaft contact of good integrity to allow current to flow freely when voltage is present? When grounding current is markedly different from what is normally seen on the generator and there is no correlating operating condition to explain it, the grounding system should be investigated to assure that grounding is still taking place properly. Here again, it is good to be familiar with what values are normal for your generator when it is online, on turning gear, offline, and at varying load levels.
If a significant step down in grounding current takes place in conjunction with an increase in shaft voltage, inspect the grounding assembly, grounding rope, and shaft surface for potential deterioration of the grounding rope-to-shaft connection.
Typically, shaft voltages on the generator operate in a somewhat consistent fashion and often increase or decrease in amplitude with generator output and other operating conditions. Soon after installing, you should note what normal readings are for your generator at different loads and other significant operating conditions. Knowing the difference between your generator's grounding system's readings at lowest and highest generator outputs helps you to fine tune your monitoring system's thresholds so that you are not triggering snapshots and alarms at levels that are potentially just normal periods of greater demand.
Trending values on the generator can be powerful diagnostic indicators. Long term trends and changes may give insight to potentially significant damage taking place that may not be identified by any shorter-term step-up indicator.
If you have measurements that you believe warrant further investigation, record a snapshot or set threshold levels so they capture the events in question in a waveform view. Record the date and time along with a description of related conditions, such as generator load and vibration trends at the time.
When you have concerns about the observed measurements or if you want a professional opinion on whether they represent known problems, Cutsforth can help you connect with professionals experienced in shaft diagnostic and root cause analysis.
If you experience a false alarm, record a system snapshot and send it to Cutsforth, as described in Handling False Alarms.
If you experience an error message or an application lockup, notify Cutsforth of the issue immediately. Be sure to include the following information in your correspondence. After you collect the information, reboot the Premium Monitoring System to resume monitoring operation.
-
Picture(s) of the as-found condition of the Premium Monitoring System touchscreen. If an error message is present, scroll down to view the entire message, taking multiple pictures as necessary to capture the entire message.
-
A detailed description of the as-found state of the monitoring application. For example: Are home screen values updating? Is navigation between application screens possible?
-
A detailed description of the steps taken to produce the error, if known.
-
An error log text file. Obtain the error log file using the Premium Monitoring System File Manager. See Downloading Data for instructions on how to do this. If the Premium Monitoring System File Manager is inaccessible, the user can manually obtain the Error Log.txt file from Computer > Windows (C:) > Program Files > CMS > Error Log Folder. Depending on the error experienced, a monitoring system reboot may be necessary in order to access the error log. Transfer the log from the monitoring system using a flash drive.