Why Should I Monitor My Industrial Motor?
It is important for industrial plants to have reliable motors. The key benefits to implementing industrial motor monitoring are
- Increasing safety for workers
- Reducing unexpected failures to increase plant reliability
- Reducing unplanned outages which saves time and money
Online condition-based monitoring collects data generated during the assets normal operating conditions to get real-time awareness of problems.
Failure Modes of Industrial Motors
What causes failure in a motor's stator windings?
Failures in stator windings usually occur due to four factors
- high temperatures
- high electric stress
- inadequate ambient conditions around the windings
- mechanical issues
All of these failures have the potential to generate partial discharge (PD) and influence the life expectancy of the winding. The rate of deterioration in stator winding insulation can be tracked by measuring partial discharge activity and closely monitoring PD tendencies.
Manual Inspection vs Online Monitoring
The condition of industrial motors is usually determined through periodic manual inspections during an outage. These inspections look for obvious problems such as physical damage, frayed connectors, degraded insulation and evidence of overheated components. The disadvantage of periodic inspections is that the time interval between two maintenance activities is not always sufficient to identify developing issues prior to failure. Periodic maintenance is often performed when the asset is not in service or the plant is in outage and the actual state of the asset with respect to time and plant operation condition is often not available for diagnosis. Periodic maintenance frequently results in the maintenance of healthy assets, increasing maintenance costs, and the possibility of human error.
Online Monitoring for Industrial Motors
There are two things to consider when implementing online PD monitoring for motors:
According to IEEE, 20% of motors are taken out of service within 12 months of maintenance due to forced outages.
15% of a motor is being monitored for PD (maybe 2-3 coils). The rest is outside of the coupling capacitor zone.
Most motors have at least 6-12 RTDs already inside which can be used to transmit PD pulse data.
Use Realtime Data with Motor Monitoring
Rotating Machine Monitor
The Rotating Machine Monitor is a continuous partial discharge monitor that monitors, stores, and correlates operating dynamics. The RMM provides information as to the health of the stator winding insulation in medium and high voltage motors and generators.
Coupling Capacitor Sensor
The Coupling Capacitor is a highly sensitive partial discharge (PD) sensor used to decouple PD from the monitored conductor. Coupling Capacitors are installed as close to the winding as possible for maximum sensitivity.
The RTD-PD Module is designed to detect PD that occurs deep within the windings. Line-side coupling capacitors only identify PD levels close to the equipment terminals. When the RTD-PD sensor is used it allows a more comprehensive view of the true condition of the machine’s insulation system.
Comprehensive Partial Discharge Monitoring Approach
It is important to consider a comprehensive partial discharge monitoring approach. PD can occur in generators, isolated bus ducts, step up transformers, and switchgear. Comprehensive monitoring of the entire power train can greatly increase the ability to pinpoint problem locations. To learn more about comprehensive PD Monitoring, visit our overview page.