The typical epoxy-mica insulation system of rotating machines is a 'forgiving' insulation system. Due to this electrical stability, partial discharge activity acts as an indicator for a variety of defect mechanisms. Besides the mere normal thermal aging, further problems, such as end winding contamination, bar or overhang vibrations, deterioration of grading layers, loose wedges, or large internal delamination can be classified by analysis of the properties of phase-resolved partial discharge patterns. PD testing and monitoring on generators and large motors offers a detailed stator winding condition assessment. This helps avoiding unplanned outages as well as scheduling efficient maintenance turn arounds.
Power Diagnostix offers various instruments for continuous monitoring, schedule-based routine testing and in-depth analysis of rotating machinery. The instruments and their control software were continuously improved, based on the feedback and requirements of the end users.
Permanently installed partial discharge couplers greatly simplify periodical on-line testing using the ICMsystem without any interruption or downtime. Continuous online PD monitoring with a permanently installed ICMmonitor helps optimizing maintenance intervals and reducing costs, while improving the level of equipment dependability.
Tan Delta Measurements
The loss factor or tan delta measurement allows an evaluation of the condition of the complete insulation of a stator winding. All resistive losses between HV potential and ground are measured. Typical values are in a range of 10-3 to 10-2.
The TDAcompact is a digital tanδ and power factor analyzer for off-line dielectric testing to assess the overall healthof the insulation system. Its fiber optic signal transmission simplifies connection even on grounded equipment. The unit comes with reference capacitor and can be combined with any external high voltage source.
Partial Discharge Monitoring
Based on the stand-alone ICMmonitor unit connected to an individual machine, larger networks supervising a multitude of generators in combined-cycle thermal power plants or pump storage hydro power plants have been realized. Such networks include full control of the local instrument via global Intranet access as well as visualization of the monitoring data in monitoring centers. The ICMmonitor software offers automated scanning, pattern acquisition, and analysis of the trending data, while the ICMserver software operates in the background to supervise the communication between the individual instruments and data servers.
High voltage motors are the main assets to keep compressors, cooling pumps, extruders and or large fans running in refineries, oil and gas plants, chemical and petrochemical industry. Here, unplanned outages can cause immense losses. Not only for the HV motor in particular, but, to clean pipelines with remaining product or compressor and extruders that have stalled by motor failure. Further, such motors act as auxiliary drives in thermal and nuclear power plants to run the (emergency) cooling system, for example. Here, failure of a motor stator winding can cause critical subsequent damage. Given the typical 5-yearly outages for such setups, permanent installation of capacitive couplers offers periodical online PD measurements, and, hence, the possibility for an accurate and short follow-up. For the most critical trains continuous monitoring can be installed from the early beginning.