Partial Discharge - Rotating Machines

Megger offers a range of continuous monitoring solutions as well as schedule-based routine testing and an in-depth analysis of rotating machinery. Our instruments and software have been meticulously refined based on the feedback and requirements of our end users, giving you the most efficient and user-friendly tools to help you with your testing and analysis.

To that end, our ICMsystem simplifies periodic on-line testing without any interruption or downtime, thanks to its permanently installed partial discharge couplers. Additionally, our ICMmonitor is ideal for continuous on-line PD monitoring as it helps to optimise maintenance intervals and reduce costs, while improving the level of equipment dependability.

Tan delta, or loss factor, measurements evaluate a stator winding’s insulation by measuring all resistive losses between the high voltage (HV) potential and earth/ground. Typical values are in the range of 10-3 to 10-2. This testing effectively detects various insulation issues, including contamination, delamination, semiconducting and stress gradient coating quality, void content, partial discharge damage, and impregnation process quality.

For accurate tan delta testing, we have the TDAcompact. This digital capacitance and tan delta analyser is ideal for off-line dielectric testing, enabling you to assess the overall health of the insulation system. Its fibre optic signal transmission simplifies connection, even on grounded equipment, and it comes with a reference capacitor. What’s more, it can be combined with any external high voltage source.

Tan delta measurements complement partial discharge measurements. One limitation of tan delta results is that the test provides an overall, combined representation of the health conditions of all the insulation included in the test, rather than the health of individual pieces of insulation. Therefore, as the amount of insulation under test increases (i.e., as in larger rotating machines), it becomes more challenging to identify localised problems. Problems are revealed by an elevated tan delta value. A further limitation is that when a problem is indicated, the test alone does not reveal the exact nature of the issue.

In contrast, partial discharge measurements can both reveal problems and characterise their nature. Moreover, PD testing provides the earliest detection of dielectric problems.

Capitalizing on the strengths of both tests, Megger offers the ICMflex - a unique measurement system that performs PD and tan delta measurements simultaneously, increasing efficiency and precision

PD monitoring is the preferred approach for critical rotating machines, where continuous monitoring and early fault detection are essential. Megger’s ICMmonitor provides comprehensive visibility into stator insulation health and seamlessly integrates with existing systems, unlike other monitoring solutions with limited inspection capabilities.

Using the standalone ICMmonitor unit for individual machines, we have developed larger networks that can supervise multiple generators in combined-cycle thermal power plants or pump storage hydro power plants. Such networks include full control of the local instrument via global Intranet access and allow monitoring data visualisation in central monitoring centres. The ICMmonitor software offers automated scanning, pattern acquisition, and data trend analysis, while the ICMserver software operates in the background to manage communication between individual instruments and data servers.

High voltage (HV) motors are essential assets that keep compressors, cooling pumps, extruders, and/or large fans running in refineries, oil and gas plants, and chemical and petrochemical industries. As such, any unplanned outages can cause immense losses. These not only affect the HV motor itself, but they also lead to issues such as stalling compressors and extruders due to the subsequent motor failure.

Furthermore, HV motors act as auxiliary drives in thermal and nuclear power plants, for example, to run the (emergency) cooling system. Here, the failure of a motor stator winding can subsequently cause critical damage. Given the typical 5-yearly outages for such setups, the permanent installation of capacitive couplers offers periodic on-line PD measurements that enable you to gain accurate readings regularly, allowing you to act on any faults immediately. Indeed, for the most critical motors, continuous monitoring can be installed as early as possible.