--- title: Shaft Grounding Rings for Wind Turbine Generators description: Wind generators are vulnerable to electrical damage to their bearings and gearboxes. AEGIS Shaft Grounding Rings are one part of the solution. image: https://blog.est-aegis.com/hubfs/20200707_145530.jpg --- [![Electro Static Technology](https://blog.est-aegis.com/hubfs/raw_assets/public/public/images/electro-static-technology.svg "Electro Static Technology")](https://www.est-aegis.com/) [![Aegis](https://blog.est-aegis.com/hubfs/raw_assets/public/public/images/Aegis.svg "Aegis")](https://www.est-aegis.com/) - [+1 866-738-1857](tel:+1%20866-738-1857) - [Products](https://www.est-aegis.com/products/) - [AEGIS® SGR – for motors under 500 HP/375 kW](https://www.est-aegis.com/product/sgr/) - [AEGIS® uKIT – for common NEMA/IEC frame size](https://www.est-aegis.com/product/sgr-ukit/) - [AEGIS® RPPR – for reactor recirculating pumps](https://www.est-aegis.com/rppr-resources/) - [AEGIS® EV and EVO Rings - for electric vehicles](https://www.est-aegis.com/product/ev-evo-rings/) - [AEGIS® PRO Series – for motors over 300 HP/225 kW](https://www.est-aegis.com/product/pro-series/) - [Shaft Voltage Testing and Accessories](https://www.est-aegis.com/product/mounting-accessories/) - [Online Product Catalog](https://catalog.est-aegis.com/) - [AEGIS® 2-Year Extended Warranty](https://www.est-aegis.com/product/extended-warranty/) - [Applications](https://www.est-aegis.com/applications/) - [Electric Vehicle Solutions](https://www.est-aegis.com/applications/electric-vehicle-solutions/) - [Food & Beverage](https://www.est-aegis.com/applications/food-beverage/) - [HVAC](https://www.est-aegis.com/applications/hvac/) - [Industrial & Chemical](https://www.est-aegis.com/applications/industrial-chemical/) - [Other Industries](https://www.est-aegis.com/applications/other-industries/) - [Power Generation & Renewable Energy](https://www.est-aegis.com/applications/power-generation-renewable-energy/) - [Transportation](https://www.est-aegis.com/applications/transportation/) - [Water Treatment](https://www.est-aegis.com/applications/water-treatment/) - [Bearing Protection](https://www.est-aegis.com/bearing-protection/) - [Shaft Voltage & Bearing Currents](https://www.est-aegis.com/bearing-protection/shaft-voltage-and-bearing-currents/) - [Fluting & Bearing Inspection](https://www.est-aegis.com/bearing-protection/fluting-and-bearing-inspection/) - [Best Practices & Installation](https://www.est-aegis.com/bearing-protection/best-practices-and-installation/) - [Resources](https://www.est-aegis.com/resources/) - [AEGIS® Bearing Protection Handbook](https://www.est-aegis.com/resources/handbook/) - [IEEE-841, Hazardous Locations, & AEGIS®](https://info.est-aegis.com/technical-codes-and-ieee-841-standards) - [Recorded Webinars Library](https://www.est-aegis.com/resources/recorded-webinars/) - [Installation Instructions](https://www.est-aegis.com/resources/installation-instructions/) - [Videos](https://www.est-aegis.com/resources/videos/) - [Technical Papers](https://www.est-aegis.com/resources/technical-papers/) - [Case Studies](https://www.est-aegis.com/resources/case-studies/) - [Specifying AEGIS®](https://www.est-aegis.com/resources/specifying-aegis/) - [Request Training](https://www.est-aegis.com/resources/training/) - [Product Sheets](https://www.est-aegis.com/resources/product-sheets/) - [About](https://www.est-aegis.com/about/) - [News](https://blog.est-aegis.com/) - [Tradeshows](https://www.est-aegis.com/about/tradeshows/) - [Blog](https://blog.est-aegis.com/) - [Where to Buy](https://www.est-aegis.com/where-to-buy/) - [Distributors](https://www.est-aegis.com/where-to-buy/distributors?type=Distributor) - [Trained Installers](https://www.est-aegis.com/where-to-buy/installers?type=Installer) - [Explosion Proof Installers](https://www.est-aegis.com/where-to-buy/installers?type=Explosion%20Proof%20Installer) - [Motors & Seals with AEGIS® Installed](https://www.est-aegis.com/where-to-buy/oems-with-aegis/) [Contact Us](https://www.est-aegis.com/contact/) - [+1 866-738-1857](tel:+1%20866-738-1857) # Improving Wind Generator Reliability with Shaft Grounding [Home](https://www.est-aegis.com/) » [Blog](https://blog.est-aegis.com/) » Improving Wind Generator Reliability with Shaft Grounding [AEGIS](https://blog.est-aegis.com/author/estaegis) Mar 18, 2026 Electric generators are essentially motors in reverse: rather than drawing power from the line and using it to do work, they are driven by an external force, such as wind, which is used to produce electric power.  Unfortunately, wind and other generators are, also like motors, vulnerable to [electrical damage caused by inverters](https://blog.est-aegis.com/three-types-of-bearing-current?hsLang=en-us).  This causes premature failure and the huge expense of unplanned downtime. ## Inverters and Stray Current ![Tiger striping on gearbox teeth](https://blog.est-aegis.com/hs-fs/hubfs/nach2stundenFlen2.jpg?width=300&height=225&name=nach2stundenFlen2.jpg) The most common types of WTGs are doubly-fed induction generators (DFIGs) and permanent magnet synchronous generators (PMSGs).  Both use inverters to regulate their power output, and DFIGs additionally use an inverter for excitation.  Unlike PMSGs, DFIGs also use gearboxes. The problem with inverters is that their high switching frequencies and unbalanced phase voltages produce stray voltage and current in their systems.  In WTGs, this can lead to electrical damage to the generator's bearings and gearboxes.  This damage accumulates and can cause premature system failure.  The image shows "tiger striping" on a gearbox, which was caused by electrical damage. In addition to inverter-induced electrical damage, wind turbines are prone to large static charges that can damage bearings and gearboxes.  This problem is [most severe in doubly-fed systems](https://www.mdpi.com/1996-1073/11/5/1305#energies-11-01305-t003), but it also occurs in PMSGs. ## Protection from Electrical Damage ![AEGIS PRO Ring installed on a WTG](https://blog.est-aegis.com/hs-fs/hubfs/20200707_145530.jpg?width=300&height=169&name=20200707_145530.jpg) Many WTGs include one or more insulated or hybrid bearings, which are resistant or immune (respectively) to electrical damage.  They are particularly effective at blocking high-frequency circulating currents.  Two insulated bearings are not a complete solution for DFIGs because there will still be stray voltage on the shaft, which, with the bearings blocked, will tend to discharge through the gearbox instead. Most WTGs also include a carbon brush to ground the shaft.  These brushes can carry high-amperage DC and low-frequency current, but they have higher impedance at high frequencies.  Since the stray current produced by inverters is largely high-frequency, they are less than a perfect match. The [AEGIS® PRO Series Shaft Grounding Ring](https://www.est-aegis.com/product/pro-series/) was developed specifically to address high-frequency stray current in large motors and generators.  AEGIS PRO Rings ground the shaft by surrounding it with millions of conductive microfibers that bleed off voltage before it builds up high enough to discharge by arcing through a bearing or gearbox. An installed AEGIS PRO is shown in the second photo - the AEGIS ring is the outermost metallic circle.  The conductive microfibers (black) are visible around the inner diameter of the ring. The best practice for electrical bearing protection is to combine these three approaches: One hybrid bearing to interrupt circulating current, a carbon brush or brushes to carry DC and low-frequency current, and an AEGIS PRO Ring to dissipate inverter-sourced high-frequency voltage. With this combination, generations and gearboxes are essentially totally protected against electrical damage to rotating equipment.  This electrical protection is, of course, only one component of reliability, but it is one less thing for wind farm managers to worry about. AEGIS Rings also come with a [2-year extended warranty](https://www.est-aegis.com/product/extended-warranty/) against bearing fluting damage. No other form of protection against VFD-caused bearing damage offers a warranty like this. [![2-Year Extended Warranty](https://no-cache.hubspot.com/cta/default/20974229/3b258d08-3058-4c7f-a866-2991b627f2e0.png)](https://cta-redirect.hubspot.com/cta/redirect/20974229/3b258d08-3058-4c7f-a866-2991b627f2e0) To learn more about AEGIS shaft grounding and best practices for electrical bearing protection - for motors and generators - [sign up for a training](https://www.est-aegis.com/resources/training/). We offer monthly live training webinars, and we can also visit your facility to review your exact application. [![Sign Up For Training](https://no-cache.hubspot.com/cta/default/20974229/69dd56c7-bbd1-4ad0-ae5c-29de322039f0.png)](https://cta-redirect.hubspot.com/cta/redirect/20974229/69dd56c7-bbd1-4ad0-ae5c-29de322039f0) [Power Generation](https://blog.est-aegis.com/tag/power-generation), [Electrical Bearing Damage](https://blog.est-aegis.com/tag/electrical-bearing-damage), [Wind Power](https://blog.est-aegis.com/tag/wind-power) ### Subscribe To Our Blog ## Read On ### [Improving Reliability in Power Generation with Shaft Grounding](https://blog.est-aegis.com/improving-reliability-in-power-generation-with-shaft-grounding?hsLang=en-us) Electric power is fundamental to the modern world. With increasing electrification in areas like... ### [Shaft Grounding Improves Electric Rail Reliability](https://blog.est-aegis.com/shaft-grounding-improves-electric-rail-reliability?hsLang=en-us) Like other[electric vehicles](https://www.est-aegis.com/applications/electric-vehicle-solutions/), electric trains offer [significant benefits](https://www.eesi.org/articles/view/electrification-of-u.s.-railways-pie-in-the-sky-or-realistic-goal) over petroleum-powered... ### [AEGIS Shaft Grounding in Wind Turbine Generators](https://blog.est-aegis.com/aegis-in-wind-turbine-generators?hsLang=en-us) Along with solar power, wind power is the fastest-growing [renewable energy source](https://www.est-aegis.com/applications/power-generation-renewable-energy/). Wind turbine... [![Electro Static Energy](https://blog.est-aegis.com/hubfs/raw_assets/public/public/images/logo-est-alt.svg) ![AEGIS](https://blog.est-aegis.com/hubfs/raw_assets/public/public/images/logo-aegis-alt.svg)](https://www.est-aegis.com) 31 Winterbrook Road Mechanic Falls, ME 04256 Phone: [+1 207-998-5140](tel:+1%20207-998-5140) Fax: [+1 207-998-5143](fax:+1%20207-998-5143) Contact Us: [Send Message](https://www.est-aegis.com/contact/) ## Subscribe to Our Emails - [Products](https://www.est-aegis.com/products/) - [AEGIS® SGR](https://www.est-aegis.com/product/sgr/) - [AEGIS® uKIT](https://www.est-aegis.com/product/sgr-ukit/) - [AEGIS® PRO Series](https://www.est-aegis.com/product/pro-series/) - [Testing & Accessories](https://www.est-aegis.com/product/mounting-accessories/) - [Custom Static Solutions](https://www.est-aegis.com/product/custom-static-solutions/) - [Product Catalog](https://catalog.est-aegis.com/) - [AEGIS® 2-Year Extended Warranty](https://www.est-aegis.com/product/extended-warranty/) - [Applications](https://www.est-aegis.com/applications/) - [Electric Vehicle Solutions](https://www.est-aegis.com/applications/electric-vehicle-solutions/) - [Food & Beverage](https://www.est-aegis.com/applications/food-beverage/) - [HVAC](https://www.est-aegis.com/applications/hvac/) - [Industrial & Chemical](https://www.est-aegis.com/applications/industrial-chemical/) - [Other](https://www.est-aegis.com/applications/other-industries/) - [Power Generation & Renewable Energy](https://www.est-aegis.com/applications/power-generation-renewable-energy/) - [Transportation](https://www.est-aegis.com/applications/transportation/) - [Water Treatment](https://www.est-aegis.com/applications/water-treatment/) - [Resources](https://www.est-aegis.com/resources/) - [Request a Training](https://www.est-aegis.com/contact/request-a-training/) - [AEGIS® Bearing Protection Handbook](https://www.est-aegis.com/resources/handbook/) - [Videos](https://www.est-aegis.com/resources/videos/) - [Technical Papers](https://www.est-aegis.com/resources/technical-papers/) - [Case Studies](https://www.est-aegis.com/resources/case-studies/) - [Specifying AEGIS®](https://www.est-aegis.com/resources/specifying-aegis/) - [Product Sheets](https://www.est-aegis.com/resources/product-sheets/) - - - Copyright 2022 Electro Static Technology. All rights reserved. Made in America. - [Privacy Policy](https://www.est-aegis.com/privacy-policy/) - [Terms and Conditions](https://www.est-aegis.com/terms-and-conditions/) - [Sitemap](https://www.est-aegis.com/sitemap/)