Generator Stator Shields (GSS) for ENERCON WEC’s
The primary purpose of the GSS (patent pending under patent number EP24180567.0) is to prevent water and moisture from entering
the generator. Water and moisture in the generator stator is the main source of generator short-circuits.
Historical development of the Generator Stator Shield (GSS)
“In 2014 I was assigned as O&M manager for a customer in Norway who at that time had 30 Enercon E70 turbines in their portfolio.
The main technical challenge was re-occurring generator failures. At the time the customer suffered 3-5 generator failures annually.
Each generator failure would lead to an extended downtime, significant loss of production, costly repairs and an increasingly dissatisfaction of
the insurance company. Once a generator have suffered a damage the windings in the stator becomes exponentially more brittle and will be
more prone to a short-circuit in the future, even a generator had to be de-rated in order to operate. Without a doubt after several generator
failures the stator lifetime expectancy will de-crease.
In 2016 the customer terminated the EPK with Enercon. After going from an EPK to a Support Agreement it was decided to replace the Enercon
“rain-gutter” with the newly invented Generator Stator Shields (GSS).
On some turbines it was opted to only install 5 GSS elements and in 2023, 2 of those turbines have suffered minor stator winding damages. This
is caused by up draft water spray entering the bottom half of the generator. On all the turbines fitted with only 5 GSS elements it has now been
decided to fit 9 GSS elements to provide the full optimal stator protection.
Since 2018 not one single turbine with the full 9 element GSS in the customers portfolio have suffered a generator damage, which is a
remarkable proof that the likelihood of Generator Stator damages is significantly reduced.
The GSS have some additional upsides:
✓ With the full 9 element GSS it is clear the airflow over the generators is reducing the generator operational temperature.
✓ The full 9 element GSS is a physical barrier that prevents foreign objects from hitting the generator.”
Leif Kyhl Johansen
Examples of the consequences of a generator short circuit failure
The GSS has some additional major upsides:
There are cooling fans mounted in the nacelle and the positive pressure in the nacelle forces the air to flow over the generator stator out into the hub. The GSS will direct the airflow and ultimately increase the air flow velocity exactly where the cooling is most wanted. This will lead to generator temperature reduction during production.
GSS tests have been performed which demonstrates the GSS ability to reduce the generator stator temperature.
Below green graph shows the generator stator temperature before the GSS is installed.
Below blue graph shows the generator stator temperature after the GSS is installed.
We have also been made aware of an incident where a broken bracket in the hub hit the generator windings which then led to a short circuit.
The GSS would have reduced the possibility of this broken bracket (or any other loose object) hit the generator stator.
Worst case scenario a broken bracket can lead to a total loss of the generator.
Picture to the right is of an actual generator winding damage sustained by a lose object.
The GSS shown to the right is our first-generation version.
The second generation GSS to the right is made of a material of significantly higher heat resistance properties and furthermore isthe inside ispainted with topcoat.
The second generation GSS was developed to cater the market where the ambient temperature is higher than the Northern European market.
Second generation GSS in the workshop for test assembly.
A GSS fitted which shows the stator is protected from water & lose items entering the generator.
