Generator Auxiliary Modernizations

The operation of gas- as well as gas/water-cooled turbogenerators requires a number of auxiliary systems that supply the unit with operating fluids such as gases, seal oil and water. Those generators typically require explosion-protected auxiliary systems. Siemens offers a comprehensive package of explosion-protected auxiliary systems and can provide a spectrum of innovative service solutions from plant specific planning through installation and commissioning.


According to the European directives for explosion protection, known as the ATEX directives, some auxiliaries of hydrogen-cooled and water-cooled generators may be required to be explosion-protected. 


Siemens can support users conformance to ATEX requirements by performing plant specific auxiliary system assessments in order to determine and propose potentially required adaptation measures.

Our Auxiliary Modernization Concepts in Detail

Seal Oil System

The gastight and pressure-resistant enclosure of hydrogen-cooled generators has to be sealed against ambient atmosphere in order to prevent hydrogen gas leakages through the shaft seals on the exciter and the turbine end. The seal oil pressure in the seal gap is greater than the hydrogen casing pressure to prevent a hydrogen release.


Installing a customized and ATEX-compliant seal oil system from Siemens can improve generator availability. The low-maintenance unit offers optimized control capabilities and is designed for easy implementation on one skid. Single-flow or double-flow systems can be deployed, depending on the generator type.

Gas Supply System

Siemens offers a comprehensive portfolio of all required components of the gas supply system to ensure safe and reliable operation of your hydrogen-cooled generator. The gas supply system includes is comprising of the following sub systems:

Liquid Level Detector Rack

The liquid level detector rack is rack is part of the auxiliary systems of all air, hydrogen and water-cooled generators and is designed to detect the collection of liquids during operation. Smaller amounts of these liquids can be removed without interrupting generator operation. Replacing the existing liquid level detector rack with an upgraded version, can enhance reliability, simplify operation as well as increase availability. The liquid level detector rack is part of the protection system for certain generator models when these are integrated into the instrumentation and control (I&C) system.

Stator Water System

Water-cooled generators are equipped with a stator water system to allow more efficient cooling of the stator windings, high voltage bushings and the phase connectors. The stator water cooling system includes pumps, coolers, filters, monitoring for normal stator cooling water system operations and optionally a water chemistry treatment device.


The thermal losses occurring in the stator winding, high voltage bushings and phase connectors are dissipated directly by the stator water. The stator water is circulated through in a closed system by centrifugal pumps arranged in a redundant configuration and is drawn in from the stator water tank and routed to the cooling water manifold via coolers and filters.


Siemens offers customized stator water system solutions for the following two stator water bar types.

  • Stator Winding with Copper Hollow Conductors
  • Stator Winding with Stainless Steel Cooling Channels

Hydrogen Performance Plus Seal™ Improvement

Additionally to usual seal oil systems, Siemens has developed the Hydrogen Performance Plus Seal™ in order to increase safety and availability and to ensure implementation in specific generator types as a stand-alone product.


The Hydrovent™ seal is designed to hold the pressurized seal oil in the channel between the Hydrovent™ and Hydroload™ seals. A small amount of oil will flow past the Hydrovent™ seal into the bearing cavity, where it will mix with the bearing oil. The Hydroload™ seal is designed to be a means for controlling hydrogen leakage out of the generator as it is located between the seal oil and the hydrogen environment of the generator. Utilizing the latest computational fluid dynamic (CFD) modelling techniques, seal hydrodynamic features were optimized and were modified to improve pressure distribution under the seal.


In order to help hydrogen-cooled generators to reduce leakage of hydrogen and therefore increasing H2 safety, Siemens has developed improvements to the Hydrovent™ Seal (air-side) and Hydroload™ Seal.


Getting in touch

If you have any questions or would like to find out how we can help you to modernize your generator equipment, please let us know.