Generator Service Capabilities

With over 150 years of experience, Siemens-Energy is a world leader in generator technology and has manufactured many of the largest and most efficient generators in the world.

With Siemens-Energy as your service partner, you can have the full benefits of the expertise of our turbine-generator factory personnel, design engineering, service engineering groups, and our regional management and service expertise. We are knowledgeable of potential turbine-generator issues through significant fleet experience and have developed an enormous backlog of field processes, procedures, tooling and trained personnel to quickly address them.

Our Generator Service Capabilities in Detail

Completion of Lockout/Tagout procedure prior to entering the unit.
Electrical isolation and grounding of stator winding.
Implementation of Foreign object incident control.

Inspection of Stator Winding Components:

  • Visual inspection of the overall appearance of the stator windings. Looking for signs of dirt and/or oil, corona, tape separation, foreign objects, overheating, deterioration and any abnormalities.
  • Inspection of top and bottom diamond spacers for greasing and wear.
  • Inspection of coil to brace fillers for dusting or greasing.
  • Inspection of support ring spacers for dusting or greasing. Including bottom coil support ring, inboard bottom coil support ring, middle coil support ring, and top coil support ring.

Stator Core:

  • Inspection of the stator iron for general appearance and visible discoloration and evidence of hot spots or mechanical damage.
  • Inspection of the slot wedges for signs of looseness, dusting, or greasing, and migration of the wedges and/or wedge filler.
  • Inspection of the back of the core for fretting between building bolts,
  • Laminations and any other unusual circumstances.

Inspection of Abnormal Conditions:

  • Inspection for the evidence of OCP Erosion. (Outer Corona Protection)
  • Inspection for Coil Side Filler Migration.
  • Inspection for Wedge Movement, Greasing and Migration.
  • Inspection for evidence of electrical distress, deterioration and break down.

Main Leads and Bushings:

  • Inspection of the porcelain insulators.
  • Inspection of the interface of porcelain to flange seal inside and outside of the lead box, where accessible, for signs of greasing, gas or oil leakage.
  • Inspection of the leads for condition of insulation taping and voltage break down.

Generator Rotor:

  • Visual Inspection of the Retaining Rings.
  • Visual Inspection of the Radial Leads.
  • Visual Inspection of the Rotor Body.

  • AC Maintenance and Overpotential Tests
  • DC Maintenance and Overpotential Tests
  • Dielectric Absorption
  • Leakage Voltage
  • Insulation Resistance of Each Phase 
  • RTD and T/C Insulation Resistance
  • Through Bolt Insulation Resistance
  • Thermocouple Continuity
  • Tube-to-Tube Resistance  (If present)
  • Tube-to-Copper Resistance  (If present)
  • RTD Internal Resistance Measurements
  • Phase Resistance Measurements 
  • Transposition Test   (If applicable)
  • Stator Core SMCAS Test

  • Coil Vent Tube Pressure Drop
  • Parallel Ring & Bushing  Flow Test
  • Stator Test Wedge Measurements
  • Building & Through Bolt Tightness Check
  • Radial Clamp Tension Test
  • Top Coil Support Ring Checks
  • Bottom Coil Support Ring Checks

  • Impendance Test
  • Pole Balance
  • Insulation Resistance of Winding
  • Rotor Winding Resistance Measurements

  • Radial Lead Assy. Leakage Test [Nitrogen]
  • Radial Lead Seal Leakage Test [Helium]
  • Hardness Testing
  • Blower Hubs Hardness (solid shaft only)
  • Retaining Rings Hardness Testing

RTD Element Resistance Test

Thermocouple Continuity

RTD or T/C Insulation Resistance

Diode Wheel:

  • Fuse Testing
  • Diode Forward/Reverse Resistance
  • Capacitor Fuse Check (Mark III only)
  • Diode Wheel to Heat Sink Insulation Resistance
  • Diode Wheel to Exciter Shaft Insulation  Resistance
  • Diode Wheel-to-Diode Wheel Insulation Resistance

Exciter Rotor:

  • Winding Resistance
  • Winding Ring Insulation Resistance
  • Ground Detection Ring Insulation Resistance
  • Continuity of Ground Detection Ring to Armature
  • Rotor Ground Protection Insulation Resistance
  • Slip Ring to Ground Insulation Resistance
  • A Ring to B Ring Insulation Resistance

Exciter Stator Assembly:

  • AC Impedance & Pole Balance Test
  • Winding Copper Resistance
  • Winding Insulation Resistance
  • Field Current Limiting Resistor Resistance

PMG Assembly:

  • Winding Copper Resistance
  • Winding Insulation Resistance

Siemens Energy has +30 years of providing robotic In-Situ generator inspections known as FAST Gen. The three inspection scopes offered are Visual, Siemens Multifrequency Core Assessment System (SMCAS™️) and Wedge Tightness. The visual inspection utilizes on board camera(s) that are capable of digitally recording video and still images used to look for visual signs of overheating, excessive relative motion, ventilation blockages in stator or rotor vent paths and possible foreign objects. SMCAS™️ is a test that evaluates core laminations for circulating currents the same as EL CID. A feature that SMCAS™️ offers is the ability to digitally overlay previously recorded SMCAS™️results to compare for trending over the life cycle of the stator core. Wedge Tightness testing is used to assess the loading force of generator stator wedges and is a helpful tool to predict a possible outage of sufficient length when loose or loosening stator wedges need to be replaced.

With 3 decades of field use comes significant innovation. Siemens Energy at the Pittsburgh Service Center has begun to incorporate additive manufacturing to the latest design updates that allow for more rapid customization of inspection components that can be attached to the modular base of the FAST Gen tooling or even complete standalone solutions. This enables the Pittsburgh Service Center to help meet an ever-increasing demand of non-OEM inspection requests where generator access may offer unique obstacles.

  • Fiber Optic End Winding Vibration System
  • Rotor Flux Probe Monitor
  • Frame Foot Loading
  • GenAdvisor

  • Evacuating water from the generator windings is necessary for performing some electrical tests on the stator windings system
  • Extremely useful in Leak Detection and Investigations
  • Vacuum decay can be affected by moisture in system
  • Helium leak detection can be affected
  • Stator winding leak repairs
  • Aids in Long term storage of or layup of the stator water cooling system

Loop Testing is performed to identify and restore insulation between core laminations, (if interlaminar insulation has broken down).

  • Standard Loop testing is performed at an input  frequency of 60 Hz and a voltage of 4,160 VAC  (This tests the generator at rated flux density).
  • Once energized, the stator core is scanned with a Thermographic camera for evidence of hot spots.

High Frequency Flux Test

  • Magnetization of the stator core
  • Production of magnetic / core losses to detect hot spots in fault locations by eddy currents at 480 VAC inputs, rather than at 4,160 VAC.
  • Lower input Voltages and Currents allow for smaller cable sizes and customer demands.
  • The VFPS, (Variable Frequency Power Supplies) can be run as stand alone units, or run in parallel for larger generators if needed.
  • Thermovision scans are then performed similar to the 60 Hz loop tests but at variable frequencies, (usually around 500 Hz), to locate hot spots in the stator core iron. 

  • Power Factor Testing (Tan δ)
  • Partial Discharge Testing
  • Doble Testing

Modal analysis determines the natural frequencies and mode shapes of turbine-generator static structures across the relevant frequency ranges of operation. Testing ensures that during operation the structure is tuned away from resonant conditions that increases structure fatigue and chance of failure. Modal analysis can be performed in the field or the factory.

Modal analysis applications include:

  •  Generator end windings
  •  Generator pedestals
  •  Generator frame
  •  Generator lead box
  •  Operational deflection shape (ODS)
  •  Blade frequency testing
  •  Turbine structural shaker test
  •  Rotor modal analysis
  •  Baffle plates
  • Maintenance Winding Repairs 
  • Generator Rewedge
  • Generator Core Retightening
  • Generator Core Core Repairs 
  • Rotor Modifications & Improvemnts
  • Specialty Off Line Diagnostics
  • Automatic Voltage Regulator Repairs
  • AVR Retrofit
  • NERC Testing
  • Exciter / Collector Maintenance
  • Generator Rewinds
  • Generator Core Replacements
  • Generator and Rotor Modernizations

Further comprehensive Siemens Generator Service Capabilities can be offered upon request.

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.