Inspection & Electrical Testing
Turbine Diagnostic Services mechanical service team will disassemble the generator, inspect the generator mechanical components, reassemble, and align the generator. The Turbine Diagnostic Services Generator Specialist Engineers can conduct Inspections of the Generator Stator, Generator Field, and the Excitation System.
The Turbine Diagnostic Service generator specialist engineers are also experienced in the startup testing required for new and relocated generators. These engineers can perform synchronizing and phasing check to verify proper phase rotation of the generator leads before the initial closure of the breaker.
Turbine Diagnostic Service has engineers that are knowledgeable in the generator protection relay and tripping schemes and can provide troubleshooting and programming functions for the new multifunction electrical protection relays. Turbine Diagnostic Service has generator engineers that are experienced in all types of excitation systems, from old rotating exciters with amplidyne control, alterex, or static exciters. Turbine Diagnostic Service engineers are experienced in the static exciters from buss fed SCT-
The Turbine Diagnostic Service Generator Engineer Specialist has over 40 years of OEM generator experience. The Turbine Diagnostic Service generator specialists are knowledgeable in the generator stator with field construction and proper winding support systems. The Turbine Diagnostic Service generator specialists understand the signs of winding and support looseness also can evaluate the winding support system and core wedges for proper tightness, where repairs are appropriate.
The Turbine Diagnostic Service generator specialist engineers are knowledgeable in the operation of generators and common modes of failure and Indications of excessive electromotive forces applied to the electrical winding. These engineers are familiar with the different types of stator high voltage insulation and proper repair procedures for air, hydrogen, and water cooled stator bars.
Turbine Diagnostic Service generator engineers can provide generator field and stator winding insulation testing to determine the condition of the electrical winding insulation. Turbine Diagnostic Service can measure the low resistance of the field and stator windings and test the pole balance of the generator field when accessible.
The field windings are tested with low voltage megger checks to obtain a polarization index, and A/C voltage impedance checks. For problem fields, rolling impedance testing can be conducted to inspect for changes in the field impedance with speed, searching for step changes to associate the centrifugal force to a speed at which shorted turns occur. Turbine Diagnostic Service can conduct flux density probe testing and signal evaluation for further evaluation of field shorted turns.
The stator windings are tested with DC high voltage test sets. Initial megger testing is conducted at 2.5kv testing to determine the suitability of a generators winding for high voltage insulation stress testing. Generally a polarization index of 3.0 is desired for proceeding with higher voltage tests. Each generator phase is tested starting with a 10kv absorption test and that sets the timing of the hold points of the high voltage DC leakage testing. After the DC leakage has been tested, the final minute of testing is a one minute pass/fail HighPot test. This is a high potential test that is potentially destructive to the generator if the winding fails the insulation stress test. Turbine Diagnostic Service will only provide the generator HighPot test to the customer, when the customer agrees before the test to the Turbine Diagnostic Service voltage level to tested, and the understanding that the failure of a winding during the test is not the responsibility of Turbine Diagnostic Service, rather a failure of the winding to pass the test. This high voltage HighPot test, conducted for one minute, should be seriously considered by the customer with the ramifications of a failure before requesting the test to be conducted. The old line of justification for the utility was they would rather fail the winding during a planned outage than fail the winding in services with higher energy potential release creating an unplanned forced outage. All of this data is evaluated and incorporated into a thorough outage report.