NERC Compliance Generator Testing

Satisfy Mandates to Produce Accurate Models

As a transmission system is operated close to its stability limits, it is necessary to confirm proper operation of generator controls for optimum performance. This includes identifying and correcting misoperating equipment and tuning controls, thereby improving the performance of the power system during contingencies. Generator testing is recognized as practical, having minimal intrusion on plant operations and yielding significant benefits to generating plants. Two distinct benefits are derived from testing:

  1. Improved predictability of performance of the power system during contingencies.
  2. Evaluation of equipment performance to recommend retuning, if necessary, resulting in the improvement of power system performance following major disturbances.

Example Customer Request

A utility requests a transient response test on its excitation system. The objective of the engagement is to obtain values of the gains and time constants describing voltage regulation loops and maximum field voltage capabilities. This excitation system data must be reviewed periodically in all machines to assure that field-adjustable elements are set properly.

Typical Work Scope
  1. Test Performed - The test is initiated by tripping the generator from a leading power factor at a stator current of about 20% of rating.
  2. Response to Findings - Test recordings are analyzed to derive a computer simulation model that will reproduce the excitation system response to the generator trip.
  3. Action Recommendation - A recommendation is made, such as replacement of old excitation system model with the new model.
Performance Period

A complete series of tests can be executed in as little as one day for most hydro plants, smaller steam plants and motors. The schedule for testing of large steam units is determined by the operating constraints of the boiler and the turbine.

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