IEC 61400-21:2008

FOREWORD
INTRODUCTION
1 Scope
2 Normative references
3 Terms and definitions
4 Symbols and units
5 Abbreviations
6 Wind turbine power quality characteristic parameters
  6.1 General
  6.2 Wind turbine specification
  6.3 Voltage fluctuations
      6.3.1 General
      6.3.2 Continuous operation
      6.3.3 Switching operations
  6.4 Current harmonics, interharmonics and higher frequency
      components
  6.5 Response to voltage drops
  6.6 Active power
      6.6.1 Maximum measured power
      6.6.2 Ramp rate limitation
      6.6.3 Set-point control
  6.7 Reactive power
      6.7.1 Reactive power capability
      6.7.2 Set-point control
  6.8 Grid protection
  6.9 Reconnection time
7 Test procedures
  7.1 General
      7.1.1 Test validity
      7.1.2 Test conditions
      7.1.3 Test equipment
  7.2 Wind turbine specification
  7.3 Voltage fluctuations
      7.3.1 General
      7.3.2 Fictitious grid
      7.3.3 Continuous operation
      7.3.4 Switching operations
  7.4 Current harmonics, interharmonics and higher frequency
      components
  7.5 Response to temporary voltage drop
  7.6 Active power
      7.6.1 Maximum measured power
      7.6.2 Ramp rate limitation
      7.6.3 Set point control
  7.7 Reactive power
      7.7.1 Reactive power capability
      7.7.2 Set point control
  7.8 Grid protection
  7.9 Reconnection time
8 Assessment of power quality
  8.1 General
  8.2 Voltage fluctuations
      8.2.1 General
      8.2.2 Continuous operation
      8.2.3 Switching operations
  8.3 Current harmonics, interharmonics and higher frequency
      components
Annex A (informative) Sample report format
Annex B (informative) Voltage fluctuations and flicker
Annex C (informative) Measurement of active power, reactive
                      power and voltage
Bibliography

IEC 61400-21:2008 covers the definition and specification of the quantities to be determined for characterizing the power quality of a grid connected wind turbine; measurement procedures for quantifying the characteristics; and procedures for assessing compliance with power quality requirements, including estimation of the power quality expected from the wind turbine type. The main changes with respect to the previous edition deal with interharmonics and current distortions (