IEEE 421.2:2014 pdf free download – IEEE Guide for ldentification, Testing,and Evaluation of the Dynamic Performance of Excitation Control Systems
1.Scope
This guide includes criteria,definitions,and test objectives for evaluating the dynamic performance ofexcitation control systems as applied by electric utilities. The term excitation control system (see Figure 1)is used to distinguish the combined performance of the synchronous machine, power system, and excitationsystem from that of the excitation system alone (see IEEE Std 421.1 TM).The primary purpose of this guideis to provide a basis for evaluating the closed-loop performance of excitation control systems,includingsynchronous machines,for both large and small signal disturbances. Confirming the adequacy ofmathematical models for excitation control systems for use in analytical studies of power systems,identifying objectives for tests of excitation control systems and their components, and preparing excitationsystem specifications and additional standards will also be addressed (see IEEE Std 421.3TM’,IEEE Std421.4 TM, and IEEE Std 421.5TM,).Portions of this guide will also serve as educational material for peoplewho are becoming familiar with excitation control systems. This guide is applicable to excitation systemsused on all sizes and types of synchronous machines including those in nuclear power facilities.
Traditionally，large signal performance (see 4.2) has been more closely associated with equipmentspecification and acceptance testing，while small signal performance (see 4.3) has been more closelyassociated with stability and model studies. Matching actual disturbance data with model simulations,however，requires that both large and small signal performance criteria be considered during design,specification, and acceptance testing.
4.1 Overall
The subclauses below describe methods for tuning and testing excitation system functions as applied tosynchronous generators. The techniques and discussions apply directly to analog electronic proportionalstyle controls with feedback from various measured signals and measured with external testing andrecording instruments.Actual excitation system equipment and test equipment，however，have evolvedfrom magnetic and rotating devices，through analog electronic implementations to digital controlimplementations. Both the controls and the test equipment details must be understood and the techniquesdescribed below adapted appropriately to achieve the desired tuning goals.Additionally,modern controlsmay have multiple modes of operation where gains or feedback signals are changed to allow betterperformance depending on unit conditions such as start-up, on-line at full load, or shut-down.As a result,tests performed in one operating condition,e.g.， off-line，may not capture the control gains and timeconstants which are in service under load. A thorough review of the control gains and time constantssettings as well as logic,which may alter these parameters，must be performed prior to embarking on atesting and tuning program.
4.3 Small signal performance
Small signal performance is the response of an excitation control system, excitation system, or elements ofan excitation system to signals that are small enough that nonlinearities can be disregarded in the analysisof the response, and operation can be considered to be linear. Small signal performance of an excitationcontrol system or its components can be assessed from dynamic responses,frequency responses,or byeigenvalue analysis.(See IEEE Std 421.5,Committee Report, 1973 [B6],IEEE Tutorial Course [B23],Kundur [B29], Kundur, et al. [B30], for examples.)
Small signal performance criteria provide a means of evaluating the response of systems for incrementalload changes，incremental voltage changes,and the incremental changes in synchronous machine rotorspeed associated with the initial stages of oscillatory instability (where oscillations are small enough thatnonlinearities are insignificant). Small signal performance data provide a means for determining orverifying excitation system model parameters for system studies (see IEEE Std 421.5,Hurley and Baldwin[B4], and Dandeno, et al. [B41]). The assumption of linearity limits the application of small signal modelsas noted above.