IEEE Std 421.2 pdf free download

IEEE Std 421.2 pdf free download.Identification, Testing, and Evaluation of the Dynamic Performance of Excitation Control Systems.
4.3 Small signal performance Small signal performance is the response of an excitation control system, excitation system, or elements of an excitation system to signals that are small enough that nonlinearities can be disregarded in the analysis of the response, and operation can be considered to be linear. Small signal performance of an excitation control system or its components can be assessed from dynamic responses, frequency responses, or by eigenvalue 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 incremental load changes, incremental voltage changes, and the incremental changes in synchronous machine rotor speed associated with the initial stages of oscillatory instability (where oscillations are small enough that nonlinearities are insignificant). Small signal performance data provide a means for determining 0 verifying 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 models as noted above.
4.4 Effects of excitation limiters A modern excitation system used on a synchronous machine may have sufficient excess capability to supply excitation under all operating conditions. The voltage regulator utilizes various auxiliary control and limiting functions that are designed to enhance power system performance and reliability while protecting both the excitation system and the synchronous machine. These limiting functions generally have no effect on the excitation output during normal operating conditions, but protect the exciter and machine during severe unit or power system disturbances in which the excitation system is pushed near or beyond defined operating limits (see Carleton, Bobo, and Burt [B40], Eberly and Schaefer [B42], Overexcitation Limiting Devices [B43]， Underexcitation Limiter Models [B44], Nagy [B46]， Ribeiro [B47]， Rubenstein and Temoshok [B48]). Typical excitation limiters include overvoltage, volts/hertz, overexcitation (both instantaneous and timed), underexcitation, and stator current limiters. These limiters may act to either decrease or increase the excitation level of the synchronous machine, depending on the type of limiter and the power system circumstances. Where a power system stabilizer (PSS) is applied, limiters should coordinate with PSS functions, and preferably not block the stabilizing signal. (This is more critical for underexcitation limiters as instabilities develop more readily at reduced levels of machine field current.)
5.1 General The following large signal performance criteria relate to excitation control systems and, where applicable, their components. To permit maximum flexibility in the design, manufacture, and application of excitation systems, some of the performance criteria are defined under “specified conditions.” The applicable conditions may be specified by the manufacturer or, more usually, by the equipment purchaser to meet applicable reliability or interconnection requirements. Care must be exercised that the“under specified conditions” clauses are interpreted in a manner consistent with the application. It should be noted that some of the criteria discussed below cannot be directly tested and, thus, might depend on a combination of testing and simulation techniques to be verified. When specified in per unit (pu), the base value (1 pu) of synchronous machine field current is normally considered to be the current required to produce rated terminal voltage on the air-gap line (see the annex in IEEE Std 421.5 on per unit system). The corresponding value of synchronous machine base field voltage is the air-gap field voltage as defined in Clause 3 and IEEE Std 421.1.IEEE Std 421.2 pdf download.