Verification of limiter performance in modern excitation control systems

Abstract

Modern excitation systems include devices for controlling or Limiting machine terminal voltage (overvoltage biters), Volts P r hertz ratio w/Hz biters), U K O & U~~ machine field current (overexcitation limiters), and the reactive load absorbed by the machine (underexcitation Limiters). Functional testing of these limiters before they are placed into testing of excitation limiters commercial service is recommended. The Bureau of to determine synchronous machine reactive capability Reclamation routinely performs functional testing to determine limiters as pad of excitation system tests on its the coordination of these limiters with the corresponding hydroelectric generators. This paper & C U S S &e purpose protective devices. Also, funCtiOIld testing Of the limiters and practice of functionally testing these Limiters. will confirm proper operation and stability. and function properly, these relays should not trip the machine. The limiter and relay adjustments provided in this paper are typical for hydroelectric generators installed in B~~~~~ of ~~l~t i~~ facilities. A number of utilities the actual settings and operational characteristic of these [1,2,3,4,51. In addtion, tests are performed to determine

Operating limits of underexcited synchronous generator

“…Classical synchronous generator's power chart usually has limits in an underexcited quadrant defined by stability limits and minimal field current. However, it has been noticed that some generators during continuous underexcited operation, even within the allowed operation area, have increased temperatures of conductive parts in the end region of the generator [1,2].…”

Determination of Load Angle for Salient-pole Synchronous Machine

“…The load angle value is important information especially in the case when generator operates in under-excitation state, because the load angle then assumes the maximum allowed value in relation to the stability limit of synchronous generator operation. The load angle can be used as a measure of how close the generator is to pole slipping and can be also used to limit the excitation current during its operation in capacitive mode [3]- [6]. The application can be also possible in the implementation of the power system stabilizer, where change of the load angle can be used as a stabilizer input signal [7].…”

Dynamic Performance of an Excitation System Built in a Digital Way

“…The limiters take the operating point to a state inside of the limits of the machine's capability. [2], [4].…”

“…The underexcitation limiter avoids the machine loss of synchronism or avoids an overheating in the stator end region, due to his close operation to the minimal limit of the machine's capability curve [2], [4]. The underexcitation limiters can perform in two ways: Taking control of the system through a diode in a High Value (HV) gate.…”

“…The way to reach this desired point has different configurations: some limiters operate with a inverse time characteristic, other generate a ramp as a function of the overexcitation quantity [2], [4], [5].…”