Computer Modeling of Rotating Machines

Computer Modeling of Rotating Machines

J.J. Dai (Operation Technology, Inc., USA)
DOI: 10.4018/978-1-4666-1921-0.ch009
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Abstract

Modeling and simulating rotating machines in power systems under various disturbances are important not only because some disturbances can cause severe damage to the machines, but also because responses of the machines can affect system stability, safety, and other fundamental requirements for systems to remain in normal operation. Basically, there are two types of disturbances to rotating machines from disturbance frequency point of view. One type of disturbances is in relatively low frequency, such as system short-circuit faults, and generation and load impacts; and the other type of disturbances is in high frequency, typically including voltage and current surges generated from fast speed interruption device trips, and lightning strikes induced travelling waves. Due to frequency ranges, special models are required for different types of disturbances in order to accurately study machines behavior during the transients. This chapter describes two popular computer models for rotating machine transient studies in lower frequency range and high frequency range respectively. Detailed model equations as well as solution techniques are discussed for each of the model.
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Introduction

Rotating machines are essential components in power systems. Their dynamic and frequency responses to system disturbances are important to determine system stability and safety. To correctly simulate rotating machine responses in power system transient studies, two things need to be considered: (1) understanding origin and especially frequency ranges for various power system disturbances, and (2) determining rotating machine computer models and applying them properly to different types of simulation studies.

Power system disturbances can have different origins and cover a wide range for frequency. Table 1 lists some typical transient phenomena in power systems and the associated frequency range classifications (Martinez, Mahseredjian & Walling, 2005).

Table 1.
Power system disturbances and their frequency ranges
      Disturbance Origin      Frequency Range (Hz)
      Ferroresonance      10-1 – 103
      Load rejection10-1 – 3103
      Fault clearing50/60 – 3103
      Line switching50/60 – 2104
      Transient recovery voltage      50/60 – 105
      Lightning overvoltages104 – 3106
      Disconnector switching in GIS105 – 5107

These classifications are proposed by International Electrotechnical Commission (IEC, 1985) and CIGRE (CIGRE, 1990). IEC and CIGRE further classify these disturbances into four categories, according to their frequency ranges:

  • Low-frequency oscillations – disturbance signal frequency from 10-1 to 103 Hz

    • Slow-front surges – disturbance signal frequency from 50/60 to 2104 Hz

    • Fast-front surges – disturbance signal frequency from 104 to 3106 Hz

    • Very-fast-front surges – disturbance signal frequency from 105 to 5107 Hz

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