title: Power System Protection
author: Paul M. Anderson
description: In a world of huge, interconnected networks that can be completelyblacked out by disturbances, <i>Power System Protection</i> offersan improved understanding of the requirements necessary for promptand accurate corrective action. P.M. Anderson, a noted expert onpower systems, presents an analytical and technical approach topower system protection. His discussion shows how abnormal systembehavior can be detected before damage occurs, and points toeffective control action to limit system outages. Advance yourknowledge of power system protection through a better understandingof: <ul><li>Protective devices and controls</li><li>Protection concepts</li><li>Transmission protection</li><li>Apparatus protection</li><li>System aspects of protective systems</li><li>Reliability analysis of protective systems</li></ul><i>Power System Protection</i> is written for practicing engineersand advanced graduate-level student engineers, who need acomprehensive resource on the principles of power system behaviorand methods of system analysis. This essential reference workprovides new and advanced concepts for understanding systemsperformance.
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  Symbols and 
  designations
  Symbols and designations, 
  based on the IEC 617-series,
  IEC 617-7 (1983) and others
  Block symbols and qualifying symbols
  1. General block symbols
  Protection relay
  The asterisk must be
  replaced by one or more
  letters or qualifying
  symbols indicating the
  parameters of the device
  Protection relay with
  enabling input
  Protection relay with
  blocking input
  2. Parameters and functions
  I
  Current
  I 
   
  Reverse current
  Id
  Differential current
  Id/I
  Percentage differential current 
  (current restraint)
  Inf
  Current of nth harmonic
  I1, (Ip)
  Positive sequence current 
  component
  I2, (In)
  Negative sequence current 
  component
  I0, (Ih)
  Zero sequence current 
  component
  Irsd
  Residual current
  I 
  Earth fault current
  I 
  Current to frame
  IN
  Current in the neutral conductor
  IN-N
  Current between neutrals of two 
  polyphase systems
  Iub
  Current unbalance
  U
  Voltage
  dP/dt
  Power derivative
  Q
  Reactive power
  R
  Resistance
  X
  Reactance
  Z
  Impedance
  f
  Frequency
  n
  Rotational speed
  F
  Magnetic flux