Detecting Power Grid Synchronization Failure on Sensing Frequency or Voltage Beyond Acceptable

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Detecting Power Grid Synchronization Failure on
Sensing Frequency or Voltage Beyond Acceptable
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Detecting Power Grid Synchronization Failure
Introduction

• Synchronization means the minimization of
  difference in voltage, frequency and phase angle
  between the corresponding phases of the generator
  output and grid supply. An alternating current
  generator must be synchronized with the grid
  prior to connection. It cant deliver the power
  unless it is running at same frequency as the
  network.
• Synchronization must occur before connecting the
  generator to a grid. Synchronization can be
  achieved manually or automatically. The purpose
  of synchronization is to monitor, access, enable,
  and automatically take the control action to
  prevent the abnormalities of voltage and
  frequency.

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Rules Must Be Followed for Power Grid
Synchronization
Voltage Fluctuation

• When a generator is synchronized with a power
  grid.
• There is a voltage fluctuation on the
  distribution line.
• During synchronization the voltage fluctuation
  should not exceed 3 at the at the point of
  common coupling.

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Rules Must Be Followed for Power Grid
Synchronization
Synchronization Limits

• The limits allowing for synchronization are.
• Phase angle- /-20 degrees
• Maximum voltage difference 7
• Maximum slip frequency 0.44

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Rules Must Be Followed for Power Grid
Synchronization
Relays

• For checking the synchronization synch check
  relay must be used.
• The usage of relays cant apply for induction
  generators.
• The use of synch check relay is to accept as a
  backup during synchronization.
• It ensures a generator will not connect to a dead
  distribution line.

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Synchronization of Induction Generators

• Standard motor controllers will be used to
  synchronization of induction generators.
• Turbine shaft power will be used to mechanically
  drive the generators up to synchronization speed.
• The speed of the motors depends on supplied
  frequency and number of poles on the generators.

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Synchronization of Synchronous Machines

• For synchronous generators output waveform should
  be in phase with the grid voltage waveform.
• The rate of change of phase angle between the
  grid and the machine (generator) must be within
  the specified limits.
• Some other rules are variable speed drive
  arrangement to maintain a constant output
  frequency.

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Failure of Synchronization

• There are various reasons for failure of power
  grid synchronization.
• Synchronization circuit may fail for responding
  to a received input pulse.
• It happens when the received input pulse is
  shorted than the sampling period of the
  synchronizer.
• Then no synchronized representation will take
  place.
• Synchronization circuit may fail, when the pulse
  rate of the input signal is higher than the
  synchronization rate of the synchronizer.

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Synchronization Failures and their Detections

• Generators and some local loads have become
  disconnected from main distribution lines due to
  some issues.
• Due to this there is a reduction in quality of
  supply.
• It may prevent automatic reconnection of devices.
  This is called as islanding.
• Islanding must be detected and producing power
  must be stopped immediately.

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Following Hazards May Take Place Due to Islanding

• Line voltages may excessive when distributing
  lines and generators are disconnected the line is
  not earthed.
• Due to Islanding synchronization cant be
  maintained.
• The fault level contribution from the grid to
  sub-station may be lost.
• Due to this sufficient current may not be
  generated.
• The voltage levels may go outside of normal
  operating limits, and the quality of supply may
  be reduced.

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Detection Methods of Islanding

• Detection of islanding can be done through active
  and passive methods.
• Passive methods look for transient events on the
  grid.
• Active methods will probe the grid by sending
  signals from the distribution point of grid.
• Loss of Mains Protection (LoM) will be designed
  to sense the disconnection of generators.
• The blind area is called Non Detection Zone
  (NDZ).

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Which Microcontrollers Are Used in This Project?

• 40 pin 8051 Microcontrollers are used in this
  project.
• The Microcontroller monitors the under/over
  voltage being derived from a set of comparators.

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Applications of Power Grid Failure Detection

• Lighting is one of the main causes for power
  system faults.
• The major advantage is detecting the
  synchronization failure between generators and
  power grid.
• When there is an Under/over voltage or under/over
  frequency.
• The comparator will detect the difference the
  actual power and reactive.
• If there is no failure of power grid
  synchronization then the detectors will give the
  zero values.

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Block Diagram
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Hardware Requirements

• 8051 series Microcontroller
• LCD
• Op-Amps
• 555 timer
• Crystal
• Resistors
• Capacitors

• Diodes
• Transformer
• Voltage Regulator
• Relay
• Transistors
• Slide Switch
• Lamp

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