NEPTUNE Power System Protection

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NEPTUNE Power System Protection

• Kevin Schneider, Chen-Ching Liu
• Department of Electrical Engineering, University
  of Washington
• Harold Kirkham
• Jet Propulsion Laboratories

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Protection Areas

• 1) Medium voltage backbone protection
• 2) Internal node protection
• 3) Low voltage protection

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Backbone Protection Layers

• 1st- Differential measurements and pilot tones,
  combined.
• 2nd- Primary zone distance relays.
• 3rd- Secondary zone distance relays

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Backbone 1st Protection Layer

• Uses two protection techniques
• 1) Differential current protection
• 2) Pilot tone relaying

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Normal Operating Conditions

• Differential current measurements.
• Double pilot tone.
• DO NOT TRIP
• Primary relay in place.
• Back up relay in place.

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Loss of Both Signals

• Differential comms. are lost.
• Pilot tones are lost.
• PRIMARY TRIPS BREAKER
• Back up relay in place.

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Loss of Differential Comms.

• Differential comms. Are lost.
• Pilot tones are not lost.
• DO NOT TRIP
• Primary relay in place.
• Back up relay in place.

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Loss of Pilot Tones

• Pilot tones are lost.
• TRIP IF DIFFERENTIAL PROTECTION DETECTS FAULT
• Back up relay in place.

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Backbone 2nd Protection Layer
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Backbone 3rd Protection Layer
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Backbone Relay Coordination
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Node Protection Layers

• 1st- Node differential protection step 1
• 2nd- Converter differential protection
• 3rd- Node differential protection step 2

Note the 1st and 3rd layers work on the same
principle but their resulting protective actions
are different.
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Node 1st Protection Layer
Current 1 Current 2 Current 3 0 If a fault
is detected then the running converter is secured
and the second unit is started
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Node 2nd Layer Protection

• Same techniques as transformer differential
  protection
• Must account for losses in the main power
  converter
• If a fault is detected the converter is secured
  and the other unit started

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Node 3rd Layer Protection
Current 1 Current 2 Current 3 0 Similar to
the first layer except that in the event of a
fault the entire node is secured through the
opening of adjacent node backbone breakers
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Node Relay Coordination
Note all three layers will actuate before the
3rd layer of the backbone protection. This will
prevent unnecessary loss of loads.
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Node Low Voltage Protection

• Low voltage protection is similar to distribution
  system protection
• Can use any of the following methods
• 1) Over current
• 2) Distance relaying
• 3) Ground fault indication
• 4) A combination of methods

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Questions?