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DEE-24116 Distribution Automation Examination, May 14, 2014
Pekka Verho (Faculty calculator allowed)

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Explain typical feeder protection solution, which can be applied in radially operated
and neutral isolated medium voltage network. Which protection functions are used,
what are the principles in definition of relay settings?

Describe briefly, how the development of distribution automation has changed the
following operational processes: ;

a) Location of short circuit faults in medium voltage network

b) Handling of low voltage network faults

c) Customer service during fault situations

Explain briefly what kind of communication is typically used in the following
applications of distribution automation and why:

a) Communication inside substation

b) Communication between control center and substations

c) Customer meter reading

Calculate the reliability indices SAIFI, SAIDI and MAIFI in the following simple
feeder. Calculate the indices also in case when the disconnector is replaced with a
Breaker. What else method could be used to evaluate reliability?

Failure rate = 5 faults / 100 km, a
Temporary failure rate = 40 faults / 100 km, a
Switching time of disconnector 1 h, repair time 3 h

 

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Line length 20 km Line length 40 km

Number of customers 400 Number of customers 200