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UNIT 7
INTRODUCTION TO DISTRIBUTION
SYSTEMS

1 Learn the meaning of the following words, word-
combinations and word groups:
Power systems, generation subsystem, transmission subsystem,
distribution subsystem, subtransmission system, distribution
system, distribution substation, primary distribution system,
secondary distribution system, distribution feeder, emanate,
supply the load, three single-phase banks, switchgear, circuit
breakers, relay, recloser, fuses.

2 Read and translate Text 1:

Text 1
Introduction to Distribution Systems

Power systems are comprised of 3 basic electrical subsystems.
 Generation subsystem
 Transmission subsystem
 Distribution subsystem

The subtransmission system is also sometimes designated to
indicate the portion of the overall system that interconnects the
extra high voltage (EHV) and high voltage (HV) transmission
system to the distribution system.
We distinguish between these various portions of the power
system by voltage levels as follows:
 Generation: 1kV-30 kV
 EHV Transmission: 500kV-765kV
 HV Transmission: 230kV-345kV
 Subtransmission system: 69kV-169kV
 Distribution system: 120V-35kV

Our focus in this unit is on the distribution system. About 40% of
power system investment is in the distribution system equipment
(40% in generation, 20% in transmission).

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