EE-PC 425 DISTRIBUTION SYSTEM AND SUBSTATION DESIGN
MIDTERMS
ELECTRIC POWER SYSTEM- understanding of basic design principles is essential in the operation
of electric power systems
EMERGENCY POWER SYSTEM – short periods
STANDBY POWER SYSTEM – longer periods
POWER NETWORK STAGES
1.
Power must be generated.
2. Transformation (Step Up)
3. Transmitting power (Transmission Lines)
4. Transformation (Step Down)
5. Distribution of Power
ELECTRIC POWER GENERATION

Prime Movers – utility power generation, predominantly are steam turbines and internal
combustion machines, connected to an alternator


Generator Capacity – turbine units can be built for almost any desired capacity

Steam Turbines (5-1000MW)
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Gas Turbines, multiple installation (100kW-20MW)

Diesel Engine, auxiliary and standby (500-6500kW)
Generator Voltage – stepped up for longer transmission

Large generators output voltages (11 and 18 kV)

Industrial plant generators (2.4-13.8 kV)

Generator Frequency – synchronize, 60Hz

Voltage and Frequency Control


Voltage- controlled by automatic voltage generators

Frequency – directly proportional to rpm of motors, controlled by governors
Parallel Operation of Generators – large power plants normally have more than one
generator in operation at the same time


Synchroscope – enables same speed, same phase rotation and position, same voltage
DC Generation – direct current power, limited largely to special loads, obtained by
conversion or rectification of AC power near the load
AC POWER TRANSMISSION SYSTEM (Power Generation to Distribution Center)
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Bulk power transfer system between PG and DC
-
Includes sub-transmission stages to supply intermediate voltage levels
-
Sub-transmission is economical and practical because of the equipments used

Transmission Voltage


Standard nominal transmission voltages: 69kV, 115kV, 138kV, 161kV, 230kV

23-69 kV, voltage levels normally categorized as primary distribution system
Transmission Lines – distribution substation equipped with transformers which step high-low
volts

STANDARD: 3 phase, 3 conductor, overhead lines with or without ground conductor
ANDREA KAMILLE R. CARMONA
BSEE-4
AY 2022-2023 2ND SEMESTER
EE-PC 425 DISTRIBUTION SYSTEM AND SUBSTATION DESIGN
MIDTERMS
DISTRIBUTION SYSTEM (Distribution Substation to Utilization Transformer)
A. PRIMARY DS – stepped down to lower levels by distribution subtransmission
-
Consist of circuits called Primary Feeders which originates in Secondary Bus
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Nominal System Voltages: 24k to 69 kV

Distribution Substation – consist of one or more power transformer banks to get the
necessary voltage regulating equipment, buses and switchgear

Substation Arrangements – one incoming line and one transformer

Primary Section – provides connection of one or more incoming high-voltage circuits
with a switching device or a combination switching and interrupting device

Transformer Section – one or more transformers with or without automatic load –
tap changing capability


Secondary Section – connection of one or more secondary feeders
Substation Bus Arrangements – bus is a junction of two or more incoming and outgoing
circuits

Single Bus – one main bus that is energized, simplest, least reliable, one failure
results to complete loss of substation

Double Bus – two buses, two breakers, greatest flexibility, number of breakers
times two is the number of lines

Ring Bus – extension of sectionalized bus, accomplished interconnecting two open
ends
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Breaker and a Half – two main bus that is energized, shares common center, three
circuit breakers

Double Breaker, Double Bus – two main bus, each normally energized, two circuit
breakers, one circuit.


Two Fundamental Types of Systems

Radial System – has a single simultaneous path of power flow to the load

Network System – MESH, has more than one simultaneous path
Feeder Arrangements

Tie Feeder – connect two source in parallel to provide service continuity

Loop Feeder – ends connected to a source, supply two or more load points in
between, each load point can be supplied from either direction

Radial Feeder connects between a source and a load point, one directional

Parallel Feeder – connect the source and a load or load center, supply in parallel
B. SECONDARY DISTRIBUTION SYSTEM
ANDREA KAMILLE R. CARMONA
BSEE-4
AY 2022-2023 2ND SEMESTER