Presentation by ABS Ennin, George Coleman, David Dadson &
Anthony Ansah
Slide 2
Introduction Modern day users of electricity demand a constant
and unvarying voltage and frequency to operate new sophisticated
equipment. Customers also expect electric power 24 hours a day,
seven days a week. Many unpredictable incidents can interrupt the
continuous operation of a power system. Overhead lines may be
struck by lightning; untrimmed trees can fall or blow into a line;
strong winds can cause lines to fall or make contact with each
other; ice can accumulate resulting in overstressed conductors;
cars can hit utility poles during an accident; electrical equipment
can fail due to poor maintenance; contractors can dig into an
underground cable; operating personnel can make switching errors.
Yet, customers still expect electric power, on demand. Substations
play a significant role in meeting these requirements. 2
Slide 3
OBJECTIVES Upon completion of this module the participant
should be able to: Describe the purpose of a substation. List the
types of substations. State the advantages of various switching
configurations. List the basic components of a substation. List
methods of voltage control in a substation. Describe the function
of metering in a substation. Describe the function of relaying in a
substation Describe the function of equipment in the control room.
List and describe the function of equipment at the switchyard.
3
Slide 4
Purpose of a Substation Substations play an important role in a
power system. Basically, a substation has three main functions;
switching, transform the voltage, and control the voltage. An
electrical power system is designed so that service will continue
despite any damage or impairment to other components of the system
by natural disaster or other phenomena. When a single element of
the system is out of operation for a period of time, be it a few
seconds or several days, the power system shall be capable of
meeting the usual needs of the customer. Substations represent an
important role in providing this reliability. 4
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Purpose of a Substation One important function of substations
is switching. Whether it is switching normal load currents or fault
currents, switching protects the power system and equipment in the
event of trouble. Normally, the switching is done automatically
with relaying and circuit breakers or switches. However,
non-automatic switching of circuits can be done if it becomes
necessary to improve reliability or security of the system. 5
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Purpose of a Substation Secondly, substations function to
transform the voltage. For economic reasons, different voltages are
used in various parts of the system, ranging from 11.5kV or lower
in distribution systems, up to 330kV in bulk transmission systems.
High voltages are desirable when the amount of power is great or
the distance of transmission is very long. Lower voltages are
advantageous where the amount of power is small or transmission
distances are short. When a substation uses transformers, it
represents a division between sections of the power system with
different voltages. 6
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Purpose of a Substation Substations also function to control
the system voltage. Various types of equipment are used to
accomplish this. Voltage regulators and load-tap changers (LTCs)
modify the voltage directly; whereas synchronous condensers,
capacitor banks, static voltage compensator (svc) and shunt
reactors control system voltage by modifying the reactive power
flow. 7
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Substation Design Stage Construction Stage A substation can be
describe into two areas as: Switchyard Controlroom 8
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Switchyard A Switchyard comprises of: A Line Gantry Incoming
Line Outgoing Line Bus Configuration Transformer Bank Feeder
Structure Earthing Voltage Control 9
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Switchyard Equipment Lines Incoming Line Gantry Outgoing Line
Gantry Shield Wire Network Line Insulators/Arcing Horns Wave Traps
Line CVTs Line Lightning Arrestors/Shaded Rings Skywire or
Shieldwire Line Disconnecting Switches By-pass Switches Line
Breakers Dead and Live Tanks Line Ground Switch 10
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Switchyard Equipment - Line Gantry 11
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Switchyard Equipment - Line Gantry 12
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Switchyard Equipment - Line Insulator/Wave Trap/Arcing Horns
13
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Switchyard Equipment Arcing Horns 14
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Switchyard Equipment Free Standing CTs for SF6 Breaker Live
Tank 15
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Switchyard Equipment 16 Lightning Arrestor with Shaded
Ring
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Switchyard Equipment - Surge arresters act to discharge any
power surge (transient currents) high enough to cause serious
damage. During normal operating conditions, surge arresters appear
in the system as open circuits. When a disturbance occurs, such as
from a lightning strike or switching surge, surge arresters
discharge transient voltages that can cause serious equipment
damage to ground. 17 Lightning Arrestor with Shaded Ring
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Switchyard Equipment Free Standing CTs for SF6 Breaker Live
Tank 18
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Switchyard Equipment 19 Live Tank SF6 Circuit Breaker
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Switchyard Equipment Live Tank SF6 Breaker 20
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Switchyard Equipment Dead Tank SF6 Breaker 21
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Switchyard Equipment 22 Dead Tank
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Switchyard Equipment 23 SF6 Circuit Breaker
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Switchyard Equipment 24 SF6 Circuit Breaker
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Switchyard Equipment 25 Disconnect Switch
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Switchyard Equipment 26 Lightning Arrestor with Shaded
Ring
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Switchyard Equipment 27 CVT with WAVETRAP
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Switchyard Equipment 28 CVT with Carrier Mounting Device
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Switchyard Equipment Busbar Conductors Hollow Bus Busbar
Insulator Support Bus PTs Bus CVT/CTs Bus Ground Switch 29
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Substation Bus Configuration Single Bus 30
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Substation Bus Configuration Transfer Bus 31
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Substation Bus Configuration Double Bus 32
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Substation Bus Configuration Reserve Bus 33
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Substation Bus Configuration Ring Bus 34
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Substation Bus Configuration Breaker and Halve (Mesh) Bus
35
Switchyard Equipment Feeder Structure Feeder Breakers Feeder
CTs Feeder PTs Station Service Transformer Fused Switches Grounding
Transformer Customer Connections Capacitor Banks Capacitor Bank
Breaker Capacitor Bank Ground Switches Capacitor Bank Disconnect
Switches 38
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Switchyard Equipment 39 Current Transformer
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Switchyard Equipment 40 Voltage Transformer
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Switchyard Substation Earthing System Earthing Alternatives
There are three basic alternatives, isolated systems with no
intentional connection to earth, impedance earthed systems with
connection through a reactor or resistor and directly earthed
systems where transformer neutrals are connected directly to earth.
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Slide 42
Substation Earthing Earthing of fences Fences around the
substation are might be energised through induced currents from
overhead lines passing above. They should always be connected to
encircling earth wires. The best is to put the earth wires outside
the fence, but risks for theft often makes more practical to put
them inside the fence. The most common practice is to connect the
fence at corners and every 50m along straight stretches. Gateposts
shall always be connected. Fences inside the substation area must
also be connected to the earth grid in the same way. However, for
straight stretches, connect at every 10m. NOTE: if the fence
surrounds an air-core reactor group, the fence must be connected to
earth at one place only, and that should be by one gatepost (if
there is a gate). If the fence is connected at more than one place,
the magnetic field surrounding the reactors will drive very 42
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43
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Switchyard Voltage Control Capacitor Banks Transformers SVC
Static Voltage Compensators Reactors Synchronous Condenser 44
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45 Controlroom Equipment Annunciator Panel Relay Panel
Protective Relays Control Panel Indicating Lamps AC 400v Station
Service Panel DC 125V Rectifier DC 48V Rectifier 125v Battery Banks
48v Battery Bank DC/DC Converters
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Controlroom Equipment Annunciator Panel 46
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Controlroom Equipment Annunciator Panel 47
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Controlroom Equipment Relay Panels 48
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Controlroom Equipment Relay Panel 49
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AC Station Service Panel 50
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Controlroom Equipment 51 DC 125V Rectifier
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Controlroom Equipment 52 DC 125V Panel
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Controlroom Equipment 53 DC 125V Rectifier
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Controlroom Equipment 54 DC 48V Rectifier
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Controlroom Equipment 55 125v DC battery Bank 48v DC battery
Bank