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Electrical
Substation

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 What is electric substation??
 Why need electric substation?
Introduction

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 Substation is a very important part in electrical power
system.
 Substation is the part of a power system in which the
voltage is transformed from high to low or low to high for
transmission, distribution, transformation and switching..etc.
 Substation which connected with other substations through
power transmission lines called Grid substation.
Introduction

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 Substation has different voltage levels, elements, and
facilities.
 500kV / 230kV substation
 230kV / 115 kV substation
 115kV / 22kV substation
 22kV / 0.4kV substation
Introduction

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Introduction

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 Mostly substation is divided into two main sections.
1. Control panel section
 A room which contains control panels and protection
system.
2. Switch yard section
 It is outside section of control room.
Section division

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1. Control panel section
 It is indoor section which contains two main parts.
1) Control panel parts which related to controlling of instruments,
feeder power flow, power flow in substation., etc
2) Relay protection panels is the protection system in whole
substation : relay panel, bus bar, line, transformer protection
panel…etc.
Section division

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2. Switch yard section
 It is the field of outdoor part which contains operation and
control elements such as:
 Power transformer
 Bus bar
 CT, CVT, CB, DS, Insulator,
 Incoming and outgoing line…etc
Section division

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Diagram

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Main elements

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 Here are the main criteria for consideration for the construction.
 It should locate at proper site
 It should provide safe and reliable arrangement
 Good design and construction
 It should be easily operated & maintained
 It should involve minimum capital cost
Construction requirement

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 In term of insulation, substation is classified into two types.
1. Air insulated substation (AIS)
2. Gas insulated substation (GIS)
 In case substation used the combination of AIS and GIS
technologies called “Hybrid Substation”.
Classification

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 Air Insulated Substation (AIS)
 Widely used in the world nowadays
 Use air as the insulation between conductor to conductor and conductor
to ground
 Air insolation is simple and cheap
 Mostly used in areas where space, weather conditions, and
environmental concerns are not an issue such as rural areas, and
favorable offsite terrain.
Classification

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 Air Insulated Substation (AIS)
 Mostly it is outdoor substation
 Indoor AIS version is only used in highly polluted areas, and saline
conditions, as the air quality is compromised
Classification

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 Air Insulated Substation (AIS)
 Advantage
 The primary choice for areas with extensive space
 With quality design, the system is viable due to the low construction
costs and cost of switchgear
 Less construction time, thereby more suited for expedited installations
 Easy maintenance as all the equipment is within view. It is easy to
notice and attend to faults
Classification

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 Air Insulated Substation (AIS)
 Disadvantage
 More space is required
 Vulnerable to faults since the equipment are exposed to the external
elements such as human intrusion, pollution, deposition of saline
particles, lightning strikes and extreme weather conditions
 More maintenance requirements, thus leading to high costs
 The poor dielectric properties of air, as well as secondary factors such
as humidity, pollutants, moisture.
Classification

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 Gas Insulated Substation (GIS)
 Use gas as the insolation
 Contain the same compartments and components as the normal (AIS)
setups
 All components are enclosed in a grounded metal enclosure, then the
whole system housed in a chamber full of gas.
 Gas insulated substations (GIS) primarily use sulphur hexafluoride gas
as the primary insulator.
Classification

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 Gas Insulated Substation (GIS)
 SF6 is non-toxic, maintains atomic and molecular properties even at
high voltages, high cooling properties, and superior arc quenching
properties.
Classification

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 Gas Insulated Substation (GIS)
 SF6 has superior dielectric properties compared to other gases; thereby
provide favorable insulation for the phase to phase and phase to ground
moderation
 It is more complex and expensive than air insulation. In terms of safety
and effectiveness
 Very applicable for indoor and underground substation.
Classification

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 Gas Insulated Substation (GIS)
Classification

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 Gas Insulated Substation (GIS)
 Advantage
 The earthed metal enclosure makes for a safe working environment for
the attending personnel.
 Low maintenance requirements due to expedient design and protection
against external elements.
 Quick assembly due to extensive pre-assembly
Classification

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 Gas Insulated Substation (GIS)
 Advantage
 SF6 neither ages nor depletes. There is no need to top up the gas
levels throughout the equipment lifetime (approx 40 years).
Classification

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 SF6 insulation properties
Classification

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 SF6 insulation properties
Classification

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 Gas Insulated Substation (GIS)
 Disadvantage
 High installation costs compared to AIS systems.
 Procurement and supply of SF6 gas can be a problems especially in
rough terrain and off site locations. This further increases the costs.
 High level of maintenance is required. This requires highly skilled
personnel
Classification

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 Gas Insulated Substation (GIS)
 Disadvantage
 If has internal fault, difficult to find and repair.
 If has leakage, it is so harmful to environment due to its huge
contribution in global warming compared to CO2.
 Its potential is 22 200 time greater than CO2.
 It is a very expensive product.
Classification

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 Hybrid Substation
 Reduced cost of GIS due to air insulted bus bar. Air insulated bus bar is
relatively inexpensive.
 Reduce spaced required of AIS.
 Most reliable and cost-effective solution for new installations,
expansions or replacement of existing substations.
Classification

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 Hybrid Substation
Classification

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Classification
-Transformer substation
- Switching substation
- Power factor correction
substation
- Frequency changer substation
- converting substation
- Industrial substation
- Indoor substation
- Outdoor substation
- Underground substation
- Pole-mounted substation
Substation classification
Requirement based Constructional based

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 Transformer substation
 Changing the voltage level of electric supply
 Receive power of some voltage and deliver it to other voltage level.
 Most of the substation
are like ‘transformer substation’.
Requirement based

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 Switching substation
 Do not change the voltage level
 Incoming voltage = outgoing voltage
Requirement based

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 Power factor substation
 This substation locate at receiving end of transmission line
 Commonly ‘synchronous condenser’ is used for power factor
 Substation improve the system power factor
Requirement based

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 Converting substation
 Converting substation converting to AC power to DC power.
 Use for traction system (railways), welding, electroplating..
Requirement based

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 Frequency changer substation
 Those substation can change the supply frequency
 Frequency change may require for industrial utilities
 An electronic or electromechanical
device that converts alternating current (AC)
of one frequency to alternating current
of another frequency.
Requirement based

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 Industrial substation
 Supply power to the individual industrial consumers or commercial
buildings.
Requirement based

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 Indoor substation
 Inside building or where the space constraints.
 Mostly is GIS
 Applicable in high building/ urban areas to reduce the noise from the
transformers, for reasons of appearance, or to protect switchgear from
extreme climate or pollution conditions.
Constructional based

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 Indoor substation
 Voltage up to 11kV and can be increased up to 66kV
Constructional based

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 Outdoor substation
 Very widely used in power system nowadays
 For all voltage levels between 55 KV to 765 KV.
 Transformers and other heavy and large equipment are installed in
outer space and only control equipment are installed in the building
 Less expensive
 easy to construct and maintenance
Constructional based

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Comparison
Outdoor Indoor
More space required Less space required
Less time required for maintenance More time required for maintenance
Easy future extension Difficult future extension
Easier fault location because of
equipment being in full view.
Difficult fault location because of
equipment not being in full view.
Low capital cost High capital cost
Difficult operation Easier operation
Faults detection time is less. Fault detection time is more.

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 Underground substation
 Mostly in most populated areas
 an effective solution for saving space in city areas
 less impact on the environment.
Constructional based

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 Pole-mounted substation
 Outdoor type substation
 For supporting small rating distribution transformer up to 250KVA
 Mounted on the supporting structures of high tension distribution line
 Basically there are two pole mounting structures used in Power system
1. Single pole mounting
2. H-pole mounting
Constructional based

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 Single pole substation
 Transformer is mounted on single
pole with the help of angles and
other metallic structures collectively
called transformer platform.
Constructional based

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 Single pole substation
Constructional based

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 H pole substation
 Used for relatively high rating
transformers
 Two poles are installed so that to
provide a base for the transformer
 This arrangement is used because
the weight of the transformer is
heavy.
Constructional based

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 Battery bank
 In Substations we use battery bank to provide an uninterrupted &
reliable power supply to control the switch gears & Monitor the status of
Feeders in case of power failure.
Other facilities

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 Capacitor bank
 Normally capacitor bank is used in distribution Substation to control the
level of the voltage supplied to the consumer by reducing or eliminating
the voltage drop in the system.
Other facilities

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 HVAC System
 Substations require special attention to ventilation in order to dissipate
heat losses from electrical equipment.
 Forced ventilation should be used where natural ventilation is not
practicable ,means fan system must be installed.
Other facilities

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 Fire Fighting System
 Substations contain components and materials that against a fire risk.
 For preventing fire, fire systems are installed in substations on the
sensitive area which give signal or alarm in case of fire such as fire
alarm, water sprinkler, smoke detector heat detector.
 Not all possible fire protection measures are necessary for every
substation
Other facilities

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 Fire Fighting System
Other facilities

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 Gate
 The substation building are surrounded by the fence or concrete wall to
prevent the unauthorized person or animals to get in.
Other facilities