230 KV SUBSTATION
House Rules
Observe silence Raise hand to question Avoid side discussions Turn off your cellular phones or keep it in silent mode230 kV Substation Seminar
Seminar Objectives
This seminar takes an in-depth look into thecomponents used in the transmission of electricity
Learn typical configurations of switchyardsand substation
Learn the operation of transformers, circuit breakers,disconnects, current and potential transformers and
lightning arresters
Learn the components which make up a typicalsubstation and how it feeds a distribution network
that supplies customers with electricity
230 kV Substation Seminar
Seminar Outline
I. Introduction
I.1 Power Substation
I.2 Transmission Lines
II. HV Outdoor Switchyard
II.1 Types of Substation Configuration
II.2 Outdoor HV Circuit Breakers
II.3 HV Disconnect Switches
II.4 HV Current Transformers
II.5 HV Capacitor Voltage Transformer (CVT)
II.6 Surge Arresters
II.7 Power Systems Communications
II.8 Typical HV Outdoor Substation Layout
230 kV Substation Seminar
Seminar Outline
III. Gas Insulated Substation
III.1 Sulfur Hexaflouride (SF6) Gas
III.2 Types of HV Substation
IV. Power Transformer
III.1 Classifications of transformer
III.2 Cooling Methods
230 kV Substation Seminar
Introduction
1. Uses of Power Substation:
Line termination Switching Protection Metering and voltage transformation Control and stabilization between thegenerating plant to the customers terminal
230 kV Substation Seminar
Introduction
2. Transmission Lines
The transmission lines serves as the linkage
between power generation and the power
substations which serve as a voltage
transformation point or switching or both.
The delivery capability of the substation is
dependent on the capacity of the transmission
lines.
230 kV Substation Seminar
HV Outdoor Switchyard
1. Types of Substation Configuration
The arrangement of outdoor switchyard installation is
influenced by economic considerations, in particular the
adaptation to space availability and the operational
requirements of reliability and ease of operations.
a) Single bus system
b) Single bus system with by-pass bus
c) Duplicate bus system
d) Duplicate bus system with by-pass bus
230 kV Substation Seminar
HV Outdoor Switchyard
1. Types of Substation Configuration
e) Multiple bus system
f) Multiple bus system with by-pass bus
g) H-shape system
h) Three breaker system
i) Ring-bus system
j) Polygon system
k) One-and-a-half breaker system
l) Two breaker system
230 kV Substation Seminar
230 kV Substation Seminar
HV Outdoor Switchyard
230 kV Substation Seminar
HV Outdoor Switchyard
230 kV Substation Seminar
HV Outdoor Switchyard
2. Outdoor HV Circuit Breakers
2.1 Dead-tank circuit breakers
A North American design using bulk oil
(old design) or SF6 (new design) as the
Interrupting medium.
SF6 power circuit breaker utilize the puffer
Principle of arc interruption. This principle
utilizes compressing SF6 during the opening
Stroke and exhausting compressed SF6
through the breaker contacts to extinguish the
Arc.
230 kV Substation Seminar
HV Outdoor Switchyard
230 kV Substation Seminar
HV Outdoor Switchyard
2. Outdoor HV Circuit Breakers
2.2 Live-tank circuit breakers
A European design using SF6 as the
Interrupting medium. Its difference with the
Dead-tank design is the absence of a CT as an
Integral part of the breaker.
230 kV Substation Seminar
HV Outdoor Switchyard
230 kV Substation Seminar
HV Outdoor Switchyard
3. HV Disconnect Switches
Disconnect switches or disconnectors are
mechanical swinging devices which in the open
position provide an isolating distance.
They are used primarily for isolation and
sectionalizing electric circuits such as buses,
lateral circuits or portions of main circuits, and
for special purposes such as testing and
Maintenance.
230 kV Substation Seminar
HV Outdoor Switchyard
3. HV Disconnect Switches
Types of disconnect switches:
a) Vertical-break
b) Side-break
c) Center-break
230 kV Substation Seminar
230 kV Substation Seminar
HV Outdoor Switchyard
230 kV Substation Seminar
HV Outdoor Switchyard
230 kV Substation Seminar
HV Outdoor Switchyard
4. HV Current Transformer
A separate units of HV current transformers are
Required in live-tank circuit breakers installations.
They provide the necessary interface between the
HV and LV systems where protection, metering,
and control signals are obtained.
230 kV Substation Seminar
HV Outdoor Switchyard
230 kV Substation Seminar
HV Outdoor Switchyard
5. HV Capacitor Voltage Transformers (CVT)
Capacitor voltage transformers or CVT are
installed in high voltage systems with
transmission voltages from 66 kV up to the
highest voltages in the EHV range.
Functions:
a) Metering
b) Protection
c) Sychronizing
d) Indication
230 kV Substation Seminar
HV Outdoor Switchyard
5. HV Capacitor Voltage Transformers (CVT)
They are often used simultaneously for coupling
carrier frequencies to power lines for purposes
of telecommunication, remote metering, selective
line protection and control.
230 kV Substation Seminar
HV Outdoor Switchyard
5. HV Capacitor Voltage Transformers (CVT)
The CVT has a distinct economic advantages
at higher voltages over the conventional
electromagnetic voltage transformers. At
voltages of 100 kV and above, the selection
of a CVT over the conventional VT is
economically motivated by its duality of
function: as a standard voltage transformer
and as a coupler for high frequency
power line carrier system.
230 kV Substation Seminar
HV Outdoor Switchyard
230 kV Substation Seminar
HV Outdoor Switchyard
6. Surge Arresters
Surge arresters in outdoor substations are used
for limiting over voltages. The protection zone of
the arrester is limited due to the traveling phenomena.
To ensure that the voltage across the protected
equipment is more or less equal to the surge
arresters protective level, it is necessary to maintain
a certain separation distance between the arrester
and the protected equipment.
230 kV Substation Seminar
HV Outdoor Switchyard
6. Surge Arresters
For rated voltages of 123 kV, the arrester should
not be farther than 15-meter from the
protected apparatus
For 245 kV up to 525 kV, the maximum distance
is 20-meter.
230 kV Substation Seminar
HV Outdoor Switchyard
230 kV Substation Seminar
HV Outdoor Switchyard
230 kV Substation Seminar
HV Outdoor Switchyard
230 kV Substation Seminar
HV Outdoor Switchyard
7. Power System Communications:
Power line carrier (PLC) systemUse of fibre optic communicationPLC System
Carrier links using the HV transmission lines
or PLC systems are used by many power
utilities as the form of its communications.
They cater to the different communication
tasks required by the power utility which
includes the following: signals for telephony,
line protection, telemetering, remote control, etc.
230 kV Substation Seminar
HV Outdoor Switchyard
7. Power System Communications:
Fibre Optic Communication
The use of fibre optic communication has
continuously gained ground in recent years.
The reasons are mainly due to the growing needs
for increased transmission capacity as well as
the enormous advantages of optical fibres over
copper cables.
230 kV Substation Seminar
HV Outdoor Switchyard
230 kV Substation Seminar
HV Outdoor Switchyard
230 kV Substation Seminar
HV Outdoor Switchyard
230 kV Substation Seminar
HV Outdoor Switchyard
8. Typical HV Outdoor Substation Layout
230 kV Substation Seminar
HV Outdoor Switchyard
8. Typical HV Outdoor Substation Layout
230 kV Substation Seminar
Gas Insulated Substation
Gas-insulated substation or GIS is usually of
modular construction. All components such as
busbars, disconnectors, circuit breakers,
instrument transformers and cable terminations
are housed in a grounded metallic enclosures
in which the primary insulating medium is
a compressed gas, usually SF6.
230 kV Substation Seminar
Gas Insulated Substation
Advantages:
1) Compact size
2) Low weight
3) High reliability
4) Safety against touch contact
5) Low maintenance
On-site erection time is short due to the extensive
prefabrication and factory testing of large assemblies
or complete bays.
230 kV Substation Seminar
Gas Insulated Substation
1. Sulfur Hexaflouride (SF6) Gas
Sulfur hexaflouride gas or SF6 is employed as
insulation in all parts of the GIS installation and
likewise used as the interrupting medium of the
circuit breakers.
SF6 is a highly electronegative gas (it readily
absorbs electrons to form negative ions) and has
A dielectric strength of about 89 kV/cm-bar in a
uniform field or about 3 times that of air.
230 kV Substation Seminar
Gas Insulated Substation
2. Types of HV Substation
There are several principal types of designs
for HV substations. They can be conventional
outdoor or indoor, gas insulated substation or
GIS, or can be a hybrid as summarized on
Table III.2.1.
230 kV Substation Seminar
Gas Insulated Substation
Table III.2.1
Principal Types of Designs
For HV Substation Installations
(*) special cases only
(**) station conversion, expansion or upgrading
Basic DesignInsulating MediumVoltage Level, kVApplicationConventionalAir52-123Outdoor/ ndoorConventionalAir123-800outdoorGISSF652-800Indoor/outdoor*Hybrid**Air/SF6245-500outdoor230 kV Substation Seminar
Power Transformers
One of the most important apparatus in the electrical
system is the transformer. This is used to transfer
power by electromagnetic induction between two or
more circuits at the same frequency. The power
transfer is usually accompanied with a change of
voltage and current.
230 kV Substation Seminar
Power Transformers
1. Classification according to size
1.1 Distribution transformer
Distribution transformers are used for
transferring power from the primary
distribution circuit to a secondary distribution
circuit.
rated 5 kVA up to 500 kVA inclusive
230 kV Substation Seminar
Power Transformers
1. Classification according to size
1.2 Power transformer
Power transformers are used for
transferring power in any part of the system
between the generator down to the primary
distribution system.
rated 500 kVA above
230 kV Substation Seminar
Power Transformers
100 MVA Power Transformer
230 kV Substation Seminar
Power Transformers
100 MVA Power Transformer
230 kV Substation Seminar
Power Transformers
100 MVA Power Transformer
230 kV Substation Seminar
Power Transformers
2. Classification according to insulation
2.1 Liquid-immersed transformers
Liquid-immersed transformers are those whose
core and coils are immersed in an insulating
liquid. The insulating liquid can either be
mineral or synthetic oil. Non-flammable
liquid-immersed transformers are required for
indoor installations
230 kV Substation Seminar
Power Transformers
2. Classification according to insulation
2.2 Dry-type transformers
Dry-type transformers are those whose
core and coils are gaseous or dry compound
insulating medium. These type of transformers
are basically applied in LV up to MV systems
Power Transformers
230 kV Substation Seminar
230 kV Substation Seminar
Power Transformers
3. Classification according to location
3.1 Indoor transformers
An indoor transformer is one which,
because of construction, must be
protected from weather. They are usually
dry-type or the non-flammable oil-
immersed type.
230 kV Substation Seminar
Power Transformers
3. Classification according to location
3.2 Outdoor transformers
An outdoor transformer is of the weather-
resistant construction suitable for service
without the additional protection from the
Weather. They are usually of the mineral
oil-immersed type.
230 kV Substation Seminar
Power Transformers
3. Classification according to location
3.3 Station type transformers
Station type transformers are those designed
for installation in a power station or substation.
They are usually those that have voltages
above 34.5 kV in any of the windings.
230 kV Substation Seminar
Power Transformers
3.5 MVA Station Transformer
230 kV Substation Seminar
Power Transformers
3. Classification according to location
3.4 Padmounted transformer
A padmounted transformer is an outdoor
type used as a part of an underground
distribution system. The high and low
voltage bushings are provided with
enclosed compartments with the
corresponding cable systems entering from
below. They are mounted on a foundation
pad.
230 kV Substation Seminar
Power Transformers
3. Classification according to location
3.5 Pole-type transformers
A pole-type transformer is one which is
suitable for mounting on a pole or similar
structure.
230 kV Substation Seminar
Power Transformers
3. Classification according to location
3.5 Pole-type transformers
A pole-type transformer is one which is
suitable for mounting on a pole or similar
structure.
230 kV Substation Seminar
Power Transformers
4. Cooling Methods
Excessive heat is a catalyst to the rapid
degradation of the transformer insulation system.
It reduces the mechanical and dielectric strength
of the paper insulation. The loss of the insulation
means the loss of life of the transformer.
To safeguard the early retirement (failure) of
transformers, several factors must be taken into
consideration when loading. Each kVA rating of
a transformer is based on its rated temperature rise
of either 55oC or 65oC for oil-immersed and 55, 80,
115 and 150oC for dry type.
230 kV Substation Seminar
Power Transformers
4. Cooling Methods
ANSI and IEC differs in identifying the various
transformer cooling methods.
4.1 ANSI standard
The various types of transformer cooling
methods as provided by the ANSI
standard are identified by the type letters
as shown on Table 4.1.
230 kV Substation Seminar
Power Transformers
4. Cooling Methods
4.1 ANSI standard
The type letter identify by a slash
indicates an upgraded capacity with
forced-cooling. It is possible that the
self-cooled rating can be raised to a
higher rating of one or two steps
depending on the number of auxiliary
cooling stages and capacity.
230 kV Substation Seminar
Power Transformers
4. Cooling Methods
4.1 ANSI standard
The Three phase transformer upgraded
capacity with forced cooling is given as
follows:
501 - 2499 kVA1st stage = 1.5 self-cooled rating
2500 11999 kVa1st stage = 1.25 self-cooled rating
12000 kVa1st stage = 1.33 self-cooled rating
2nd stage = 1.66 self-cooled rating
230 kV Substation Seminar
Power Transformers
Table 4.1
230 kV Substation Seminar
1.psdPower Transformers
4. Cooling Methods
4.2 IEC standard
The identification of the type of cooling of
IEC standard transformers are identified by
four-letter symbols as described on Table 4.2.
The four-letter symbol indicating the type
of cooling is governed by the order of
arrangement of the letters given on Table 4.2.
230 kV Substation Seminar
Power Transformers
4. Cooling Methods
4.2 IEC standard
The first two symbols indicate the cooling
medium that is in contact with the windings.
The last two symbols indicate the cooling
medium that is in contact with the external
cooling system.
230 kV Substation Seminar
Power Transformers
4. Cooling Methods
4.2 IEC standard
An example of an IEC cooling designation is
ONAN which can be interpreted as follows:
ONANthe 1st letter O indicates that the
cooling medium in contact with the
winding is mineral oil.
230 kV Substation Seminar
Power Transformers
4. Cooling Methods
the 2nd letter N indicates that the
kind of circulation of the cooling
medium in contact with the winding is
natural.
the 3rd letter A indicates that the
kind of cooling medium in contact
with the external cooling system is air.
the 4th letter N indicates that the
kind of circulation of the external
cooling medium is natural.
230 kV Substation Seminar
Power Transformers
Table 4.2
230 kV Substation Seminar
230 kV Substation Seminar
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important thing is not to stop questioning.
Albert Einstein
Thank You
230 kV Substation Seminar
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