230kV-substation-seminar-eric.ppt

230 KV SUBSTATION

House Rules
Observe silence Raise hand to question Avoid side discussions Turn off your cellular phones or keep it in silent mode
230 kV Substation Seminar

Seminar Objectives
This seminar takes an in-depth look into the
components used in the transmission of electricity
Learn typical configurations of switchyards
and substation
Learn the operation of transformers, circuit breakers,
disconnects, current and potential transformers and

lightning arresters
Learn the components which make up a typical
substation and how it feeds a distribution network

that supplies customers with electricity


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


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


Introduction

1. Uses of Power Substation:
Line termination Switching Protection Metering and voltage transformation Control and stabilization between the
generating plant to the customers terminal


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.


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



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




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.



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.



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.



3. HV Disconnect Switches

Types of disconnect switches:

a) Vertical-break

b) Side-break

c) Center-break




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.



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




They are often used simultaneously for coupling

carrier frequencies to power lines for purposes

of telecommunication, remote metering, selective

line protection and control.




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.



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.



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.



7. Power System Communications:
Power line carrier (PLC) systemUse of fibre optic communication
PLC 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.



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.



8. Typical HV Outdoor Substation Layout


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.



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.



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.



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.



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/SF6245-500outdoor

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.


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


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


Power Transformers

100 MVA Power Transformer


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


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



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.


Power Transformers


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.


Power Transformers


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.


Power Transformers

3.5 MVA Station Transformer


Power Transformers


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.


Power Transformers


3.5 Pole-type transformers

A pole-type transformer is one which is

suitable for mounting on a pole or similar

structure.


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.


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.


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.


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


Power Transformers

Table 4.1

1.psd

Power 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.


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.


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.


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.


Power Transformers

Table 4.2



Learn from yesterday, live for today, hope for tomorrow. The important thing is not to stop questioning.
Albert Einstein

Thank You


230kV-substation-seminar-eric.ppt

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