PRACTICAL TRAINING REPORT

SESSION 2012-16

Submitted To Submitted By

Mr. Vikash Gupta Durgesh Maneshwar H.O.D. ID- 2012UEE1168 (Electrical Engineering Batch- E2 Department)

Department Of Electrical Engineering

ACKNOWLEDGEMENT

This summer training is of an immense academic record and value for the student of any professional course and for the Engineering student who have to be in the industry with the theoretical knowledge; this practical experience gives an extra confidence in his performance. With grateful heart I would like to remember the persons who have helped me during the course of my internship program. I wish to place on record my words of gratitude to Mr. Vikash Gupta , HoD , Department of Electrical Engineering at Malaviya National Institute of Technology, Jaipur for his efforts and for technical as well as moral support. I would like to thanks the Mr. Anurag Vats (AEN), 132kv Hybrid GSS, SMS Stadium , Jaipur that gave me the honour to complete my summer training in their substation. I would like to thanks all the employees & associates of 132kv Hybrid GSS, SMS Stadium , Jaipur who really helped me in understanding all the functions and activities of the Substation from time to time. Lastly I would like to thank all those who helped me in any way in my summer training.

1.1 NEED OF 132 KV SUBSTATION 132KV Sub-Station forms an important link between Transmission network and Distribution network. It has a vital Influence of reliability of service. Apart from ensuring efficient transmission and Distribution of power, the sub-station configuration should be such that it enables easy maintenance of equipment and minimum. interruptions in power Supply. Sub-Station is constructed as near as possible to the load center. The voltage level of power transmission is decided on the quantum of power to be transmitted to the load center. This 132 KV hybrid GSS is one of the main power supply in Jaipur city.

1.2 SPECIFICATIONS OF SMS GSS

Total cost- 28.31 crore

Total capacity – 2*50 MVA

1.3 Unique features of SMS hybrid GSS

India’s first hybrid grid substation where 145KV hybrid module and 36KV GIS is used. A conventional outdoor substation requires 25000 sq. meters for 132KV grid but hybrid

substation was constructed only in 2100 sq. meter of land area. Automatic/Scada system based on IEC 61850 standards. Digital Communication System.

1.4 Equipments installed at GSS

Two Power Transformer of capacity 50 MVA

Lightning Arrester 132KV and 33KV

Wave trap

Relays

Isolator

Bus bars

PLCC

PASS

Capacitive voltage Transformer

CHAPTER 1

1.5 FEEDERS

1.5.1 Incoming Feeders 132 KV Sanganer 132 KV Mansarovar

1.5.2 Outgoing Feeder

33kv Gautam Nagar 33kv Stadium 33kv Vidhansabha 33kv Secretariate 33kv Ramniwas Bagh 33kv Bisalpur 33kv Station

CHAPTER 2

2.1 Transformer

2.1.1 Power Transformer

Power Transformer is a static machine, which transforms the potential of alternating current at same

frequency. It means the transformer trans- forms the low voltage into high voltage and high voltage to

low voltage at same frequency. It works on the principle of static induction principle. When the energy is

transformed into a higher voltage, the transformer is called step up transformer but in case of other is

known as step down transformer.

The working principle of transformer is very simple. It depends upon Faraday's law of electromagnetic

induction. Actually, mutual induction between two or more winding is responsible for transformation

action in an electrical transformer.

Figure : Power Transformer

2.1.2 Current Transformer

A current transformer (CT) is used for measurement of alternating electric currents. Current

transformers, together with voltage (or potential) transformers (VT or PT), are known as instrument

transformers. When current in a circuit is too high to apply directly to measuring instruments, a current

transformer produces a reduced current accurately proportional to the current in the circuit, which can

be conveniently connected to measuring and recording instruments. A current transformer isolates the

measuring instruments from what may be very high voltage in the monitored circuit. Current

transformers are commonly used in metering and protective relays in the electrical power industry.

Figure :Current Transformer Figure :Capicitor Voltage Transformer

2.1.3 Capacitive Voltage Transformer

A capacitor voltage transformer (CVT or CCVT), is a transformer used in power systems to step down

extra high voltage signals and provide a low voltage signal, for metering or operating a protective relay.

In its most basic form, the device consists of three parts: two capacitors across which the transmission

line signal is split, an inductive element to tune the device to the line frequency, and a voltage

transformer to isolate and further step down the voltage for the metering devices or protective relay.

In the conventional potential transformer we use the coupling capacitor but in CVT this is eliminated and

if we use conventional Potential Transformer in yard ,this is expensive due to the fact that the

transformer ratio is high and the size of PT is high than CVT of same capacity.Thats why CVT’s are used in

substation.

2.2 CIRCUIT BREAKER

2.2.1 Introduction

A circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit

from damage caused by overload or short circuit. Its basic function is to detect a fault condition and

interrupt current flow.

2.2.2 Working

The circuit breaker actually makes a physical separation in the current-carrying or conducting element

by inserting an insulating medium sufficient to prevent current from continuing to flow. In so doing, the

persistence of an arc across the gap is prevented. opened by drawing out an arc between contacts until

the arc can no longer support itself. The arc formed when The circuit is usually the contacts of a circuit

breaker move apart to interrupt of a circuit is a conductor made up of ionized particles of the insulating

materials. Whenever voltages and currents are large other forms of insulation are used in place or air to

extinguish the arc as quickly as possible.

Whenever fault occurs in the circuit breaker, relay connected to the current transformer CT actuates

and closes its contacts. Current flows from the battery in the trip circuit As soon as the trip coil of the

circuit breaker gets energized the circuit breaker operating mechanism is actuated and it operates for

the opening mechanism.

Different types of circuit breakers are explained in subsequent sections of this chapter.

2.2.3 Types of Circuit Breaker

Oil circuit breaker

Air circuit breaker

SF6 circuit breaker

Vacuum circuit breaker

2.2.4 SF6 Circuit Breaker

A circuit breaker in which the current carrying contacts operate in sulphur hexafluoride or SF6 gas is

known as an SF6 circuit breaker.

In 132KV SMS hybrid GSS only SF6 is used.

2.3 INSULATORS

2.3.1 Introduction It is defined as “An electrical insulator is a material whose internal electric charges do not flow freely, and therefore make it impossible to conduct an electric current under the influence of an electric field.”

Figure : Insulators

2.3.2 Need of the insulators Electrical Insulator must be used in electrical system to prevent unwanted flow of current to the earth from its supporting points. The insulator plays a vital role in electrical system. Electrical Insulator is a very high resistive path through which practically no current can flow. In transmission and distribution system, the overhead conductors are generally supported by supporting towers or poles. The towers and poles both are properly grounded. So there must be insulator between tower or pole body and

current carrying conductors to prevent the flow of current from conductor to earth through the grounded supporting towers or poles. The main cause of failure of overhead line insulator, is flash over, occurs in between line and earth during abnormal over voltage in the system. During this flash over, the huge heat produced by arcing, causes puncher in insulator body. Viewing this phenomenon the materials used for electrical insulator, has to posses some specific properties.

2.3.3 Properties of Insulating Material For successful utilization, this material should have some specific properties as listed below- 1. It must be mechanically strong enough to carry tension and weight of conductors. 2. It must have very high dielectric strength to withstand the voltage stresses in High Voltage system. 3. It must possesses high Insulation Resistance to prevent leakage current to the earth. 4. The insulating material must be free from unwanted impurities. 5. It should not be porous. 6. There must not be any entrance on the surface of electrical insulator so that the moisture or gases can enter in it. 7. There physical as well as electrical properties must be less effected by changing temperature.

2.3.4 Types of Insulators There are mainly three types of insulator used as overhead insulator likewise 1. Pin Insulator 2. Suspension Insulator 3. Strain Insulator 4. Stray insulator 5. Shackle insulators

2.4 ISOLATOR

2.4.1 Introduction

Isolator is defined as “Isolator is a manually operated mechanical switch which separates a part of the

electrical power system normally at off load condition.”

2.4.2 Need of Isolators

Circuit breaker always trip the circuit but open contacts of breaker cannot be visible physically from

outside of the breaker and that is why it is recommended not to touch any electrical circuit just by

switching off the circuit breaker. So for better safety there must be some arrangement so that one can

see open condition of the section of the circuit before touching it. Isolator is a mechanical switch which

isolates a part of circuit from system as when required. Electrical isolators separate a part of the system

from rest for safe maintenance works.

2.4.3 Working

Isolator is located on both the sides of a circuit breaker. They are opened after the opening of CB and

are closed before the closing of CB. While doing maintenance on CBs, they are opened and earthing

switch is closed. They are always operated on no-load as they don’t have arc extinguishing medium

Figure : Isolato

2.5 BUSBAR

2.5.1 Introduction

In electrical power distribution, a busbar is a metallic strip or bar (typically copper, brass or aluminium) that conducts electricity within a switchboard, distribution board, substation, battery bank, or other electrical apparatus. Its main purpose is to conduct a substantial current of electricity.

There are many different electrical bus system schemes available but selection of a particular scheme

depends upon the system voltage, position of substation in electrical power system, flexibility needed in

system and cost to be expensed.

2.5.3 Types of Busbars

Single Bus System

Single Bus System with Bus Sectionalizer

Double Bus System

Double Breaker Bus System

Main and Transfer Bus System

Double Bus System with Bypass Isolators

Ring Bus System

Figure : Busbars

2.6 LIGHTNING ARRESTER

2.6.1 Introduction

A lightning arrester is a device used on electrical power systems and telecommunications systems to

protect the insulation and conductors of the system from the damaging effects of lightning. The typical

lightning arrester has a high-voltage terminal and a ground terminal.

A lighting arrester is a piece of equipment that is designed to protect electrical systems and components

from damages that can be caused by surges of electricity. Such surges can be the result of lightning or

electrical switching and can be very dangerous, especially for power system equipment.

Different types of LA’S are explained in subsequent sections of this chapter

2.6.2 Types of Lightning Arrester

Rod gap arrester

Horn gap arrester

Multigap arrester

Expulsion type arrester

Valve type arrester

General rating Recommendation for lightning arrester

1. 10kv rated lightning arrester- Arrester of this type are used in case of power station and

EHV substation

2. 5kA rated lightning arrester- Arrester of this capacity normally are used in case of high

voltage substations having system voltages as 66 kV or less.

3. 2.5 kA rated lightning Arrester- - Arrester of these ratings are used in case of system upto

11 KV.

4. 1.5 KA rated lightning Arrester- Arrester of these ratings are used in case of distribution

system.

Location of lightning arrester

1. Very close to the equipment to be protected and connected with shortest lead on both the

linesandground side to reduce the inductive effect of leads while discharging the surge current.

2. In order to ensure the protection of transformer windingsit is desirable to inter connect the

ground lead of the arresterwith the tank and also the neutral of secondary. This interconnection

reduces the stress imposed on the transformer windings by the surge current.

Figure : Lightning Arrester

.

2.7 PLCC

2.7.1 Introduction

Power Line Carrier Communication(PLCC), is an approach to utilize the existing power lines for the

transmission of information. In today’s world every house and building has properly installed electricity

lines. Power Line Carrier Communication – PLCC By using the existing AC power lines as a medium to

transfer the information, it becomes easy to connect the houses with a high speed network access point

without installing new wirings

2.7.2 Need of PLCC

Different communication technologies are being used for the transmission of information from one end

to another depending on the feasibility and needs. Some include Ethernet cables, fiber optics, wireless

transmission, satellite transmission, etc. A vast amount of information travels through the entire earth

every day and it creates an essential need for a transmission medium that is not only fast but

economically reasonable as well. One of the technologies that fit in the above stated criteria is PLCC..

2.7.3 Operation

The voice/data are mixed with radio frequency carrier (40-500kHz), amplified to a level of 10-80W RF

power and injected in to high voltage power line using a suitable coupling capacitor. The power line

as a rigid long conductor parallel to ground, guides the carrier waves to travel along the transmission

line.

2.8 Wave trap

Wave Traps are used at sub-stations using Power Line Carrier Communication (PLCC). PLCC is used to

transmit communication and control information at a high frequency over the power lines. This reduces

need for a separate infra for communication between sub-stations.

Figure : PLCC and Wavetrap

CHAPTER 3

3.1 What is GIS?

A gas insulated substation is an electrical substation in which the major structures are contained in a

sealed environment with sulfur hexafluoride gas (SF6) as the insulating medium. Gas insulated

substations originated in Japan where the there a major need to develop technology that would allow

substations to be made as compact as possible.

3.2 why Gas Insulated Substations are

used ?

Gas Insulated Substations are used where there is space for providing the substation is expensive in

large cities and towns. In normal substation the clearances between the phase to phase and phase to

ground is very large. Due to this, large space is required for the normal or Air Insulated Substation (AIS).

But the dielectric strength of SF6 gas is higher compared to the air, the clearances required for phase to

phase and phase to ground for all equipments are quite lower. Hence, the overall size of each

equipment and the complete substation is reduced to about 10% of the conventional air insulated

substation.

3.3 ADVANTAGES OF GIS TECHNOLOGY

1- Compactness. The space occupied by SF6 installation is only about 8 to 10 % of that a conventional

outdoor substation. High cost is partly compensated by saving in cost of space.

2- Choice of Mounting Site. Modular SF6 GIS can be tailor made to Suit the particular site requirements.

This results is saving of otherwise Expensive civil-foundation work. SF6 GIS can be suitably mounted

indoor on any floor or basement and SF6 Insulated Cables (GIC) can be taken through walls and

terminated through SF6 bushing or power cables.

3- Reduced Installation Time- The principle of building block construction (modular construction)

reduces the installation time to a few weeks. Each conventional substation requires several months for

installation. In SF6 substations, the time-consuming high cost galvanized steel structures are eliminated.

Heavy foundations for galvanized steel structures, Equipment support structures etc are eliminated. This

results in economy and reduced project execution time. Modules are factory assembled, tested and

dispatched with nominal SF6 gas. Site erection time is reduced to final assembly of modules.

4- Protection from pollution. The external moisture. Atmospheric Pollution, snow dust etc. have little

influence on SF6 insulated substation. All live parts are hermetically enclosed in the gas chamber & are,

thus, independent from environmental influences like rusting, ageing, atmospheric faults etc.

However, to facilitate installation and maintenance, the substations are generally housed inside a small

building.

5- Increased Safety. As the enclosures are at earth potential there is no possibility of accidental contact

by service personnel to live parts. Also continuous & robust mechanical interlocking systems ensure

maximum operating stability & operator safety.

6- Explosion-proof and Fire-proof installation. Oil Circuit Breakers and oil filled equipment are prone to

explosion. SF6 breakers and SF6 filled equipment are explosion proof and fire-proof.

7- Easy operation and long life

Operation of GIS is simple, user friendly and through safe mechanism. As all GIS is enclosed in sealed

chamber it provides long service life and low maintenance cost.

3.4 Why SF6 gas is used?

SF6 has excellent insulating property. SF6 has high electro-negativity. That means it has high affinity of

absorbing free electron. Whenever a free electron collides with the SF6 gas molecule, it is absorbed by

that gas molecule and forms a negative ion.

The attachment of electron with SF6 gas molecules may occur in two different ways,

These negative ions obviously much heavier than a free electron and therefore over all mobility of the

charged particle in the SF6 gas is much less as compared other common gases. We know that mobility of

charged particle is majorly responsible for conducting current through a gas.

Hence, for heavier and less mobile charged particles in SF6 gas, it acquires very high dielectric strength.

Not only the gas has a good dielectric strength but also it has the unique property of fast recombination

after the source energizing the spark is removed. The gas has also very good heat transfer property. Due

to its low gaseous viscosity (because of less molecular mobility) SF6 gas can efficiently transfer heat by

convection. So due to its high dielectric strength and high cooling effect SF6 gas is approximately 100

times more effective arc quenching media than air. Due to these unique properties of this gas SF6 circuit

breaker is used in complete range of medium voltage and high voltage electrical power system. These

circuit breakers are available for the voltage ranges from 33KV to 800KV and even more.

CHAPTER 4

3.1 WHAT IS PASS? Here term “Hybrid system” refers to the combination of both conventional air insulated switchgear (AIS)

and newer SF6 metal clad insulated switchgear (GIS) which takes advantage of the two different

technologies.The hybrid switchgear solution uses already existing, tried and tested gas insulated

switching components but also a conventional and very reliable AIS bus to connect the various hybrid

modules. All the functions( except the ring type current transformer) are sealed in single SF6 gas

insulated housing.

Circuit breaker Disconnectors Earth switches Cable sealing ends Fast earthing switches SF6 VT’s or voltage sensors

Figure : PASS

3.2 Components of PASS

1. Gas density Control

Each PASS pole has a single gas compartment. Since the dielectric strength of the switchgear and the breaking capacityof the SF6 circuit breaker depend on the density of SF6 gas, a gas density relay is installed to control gas density and detect leakage.

2. Voltage Transformer PASS can be equipped with a conventional GIS inductive voltage transformer.

3. Combined Disconnector/earth switch PASS is equipped with combined disconnector/earthing switch. The mechanism has minimal number of mechanical components and is intrinsically reliableand maintenance free. All combinations are possible.

4. Current Transformer PASS is equipped with a conventional transformer to meet the customers requirement. E.g. for retrofitting. Several combination of cores for protection and measurement with different load are available.

CHAPTER 4

4.1 What Is scada system It is defined as -“SCADA (supervisory control and data acquisition) is a system operating with coded signals over communication channels so as to provide control of remote equipment (using typically one communication channel per remote station) .” There is a SCADA system in the SMS Hybrid Substation based on IEC 61850 standard.

4.2 Need of SCADA system

Substations are a critical component for maintaining electrical supply and load control in low voltage,

medium voltage and high voltage electrical distribution networks. In order to ensure the proper

functioning of substations and related equipment such as line-mounted switches and capacitors, most

utilities use SCADA (supervisory control and data acquisition) systems to automate monitoring and

control.

4.3 Working

Electrical distribution systems involve many remote applications and sites, and monitoring and

controlling these sites has often been difficult. To solve this problem, utilities began installing remote

terminal/telemetry units (RTUs) at substations. Early RTUs were initially custom-made units, but later

versions relied on standard hardware such as programmable logic controllers (PLCs) or industrial PCs.

Intelligent electronic devices (IEDs) are a more recent technology development, and these devices are

now installed at most substations to some extent. These IEDs generally communicate with the

substation RTU.

Power distribution to various electrical loads at substations is controlled by switchgear feeders. Sensors

mounted on the switchgear collect various data on current, voltage, power and switchgear status. This

data is transferred to the RTU, which is in turn polled by a SCADA system.

The SCADA system consists of a master control station with one or more PC-based human machine

interfaces (HMIs). The SCADA system may also contain other secondary control stations with HMIs, and

large substations may also have local HMIs.

Operators view information on the HMIs to monitor and control substation operations and related

equipment.

CHAPTER 5

5.1 RELAY Relay is a device which detects fault current and energizes trip circuit of circuit breaker. A relay is an electrically operated switch. Different Relay used

Current Relay Voltage Relay Power Relay Directional Relay Differential Relay Distance Relay

Figure :Relay Panel in SMS hybrid GSS

5.2 TRANSFORMER PROTECTION

Buccholz relay protection

Differential protection

Pressure releasedevice(PRD) Oil surge relay protection

Backup protection

WTP(winding temperature protection) OTP(oil temperature protection) Over flux Protection

Fire flighting Protection

5.3 protection for TRANSmission line

feeder

Differential backup protection

Differential relay protection

5.4 FIRE PROTECTION

Figure : FIRE Protection

CHAPTER 6

6.1 CONTROL ROOM

6.1.1 Introduction

At control room , remot control not only carry the appropriate mean s by which circuit breaker may be

open or close but also necessary indicating devices , indicating lamps, isolating switching, protective

relays, secondary circuit and wires are located here and most important “No load Tap Changer” for

transformer is available. There is a panel for synchronizing .

Different panels are located in different stages and on each panel control switch is provided on the

board. The control switches for each circuit breaker and isolators are provided on control panel. Color of

signals are synchronized as follows-

Red- For circuit breaker or isolator is in closed position.

Green- For circuit Breaker is in open position

Amber-Indicate abnormal condition requiring action.

Supervisory control and data acquisition(SCADA)

For power system operation and control SCADA system is used which includes-

Data collection system

Data transmission telemetric equipment

Data monitoring Equipment

Man/machine interface

Detail of SCADA has already explained in earlier chapter.

Operation

The operation in control room needs information regarding parameters and configuration according to

feeders. It has different units

Indicating system

Control Switches

Relay Section

Meter Section

Announcing Section

DC Supply system

Transformer control unit

Announcing Section

This section is always checked by shift incharge.If any fault or alarm swing or any abnormal condition

then type o fault is indicated on announcing box The most important section is transformer control

section, winding temperature indicator.

Tap position selector is situated on control panel. A control engineer controls the loading of various

lines,outgoing feeders, synchronizing the incoming lines with bus bars.

Control and relay panel

The arrangement of control and relay power is such that the indicating apparatus is clearly visible from

control space. These respective panels are provided-

Control and indicating equipment

Relay and recording equipment

Indicating system

Indicating system is used to indicate total load, bus bar voltage indication of circuit breaker, isolator

position.

Relay section

Relay section indicate position of different realy at different feeder. Fault at any feeder is denoted by

corresponding relay that gives alarm signal.Master relay gives signal to trip coil of circuit breaker and

thus faulty feeder is disconnected from supply.

Figure 1 Control Room at 132KV SMS GSS

6.2 Battery Room

In GSS, DC supply is maintained for signaling remote position control. Alarm circuit etc. Direct current

can be obtained from 220 v 3 phase ac supply via rectifier and in event of ac failure , from fixed battery

which are kept charged in normal condition by rectifier supply.

Figure 2 Battery Room at 132KV SMS GSS