SEMINAR REPORT

ON

400Kv GRID SUBSTATION

HEERAPURA

ACADEMIC SESSION 2013-14

SUBMITTED TO: - SUBMITTED BY:-

MR. ANOOP MAHESHWARI ROHIT NAIR

(EXECUTIVE ENGINEER ) VIT

ELECTRICAL

A CKNOWLEDGEMENT

Words fail me to express my sincerest gratitude to this esteemed organization, which has

conferred on us the privilege to pragmatically convert our theoretical knowledge into practical

viable experience. During the course of my training at 400Kv GSS HEERAPURA, JAIPUR so

many people have guided me and I will remain indebted to them throughout my life for making

my training a wonderful learning experience.

I would like to thank MR. ANOOP MAHESHWARI my project head, who gave me

opportunity to work in his department and guided me through my project from time to time. His

words were a true inspiration for me. The exposure that I have got here would not have been

possible without his kind support.

He took keen interest in my project and ensured that my tenure here is a learning experience for a

lifetime for me.

I would like to thank MR. A.P VISHNU sir and all those operators, Diploma Engineer Trainees

and my trainee colleagues with whom I had developed a special bond.

PREFACE

As per the requirement of B. Tech. Course,400Kv GSS HEERAPURA, JAIPUR (RAJ.) has

been kind enough to permit me to complete my Practical Training of 30 days.

This report prepared during the practical training which is student’s first and greatest treasure as

it is full of experience, observation and knowledge.

The summer training was very interesting and gainful as it is close to real what has been studied

in all the years through was seen implemented in a modified and practical form.

GSS is the means of connection between generating station and consumer by providing safety

and reliability of system in case of default. 

This substation step down the incoming  voltage  power transmission to the required valve and

then  is supplied to the consumer feeder or GSS done by connecting auto transformer operation

and requirement of  various equipment have been include in detail , further in case of report is

the bus bar. 

Arrangement of different feeder level and switch yards  included information of  bus bar

arrangement of different  level  isolator and  growing substation also power transformer circuit

breaker oil, filtration plant, and compression protection control room and place are leveled.     

CONTENTS

1.Introduction

2.Equipments in G.S.S.

3.Transformer

4. Bus Bar

5.Circuit breaker

6.Lightening arrestor

7.Isolator

8.Current Transformer

9.Capacitive Voltage Transformer

10.Wave Trap

11.Relays

12.Oil Testing Lab

13.Earthing

14.PLCC

15.Control room

16.Conclusion

INTRODUCTION

    

When India became independent, the overall installed capacity was hardly 1900 mw. During

first year plan (1951-1956) this capacity was only 2300 mw. The contribution of Rajasthan state

was negligible during 1&2 year plans the emphases was on industrialization for that end it was

considered to make the system of the country reliable. Therefore Rajasthan state electricity board

came into existence in July 1957.

In India electrical power is generated at a voltage of 11KV to 33 KV, which is taken 

stepped up to the transmission level in the range of 66 KV to 400 KV Member of transmission

and switching have to be created. These are known as “SUB STATION”. Along these

transmission lines secondary substation are created where voltage is further stepped down to sub

transmission and primary distribution voltage. A substation is an assembly of apparatus, which

transform the characteristics of electrical energy from one form to another say from one voltage

level to another level. Hence a substation is an intermediate link between the generating station

and consumer. For economic transmission the voltage should be high so it is necessary to step up

the generated voltage for transmission and step down transmitted voltage for distribution. For

this purpose substations are installed. The normal voltages for transmission are 400kv, 220kv,

132kv and for distribution 33kv, 11kv etc.

The 400 kV G.S.S. HEERAPURA RAJASTHAN RAJYA VIDYUT PRASARAN

NIGAM Ltd. (R.R.V.P.N.L.) is ideally located at the Heerapura ajmer road Jaipur Rajasthan.

G.S.S. is the means of connection between Generating Station & Consumers

(Industrial & Domestic etc.) by providing safety & reliability of whole system in case of fault.

A G.S.S. is an assembly of apparatus, which transform the characteristics of

electrical energy from one form to another say from one voltage level to another level. Hence a

G.S.S. is an intermediate link between one G.S.S. to consumers. For economic transmission the

voltage should be high so it is necessary to step up the generated voltage for transmission and

step down transmitted voltage for distribution. The normal voltages for transmission are 400 kV,

220 kV, 132 kV and for distribution 33 kV, 11 kV etc.

In Rajasthan, R.R.V.P.N.L. is responsible for transmission and distribution of

electrical power all over Rajasthan.

The steps of this sub-station are:- To step down the incoming voltage of the power transmission

to a required value i.e. 400 kV to 220 kV &132 kV and further.

There are three incoming lines from different four sub-stations.

These are:-

• Heerapura is connected to Bassi via two lines of 400kV named Bassi1 and Bassi2.

• Heerapura is connected to 400kV Merta line.

• Heerapura is connected to 400kV Hindaun line.

EQUIPMENTS IN G.S.S

2.1 EQUIPMENTS AVAILABLE IN THE HEERAPURA400kV G.S.S. JAIPUR, RAJASTHAN

• Transformer(400kV)

I.D. NO. MAKE CAPACITY VOLTAGE(kV) CURRENT

ILT-1 TELK 250MVA 400/200/33 361/656A

ILT-2 DO DO DO DO

ILT-3 DO DO DO DO

ILT-4 DO 315MVA DO 455/828A

• C-Transformer(400kV)

SR.NO.

ID.NO. MAKE

TYPE VOLTAGE(kV)

RATIO

1. SCTA,SCTTA,SCTTB,SCTB

WS ATS 400/2

420/630/142 2000/1000/300/1

2. 4CTA,4CTTA,4CTTB,4CTB

DO DO DO DO

3. 2CTA,2CTTA DO DO DO DO 4. 2CTB,2CTTB ABB TMBRL

-420DO 455/828A

• C.V.Transformer(400KV)

SR.NO. ID.NO MAKE/TYPE RATIO BURDEN CLASS SEC,CAP

1. BASSI-1 WSI/CVE420/1425 400 200,200,100 3P,3P,0.5 80,000PF 2. BASSI-2 DO DO DO DO DO 3. BUS-1 DO DO DO DO DO 4. BUS-2 DO DO DO DO DO

• C.V.Transformer (220KV)

S.No

ID.NO. MAKE/TYPE RATIO BURDEN CLASS SEC,CAP

1. BUS-D CROMPTON 220/3KV/110/3,110,110/3V

200,100,100

5/3P,3P,3P 48,400PF

2. BUS-E WSI/CVE/245

DO 200,200,200

3P,3P,3P/0.5

DO

3. BUS-F DO DO DO DO DO 4. PHULER

ADO 220/3kV/110,110/3V 200,200 0.5,0.5 DO

5. KTPS-1 HBB245-N 220/3KV/110/3,110V DO DO DO 6. KTPS-2 CROMPTON 220/3kV/100/3,110/3V DO DO DO 7. KOTA-3 WSI DO DO DO DO

• Circuit Breaker (400kV)

SR.NO.

ID.NO.

.MAKE TYPE VOLTAGE(KV)

CURRENT

STC DCF

SFG/HYD

1. 552A BHEL 3AT 420/520/1050,1425

2000A 40KA/1S 29,000MVA

1.3 7.5/350

2. 552T DO DO DO DO DO DO DO 3. 552B M.G.

(FRAN)FA2R DO 3150 DO DO 7/300

4. 552T NGEF S2-M420 420/610/1425 2000 DO DO 8.0/35(PN)

5. 252A BHEL 3AT3 420/520/1050/1425

2000 DO DO 7.5/250

6. 552T DO DO DO DO DO DO DO 7. 252B ABB EL(V)FS

L6-2420/1050,1425

3150 40KA/3S DO 7.0/31.5

• Circuit Breaker(220kV)

SR.NO. ID.NO. MAKE TYPE VOLTAGE(KV) CURRENT

1. 2452C NGEF S1-245 245/460/1050 2000A 2. 2352C DO DO DO DO 3. 2052C DO DO DO DO 4. 1652D DO DO DO DO 5. 1652C DO DO DO DO 6. 2259C ABB ELFSL4-1 245/1000KV DO 7. 1852C DO DO DO DO 8. 1752D DO DO DO DO 9. 1652G DO DO DO DO 10. 2252D HVV DLF-

245NC-2245/460/1050KV

DO

11. 2152D DD DO DO DO 12. 1952C ABB ELFSL4-1 245/1050KV 3150A

• Lightning Arrester(400KV)

SR.NO. ID.NO. .MAKE TYPE VOLTAGE(KV)

CURRENT

1. BASSI-1 WSI CPL 360KV 10KA 2. BASSI-2 PLPRO ALUGARD-

2DO DO

3. ILT-1 DO DO DO DO 4. ILT-2 DO DO DO DO 5. ILT-3 WSI 10KA 890KV 10KA 6. ILT-4 DO DO DO DO

• Lightning Arrester(220KV)

SR.NO. ID.NO. MAKE TYPE VOLTAGE(KV) CURRENT 1. ILT-1 ELPRD ALUGARD-

2DO DO

2. ILT-2 ELPRD ALUGARD-2

DO DO

3. ILT-3 DO DO DO DO 4. ILT-4 DO DO DO DO 5. KTPS-1 OBLUM METOVAR DO DO 6. KTPS-2 WSI CPL-2 DO DO 7. KOTA-3 WSI CPL-2 DO DO 8. PHULERA AEG 4S204 204 DO

• Isolators(400kV)

S.No. ID.NO. MAKE TYPE VOLTAGE(KV) CURRENT STC 1.

589AAAB(S/EB) S&S RC500 MGB

420/1425 2000A 40KA/1S

2.

589AL,(D/EB) DO DO DO DO DO

3.

589A,589B(S/EB) DO DO DO DO DO

4.

589BA,BB(S/EB) RADE-KONKAR

RVZ420-3-20-LD

DO DO DO

5.

689AL(D/EB) DO DO DO DO DO

6.

89VT-182(D/EB) S&S RC500MGB

DO DO 40KA/3S

7.

489BA,BC,AB,AC(S/EB) DO DO DO DO DO

8.

289BA,BB(S/EB) DO DO DO DO DO

9.

289BA,BB(S/EB) MULLER&CO

………. DO DO DO

10.

189BT(D/EB) DO ……….. DO DO DO

• Isolators(220kV)

SR.NO. I.D.NO. MAKE TYPE RATING E/B MECHANISM STC 1. 2489CC S&S RC500 2000 DEB MOTOR 40KA/3S 2. 2489CA S&S RC500 2000 SEB MOTOR 40KA/3S 3. 2489CA

AS&S RC500 2000 SEB MOTOR 40KA/3S

4. 2389CC S&S RC500 2000 DEB MOTOR 40KA/3S 5. 2389CA S&S RC500 2000 SEB MOTOR 40KA/3S 6. 2289CB SE RC500 2000 SEB MOTOR 400KA/3S 7. 2389CD S&S RC500 2000 W/EB MOTOR 40KA/1S 8. 2289CC SE RC500 2000 DEB MOTOR 40KA/3S 9. 2289CB S&S RC500 2000 D/OEB MOTOR 40KA/1S 10. 89VTF UNISO RC500 2000 SEB MOTOR 40KA/3S 11. 2289DV OBLUM 220ABSA2 8000 DEB MANUAL 20KA/1S 12. 2289DA OBLUM 220ABSA2 8000 DEB MANUAL 20KA/1S 13. 2289DC OBLUM 220ABSA2 8000 SEB MANUAL 20KA/1S 14. 2189DA OBLUM 220ABSA2 8000 D/OEB MANUAL 20KA/1S 15. 2189DC OBLUM 220ABSA2 8000 D/OEB MANUAL 20KA/1S 16. 2089DB UNISO 220ABSA2 8000 SEB MANUAL 20KA/1S 17. 2089DC UNISO 220ABSA2 8000 SEB MANUAL 20KA/1S 18. 2089DD SE 22ABSD2 8000 W/OEB MANUAL 20KA/1S 19. 2089CC SE DB 2000 W/OEB MOTOR 40KA/1S 20.. 1889CC S&S DB 2000 W/OEB MOTOR 40KA/1S 21. 1889CA ELECTRONICS DB 2000 DEB MOTOR 40KA/3S 22. 1889CB ELECTRONICS RC500 2000 W/DEB MOTOR 40KA/1S 23. 1889CD ELECTRONICS RC500 2000 SEB MOTOR 40KA/1S 24. 1889 ELECTRONICS RC500 2000 W/DEB MOTOR 40KA/1S 25. 1889 ELECTRONICS RC500 2000 W/DEB MOTOR …………. 26. 1889CC HIVELM RC500 800 W/DEB MOTOR …………. 27. 1889CB HIVELM RC500 800 SEB MOTOR …………. 28. 1889CA HIVELM RC500 800 W/DEB MOTOR …………. 29. 1789DA AMEL RC500 800 W/DEB MOTOR …………. 30. 1789DB HIVELM HPPR-

SHME3800 W/DEB MOTOR ………….

31. 1789DC HLM HPS 800 W/DEB MOTOR …………. 32. 1689GG SE HPS 2000 W/DEB MOTOR …………. 33. 1689GF SE HPS 2000 SEB MOTOR …………. 34 1689CE S&S RC500 2000 SEB MOTOR …………. 35 1689CC S&S RC500 2000 SEB MOTOR …………. 36. 1689DB S&S RC500 2000 SEB MOTOR 40KA/3S 37. 1689DD S&S RC500 2000 SEB MOTOR 40KA/3S

TRANSFORMER:

A transformer is a static electrical device that transfers energy by inductive coupling between its

winding circuits. A varying current in the primary winding creates a varying magnetic flux in the

transformer's core and thus a varying magnetic flux through the secondary winding. This varying

magnetic flux induces a varying electromotive force (emf) or voltage in the secondary winding.

The transformer is based on two principles: first, that an electric current can produce a magnetic

field and second that a changing magnetic field within a coil of wire induces a voltage across the

ends of the coil (electromagnetic induction). Changing the current in the primary coil changes

the magnetic flux that is developed. The changing magnetic flux induces a voltage in the

secondary coil.

TYPES OF TRANSFORMER :

1.Autotransformer: Transformer in which part of the winding is common to both primary and

secondary circuits.

2.Capacitor voltage transformer: Transformer in which capacitor divider is used to reduce

high voltage before application to the primary winding.

3.Phase angle regulating transformer: A specialized transformer used to control the flow of

real power on three-phase electricity transmission networks.

4.Scott-T transformer: Transformer used for phase transformation from three-phase to two-

phase and vice versa.

5.Polyphase transformer: Any transformer with more than one phase.

6.Grounding transformer: Transformer used for grounding three-phase circuits to create a

neutral in a three wire system, using a wye-delta transformer,[76][81] or more commonly, a

zigzag grounding winding.

7.Leakage transformer: Transformer that has loosely coupled windings.

8.Resonant transformer: Transformer that uses resonance to generate a high secondary voltage.

9.Audio transformer: Transformer used in audio equipment.

10.Output transformer: Transformer used to match the output of a valve amplifier to its load.

11.Instrument transformer: Potential or current transformer used to accurately and safely

represent voltage, current or phase position of high voltage or high power circuits.

BUS BARS:

There are several ways in which the switching equipment can be connected in the electrical layout of substation in a distribution system. The selection of the scheme is in general affected by following aspects.

• Degree of flexibility of operations desired.

• Importance of load and local condition freedom from total shutdown and its period desired.

• Economic consideration, availability and cost.

• Technical consideration.

• Maintenance, safety of personnel.

• Simplicity

• Provision of extension.

• Protective Zones.

With these basic requirements, there are several combinations such as

• Single bus – bar arrangement

• Duplicate bus- bar arrangement

• Ring bus

• One & a half breaker arrangement

• Mesh arrangement

• Sectionalization of bus

Of this arrangement single bus bar arrangement is employed at 400 KV GSS, Heerapura. In single bus bar arrangement bus bar is split into sections by means of a bus sectionalizer. Single bus bar is easier to use, readily is less (equipment, site procedure, understood by operators, requires less maintenance, spares holding and space). Typical installation consist of basic cubicle types, that can be combined together to form the required switgear.

CIRCUIT BREAKER:

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. Unlike a fuse, which operates once and then must be

replaced, a circuit breaker can be reset (either manually or automatically) to resume normal

operation. Circuit breakers are made in varying sizes, from small devices that protect an

individual household appliance up to large switchgear designed to protect high-voltage circuits

feeding an entire city.

Types of circuit breaker:

1.Oil circuit breaker

2.Air blast circuit breaker

3.SF6 circuit breaker

4.Vaccum circuit breaker

5.Water circuit breaker

6.Air break circuit breaker

Generally SF6 circuit breakers are used on 400KV GSS.

SF6 Circuit Breaker:SF6 circuit breakers work through arc interruption. When electrical

current exceeds a certain level (called a rating), the breaker will trip and contacts within the

circuit breaker.

As the breaker is tripped, a magnetic coil is beneath it and as the movable contact falls into the

coil the arc is elongated in a spiral caused by the magnetic coil until the SF6.

Several Characteristics of SF6 circuit breakers can explain their success:

• Simplicity of the interrupting chamber which does not need an auxiliary

breaking chamber.

• Autonomy provided by the puffer technique.

• The possibility to obtain the highest performance, up to 63 kA, with a reduced

number of interrupting chambers.

• Short break time of 2 to 2.5 cycles.

• High electrical endurance, allowing at least 25 years of operation without

reconditioning.

• Possible compact solutions when used for gas insulated switchgear or hybrid

switchgear.

LIGHTENING ARRESTOR : A protective device for electrical equipment that reduces excessive voltage resulting from

lightning to a safe level by grounding the discharge.A device designed to protect electrical

equipment from high transient voltage and to limit the duration and frequency the amplitude of

follow-current. Surge arrester are usually connected the electrical conductors of a network and

earth though they may.

Types of Lighting Arrester:

Originally, three types of surge arresters. They are:

1. Expulsion type: This type of arrester is also called ‘protector tube’ and is commonly used on

system operating at voltages up to 33kV. It essentially consists of a rod gap AA’ in series with

the protector tube. The upper electrode of protector tube is connected to rod gap and the lower

electrode to the earth.

2. Valve Type Arrester: Valve type arresters incorporate non linear resistors and are extensively

used on systems, operating at high voltages. It consists of two assemblies (i) series spark gaps

and (ii) non-linear resistor discs in series.

3. Gapless metal-oxide type: The gapless metal-oxide type arresters are the most widely used

today. The metal oxide lightning arrester is the most advanced over-voltage protector. It is

widely used as protective devices against switching and lightning over voltages in power

electrical systems such as power transformers, distributors, generators, compensation capacitors.

CHARACTERISTICS OF LIGHTENING ARRESTOR:-

STABILITY: -It should remain in operation during normal conditions even under polluted

atmosphere.

RESPONSE:-Protective device should have means of sensing the transient appearing across its

terminals very quickly.

PROTECTION:-After passes the surge current the power frequency current which is called

“power flow current” through the arrestor

ISOLATOR:

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.

So definition of isolator can be rewritten as Isolator is a manually operated mechanical switch

which separates a part of the electrical power system normally at off load condition.

Depending upon the position in power system, the isolators can be categorized as:

Bus side isolator – the isolator is directly connected with main bus

Line side isolator – the isolator is situated at line side of any feeder

Transfer bus side isolator – the isolator is directly connected with transfer bus.

Types of Electrical Isolators:

There are different types of isolators available depending upon system requirement such as:

1. Double Break Isolator

2.Single Break Isolator

3.Pantograph type Isolator

400 KV SIDE ISOLATORS RATINGS:-

• Operating Voltage: 400kV

• Current Capacity : 2000A

• Frequency: 50 Hz

• Operator Motor: 415V ac

• The isolator used is a centre break, off load type isolator

220 KV SIDE ISOLATORS RATINGS:-

• Type: HCB

• Voltage: 220 kV

• Frequency: 50Hz

• Operating motor voltage: 415 V

• Control Voltage: 220V

CURRENT TRANSFORMER:

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

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

as instrument transformers. When current in a circuit is too high to directly apply 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 also 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.

The accuracy of a CT is directly related to a number of factors including:

1.Burden

2.Burden class/saturation class

3.Rating factor

4.Load

5.External electromagnetic fields

6.Temperature

7.Physical configuration.

8.The selected tap, for multi-ratio CTs.

A Current Transformer

On construction basis that the current transformers may be divided as:

Bar type C.T.:-

A current transformer in which the primary winding consist of a bar of

suitable size and material forming an integral part of transformer. For large primary current the

bar type construction is ideal because it can meet with the burden and accuracy requirement and

the same time can have high thermal and dynamic short time factors. This type of construction is

very sturdy. This may be further sub-divided.

• Separately mounted type

• Bushing type

Wound Type C.T :-

A current transformer having a primary winding of more than one full turn

wound on core. Where the primary currents are low on the burden and accuracy requirements

are high. Primary winding consist of a number of turns normally not exceeding 5. The primary

number of turns depends on the primary current. The greater the number of turns lesser the

thermal and dynamic short time current factors.

The use of one of the other is determined by the rated current of the apparatus and the rated

burden required.

Selection of C.T.:-The following points need to be considered while selecting a C.T.

• Type.

• Number of Secondary.

• Accuracy class of each secondary.

• Rated burden.

• Accuracy limit factor.

• Short time current rating.

CAPACITIVE VOLTAGE TRANSFORMER (CVT):

A capacitor voltage transformer (CVT), or capacitance coupled voltage transformer (CCVT) is a

transformer used in power systems to step down extra high voltage signals and provide a low

voltage signal, for measurement or to operate 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 transformer to isolate and

further step down the voltage for the instrumentation or protective relay. The tuning of the

divider to the line frequency makes the overall division ratio less sensitive to changes in the

burden of the connected metering or protection devices.

The device has at least four terminals: a terminal for connection to the high voltage signal, a

ground terminal, and two secondary terminals which connect to the instrumentation or protective

relay. CVTs are typically single-phase devices used for measuring voltages in excess of one

hundred kilovolts where the use of wound primary voltage transformers would be uneconomical.

In practice, capacitor C1 is often constructed as a stack of smaller capacitors connected in series.

This provides a large voltage drop across C1 and a relatively small voltage drop across C2.

The CVT is also useful in communication systems. CVTs in combination with wave traps are

used for filtering high frequency communication signals from power frequency. [2] This forms a

carrier communication network throughout the transmission network.

A Capacitive Voltage Transformer

WAVE TRAP:

Wave Trap is the instrument which used to reduce the corona loss in transmission line in power

system and in this a parallel tuned inductor -capacitor tank circuit made to be resonant at the

desire communication it effort to utilize the same transmission between two substations for the

purpose of communication. Wave trap is a parallel tuned inductor - capacitor 'tank' circuit made

to be resonant at the desired communication frequency.

It is the effort to utilize the same transmission line between two substation for the purpose of

communications.

At this communication frequency the tank circuit provides high impedance and does not allow

to pass through them & onto the substation bus & into transformers.

It is used to trap the communication signals & send PLCC room through CVT.  

Rejection filters are known as the line traps consisting of a parallel resonant

circuit ( L and C in parallel) tuned to the carrier frequency are connected in series

at each and of the protected line such a circuit offer high impedance to the flow of

carrier frequency current thus preventing the dissipation. The carrier current used

for PLC Communication have to be prevented from entering the power equipments

such as attenuation or even complete loss of communication signals. For this

purpose wave trap or line trap are used between transmission line and power

station equipment to- 

Avoid carrier power dissipation in the power plant reduce cross talks with other

PLC Circuits connected to the same power station.

Ensure proper operating conditions and signal levels at the PLC transmit

receive equipment irrespective of switching conditions of the power circuit and

equipments in the stations. 

    

    Line Matching Filter & Protective Equipments

For matching the transmitter and receiver unit to coupling capacitor and power line

matching filters are provided. These flitters normally have air corral transformers

with capacitor assumed.

The matching transformer is insulated for 7-10 KV between the two windings and

perform two functions. Firstly, it isolates the communication equipment from the

power line. Secondly, it serves to match .

 

Figure-4.1 Line Matching Filter & Protective Equipments

Transmitter

The transmitter consists of an oscillator and a amplifier. The oscillator generates

a frequency signal with in 50 to 500 HZ frequency bands the transmitter is

provided so that it modulates the carrier with protective signal. The modulation

process usually involves taking one half cycle of 50 HZ signal and using this to

create block to carrier.    

Receivers 

The receivers usually consist of and alternate matching transformer band pass

filter and amplifier detector.

The amplifier detector converts a small incoming signal in to a signal capable of

operating a relatively intensive carrier receiver relay. The transmitter and receiver

at the two ends of protected each corresponds to local as far as transmitting. 

RELAYS:

A relay is an electrically operated switch. Many relays use an electromagnet to operate a

switching mechanism mechanically, but other operating principles are also used. Relays are used

where it is necessary to control a circuit by a low-power signal (with complete electrical isolation

between control and controlled circuits), or where several circuits must be controlled by one

signal. The first relays were used in long distance telegraph circuits, repeating the signal coming

in from one circuit and re-transmitting it to another. Relays were used extensively in telephone

exchanges and early computers to perform logical operations.

1. Buchholz relay

It is a safety device sensing the accumulation of gas in large oil-filled transformer which will

alarm on slow accumulation of gas or shut down the transformer if gas is produced rapidly in the

transformer oil.

2.Overload protective relay

Electric motors need overcurrent protection to prevent damage from over-loading the motor, or

to protect against short circuits in connecting cables or internal faults in the motor windings .The

overload sensing devices are a form of heat operated relay where a coil heats a bimetallic stripor

where a solder pot melts, releasing a spring to operate auxiliary contacts. These auxiliary

contacts are in series with the coil. If the overload senses excess current in the load, the coil is

de-energized.

Electronic overload protection relays measure motor current and can estimate motor winding

temperature using a "thermal model" of the motor armature system that can be set to provide

more accurate motor protection. Some motor protection relays include temperature detector

inputs for direct measurement from a thermocouple or resistance thermometer sensor embedded

in the winding.

The purpose of protective relay and protective system is to operate the correct

CB‘s as to disconnect only the faulty equipment from the system as quickly as

possible. Thus minimizes the trouble caused by fault by they do occur. The

protective relay does not operate possibility of the fault on the system. Their active

starts only after the faults have occurred. It could be idea led if the protection could

anticipate and peasant faults because it is impossible to except where original case

of fault create some effects which can operate a protective relay. These are two

groups of protective relay.

1. Primary relaying equipments.

2. Back-up relaying equipments.

  Primary relaying is the first line of difference whereas back up protection

relaying works. Only when the primary relaying equipments fails and also back up

relays are slow in motion condition. Another job of back relay is to act as primary

relay in case of where this is out work.

Relay must operate when it is required. Since relay remains ideal. Most of the

time proper maintenance also plays important role in improving reliability. Relay

should select fault region and isolate that section from circuit. It should also

operate required speed. It should neither be slow which may not result in damage

to the equipment nor it should too fast which may result undesired operation during

transient faults and should be sensitive to faults. 

OPERATION:-

The protective relay serves for preventing tap changers and transformer from

being damage which is the part of delivering the protective relay as to be

connected in away that transformer immediately switched off captions oil

immersed transformer. Transformer break down are always precede by more or

less violent generation of gas. A broking joints produce local arc and vaporize in

the vicinity. As earth faults has the some results sudden short circuit rapidly

increased the temperature of the winding particularly the inner layer and packed oil

in vaporize. Discharge due to insulation weaken i.e. by the dehydration of the oil

produce local heating and generate gas. The generation of oil vapour or gas in

utilize to actuate a relay the relay is arranged between the transformer tank and the

separate oil conservator. The vessel is normally is full of oil. It contains two floats

if the gas bubbles are generated in transformer due to faults. They will be rise and

transfers the conservator and will trap in the upper part of the relay chamber.

Thereby displacing the oil and lowering the faults. This sinks and eventually closes

and external contacts which operates an alarm over other protection and flashover

at the bushing are not at adequately covered by other protective scheme also unless

it improves ground.

The differential scheme detects such faults and also on the leads between CTs

are power transformer provided ct’s are not mounted separately on transformer

bushing. In service internal faults operate when the relay is energizes. The

protective relay reenergized only by oil flow from the tap changer heat to the

conservator. The oil flow operates the flap value which is trapped into the “off”

position by timing mechanism. Thus the trapping switch is energized the CB’s are

operated the transformer off the line.

OIL TESTING LAB:

A)Oil Sampling:

Oil sampling is a procedure for collecting a volume of fluid from lubricated or hydraulic

machinery for the purpose of oil analysis. Much like collecting forensic evidence at a crime

scene, when collecting an oil sample, it is important to ensure that procedures are used to

minimize disturbance of the sample during and after the sampling process. Oil samples are

typically drawn into a small, clean bottle which is sealed and sent to a laboratory for analysis.

B)Oil analysis:

Oil analysis (OA) is the laboratory analysis of a lubricant’s properties, suspended contaminants,

and wears debris. OA is performed during routine preventive maintenance to provide meaningful

and accurate information on lubricant and machine condition. By tracking oil analysis sample

results over the life of a particular machine, trends can be established which can help eliminate

costly repairs. The study of wear in machinery is called tribology.Tribologistsoften perform or

interpret oil analysis data.

OA can be divided into three categories:

1. Analysis of oil properties including those of the base oil and its additives

2. Analysis of contaminants

3. Analysis of wear debris from machinery

EARTHING

Earthing is the provision of a surface under the sub station, which has a

uniform potential as nearly as zero or equal to Absolute Earth potential. The

provision of an earthing system for an electric system is necessary by the following

reason. 

1. In the event of over voltage on the system due to lighting discharge or other

system fault. These parts of equipment which are normally dead as for as voltage,

are concerned do not attain dangerously high potential.

2. In a three phase, circuit the neutral of the system is earthed in order to stabilize

the potential of circuit with respect to earth.

    

 

The resistance of earthing system is depending on shape and material of earth

electrode used.

    

 

The earthing is of two principal types  :-

Neutral Earthing

Equipment Body Earthing

        Neutral Earthing :-

Neutral Earthing also known as System Neutral Earthing (or Grounding)

means connecting the neutral point i.e. the star point of generator,transformer etc.

to earth. In rotating machines, generator, transformer circuit etc., the neutral point

is always connected to earth either directly or through a reactance. The neutral

point is usually available at every voltage level from generator or transformer

neutral. If neutral point is not available, then the most common method used is

using a Zigzag transformer. Such a transformer has no secondary. Each phase of

primary has two equal parts. There are 3 limbs and each limb has two winding,

providing flux density under normal condition. Since the fluxes are opposite, the

transformer takes very small magnetizing current under normal conditions. During

fault, the circuit is primary side,

which provides very less impedance to the current. The grounding

transformers are short time rating. Their size is almost one tenth as compared to

power transformer. 

Electrical Earthing:-

Electrical Earthing is different from neutral earthing. During fault condition,

the metallic parts of an electrical installation which do not carry current under

normal conditions, may attain high potential with respect to ground. As human

body can tolerate only I=0.165A/T current for a given time t so to ensure safety we

connect such metallic parts to earth by means of Earthing system ,which comprises

of electrical conductor to send fault current to earth. The conductor used is

generally in the form of rods, plates, pipes etc. 

Earthing system ensures safety in following ways :-

1. The potential of earthen body does not reach dangerously high value about earth,

since it is connected to earth.

2. Earth fault current flows through earthing and readily causes the operation of

fuse or an earth relay.

Merits of neutral Earthing:-

1. Arcing grounding is reduced.

2. Voltage of heating with respect to earth remains at harmless value they don't

increase to root 3 times of normal value. 

3. Suitable neutral point.

4. The earth fault relaying is relatively simple useful amount of earth fault current

is available to operate earth fault relay.

5. The over voltage due to lightening are discharged to earth. 

6. Improved service reliability due to limitation of arcing ground and improved of

unnecessary fringing of CB.

At GSS the neutral point of power transformer is connected solidly to earth

generally the earth connection are provided which leads reliability.

Power Line Carrier Communication :-

Power Line Carrier Communication (PLCC) provides for signal transmission

down transmission line conductors or insulated ground wires. Protection signaling,

speech and data transmission for system operation and control, management

information systems etc. are the main needs which are met by PLCC. 

PLCC is the most economical and reliable method of communication because

of the higher mechanical strength and insulation level of high voltage power line

which contribute to the increased reliability of communication and lower

attenuation over the larger distances involves.   

High frequency signals in the range of 50 KHZ to 400 KHZ commonly known

as the carrier signal and to result it with the protected section of line suitable

coupling apparatus and line traps are employed at both ends of the protected

section. Here in Sanganer and also in other sub-station this system is used. The

main application of power line carrier has been from the purpose of supervisory

control telephone communication, telemetering and relaying.  

PLCC Equipment

The essential units of power line carrier equipment consists of :-

a. Wave trap

b. Coupling Capacitor

c. LMU and protective equipments.

MERITS AND DEMRITS OF PLCC 

Merits  

The severity that a power line can withstand is much more than that odd

communication line due to higher mechanical strength of transmission line power

lines generally provide the shortest route between the Power Station and the

Receiving Stations. 

The carrier signals suffer less attenuation, owing to large cross sectional area of

power line

Larger spacing between conductors reduces the capacitances which results in lesser

attenuation of higher frequencies.

Large spacing also reduces the cross talk to a certain extent.

The construction of a separate communication line is avoided. 

Demerits 

Utmost care is required to safeguard the carrier equipment and persons using them

against high voltage and currents on the line. 

Noise introduced by power line is far more than in the case of communication line.

This is due to the discharge across insulators and corona etc. 

Induced voltage surges in the power line may affect the connected carrier

equipment.   

     

    

CONTROL ROOM

INTRODUCTION:- In Heerapura G.S.S. not only remote control carry the appropriate mean by which circuit breaker may be open or close but also indicating device , indicating lamps , isolating switches, protective relays , secondary circuit and wires are located here and most important “no load tap changer” for transformer is available. There is panel for synchronizing. Different panel are located at different stages and on each control panel switch is provided on the board. Colors of signals are synchronized as follows:

• Red – For circuit breaker or isolator switch is in closed position.

• Green - For circuit breaker is in open condition.

• Amber – Indicates abnormal condition.

There are different relays are located.

CONCLUSION

The training at grid substation was very helpful. It has improved my

theoretical concepts of electrical power transmission and distribution. Protection

of various apparatus was a great thing. Maintenance of transformer, circuit

breaker, isolator, insulator, bus bar etc was observable.

I had a chance to see the remote control of the equipments from control

room itself, which was very interesting.

So the training was more than hope to me and helped me to understand

about power system more.