Gyanmanjari Institute of Technology

Bhavnagar

Department of Electrical Engineering

Report on Industrial Visit

at

400kV Substation at Hadala & Allwyn Cable, Rajkot.

8th January 2018

Submitted By

1.Yash Patel (151290109041)

2. Harsh Vaidya (151290109060)

Faculty Coordinator:- Prof. C. P. Pandya

Head of Department:- Prof. A. H. Vora

Acknowledgement

We are indeed thankful to our respected Principal, Dr. H. M. Nimbark, H.O.D. Prof.

Anish Vora sir who have arranged an industrial visit at 400kV substation, At. Hadala & Allwin

Industries, Rajkot for students of 6th sem electrical engineering department. It was really fruitful

experience we had during our visit. We are also thankful to the engineers of GETCO and Mr.

Dhaval sir for their warm response.

Content

1. Purpose of Visit

2. General Information

3. Conclusion

Purpose of Visit

The main purpose of visit was to gain overall practical knowledge about the equipments

and their functions used in substation. There were many equipments students had seen for the

first time like ICT(Inter Connected Transformer),many Circuit Breakers like 1.5 Circuit Breaker,

SF6 Circuit Breaker etc,many protection devices such as OSR(Oil Surge Relay), PRV(Pressure

Release Valve), equipments for cable manufacturing process etc. Particularly in electrical

engineering we deal with two domains i.e. Field Domain and Circuit Domain. Practical

implementation of Circuit Domain can be done via Field Domain. Ultimately, our aim was

fulfilled.

General Information

On 8th January 2018 we had undergone visit at 400kV substation at Hadala-Rajkot and

Allwin industries. Hadala substation is interconnecting s/s of saurashtra region dealing with three

different voltage levels 66kv, 220kv & 400kv. Hadala s/s interconnecting transmission lines from

different locations like Mundra, wadinar, Limdi, Amreli, etc.

Allwin industries are manufacturer of various types of cables like Single core, Multi core,

Armored cable, Arial Bunch etc. Allwin industries are having well established laboratory for

testing of cables. They have demonstrated various testing on cable during our visit as well as

manufacturing and coating process of cable.

1. ICT-Interconnected Transformer

Afterwards, along with senior engineer of GETCO we had entered in substation. First of

all we had discussed about transformer as it is the heart of the substation. The transformer which

was used their was ICT(Inter Connected Transformer). The rating of ICT was 315MVA. It was

commercialized on 27-05-2007. The connection scheme was star-delta(LV-HV). There were

total 3 bus,

1. Main bus-1

2. Main bus-2

3. Transfer bus

The tapping which was use in ICT is 17 which is placed at secondary winding. The

transformer oil which was used in ICT was “Ester Oil”. The type of cooling used was

ONAN,ONAF etc. There were also many protecting devices used in ICT i.e. Buchholz Relay,

Breather(will turn blue to pink at the time of replace), LCM(Leakage Current Monitor), Surge

Monitor, MOG(Minimum Oil Gauge), PRV(Pressure Release Valve), OSR(Oil Surge

Relay),Differential Relay.

2. Buchholz Relay

It is a very sensitive gas and oil operated instrument which safely detect the formation of

gas or sudden pressure inside the oil transformer. It is a electrical and mechanical both type

operated device. Electrical type relay is very accurate as compare to mechanical type relay.

3. Conservator Tank

This is a cylindrical tank mounted on supporting structure on the roof of the transformer's

main tank. When transformer is loaded, the temperature of oil increases and consequently the

volume of oil in the transformer gets increased. Again, when ambient temperature is increased,

the volume of oil is also increased. The conservator tank of a transformer provides adequate

space for expansion of oil. Conservator tank of transformer also acts as a reservoir of oil.

4. Breather

When the temperature changes occur in transformer insulating oil, the oil expands or

contracts and there an exchange of air also occurs when transformer is fully loaded. When

transformer gets cooled, the oil level goes down and air gets absorbed within. This process is

called breathing and the apparatus that pass through the air is called breather. Actually, silica gel

breathers control the level of moisture, entering electrical equipment during the change in

volume of the cooling medium and airspace caused by temperature increasing. So it sucks the

moisture from the air which is taken by transformer so that dry air is taken by transformer.

5. Transformer Tests

1. Ten delta test

2. SFRA

3. SC OC test

6. Insulator Type

1. SRA

2. Porcelain

7. Transformer Oil Test

1. BDV(Breakdown Voltage)

2. PPM(Parts Per Million)

8. Capacity of Substation

3*315MVA=945MVA

9. Safety to Fire System

NIFT:-To drain the oil via pipe

To indicate when minimum oil is left in conservative tank MOG(Minimum Oil

Gauge) was used. For maintenance purpose transfer bus is used in which the power is

diverted to this bus.

10. Circuit Breaker

A circuit breaker essentially consists of fixed and moving contacts called electrodes.

Under normal operating condition, this contact remains close and will not open automatically

until and unless the system becomes faulty. When a short circuit occurs, a heavy current flows

through the contact of the circuit breaker. Hence current density increases which results in heat.

There is an arc quenching medium in the circuit breaker. The CB which was used in substation

was SF6. In this CB gas is used as the arc quenching medium. The SF6 (Sulphur Hexafluoride)

is an electro negative gas and has a strong tendency to absorb free electrons. This is the reason

that SF6 CB is used frequently in many substations. Names of other popular CB’s are given

below,

1. 1.5 CB

2. Arc Control Oil CB

3. Low Oil CB

4. VCB(Vacuum CB)

5. Air blast CB

6. SF6 CB

7. Plain break oil CB

8. Oil CB

11. Isolator

Isolator is used to isolate the faulty part from transmission line. The fault may be L-L-L,

L-L-L-G where fault currents in the three lines are equal in magnitude and displaced 120 degree

electrical from one another. There is no any arc quenching medium in isolator. Normally isolator

operates in no load condition. The isolator which was used in 400kV substation was “Pentogram

Isolator” and “Central break isolator”. The pentogram isolator is used in Traction. The other

popular isolators are,

1. Tendum type single break isolator

2. Tendum type double break isolator

12. CT & PT

Current transformer and potential transformer are used for protection and measurement of

current and voltage respectively. At the time of voltage measurement first of all voltage is

stepped down and then it is measured.

13. Wave Trapper

Wave trapper is used to pass the required frequency and to eliminate extra frequency

which may be harmful for transmission line. It is like low pass and high pass filter.

14. Earth Switch

It is used to discharge the high voltage at the time of fault occurrence on the transmission

line. When the fault occurs the path for fault recovery is,

1. Relay:- It will sense the fault occurred.

2. CB:- Circuit will break with help of circuit breaker.

3. Isolator:- It will isolate the faulty part from transmission line.

4. Earth Switch:- It will discharge the high voltage directly to earth.

15. Reactor Transformer

It is used to eliminate reactive voltage at the time of peak load.

16. Cable information

We had also seen the control room at substation. Afterwards sharp at 3:30 pm we had

finished our visit at 400kV substation Hadala. Then we had also visited at one small

industry named Allwin Industries which was dealing with cables. Some of the tests of

cables were also performed which is listed below,

17. Photographs

- Control room of Hadala s/s

- Discussion with Engineers of GETCO

- Campus, Hadala s/s 400kv

- Manufacturing Process @ Allwin industries

- Campus, Allwin industries Rajkot

Conclusion

Through this visit, students gained information and practical knowledge about various

manufacturing process for cables and power transmitting equipments. They got knowledge about

active and reactive power flow in power system as well as manufacturing of cable insulator.

During visit they have got an opportunity to see various world class heavy engineering

machineries and processes. This kind of visit is very much helpful to enhance practical

knowledge of the students.