This document contains lists and contents pages for a report on power transformer protection. It includes a list of 15 figures related to transformer components and protection devices. It also includes lists of 3 tables on maintenance schedules and relay settings. The contents section outlines chapters on transformer construction, maintenance, losses, and various protection methods. Protection methods to be discussed include Buchholz relays, differential relays, overcurrent protection, and microcontroller-based protection.

1. (AIET/DOEE/2017-2018/SM/i)
LIST OF FIGURE
FigureNo. Figure Description Page No.
1.1. Law of Induction in Power Transformer 1
1.2. Power Transformer 3
2.1. Laminated Steel Transformer Core 5
2.2. High voltage winding and low voltage winding 6
2.3. Conservator Tank 7
2.4. Silica Gel Breather 8
2.5. Bushings of power transformer 9
2.6. Tapings in transformer 10
5.1. Hysteresis loop 17
6.1. Diagram of buchholz relay 24
6.2. Overview of buchholz relay 24
6.3. Constructional diagram of buchholz relay 25
6.4. Buchholz relay and conservator of 10 MVA, 132/3.3
KV
26
6.5. Diagram of flux producing in power transformer 28
6.6. Restricted earth fault protection 29

2. (AIET/DOEE/2017-2018/SM/ii)
6.7. Backup o/l & e/l relays 30
6.8. Differential relays 31
6.9. percentage differential relays 32
6.10. The operating characteristic of percentage bias
differential relay
33
6.11. Protection against lightning 37
6.12. Circuit diagram of overcurrent protection 38
6.13. Protection against fire 40
6.14. Diagram of GSM modem for protection of power
transformer
42
6.15. Block diagram of microcontroller for protection of
power transformer 44

3. (AIET/DOEE/2017-2018/SM/iii)
LIST OF TABLES
Table No. Table Description Page No.
3.1. Recommended maintenance schedule for transformer 11-13
3.2. Limits of Insulation Resistance of Windings of Power
Transformer
13
4.1. Power transformer maintenance schedule 14-15
5.1. Permissible core losses in transformer 18
5.2. Permissible copper losses at 75 degree Centigrade 20
6.1. Norms of transformer protection 22-23
6.2. Backup o/l & e/l relay 31
6.3. 10 MVA Power Transformer Relay settings 35
6.4. Magnetising inrush current 36

4. (AIET/DOEE/2017-2018/SM/iv)
LIST OF ABBREVIATIONS
Unit Abbreviations
A Ampere
AC Alternating Current
DC Direct Current
ACSR Aluminium Conductor Steel Reinforced
C.B. Circuit Breaker
C.T Current Transformer
CVT Capacitive Voltage Transformer
E.g. Example
Hz Hertz
KHz Kilo Hertz
KA Kilo Ampere
KV Kilo Volt
KVA Kilo Volt Ampere
MVA Mega Volt Ampere
Max. Maximum
Min. Minimum
MVA Mega Volt Ampere
Pf Pico Farad
P.F. Power Factor
LV Low Voltage
HV High Voltage
LCD Liquid Crystal Display
ADC Analog to Digital Converter
SMS Short Message Service
GSM Global System for Mobile Communication

5. (AIET/DOEE/2017-2018/SM/v)
CONTENTS
S. No. Title Page No.
CERTIFICATE……………………………………………………
ACKNOWLEDGEMENT………………………………………...
ABSTRACT………………………………………………………..
LIST OF FIGURE…………………………………………………
i-ii
LIST OF TABLES………………………………………………… iii
LIST OF ABBREVIATIONS…………………………………….. iv
CONTENTS………………………………………………………..
v-vii
1. CHAPTER-1
Introduction of Power Transformer………………………………....
1
1.1 Why protection required? ............................................................
2
1.2 Types of transformer……………………………………………
2
1.3 Use of power transformer……………………………………….
4
1.4 Protection of transformer………………………………………..
4
1.5 Possible transformer faults……………………………………...
4
1.5(a) Internal fault……………………………………………...
4
1.5(b) External fault…………………………………………….. 4
2. CHAPTER-2
Construction features of transformers……………………………… 5
2.1 Core……………………………………………………………..
5
2.2 HV & LV windings……………………………………………..
5

6. (AIET/DOEE/2017-2018/SM/vi)
2.3 Conservator……………………………………………………...
6
2.4 Vent pipe & diaphragm…………………………………………
7
2.5 Breather…………………………………………………………
7
2.6 Bushings………………………………………………………...
8
2.7 Tap changer……………………………………………………..
9
2.8 Cooling………………………………………………………….
10
3. CHAPTER-3
Recommended maintenance schedule for transformer……………...
11
3.1 Permissible values of earth resistance at……………………….. 13
3.2 Limits of insulation resistance of windings of power
transformers………………………………………………………… 13
4. CHAPTER-4
Power transformer maintenance schedule………………………….. 14
4.1 The following maintenance schedule is followed in power
stations and switching stations in the a.p power system…………… 14
5. CHAPTER-5
Losses in transformer……………………………………………….
16
5.1 Core loss………………………………………………………...
16
5.1(a) Hysteresis loss…………………………………………...
16
5.1(b) Eddy current loss………………………………………..
18
5.2 Copper loss……………………………………………………...
19
5.3 Stray loss…………………………………………………..........
20
6. CHAPTER-6
Transformer protection……………………………………………... 21

7. (AIET/DOEE/2017-2018/SM/vii)
6.1 Type of faults……………………………………………………
21
6.1(a) Through faults…………………………………………...
21
6.1(b) Internal faults……………………………………………
21
6.2 Transformer protection-different types of relays……………….
23
6.2(a) Buchholz relay…………………………………………..
24
6.2(b) Over fluxing protection………………………………….
28
6.2(c) Restricted earth fault protection…………………………
29
6.2(d) Backup o/l & e/l relays………………………………….
30
6.2(e) Differential relays……………………………………….
31
6.2(f) Protection against lightning……………………………...
36
6.2(g) Over current protection…………………………………. 37
6.2(h) Over loads protection……………………………………
38
6.2(i) Protection against overheating…………………………...
39
6.2(j) Protection against incipient faults………………………..
39
6.2(k) Protection against fire…………………………………...
39
6.2(l) Protection against overvoltage…………………………...
41
6.2(l.1) Cause of overvoltage protection………………...
41
6.2(l.2) Overvoltage protection device…………………..
41
6.2 (m) Protection of transformer using GSM modem…………
42
6.2(n) protection of transformer using microcontroller based 43
CONCLUSION………………………………………………..
45
REFRENCE…………………………………………………...
46