Ranjan Kumar presented on advance transformer protection technologies. The presentation covered: 1) An introduction to power transformers, their components and working principle. 2) Common power transformer failures like winding failures and faults caused by overloading. 3) Types of protection methods like Buchholz relay, differential protection, oil level monitoring and overflux protection. 4) New protection technologies using devices like silica gel, pressure relays, GSM modems and microcontroller-based relays for remote monitoring of transformer parameters.

1. SEMINAR PRESENTATION
ON
SUBMITTED BY:-
RANJAN KUMAR
14EAIEE079
B.Tech. IV Yr. VIII SEM
ADVANCE TECHNOLOGY OF POWER
TRANSFORMER PROTECTION
SUBMITTED TO :-
Ms. NUMA M. THAPLIYAL &
Mr. DEEPAK SHARMA
(SEMINAR INCHARGE)

2. CONTENTS :-
1. Introduction of power transformer
2. Use of power transformer
3. Power transformer failures
4. Possible power transformer faults
5. Types of protection of transformer
6. Conclusion.
7. References
1

3. 1. INTRODUCTION OF POWER TRANSFORMER
 A power transformer is a static machine used for
transforming power from one circuit to another
without changing frequency.
 Since, there is no rotating or moving part, so a
transformer is a static device. A transformer works on
the principle of mutual induction.
 Hence, transformer operates on an ac supply.
 Power transformers, primary winding always
connected in star and secondary winding delta
connection. 2

4. DIAGRAM OF POWER TRANSFORMER:
3

5. 2. USE OF POWER TRANSFORMER:
For reduction of transmission losses.
For increasing the low voltage level to high
voltage level.
The voltage level of a power is increased,
the current of the power is reduced which causes
reduction in ohmic or I2R losses in the system.
Low level power must be stepped up for
efficient electrical power transmission. 4

6. 5
3. POWER TRANSFORMER FAILURES:
Winding failures due to short circuits.
Core faults due to core insulation failure and shorted
laminations.
Terminal failures due to open leads, loose connections and short
circuits.
On-load tap changer failures due to mechanical, electrical, short
circuit and overheating.
Abnormal operating conditions due to over fluxing, overloading
and overvoltage.
External faults due to Overloads , Overvoltage and Over fluxing.

7. 6
4. POSSIBLE TRANSFORMER FAULTS:
1. Winding Failure
2. Winding inter-turn
faults.
3. Core insulation failure,
shorted laminations.
4. Over fluxing.
1. Overloads .
2. Overvoltage .
3. Over heating .
4. External system
short circuits.
EXTERNAL FAULTInternal FAULT

8. 5. TYPES OF PROTECTION
1. BUCHHOLZ RELAY :
Definition: The Buchholz relay protects the transformer from
internal faults. It is the gas actuated relay. The Buchholz relay is
placed between the main tank and the conservator. Such type of
relay is used in the transformer having the rating higher than
500KVA. It is not used in small transformer because of economic
consideration.
7

9. BUCHHOLZ RELAY DIAGRAM:
8

10. WORKING PRINCIPLE OF BUCHHOLZ RELAY:
When the fault occurs inside the transformer, the temperature
of the oil increases. The oil evaporates in the form of the gas.
The generation of the gas depends on the magnitude of the fault
occurs inside the transformer. The internal failure occurs in the
transformer either because of the insulation breakdown between
the winding or the winding have the weak initial contact.
9

11. 10
2. DIFFERENTIAL PROTECTION SCHEME:
 This scheme is employed for the protection of
transformers against internal short circuits. It provides
the best overall protection for internal faults.
 It compares the current entering the transformer with
the current leaving the element.
 If they are equal there is no fault inside the zone of
protection.
 If they are not equal it means that a fault occurs
between the two ends.

12. DIFFERENTIAL RELAY OPERATION:
11

13. DIFFERENTIAL RELAY OPERATION:
12

14. 13
3. PROTECTION OF X-MER USING SILICA GEL :
Silica gel basically used for absorbed the
moisture content.
Silica gel protect from atmospheric moisture for
inserting inside the transformer because
transformer is not fully pack as like CT and PT.
Silica gel is basically in blue color and its
chemical name is cobalt chloride. When it is
rotten then its color becomes pink color.
Silica gel is connected with conservator tank by
means of breathing pipe.

15. 14
 DIAGRAM OF SILICA GEL:

16. 15
4. OIL LEVEL MONITOR DEVICE:
 Transformers with oil conservator (expansion tank)
often have an oil level monitor.
 Usually, the monitor has two contacts for alarm.
 One contact is for maximum oil level alarm and the
other contact is for minimum oil level alarm.
 When oil level is low from fixed minimum oil level then
minimum oil level alarm is ringing.
 When oil level is high from fixed maximum oil level then
maximum oil level alarm is ringing.

17.  OIL LEVEL MONITOR DEVICE DIAGRAM:
16

18. 17
5. PRESSURE RELAY:
 Many power transformers with an on-tank-type tap changer
have a pressure protection for the separate tap changer oil
compartment.
 This protection detects a sudden rate-of-increase of
pressure inside the tap changer oil enclosure.
 When the pressure in front of the piston exceeds the counter
force of the spring, the piston will move operating the switching
contacts.
 The micro switch inside the switching unit is hermetically sealed
and pressurized with nitrogen gas.

19.  DIAGRAM OF PRESSURE RELAY:
18

20. 19
6. PROTECTION AGAINST OVERFLUXING
Transformer over flux Protection is provided to protect the
Transformer core from over fluxing.
In case the flux in the core of Transformer exceeds a certain level,
the core loss increases which may lead to overheating of
components which in turn may result into internal fault.
Therefore, over flux protection is provided.
The magnetic flux increases when voltage increases. This results
in increased iron loss and magnetizing current. The core and core
bolts gets heated and the lamination insulation is affected.

21.  THE EXPRESSION FOR FLUX IN A TRANSFORMER IS GIVEN BY:
WHERE,
Φ = FLUX E = APPLIED VOLTAGE
F = FREQUENCY K= IS A CONSTANT.
Φ = K E/f
20

22. 7. PROTECTION OF X-MER USING GSM MODEM:
 It can be used to detect the fault in Power transformers.
Various parameters like Oil level, Temperature, voltage
and current are monitored.
 GSM-(global system for mobile communication)
performs digital cellular communication.
 It sends actual load value in digital information to
respective authority via SMS with the help of sim card.
 It’s frequency range is 900MHZ to 1990MHZ.
21

23.  DIAGRAM OF GSM MODEM FOR PROTECTION OF POWER X-MER:
22

24. 8. PROTECTION OF X-MER USING MICROCONTROLLER
BASED RELAY:
 The microcontroller is required to serve the purpose monitoring
the transformer information such as temperature, voltage and
current through the LCD display, personal GSM module and
triggering the relay when there is any fault.
 To design the current and voltage sensing circuits that
will be interfaced to the microcontroller for monitoring.
 To develop an algorithm and codes to the microcontroller which
will work for under over current, over voltage, under voltage
conditions and transmit the parameters to a personal computer.
 A microcontroller is a compact integrated circuit designed to
control operation of any system. 23

25.  BLOCK DIAGRAM OF MICHROCONTROLLER FOR
PROTECTION OF POWER X-MER:
24

26. 6. CONCLUSION
25
The protective equipment discussed is engineered to
limit the damage and system disturbance caused by
faults which can occur in a transformer.
The choice of protective equipment depends on the size
and the connection of a transformer, voltage level, power
system grounding and the protective relays of the power
network.
Protection of transformer is more necessary for
reducing the fault occurring in power transformer.
With the help of protection of fault life and efficiency of
power transformer is maintain.

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2003
2. Electrical technology volume 3rd and 4th by- B. LTheraja,1st edition
1959,reprint 2008
3. http://sites.ieee.org/fw-pes/files/2013/01/Linear integrated circuits J.S Katre,
4th edition 2002
4. Badri ram and D N Vishwakarma (1995) power system protection and switch
gear New delhi: Tata Mc Graw hill.
5. Mazouz A. Salahar Abdallah R. Al-zyoud (2010), ‘Modelling of transformer
differential protection using programmable logic controllers’ European
journal of scientific research, 41(3), pp. 452-459.
7. REFERENCES
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