Transformer is one of the most important part of the power system.This presentation provides information about transformer protection.

1. Sharad Institute of Technology College of
Engineering, Yadrav (Ichalkarnji)
A
Presentation On
transformer protection
Presented By,
Mr. Chetan Patil.
Assistant Professor
Department of Electrical Engineering

2. 
 Problems Arising In differential Protection Applied To Transformer.
 Harmonic Restraint And Harmonic Blocking.
 Restricted Earth Fault Protection
 Buchholz Relay
Contents

3. 
 Difference in lengths of pilot wires on either sides of relays.
 Difference in C.T. ratios due to error difference at high values of short
circuit current.
 Magnetizing inrush current.
 Tap changing.
 Saturation of magnetic core.
Problems Arising In differential
Protection Applied To Transformer

4. Harmonic Restraint And Harmonic Blocking
 When transformer is connected
to supply it will take large
current 16 to 10 times full load, to
avoid this difficulty harmonic
restraint relay is used.
This type of relay sensitive to
fault current only it does not
operate due to magnetizing
current.

5. Restricted Earth Fault Protection
 The restricted earth fault
relay does not operate for
earth fault beyond the
protected zone of
transformer.
 Such type of protection
system is not sensitive.
 Such type of system operate
for earth fault current of
about 15% of rated winding
current.

6. Buchholz Relay
 In this type of relay there are
two main circuits are used
 Alarm circuit
 Trip circuit
 The upper element is closes the
alarm circuit during incipient
fault.
 The lower element is used to
trip the CB for the internal
fault.

7. 
 It is simplest form of transformer protection.
 It is used protection against incipient fault.
Advantages

8. 
 It can be only used for the oil immersed transformer.
 It detect only the fault below oil level in the transformer.
 It is only used above 500KVA or 750KVA for the economic
consideration.
Disadvantages

9. 
 There are many problems in transformer such as magnetizing inrush
current, tap changing, saturation of magnetic core , difference in C.T.
ratios etc.
 The protective equipment's such as CB, relays are gives the protection
to the transformer from earth fault, harmonic blocking, incipient fault
and maintain the reliability of transformer.
Conclusion

10. 
Thank You

11. 
 Power system protection & Switchgear: B.Ram &
B.N. Vishwakarma.
 Switchgear & Protection: Sunil S.Rao, Khanna
Publications.
References