BALASORE COLLEGE OF ENGINEERING AND TECHNOLOGY

GUIDED BY:-Mr. Mithun Kar Mr. Sashibhusan

Behera

presented BY:-MALAY RANJAN PRADHANELECTRICAL ENGG7TH SEMESTERREGD NO:-1421225080ROLL NO:-13EE/56L

SAMINAR TOPICS :- Buchholz relays

Contents:•Introduction •Basic construction

•TYPES OF FAULTS

•Operation

• Advantages & disadvantages

•Conclusion

This relay was first developed by Max Buchholz in 1921. Buchholz relays have been applied to large power transformers

Buchholz relay is a gas-actuated relay installed in oil- immersed transformers for protection against all such kind of faults.

It is used to gives an alarm in case of slow developing faults in the transformer and to disconnect the transformer from the supply in the event of severe internal faults.

This relay is used in oil-immersed transformers of rating above 750kVA.

introduction

BUCHHOLZ RELAY IS USED IN BETWEEN CONSERVATOR AND MAIN TANK OF TRANSFORMER

SCHEMATIC DIAGRAM

Basic CONSTRUCTION The device has two elements

The upper element consists of a mercury type switch attached to a float.

The lower element contains a mercury switch mounted on a hinged type flap located on the direct path of flow of oil from the transformer to the conservator which is in contact with the other float.

The upper element closes an alarm circuit during slow developing faults whereas the lower element is arranged to trip the circuit breaker in case of severe internal faults.

TYPE OF FAULTS

1.INCIPIENT FAULTS or SLOW DEVELOPING FAULT

2.EARTH FAULT 3.WINDING SHORT CIRCUIT 4.PUNCTURE OF BUSHINGS 5.SHORTCIRCUIT BETWEEN PHASES

In case of slow developing faults within the transformer, the heat due to the fault causes decomposition of some transformer oil in the main tank.

The products of decomposition mainly contain 70 % of hydrogen gas. The hydrogen gas being light tries to go into the conservator and in the process gets trapped in the upper part of the relay chamber.

When a predetermined amount of gas gets accumulated, it exerts sufficient pressure on the float to cause it to tilt and close the contacts of mercury switch attached to it. This completes the alarm circuit to sound an alarm.

If serious fault occur in the transformer, an enormous amount of gas is generated in the main tank.

operation

The gas in the main tank rushes towards the conservator via of the buchholz relay and in doing so it tilts the flap to close the contacts of mercury switch.

This completes the trip circuit to open the circuit breaker controlling the transformer.

ADVANTAGES:

It is the simplest form of transformer protection .

It detects the slow developing faults at a stage much earlier than other forms of protection.

DISADVANTAGES:

It can only be used with oil immersed transformers equipped with conservators

The device can detect only faults below oil leveling the transformer.

Therefore separate protection is needed for connecting cables.

conclusion:As Without antivirus PC is affected by virus which may affect system performance & can also damage the system, just like that…

Without buchholz relay the transformer operate with oil cannot be exit.As fault will create a severe damage to transformer.

Transformer is the worldwide acceptable electrical device as it is considered as heart of electricity hence it’s protection is necessary.

That is the reason we can understand that buchholz relay is how much important for transformer protection.

REFERENCES Technical manual – Power Transformer

maintenance and acceptance testing, 1998. Lance R. Lewand, Condition Assessment of

Transformers – Analysis of oil Data and its Quality, NETA WORLD – The Official Publication of the International Electrical Testing Association, Winter 2005-2006.

Web side of www.you tube.com and electrical4u.com and 282online.com

THANK YOU