Buchholz Relay Construction Working And Transformer Protection

August 11, 2016April 17, 2020 admin

In this article we will learn about Buchholz Relay construction working and transformer protection. What we can prepare steps for transformer protection. We will discuss about the electrical device which is useful in transformer protection.

Buchholz Relay Construction Working and Transformer Protection

Now we are going to learn about the buchholz Relay construction working and transformer protection .

Buchholz Relay Construction Working and Transformer Protection

This is type of thermal relay which is installed between the transformer and conservator.It is used to give warning in case of less severe internal fault in oil immersed transformer and to disconnect the transformer from mains in case of severe internal fault. It provide protection against transformer internal fault and does not respond to external bushing or cable connection fault.

Construction of Buchholz relay

It consist of two element mounted is a small chamber located in the pipe connection between conservator and transformer tank. When minor fault occur heat is produced due to current leakage ,some of the oil evaporates and vapour collect in top of the chamber while passing to the conservator. When a predetermined amount of vapour accumulate in the top of chamber the oil level falls, the mercury switch attached to float is tilted so close the alarm cuircuit and sing the bell.

A release cock is also provided at the top of chamber so that after operation the pressure in the chamber can be released and gas emitted to allow the chamber to refill with oil. In case of severe fault large volum of gas is evolved so that the lower element containing a mercury switch mounted on a ringed type flape is tilted and the trip coil is energized. A test cock is also provided at the bottom of chamber to allow air to be pumped into the chamber.

Advantage of Buchhloz Relay

This relay has following advantages

It is simplest form of protection

It detect the incident fault at a stage much earlier that is possible with other form of protection.

Buchholz Relay Working Construction and Transformer protection

Fault in the transformer is of following when drawn on a graph.

Fault in Auxiliary Equipment’s

The following can be considered as auxiliary equipment’s of the transformer.

1. Transformer

2. Gas cushion

3. Oil pumps and forced air fans

4. Core and winding insulation

Winding fault In Transformer

There may be faults between adjacent turns or parts of coils such as phase to phase faults another fault may be fault to ground or across complete winding such as phase to earth faults on the HV and LV external terminals.

Over-loads and external short circuits In Transformer

Over-loads may be sustained for long periods, being limited only by the permitted temperature rise in the winding and the cooling medium. Excessive overloading will result in deterioration of insulation and subsequent failure.

Differential protection of transformer

transformer protection, protection of transformer, transformer fault

Differential transformer protection is the most important type of protection used for internal phase to phase and phase to earth faults and generally applied to transformer having rating of 5MVA and above. The differential protection of transformer is also known as merz-price protection for the transformer. A schematic diagram of differential transformer protection scheme for a star- delta power transformer shown in below fig.

In a star delta transformer, the load currents in the two winding are not in direct phase opposition but are displaced by 30 degree and to allow for this the CT secondary are connected in delta on the star side and in star on delta side.

Buchholz Relay Working In Transformer

The heat produced by internal fault or overloading of transformer oil to decompose and produce a gas which can be made to detect the winding fault. Buchholz relay is an electrical device which use to transformer protection form heating of winding.

Buchholz relay is a simplest form which is used in all transformers produced with conservator. So These are buchholz relay construction working and transformer protection.

Bus-Bar Arrangements In Transformer

Bus-bar are arranged to achieve

1. Adequate operating flexibility

2. Sufficient reliability

3. Minimum Cost

The cost can be minimized by reduced the number of circuit breakers to a minimum but complication of the protective gear are increased.

Some bus bar Arrangement In Transformer

It is also main step in transformer protection.In this arrangement a set of bus-bars is used for complete power station and to this bus bar are are connected all generators. Transformers and feeders through circuit breakers and isolating switches. Such a bus-bar arrangement is cheaper in initial as well as in maintenance cost and simple in operation and relaying.

Single Bus-bar system with sectionalisation

With increased number of generators and outgoing feeders connected to the bus-bars, it becomes essential to provide arrangement for sectionalizing the bus bars so that a fault on any one section of the bus-bars may not cause a complete shutdown. This is achieved by providing a circuit breaker and isolating switches between the sections. This is main step of transformer protection because bus bar proper arrangement is more important than other. These are also describe the above title which is buchholz relay construction working and transformer protection.

Ring bus-bar system

In this arrangement each feeder is supplied from two paths, so that in case of failure of a section, supply is not interrupted.

Double main and transfer bus bar Arrangement

Double main and transfer bus bar arrangement is also important for transformer protection. This arrangement incorporates all advantages of the double bus as well as transfer bus-scheme. The scheme needs a bus-coupler for the on load transfer to circuits from one main bus to the other and a transfer coupler for taking out circuit breaker of various circuits for maintenance. Double main and transfer bus bar arrangement is also important for transformer protection.

Hence these are Buchholz Relay construction working and transformer protection. From above article we have also studied about advantage of buchholz relay and different kind arragement of bus bar like Double main and transfer bus bar arrangement, Single busbar arrangement. We have also known about winding fault in transformer . If you will find any incorrect in above article please comment below in comment box.