Transformer protection

In this article we will learn about how to do transformer protection. What we can prepare steps for transformer protection. We will discuss about the electrical device which is useful in 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

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 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 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.

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.

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.

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.

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.

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 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 it is transformer protection if you will find any incorrect above please comment below in comment box.

For more about transformer protection you must watch this video.