Power Transformer Protection Devices - Miracle Electronics

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Power Transformer Protection Devices -
Miracle Electronics
Transformers rarely go down, but when they do,
they highly affect the entire working
environment with devastating effects. In case of
a transformer failure, there is great loss of
operational capability with the entire process
being interrupted and the assembly line coming
to a stop. Additionally, there could be
subsequent fires, security lapses and great loss
of income. Therefore, it is very essential to
take care of transformer protection.
There are two different categories of protection
devices that come with a power transformer one
that measure the electrical quantities affecting
the transformer, and second being those that
indicate the status of physical quantities of the
transformer. These include four protection
devices namely Buchholz Relay, Pressure Relay,
oil level monitor device, and winding
thermometer. Let us learn about these devices in
detail. Buchholz Relay The Buchholz Relay is a
fast and sensitive mechanical fault detector that
measures the electrical faults in oil-immersed
transformers. It is placed in the piping between
the transformers main tank and oil conservator,
irrespective of the number of transformer
windings, instrument transformers, and tap
changer position. The Buchholz Relay comprises of
a pivoted float and pivoted vane, both carrying
an individual mercury switch. Usually, the casing
is filled with oil and the mercury switches are
open.
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Pressure Relay The Pressure Relay in on-tank-type
tap changer power transformers detects any sudden
pressure increase rate inside the tap changer
oil compartment when the pressure in front of
the piston surpasses the contradictory force of
the spring, the piston will move, thus operating
the switching contacts, inside which the micro
switch is sealed and pressurized with Nitrogen
gas. Oil level monitor device As the name
suggests, oil level monitors are utilized to
measure the level of oil within the transformer.
These monitors have two contacts one for
maximum oil level alarm and the other for
minimum oil level alarm. A thermometer placed at
the top of the transformer has a liquid
thermometer bulb in a pocket that measures the
temperature of oil. This thermometer may have up
to four contacts two used for starting fans or
pumps for cooling, third for initiating the
alarm, and fourth to trip load breakers or
de-energize the transformer. Therefore, the top
oil thermometer can monitor the oil temperature
to ensure that it does not reach the flash
temperature level. Winding Thermometer The
winding thermometer creates an image of the
hottest part of the winding, and responds to
both the top-oil temperature and the heating
effect of the load current. Once the top oil
temperature is measured (as mentioned above), the
measurement is expanded with a current signal
proportional to the loading current in the
winding. This current is lead to a resistor
element in the main unit, which heats up and
results in an increased indicator movement. The
winding thermometer can also have up to four
contacts that perform the functions same as the
four contacts of the top-oil thermometer. Thus,
if a power transformer is fitted with both top-
oil and winding thermometers, it is the winding
thermometer that takes care of the forced
cooling control. To get the best-in-class power
transformers, or any kind of transformers for
that matter, you must approach Miracle
Electronics, the leading transformer manufacturer
in India, who has been providing transformers to
a number of satisfied customers since more than
20 years. For more information visit Miracle
Electronics