FIELD OF THE INVENTION
The present invention relates to an improved device to consistently maintain dry
air/nitrogen at higher pressure inside a transformer tank during long-distance
movement of the transformer tank.
BACKGROUND OF THE INVENTION
A power transformer is a voltage transforming electrical machine, and having a
magnetic circuit known as Core and two different coils one each for incoming ad
outgoing of the power. The core and the coils are separated from each other by
providing insulating materials in between them. The core-coil assembly is kept
inside the transformer tank.
The transformer is manufactured and tested in the factory after which the
accessories are dismantled and sent, with the transformer tank (which is the
largest and heaviest package of the total consignment) along with the en-cased
core-coil assembly being dispatched separately.
The technical requirement warrants that the core-coil assembly should not be
exposed to atmosphere during shipment to avoid absorption of moisture content
of the ambient air by the insulated items inside the transformer. For this
purpose, the transformer is required to be sent in oil filled condition . Because of
oil filling, the weight of the tank increases, and the resultant over-weight cargo
imposes restrictions in surface transportation.
Further, the oil inside the tank keeps on moving/oscillating during transportation
causing an imbalance in the Centre of Gravity of the cargo (oil filled tank with
core coil assembly inside). This un-stable condition of the cargo can cause
toppling (falling) of the transformer from the carrier resulting in complete
damage of the transformer.
To overcome the above problems, the tank (with core-coil assembly inside) is
filled with nitrogen gas or Dry air in the factory and sent to site for installation.
Oil is sent separately in tankers or drums, which is filled into the transformers
tank at site of installation.
During transport of the transformer tank from factory to site, the Nitrogen gas
(or Dry air) is kept at a pressure of 0.15 kg/sq. cm above the atmospheric
pressure. To maintain the higher gas pressure inside the tank, a set of spare gas
cylinders are provided along with the tank. These spare cylinders are connected
through a valve and a metallic pipe, in*such manner that, whenever the gas
pressure inside the tank reduces, the gas from the cylinder goes into the tank to
maintain the required pressure.
Sometimes during transit, this metallic pipe is damaged/removed/lost
accidentally. As a result, an opening appears on the tank wall and the gas from
the transformer tank leaks out. As a result, outside air including moisture goes
into the tank and the core-oil assembly is exposed to outside air. In this way, the
technical requirement of the transformers gets violated and the insulating
material inside the transformer has to be again dried at site to achieve the
desired result. This causes additional cost and delay at site of installation.
OBJECTS OF THE INVENTION
It is therefore, an object of the invention to propose an improved device to
consistently maintain dry air/nitrogen gas at higher pressure inside a
transformer tank during long distance movement of the transformer tank, which
eliminates the prior disadvantages.
Another object of the invention is to propose an improved device to consistently
maintain dry air/nitrogen gas at higher pressure inside a transformer tank during
long distance movement of the transformer tank, which eliminates the problem
of moisture-absorption by the core-coil assembly during transportation of the
transformer by surface transport.
A further object of the invention is to propose an improved device to consistently
maintain dry air/nitrogen gas at higher pressure inside a transformer tank during
long-distance movement of the transformer tank which is safe and economic.
SUMMARY OF THE INVENTION
According to this invention, there is provided an improved device to consistently
maintain dry air/nitrogen gas at higher pressure inside a transformer tank during
long-distance movement of the transformer tank, comprising at least one dry
air/nitrogen gas cylinder having a valve means to supply regulated gas/ dry air
upon activation; a connecting pipe adjoining the dry air/ nitrogen gas cylinder
to a transformer tank with core-coil assembly. The transformer tank is filled
with nitrogen gas/dry air maintained at a pressure higher than that of the
ambient pressure, the at least one cylinder upon activation supplying nitrogen
gas/dry air to said transformer tank to maintain the higher pressure. The
improvement is characterized in that a non-return valve is interposed between
the cylinder and the tank to permit one-way gas flow to the tank and prevent
egress of the available gas from inside the tank when the connecting pipe is
disabled to supply additional nitrogen gas to the tank.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 - shows a prior art device for maintaining pressure of nitrogen gas
/dry air inside a transformer tank according to the prior art.
Figure 2 - shows an improved device to consistently maintain nitrogen gas
/dry air at higher pressure inside a transformer tank according to the invention.
DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE
TO THE ACCOMPANYING DRAWINGS
A transformer is manufactured and tested in the factory and the accessories are
dismantled from shifting to erection site. The transformer tank (which is the
largest and heaviest package of the total transformer) including the en-cased
core-coil assembly is dispatched separately in gas (of Dry Nitrogen or Dry air)
filled condition. The pressure of the gas inside the tank is always at a higher
pressure than the outside air pressure. As shown in Figure 1, in order to
maintain the gas pressure inside the tank (1) during the shipment of the tank
(1), a set of spare gas cylinders (2) are provided in the tank (1)- These spare
cylinders (2) are connected to the tank (1) through a valve (3) and a metallic
pipe (4).
During the shipment, this connecting metallic pipe (4) might get damaged. As a
result, the gas which is at a higher pressure inside the tank (1) leaks out and the
outside air including moisture enters into the tank (1). Such a phenomenon
causes the core-coil assembly of the transformer exposed to outside air. In this
way, the insulation material inside the transformer absorbs moisture (water
particle) and become unsuitable for operation of the transformer.
To prevent the damages under such accidental circumstances, the present
invention provides an improved device to consistently maintain dry air at. higher
pressure inside a transformer tank during long-distance movement of the
transformer tank as illustrated in figure 2. According to the invention, a non-
return Valve (5) is proposed to be placed between the tank (1) and the metallic
pipe (4). The Non-return valve (5) permits the flow of gas in one way, i.e. from
the gas cylinder (2) through the metallic pipe (4) into the tank (1). The valve (5)
does not permit the gas to flow out from the tank.
Even under the circumstances, where the pipe (4) is damaged or dislodged
during transit, the gas already present in the tank (1) wilt not flow out and the
outside air cannot go inside the tank (1). Thus, the core-coil assembly will not be
exposed to the moisture of the outside air/water and the technicality of the
shipment is maintained.
WE CLAIM:
1. An improved device to consistently maintain dry air at higher pressure
inside a transformer tank during long-distance movement of the.
transformer tank, comprising:
- at least one air/nitrogen gas cylinder (2) having a valve means (3) to
supply regulated gas/air upon activation;
- a connecting pipe (4) adjoining the air/gas cylinder (2) to the transformer
tank (1) with core-coil assembly, the transformer tank (1) is filled with
nitrogen gas/air maintained at a pressure higher than that of the ambient
pressure, the at least one cylinder (2) upon activation supplying gas/air to
said transformer tank (1) to maintain the higher pressure, the
improvement is characterized in that a non-return valve (5) is interposed
between the cylinder (2) and the tank (1) so as to permit one-way gas
flow to the tank (1) and prevent egress of the available gas from inside
the tank (1) when the connecting pipe (4) is disabled to supply additional
gas to the tank (1).
2. An improved device to consistently maintain dry air at higher pressure
inside a transformer tank during long-distance movement of the
transformer tank substantially as herein described and illustrated with
reference to the accompanying drawings.

ABSTRACT

This invention relates to an improved device to consistently maintain dry air
at higher pressure inside a transformer tank during log-distance of the
transformer tank comprising at least one air/nitrogen gas cylinder (2) having
a valve means (3) to supply regulated gas/air upon activation; a connecting
pipe (4) adjoining the air/gas cylinder (2) to a transformer tank (1) with corecoil
assembly, the transformer tank (1) is filled with gas/air maintained at a
pressure higher than that of the ambient pressure, the at least one cylinder
(2) upon activation supplying gas/air to said transformer tank (1) to maintain
the higher pressure, the improvement is characterized in that a non-return
valve (5) is interposed between the cylinder (2) and the tank (1) so as to
permit one-way gas flow to the tank (1) and prevent egress of the available
gas from inside the tank (1) when the connecting pipe (4) is disabled to
supply additional gas to the tank (1).