Cand. tech. sci
Kostinskiy S.S., the master Vasileva C.V.
Federal
state budget educational institution of higher education
"Platov South-Russian State Polytechnic University (Novocherkassky
polytechnic institute), the
Russian Federation
Influences of temperature of the core of the
three-phase transformer on idling losses
The provisions. In article results of modeling of
influence of temperature of the core on losses of idling of the power
three-phase transformer are resulted. Modeling is executed for nominal phase
voltage 200, 210, 220, 230 and 240 V. On the basis of the received
experimental data the conclusion that the
temperature of magnetic system of the tested transformer influences value of
losses of idling is drawn. With growth of
temperature of magnetic system total losses of active power of idling on all
three phases of the tested transformer decrease on the average for 2 %.
Key
words: the three-phase transformer, losses of active
electric energy, magnetic system.
Electrical networks represent set of mains
transformers and transmission lines. Electric mains transformers are the most
responsible elements in the scheme of any electric substation. The general
number of the electric transformers established on substations of power
systems, the industrial and agroindustrial
enterprises, in city and rural electric systems, are estimated hundreds thousand. This results from the fact that the
electric power on a way from generators of power stations to electroreceivers - to electric power consumers, as a rule,
is repeatedly transformed [1].
Actual losses, that is difference between released in
a network and the paid electric power, it is integrated have four components
[2, 3]: technical losses of the electric power; an auxiliary power requirement
of substations and ice fusion; the losses of the electric power caused by tool
errors of her measurement (tool losses); commercial losses.
Losses in mains transformers develop of two
components: short circuit losses (losses in copper) and idling losses (losses
in a steel). In distributive electrical networks with upper voltage
6 – 10 kV a considerable component of technological losses of
the electric power are losses of idling of transformers [4].
The core temperature influences importance of losses
of the idling caused by vortical currents. Deviation
of losses of idling owing to temperature change can be considerable [5]. So at
temperature measurement at 21 °Ñ and at 50 °Ñ on the transformer 50 MVA,
110 / 10,5 kV decrease in losses with temperature growth has
been noted. At a nominal induction 1,77 Tl
decrease has made 1,2 %, and at an induction 1,6 Tl
– 3,3 % [6].
Now errors of definition of losses of idling of the
transformer are considerable, as they pay off by the simplified techniques. The
real estimation of these losses by results of tests and development of
necessary recommendations is necessary [4].
In materials [7] it is specified, that «at an establishment
of specifications of losses of the electric power in electrical networks the
technical condition of objects of an electronetwork
economy on the basis of inspections and accounts» can be considered. In
accounts of loss of idling of transformers are accepted, as a rule, equal to
passport importance, but during operation term real losses of idling change.
According to [8]: «It is supposed to define for mains
transformers (autotransformers) of loss of idling taking into account their
technical condition and service life by measurements of these losses by the
methods applied on manufacturers at an establishment of nameplate data of
transformers (autotransformers)».
In the instruction [8] it is underlined, that it is
expedient to include reports of measurements of losses of the idling, received
by measurements of these losses by the methods applied on manufacturers.
Selective measurements of losses of idling of working
transformers of networks spent(lead) in article [4] 6 – 10 kV
and comparison of the importances received in
observed data with the rated importances received at
recalculation of passport importances by a technique
[9, 10] which considers change of size of losses of idling while in service the
transformer, testify that real importances of losses of
idling for separate transformers can appear as above, and below rated importances.
In a kind specified above the question of
specification of influence on losses of idling of the mains transformer of
temperature of the core is actual.
According to item 1.2 [11] transformers test with the details established on
them and outside emergency devices which can influence results of tests of the
transformer. The photo of appearance of the stand for measurement of
losses of idling is shown in figure 1.
Fig 1. The photo of appearance of the stand for
measurement of losses of idling:
1 – the personal computer; 2, 3, 23 – a laboratory
autotransformer; 4, 7, 9, 12, 18, 20, 22 – the jack; 5 – the counter of
electric energy multipurpose PSCH-4TM.05MK.04; 6, 11 – the interface device
optical USO-2; 8, 19, 21 – the automatic switch; 10 – the counter of electric
energy multipurpose PSCH-4TM.05MK.00; 13 – interface AS4 converter; 14 – a
measuring instrument-regulator universal eight-channel TRM 138-R; 15 – the
transformer of power series TP TP3-380/220-2,5; 16 – a cable the feeding stand
in rated voltage 380 V; 17 – the block measuring; 24 – the analyzer of
quality of power MI 2792À
As object of research the three-phase transformer of
mark TP 3-380/220-2,5, by nominal capacity 2,5 kVA,
voltage on a winding of upper voltage 380 V, on a winding of the lowest
voltage 220 V, produced 30.09.2016 with factory number ¹ 1054 and
corresponding to Specifications 3413-006-47936447-2002 [12] has been
accepted.
According to item 1.3 [11] the
ambient temperature at tests should be from 10 to 40 °Ñ. The diagram
of change of an ambient temperature at tests is shown in figure 2.
Fig 2. The diagram of change of an
ambient temperature at tests:
1 – the data received from the gauge of temperature; 2
– the data received from the gauge of temperature, 4th order approximated by a polynom
Apparently in figure 2, during test the
minimum value of temperature of air has made
13,0 ºÑ, and maximum -
20,3 ºÑ, that corresponds
to item 1.3 requirement [11] . Average value of temperature
of air for all period of test has made 17,5 ºÑ
According to item 6.1.1 [11], at
experience of idling directed on measurement of losses of idling of the tested
transformer, brought voltage at tests of three-phase transformers should be
practically symmetric under item 6.1.2 [11]. According to item 6.1.2 [11] it is
necessary to consider system of linear voltage practically symmetric if each of
linear voltage differs no more than on 3 % from an average of arithmetic three
linear voltage of system. The diagram of change of value of an average of arithmetic three
linear voltage of system during test carrying
out is shown in figure 3.
Fig 3. The diagram of change of value of an average of arithmetic three
linear voltage of system during test carrying
out:
1 – the values calculated on the basis of
data about linear voltage of windings of the
higher voltage of the tested transformer, received from the counter
PSCH-4TM.05MK.00;
2 – the values calculated on the basis of data about linear voltage of windings of the higher voltage, 4-th
order approximated by a polynom
Average value of an average of arithmetic three linear
voltage of system for all period of test has
made 381,6 V.
The diagram of a deviation of
each of linear voltage concerning value of an average of arithmetic three
linear voltage of system is resulted in figure 4.
During test the minimum deviation of
value of linear voltage concerning value of an average of arithmetic three
linear voltage of system has made – 1,335 % for linear voltage between
phases L2 and L3, maximum – 1,189 % for linear voltage between
phases L1 and L2.
Considering the deviations of values of
linear voltage resulted above value concerning values of an average of
arithmetic three linear voltage of system during
test carrying out it is possible to draw a conclusion, that each of linear
voltage differs much less, than on 3 % from an average of arithmetic three
linear voltage of system. Accordingly, it is necessary to consider system of
linear voltage practically symmetric.
Fig 4. The diagram of a deviation of values of linear voltage concerning values
of an average of arithmetic three linear voltage of system during carrying out of the test, 4-th order
approximated by a polynom:
1 – linear voltage between
phases L1 and L2; 2 – linear voltage between phases L2
and L3; 3 – linear voltage between phases L3 and L1
According to item 6.1.1 [11] at experience
ÕÕ necessary for definition of losses ÕÕ of the tested transformer, brought
voltage should be nominal frequency with a maximum deviation in limits
± 1 %. The diagram of change of value of frequency of voltage brought to
the tested transformer during test carrying
out is shown in figure 5.
Apparently in figure 5, during test the minimum value of frequency of voltage
brought to the tested transformer made
49,97 Hz, and maximum – 50,03 Hz. Average value of frequency
of voltage brought to the tested transformer
for all period of test has made 50,002 Hz.
The deviation of value of frequency of
voltage brought to the tested transformer from rating value 50 Hz on the
average during test has made of 0,004 %, that on three order 1 %
there is less. Hence, item 6.1.1 [11]
requirement is carried out.
Fig 5. The diagram of change of value of frequency of voltage brought to
the tested transformer during test carrying
out:
1 – the values of frequency
measured by counter PSCH-4TM-05MK; 2 – the values of frequency
approximated by a polynom of 4-th order
The diagram of change of
values of losses of the active power measured at performance of experience of
idling on the tested transformer during
carrying out of test, is shown in figure 6.
Fig 6. The diagram of change of values of losses of the active power
measured at performance of experience of idling on the tested transformer during carrying out of test, 4-th order
approximated by a polynom:
1 – phases L1;
2 – phases L2; 3 – phases L3;
4 – total losses on all three
phases of the tested transformer
At definition of losses of idling of the
transformer, definition of influence of temperature of the core on change of
losses of idling was the primary goal of the spent tests. The diagram of change of values of total losses of active power on
all three phases of the tested transformer,
measured at performance of experience of idling, from average temperature of magnetic system is shown in figure 7.
Fig 7. The diagram of change of values of total losses of active power on
all three phases of the tested transformer,
measured at performance of experience of idling, from average temperature of the magnetic system, 1-st order
approximated by a polynom
During test the minimum value of total
losses of active power on all three phases of
the tested transformer, measured at performance of experience of idling has made 103,282 W, and maximum –
104,814 W. Hence, at change of average temperature of magnetic system
from 13 ºÑ to 45 ºÑ, i.e. on 32 ºÑ or on 246 %, change of total
losses of active power on all three phases of
the tested transformer, measured at performance of experience of idling has made – 1,461 %.
Similar experiments have been spent for voltage 200,
210, 230 and 240 V. Following the results of their carrying out similar
results have been received. The schedule of change
of values of total losses of active power on all three phases of the tested transformer, measured at
performance of experience of idling at conditional voltage 200, 210, 220, 230,
240 V, from average temperature
of the magnetic system, 1st order approximated by a polynom
is shown in figure 8.
Fig 8. The diagram of change of values of total losses of active power on
all three phases of the tested transformer,
measured at performance of experience of idling, from average temperature of the magnetic system, 1st order
approximated by a polynom:
1 – at conditional voltage 200 V;
2 – at conditional voltage 210 V;
3 – at conditional voltage 220 V;
4 – at conditional voltage 230 V;
5 – at conditional voltage
240 V
Hence, as well as in [5, 6] the
temperature of magnetic system of the tested transformer influences value of
losses of idling. With growth of temperature of magnetic system total losses of
active power of idling on all three phases of
the tested transformer decrease.
Conclusion.
The temperature of magnetic system of
the tested transformer influences value of losses of idling. With growth of
temperature of magnetic system total losses of active power of idling on all
three phases of the tested transformer
decrease on the average for 2 %.
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