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8Рис. 3. Пример структурной схемы алгоритма расчета эквивалентных часов эксплуатации
ОПРЕДЕЛЕНИЕ ОБЛАСТИ ОБЕСПЕЧЕНИЯ ЭЛЕКТРОМАГНИТНОЙ СОВМЕСТИМОСТИ ДУГОВЫХ СТАЛЕПЛАВИЛЬНЫХ ПЕЧЕЙ С СИСТЕМОЙ
ЭЛЕКТРОСНАБЖЕНИЯ
Салтыков Валентин Михайлович,
доктор технических наук, профессор кафедры Электромеханика и автомобильное электрооборудование, Самарский государственный технический университет Салтыков Александр Валентинович кандидат технических наук, доцент кафедры Автоматизированные электроэнергетические системы,
Самарский государственный технический университет
DEFINITION OF THE FIELD OF ELECTROMAGNETIC COMPATIBILITY OF ARC FURNACES AND ELECTRIC SUPPLY SYSTEM
Saltykov V.M. Doctor of Technical Sciences, Professor of Electromechanics and electric motor, Samara State Technical University
Saltykov A.V. Ph.D., assistant professor of Automated electric power systems, Samara State Technical University
АННОТАЦИЯ
В работе показан способ решение проблемы электромагнитной совместимости электрических характеристик нагрузки дуговых сталеплавильных печей, определяемых с учетом параметров системы электроснабжения, и условия их ограничения по показателям качества напряжения в питающей электрической сети.
ABSTRACT
The paper demonstrates the way of soling the problem of electromagnetic compatibility of arc furnaces' load electric characteristics, including electric supply system parameters, and conditions for their limitations by voltage quality indicators in supply main.
Ключевые слова: дуговая сталеплавильная печь, система электроснабжения, показатели качества напряжения, электромагнитная совместимость.
Keywords:North-East of Russia, the Arctic Zone, the Main Watershed of the Earth, Fresh Groundwater Resources, Winter Low Water, the Artificial Replenishment of Groundwater Resources
Introduction
The solution of electric supply system - arc furnace (ESS -AF) electro-technical complex electromagnetic compatibility has two interconnected directions: providing electromagnetic compatibility (EMC) conditions for AF built-in power leads and providing EMC conditions for other power-consuming units [1].
EMC for AF power leads is determined both by conditions for providing certain values of voltage quality indicators (VQI), i.e. at the ESS point where they emerge and are maximal, and by the degree of lower quality voltage influence, voltage digression in the first place, on electric and operational parameters of AFs proper as well as their electro-technological modes.
It should be noted that AF electric characteristics and electro-
technological modes also limit operational modes of electro-technological equipment such as AF furnace transformers.
To provide ESS - AF EMC it is necessary to develop provisions for permissible interference level for AF built-in power leads, i.e. for such power quality interferences as fluctuations and distortions of voltage sine wave (non-sinusiodality) appearing on AF power leads so that at power leads of electric receivers sensitive to the above power quality reduction the requirements of GOST (National State Standard) P 54149-2010 [2] are not violated.
Power quality requirements stated in GOST P 54149-2010 [2] embrace electric supply systems circuits of alternate three-phase and one-phase current with 50 hz frequency. Power quality standards are electromagnetic compatibility levels for conductive interferences that provide for EMC of power suppliers' electric circuits, as well as those of power consumers.
Besides, EMC requirements must include the influence of deviations, voltage fluctuations and sine wave voltage distortion (non-sinusoidality) in AF power leads on respective power quality in power leads of adjacent power consuming units.
It should be noted that the number of power consumers sensitive to fluctuations and sine wave distortions in industrial ES systems greatly exceeds that of power consumers creating the above deviations in electric circuits; therefore, setting standards for voltage fluctuations and sine wave distortions directly at AF built-in power leads will make it possible to reduce the number of control points and to combine ESS voltage quality control and management with maintaining definite electric parameters of AF load.
So it seems reasonable, from EMC position, to consider questions of standard-setting for voltage deviations, fluctuations and sine wave distortions at AF power leads in
complex, proceeding from the following positions:
1) providing rational electric and operational AF characteristics including permissible voltage deviations, fluctuations and sine wave distortions at AF power leads;
2) sticking to GOST P 54149-2010 [2] requirements for voltage fluctuations and sine-wave distortions at any power leads' sections of any electric consumers sensible to them and at the balance inventory boundaries.
Conditions for Providing Electromagnetic Compatibility between Arc Furnaces and Electric Supply System
On the basis of the technique developed earlier it is possible to obtain values of AF operating current for all AF's: Ip and corresponding operational AF characteristics pertaining to any given rational (or otherwise) AF mode, maximum productivity mode in the first place: Gmax, considering initial voltage levels
values group:
SU
U
eno
short circuit power:
5U,
S
& , voltage
deviations: 0 and fluctuations: 1, voltage sine wave distortion ratios: KU at AF power leads, interconnection between which may be reflected as corresponding graphs.
The illustration of the statement is provided on Fig 1. for AF-40. The y-axis of the plot presents maximum productivity values: Gmax, and x-axis shows voltage fluctuations values:
SUt (AI = Iâ )
SU, däa(ß = 0,5)
and ' ' , voltage sine wave
distortion ratios: KU, appearing at AF built-in power leads under furnaces' operation at preset operational (rational) current for AF at maximum level of furnace transformer transformation, obtained within wide range of supplying ESS parameter values
U
eNO âNï
presented as initial voltage levels:
S
power values: ^ ANÏ at AF power leads.
and short circuit
I Ao + I Ao I AA+ I AA 20
100 I AA
11 ê = 1,1U
10,5 êA = 1,05U„
10 êA = 1,0Um
9,5 êA = 0,95U„ 9 êA = 0,9U,„
âëy Sêç 300 I AA cosô = 0,727
SU, ,%(AI = Ip ),
-A—i
SUt«„%(ß = 0,5) :
—;
""
Fig. 1. ACKLM Electromagnetic Compatibility Area ofAF-40 Load (SnT = 15 MBA, UH = 10 kB) at Maximum AF Productivity Mode Gmax = Gp
D
F
y-E
From Fig. 1 we see that maximum productivity values: Gmax, defined under short circuit power at AF power
leads: • ANÏ = œ , i.e. over y-axis (theoretical calculation technique), substantially differ from the above AF parameters values calculated over actual short circuit power values at AF
power leads: ç •AN , defined with inclusion of ESS parameters (resistances).
It should be noted that under: ■Mt it is impossible to determine power quality indices at AF leads and in ESS, i.e. we lack the possibility to identify EMC within ESS-AF electro-technical complex.
In analyzing conditions for AF load supply it is evident that
short circuit power at AF power loads S^ j^j , defined by ESS parameters (resistances) cannot exceed tripping power:
-Wr
S (current I ) of switches applied, defined by the
в,откл v в.откл' 11' J
expression:
b ■ Qä
ENO, ÄN1 ■ Iâ,îôêë - , ÄN1 ,â
■h
i.e. under condition:
oNÈNÔ ,âîï +
Ue
■Ut
Ut
-■100% - +5%
ША
о, ÄN1
SU о, ÄN1
> -5%
и.
-Ui
where: Ui are voltage deviations
at AF power leads caused by AF load.
Therefore, in analyzing AF load influence on the circuit we needn't take into account the limit of positive voltage deviations,
since it is determined by initial voltage only: ueno , the value
of which is known and is always bigger than: .
Conditions for non-exceeding permissible negative voltage deviations at AF power leads may be expressed through supplying ESS parameters and AF load parameters according to expression:
100%
, ÄN1 ,än
Ue
Fig. 1. also reflects permissible short circuit power at AF power leads •ANI •â limited by AC line.
In analyzing conditions for AF load power supply from
g U
permissible voltage deviations at AF power leads: "•ANI it is necessary to take a number of factors into consideration. 1. Before AF hooking-up the initial voltage level at AF power
leads: ÈNÔ AN:I is determined by ESS mode conditions (system load depending on the time of the day, regulation conditions, etc.), and AF power leads voltage level may deviate from nominal both on the plus side, up to maximum operating voltage value, and on the minus side.
It should be noted that the increase in initial voltage level at AF power leads above nominal value leads to extra losses in furnace transformers' steel and reduces insulation life time. In principle, by conditions of permissible positive voltage deviations at AF power leads in calculations it is reasonable to restrict them to the level: UÈNÔ.ANI + = ' UÎÎi
that allows us to determine permissible short circuit power values at AF power loads: •ш , UNDER при under which AF load in operating mode will not lead to GOST Р 541492010 [2] requirements violation concerning voltage deviations
RT T
under Ш ,âîï
SÊ , ÄN1 Mi > b ■ QäN
> -5%
by expression:
U,
Ue
- 0,9 U,
Having expressed reactive power consumed by AF in operational mode through furnace contour:
qànï = 3 '1 an! 'x e
we may visualize short circuit power permissible values as follows:
X, U
E ' ENO, ÂNJÏ
I,
-0,§ Ut )- Uen
(Ue.
- 0,9 ■ Ut )
I
On Fig. 1. the restriction of voltage positive deviations: is reflected by AB line.
2. In the moment of AF load hooking-up negative voltage deviation appear, as a rule at AF power leads and supplying ESS due to, mostly, AF operating mode.
It is reasonable to restrict negative voltage deviations at AF power leads caused by operational (rational) AF modes to the level of 5% of nominal voltage, i.e. at narrower range than it is generally accepted now for normally permissible voltage deviations values on electric receiver leads set by GOST P 54149-2010 [2], which can also be applied to AF power leads and especially to main step-down substations' power transformers' parallel windings power leads, for instance MSDS transformers with split windings etc., where industrial electric receivers are hooked up, which can be presented as expression:
where: mp = YEG is AF operational (rational) current proportionality ratio: Ip and AF exploitation short circuit (ESC)
current: ; kd is furnace transformer transformation
ratio; Z& , XE are complete and inductive furnace contour resistance under ESC mode.
Through obtained short circuit power values at AF power
leads ■jiNi under set ESS conditions we may determine permissible AF load, represented, for instance, as reactive
power ,au by expression:
Q . , ANI ' ENO , ANI — -Ui )
qANI ,aii — hTr
b ' U ENO ANI
-7 (Ueno,ÄNI - 0,9 ■U, )-UÈ
Condition for non-exceeding negative voltage deviations (S^ANI •an - - under permissible AF leads short circuit
power values: S® • 'ANI m , initial voltage levels: ÈNÔ •ANI under permissible AF load in operational mode, represented
as permissible reactive power: QANI •al 1 , on Fig.1 at BC line.
And so, the area of AF parameters admissible by operational mode reflected on Fig.1 will be limited within ABC triangle characterizing ESS parameters at AF power leads:
AC being maximal short circuit power permissible from the
S- ■■ —
position of braking capacity of switches: % •ANI ;
AB being initial voltage: UÈNÔ.ANI += Uni or permissible
SUà = +5% voltage deviations: ;
BC being permissible negative voltage deviations:
UENO,ÄN1 ■Ut
m
д
ENO, ÄN1
, ÂNÏ ,âîi > b
m
д
or
m
Q
Ki, -¿% m
äll —
-m-
SUA
o,ÂNÏ ,âîï -
= -5%
It should also be noted that AF operation in meltdown mode is accompanied with short-term maximum voltage drops at
AF power leads, caused by ESC currents: , that may
reasonably be considered short-term voltage deviations. The correctness of this approach is conditioned by characteristics of voltage regulators applied in AF's.
Research tests show that under ESC transition time from AF operational current to ESC current is about 0,8-1,5 sec., while general time of ESC elimination by AF power regulator is from 3 to 5 sec. For power receivers fed from leads joint with AF such mode may be regarded as post-fault, and for AF proper -as maximum permissible load mode, and it allows us to lower the boundary of permissible power deviations at AF power leads under ESC mode up to -10% of nominal value, which corresponds to permissible negative deviations level according to GOST P 54149-2010 [2]:
SUo,ÂNÏ ,YÊÇ,âîï
>-D %
SU
o,ânï ,yeç
where:
uânï ,yêç uî
uf
100%
Ue
,ÂNÏ .YÊÇ.Si
> b-Q
Ue
ÂNÏ , YEÇ,dîi
= 3-1 2
■xt
QaNI ,YEQ = 3 '1 ANI ,YEQ ' X E we may present permissible short circuit power values as:
SÇ ,ÂNÏ ,YÊÇ,âîi >
b-Xe -(09-Uj )2-UENO,ÂNÏ K-Ï -ZÊ-(UENO,ÂNÏ -0,9•Ui )
St-
C-Ut,
IÇ ,ANÏ ,YÊÇ,âîï
UENO,ÂNÏ 0,9 - Uj
Q
S
g ,ÂNÏ ,YÊÇ
-(Ue
- 0,9- U )
ÂNÏ ,YÊÇ,âîï - '
b-Ut
Obtained conditions for non-exceeding negative voltage
deviations on the level 0ANÏ •YÊÇ,a" - ~ ® % at AF power leads under AF ESC mode are reflected on Fig.1 as KN line.
At the same time the area of AF permissible working modes (electric and operational characteristics) set by permissible parameters of supplying ESS at AF power leads is narrowed; on Fig.1 it is reflected by triangle ACKN.
The multitude of limitations on minimally permissible AF S- ■■ —
short circuit power: % •ANÏ •m' and on maximally permissible
reactive power consumed: ,a" under operational
(rational) AF mode also makes it possible to determine
ÔU
permissible voltage deviations values: tM" , appearing at AF power leads through the formula:
SULm *
b-QÂ
Ut
JÇ , ÂNÏ ,mï
-ß- 100%
are
voltage deviations at AF power leads conditioned by AF load under ESC mode.
We may determine supply circuit and AF load parameters limitations for the case considered, using relationship:
b'QANj .YEg.aii < U ENO, ANI — ' U1
where: ^ is AF current oscillability ratios, including AF current oscillability ratios defined by AF automated voltage
B ...
regulators' characteristics: .
Under AF current oscillability ratio: ^ = 1,65 corresponding
M = I.
to AF arc current swing: . maximum voltage
fluctuations values: t at AF power leads for rational mode considered are presented on Fig. 1, as it was stated earlier, as x-axis. In evaluating AF current swings conditioned by AF automated power regulator (APR) used AF current oscillability
The magnitude of short circuit power values at AF power leads may then be determined by expression:
ß
dàa
, are different of different types of APR. On
Having expressed reactive power consumed by AF under ESC mode through furnace contour parameters
ratios:
x-axis it is accompanied with proportional change in voltage
fluctuations scope: ^ daa.
Voltage fluctuations appearing at AF power leads under ESC mode are determined by correlation between maximum
AF reactive power consumed: QaNn JÊç,an and minimum permissible short circuit power: £ •ANÏ •YEÇai at AF power
leads subject to limitations: 0ANÏ jÈç,au — ® % by the expression:
Taking into account known AF furnace contour parameters the previous expression may be generalized as:
SU
b-Q_
ÂNÏ ,YÊÇ,âu UENO,ÂNÏ
t.YÊÇ,âîï
,ÂNÏ ,YÊÇ,âîï
U
-ßYÊÇ '100%
ß
where YEÇ is AF current oscillability ratio under
where C coefficients for a number of AF's are equal, respectively, to: for AF-6 C = 8,4; for AF-40 C = 25,0; for AF-100 C = 151,0.
Reactive power values consumed by AF under ESC mode in terms of pre-set ESS conditions and permissible voltage deviations on the level of - 10% at AF power leads may be determined by the expression:
SI = IYÊÇ .
Conditions for providing EMC between AF and ESS of AF-ESS electro-technical complex considered may be supplemented with GOST P 51317.3.3-2008 (IEC 61000-33:2005) [3] requirements for permissible voltage oscillation values at voltage-oscillation-sensitive power receivers' leads:
5Utj •an by means of their reduction to AF power leads with simultaneous limitation of permissible voltage fluctuations at AF power leads: :
-•SU
tî ,äu Jîdi
i = Y ÂNÏ -1 -SUt,î
ÎÂNÏ , YEÇ, âîï
< 0,$ XêUî
Kï -Z 2
where:
Ê Äxrj
ÂNÏ -I
is transmission ratio between voltage
S
ÂNÏ ,YÊÇ,âiï
..... -0 9•U
u ENO, ÂNÏ u
SUt.ÂNÏ Mi <
or
8U
t, än1 mi
those at
fluctuations at AF power leads:
sensitive receivers' leads: *^ •al1 , where they are specified by GOST P 51317.3.3-2008 (IEC 61000-3-3:2005)
Y -----
[3]; ANI —I is voltage relaxation ratio that is in inverse proportion to voltage fluctuations transmission ratio from AF
i i E Anï —f power leads: .
As previous research has shown, voltage oscillation values
at sensible receivers' (light load) power leads:
: 8 U,j
ratio:
E ä
ÄN1 -I
8Ut. ÄN1 .âîi —
E,
■ ■SU,
t.N ,âîï ,iîdi
E
AN! -В
On + O,
O + O.
Ô,I
or
E
O,
O~
ÄN1 -S)
On + O,
On + OÔ,&
E
points of connection to power circuits): U'au 'lldl by their reduction to AF power leads through the expression:
KU ,AN! Mï — Y ku (AN! -i ) ■ K
U,âîï ,iîdi
where: ^ Ku(^ ^ ) is damping ratio for voltage higherorder harmonics inversely proportional to transmission ratio:
Wku (jANI -b ) , which, in turn, is determined by expression similar to those applied for voltage fluctuations:
and
voltage fluctuations values in common points of their ESS and
SU
that of AF load: •atI (as a rule, this is three-winding and
split-winding MSDS transformers midpoint (mp) voltage) are practically equal, i.e.:
SUtj •an ~SUt$ •an
Therefore, in the expression given above transmission
Ykv (An! -i ) :
1
Wk
Ku ( AN! -¥ )
XC + Xr
Xc
may be substituted by transmission ratio:
ANI , and AF power leads' fluctuations permissible by GOST P 51317.3.3-2008 (IEC 61000-3-3:2005) [3] may be determined by expression:
where E anï is voltage oscillation transition ratio
between AF power leads and MSDS transformers' midpoint determined by ratio of ESS inductive resistance up to midpoint:
Ô" and inductive resistance of ESS element: Ôy , i.e. MSDS transformer winding between AF power leads and midpoint:
where: XC is ESS resistance up to common connection
point; Ôy is ESS element (elements) resistance between AF power leads and industrial load hook-up point.
Limitation of permissible AF operational modes area and permissible voltage curve sine wave distortion ratios values: KU at AF and industrial load common connection points regulated by GOST P 51317.4.7-2008 (IEC 61000-4-7:2002) [4] requirements is presented on Fig.1 as a straight line parallel to y-axis.
Joint analysis of ESC permissible values at AF power leads under voltage fluctuations norm-setting conditions and ESS voltage curve sine wave distortion ratio shows that voltage fluctuations leading to significant limitations of permissible AF operational modes are dominant factor in providing ESS-AF EMC.
In addition, from electro-magnetic compatibility conditions diagram for estimated AF load characteristics (Fig.1 for AF-40) we may also specify fulfillment of furnace transformer (FT)
S-, ■■■ S- ■■■
load: 111 •ÏD and overload wdaad, D mode conditions;
Sf
S,
for AF-40 specifically, are: ôàà'ANI < = 15 MBA
S '1'ЛдЛл
Area limitation of permissible AF operational modes and permissible voltage fluctuations at AF power leads:
SU
t,AN1 ,an from the standpoint of permissible voltage fluctuations at sensitive (lighting) receivers' power leads:
SU
a M , regulated by GOST P 51317.3.3-2008 (IEC 61000-3-3:2005) [3] requirements for voltage fluctuations is represented on Fig. 1 as a straight line parallel to y-axis.
In a number of cases these conditions result in limitation of permissible AF operational modes (on Fig.1 it is reflected by LM line), and the area of permissible AF operational modes will be limited for AF-40 under maximum productivity mode, as it is shown on Fig.1 by ACKLM polygon.
Conditions for ESS-AF EMC may be complemented with GOST P 51317.4.7-2008 (IEC 61000-4-7:2002) [4] requirements for maximum permissible value of voltage curve sine wave distortion ratio at sensitive receivers' power leads (at common
and dM •ANI < = 18 MBA.
Conclusion
Summing up, in order to provide conditions for electromagnetic compatibility of electric supply system - arc furnace electro-technical complex expressed as permissible AF electric and operational characteristics, voltage quality indicators, permissible furnace transformer loads and overloads characterized by AF electro-technological modes it is expedient to apply expressions and graphic dependences provided in this paper.
Besides, graph analytic dependences obtained may be augmented with other EMC indices, as well as used for a number of other types of electric power receivers.
Sources (in Russian)
1. В.М. Салтыков, О.А. Салтыкова, А.В. Салтыков. Влияние характеристик дуговых сталеплавильных печей на качество напряжения в системах электроснабжения: Под общ. ред. В.М. Салтыкова. - М.: Энергоатомиздат, 2006. -245 с.
2. ГОСТ Р 54149-2010. Электрическая энергия. Совместимость технических средств электромагнитная. Нормы качества электрической энергии в системах электроснабжения общего назначения. М.: Стандартинформ, 2012.
3. ГОСТ Р 51317.3.3-2008 (МЭК 61000-3-3:2005). Совместимость технических средств электромагнитная. Ограничение изменений напряжения, колебаний напряжения и фликера в низковольтных системах электроснабжения общего назначения. Технические средства с потребляемым током не более 16 А (в одной фазе), подключаемые к электрической сети при несоблюдении определенных условий подключения. Нормы и методы испытаний. М.: Стандартинформ, 2009.
4. ГОСТ Р 51317.4.7-2008 (МЭК 61000-4-7:2002). Совместимость технических средств электромагнитная. Общее руководство по средствам измерений и измерениям гармоник и интергармоник для систем электроснабжения и подключаемых к ним технических средств. М.: Стандар-тинформ, 2009.
CONDITIONS ELECTROMAGNETIC COMPATIBILITY BY THE MAGNETIC FIELD OF INDUSTRIAL FREQUENCY IN THE SURROUNDING AREA FROM CABLE SYSTEMS
POWER SUPPLY
Mayevskiy B.Y.
Doctor of geological sciences, Professor Kurovets S.S.
PhD, Associate Professor Ivano-Frankivsk National Technical University of Oil and Gas УСЛОВИЯ ЭЛЕКТРОМАГНИТНОЙ СОВМЕСТИМОСТИ ПО НАПРЯЖЕННОСТИ МАГНИТНОГО ПОЛЯ ПРОМЫШЛЕННОЙ ЧАСТОТЫ В ОКРУЖАЮЩЕМ ПРОСТРАНСТВЕ ОТ КАБЕЛЕЙ СИСТЕМ ЭЛЕКТРОСНАБЖЕНИЯ
Салтыков Александр Валентинович, кандидат технических наук, доцент кафедры Автоматизированные электроэнергетические системы, Самарский государственный технический университет
Салтыков Валентин Михайлович, доктор технических наук, профессор кафедры Электромеханика и автомобильное электрооборудование, Самарский государственный технический университет
ABSTRACT
The conditions of electromagnetic compatibility (EMC) for the equipment and electromagnetic safety (EMS) staff offices and the public from exposure to magnetic fields of industrial frequency currents generated electricity cable systems, low voltage.
АННОТАЦИЯ
Показаны условия обеспечения электромагнитной совместимости (ЭМС) для технических средств, а также электромагнитной безопасности (ЭМБ) персонала офисных помещений и населения, от воздействия напряженностей магнитных полей промышленной частоты, создаваемых токами кабелей систем электроснабжения низкого напряжения.
Keywords: electromagnetic compatibility, electromagnetic security of, the magnetic field of industrial frequency, system power supply-the supply of low voltage.
Ключевые слова: электромагнитная совместимость, электромагнитная безопасность, напряженность магнитного поля промышленной частоты, система электроснабжения низкого напряжения.
Introduction providing process, the reliability and the required sanitary and
The main sources of electromagnetic fields in electric power epidemiological conditions for staff. This is important from
us-the sense of forming the electromagnetic environment the perspective of the functioning of all systems of an office
are: overhead transmission line high voltage, static electricity, building and conditions EMC is the power supply system.
strong industrial electrical installations, switchgear, and so on These circumstances lead to the need for theoretical
[1]. Simultaneously increasingly used electronic equipment in and experimental studies of electromagnetic environment
the relay protection systems, security and emergency control (EME), conditions electromagnetic compatibility (EMC) and
of electrical high and low voltage. The electronic equipment electromagnetic safety (EMS) in the areas of office buildings,
is becoming more sensitive to electromagnetic interference, equipped with computers and other office equipment [2], and
especially to the magnetic field appearing in the secondary to assess the influence of power supply system's low voltage.
circuits substations, which are the sources of operating Based on the foregoing, in this paper based on the working
current, the switching switches the high and low voltage, large methods of calculation [3] the nature of the variation of
short circuit currents, the electromagnetic field of industrial the power frequency magnetic fields in the surrounding
frequency and radio frequency. single-phase and three-phase of four-wire and cable power
Enough is complicated electromagnetic environment supply systems, showing the conditions of electromagnetic
(EME) and in office buildings, which is characterized by a large compatibility (EMC) for the equipment used in residential
variety of electromagnetic fields (EMF) by type, frequency , commercial and industrial areas, as well as providing
range, and levels. This diversity EMF is determined by a large conditions for electromagnetic safety (EMs) in accordance
number of computer equipment, primarily computers, lighting with the requirements of sanitary-epidemiological rules and
systems, air conditioners, elevators, alarms and other electrical norms (SRN) to protect personnel office and the public from
equipment and supply their electric systems and networks, exposure to magnetic fields.
