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ELEKTRYKA
Zeszyt 3-4 (223-224)
2012
Rok LVIII
Olgierd MAŁYSZKO, Michał ZEŃCZAK
Katedra Elektroenergetyki i Napędów Elektrycznych, Zachodniopomorski Uniwersytet
Technologiczny w Szczecinie w Szczecinie
ELECTRIC AND MAGNETIC FIELDS NEAR NEW POWER
TRANSMISSION LINES
Summary. The article discusses electric and magnetic fields around new power
transmission lines. The paper takes into considerations comparison of electric and
magnetic fields near PTL with traditional AFL wires, traditional AFL wires with
monitoring of temperature and HTLS wires.
Keywords: electric field, magnetic field, power transmission lines
POLA ELEKTRYCZNE I MAGNETYCZNE WOKÓŁ NOWYCH LINII
ELEKTROENERGETYCZNYCH
Streszczenie. W artykule omówiono problematykę pola elektrycznego i magnetycznego wokół nowych linii elektroenergetycznych. Tekst uwzględnia zagadnienia:
porównanie pola elektromagnetycznego w pobliżu PTL z tradycyjnych przewodów AFL,
tradycyjne przewody AFL z monitorowaniem temperatury i HTLS.
Słowa kluczowe: pole elektryczne, pole magnetyczne, linie elektroenergetyczne
1. INTRODUCTION
The most important parameter of power transmission lines (PTL) is the highest value of
power (energy), which can be transmitted by these lines. There are some methods of increase
of the highest permissible power:
- usage of higher voltage of lines,
- usage of conductors with higher current- carrying capacity.
The increase of voltage is troublesome, because it is connected not only with change of
insulators, but also with change of pylons and distances between phase wires and external
objects. On the other hand increase of voltage is connected with increase of electric field
112
O. Małyszko, M. Zeńczak
intensity. The higher value of electric field intensity creates problems in natural environment
and land development (mainly housing).
The increase of current-carrying capacity may be realized by monitoring of temperature
of traditional AFL conductors or by application of high temperature low sag conductors
(HTLS). The increase of currents in wires causes the increase of magnetic field intensity near
PTL.
New trends in power transmission relate not only to conductors but also to towers.
Nowadays the new towers (EB24, EPW24, Src) are used. Some of them (EB 24, EPW 24) are
concrete poles or steel tube poles (Src). They have similar configuration like traditional tower
B2 but Src has lower distances between phase-conductors than B2.
Transmission of energy is connected with electric (EF) and magnetic fields (MF). There
are special safety rules of protection against electromagnetic fields of 50 Hz frequency. The
permissible value of EF intensity in natural environment must not exceed 10 kV/m [1], while
value of magnetic field intensity in natural environment must not exceed 60 A/m. But in
places appropriated for the public building the highest value of EF intensity must not be
higher than 1 kV/m, while the MF intensity must not exceed 60 A/m.
The paper takes into considerations comparison of electric and magnetic fields near PTL
with traditional AFL wires, traditional AFL wires with monitoring of temperature and HTLS
wires.
2. COMPARISON OF PROPERTIES OF AFL CONDUCTORS WITH HTLS
There are many kinds of HTLS conductors [2]. But the comparison should take into
consideration the same mass of conductor, because then the same towers can be used.
Therefore conductor AFL-6 240mm2 is compared to HTLS with diameter of 325.7 mm2.
Properties of HTLS and common AFL conductors are presented in table 1.
The current-carrying capacity is such the current, by which the temperature of conductors
does not exceed the design temperature. The design temperature is basis for estimation of
permissible sag and distances between conductors and crossed objects. In Poland majority of
110 kV lines have been designed for 40oC. Rest of lines in Poland has been designed for
60oC or 80oC that is for the highest permissible temperature for conductors.
Table 1
Properties of HTLS and AFL conductors
Sort of conductor
Nominal cross-section
Calculation cross-section
AFL-6 240
HTLS
2
240 AL
325.7
2
236.1 AL
325.7
mm
mm
Electric and magnetic fields…
113
con. table 1
Outside diameter
mm
Total mass per km
o
21.7
22.0
kg/km 971
977
Resistance per 1 km in 20 C
/km
0.124
0.086
Permissible temperature
o
80
180
C
There are algorithms for estimating current-carrying capacity of wires for different
weather conditions [3]. Therefore the most profitable weather is winter night: e.g.:
temperature: -10oC, wind speed: 25 m/s, sun radiation: 0 W/m2. The worst conditions are in
summer day: e.g.: temperature 30oC, wind speed 0.5 m/s, sun radiation: 900 W/m2. Results of
calculations are presented in table 2.
Table 2
Current-carrying capacity in winter night and summer day
Current-carrying capacity [A]
Type of conductor
Winter
Traditional AFL 6 240, w = 40oC (design value)
Summer
625
322
Traditional AFL 6 240, w = 80 C (design value)
735
645
Traditional AFL 6 240, w = 40oC (monitoring)
o
2120
0
o
Traditional AFL 6 240, w = 80 C (monitoring)
2654
641
HTLS w = 80oC
3205
773
HTLS w = 100 C
3432
935
HTLS w = 180oC
4045
1357
o
3. ELECTRIC FIELD NEAR NEW POWER TRANSMISSION LINES
Electric field intensity depends on configuration of line. Table 3 contains parameters of
110 kV lines hanged up on towers B2 type P and Src type P. Fig 1 presents electric field
intensity for both lines in point of maximum sag, where the distance H between conductor and
ground is the lowest permissible according to polish regulations [4]: H = 5 + Del, where Del =
0.85 m.
Table 3
Configuration of 110 kV lines on tower B2 and Src
Wire
Section
[mm2]
L1
L2
L3
Earth wire
240
240
240
70
Distance from axis of
line [m]
Tower B2
-2.80
2.80
3.60
0.5
Height above ground
[m]
5.85
9.45
5.85
12.45
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O. Małyszko, M. Zeńczak
con. table 3
L1
L2
L3
Earth wire
Tower Src
-2.40
1.80
2.40
0.0
240
240
240
70
E [kV/m]
5.85
9.75
5.85
13.95
3
2,5
B2
Src
2
1,5
1
0,5
0
-15
-10
-5
0
5
10
15
x [m]
Fig. 1. Electric field intensity near 110 kV lines with tower B2 and Src
Rys. 1. Natężenie pola elektrycznego w pobliżu 110 kV linii z wieży B2 i Src
Electric field intensity near new line (Src) is lower than electric field intensity near
traditional (B2) in all area on the height 2 m above the ground. The area with E > 1 kV/m is
shorter too.
4. MAGNETIC FIELD NEAR NEW POWER TRANSMISSION LINES
Magnetic field intensity near power transmission lines depends on configuration and
currents in wires. Fig. 2 presents magnetic field intensity near power transmission line on
tower B2 and Src with traditional conductors AFL6 240 designed for 80oC, thus the current is
equal 735 A.
Fig. 3 presents magnetic field intensity for the traditional conductor AFL6 240 designed
for 80oC (735 A), traditional AFL6 240 designed for 80oC but with monitoring of
temperature (2654 A) and HTLS 180oC (4045 A). All wires are hanged on the towers B2.
Electric and magnetic fields…
115
H [A/m]
30
25
B2
Src
20
15
10
5
0
-15
-10
-5
0
5
10
x [m] 15
Fig. 2. Magnetic field intensity near power transmission line on tower B2 and Src for current 735 A
Rys. 2. Natężenie pola magnetycznego w pobliżu linii elektroenergetycznej na wieży B2 i Src dla
bieżącego 735 A
Magnetic field intensity near line on towers B2 is higher, because the distances between
wires on the tower Src are lower.
H [A/m]
160
AFL
AFL M
HTLS
Perm
120
80
40
0
-15
-10
-5
0
5
10
x [m]
15
Fig. 3. Magnetic field intensity for the traditional conductor AFL6 240 (735 A), traditional AFL6 240
with monitoring of temperature (2654 A) and HTLS 180oC (4045 A); towers B2
Rys. 3. Natężenia pola magnetycznego na tradycyjnych dyrygentach AFL6 240 (735 A), tradycyjne
AFL6 240 z monitorowania temperatury (2654 wersja A) i HTLS 180oC (4045 A); wieże B2
Magnetic field intensity near line with traditional AFL 6 240 conductors does not exceed
permissible value in natural environment (60 A/m). The problem is with AFL conductor with
monitoring of temperature and HTLS conductors. The permissible value (60 A/m) is exceeded
when the highest value of current-carrying capacity is used. For the line from fig. 3 the
highest current must not exceed 1668 A.
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O. Małyszko, M. Zeńczak
5. CONCLUSIONS
New towers and conductors create no environmental problems with regard to electric
field intensity. However if traditional AFL conductors with monitoring of temperature or
HTLS conductors are planned the permissible value of magnetic field intensity must not be
exceeded. Therefore the criterion for magnetic field intensity [1] should be fulfilled.
BIBLIOGRAPHY
1. Rozporządzenie Ministra Środowiska z dnia 30 października 2003 r. w sprawie
dopuszczalnych poziomów pól elektromagnetycznych w środowisku oraz sposobów
sprawdzania dotrzymania tych poziomów, Dziennik Ustaw RP, 2003, Nr 192, poz. 1883.
2. Sokolik W.A.: Optymalizacja energetycznej efektywności przesyłu i dystrybucji energii
elektrycznej za pomocą niskostratnych przewodów o małym zwisie. APE’10, Present-Day
Problems of Power Engineering, Jurata, Poland, 8-10 June 2011, 29-40.
3. Małyszko O., Zeńczak M.: Power system with high temperature conductors. „Przegląd
Elektrotechniczny” 2010, nr 4, s. 170-173.
4. Elektroenergetyczne linie napowietrzne prądu przemiennego powyżej 45 kV, Część 3:
Zbiór normatywnych warunków krajowych, Polska wersja EN 50341-3-22:2001.
Recenzent: Prof. dr hab. inż. Marian Pasko
Wpłynęło do Redakcji dnia 10 grudnia 2012 r.
Dr inż. Olgierd MAŁYSZKO
Dr hab. inż. Michał ZEŃCZAK
Zachodniopomorski Uniwersytet Technologiczny w Szczecinie
Katedra Elektroenergetyki i Napędów Elektrycznych
ul. Sikorskiego 37, 70-313 Szczecin,
Tel. (91) 4494634, e-mail: [email protected]
Tel. (91) 4494634, e-mail: [email protected]