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Файл:The Electromagnetic Interference in the Electrical Power Supply System. The long-term variance of the voltage specifications. Study guide
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5. FREQUENCY DEVIATION
f
f
f
5.1. The Main Definition and Standards
The indicator of CE related to frequency is the deviation of the value of
the fundamental frequency of the power supply voltage from the nominal
value, Δf, Hz:
ff
mnom
, (5.1)
Where
voltage, Hz, measured in the time interval of 10 s;
is the value of the fundamental frequency of the power supply
m
– nominal frequen-
nom
cy of power supply voltage, Hz.
The frequency deviation in synchronized power supply systems should
not exceed ± 0.2 Hz within 95 % of the time interval of one week and
± 0.4 Hz within 100 % of the time interval of one week [14, p. 5].
The main reason for the occurrence of frequency oscillations are powerful electric power receivers with rapidly alternating resistive loads (thyristor
converters of main drives of rolling mills). The active power of these receivers varies from zero to the maximum value in less than 0.1 s, as a result
of which frequency oscillations can reach large values.
Changes in frequency, even within narrow limits, affect the operation of
electrical grids and receivers of electrical power. Lowering the frequency of
the current leads to an increase in power losses and voltage in the power
supply networks and to underproduction. The effect of reducing the frequency on the required power of power consumers is different.
The power consumption by electric lighting receivers, electric resistance
furnaces and electric arc furnaces does not significantly depend on frequency.
The power consumed by the mechanisms with a constant torque on the
shaft (metal cutting machines, piston pumps, compressors, etc.) is proportional to the frequency.
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Power losses in the network are proportional to the square of the frequency.
The power consumed by the mechanisms with the fan moment of resistance (centrifugal pumps, fans, smoke exhausters, etc.) is proportional to
the frequency in the third power.
For centrifugal pumps operating on a network with a large static pressure (retarding), for example, for feed pumps of boiler houses, the power
consumption is proportional to a frequency of a degree higher than a third.
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CONCLUSION
This manual considers the quality of power supply from the standpoint
of analyzing the parameters of power quality according to GOST 32144-
2013. The issues of the influence of various parameters of power quality on
the operation of power consumers, basic definitions and standards for power
quality parameters, methods for estimating deviations of power quality parameters from GOST 32144-2013, as well as the ways to reduce the harmful
effects of power quality parameter violations on power supply systems are
considered.
In electrical networks up to 1000 V the highest damage to the consumer
is caused by current and voltage high harmonics. Moreover, as practice
shows, the contribution of a small non-linear consumer to the distortion of
the sinusoidal voltage curve significantly exceeds the negative impact of a
large industrial consumer. The causes of the high harmonics are non-linear
current-voltage characteristics of electrical equipment.
It should be noted that recently there has been a rapid growth of semiconductor elements, which is a part of numerous small non-linear consumers (televisions, computers, lighting, power equipment for the example of a
frequency-controlled electric drive, etc.). This increase is typical for any
power supply systems: industrial, urban, rural, etc. Therefore, specialists
engaged in the design of various power supply systems are becoming increasingly interested in the non-sinusoidal currents caused by shallow nonlinear loads.
Power quality issues are an integral part of the problem of electromagnetic compatibility of electrical equipment and electrical networks and have
recently become particulary relevance due to the introduction of highprecision process equipment for the operation of which high-quality electrical energy is required. Therefore, special attention is given to the issues of
electromagnetic compatibility and power quality.
63
REFERENCE
1. GOST 13109-67. Elektricheskaya energiya. Normy kachestva elektricheskoj
energii u ee priemnikov, prisoedinennyh k elektricheskim setyam obshchego
naznacheniya.
2. GOST 13109-87. Elektricheskaya energiya. Trebovaniya k kachestvu elektricheskoj energii v elektricheskih setyah obshchego naznacheniya.
3. GOST 13109-97. Elektricheskaya energiya. Sovmestimost' tekhnicheskih
sredstv elektromagnitnaya. Normy kachestva elektricheskoj energii v sistemah elektrosnabzheniya obshchego naznacheniya.
4. GOST R 54149-2010. Elektricheskaya energiya. Sovmestimost' tekhnicheskih sredstv elektromagnitnaya. Normy kachestva elektricheskoj energii v
sistemah elektrosnabzheniya obshchego naznacheniya.
5. GOST 32144-2013. Elektricheskaya energiya. Sovmestimost' tekhni-cheskih
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Vladimir Ya. Olhovskiy
Tatyana V. Myateg
Olga S. Atamanova
THE ELECTROMAGNETIC INTERFERENCE
IN THE ELECTRICAL POWER SUPPLY SYSTEM
THE LONG-TERM VARIANCE OF THE VOLTAGE SPECIFICATIONS
Managing Editor I.P. Brovanova
Art Director A.V. Ladyzskaya
DTP S.I. Tkacheva
Signed Print 05.11.2019
Format 60 × 84 1/16. Newsprint
Uch.-ed. 1. 3,95. Pecs. 1. 4,25.
Quantity 100 copies. Ed. No. 162. Order No. 1518
Tax credit-the Russian Classification of product
Edition corresponds to 95 3000 OK 005-93 (OKP)
Publisher of the Novosibirsk State Technical University
630073, Novosibirsk, Russia, 20, Karl Marx prospect
Tel: (383) 346-31-87
E-mail: office@publish.nstu.ru
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