Добавил:
ivanov666
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз:
Предмет:
Файл:The Electromagnetic Interference in the Electrical Power Supply System. The long-term variance of the voltage specifications. Study guide
.pdf
Ministry of Higher Education and Science of the Russian Federation
__________________________________________________________________________
NOVOSIBIRSK STATE TECHNICAL UNIVERSITY
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
Approved by The Aditorial Board of NSTU as a manual
NOVOSIBIRSK
2019
UDC 621.311.018.33.78:658.26
O-567
Reviewer:
PhD (Eng.), Assoc. Prof. D.A. Pavluchenko
PhD (Phil.), Assoc. Prof. A.I. Bochkarev
The manual was prepared by the Electrical Power Supply
Systems Department, the Department of Foreign Languages
of Engineering Faculties
Olhovskiy V.Ya.
O-567 The Electromagnetic Interference in the Electrical Power Supply
System. The long-term variance of the voltage specifications: study
guide / Vladimir Ya. Olhovskiy, Tatyana V. Myateg, Olga S. Atamanova. – Novosibirsk: NSTU Publishers, 2019. – 66 p.
ISBN 978-5-7782-3936-4
The introduced manual is aimed at theoretical and practical training of
master students in “Power Engineering” discipline (13.04.02. – Electrical
Power Industry and Electrical Engineering). One of the main tasks of the
manual is to consolidate the theoretical material studied by the students in
the first term of the Master Program. The manual also includes the issues of
electromagnetic compatibility in electrical supply systems with the object
under study – the interaction of the system “power supply network – consumer”. It allows a student to better understand the physical processes running not only during the interaction of consumer power supply systems and
power networks but also during the processes of consumerʼs interactions.
The authors analyze the quality of consumer electrical power supply on the
basis of the system operating conditions in accordance with STANDART
32144-2013.
UDC 621.311.018.33.78:658.26
ISBN 978-5-7782-3936-4 © Vladimir Ya. Olhovskiy,
Tatyana V. Myateg, Olga S. Atamanova, 2019
© Novosibirsk State Technical University, 2019
CONTENT
Introduction ............................................................................................................... 4
1. Voltage Deviations ............................................................................................... 8
1.1. Main Definitions and Standards ..................................................................... 8
1.2. Estimation of Voltage Deviations .................................................................. 9
1.3. Techniques of Voltage Deviation Decrease ................................................. 10
1.4. The Influence of Voltage Deviations on Power Consumer Operation ......... 10
2. Voltage Fluctuations ........................................................................................... 12
2.1. Main Definitions and Standards ................................................................... 12
2.2. The Ways of Voltage Fluctuations Decrease in the Power Supply
Systems ........................................................................................................ 17
3. Voltage Non-Sinusoidality .................................................................................. 19
3.1. The Main Definitions and Standards ............................................................ 19
3.2. The Currents Non-Sinusoidal of Nonlinear Loads ....................................... 22
3.3. Oscillograms of Some Non-linear Loads Currents ...................................... 23
3.4. Consumer Damage due to High Harmonics ................................................. 42
3.5. Rationing of High Harmonics ...................................................................... 47
3.6. The Ways of Voltage High Harmonics Decreasing ..................................... 49
4. Voltage Unbalance .............................................................................................. 51
4.1. The Main Definition and Norms .................................................................. 51
4.2. The Ways Voltage Unbalance Decreasing ................................................... 57
5. Frequency Deviation ........................................................................................... 61
5.1. The Main Definition and Standards ................................................................. 61
Conclusion .............................................................................................................. 63
Reference ................................................................................................................ 64
INTRODUCTION
The concept of electromagnetic compatibility (EC) can be explained
with Figure 1.1. Any mechanical unit, namely current-used equipment,
(CUE) operates in environment, which influences its functioning. The environment (Е), with a circuit as a part of it, demonstrates different features
characterized by a relevant parameters:
climate (temperature, pressure, humidity);
mechanical (vibration, impulse load);
electromagnetic (frequency, voltage deviations, voltage fluctuations
etc.).
The mechanical unit is compatible with the environment, if all environmental factors don’t produce interfering effect on its operation or the mechanical component doesn’t interfere the environment. The interfering influences are such influences, which may cause the malfunction of the mechanical unit normal operation.
The mechanical units (such as consumers) must comply with the requirements to provide compatibility with the environment: the format of
climatic modification, the class of protection, reliability (including electrical
safety), and also fire and explosion safety. The observation of these and
many other requirements while designing, manufacturing, storing, transportation and exploitation of mechanical units provide their proper compatibility with the environment.
The discipline “POWER SUPPLY” is to provide professional training
of Master Program students (13.04.02. – Electrical Power Industry and
Electrical Engineering) to meet Federal State Educational Standard of higher professional education.
EMC is a part of general compatibility, limited by factors of electromagnetic nature (shown by a dotted line in Figure 1.1). The EMC problem
can be structurally divided into three parts.
The electromagnetic compatibility (EC) is a part of total compatibility,
confined by the factors having electromagnetic nature (marked by the dotted
4
line in Fig. 1.1). The electromagnetic compatibility problem can be divided
into three parts.
DC
EPQP
CEI
EMC
EP
Disturbance
C
IFN
EC
CTV
380 V
EPSS
Dust
EE
t,°C
Moisture
Vibration
Fig. 1.1. Electromagnetic compatibility:
power supply system (EPSS); distribution cabinet (DС); external environment (EE); electric power quality parameters (EPQP), interference from the power network (IFN), conductive electromagnetic interference (CEI); connection (C); electromagnetic pickup (EP); electric consumer (EC); the voltage at the terminals of a consumer (CTV)
The first of the three parts is determined by the electromagnetic interaction of ES with the power supply network and is the subject of the study for
electric supply specialists.
The second part is connected with electromagnetic fields, which can
cause pick up effects in the elements of a power consumer, negatively affecting its work. This part is the basis of the problem of electromagnetic
compatibility of radio electronic equipment.
The third one is the electromagnetic compatibility of the transmission
facility, telecommunication and automation.
5
This study guide is devoted to the first part of the electromagnetic compatibility problem, in which the object under study is the interaction of the
system “network – power consumer”.
Historically there can be distinguished three stages in the solution of the
electromagnetic compatibility problem in power supply systems in Russia.
The first stage lasted up to the mid-70s when the mass application of the
so-called digital hardware (DH) for production and domestic purposes started. At that time EMC for traditional PCs (electric motor, electrotechnological and lighting installations, etc.) was ensured by observing the
requirements of GOST on the quality of electricity in 1967 [1]. In this
GOST, a list of electric power quality indicators (conducted electromagnetic
interference) was established and their maximum permissible values for various PCs were normalized. These interferences included: frequency deviations, voltage deviations and fluctuations, as well as indicators of nonsinusoidality and voltage unbalance.
The second stage began with mass implementation of digital technical
devices (DTD): computers, digital automation devices, telecommunications,
etc., and is characterized by active works to ensure their interference immunity. The main feature of DTD in comparison with traditional electric
consumers is an extremely low level of signals (voltage, current, duration)
used in their logic circuits, and hence the possibility of malfunctions caused
by short-term disturbances in the supply voltage. If no special measures are
taken, then it is impossible to ensure the DT nonsusceptibility to short-term
disturbances, which are defined as conductive electromagnetic interference
in power supply (CEIP). Thus, the study of these interferences as highfrequency electromagnetic disturbances in the power supply networks,
which can cause malfunctioning of a DT, began approximately from the
mid-1970s [2] and is now is formulated in an engineering discipline.
The third stage began approximately from the middle of the 80
th
, when
the main problems of EEC were solved. Whereby, in accordance with IEC
standards, power quality parameters (PQPs) and interference from the power supply network were united by the general term “conductive electromagnetic interference” (CEI) [3].
The following list of PQPs or CEIs is established in the currently appli-
cable Standard [5]
The long-term changes in voltage characteristics:
1) long-term frequency deviations,
2) slow voltage changes,
3) voltage fluctuations and flicker,
6
4) non-sinusoidal voltage,
5) voltage unbalance in three-phase systems,
6) voltage signals transmitted over electrical networks.
Random events:
7) voltage interruption
8) voltage fail and overvoltage,
9) pulse overvoltage.
The first five CEIs form so-called long-term changes in voltage characteristics, which are long-term deviations of voltage characteristics from the
nominal values and are caused mainly by load changes or non-linear load
effect. The Standard [5] establishes their permissible values.
The last three CEIs form random events, which are sudden and significant changes of a voltage shape, resulting in the deviation of its parameters
from the nominal ones. These voltage changes are caused as a rule by unpredictable events (for example, damage of the electrical network equipment of a consumer) or external environment (for example, weather conditions or actions of the party that is not a user of the electrical network). For
the last three, having a rare and random nature, the permissible parameters
are not established, but their statistical characteristics obtained by surveying
the existing electrical power supply system (EPSS) are given.
Two types of permissible PQPs values are established: normally permissible (with an integral probability of 0.95) and maximum permissible ones.
This means that at long observation intervals, for example, 24 hours, during
0.95 × 24 = 22.8 hours, the PQPs should not exceed the normal permissible
values. The rest of the time, 0.05 × 24 = 1.2 hours, these PQPs may exceed
the normal permissible values, but should not exceed the maximum permissible ones.
7
1. VOLTAGE DEVIATIONS
1.1. Main Definitions and Standards
The difference in the U voltage value at a specific point in the network
from the nominal one is characterized by
tion: voltage deviation is the difference between the actual voltage in the
steady-state operation of the power supply system and its nominal value.
Voltage deviations from nominal values occur due to daily, seasonal and
technological changes in the electrical load of consumers; power changes of
compensating devices; voltage regulation by generators of power stations
and power substations; changes in the scheme and parameters of electrical
networks [5].
Voltage deviations characterize slow changes in the power supply voltage. Indicators of EEQ related to slow changes in power supply voltage are
negative and
U
positive deviations of the power supply voltage
U
from the nominal (agreed) value in % [14, p. 6]:
UU
0
U
m
U
0
steady-state voltage devia-
U
у
100
, (1.1)
UU
U
m
where
,
UU
mm
and larger than
10 minutes;
U
are the values of the supply voltage, smaller than
U
, respectively, averaged over a time interval of
0
– is voltage equal to the nominal or agreed values.
0
In low voltage electrical networks, the
0
U
0
100
, (1.2)
U
0
U
nominal power supply
nom
voltage in Russia is 380/220 V. In the electrical networks of medium and
8
high voltage a
U
matched value of power supply voltage is assumed in-
c
stead of a nominal one.
For the above EEQ parameters, the following norms are established:
positive and negative voltage deviations at the point of electrical energy
transmission should not exceed 10 % of the nominal or matched value of the
voltage for 100 % of one week time interval. The established standards for
slow changes in power supply voltage refer to 1008 measurement time intervals of 10 minutes each.
1.2. Estimation of Voltage Deviations
Voltage deviations during long time intervals (for example, 24 hours)
are shown to the utmost with a voltage deviation graph (Fig. 1.2). Two types
of
integral characteristics.
deviation estimates are used: estimates for limiting values and
()
Ut
у
voltage deviation flickout
more than 1 minute more than 1 minute
more than 1 minute
Fig. 1.2. The voltage deviation characteristic.
()
The estimates for the limiting values are
the “+” sign in a minimum load mode and
U
maximum values with
inm
()
U
maximum values with the
inm
“–” sign in a maximum load mode (Fig. 1.3). Wherein if
12
0,05
, then the example shown in Figure 1.3 is permissible. Here
24
9
inm
10 %
U
and
is the total time during which the
12
value exceeds
()
Ut
in
5 %
normally acceptable values, but does not exceed +(–) 10 %.
1.3. Techniques of Voltage Deviation Decrease
The techniques to reduce the voltage deviations are divided into two
types: voltage change in the network and voltage regulation. Measures to
change the voltage are one-time in nature and influence the position of the
graph relative to the ordinate axis in Fig. 1.2. They include:
E
–
change with the help of no-load tap changing of a substation
T
transformer;
– the change of the average voltage in the center of the power supply;
– the increase of the power of substation transformers;
– the increase of supply lines sections.
These measures make it possible to reduce
affect
the diversity relative to the average, characterized by
()
Ut
in
dispersion.
Voltage regulation measures are carried out at the pace of the process
and provide a reduction in diversity
the decrease in
2
dispersion.
U
in
relative to the average, that is,
()
Ut
in
They include:
– counter load voltage control in power supply networks;
– voltage regulation on the 10 (6) kV distribution substation tires main
step-down substation (MSDS) with the help of on-load tap-changer transformer MSDS;
– voltage regulation by reactive power compensation;
– application of individual voltage regulators for individual electrical
consumers.
(Fig. 1.2) and not to
U
uv
2
U
in
1.4. The Influence of Voltage Deviations on Power
Consumer Operation
Voltage deviations affect differently the operation of various electrical
equipment. From the point of view of the analysis of this influence, all electrical consumers can be divided into three groups.
10
Соседние файлы в предмете [НЕСОРТИРОВАННОЕ]