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Файл:The Electromagnetic Interference in the Electrical Power Supply System. Study guide
.pdf
Ministry of Higher Education and Science of the Russian Federation
NOVOSIBIRSK STATE TECHNICAL UNIVERSITY
___________________________________________________________________
Tatyana V. Myateg, Olga S. Atamanova
THE ELECTROMAGNETIC
INTERFERENCE
IN THE ELECTRICAL POWER
SUPPLY SYSTEM
Approved by The Aditorial Board of NSTU as a manual
NOVOSIBIRSK
2022
UDС 621.311.018.33.78(075.8)
М 99
Reviewers:
Doctor of Science (Eng), Assoc. Prof. A. G. Rusina,
Power Engineering Faculty
PhD (Eng), Assoc. Prof. A. V. Sedelnikov, JSC Elertromagistral
The manual was prepared by the Electrical Power Supply Systems
Department, the Department of Foreign Languages
of Engineering Faculties.
Myateg Tatyana V.
M 99 The Electromagnetic Interference in the Electrical Power Supply
System: study guide / Tatyana V. Myateg, Olga S. Atamanova. – Novosibirsk: NSTU Publisher, 2022. – 43 p.
ISBN 978-5-7782-4611-9
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 consumer interactions.
The authors analyze the quality of consumer electrical power supply on the
basis of the system operating conditions in accordance with STANDARD
32144-2013.
UDC 621.311.018.33.78(075.8)
ISBN 978-5-7782-4611-9 © Tatyana V. Myateg, Olga S. Atamanova, 2022
© Novosibirsk State Technical University, 2022
CONTENT
Introduction .................................................................................................... 4
1. Voltage interruption ................................................................................... 8
1.1. Voltage interruptions and overvoltage ............................................... 8
1.2. Definition and assessment of voltage dips and overvoltage ............ 12
1.3. Calculation of voltage interruptions ................................................. 13
2. Temporary overvoltage ............................................................................ 16
2.1. Overvoltage during the operation of circuit breakers ...................... 18
2.2. Overvoltage when switching electric motors ................................... 20
2.3. Overvoltage during switching filter-compensating device (FCD) ... 20
2.4. Ferroresonant overvoltage ................................................................ 22
3. Voltage pulses .......................................................................................... 24
3.1. The main definitions and Standards ................................................. 24
3.2. Ways of pulsed noise penetration into logic DTS chain .................. 28
3.3. Ways to protect a DTS from impulse noise ...................................... 30
Conclusion ................................................................................................... 41
References .................................................................................................... 42
Dedicated to the blessed memory of V.Ya. Olkhovskiy
INTRODUCTION
The meaning of the concept of electromagnetic compatibility(EMC) 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 the circuit as a part of it, demonstrates different
features characterized by the 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.
Mechanical units (such as consumers) must comply with the requirements
to provide compatibility with the environment: the format of climatic modification, the class of safety 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 necessary 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 the 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(EMC) is a part of total compatibility,
confined by the factors having the electromagnetic nature (marked by the
4
dotted 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
t,°C
EE
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 EC 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, electro-technological 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 non-sinusoidality 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 and stability.
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 with power supply (CEIP).
Thus, the study of these interferences as high-frequency electromagnetic disturbances in the power supply networks, which can cause malfunctioning
of a DT, began approximately from the mid-1970s [2].
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,
4) non-sinusoidal voltage,
6
5) voltage unbalance in three-phase systems,
6) voltage signals transmitted over electrical networks.
Random events:
7) voltage interruption
8) voltage dips 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 dimensions.
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 INTERRUPTION
Voltage interruption are of two types. The first is produced intentionally,
if the electricity consumer is informed about expected voltage interruption.
The second is caused by the external effects, breakage of the equipment or
the influence of electromagnetic interference. The voltage interruptions produced intentionally are caused by carrying out the pre-planned works in the
electricity network. Random voltage interruptions are divided into long-term
interruption (more than 3 minutes) and short-term interruption (less than
3 minutes).
In three-phase power supply systems, voltage interruptions include a situation when the voltage is less than 5% of the reference voltage in all phases.
If the voltage is less than 5% of the reference voltage not in all phases, the
situation is considered as a voltage dip.
1.1. Voltage interruptions and overvoltage
Certain requirements are imposed on the quality of electric energy, as
well as on any other type of a product as it is an indispensable condition for
the safe use of electrical device, and also directly effects the economic performance of electricity producers and consumers. Voltage dips are one of the
indicators of the electric energy quality, which in Russia is determined by
Standard 32144-2013. Standard 32144-2013 gives the following characteristic: voltage dip – an off-voltage decrease in voltage at a point of an electric
network below 0.9
close level after a period of time from ten milliseconds up to several tens of
seconds. Physically, this means that the required energy does not reach the
load during this time. The consequences of this can be very serious, depending on the specific features of the power consumer.
, followed by restoration of voltage to its initial or
U
nom
8
The parameters of voltage dips include the duration
p
M
f
residual voltage
U , expressed as a percentage of the nominal, and the fre-
p
t , the value of the
p
quency of voltage dips occurrence (Fig. 1.2).
The main causes of voltage dips occurrence in electrical networks are
shown in Fig. 1.3. The most common causes of voltage dips are short circuits
on networks overhead lines of the voltage110 kV and higher . Failures, in this
case, are distinguished by a sufficiently large number of affected consumers
and a low level of residual voltage. It is possible to assess the degree of their
influence on consumers, knowing their depth and duration, as well as the degree of consumer sensitivity.
Voltage dips
characteristics
(Standard 13109-97)
Depth of voltage dip
UU
nom min
U
p
U
100%
nom
Duration of voltage dip
ttt
sfp
Frequency of
voltage dips
()
mU t
F
p
p
Fig. 1.2. The voltage dips characteristics
In figure:
rms voltage values, V;
the voltage dip, s;
– rated voltage, V;
U
nom
,
tt – the initial and final moments of the time of
s
()
mU t – the number of voltage dips with depth pU
pp
– the minimum of all measured
U
min
9
and duration pt for a period of time T; M is the total number of observa-
tions.
In the case of multiphase short circuits, the depth of the voltage dips is
much greater. From this it follows that the operation of high-voltage electric
motors, sensitive to voltage dips, depends on the protection setting in 110 kV
network. If the protections are to work under the condition that if the voltage
drops on the bus bars of the power source is below
0.65U
, they are turned
nom
off without a time delay, while the duration of the voltage dip is 0.20-0.25
seconds. This does not affect the operation of high-voltage synchronous and
asynchronous motors. The protection of the minimum voltage of high-voltage
electric motors is performed with a time delay of at least 0.5 seconds, in this
regard, it does not have time to work. If the protection of 110 kV lines does
not have the necessary speed for deep voltage dips, then synchronous motors,
as a rule, come out of synchronism, and asynchronous motors can simply turn
off, which entails a stop or a failure in the production process.
Each voltage dip leads to a short-term malfunction of the technological
equipment. Different industries react in their own way to this phenomenon.
Voltage dips have a particularly tangible effect on the so-called “continuous
technological processes” in chemistry, oil refining, metallurgy and other similar industries. In contrast, for example, from the assembly line of mechanical
assembly production, which can be stopped and started again. Depending on
the type of production, protection against voltage dips must also be taken into
account.
The likelihood of a sudden power outage should be taken into account
when developing process regulations. Voltage shafts in power supply systems
cannot be excluded completely, but it is possible to minimize the damage
from their influence. This is achieved by a set of measures in the networks of
external and internal power supply. To reduce voltage dips the following can
be used:
– flywheel;
– static compensator;
– a parallel-connected synchronous motor;
– direct current converter;
– active filter;
– dynamic voltage distortion compensator;
– uninterruptible power system (UPS),
– active voltage regulator.
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