Download Report 2015

Web-based Power Quality Monitoring System
of Smart Transformer Substation RTP-34 MPEI
for engineering education.
Lev Khruslov, Mikhail Rostovikov, Vladimir Shishov
Moscow Power Engineering Institute (MPEI)
Moscow, Russia
[email protected] , [email protected]
www.magistr.tv/demo
Abstract—Fragment of an educational program on the
basis of online-monitoring of the power quality parameters
is discussed.
The future of electric power is smart grid, one of it’s main
parts is smart substation. To date, there is a decrease in
consumption of electricity in three-phase networks with
linear loads of 6-10 kV and increased consumption in
single-phase 0.4 kV networks. Because the active
introduction of power electronic equipment (TV,
computers, servers, compact fluorescent and LED bulbs,
office equipment, etc.) is the emergence of higher
harmonics in the 0.4 kV networks. Higher harmonics
cause additional energy losses in distribution transformers
and wires. These new trends require innovations in
engineering education.
On the working distribution transformer substation
7000kVA RTP-34 at Moscow Power Engineering Institute
(MPEI), there is a comprehensive system for onlinemonitoring of electric power quality parameters using
these parameters in the educational process via the
Internet. Remote access via the Internet to the actual
industrial equipment has allowed to create a
fundamentally new infrastructure of the educational
process. Monitoring system provides power quality control
and digital fault recording solutions.
At common coupling points RTP-34 measure electrical
parameters on the high side - 10kV (12 voltages, 42
currents) and low side - 0.4 kV (15 voltages, 99 currents).
The measured instantaneous values of voltages and
currents of the three phases are calculated values of the
total and active power, quality factors and other
parameters according to IEC 61000-4-30:2015 standard.
Performed spectral analysis of voltage and current
harmonics up to the fortieth. Evaluated the contribution of
individual harmonics in the level of additional losses in the
phase and neutral conductors is done by special “harmonic
calculator”. Monitoring system allows us to calculate the
additional losses in the power transformer. The
effectiveness of the active filter is discussed.
Keywords: power quality, web-based internet monitoring,
harmonic distortion, additional power losses, active
harmonic filter, smart substation.
I.
INTRODUCTION
Currently in the field of traditional electricity there are
significant changes. These changes include the active use of
power electronics, IT-technologies, increased attention to
energy saving, development of approaches to create a "smart
grid», the integration of the traditional system of power supply
of renewable energy and more. There is a mutual penetration of
new concepts in energy, information and telecommunication
technologies. It is planned to create the next generation of
energy systems - intelligent power networks.
Intellectualization of electricity poses problems:
• Creating a "smart" instrumentation and devices for
substations, providing accounting and energy management in
conjunction with non-stop monitoring and control of quality of
electric power in stationary and transient conditions.
• Develop principles for the organization of intelligent
distribution transformer substations of 10 / 0.4 kV.
• Formation of the concept and testing of fragments of
intellectual energy in the form of Micro Smart Grid on the
basis of individual power grid structures, located in a small
area around MPEI.
• Implementation of the Smart Grid concept in the
educational process.
New trends in modern electricity require innovations in
engineering education, especially in such expensive field as
laboratory practice.
In MPEI over the past 15 years are working in the direction
of energy saving and efficiency of electric power through the
introduction of elements of intellectual energy at the facilities
of Moscow. We transferred this research experience in
electrical engineering education.
Developed and produced in small series are two types of
smart meters quality control: Magistr DM-306M and Magistr430 PQ. On the basis of these devices implemented more than
20 local power systems «Micro Smart Grid», carried out a pilot
project for the creation of smart transformer station RTP-34
MPEI.
II.
FEATURES OF MODERN ELECTRICITY
In world practice, formed two trends related to total
consumption of electrical energy:
1. Reducing energy consumption in three-phase networks
at a voltage of 6-10 kV and increase the level of consumption
in single-phase networks of 0.4 kV. In USA total consumption
of electricity 0.4 kV "private and commercial sector" is 73%,
and at a voltage of 6-10 kV "industrial sector" 27% (Fig.1) [1].
generally designed for electric power linear loads, provided
that the total harmonic distortion THDi does not exceed 3-8%.
2. Active introduction of elements of power electronics in
low voltage caused a sharp increase in the current harmonics
and deterioration of electrical energy in the low voltage
network, including power transformers.
At the present time, more than 95% of the loads of 0.4 kV
networks are non-linear (fig.2).
Figure.1 Structure of energy consumption in USA
Figure 2. The increase of non-linear loads since 1960
Sources of power quality deterioration became institutions,
homes, schools, hospitals, etc., mainly because of controlled
single-phase rectifiers: compact fluorescent and LED lamps,
servers, office equipment, household appliances, switching
power supplies installed in the TV , computers etc.
It can be argued that the current nonsinusoidality in modern
low voltage is mainly determined by the imperfection of the
secondary power supply for the equipment.
Fig.3 shows the principled model with the idealized
electronic key S. Simulation analysis explains the appearance
of harmonic currents in power electronics devices with phase
control. Depending on the state of the switch S, current in the
circuit can take different forms. After Fourier analyze nonsinusoidal load current i(t) is represented as a sum of harmonic
currents F r - 1, 3, 5, 7, 9.
Figure 3. The emergence of higher harmonics at the phase control.
This same condition corresponds to the choice of elements
of internal automation: measuring current and voltage
transformers, relay protection, etc. Assessing the impact of
non-sinusoidal current transformers operating conditions can be
produced by various methods, one of which, according to [2],
is the K-factor notion load (Fig. 4).
K  factor   I h  h 2
2
(1)
To facilitate comparison of different forms of the same
current selected value of its effective value Irms = 100 A.
Despite the absence of reactive elements Fig.3 circuit
between the first harmonic of the current i1 (t) and the voltage
u (t) phase shift occurs. The shift can be a leading (capacitive),
zero (resistive) or lagging (inductive) depending on the
switching time key S.
In compact fluorescent lamps and LED lamps first
harmonic current is usually ahead of the first harmonic voltage.
In dimmer devices dimming the first harmonic current lags
behind the first harmonic voltage.
There are three methods of estimating harmonic load
content: the Crest-factor (CF), Harmonic Factor or percentage
of Total Harmonic Distortion (THDi) and K-factor. It is
known, that the transformer substation 10 / 0.4 kV, are
Figure 4. The dependence of the load capacity of the transformer
on the value of the K-factor loads.
III. WEB-BASED POWER QUALITY MONITORING SYSTEM
(WPQMS) OF TRANSFORMER SUBSTATION RTP-34 MPEI.
The aim of non-stop monitoring is information about
electrical parameters of power supply basic elements.
Measuring system consists of decentralized synchronized to
external time standard measurement tools with remote access
via the Internet to Web-technologies.
Methods of measurement of quality of electric energy in
the analyzer MAGISTR-430 PQ are going according to IEC
61000-4-30:2015 class “A” [3] and IEC 61000-4-7:2015 [4].
Based on measurements of voltages and currents on the
three phases are calculated Online Power Quality Parameters
(OPQP) (fig.5): full power, active power, power factor, and a
number of other parameters. In accordance with the standard
[3] measurement is making always for 10 cycles of
fundamental frequency, aggregation is made for intervals of 3
seconds, 10 minutes, 2 hours. For parameters OPQP the word
“online” means that the relevant parameters are provided for
the last three-second aggregation interval; parameter “PF”
means total power factor, parameter “cos(φ1)” means
displacement power factor for fundamental frequency.
WPQMS provides technical capabilities for the analysis of
voltage and current load. For these purposes the harmonic
contributions calculator (Fig.6) which makes it possible not
only to determine harmonic components and the currents on the
neutral conductor, but also to quantify the increase of the cable
losses and copper losses in the power transformer. This allows
us to estimate (and provide) ELECTROSAVINGS using filters
or power supplies with built-in power factor corrector.
WPQMS supports various data protocols: CAN, SNMP,
ModBus, LonWork etc. In addition the system can be
integrated into various devices having a data interface (energy
meters, panel meters, PLC controllers, UPS units airconditioning systems, diesel generator, etc.), which provides:
• View the measured OPQP in the form of graphs,
waveforms, spectra; preservation of information in graphic and
text files; counting the number of voltage sags, surges and
voltage pulses;
• control standard and emergency events, which are
displayed on a special screen forms single-line structural
schemes using animation and color changes;
• viewing parameters measured in real time, including
forms of voltages and currents for the three phases (waveform);
• Analysis of the harmonic structure of currents and
voltages;
• archiving (logging) of the measured parameters;
• Creation of power quality indices protocol in accordance
with Russian Standard RU GOST 32144-2013;
• count dips and voltage pulses and their representation in
the standard ANSI;
• preservation of the graphs in graphic files;
• e-mail alerts by e-mail, sms.
WPQMS is flexible, scalable, and easily integrated into
existing control systems.
Structurally complex object is a distributed decentralized
network peripheral controllers, combined or fieldbus CAN, or
through RS-232, RS-485, Ethernet, through which information
is exchanged between controllers and data servers. WPQMS
allows the connection of devices from other manufacturers
under the relevant protocols.
Figure 5. Online Power Quality Parameters (OPQP)
WPQMS is addressed to six major categories of
professionals: duty electricians; engineering staff service;
scientific and engineering staff of specialized organization that
helps in the analysis of emergency situations; managers (not
electricians) secondary and primary level; students of higher
and specialized educational institutions; researchers.
By providing non-stop monitoring of the quality of
electrical energy is proposed to use a visual representation as in
fig.5.
Online monitoring is supported by records and retention of
basic quality parameters of electricity each day in a journal.
Direct measurement and archiving OPQP correspond to the
current trend of continuous monitoring of the main parameters
of electric power, similar to the system of monitoring the
leading Russian TV and Radio centers.
Figure 6. Harmonic Contribution Calculator
Technically WPQMS allows for multi-parameter analysis
of modes of load and mains. Additional tool for monitoring
computer is the contribution of harmonics, which allows not
only to evaluate the currents in the neutral conductor, but also
to quantify the increase in cable loss and copper loss of the
power transformer. This allows you to define (and provide) the
effectiveness of power management when using active filters or
power supplies with built-in power correctors.
Fig.7 shows the screen form regime suppress current
harmonics active filter designed to reduce harmonic distortion
of the current in the cable and power transformers.
Source THDi determined by the type of real load section 2,
and is approximately 20%. Active filter reduces the level of
THDi to 2-3% (fig.8). The current in the neutral conductor
depends on the imbalance of the first harmonic and on the
presence of harmonics especially that are multiples of three.
Fig.7 data show that in the two main power elements - a
transformer and power cable between the transformer and the
filter - THDi decrease for each phase is about 7 times and the
power factor PF increase from 0.97 to 1.
OPQP are continuously stored in the archive in the form of
daily graphs of the main parameters. Archival data and the
online power quality parameters are used in the educational
process. From archival data students determine loss parameters
according to time of day, the level of current harmonics and the
transmit power level. It identifies additional power losses in the
power transformer (fig.9), cable and active filter. From
analyzing OPQP students determine the first harmonic
imbalance, the share of for different harmonics in neutral
current, assesses harmonic current compensation for active
filter (fig.6). All calculations are done for real loads at the time
of measurement. Real power and harmonics level differs each
day and doesn’t depend on professor.
Figure. 9. Active power losses in T2, MPEI RTP-34, 22.04.2015.
Figure 7. Active Filter ABB.
Fig. 9 shows the changes in active power in the power
transformer T2 during the day. Active power on the high
voltage side (PHV) and on the low voltage side (PLV) of
transformer are measured and averaged each hour from 8:00
am to 8:00 pm. Power losses are calculated as the difference
between PHV and PLV.
Educational structure "Distribution transformer substation
10 / 0.4 7000 kVA with internet access" is the development of
the Department of Electrical and Electronic devices MPEI and
is designed to prepare specialists in the fields: electrical
engineering, electric power supply, electromechanics, industrial
electronics, electrotechnology and several others [5].
Internet access to the web-resource WPQMS RTP-34 is
available free of charge and is documented on the use in the
educational process, with specific forms of application:
http://www.magistr.tv/demo
REFERENCES
[1]
[2]
Figure 8. THDi levels before and after active filter during
29.04.2015. For demonstration filter was off from 16:00 to 18:00.
IV.
CONCLUSION.
It has been found, that students who are faced with
principles of power quality have problems in understanding,
when their course does not include laboratory exercises.
WPQMS set of parameters can be considered as an additional
tool for the analysis of inpatient and emergency processes of
distributed energy systems. For example, WPQMS enables the
evaluation of real losses in power lines and power transformers
and instrument control to ensure energy efficiency.
[3]
[4]
[5]
T.Heidel, J.Kassakian, R.Schmalensee "Policy challenges and
technical opportunities on the U.S. electric grid" IEEE Power &
Energy magazine, may/june 2012, pp30-37.
ANSI/IEEE C57.110-2008. Recommended Practice to Establish
Transformer Capability when Supplying Non-Sinusoidal Load
Currents.
IEC 61000-4-30:2008. Electromagnetic compatibility (EMC) –
Part 4-30: Testing and measurement techniques – Power quality
measurement methods.
IEC 61000-4-7:2008. Electromagnetic compatibility (EMC) –
Part 4-7: Testing and measurement techniques – General guide
on harmonics and interharmonics measurement and
instrumentation, for power supply systems and equipment
connected thereto.
L.Khruslov, M.Rostovikov, V.Shishov “Web-based Power
Quality Monitoring System at RTP-34 MPEI”. Conference
“Metrology and metrology assurance 2014”, September 7-11,
2014, Sozopol, Bulgaria.