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Data Acquisition System for Energy Quality Monitoring
in Decision-Making Network Nodes
SORIN DAN GRIGORESCU
Politehnica University of Bucharest
ROMANIA
COSTIN CEPISCA
Politehnica University of Bucharest
ROMANIA
NICOLAE JULA
Military Technical Academy of Bucharest
ROMANIA
NICOLAE POPOVICIU
Hyperion University of Buicjharest
ROMANIA
Abstract: - Modern monitoring solution fitted for energy quality control consist in information technology on PC
platform, as it allows acquisition, sampling, processing, storage, graphical representation, editing, printing and dissemination by electronic means, of specific information, on the basis of modularized software packages, easily
editable according to supervised installation and with an average performance technical computing configuration.
Key-Words: - Energy parameters, power quality, monitoring equipments.
1 Introduction In Romania, Transelectrica is the Transmission System
Operator and, at the same time, the Balancing Market
and the Metering Operator of the wholesale electricity
market. Technically, the power distribution system
(SEN) work unitary, administrated by Transelectrica,
which is a state-owned company, but transport and
system services have been separated from energy production, distribution and marketing – figure 1.
The power quality (PQ) aspects are very actual and
important in this company activity at the interface with
the Distribution and Supply Operator, and with eligible
customers. All the partners have the common goal of
maintaining the PQ parameters in the points of
common coupling (PCC), within admissible limits.
The term “power quality” (PQ) is used to describe the
produced power compatibility to the electrical devices
requirements and standards. PQ is defined as the
combination of voltage and current quality. In
alternating power production and transmission
systems, only the voltage and the frequency can be
controlled.
RECENT ADVANCES in ENERGY & ENVIRONMENT
ISSN: 1790-5095 101 ISBN: 978-960-474-159-5
Fig.1. Romanian Electrical Network
The PQ conditions in PCC between transmission
power grid and eligible customers are regulated by the
Connection Notice issued by Transelectrica. In this
regulation could be established PQ parameters
admissible limits. These regulations define the quality
of service as a combination of power supply reliability,
supply quality and commercial quality, between the utility and the customers [1], [2].
In order to achieve those goals, Transelectrica has
developed [4]:
- Dedicated CT and VT measuring transformers
installed in each metering points of wholesale
electricity market.
- PQ monitoring system dedicated to the permanent
monitoring of the interface between transmission
and distribution power grid, at a voltage level of
110 kV
- PQ monitoring system dedicated to the permanent
monitoring of the interface between the
transmission power grid and the eligible customers, at voltage levels of 110kV, 220kV,
400kV.
In this special situations global information about the
whole network can be difficult to obtain and special
monitoring equipments, for power, energy and power
quality parameters measurements, are required [3].
The main scope of this paper is to presents the new data acquisition system for PQ measure in electrical
networks, based on PC platform and modularized
software packages, which will optimize the power grid
operating mode for network optimization, technical
energy losses reduction and customer satisfaction.
2 System requirements The system of data acquisition, developed by us, called
TIFPRET-DAS, is used for continuous monitoring of
electrical parameters (voltage, voltage harmonics, U%
THD, the direct, reverse and homo-polar components). The system performs a statistical calculation of
distortion level over a 24 h period, divided into 3s
intervals. Within each 3s interval all 3 tensions and 3
currents are simultaneously sampled on a period of
80ms (4 period) with a number of 20000 points/period
and the harmonic1s up to 40
th, are calculated in the 24 h
period. The system carries out a statistic based on measurements taken at 3 s, which shows that in 95% of
cases analyzed indicators do not exceed the
permissible limit (the system must be made according
to IEC 50160) [5],[6].
For measuring the indicators on the quality of curves
of tension in accordance with the Code of Technical
RET as well as CEI 50160 of the stations, subject to
analysis, it will be used a measurement system able to
track both stationary and the slow fluctuant harmonics. This monitoring system based on PC host is built in
accordance with IEC 61000-4-30 and PE 143/1994.
Fig. 2.The strategy for data acquisition, processing and
transmission to the decisional centre
Also, TIFPRET-DAS is provided with a data
transmission module on optical fiber or wireless, which
can be used in different configurations –figure 2.
DAS interface contains current transformers,
protections and resistive divisors to adapt the data acquisition system to the featured points of measure of
power stations.
The system measures the following parameters:
- Voltage: using measurement transformers for
single phase on three-phase systems with an input of
100V or 400V.
- Current: current transformers with the nominal
current of 1A or 5A.
3 System descriptions The monitoring system TIFPRET-DAS is composed of the following functional blocks –figure 3:
- conditioning and protection block -
conditioning and protection electrical quantities of
input, which is intended to allow electrical
connections in measuring circuits of the plant
monitored, to parameterize values in accordance with
the constructive denominations of the analog
acquisition card and to protect the inputs for all
RECENT ADVANCES in ENERGY & ENVIRONMENT
ISSN: 1790-5095 102 ISBN: 978-960-474-159-5
perturbations led buy over voltages and currents that
spread on realized galvanic bonds; to this interface can
be connected simultaneously, in differential assembly,
3 voltage circuits and 3 current circuits to eliminate
any perturbations driven over the examined signals; - DAS analog acquisition system - providing
signal sampling, analog to digital conversion and
primary signal processing and storage, making data
available to the communication and further processing
system.
Fig. 3. Data acquisition equipment TIFPRET-DAS.
- communication interface – providing data
exchange with the host computer and also between the
host computer an the dispatcher of the energy
distribution.
The main constructive features acquisition system is: - analog entries: 6 asymmetric
- input resolution: 16 bits
- The maximum sampling rate for all channels:
6400 samples / s
- Three phase voltage up to 400V and current up
to 5A
- IBM-PC host computer has the role of numerical processing the input data according
to our purpose, in this case the measuring of
quality indicators of electric voltage.
- BUS: RS232 or RS485 with galvanic
separation, fiber optic and GSM adapters.
- the software is represented by a package of
programs specially designed for harmonic and
symmetric analysis, under the LabVIEW -
Virtual Laboratory Instrument Engineering
Workbench - graphical programming, version
6.1, carried out by National Instruments.
Communications subsystem provides and manages the
acquisition and data processing subsystem
communication with beneficiaries connected on the
network, if the communication is done via Internet
using VPN. The communication was thought to work
in two variants, in public and private system, using
access codes to have a level of data security –figure 4
and figure 5.
Fig. 4. The communications subsystem with wire and optic
fiber data transmission capability.
The software module of the subsystem –figure 6 -is installed on that computer which equips the acquisition
subsystem ensuring both the communication protocol
between it and fiber network and communication
protocol between it and the Internet through GSM
system. For communicating via the GSM system, data
is transmitted via USB converter - RS 232 to GPRS
modem, which transmits further, through the antenna,
to the GSM system which will provide connectivity to
the Internet.
The laboratory simulation on the system gave very
good results, both regarding the operation of its own
and the protection involved. There were also ran
laboratory simulations to verify the possibilities of data
transmission of this subsystem and the results were
positive. The system works well on the protocols of
serial data transmission, which allows connection to
the DAS TIFPRET and make it operational for the data
acquisition [5], [6].
Fig.5. Motherboard acquisition and data transmission system
- the front
RECENT ADVANCES in ENERGY & ENVIRONMENT
ISSN: 1790-5095 103 ISBN: 978-960-474-159-5
Fig. 6. The main window of TIFPRET-DAS
The subsystem ensures communication both in a
situation in which optical fiber network of the client is
directly accessible and the situation in which the network is not accessible to the location where to
install the acquisition and data processing subsystem
[7].
Once one is logged on application’s on-line database,
the client module to be installed can provide
information on multiple state parameters of the system (figure 7): three-phase voltages and currents, factors
THD type etc.
Fig.7. Application Window for measurements TIFPRET-
Client view
Fig.8. Global Showcase window and filling the database
4 Conclusions Using several signal monitors in a high voltage stations spread on the net, in a distributed measurement
application with a client-server protocol, system allows
monitoring and alarm state in a real time decision-
making level of RET, reducing the risks in case of
critical and dangerous situations. The way the data is
packed allows making decisions in a pyramidal
hierarchy, very important when these decisions may
affect operation safety of RET. The system allows a
flexible development, which can be implemented in the
future on related network stations of main electricity
distribution network. Connecting the monitoring
system with the optical fiber safe communication
property of RET, or traditional wire opening of a database replica on client computer that contains
desired, as depicted in Figure 8. Acquired data may be saved in a real time database for
ulterior processing; the program allows the GSM, and
the communication subsystem of TIFPRET DAS
allows installation in any decision-making node of
RET, contributing to a better knowledge of exploitation parameters of any electrical network
integrated in the SCADA system of RET.
R e f e r e n c e s
[1] ANRE, Romania 2007, The Electricity
Transmission Grid – Standard of performance,
www.anre.ro
[2] ANRE, Romania, 2007, The Electricity
Distribution Grid – Standard of performance,
www.anre.ro
[3] Barbu, I., Sisteme descentralizate de urmărire,
control şi achizitii de date, Revista de Măsurări şi
Automatizări nr.4/2004
[4] C. Stanescu, J. Widmer and C. Pispiris, Power
RECENT ADVANCES in ENERGY & ENVIRONMENT
ISSN: 1790-5095 104 ISBN: 978-960-474-159-5
Quality Permanent Monitoring Systems in
Romania, Foren 2008
[5] A. Broshy, Monitoring Power Quality beyond EN
50160 and IEC 61000-4-30”, EERG Revue,
February 2008 [6] Schlabbach, D. Blume, T. Stephanblome, and M.
Daly J.,Voltage Quality in Electrical Power
Systems, IEEE Power & Energy Transaction
Series, vol. 36- 1/2006
[7] *** European Commission Report http:
//ec.europa.eu/health/ph_risk/committees/04_scenihr/d
ocs
[8] Dimitris Al. Katsaprakakis, Dimitris G. Christakis,
Arthouros Zervos, and Spiros Voutsinas, A PQ
measure, IEEE Transactions on Power Delivery,
vol.
23, no. 2, april 2008,pp.553
[9] John DeDad, Flicker: Causes, Symptoms, and Cures,
EC&M Revue No.1/2007 Penton Media, Inc.
[10] A. Ferrero, M. Lazzaroni, and S. Salicone, A
calibration procedure for a digital instrument for power quality measurement, IEEE Trans.
Instrum.Meas., vol. 51, pp. 716–722, Aug. 2002
[11] N. C. Ferguson, Power quality improvement in a
harmonic environment, International Electrical
Testing Association (Neta) Annual Technical
Conference,
March 19, 2002, St. Louis, USA.
RECENT ADVANCES in ENERGY & ENVIRONMENT
ISSN: 1790-5095 105 ISBN: 978-960-474-159-5