Data Acquisition System for Energy Quality Monitoring

in Decision-Making Network Nodes

SORIN DAN GRIGORESCU

Politehnica University of Bucharest

ROMANIA

sorin.grigorescu@upb.ro

COSTIN CEPISCA

Politehnica University of Bucharest

ROMANIA

costin.cepisca@upb.ro

NICOLAE JULA

Military Technical Academy of Bucharest

ROMANIA

nicolae.jula@gmail.com

NICOLAE POPOVICIU

Hyperion University of Buicjharest

ROMANIA

nicolae.popoviciu@yahoo.com

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.

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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

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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

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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.

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ISSN: 1790-5095 105 ISBN: 978-960-474-159-5