Computer based data acquisition system for EMC experimentation initalian Railways F. Cipollone, E. Fedeli & A. Fumi Ferrovie dello Stato S.p.A., Divisione Infrastruttura, Italy. Abstract New electrical and electronic technological applications in power supply and signalling railway systems will result in the dramatic increase, in the near future, of electromagnetic complexity of the whole infrastructure and vehicle environment. Thus, preliminary studies of the compatibility of new technologies with the pre-existing installations have become more and more important from both a technical and economical point of view. For this reason, during the last year, FS S.p.A. has set up a field test measurement campaign to study EMC problems related to interaction between 25 kv - 50 Hz power supply system, adopted in the new high speed lines of Italian Railways, and the traditional railway network supplied with 3 kv dc, particularly in the cases of interconnection or close proximity of the two types of infrastructure. To achieve the expected goals of such experimentation, FS S.p.A. developed a computer data acquisition system based on commercial hardware and open software platform able to satisfy the necessary flexibility, modularity, reusability and user-friendliness requirements. In this paper the following topics will be discussed: - railway infrastructure field test description; - test procedures; - computer based data acquisition system; - test results evaluation. In particular, the hardware and software architecture of the system will be presented, the main advantages of the specific technical solution will be highlighted and the possible future evolution of the system will be indicated.
346 Computers in Railways VII 1 Introduction The 25 kv 50 Hz power supply system, adopted by Italian Railways for the next future high speed lines, requires a particular attention to the electromagnetic compatibility problems. Such matter potentially involves all electric and electronic systems interfering with electromagnetic fields produced by the new power supply system, particularly in the case of interconnection or close proximity of traditional railway lines, where considerable interaction phenomena with the operating signalling and telecommunication systems could occur. 2 The test site fixed installations The experimentation this paper deals with, was set up on the railway line Roma- Firenze in the site, about 18.5 km long, delimited by the stations of Chiusi (km 164+208) and Terontola (km 192+738). The selected site matches all the main requirements needed from both technical and functional (traffic, time table, etc.) point of view and it is very representative of a typical double track traditional installation of Italian railway infrastructure. The stretch from Chiusi to Terontola is a double track line coded current automatic block (BACC) signalling system equipped, almost rectilinear, with bending radius greater than 1000 m and maximum slope lower than 3 %Q 2.1 Power supply system The power supply system adopted in the normal service on the above mentioned Chiusi-Terontola stretch provides a 3 kv dc voltage by mean of two transformation and rectification electrical substations in Chiusi and Camucia (km 199+093), both equipped with two 3.6 MVA three-phase transformers [1]. The catenary is constituted by four parallel connected conductors: two copper tensioned carrying cables of 120 mm^ cross-section and 0.15 Q/km resistance/km and two copper tensioned contact cables of 100 mnr* cross-section and 0.18 Q/km resistance/km. The overhead line masts are grounded and the protection circuit is composed of "cells" 3 km long, formed by two aluminium wires of 125 mm^ cross-section and 0.23 Q/km resistance/km for each track, directly connected to the masts and, by means of overvoltage protections, to the return current circuit too. The rail features are according to the standard UNI 60 with 0.15 Q/km resistance/km at 50 Hz frequency. The infrastructure cross-section of the experimentation site is sketched in figure 1. 2.2 Signalling systems The Chiusi-Terontola line is operating with a coded current automatic block signalling system (BACC), installed in 1995, based on static balanced transmission and reception devices.
Computers in Railways VII 347 ground wires Figure 1: Chiusi-Terontola infrastructure cross-section The BACC system provides train protection by "block sections", 12504-2000 m long, based on insulated double rail track circuiting to detect trains presence within the block sections. The Chiusi-Terontola stretch includes two intermediate stations (Panicale and Castiglion del Lago), whose auxiliary tracks are equipped with single rail track circuit systems. Other possible targets of electromagnetic interference inside station area are all the cables, hundreds meters long, for interconnections of field signalling apparatuses. 2.3 Telecommunication system The cables for telecommunication applications installed along the stretch Chiusi- Terontola are the following: 46 pairs aluminium shielded cable; 41 pairs (+ 1 coax) lead shielded cable. The main applications running on the above mentioned telecommunication cables are: real-time train traffic supervision and control, remote stations and substations control, dedicated and switched telephone services, data transmission.
348 Computers in Railways Vll 3 The electromagnetic interference source The configuration of power supply system in the stretch Chiusi-Terontola was modified to simulate the case of close proximity of two railway infrastructures, thefirstpowered at 3 kv dc (traditional line) and the second at 25 kv 50 Hz (high speed line). While a track of the line was operating as usual at 3 kv dc, the other one was temporary fed at 25 kv 50Hz by a mobile substation installed in Castiglion del Lago, equipped with a 10 MVA single-phase transformer at 132kV/25kV. The configuration obtained in this manner is a worse case than the realistic one because, in the real case of the future new high speed lines, there will be a balanced transmission of power supply (2 x 25 kv), feeding the contact line at +25 kv and the insulated return conductor (feeder) at -25kV with autotransformers at ± 25 kv distributed all along the line. In this configuration, the decay rate of railway cross-section component of total electric and magnetic field intensity is greater than the case of simple single-phase +25kV configuration [2] obtained on the experimentation site. 4 Field tests The 25 kv field test campaign was developed in 1999 during a traffic restriction program, that allows to make available the infrastructure included between Castiglion del Lago and Panicale in order to prepare the measuring system, to set the test configurations and to perform the measures. The test were carried out feeding the even track catenary at 25 kv-50 Hz between Panicale and Castiglion del Lago to allow a run test sequence, using a train equipped with two E402B loco and four coach (see picture la). 4.1 Power supply system The power for the test runs was obtained from a mobile electric feeder substation placed in Castiglion del Lago (see picture Ib), connected with 132 kv line derived from high voltage railway network. Picture 1: a) 402B train test run b): 25 kv mobile electric substation
Computers in Railways 111 349 Thus, during the test, this substation was feeding at 25 kv the catenary of the even track included between Panicale (km 174+950) and Castiglion del Lago (km 183+240), while the return circuit for the traction current was mainly assured by the rails of the same track and the ground wires of the protection earth circuit (PE) included in the same stretch. 4.2 Test configurations During the test, in order to make evidence on existing relationships between circuit topology and disturbance values, have been foreseen the permanent bonds between the protection earth circuit and the rails of the even track. In that way the return traction current passed trough the rails and the protection earth conductors similar to the system that will be adopted in the new Italian high speed lines. The even track signalling equipment have been disconnected to protect them from possible risks due to flowing of high alternative current through the rails. Also for the disturbed circuits, several different configurations and particular work conditions have been planned. The odd track return current circuits have been connected or disconnected at boundary of test site. The different test configurations are reported in table 1. Table 1: Test configurations Test code DIN1 DIN2 DIC1 DIC2 DCN1 DCN2 SIN1 SIN2 N 719 TC configuration Single rail Single rail Odd return current circuit at boundaries Connected Connected Odd catenary power condition and short circuited at boundaries and short circuited at boundaries Odd protection earth circuit to rail Connected to rail to rail Connected to rail to rail Connected to rail to rail Connected to rail 4.3 Measurements system The measurements activities involved four different locations throughout the line between Panicale and Castiglion del Lago. The measuring arrangements are shown schematically in figure 2. At each measuring location grounding rods were installed at 60m from the track, and they were used as reference electrodes for measurement rail to earth voltage.
Location 1 (km 178 + 511) 2) Inner rait current (TC 716) 5) PE circuit current Location 2 (kn 180+291) 1) Outer rail current (TC 718) 3) Outer rail current (TC 720) 4) Inner rail current (TC 720) 5) PE circuit current ^ Location 3 (kn 181 + 660) 3) Rail to earth voltage Location 4 (kn IE 1) Catenary current 4) Current between ESS PT80 M7B PT74 (ZH> 0 0 ~ * Is Is : 4%; 2S fc «j - i 1 «p CASTIGLIDN DEL Hi H IT. 1 n r u r. CzT?) ^ (Tig) ^ (Tgj) ^ @ ^ ( } ^ 0) (n> i ^ ^ ;?it)f. m. H\i 1 11 M9 PT7 PT1 LS47 LS45 M77 PT73 M71 M67 Location 1 (kn 178 + 511) 7) Outer rail current (TC 717) 9) Outer rail current (TC 719) 10) Inner rail current (TC 719) 11) Rail to rail voltage (TC 717) 12) Rail to rail voltage (TC 719) 13) Rail to earth voltage 14) PE circuit current 15) Conductor to earth voltage Location 2 (kn 180 + 291) 9) Outer rail current (TC 721) 12) Rail to rail voltage (TC 721) 13) Rail to earth voltage 14) PE circuit current 16) Track circuit relay voltage Location 3 (kn 181 + 660) 4 Inpedenc bound current 5 PE circui current 6 Rail to il voltage (TC 721) 7 Rail to r il voltage (TC 50) 8 Rail to e rth voltage Location 4 (kn 182 + E Telecommunications 4) Sheath to earth"vo% Figure 2: Schematics of test field measurements
Computers in Railways VII ^ri Before starting test campaign, in order to evaluate conductive parameters that can influence galvanic coupling, earth resistivity measurement was performed. The results reported various values of earth resistivity in the range 30 to 60 Q/m. Moreover, the rail to earth conductance and the protection earth circuit (PE) to earth conductance was estimated. The results of these preliminary measurements reported, for the conductance between each rail and the ground, a value of 0,01 S/km and, for the conductance between protection earth circuit and the ground, a value of 1,3 S/km. 5 Data acquisition system The measurements were performed by a computer based distributed data acquisition system, installed in the four field test measurement locations. The general architecture of the local data acquisition system is shown in picture 2. Picture 2: Local data acquisition system architecture The main hardware components of data acquisition systems were: - standard notebook PC (Pentium II 350 MHz, RAM 64 MB, HD 4GB); PCMCIA card data acquisition hardware (250 KS/s, 12 bit resolution); conditioning unit (8 channels, filtering, synchronisation function); current transducers (Hall effect, opto-isolated, 1kHz bandwidth); voltage transducers (opto-isolated, 1kHz bandwidth). 5.1 Software application The software application for all the implemented data acquisition and elaboration functions was completely developed by FS technicians within LabView virtual instrumentation development environment.
352 Computers in Railways VII The main benefits of this choice were: developing time reduction; software flexibility and modularity; overall cost reduction; software reusability. This development environment provides an object oriented graphical interface, allowing a completely visual programming, by mean of simply definition and interconnection of standard objects available in the system libraries (see figure 3). Figure 3: Example of development environment graphical interface Moreover, virtual instrumentation based solution allowed to develop user friendly software MMI (Man-Machine Interface) so that the management of the whole data acquisition system, during the field test campaign, didn't require highly specialised personnel. An example of application MMI is shown in figure 4. Synchronisation of data acquisition systems, distributed in four different locations all along the field test stretch, was obtained connecting all the systems by mean of a copper conductor pair in a multipoint line configuration. Using this connection, the master station sent a synchronisation signal to the slave stations to enable/disable acquisition task, driving in this way the whole distributed data acquisition process.
Computers in Railways VII Indirizzo del datt [Vclg] 353 Anomalietcoiiente 250 A ate 13:25:16 a»sorbi<a 280-290 402 dalfo Vari«:partenza 13:25:35 aua tteno. 13:27:00 p4**asgiolg..13 25:50 13:24:32 pat»aggk)l5. L4.13:27:20 13:26:44 Figure 4: Data acquisition system MMI 5.2 Conditioning unit and signal transducers The conditioning units were specifically developed by F.S. technicians from electronic laboratories in Florence to achieve specific amplification, isolation and filtering functions not easily obtainable with on-the-shelf products (see picture 3a). To measure the rail current, transducers, based on Hall effect element, were installed around the conductors connected to impedence bounds (see picture 3b). Similar transducers were used to evaluate the current in the ground wires. Picture 3: a) PC and conditioning unit b) current transducers
354 Computers in Railways VII 5.3 Post-elaboration analysis At the end of each field test session, the data recorded by the data acquisition systems were transferred to the back-office post elaboration computers for the off-line data analysis and correlation activities. During the complete campaign period, nearly 20 GByte of data were acquired and stored and a great amount of data charts and tables was produced. In the figure 5 typical output plots are reported. TC 717 Distorted outerrailcoded current (A) TC 717 Normal operating outer rail coded current (A) Figure 5: Examples of output plots 5.4 System evolution The system is going to be upgraded with a GPS master clock and GSM interconnection network to manage synchronisation with other external data acquisition system (e.g. installed on test train) in order to correlate the simultaneous measurements/events captured during the future field test campaign. 6 Test results The authors reported an exhaustive overview of measurement results in a previous paper [3]. The most significant values were in depth investigated and analysed, particularly the track circuit rail to rail voltage, that is the most relevant parameter for the signalling systems, for which were obtained critical values for the system functionality. As example, in figure 6 are reported the values of rail to rail voltage for different configurations that point out that the measured disturbance levels are comparable with the operational working voltage of double rail track circuit (2-2.5 V).
Computers in Railways VII 355 TC 719 rail to rail voltage (V) DIN1 DIN2 DIC1 DIC2 DCN1 DCN2 Figure 6: Chart of normalised measurements values 7 Conclusions The field test environment, arranged in the Terontola - Chiusi stretch, allowed to verify the electromagnetic interference phenomena occurring in the cases of railway infrastructures close proximity with different power supplies (25 kv 50 Hz and 3 kv dc). The test results pointed out critical values for signalling systems operation that could determine a service regularity detriment. Computer-based data acquisition system provided excellent performances and allowed to obtain the expected targets. The final results constituted an useful input for electromagnetic coupling numerical simulation models and a meaningfully contribution in development of technical solutions to increase the electromagnetic immunity of signalling systems, in the cases where traditional lines will be interfered by the future high speed lines. The same results also provided experimental contribution to the ESCARV European project (Electrical System Compatibility for Advanced Rail Vehicles) in which Italian Railways is participating. References [1] A. Fumi: "La Gestione degli Impianti Elettrici Ferroviari", Ed. CIFI; [2] V. Morelli: "Sistemi di trazione a 25 kv", La Tecnica Professional, n 4, 1993; [3] F. Cipollone, E. Fedeli, A. Fumi: "EMC experimentation in Italian Railways on interference between AC and DC supply systems" - Alternate traction technologies conference - Johannesburg (SA) 11-14 April 2000.