INTEGRATION OF SCADA AND AMR SYSTEMS AS A COST- EFFECTIVE TOOL FOR GAS FLOW MANAGEMENT

Transcription

1 INTEGRATION OF SCADA AND AMR SYSTEMS AS A COST- EFFECTIVE TOOL FOR GAS FLOW MANAGEMENT Elzbieta Dzirba, Polish Oil and Gas Company, Regional Transmission Division in Warsaw Stanislaw Brzeczkowski, Polish Oil and Gas Company Dariusz Dzirba, Oil and Gas Institute 1. INTRODUCTION To provide better service to customer and to lower operating costs in increasing competitiveness in natural gas business, during last years companies all over the world show growing interest in remote gas meter reading (AMR) systems. On the XXI World Gas Conference in Nice it was said that such systems are the most dynamically developed area in gas metering. The main objectives of so deep interest in AMR systems may be grouped as follows: Economic: Decreasing costs of hardware devices compared with increasing labor costs change the boarder of effectiveness in favor of AMR systems. Growth of effectiveness of remote metering up to hundreds percent, possibility of reduction unaccounted-for gas, new value added services also course decrement of pay-off time of such systems. Safety: Minimization of repeated visits by meter readers at customer s doorstep improves property and both sides persons security, supports client s privacy. Marketing: Gas is very specific market product it is difficult to improve it s quality to attract more clients. However it is possible to improve the quality of service. The improvement of level of service increases customer s satisfaction. In open market environment supporting customer s expectations to be better served can improve the company s image. Law: European Union introduces regulations e.g. ETSI Standard to facilitate short range and low power devices to be installed without individual authorities approval. Also the new European Gas Directive, forcing introduction of TPA, will support development of remote metering accessible for different parties. One of the main problems during AMR implementations is usually data transmission method. The first systems were based on PTSN communication system, now after the evaluation process such systems are based on radio frequency and - more and more often on GSM network. In any case either existing commercial networks are used or specialized private networks are built. Both solutions have disadvantages necessity of supporting compatibility with existing network or high costs of developing private. It put the idea of usage the infrastructure and solutions especially data transmission of SCADA system in AMR systems. It is vital to stress that it is an additional functionality of SCADA despite its main role. It also allows to speculate about extremely positive economic effects of such solution. The main purpose of SCAMR system is introduction of: Global and integrated system comprising functionalities of SCADA and AMR systems on the basis of well-developed hardware, transmission and database infrastructures of SCADA. 2. TELEMETRY AND AMR SYSTEMS IN POLISH GAS INDUSTRY The Polish gas transmission system comprises about km of gas network, the distribution network is about km long; also there are 25 compressor stations, 7 underground storages, about 1700 I level and over 4000 II level pressure reduction stations. For last few years in Poland the modern Supervisory Control and Data Acquisition (SCADA) system has been implemented. SCADA infrastructure covers the hierarchical structure of gas-network management in Polish Oil and Gas Company (POGC) - from National Dispatching Centre, regional and area centres to gas stations supplying domestic area and industry clients. From functional point of view SCADA application system is build from five basic modules.

2 System for on-line information about pressures, flows, gas composition and state of valves and regulators. Process Data Archive (PDA) database used for archiving values of process data. SCADA system archive database comprises data of two types: - cycled data - constant data Both parts of historical database are interconnected thanks to their relational structure. Cycled part comprises the data from real time database stored on different time basis e.g. 5 min., hourly and daily. The internal structure of constant part of database provides a complete representation of site items ( technical parameters) and their interconnections. It also includes - what s more important information about customers for CIS (Customer Information System), billing and forecasting. This functionality is used for loading values from meteorological forecast and can be used for off-line loading data about gas consumption from gas stations where on-line telemetry is not installed. Simulation module in POGC SCADA system uses two kinds of gas network simulation. The first type is called state reconstruction and is based on data values from the past. The actual reconstructed values are calculated every 5 minutes and the results are stored in 5 min. archive in PDA. The second type of simulation - look-ahead - calculates hourly values for next 24 hours. These calculations are based on current state of gas network (values calculated during state reconstruction), forecasted off-takes and supply profiles. The off-take profiles are calculated by gas demand forecasting system, predefined values for some gas stations or values calculated in PDA on the basis of contracts and nominations. The results of look ahead simulation represent state of gas network in next 24 hours assuming no changes in network configuration (e.g. compressors switch on/off, changes of supply direction); additional what if module would also consider in calculations input information about such changes possible in future. Forecasting package forecasted values are based on hourly values of gas consumption in defined areas, measured and forecasted temperature. It forecasts gas demand for next 24 hours and up to next ten days. This system is dedicated to compute domestic gas consumption dependent on past information, kind of day and whether conditions. Dispatcher Information System (DIS) system designed to exchange information and orders between National and Regional Dispatching Centres. System is integrated with Process Data Archive to give possibility to store notices for predefined period of time. All information is grouped according to group type (e.g. message, order) and source region. Also DIS recognises automatically who is logged in on workstation during notice creation or acknowledging. All above modules are integrated. The main dispatcher s application is the module presenting on-line telemetry data. From this module the logged dispatcher can call all other functionalities e.g. access to PDA to view graphs and tables from archives, to print necessary reports. Also simulation and forecasting applications can be started from main module s screen. All the time the data exchange between real-time module, archives, simulation and forecasting packages is realised in the background. The basis of SCADA system is telecommunication network. Telecommunication infrastructure of SCADA system is very well developed and has a tree structure. Basic level is from gas measurement station to local area centres. On this level different kinds of media are used. The first implementations were based on PTSN communication system, now after the evaluation process such systems are mainly based on radio frequency and - more and more often on standard GSM or GPRS network. The choice of transmission media is often influenced by data transmission frequency varying from few minutes to one per day. Depending on quantity of transmitted data and importance of station/node in the whole gas network direct digital channels are also used. On the highest level of data transmission to National Dispatching Centre the digital channels with capacity of 64k are used. This structure is used traditionally for gas network monitoring of remote items of equipment along the gas pipelines including associated stations and so on. Basic operational information such as pressures, volumes, gas quality parameters is transmitted along described communication tree structure from simple leafs like smart gas meters, gas station - up to the root National Dispatching

3 Centre. Also some information, especially gas composition, is exchanged on the same level directly or through the common higher level. Above described applications and transmission system allows control and managing the whole gas system from small gas station used to supply domestic areas up to compressor stations on transportation gas network. Figure 1 shows the interconnections between SCADA modules in region system node. Figure 1. Data flow between SCADA modules. The AMR systems are significantly less developed on Polish gas market, among the others due to poor cost-effectiveness factor. As telemetry system is common, complex and coherent, the AMR systems are implemented only locally and in a very diverse manners. For domestic and small commercial gas consumers their gas consumption is measured by direct reading out the total on the installed meter. Only on few sites in Poland the simplest Off-Site AMR pilot systems have been implemented. The systems implemented in cooperation with Oil and Gas Institute have covered only small groups of domestic customers. They have proved that Off-Site Meter Reading Systems as partly automatic, still including human resources in metering process (the meter reader is equipped with a small data acquisition device to read gas consumption from gas meters transponders) despite their advantages, higher efficiency, are still inconvenient. Much better solution, but also very expensive, would be the fully remote consumption data transfer in Fixed Network Automatic Meter Reading systems. Individually depending on specific location and type of customers it is economically justified to gather gas meters to one data concentrator/data logger communicating still via short range and low power radio links. Here the problem has to be faced: how economically include the data loggers into wider area transmission system. Lack of effective solution is the main restrain of progress of AMR systems in Poland.

4 3. PRINCIPLES OF NEW SYSTEM CONCEPT So far the methodology put into practice for AMR and SCADA systems implementations has assumed separate and independent technological solutions for each application. So the separate onsite devices, transmission links, databases and organizational procedures have been applied for telemetry/monitoring data and billing values for industrial, commercial and even household customers. It means that the same single, real measuring value often has different virtual interpretations and thus can exists in the system as few different data points. What s more, there can be few different sources measuring devices of the same measurement. It is quite obvious as the usage of this data has been extremely different, as shown in following breakdown: Telemetry data (SCADA) Billing data for big and medium customers (AMR) Billing data for small customers (AMR) Typical frequency of data transmission Data accuracy 5 15 min. Low to medium Few days Dozen up to few dozen days Medium to high Medium to high Archive data transmission Typical devices Typical transmission media no RTU Leased lines, fibre optic, radio yes yes Flow computers, Gas meters Gas-meters Radio, GSM Radio, GSM, human resources Table 1. Selected parameters of SCADA and AMR systems. There were few essential reasons leading to separation of telemetry and billing systems on Polish gas market: 1) Organizational: different services were dealing with mentioned above data categories; there was no possibility of no-conflict, independent and synchronous access to the data. 2) Economical: simple measuring station RTU without possibility of data processing and archiving, with low a/c accuracy was much cheaper than flow computer generating real-time and archive data with good accuracy. 3) Technical: different requirements (see table 1.) led to various transmission protocols for different data categories for example telemetry protocol was not able to recover data and could hold only current data. 4) Structural: there was no suitable transmission infrastructure to combine requirements of both systems. During last few years some objective factors and activities taken on Polish gas industry have caused the above reasons to be out existence, as follows: Ad.1. As it was mentioned above, for SCADA system the powerful archive database PDA with great functionality was created. This database is geographically distributed and divided into functional blocks. Its allows to store data in three kinds of archives: every five minute, every one hour and daily. System of six PDA in Regional Dispatching Centres (RDC) and one in National Dispatching Centre (NDC) allows transmission of data with time stamps. The main source of data for PDA is telemetry system which transmits data direct from flow computers (pressures, flows) and RTU s (gas composition and states of valves and regulators) on gas stations. Another data source for PDA is simulation system. In this case PDA plays an extremely important role of data distribution platform between RDC and NDC by means of replication process - for values calculated during simulation. It is very important and useful functionality giving possibility of distribution of consumption profiles for different areas for next 24 hours. The hourly and daily values of consumption calculated in PDA on the basis of contract schedules or nomination from constant part of database can be also distributed in the same way.

5 Thanks to prepared tools for import ASCII files with pre-defined format the PDA accepts also other kind of data from external systems. This relational archive database with SQL tools allows for easy access to any stored data. Thanks to well-developed corporate network any data stored in any distributed part of PDA can be retrieved by the user also regardless of his geographical allocation. Ad.2. A quick progress of technology, techniques and electronics of measuring devices has reduced costs of hardware and thus has squeezed out from the market measuring systems with poor accuracy. It means that the economical reason of implementing telemetry and AMR systems on the basis on different devices is not valid any more. Ad.3. The research work was undertaken to develop and implement an unified transmission protocol to fulfil requirements imposed by different applications. From 1994 the work had concentrated on protocol standardisation on the basis of detailed and obligatory internal company s regulations. Among the others the important requirements were defined concerning: which online data, for how long stored archival values, also in what format, would be transmitted. In the middle of nineties the first version of this protocol, dedicated to values transmitted from flow computers was edited. Since then all flow computers newly mounted on gas stations have the new protocol called Gaz-Modem implemented. Ad.4. Due to an extremely dynamic progress of telecommunication technologies on world and Polish market the problem of transmission infrastructure is almost out of reason. As a matter of fact it has changed to new one: which - from available - technology would be economically justified. The choice is very wide: leased telephone lines, direct digital channels, standard GSM, GPRS, analogue radio, satellite links and so on. The above analysis proves the requirements, assumptions for the concept of new integrated system are met. The system was named SCAMR (SCADA + AMR). 4. INTRODUCTION TO SCAMR SYSTEM IMPLEMENTATION In the integrated structure the new definition of data point in the system is introduced. Its interpretation for RTU s, flow computers, transmission protocol and applications is wider than traditionally applied. The measurement data Ω in gas system is described by following set of parameters: where: I unique identifier P parametrisation vector w n original value w p processed value t time stamp o validity factor g data group switch Ω (I, p, w n, w p, t, o, g) The g switch informs RTU (flow computer) and logical of communication protocol that the record represents a group of data or single data point. The data groups can be nested to better reflect the hierarchical structure of the whole system. The flexibility of such data interpretation results in easier integration of AMR and SCADA systems. Of course the new definition has to be implemented on all applicable s of SCAMR system. Both systems AMR and SCADA s are integrating and penetrating each other to improve functionality and increase effectiveness in new SCAMR system. Figure 2 presents actual standard implementations of SCADA and AMR systems in logical s form. In the same manner the functional concept of new system is shown on figure 3.

6 Gas system. Hardware Hardware Transmission Transmission AMR system Monitoring SCADA system Archive Archive Application Application Figure 2. Traditionally implemented AMR and SCADA systems. Gas system Hardware Transmission SCAMR system Archive Monitoring Application Application Figure 3. Integrated SCAMR system.

7 After few years of experience and due to increasing requirements the development project on next generation of Gas-Modem protocol had been started. As a result the new protocol called Gaz- Modem 2 GM2 was introduced in 2001 posing new company s standard regulation. Since middle of 2002 this protocol is also obligatory implemented. GM2 has possibility not only of different type data acquisition but also control. Now it can be used for communication with all measurement equipment from smart gas-meters (like in AMR systems) through flow computers up to process gas chromatographs on one on-site end of the system to SCADA system on second end of telecommunication infrastructure. Though new Gas-Modem 2 protocol simplifies integration of different applications for data transmission including dispatching systems as well as customers billing systems, it still needs some modification work to be done to fulfil all requirements posed by integrated system. Integration of SCADA and AMR systems results in possibility of storing in archive database also the integrated information about consumption quantities of groups of AMR household customers. Archive database identifies the end user (application) by user login and password. Any database tool like Oracle Reports or Oracle Forms fulfils access demands without necessity of deep programming knowledge of SQL. Thanks to database open structure as long as the access is functionally (according to base structure and SQL rules ) and formally (entitled user) correct it will be accepted and realised. It gives possibility to open data market for new users in particular for AMR applications. Here the quantitative problems have to be considered significant uncontrolled growth of number of users can not be done with impunity. To not slow down the operations of the system the storage capacity and hardware parameters of database servers have to be improved. The database operations can be also optimised by better allocation of functional blocks to geographically distributed servers. AMR data concentrator/ logger New connection (e.g.radio ) Existing transmission link Existing gas station with telemetry SCADA system AMR metering points Measurements from site Figure 4. Example of SCAMR subsystem. Telecommunication infrastructure of SCADA system can be as well used for transmission of additional data from AMR systems - gas consumptions. Individually depending on specific location, group of gas meters can be gathered to one data concentrator/data logger and than they can be

8 connected via radio links to nearest telemetry SCADA point existing one, if the distance for radio is satisfying, or implemented for this special need. Of course the AMR consumption data has a different status and transmission frequency than SCADA telemetry, so the solution should not lower the effectiveness of the main SCADA data transmission. Here the new parameters describing the data in system and recognized by protocol, help to hierarchically rank the data packages. The assumptions of SCAMR allow all data in the system to be dealt with in the same uniform universal manner. The distinction is done only on the final application level (on-line monitoring, forecasting, billing etc.). Figure 4 shows an example of connection of AMR subsystem with existing part of telemetry system. 5. EXPECTED RESULTS AND CONCLUSION Independent and parallel development and implementations of SCADA and AMR systems often mean redundancy in technical resources, thus the possibility of systems integration is very important from economical point of view. Especially it will enable more dynamic development of AMR systems demanding so far very high level of initial costs. The important problems that Polish gas industry faces are: system balance accurate billing still not satisfying level of process information available on-line The wide implementation of SCAMR system will help to rank sites on gas network and group of gas consumers to include into on-line measuring system. Also it will allow wide use of specialized software packages like billing, forecasting, simulation. As a consequence the final user will be better served, more accurate billed. Generally gas composition is measured in supply points like border stations, mines, storages. Then in other points of network it is calculated using additional functionality of SCADA simulation module called gas composition tracking. Such calculations for the whole transmission network are done in National Dispatching Centre and the results are transmitted backwards to lower levels - regional centres. There the more precise calculations are performed to define gas quality for smaller areas like customer stations, supply stations for domestic areas. This is valuable knowledge that can be used in few ways. One of them is the possibility of increasing accuracy level of conversion of gas volume to energy quantity where applicable. Also for some customers usually industrial or group of households - it helps to fulfil contract conditions about gas quality. It is especially useful for areas which can be supplied from different directions changing few times per week or - in extreme conditions - per day. Different kind of data - but also very important for effective managing gas system - is detailed information about realised and forecasted gas consumptions. These two types of data are closely related to each other. Three main types of information are used by forecasting software: gas consumption and temperature in the past and forecasted parameters of temperature. Quality of forecasted temperature generally does not depend on POGC functionality. So the forecast of gas consumption with satisfied level of accuracy is possible only when mentioned above past values are as accurate as possible. There are three kinds of gas consumers: industry clients, commercial and domestic customers. Each of them has different shape of off-take characteristic and forecasting software supports the situation. Huge industry clients consumes gas on the basis of special dedicated contracts. They comprise the contract schedules which define maximal daily and hourly consumption and the way of changes. To fulfil contract conditions at each point where contracts are realised the simulation software is used on the basis of SCADA database functionality. Information about contracts is stored in constant part of PDA. It is used to compute hourly and daily values for 24 hours ahead. This is necessary and enough information for look ahead simulation. Commercial customers do not have special contracts and are supplied mostly from domestic grid. Their consumption is not strictly related to whether conditions. Due to not important influence for total volume of gas used their consumption is considered as an additional value in global trend. Domestic gas consumption creates the main part of dynamic of network s load in daily and yearly scale. In such case it is necessary to get proper characteristics of off-takes which are summarised on gas station. Domestic users are the most important for forecasting. Possibility of remote reading of their consumption gives new quality of information. Received from AMR system

9 information about past is completed and detailed. It allows to create precise profiles with very high probability of shape characteristic; this combined with on-line information about flow through supply station for the AMR area can be used for look ahead simulation and short and middle range forecasting. The results of forecasting for AMR groups on the whole gas system level can be used to verify the results from forecasting tool for households. This application software provides long term information for local distribution and global transmission network management. 6. FUTURE DEVELOPMENTS The implementations of concept of SCAMR system have started from: No-conflict connection of AMR subsystems for big and medium customers (industrial, commercial) to existing telemetry telecommunication infrastructure with relatively small system modifications Incorporation of new data to respective software applications On further stages of integration the more significant modifications will be done concerning database itself, access tools with strict safety rules. New AMR subsystems will be implemented for the other groups of customers with usage of data loggers, also functionality of on-site telemetry devices will be developed following assumptions of SCAMR system. REFERENCES 1. Bujalski, P., Brzeczkowski, S. (2002) Implementation of Simulation Software SIMONE In Polish Oil and Gas Company. Proceedings, 6th Simone Congress, Lyon. 2. Dho,V., Hensemberger,F. (2000). Quality in the billing cycle. Remote reading through radio frequency walk-by system and prepayment: technical and initial reliability results, cost vs benefit analysis, end user satisfaction. Proceedings, 21 st World Gas Conference, Nice. 3. Dzirba, D., Dzirba, E. (2001). Systemy AMR w gazownictwie. Nowoczesne Gazownictwo, Dzirba, E., Osiadacz, A. (2000). Structure of Distribution Gas Network operation System. Proceedings, 21st World Gas Conference, Nice. 5. Fasoli, L. (2000). A remote reading system for gas and water meter. Proceedings, 21 st World Gas Conference, Nice. 6. Higashino, A. (2001). Development of a two-way communication technology for a radiocontrolled meter-reading system. Proceedings, IGRC. Amsterdam. 7. Marr, C., Kler, B. (1997). Pipeline Integrity Management and Monitoring Systems. Proceedings, 3rd International Conference on SCADA Systems for the Oil and Gas Industry. 8. TELEGYR GAS MANAGEMENT SYSTEM POGC POLISH SCADA PROJECT. (1998). Statement of Work by Landis&Gyr Leit- und Fernwirktechnik Gesellschaft m.b.h.