INTEGRATED FLOW CAPACITY METERING AND ALARM MANAGEMENT SYSTEM FOR THE OPEN GAS MARKET

Transcription

1 INTEGRATED FLOW CAPACITY METERING AND ALARM MANAGEMENT SYSTEM FOR THE OPEN GAS MARKET Ing. S. Bakker, (Gastransport Serivices, P.O. box MA, Groningen, the Netherlands) 1 INTRODUCTION Introduction of new European and Dutch legislation for the gas market at the end of the last century necessitated a rethink of the tariff systems of Gastransport Services. (Wholly owned by N.V. Nederlandse Gasunie) Previously an integrated tariff system was applied for both commodity and the transport and associated services. Under the new legislation Gastransport Services had to develop a non-discriminating tariff system for transport and associated services (i.e. storage and quality conversion) only. In addition to transport distance capacity is a vital element in the design of a new tariff system. Due to the capacity component of the new tariff system it became necessary to measure the gas volume on an hourly basis or flow capacity in addition to the absolute gas volume for billing purposes. For approximately 1100 geographically spread Gas Delivery Stations (GDS), where gas is delivered to customers of Gastransport Services with in total an amount of approximately 2500 metering runs a total new system was required to automate the process of gas volume metering, registration, data acquisition, data verification, data allocation and billing. Because billing is basically performed on energy instead of volume, an additional 100 stations for gas quality metering are required similar to the gas flow capacity registration A second requirement of the gas flow capacity registration system was the requirement to monitor process alarms on Gas Delivery Stations became. For each metering run, temperature and pressure alarm sensors are installed to monitor gas supply process conditions. These signals were traditionally sent to the associated customer for any further actions. To increase the service to the customers, Gastransport Services decided to take direct responsibility of the total process of signalling, monitoring and handling of process alarms. This decision, combined with the requirements of flow capacity registration lead to a project for an integrated system of flow capacity registration, data acquisition and alarm management. 2 APPROACH OF THE PROBLEM The total project is performed conform the standard methodology of Gastransport Services for executing projects and is formally accepted as the basic process scheme for projects. The project was initiated with the study phase which is an iterative process with the purpose to get a clear description of the problem, defining basic requirements, producing alternative solutions including consequences for time and money and evaluation of results. This process involved many departments of Gastransport Services and so required close communication between all parties. As a result of the study phase the following basic functional requirements were determined for the flow capacity and gas quality registration project:

2 Primary requirements Registration of gas volume must be performed using absolute (non resetable) integrated totals or counter values on an hourly basis and logged at every full hour; Registration of gas quality must be performed using gas composition values on a 15 minutes basis and logged at every full quarter of an hour; Registration of gas flow capacity at approximately 1100 Gas Delivery Stations with approximately 2500 gas metering runs; Registration of gas quality must be performed at approximately 100 stations at strategic nodes of the pipeline grid; The custody transfer data must be stored locally at least for 2 months for customer information and traceability purposes; The availability of all custody transfer data must be at least 99%. This means that more than 99% of all custody transfer data must be processed automatically without any manual correction; The maximum period of continues data loss must not exceed 24 hours; High integrity of custody transfer data. This means that in addition to the registration of counter values and gas composition all relevant associated custody transfer alarms must be registered and logged; Logging of custody transfer data and alarms must be realised with a clock inaccuracy better than 2 seconds/day; Secondary requirements In addition to the monitoring of custody transfer alarms some process alarms must be registered and logged on each Gas Delivery Station; The maximum repair time of the logging function shall not exceed 24 hours; Before the implementation of the flow capacity registration project each customer of Gastransport Services was responsible for monitoring the process alarms at each Gas Delivery Station and, if necessary, notifying the dispatching centre of Gastransport Services which in turn must notify the operating department for any corrective action. This was because of historical reasons while this was not directly required for the operation of the gas transport network by the dispatching centre and so no communication facilities including telemetry systems were available at a Gas Delivery Station. With the introduction of the flow capacity registration project and the inevitable necessity to install equipment at each Gas Delivery Station for the registration of custody transfer data it was only a small effort to piggyback the process alarms with this data to the central head office. This enabled Gastransport Services to improve the service for their customers while process alarms can be signalled directly and real time by a central system and the response can be more adequate. In addition, process alarms can be used for the verification of the custody transfer data to avoid false custody transfer alarms due to abnormal process conditions. To ensure the availability of at least 99% of custody transfer data the following additional measures were incorporated in the system concept: For each gas flow a set of 3 integrated totals must be logged of which one is originating directly from the turbine meter and two originate from an Electronic Volume Conversion Device (EVCD) installed at each Gas Delivery Station. The integrated total from the turbine

3 meter represents volume under line conditions from the mechanical counter (LF signal) and the integrated totals from the EVCD represents volume under line conditions and volume under normalized conditions respectively and are measured using the HF signal from the turbine meter. This measure was taken to ensure that a failure of a maximum of two signals or a total failure of the EVCD does not result in the unavailability of custody transfer data. Furthermore because the three integrated totals are inter correlated, redundancy in information is available which is used to verify the integrity of the custody transfer data; The outlet pressure and outlet temperature of a Gas Delivery Station must be determined and logged independently of the EVCD in order to verify the integrity of the integrated totals. Because the integrated totals of gas volume under normalized conditions and under line conditions are logged the correction factor can be determined and compared with a correction factor based on outlet pressure and temperature. Because a primary function of a Gas Delivery Station is to control outlet pressure and temperature, independent measurements and systems were already available and therefore the setpoint values must be logged by entering it manually; In order to reduce the repair time to an absolute minimum it is required that all relevant alarms are sent immediately to a central system and subsequently to the responsible person of the operating department for any corrective actions. This involves the implementation of a central alarm management system to automate the total process of signalling an alarm at a Gas Delivery Station up to and including sending a message to the responsible person. While the operating department consists of approximately 250 employees, divided over 11 organisational area s and each employee responsible for a specific area, with a specific technical discipline and working in shifts this involves a comprehensive handling of alarms; 3 BASIC DESIGN After formal approval of the study report the project flow capacity registration moved to the basic design phase where all functional requirements were translated into an overall system architecture indicating all main systems and for each main system allocating its major functions. The results of the basic design were written down in a combined function/project specification including a tight time schedule and accurate budget price. Again because of the impact on many different departments of Gastransport Services the realisation of the function/project specification required close cooperation. Globally the following basic design decisions were made in this phase: Locally at each Gas Delivery Station a new system, CARS (Capacity Registration System), system must be installed for the registration and logging of integrated totals, custody transfer and process alarms and for a maximum of 4 metering runs. All data must be stored locally at least for 2 months, which is mainly intended for customers of Gastransport Services for information purposes. In addition this local storage facility is required to avoid any data loss due to temporary unavailability of a central system or data communication network. Only raw data is logged at CARS with no additional intelligence to reduce the risk of software changes on decentralised systems during the project. This means that all data verification, validation, resulting alarm generation, alarm messaging etc. must be performed at central systems; Locally at strategic locations (nodes), upstream the Gas Delivery Stations, of the gas pipeline grid the already existing gas chromatographs with data acquisition systems (DAS) on 100 stations must be modified for the registration and logging of gas composition including

4 associated alarms. Similar to CARS each DAS system facilitates at least 2 months storage of custody transfer data; Data acquisition of the most recent logged custody transfer data and events from both CARS and DAS must be performed once every 6 hours by a central system via data communication facilities. As a result of an availability study it was found that an interval of 6 hours for the acquisition of data is optimal considering both data communication costs and repair times. This is only valid for the alarms derived from the acquired custody transfer data at the central systems. The process alarms and custody transfer alarms from the EVCD are logged and sent immediately, real time, to the central system; For data communication a third party digital network (telecom company) is applied and the connection to the outstations must be permanent. The requirement of a permanent communication connection to a CARS or DAS station is a consequence of the 99% availability requirement of custody transfer data including the maximum gap of data loss of 24 hours so any alarm must be signalled and transferred immediately to the central system for processing; At the head office separate systems are foreseen for processing of respectively off line data (custody transfer data: integrated totals, process alarms, custody transfer alarms) and on line data (Actual integrated totals, process alarms, custody transfer alarms, flow, pressure, temperature). For the on line data a traditional SCADA system is applied for alarm handling (AMAS: Alarm Management System) including visualisation of actual values for remote diagnose while for the off line data a separate system with batch processing (Supervisory CARS) is used for the acquisition of logged custody transfer data including verification. Whenever an inconsistency or alarm condition is detected by the SCARS system for the custody transfer data an alarm is transferred to the AMAS system where after the data is transferred to systems for the billing process. The AMAS system is solely dedicated for the operating department to fully automate the real time acquisition and handling of alarms to inform the responsible employees and perform some remote diagnose. Common part of the central systems is the Front End Processor for communication with the CARS and DAS systems including monitoring of communication and time synchronisation. Billing SCARS CARS AMAS Operations CARS FEP Data communication network CARS CARS CARS CARS CARS DAS CARS DAS Figure 1 Basic design metering and alarm management system.

5 3.1 Availability In order to verify if all requirements were met after the basic design an availability study is performed with the help of an external consultancy agency. This included a FMEA (Failure Mode and Effect Analyses) for the qualitative analysis and failure tree and probability calculations for the quantitative analysis. The quantitative analysis included the availability of the custody transfer data, the probability of having more than 10 alarms per day and the probability of a data gap of more than 24 hours. The number of alarms per day and the probability of a data loss of more than 24 hours were within limits however to meet the requirement of 99% availability of custody transfer data the following recommendations as a result of this study were proposed: Each CARS system must be provided with a battery backup unit to avoid a high unavailability of a CARS system due to the high frequency of public power supply interruptions with a relative short duration. Based on this recommendation the CARS design was modified in such a way that a CARS system has an autonomy time of minimal 1 hour; Because the common mode of failure of the central systems in which case no alarms from the field can be processed a redundant hot standby central system including a redundant central data communication line must be installed to decrease the unavailability time and increase fault tolerance; Extensive diagnostic functions on all CARS, DAS and central systems to detect any system failure in an early stage are required; 3.2 Data communication Because of the 99% availability requirement of custody transfer data it was clear that all CARS and DAS systems must be connected permanently to the central system so that all process or custody transfer alarms signalled in the field or any system failures of CARS/DAS are signalled immediately at the central system and the resulting response for any corrective actions from the operating department are quickly and adequate. In parallel to the flow capacity registration project it was required to replace the existing telemetry network of analogue leased lines with a complete digitised network because the Dutch telecom company announced the end of support for analogue lines within a few years. As a result of a study for the replacement of the existing analogue telemetry network it was proposed, based on costs, availability and security, to use the public digital data communication network of the telecom company based on X.25/ISDN-D with a closed user group (CUG). Because of the similar application the project group for flow capacity registration adopted this proposal. It assumed however the use of an efficient, event driven, data communication protocol (IEC ) while the operational costs of the network depend on data amount and not on connection time. The IEC is an international data communication standard for remote control and monitoring including facilities for remote metering. Team members of both projects, telemetry and flow capacity registration, formed a new group to combine all requirements of both projects and produce an integral Protocol Implementation Document (PID) of the IEC This PID is required to fill in application dependent details of the protocol such as data communication facilities and required information objects. At that moment the IEC protocol was already implemented for some public power supply companies and because the protocol is complex with many options an external agency with experience in the electrical world was consulted because no changes of the protocol at a later stage of the project could be permitted.

6 4 DETAIL ENGINEERING After formal approval of function/project specification containing the basic design requirements and consequences for project costs and time schedule the detailed engineering phase started for the implementation of the main systems. This comprised writing system specifications, contracting of suppliers, verifying/approving technical design specifications, construction, testing, integration tests, commissioning and final acceptance. Because the technology of flow capacity registration and the new data communication facilities was non proven the implementation was divided in 3 phases to reduce risks: 1. Prototype phase; 2. Initial phase, installation of 50 stations; 3. Final phase, installation of 1050 stations; During the prototype phase in total 6 CARS stations were installed, primary to review the design of the system and secondary to evaluate the construction of CARS in the field. As a result no changes for the system design were required however to further improve safety, quality and maintainability modifications in installation procedures and material were adopted. At the end of the initial phase the primary goal was to optimise for logistics of construction and commissioning in the field because of the huge amount of stations to install CARS and hence to reduce the total realisation time of the project. This was possible because during these activities many parties were involved and a close cooperation was required. Conform the basic design the following systems were realized: Local systems, CARS and DAS on stations; Data communication network; Central system AMAS; Central system SCARS; 4.1 Local system CARS The primary function of the CARS system is to register integrated totals of gas volume. This was realised using the LF signal from the mechanical counter of the turbine meter (representing volume under line conditions) and 2 integrated total signals (volume under line conditions and volume under normalized conditions) from the Electronic Volume Conversion Device (EVCD) which in turn is connected to the HF signal of the turbine meter. In this configuration, for each run separately, 3 integrated totals are registered and logged by CARS, and because these integrated totals are inter correlated 2 failures of signals connected at CARS or a failure of the EVCD will have no influence on the availability of custody transfer data. In order to verify the custody transfer data at the central system SCARS the custody transfer alarms from the EVCD are also registered and logged by CARS including the process alarms of each separate metering run and some general station alarms. Some process alarms are used to verify the integrity of the custody transfer data but are mainly used to signal any disturbance in the process of gas delivery to inform the operating department of Gastransport Services for corrective actions, which is also valid for the general station alarms. The process alarms per metering run comprise the socalled first pressure alarm when the backup pressure controller is active, a second pressure alarm when the safety pressure valve is closed and a low temperature alarm from the heat exchanger.

7 General alarms comprise a public power supply failure and a temperature alarm from the heating boilers. Finally the custody transfer alarms comprise a general alarm, watchdog alarm and a low temperature alarm from the EVCD. Another validation of custody transfer data is performed using the setpoint values of 2 systems on each separate metering run for controlling both pressure and temperature. This is because of contractual reasons and because pressure and temperature are controlled at fixed values by independent systems this information is used to verify the conversion factor of the EVCD. An employee of the operating department manually enters the setpoint values locally in CARS for each metering run separately whenever the setpoint is adjusted. The CARS system only logs this data for transfer to the SCARS system where all the verifications are performed. Because the integrated total signal from the turbine meter and, in most cases, also the integrated total signals from the EVCD are discrete pulse signals it is required to synchronise the associated integrated totals in CARS, however this will result in logged integrated totals with a corresponding deviation. Moreover during maintenance of either the turbine meter or the EVCD the associated logged integrated totals are completely incorrect or deviate. For both cases, integrated total synchronisation and maintenance activities, an associated counter adjust procedure and counter invalid procedure is implemented in CARS for the employee of the operating department. During these procedures associated qualifier signals of the integrated totals are logged in CARS to indicate the type of integrated total correction including the integrated totals at both the beginning and the end of the procedure. This information is used for the validation process at SCARS. For data communication with the central system the international standard IEC (balanced) protocol is used via X.25. At each station an ISDN line of the public telecom company is installed including a terminal adapter (TA) for connecting a serial RS-232 line from CARS while the terminal adaptor is using the ISDN D channel for communicating via X.25 with the central system. However because the IEC protocol is designed for point-point communication special measures were required for communication over a network. Requiring that each single IEC packet is transferred in a single X.25 packet solved this and could be easily configured in the TA as a timeout parameter (100 ms) on receiving data from CARS before transferring the buffered data. The only impact on CARS is that IEC packets are transmitted with at least a 100 ms inter packet interval. ISDN-D TA Customer RS-232 IEC Gas Delivery Station Station alarms CARS EVCD Process alarms LF PCV PCV PSV PCV PCV PSV PCV PCV PSV PCV PCV PSV HF Flow control runs Figure 2 Gas volume metering system CARS

8 During the detailed design of the CARS system great effort was made to realize a high level of standardisation with only a limited number of options for flexibility. This standard solution for CARS was necessary in order to minimise the time of construction in the field because of the tight time schedule of approximately 3 years for installation of all CARS. The CARS system cabinet is designed to facilitate a maximum of 4 metering runs because this covers 98% of the actual number of installed runs at Gas Delivery Stations (5%: 1 run, 65%: 2 runs, 24%: 3 runs and 4%: 4 runs). At the remaining 2% of Gas Delivery Stations more than 4 runs are installed and so 2 CARS systems are necessary. Although all Gas Delivery Stations are similar the EVCD s however differ because of different supplier and technological generations of these systems. The old systems have a standard hardware I/O interface while new systems have a serial data communication interface, sometimes combined with a hardware I/O interface for compatibility. The hardware I/O interface was available for customers of Gastransport Services for information purposes. To cover these differences of technical infrastructure at a Gas Delivery Station in the design of CARS, the following 3 CARS variants were defined: Basic variant (B-Variant): hardware I/O interface from EVCD and hardware I/O interface to customer; Extended variant (E-Variant): hardware I/O interface from EVCD and serial data communication interface to customer; Serial variant (S-Variant): serial data communication interface from EVCD and serial data communication interface to customer; The different CARS variants were defined as separate units so it would not imply any limitation for suppliers to implement a CARS system. Some suppliers however were able to implement a single variant (BES-Variant) with options to compose a particular variant. 4.2 Local system DAS Gas Station ISDN-D TA RS-232 IEC DAS Station alarms GAS Chromatograph Customer Sample line Pipeline Figure 3 Gas quality metering system DAS It is evident that for gas transport and associated services billing Is based on energy instead of volume only, but under normal circumstances gas flow is far more dynamic than gas quality and

9 therefore gas quality measuring is performed at strategic locations (nodes) in the gas pipeline grid depending on both, variations of gas quality and annual gas volume. In most cases only one gas quality-metering system is required and is representative for multiple Gas Delivery Stations while the same gas is delivered for an entire area. At about 100 strategic locations in the pipeline network a gas quality measuring system comprising a gas chromatograph and a data acquisition system (DAS) is installed. Every 15 minutes the gas chromatograph takes a gas sample for analysis and as a result the gas composition is logged in the DAS system including all alarms and parameter changes of the gas chromatograph controller in order to verify the integrity of the custody transfer data at the SCARS system. The DAS system also performs daily calibrations and periodic or manual test gas analysis. Because there was already an installed base of DAS systems it was only necessary to modify the software for communication with the central system via the IEC protocol conform the CARS system. So data communication of both, CARS and DAS with the central system is uniform. This means that for each DAS the logged custody transfer data is obtained via file transfer of the IEC protocol with a uniform structure of serialized IEC objects where all IEC objects are unique. For the operating department the actual gas composition and alarms are also transferred via the IEC protocol for a quick and adequate response in case of malfunctions. 4.3 Data communication network It is obvious that the availability of custody transfer data depends on both, the systems involved (failure rate) and data communication facilities, so any failure or alarm at an outstation must be signalled immediately by the AMAS system to take appropriate action so that the total time of repair for an outstation (CARS, DAS) will be less than 24 hours. Therefore redundant hot standby FEP s (Front End Processor) are installed including a redundant X.25 network data link (64 kb/s). Public X.25/ISDN-D network AMAS Packet Handler Packet Handler 750 FEP FEP FEP FEP X.25 network 750 ISDN TA RS-232 IEC x TA 100 x CARS DAS Figure 4 Data communication network

10 Because of the large amount of outstations and consequently SVC s (Switched Virtual Circuit) of the X.25 network, it was necessary to distribute these data links over 2 separate redundant FEP systems since one X.25 data link can handle only a maximum of 1000 SVC s. Each separate FEP can handle a maximum of 750 (3 X.25 cards) outstations so in this configuration each separate FEP/X.25 data link has sufficient spare. The SVC s are always set up originating from the FEP and subsequently continuously monitored for any disturbances. The FEP s are communicating with the AMAS SCADA system for the online information of the operating department and with the SCARS system for the off line custody transfer data (file transfer). The IEC protocol is used for data communication between a CARS/DAS and the FEP over the X.25 data link layer which is used as a data carrier. Remark that the data link of CARS/DAS is RS-232 and a TA (Terminal Adaptor) with PAD (Packet Assembler/Disassembler) is used for transferring it over X.25. The terminal adaptor is connected to the ISDN network and data transfer is performed via the TA-PAD over the ISDN-D channel. (max. 16 kb/s) The data communication facilities are delivered as a standard service from a public telecom company specially designed for this kind of applications but, for example, are also used for financial systems and security systems. For this reason the security of data communication is guaranteed by means of a closed user group (CUG). 4.4 Central system AMAS. The central system AMAS is used for the visualisation and alarm handling of online information from CARS and DAS stations in order to provide the operating department with correct and real time data. In this manner the employees of the operational department can be informed in time of any active alarms, perform some remote diagnoses and respond adequately so total repair times are kept at a minimum and activities can be planned efficiently. In addition to process alarms and custody transfer alarms from the field, alarms from the SCARS system, as a result of the verification process, can be received and handled uniformly in AMAS Architecture The central system AMAS consists of: Redundant SCADA servers for alarm monitoring and alarm handling or also called Enhanced Alarm Processing (EAP); Redundant Alarm Communication Servers (ACS) for message services as a result of the Enhanced Alarm Processing such as sematext, SMS, semaphone, , fax etc. via the PSTN; Redundant FEP s for communication with CARS and DAS stations; Redundant LAN for intercommunication; Redundant routers connected to the Gastransport Services office network for communication with the SCARS system and employees in the field of the operating department via dial in lines;

11 Head office Office network Viewstar 750 Router Router SCADA SCADA ACS ACS SMS Sematext Fax Etc. FEP FEP FEP FEP PSTN X.25 Figure 5 Central system AMAS. For the SCADA servers a standard, on the market available, SCADA system is used with typical functionality like alarm lists, event lists, graphic process views, trending, reports etc. Main function of the SCADA system is the monitoring of alarms originating either from the field or from the SCARS and the presentation on alarm and event lists. Because the operating department is organised in 11 sub departments, responsible for geographical oriented areas, and employees have different disciplines (manager, mechanical, electrical & instrumentation) all alarms and online information is filtered accordingly for each employee. The enhanced alarm processing (EAP) is dedicated for Gastransport Services and therefore implemented on the SCADA system as a separate software module by means of database tables for flexibility reasons, and communication with the SCADA software is performed via an open API interface. Whenever an alarm is received, either from the field or SCARS this is handled in a standard way on the SCADA system and subsequently transferred to the EAP software, which generates the appropriate call up messages (based on area, discipline, time shift, priority) for the employee and sends it to the ACS for transmission. The off line data or custody transfer data from CARS/DAS is transferred via the FEP to the SCARS system on the office network for further processing. Data acquisition is started every day at 00:00, 06:00 and 12:00 hours by sending a batch command with all requested stations from the SCARS system to the FEP s where a process for file transfer is started. Because data acquisition is not time critical a maximum of 16 stations are read simultaneously and before each file transfer, the time is synchronised at the remote station and the time adjustment logged for SCARS. Any employee in the field of the operating department can login on the Gastransport Services network, after an alarm message is received, via dial in lines and subsequently login on the AMAS system to inspect the current status of an outstation where the alarm occurred and decide what actions are required. For flexibility reasons and ease of use WEB technology is used for access of a remote user on the AMAS system and therefore a WEB server is implemented on the SCADA system interfacing via the API. The following functions are available for a remote user:

12 Inspect CARS alarms, integrated totals, flow, pressure, and temperature. For each CARS station a WEB page can be requested which initiates a general interrogation and counter interrogation to the outstation and showing all alarms, measured values, statuses and alarms; Inspect DAS alarms, gas composition. Similar to a CARS station; Examine alarm lists and acknowledge alarms. When an alarm WEB page is requested by a user only alarms for his area and discipline are shown and can be acknowledged; Examine event list using data filters. Conform the alarm WEB page only relevant events are presented but the user can also apply additional data filtering to assist the user in tracing problems; Examine/modify time schedules for employees on duty. For each area/discipline one person is directly responsible for corrective actions outside normal working hours as a result of alarm messages received. Because personal of the operating department are working in shifts during non working hours a time schedule is implemented in AMAS to redirect alarm messages depending on the time schedule; Examine/modify alarm profiles for assigning priorities. For each area and discipline, alarm profiles can be configured for similar or particular alarms to assign an active alarm an alarm priority or also called alarm scheme for successive handling. An alarm scheme is used to specify which, when, what and to who messages must be sent; Set outstations in/out maintenance to avoid unnecessary alarms. This is for normal maintenance activities which may cause false alarms or alarms which cannot be solved in a short time to suppress alarm handling; Enhanced alarm processing Because of the huge amount of alarms which must be handled by the AMAS system a meachanism was required to enable an easy and flexible configuration of the alarm handling for the operating department. For example, because most of the Gas Delivery Station are identical, similar alarms can be handled in a uniform way thus resulting in the same call up messages of the same type of person while for special cases a dedicated alarm handling is required. For this purpose the Structured tag-name enhanced alarm processing module was implemented to enable the flexibility to configure the handling of groups of alarms Alarm profile based on rules or alarm profiles. Large amounts of similar alarms can be configured by means of an alarm profile to be Call up scheme handled in a uniform way resulting in the same type and number of call up s ( , semaphone, SMS etc.) and to the same kind of persons (e.g. Duty schedule Mechanical, Electrical). However, when for a specific alarm a dedicated alarm handling is required the alarm profile must be more specific.

13 The processing of alarms by the EAP module is a 4 stage process: structured tag-name: all signals of CARS/DAS/SCARS are configured on the SCADA system and identified by means of an area code and a structured tag-name based on the instrumentation coding used in the process industry. Each tag-name consists of a station identification and an instrument signal identification (e.g. W :TS021L for a temperature switch.). Alarms are transferred from the SCADA system to the EAP module using the tag-name as a key; alarm profile: for each area a list of alarm profiles is configured and for each alarm profile separately a search key comprising a priority number and a tag-name, using wildcards (*,?), must be configured. Whenever an alarm is signalled by the SCADA system, the structured tag-name is compared against the list of alarm profiles in the order of priority number, and when a matching alarm profile is found a configured call up scheme is selected; call up scheme: a call up scheme is used to define a number of messages which must be scheduled, where for each message the media ( , semaphone, SMS) and recipient, as an abstract person, must be configured. In addition attributes must be configured to determine the point in time the message must be transmitted such as: alarm delay time, if it is relative to the alarm timestamp or the time of the first message, if it must be postponed to working hours etc. The abstract person defines the type of person such as: mechanical technician, electrical technician, head office, branch office etc. to transmit the message; duty schedule: the duty schedule is used to configure for each abstract person the employee on duty depending on a time scheme. An employee is normally on duty for one week for a particular discipline. When a scheduled message, conform the call up scheme, must be transmitted the duty schedule is used to translate the abstract person to an employee; 4.5 Central system SCARS The central system SCARS is used for the acquisition of off-line custody transfer data from CARS/DAS systems including processing. The SCARS system initiates a batch job on the FEP for data transfer, comprising all requested CARS and DAS stations, three times a day (00:00, 06:00 and 12:00) and after the batch job is completed the received custody transfer data is analysed. This involves checking of logged alarms including the verification of the 3 correlated integrated totals for each run and if necessary performing corrections. Whenever an alarm is signalled this is sent directly to the AMAS system to inform a person of the operating department. Most of the data corrections are performed automatically and for only a very small amount of data a manual correction is required. In addition to data acquisition and analyses the measured data must be allocated to contracts of customers (shippers). This can be very complex because one or multiple shippers can use a single physical point of delivery in which case the total amount of measured volume (energy) must be allocated depending on nominated values and the contract.

14 5 CONCLUSION Although for flow capacity registration off-line logging of gas metering and quality data on a hourly basis would be sufficient the on line information of custody transfer data and process data combined with automatic alarm dispatching has significant benefits for: Custody transfer process. It is evident that short response times of the operating department increase the availability of the custody transfer data and is therefore significant better than 99%. In addition the integrity of custody transfer data is improved while correlated data is continuously monitored and any deviation automatically results in an alarm for the operating department; Quality of service for gas transport. For customers of Gastransport Services the reliability of gas delivery is important and so short response times in case of alarms/malfunctions are essential. In addition any alarm identified by the custody transfer process may indicate a potential problem in gas supply and so process information can be monitored to solve the problem or perform process optimizations. The availability of flow capacity data improves pipeline grid studies to identify bottlenecks of pipeline capacity on the long term; Efficiency. The availability of on line, accurate and overall information and remote diagnoses enables the operating department to improve overall response times and improve planning of activities. Follow-up WEB based real time, on-line flow capacity information service for shippers and end users; Automatic performance registration for plant maintenance; Automatic work order generation for SAP-PM; Statistical process control for preventive maintenance;