Title of Invention	METHOD OF PERFORMING A SYSTEM LEVEL TEST OF A FIRST INTELLIGENT ELECTRONIC DEVICE OF SUBSTATION AUTOMATION SYSTEM AND TEST ENVIRONMENT THEREFOR
Abstract	ABSTRACT The invention is concerned with the testing of system level functionality involving several Protection Control and Measurement (PCM) Intelligent Electronic Devices (lEDs) of a Substation Automation (SA) system for lEC 61850 compliant substations. An extensive testing of all conceivable control or protection functions/applications of an extended S A system comprising a large number of lEDs with a multitude of configurations is facilitated by simulating at least one of the lEDs in a testing device. Hence, only a limited number of lEDs are physically present as individual devices in a test environment, the behaviour of at least one further lED being simulated by a dedicated testing device with appropriate data processing means. The testing device sends network messages indicative of the behaviour of the simulated lED according to its communication and device configuration over a substation communication network to the physically present lED to be tested. The proper working of the configured lED functions, i.e. the expected correct action as triggered by the testing device, are then verified by analyzing the device's response over its analogue and digital outputs, as well as its response over the communication network. Preferably, the set-up for SA system testing is automatically detected and configured. Fig.2 ABSTRACT The invention is concerned with the testing of system level functionality involving several Protection, Control and Measurement (PCM) Intelligent Electronic Devices (lEDs) of a Substation Automation (SA) system for lEC 61850 compliant substations. An extensive testing of all conceivable control or protection functions/applications of an extended S A system comprising a large number of lEDs with a multitude of configurations is facilitated by simulating at least one of the lEDs in a testing device. Hence, only a limited number of lEDs are physically present as individual devices in a test environment, the behaviour of at least one fiirther lED being simulated by a dedicated testing device with appropriate data processing means. The testing device sends network messages indicative of the behaviour of the simulated lED according to its communication and device configuration over a substation communication network to the physically present lED to be tested. The proper working of the configured lED functions, i.e. the expected correct action as triggered by the testing device, are then verified by analyzing the device's response over its analogue and digital outputs, as well as its response over the communication network. Preferably, the set-up for SA system testing is automatically detected and configured. Fig.2

Title of Invention

METHOD OF PERFORMING A SYSTEM LEVEL TEST OF A FIRST INTELLIGENT ELECTRONIC DEVICE OF SUBSTATION AUTOMATION SYSTEM AND TEST ENVIRONMENT THEREFOR

Abstract

ABSTRACT The invention is concerned with the testing of system level functionality involving several Protection Control and Measurement (PCM) Intelligent Electronic Devices (lEDs) of a Substation Automation (SA) system for lEC 61850 compliant substations. An extensive testing of all conceivable control or protection functions/applications of an extended S A system comprising a large number of lEDs with a multitude of configurations is facilitated by simulating at least one of the lEDs in a testing device. Hence, only a limited number of lEDs are physically present as individual devices in a test environment, the behaviour of at least one further lED being simulated by a dedicated testing device with appropriate data processing means. The testing device sends network messages indicative of the behaviour of the simulated lED according to its communication and device configuration over a substation communication network to the physically present lED to be tested. The proper working of the configured lED functions, i.e. the expected correct action as triggered by the testing device, are then verified by analyzing the device's response over its analogue and digital outputs, as well as its response over the communication network. Preferably, the set-up for SA system testing is automatically detected and configured. Fig.2 ABSTRACT The invention is concerned with the testing of system level functionality involving several Protection, Control and Measurement (PCM) Intelligent Electronic Devices (lEDs) of a Substation Automation (SA) system for lEC 61850 compliant substations. An extensive testing of all conceivable control or protection functions/applications of an extended S A system comprising a large number of lEDs with a multitude of configurations is facilitated by simulating at least one of the lEDs in a testing device. Hence, only a limited number of lEDs are physically present as individual devices in a test environment, the behaviour of at least one fiirther lED being simulated by a dedicated testing device with appropriate data processing means. The testing device sends network messages indicative of the behaviour of the simulated lED according to its communication and device configuration over a substation communication network to the physically present lED to be tested. The proper working of the configured lED functions, i.e. the expected correct action as triggered by the testing device, are then verified by analyzing the device's response over its analogue and digital outputs, as well as its response over the communication network. Preferably, the set-up for SA system testing is automatically detected and configured. Fig.2

Full Text	DESCRIPTION SYSTEM LEVEL TESTING FOR SUBSTATION AUTOMATION SYSTEMS FIELD OF THE INVENTION The invention relates to the field of Substation Automation (S A) systems for substations in high and medium voltage power networks. More particularly it relates to the testing of system level functions involving two Intelligent Electronic Devices (lEDs) of the SA system. BACKGROUND OF THE INVENTION An electric power system comprises a power transmission and/or distribution network interconnecting geographically separated regions, and a plurality of substations at the nodes of the power network. The substations include equipment for transforming voltages and for switching connections between individual lines of the power network. Power generation and load flow to consumers is managed by a central Energy Management System (EMS) and/or supervised by a Supervisory Control And Data Acquisition (SCADA) system located at a Network Control Centre (NCC). Substations in high and medium voltage power networks include primary devices such as electrical cables, lines, bus bars, switches (breakers or disconnectors), power transformers and instrument transformers which are generally arranged in switch yards and/or bays. These primary devices are operated in an automated way via a Substation Automation (SA) system responsible for controlling, protecting, measuring and monitoring of substations. The SA system comprises secondary devices, so-called digital relays, interconnected in a SA communication network, and interacting with the primary devices via a process interface. These devices are generally assigned to one of three hierarchical levels, which are (a) the station level including an Operator Work Station (OWS) with a Human-Machine Interface (HMI) as well as the gateway to the Network Control Centre (NCC), (b) the bay level with its devices for protection, control and measurement, and (c) the process level comprising e.g. electronic sensors for voltage, current and gas density measurements as well as contact probes for sensing switch and transformer tap changer positions, as well as actuators controlling the drive of a switch or tap changer. At the process level, intelligent actuators may be integrated in the respective primary devices and connected to a bay unit via a serial link or an optical process bus. The bay units are connected to each other and to the devices on the station level via an inter-bay or station bus. Today's SA systems require interoperability between all substation devices independently of their manufacturer. To that effect, an internationally accepted communication standard for communication between the secondary devices of a substation has been introduced by the International Electrotechnical Committee, Geneva, under the name of lEC 61850 "communication networks and systems in substations". All lEC 61850 compliant devices connected to the SA network are called Intelligent Electronic Devices (lED). lEC 61850 defines an abstract object model for compliant substations, and a method how to access these objects over a network. This allows the substation-specific applications such as the OWS to operate with standard objects, while the actual objects in the substation may be realized differently by the lEDs of the different manufacturers. The abstract object model according to the above standard represents the SA functionality in terms of logical nodes within logical devices that are allocated to the lEDs as the physical devices. The actual communication between lEDs is handled, for non-time critical messages, via an MMS communication stack built on OSI/TCP/IP/Ethemet, or for time critical messages, via so-called Generic Object Oriented Substation Events (GOOSE) that build directly on the Ethernet link layer of the communication stack. Very time-critical signals at the process level such as trip commands and analogue vohages or currents use a simplified variant of GOOSE known as SV (Sampled Values) that also builds directly on the Ethernet link layer. As mentioned, one consequence of the aforementioned interoperability requirement is that lEDs from different suppliers may be combined into one SA system. As the lEDs are initially configured during an engineering phase, the corresponding dedicated engineering or SA configuration tools of the different suppliers, such as ABB's lET (Integrated Engineering Tool) or ABB's CAP (Configuration and Programming) Tool, have to be able to exchange information about the lEDs. To this effect, the complete SA system with all its primary devices, lEDs and communication links must be specified in a computer-readable way. This is enabled by the comprehensive XML-based Substation Configuration Language (SCL) that is part of the lEC 61850 standard. In short, the lEC 61850 SCL language provides for a standardized description of the primary devices, the secondary devices with their PCM fimctions, the communication system logical structure and the relation between lEDs and primary devices, and thus enables an automated configuration of both communication and lEDs. The SCL language is used to describe the capabilities of a particular lED or lED type in an lED Capability Description (ICD) file that lists the application fiinctions of a physical device, e.g. the implemented protection functionality. A Configured lED Description (CID) includes fiirther the communication properties of the lED, e.g. its unique IP address. A Substation Configuration Description (SCD) file in SCL language describes, for a particular substation, the primary objects, the functions implemented in each lED in terms of logical nodes, and the communication connections. The SCD file thus comprises (1) a switch yard naming and topology description, (2) an lED configuration description, (3) relations between switch yard elements and lED functions, and (4) a communication network description. Accordingly, if a particular lED is used within an SA system, an object instance of the lED type is inserted into the corresponding SCD file. The SCL language then allows specifying typical or individual values for data attributes carried by the instance and related to the particular lED, e.g. values for configuration attributes and setting parameters. The connection between the power process and the SA system is described in the SCL language by allocating or attaching logical nodes to elements of the primary equipment. Typically, a switch control logical node is attached to a switching device, whereas a measurement logical node is allocated to an instrument transformer. The semantic meaning of a function within an SA system is determined by the logical node type or class in combination with the switch yard and/or bay to which it is allocated. During a substation engineering process, the SA configuration (topology, lED configuration and communication setup) is derived from the customer requirements and stored in a project-specific SCD file. For the actual installation or commissioning, all or parts of the configuration information previously engineered needs to be transferred to the physical devices, and the lEDs themselves need to be configured properly. The different lEDs are loaded with substation-specific configuration data from the SCD file and put into operation. Furthermore, lEDs from different manufacturers might be loaded individually by their own proprietary configuration tools. Part of this process is automated but most steps still require human interaction by commissioning or test engineers. This process is error-prone. Additional sources of inconsistency between the SCD file and the actual configuration of an individual lED arise from different versions of the SCL file used, or from the fact that lEDs allow their configuration to be changed locally, i.e. on the device itself or through device-specific configuration tools. In view of the aforementioned sources of inconsistencies as well as in order to identify and possibly eliminate a number of other potential problems and deviations from the customer specific requirements, system verification and validation for any project concerning a custom-made SA system is required. Despite the fact that testing as part of all verification and validation activities cannot guarantee the absence of any error, the goal of the supplier of the S A system is to demonstrate the correct coordinated working of all parts in the most likely and important application scenarios, as well as the expected quality or performance like throughput, availability, and timely response also under high load. Basically, a substation PCM lED is tested for compliance with its requirement specification, which includes basic operation of the device and behaviour under load, in so-called type tests or Manufacturing Acceptance Tests. The device under test is typically being tested by applying analogue signals that simulate secondary current and voltage waveforms seen by the device under simulated power system conditions. In addition, status information related to primary equipment as well as other logic and control signals are transmitted to the device over a digital communication link or data network during the simulated power system fault. The apparatus or testing device for generating the mentioned analogue signals comprises an analogue signal generator, while digital signal generators simulate the operation of a circuit breaker or other pieces of equipment. Testing of PCM lEDs based on a data exchange using digital communication between the testing system and the lEDs under test, is disclosed in the patent application US 2002/0173927[JMI]. However, the operation of a particular PCM lED depends also on signals that are generated by other PCM lEDs, e.g. for the purpose of interlocking. Therefore, in order to reproduce all expected switching states, such signals likewise have to be manipulated, and a larger range of tests allowing to influence the signals generated by other lEDs, hereafter called system level tests, have been devised. In an exemplary system level test known as Factory Acceptance Test (FAT), for a particular substation project, checks are being made to verify that the correct devices are included and, among others, that the protection functions have been properly implemented. In a further system level test known as a System Verification Test, all possible device configurations that can be supported are tested for compliance with a worst case system configuration corresponding to a hypothetical substation project of maximum extension. The aforementioned system level tests are generally performed in a test environment or test laboratory, in which a number of lEDs are installed. However, due to the sheer number of lEDs necessitating an increasingly complicated test rig, and due to cost and space limitations, not all the lEDs of a particular substation are installed for a FAT, let alone the huge number of lEDs that would be needed for the largest possible substation in a system verification test. Accordingly, the extent of the test configurations, and the complexity of the abovementioned signal patterns, is limited. DESCRIPTION OF THE INVENTION It is therefore an objective of the invention to facilitate testing of system level functionality involving several Protection, Control and Measurement (PCM) Intelligent Electronic Devices (lEDs) of a Substation Automation (SA) system. This objective is achieved by a method of performing, and a test environment for, a Substation Automation (SA) system level test according to claims 1 and 6, respectively. Further preferred embodiments are evident from the dependent patent claims. According to the invention, an extensive testing of all conceivable PCM functions or applications of an extended SA system comprising a large number of lEDs with a multitude of configurations is facilitated by simulating at least one of the lEDs in a testing device. Hence, only a limited number of lEDs are physically present as individual devices in a test environment, the behaviour of at least one further lED being simulated by a dedicated testing device with appropriate data processing means. The testing device sends network messages indicative of the behaviour of the simulated lED according to its communication and device configuration over a substation communication network such as a Local Area Network (LAN) to the physically present lED imder test. The latter may be a single individual lED such as an Operator Work Station (OWS), a logging device or a communication gateway to the Network Control Centre (NCC), or it may be any one PCM device of a plurality of lEDs belonging to a particular bay of a substation to be controlled by the SA system. The proper working of the configured device functions or allocated logical nodes, i.e. the expected correct action as triggered by the testing device, are then verified by analyzing the response of the device under test over its analogue and digital outputs, as well as its response over the communication network. The invention takes advantage of the standardized description of the implemented device functions or capabilities and the standardized Substation Configuration Description (SCD) of the substation for which the SA system comprising the lEDs is intended. Accordingly, the testing device obtains all required information about the lEDs to be simulated by parsing a corresponding SCL file, reading data objects and extracting the configuration information corresponding to each lED. In a preferred embodiment of the invention, a fraction of all the lEDs of an extended SA system is physically present in a test environment, and these lEDs are detected automatically by the testing device. This is done by checking the communication network and trying to cormect to all the lEDs of the SA system, i.e. by browsing the communication network for lEDs configured according to the standard lEC 61850. Those lEDs that are referred to in the SCD file of the substation but that are not responding when called by the testing device are concluded to be missing from the test environment. Hence, by comparing the information from the SCL file (as being engineered) and the responses above, the lEDs which are engineered for the substation but which are not physically installed in the test environment are identified and subsequently can be simulated in the testing device for proper testing of the actual lEDs under test. In an advantageous variant, an Operator Work Station (OWS) that comprises a human machine interface and facilities for event recording is considered a special case of an lED, and its operation is tested by means of the testing device simulating the lEDs of the SA system to which the OWS belongs. In other words, apart from being used as a testing device for testing PCM lEDs, the OWS may itself be a device under test. By monitoring the messages generated by the OWS, event reporting as well as data and clock formats can be verified at an early stage in the engineering process, without any physical lED actually being installed for the purpose of stimulating the OWS under test. In a further preferred embodiment of the invention, test sequences or scenarios are introduced through a script language, and the testing device or simulator is able to read script files to play scenarios in an automated way, in particular without moving switches or controlling voltage generators by hand. Scripts may be triggered in response to an external event, e.g. a command or request from an OWS or a spontaneous change within an lED. Preferably, the monitored response of the device under test is compared to an expected value according to the test scenario in order to verify the correct working of the device under test. This can be done e.g. by checking the state of the OWS through its OPC interface or by measuring process signals. Since the processing power of the hardware that runs the simulator is limited, the test environment according to the invention may be advantageously refined, in particular for simulating a multitude of lEDs concurrently, by providing several testing devices as synchronized simulators. In addition, if the latter are connected independently to the SA communication network, e.g. via their dedicated Ethernet controllers connected to different switches in the network, heavy communication traffic in the substation can be generated in a more realistic manner. Likewise, problems due to one single Ethernet controller with limited capacity filtering nearest-neighbour traffic and/or generating non-realistic network traffic can be relieved as well. In a further variant of the test environment, simulated process signals are applied to the analogue and/or binary inputs of the lED under test, either directly by the testing device or simulator, or generated by an additional signal generator distant from the simulator and connected to the latter. Hence, this signal generator is not required to be compliant with the standard, and can be of a conventional type. The present invention also relates to a computer program product including computer program code means for controlling one or more processors of a testing device connected to the communication network of a Substation Automation system, and configured to execute the steps of reading a standardized description of implemented functions of an lED and sending network messages, particularly, a computer program product including a computer readable medium containing therein the computer program code means. BRIEF DESCRIPTION OF THE DRAWINGS The subject matter of the invention will be explained in more detail in the following text with reference to preferred exemplary embodiments which are illustrated in the attached drawings, in which: Fig. 1 shows an excerpt of a single line diagram of a substation, Fig.2 schematically shows a basic test arrangement, Fig. 3 schematically shows a test arrangement with two testing devices, and Fig.4 schematically shows a test arrangement with an additional process signal generator distant from the testing device. The reference symbols used in the drawings, and their meanings, are listed in summary form in the list of reference symbols. In principle, identical parts are provided with the same reference symbols in the figures. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Fig. 1 shows a single line diagram of a part or section of an exemplary substation at an assumed voltage level of e.g. 110 kV, together with some communication links and SA or secondary equipment. The model of a switch yard at single line level contains the topological respectively electrical connections between primary equipment. The substation comprises a double bus bar configuration with two bus bars 10, 10', each of them feeding two bays 11, 11' via disconnectors QBl to QB4. Each bay comprises a circuit breaker QAl, a disconnector QCl and an earthing switch QEl. The corresponding excerpt of the substation automation system depicts, in bold lines, a communication network 20 and two lEDs 21, 22, which both host logical nodes of class CSWI (switch control). Each logical node is allocated to one of the aforementioned circuit breakers QAl as indicated by the dash-dot lines in Fig. 1. Fig.2 shows a test environment or test set-up according to the invention as well as a first lED 21 under test. The latter is connected to the SA communication network 20, as are the Operator Work Station 12, the gateway to the Network Control Centre 13, and a testing device 30 with dedicated processing means. The testing device 30 simulates or emulates second lEDs 22 that are not physically present in the test environment according to an SCL description 23 of the substation (SCD) and lEDs (ICD). Testing takes place by reading a test script or sequence 31 into a script interpreter 32, passing it to a plant simulator 33 to produce a simulated plant state 34. Based thereupon, the simulated second lEDs 22 generate network messages that are transmitted over the SA communication network 20 to the first lED 21 under test. The response of the latter is monitored by an analogue or binary signal analyser 35, and evaluated in comparator 36, together with network traffic generated by the lED 21 as well as information from the simulated plant state 34, to conclude whether or not the lED 21 operates as expected. In detail, a test sequence thus starts with the testing device 30 loading the SCD and/or ICD files. Then the communication network 20 of the test environment where the lEDs Under Test (DUT) are installed is browsed for lEDs. This includes e.g. indicating an IP range (from 10.41.24.200 to 10.41.24.214) or a sub-network (10.41.24.XYZ), and sending out ping-commands. Those lEDs not responding must then be simulated. On the other hand, lEDs that appear on the communication network 20, but were not described fully or in part in the SCD file, can be integrated as real devices by the testing device 30. Fig.3 shows a test environment with two testing devices 30a, 30b, independently connected to the network 20 via dedicated Ethernet switches 24. An OWS 12, a communication gateway or telecontrol interface 13 as well as first lEDs 21 of a bay are likewise connected to the network 20 via their own switches 24. Fig.4 shows a test environment with a testing device 30 simulating various lEDs 22, connected via communication network 30 to an lED under test 21. In addition, testing device 30 is cormected, via remote control unit 41 and a tester network 40, to a remote controlled signal generator 42. The latter generates analogue signals representing current or voltage transformers, and binary signals representing sensors or status information, these simulated process signals are applied, using amplifiers 43 that are internal or external to the signal generator 42, to analogue and/or binary inputs of the lED 21 under test. The only prerequisite for an lED type to be simulated is the availability of a model for the device type indicating how much network traffic it generates and receives under which circumstances. Accordingly, legacy devices and other non-state-of-the-art equipment, gateways, telecontrol links and logging devices are likewise amenable to simulation. Ideally, the logic behind the simulated lEDs is reproduced as accurately as possible, i.e. information about primary devices is observed when preparing responses of the simulated lEDs. By way of example, switch-contact probes report "switch closed" only 30 ms after the command has been issued, hence this delay has to be reproduced by any realistic simulator as well. In addition, the same algorithms that are buih into the real lEDs are preferably implemented in the simulator. Generally, the simulator must reproduce the behaviour of a substation with millisecond response, and has to be able to perform interlocking based on topography information. Furthermore, error situations must be simulated, such as a switch not opening or closing properly, simultaneous failures of primary and secondary devices, or bus bar short circuits with several tens of switches opening concurrently. The simulator must likewise be capable of realistically reproducing stress situations by sending e.g. lO'OOO fi-ames per second to the lEDs under test, and therefore needs appropriate processing power. Preferably, the fiinctional modules according to the invention are implemented as programmed software modules or procedures, respectively; however, one skilled in the art will understand that the functional modules can be implemented fully or' partially in hardware. The computer program code of the programmed software modules is stored in a computer program product, e.g. in a computer readable medium, either in memory integrated in the testing device 30 or on a data carrier that can be inserted into the testing device 30. LIST OF DESIGNATIONS 10 busbar 11 bay 12 Operator Work Station (OWS) 13 gateway 20 communication network 21 first Intelligent Electronic Device (lED) 22 second lED 23 SCD file 24 Ethernet switch 30 testing device 31 test script 32 script interpreter 33 plant simulator 34 simulated plant state 35 signal analyser 36 comparator 40 tester network 41 remote control unit 42 remote controlled signal generator 43 amplifier PATENT CLAIMS 1. A method of performing a system level test of a first Intelligent Electronic Device (lED) (21) of a Substation Automation (SA) system, in which test a system level function of the SA system, involving the first lED (21) and a second lED (22) is tested based on network messages that are received by the first lED (21) over a communication network (20), the method comprising - connecting a testing device (30) different from the second lED (22) to the communication network (20), - reading, by the testing device (30), a standardized description of implemented device functions of the second lED (22), - sending, by the testing device (30), network messages indicative of the behaviour of the second lED (22) in accordance with said system level function over the communication network (20) to the first lED (21), and - monitoring a behaviour of the first lED (21) in response to said network messages. 2. The method according to claim 1, characterized in that it comprises - installing a fraction of a totality of the lEDs of the SA system in a test environment, - detecting, by the testing device (30), the lEDs installed in the test environment, - identifying lEDs of the S A system not installed in the test environment, and - sending, by the testing device (30), network messages indicative of the behaviour of lEDs of the SA system not installed in the test environment. 3. The method according to claim 1, characterized in that it comprises - providing an Operator Work Station (12) as the first lED under test. 4. The method according to claim 1, characterized in that it comprises - running test sequences or scenarios by the testing device (30). 5. The method according to claim 4, characterized in that it comprises - comparing the response of the first lED (21) with the test scenario. 6. A test environment for a Substation Automation (SA) system level test of a first Intelligent Electronic Device (lED) (21), in which test a system level function of a SA system involving the first lED (21) and a second lED (22) is tested based on network messages that are received by the first lED (21) over a communication network (20), the test environment comprising a first testing device (30) different from the second lED (22), connected to the communication network, capable of reading a standardized description of implemented device functions of the second lED (22) and capable of sending network messages indicative of the behaviour of the second lED (22) in accordance with said system level function over the communication network (20) to the first lED (21). 7. The test environment according to claim 6, characterized in that it comprises means for storing and executing (32) a test script (31). 8. The test environment according to claim 6, characterized in that the first lED to be tested is an Operator Work Station (12) of the SA system. 9. The test environment according to claim 6, characterized in that it comprises - a second testing device (30b) connected to the communication network (20) independently from the first testing device (30a), and capable of sending network messages indicative of a behaviour of a third lED in accordance with said system level function. 10. The test environment according to claim 6, characterized in that it comprises a remote signal generator (42) controlled by the testing device (30) and provided for applying simulated process signals to the analogue and binary inputs of the first lED (21).

Full Text

DESCRIPTION SYSTEM LEVEL TESTING FOR SUBSTATION AUTOMATION SYSTEMS
FIELD OF THE INVENTION
The invention relates to the field of Substation Automation (S A) systems for substations in high and medium voltage power networks. More particularly it relates to the testing of system level functions involving two Intelligent Electronic Devices (lEDs) of the SA system.
BACKGROUND OF THE INVENTION
An electric power system comprises a power transmission and/or distribution network interconnecting geographically separated regions, and a plurality of substations at the nodes of the power network. The substations include equipment for transforming voltages and for switching connections between individual lines of the power network. Power generation and load flow to consumers is managed by a central Energy Management System (EMS) and/or supervised by a Supervisory Control And Data Acquisition (SCADA) system located at a Network Control Centre (NCC).
Substations in high and medium voltage power networks include primary devices such as electrical cables, lines, bus bars, switches (breakers or disconnectors), power transformers and instrument transformers which are generally arranged in switch yards and/or bays. These primary devices are operated in an automated way via a Substation Automation (SA) system responsible for controlling, protecting, measuring and monitoring of substations. The SA system comprises secondary devices, so-called digital relays, interconnected in a SA communication network, and interacting with the primary devices via a process interface. These devices are generally assigned to one of three hierarchical levels, which are (a) the station level including an Operator Work Station (OWS) with a Human-Machine Interface (HMI) as well as the gateway to the Network Control Centre (NCC), (b) the bay level with its devices for protection, control and measurement, and (c) the process level comprising e.g. electronic sensors for voltage, current and gas density

measurements as well as contact probes for sensing switch and transformer tap changer positions, as well as actuators controlling the drive of a switch or tap changer. At the process level, intelligent actuators may be integrated in the respective primary devices and connected to a bay unit via a serial link or an optical process bus. The bay units are connected to each other and to the devices on the station level via an inter-bay or station bus.
Today's SA systems require interoperability between all substation devices independently of their manufacturer. To that effect, an internationally accepted communication standard for communication between the secondary devices of a substation has been introduced by the International Electrotechnical Committee, Geneva, under the name of lEC 61850 "communication networks and systems in substations". All lEC 61850 compliant devices connected to the SA network are called Intelligent Electronic Devices (lED).
lEC 61850 defines an abstract object model for compliant substations, and a method how to access these objects over a network. This allows the substation-specific applications such as the OWS to operate with standard objects, while the actual objects in the substation may be realized differently by the lEDs of the different manufacturers. The abstract object model according to the above standard represents the SA functionality in terms of logical nodes within logical devices that are allocated to the lEDs as the physical devices. The actual communication between lEDs is handled, for non-time critical messages, via an MMS communication stack built on OSI/TCP/IP/Ethemet, or for time critical messages, via so-called Generic Object Oriented Substation Events (GOOSE) that build directly on the Ethernet link layer of the communication stack. Very time-critical signals at the process level such as trip commands and analogue vohages or currents use a simplified variant of GOOSE known as SV (Sampled Values) that also builds directly on the Ethernet link layer.
As mentioned, one consequence of the aforementioned interoperability requirement is that lEDs from different suppliers may be combined into one SA system. As the lEDs are initially configured during an engineering phase, the corresponding dedicated engineering or SA configuration tools of the different suppliers, such as ABB's lET (Integrated Engineering Tool) or ABB's CAP (Configuration and Programming) Tool, have to be able to exchange information about the lEDs. To this effect, the complete SA system with all its primary devices, lEDs and communication links must be specified in a computer-readable way. This is enabled by the comprehensive XML-based Substation Configuration

Language (SCL) that is part of the lEC 61850 standard. In short, the lEC 61850 SCL language provides for a standardized description of the primary devices, the secondary devices with their PCM fimctions, the communication system logical structure and the relation between lEDs and primary devices, and thus enables an automated configuration of both communication and lEDs.
The SCL language is used to describe the capabilities of a particular lED or lED type in an lED Capability Description (ICD) file that lists the application fiinctions of a physical device, e.g. the implemented protection functionality. A Configured lED Description (CID) includes fiirther the communication properties of the lED, e.g. its unique IP address. A Substation Configuration Description (SCD) file in SCL language describes, for a particular substation, the primary objects, the functions implemented in each lED in terms of logical nodes, and the communication connections. The SCD file thus comprises (1) a switch yard naming and topology description, (2) an lED configuration description, (3) relations between switch yard elements and lED functions, and (4) a communication network description. Accordingly, if a particular lED is used within an SA system, an object instance of the lED type is inserted into the corresponding SCD file. The SCL language then allows specifying typical or individual values for data attributes carried by the instance and related to the particular lED, e.g. values for configuration attributes and setting parameters. The connection between the power process and the SA system is described in the SCL language by allocating or attaching logical nodes to elements of the primary equipment. Typically, a switch control logical node is attached to a switching device, whereas a measurement logical node is allocated to an instrument transformer. The semantic meaning of a function within an SA system is determined by the logical node type or class in combination with the switch yard and/or bay to which it is allocated.
During a substation engineering process, the SA configuration (topology, lED configuration and communication setup) is derived from the customer requirements and stored in a project-specific SCD file. For the actual installation or commissioning, all or parts of the configuration information previously engineered needs to be transferred to the physical devices, and the lEDs themselves need to be configured properly. The different lEDs are loaded with substation-specific configuration data from the SCD file and put into operation. Furthermore, lEDs from different manufacturers might be loaded individually by their own proprietary configuration tools. Part of this process is automated but most steps still require human interaction by commissioning or test engineers. This process is

error-prone. Additional sources of inconsistency between the SCD file and the actual configuration of an individual lED arise from different versions of the SCL file used, or from the fact that lEDs allow their configuration to be changed locally, i.e. on the device itself or through device-specific configuration tools.
In view of the aforementioned sources of inconsistencies as well as in order to identify and possibly eliminate a number of other potential problems and deviations from the customer specific requirements, system verification and validation for any project concerning a custom-made SA system is required. Despite the fact that testing as part of all verification and validation activities cannot guarantee the absence of any error, the goal of the supplier of the S A system is to demonstrate the correct coordinated working of all parts in the most likely and important application scenarios, as well as the expected quality or performance like throughput, availability, and timely response also under high load.
Basically, a substation PCM lED is tested for compliance with its requirement specification, which includes basic operation of the device and behaviour under load, in so-called type tests or Manufacturing Acceptance Tests. The device under test is typically being tested by applying analogue signals that simulate secondary current and voltage waveforms seen by the device under simulated power system conditions. In addition, status information related to primary equipment as well as other logic and control signals are transmitted to the device over a digital communication link or data network during the simulated power system fault. The apparatus or testing device for generating the mentioned analogue signals comprises an analogue signal generator, while digital signal generators simulate the operation of a circuit breaker or other pieces of equipment. Testing of PCM lEDs based on a data exchange using digital communication between the testing system and the lEDs under test, is disclosed in the patent application US 2002/0173927[JMI].
However, the operation of a particular PCM lED depends also on signals that are generated by other PCM lEDs, e.g. for the purpose of interlocking. Therefore, in order to reproduce all expected switching states, such signals likewise have to be manipulated, and a larger range of tests allowing to influence the signals generated by other lEDs, hereafter called system level tests, have been devised. In an exemplary system level test known as Factory Acceptance Test (FAT), for a particular substation project, checks are being made to verify that the correct devices are included and, among others, that the protection functions have been properly implemented. In a further system level test known as a System Verification Test, all possible device configurations that can be supported are

tested for compliance with a worst case system configuration corresponding to a hypothetical substation project of maximum extension. The aforementioned system level tests are generally performed in a test environment or test laboratory, in which a number of lEDs are installed. However, due to the sheer number of lEDs necessitating an increasingly complicated test rig, and due to cost and space limitations, not all the lEDs of a particular substation are installed for a FAT, let alone the huge number of lEDs that would be needed for the largest possible substation in a system verification test. Accordingly, the extent of the test configurations, and the complexity of the abovementioned signal patterns, is limited.
DESCRIPTION OF THE INVENTION
It is therefore an objective of the invention to facilitate testing of system level functionality involving several Protection, Control and Measurement (PCM) Intelligent Electronic Devices (lEDs) of a Substation Automation (SA) system. This objective is achieved by a method of performing, and a test environment for, a Substation Automation (SA) system level test according to claims 1 and 6, respectively. Further preferred embodiments are evident from the dependent patent claims.
According to the invention, an extensive testing of all conceivable PCM functions or applications of an extended SA system comprising a large number of lEDs with a multitude of configurations is facilitated by simulating at least one of the lEDs in a testing device. Hence, only a limited number of lEDs are physically present as individual devices in a test environment, the behaviour of at least one further lED being simulated by a dedicated testing device with appropriate data processing means. The testing device sends network messages indicative of the behaviour of the simulated lED according to its communication and device configuration over a substation communication network such as a Local Area Network (LAN) to the physically present lED imder test. The latter may be a single individual lED such as an Operator Work Station (OWS), a logging device or a communication gateway to the Network Control Centre (NCC), or it may be any one PCM device of a plurality of lEDs belonging to a particular bay of a substation to be controlled by the SA system. The proper working of the configured device functions or allocated logical nodes, i.e. the expected correct action as triggered by the testing device, are then verified by analyzing the response of the device under test over its analogue and digital outputs, as well as its response over the communication network.

The invention takes advantage of the standardized description of the implemented device functions or capabilities and the standardized Substation Configuration Description (SCD) of the substation for which the SA system comprising the lEDs is intended. Accordingly, the testing device obtains all required information about the lEDs to be simulated by parsing a corresponding SCL file, reading data objects and extracting the configuration information corresponding to each lED.
In a preferred embodiment of the invention, a fraction of all the lEDs of an extended SA system is physically present in a test environment, and these lEDs are detected automatically by the testing device. This is done by checking the communication network and trying to cormect to all the lEDs of the SA system, i.e. by browsing the communication network for lEDs configured according to the standard lEC 61850. Those lEDs that are referred to in the SCD file of the substation but that are not responding when called by the testing device are concluded to be missing from the test environment. Hence, by comparing the information from the SCL file (as being engineered) and the responses above, the lEDs which are engineered for the substation but which are not physically installed in the test environment are identified and subsequently can be simulated in the testing device for proper testing of the actual lEDs under test.
In an advantageous variant, an Operator Work Station (OWS) that comprises a human machine interface and facilities for event recording is considered a special case of an lED, and its operation is tested by means of the testing device simulating the lEDs of the SA system to which the OWS belongs. In other words, apart from being used as a testing device for testing PCM lEDs, the OWS may itself be a device under test. By monitoring the messages generated by the OWS, event reporting as well as data and clock formats can be verified at an early stage in the engineering process, without any physical lED actually being installed for the purpose of stimulating the OWS under test.
In a further preferred embodiment of the invention, test sequences or scenarios are introduced through a script language, and the testing device or simulator is able to read script files to play scenarios in an automated way, in particular without moving switches or controlling voltage generators by hand. Scripts may be triggered in response to an external event, e.g. a command or request from an OWS or a spontaneous change within an lED. Preferably, the monitored response of the device under test is compared to an expected value according to the test scenario in order to verify the correct working of the device

under test. This can be done e.g. by checking the state of the OWS through its OPC interface or by measuring process signals.
Since the processing power of the hardware that runs the simulator is limited, the test environment according to the invention may be advantageously refined, in particular for simulating a multitude of lEDs concurrently, by providing several testing devices as synchronized simulators. In addition, if the latter are connected independently to the SA communication network, e.g. via their dedicated Ethernet controllers connected to different switches in the network, heavy communication traffic in the substation can be generated in a more realistic manner. Likewise, problems due to one single Ethernet controller with limited capacity filtering nearest-neighbour traffic and/or generating non-realistic network traffic can be relieved as well.
In a further variant of the test environment, simulated process signals are applied to the analogue and/or binary inputs of the lED under test, either directly by the testing device or simulator, or generated by an additional signal generator distant from the simulator and connected to the latter. Hence, this signal generator is not required to be compliant with the standard, and can be of a conventional type.
The present invention also relates to a computer program product including computer program code means for controlling one or more processors of a testing device connected to the communication network of a Substation Automation system, and configured to execute the steps of reading a standardized description of implemented functions of an lED and sending network messages, particularly, a computer program product including a computer readable medium containing therein the computer program code means.
BRIEF DESCRIPTION OF THE DRAWINGS
The subject matter of the invention will be explained in more detail in the following text with reference to preferred exemplary embodiments which are illustrated in the attached drawings, in which:
Fig. 1 shows an excerpt of a single line diagram of a substation, Fig.2 schematically shows a basic test arrangement, Fig. 3 schematically shows a test arrangement with two testing devices, and Fig.4 schematically shows a test arrangement with an additional process signal generator distant from the testing device.

The reference symbols used in the drawings, and their meanings, are listed in summary form in the list of reference symbols. In principle, identical parts are provided with the same reference symbols in the figures.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Fig. 1 shows a single line diagram of a part or section of an exemplary substation at an assumed voltage level of e.g. 110 kV, together with some communication links and SA or secondary equipment. The model of a switch yard at single line level contains the topological respectively electrical connections between primary equipment. The substation comprises a double bus bar configuration with two bus bars 10, 10', each of them feeding two bays 11, 11' via disconnectors QBl to QB4. Each bay comprises a circuit breaker QAl, a disconnector QCl and an earthing switch QEl. The corresponding excerpt of the substation automation system depicts, in bold lines, a communication network 20 and two lEDs 21, 22, which both host logical nodes of class CSWI (switch control). Each logical node is allocated to one of the aforementioned circuit breakers QAl as indicated by the dash-dot lines in Fig. 1.
Fig.2 shows a test environment or test set-up according to the invention as well as a first lED 21 under test. The latter is connected to the SA communication network 20, as are the Operator Work Station 12, the gateway to the Network Control Centre 13, and a testing device 30 with dedicated processing means. The testing device 30 simulates or emulates second lEDs 22 that are not physically present in the test environment according to an SCL description 23 of the substation (SCD) and lEDs (ICD).
Testing takes place by reading a test script or sequence 31 into a script interpreter 32, passing it to a plant simulator 33 to produce a simulated plant state 34. Based thereupon, the simulated second lEDs 22 generate network messages that are transmitted over the SA communication network 20 to the first lED 21 under test. The response of the latter is monitored by an analogue or binary signal analyser 35, and evaluated in comparator 36, together with network traffic generated by the lED 21 as well as information from the simulated plant state 34, to conclude whether or not the lED 21 operates as expected.
In detail, a test sequence thus starts with the testing device 30 loading the SCD and/or ICD files. Then the communication network 20 of the test environment where the lEDs Under Test (DUT) are installed is browsed for lEDs. This includes e.g. indicating an IP range (from 10.41.24.200 to 10.41.24.214) or a sub-network (10.41.24.XYZ), and sending

out ping-commands. Those lEDs not responding must then be simulated. On the other hand, lEDs that appear on the communication network 20, but were not described fully or in part in the SCD file, can be integrated as real devices by the testing device 30.
Fig.3 shows a test environment with two testing devices 30a, 30b, independently connected to the network 20 via dedicated Ethernet switches 24. An OWS 12, a communication gateway or telecontrol interface 13 as well as first lEDs 21 of a bay are likewise connected to the network 20 via their own switches 24.
Fig.4 shows a test environment with a testing device 30 simulating various lEDs 22, connected via communication network 30 to an lED under test 21. In addition, testing device 30 is cormected, via remote control unit 41 and a tester network 40, to a remote controlled signal generator 42. The latter generates analogue signals representing current or voltage transformers, and binary signals representing sensors or status information, these simulated process signals are applied, using amplifiers 43 that are internal or external to the signal generator 42, to analogue and/or binary inputs of the lED 21 under test.
The only prerequisite for an lED type to be simulated is the availability of a model for the device type indicating how much network traffic it generates and receives under which circumstances. Accordingly, legacy devices and other non-state-of-the-art equipment, gateways, telecontrol links and logging devices are likewise amenable to simulation.
Ideally, the logic behind the simulated lEDs is reproduced as accurately as possible, i.e. information about primary devices is observed when preparing responses of the simulated lEDs. By way of example, switch-contact probes report "switch closed" only 30 ms after the command has been issued, hence this delay has to be reproduced by any realistic simulator as well. In addition, the same algorithms that are buih into the real lEDs are preferably implemented in the simulator. Generally, the simulator must reproduce the behaviour of a substation with millisecond response, and has to be able to perform interlocking based on topography information. Furthermore, error situations must be simulated, such as a switch not opening or closing properly, simultaneous failures of primary and secondary devices, or bus bar short circuits with several tens of switches opening concurrently. The simulator must likewise be capable of realistically reproducing stress situations by sending e.g. lO'OOO fi-ames per second to the lEDs under test, and therefore needs appropriate processing power.
Preferably, the fiinctional modules according to the invention are implemented as programmed software modules or procedures, respectively; however, one skilled in the art

will understand that the functional modules can be implemented fully or' partially in hardware. The computer program code of the programmed software modules is stored in a computer program product, e.g. in a computer readable medium, either in memory integrated in the testing device 30 or on a data carrier that can be inserted into the testing device 30.

LIST OF DESIGNATIONS
10 busbar
11 bay
12 Operator Work Station (OWS)
13 gateway
20 communication network
21 first Intelligent Electronic Device (lED)
22 second lED
23 SCD file
24 Ethernet switch
30 testing device
31 test script
32 script interpreter
33 plant simulator
34 simulated plant state
35 signal analyser
36 comparator
40 tester network
41 remote control unit
42 remote controlled signal generator
43 amplifier

PATENT CLAIMS
1. A method of performing a system level test of a first Intelligent Electronic Device
(lED) (21) of a Substation Automation (SA) system, in which test a system level
function of the SA system, involving the first lED (21) and a second lED (22) is tested
based on network messages that are received by the first lED (21) over a
communication network (20), the method comprising
- connecting a testing device (30) different from the second lED (22) to the
communication network (20),
- reading, by the testing device (30), a standardized description of implemented device functions of the second lED (22),
- sending, by the testing device (30), network messages indicative of the behaviour of the second lED (22) in accordance with said system level function over the communication network (20) to the first lED (21), and
- monitoring a behaviour of the first lED (21) in response to said network messages.
2. The method according to claim 1, characterized in that it comprises
- installing a fraction of a totality of the lEDs of the SA system in a test environment,
- detecting, by the testing device (30), the lEDs installed in the test environment,
- identifying lEDs of the S A system not installed in the test environment, and
- sending, by the testing device (30), network messages indicative of the behaviour of lEDs of the SA system not installed in the test environment.
3. The method according to claim 1, characterized in that it comprises
- providing an Operator Work Station (12) as the first lED under test.
4. The method according to claim 1, characterized in that it comprises
- running test sequences or scenarios by the testing device (30).
5. The method according to claim 4, characterized in that it comprises
- comparing the response of the first lED (21) with the test scenario.
6. A test environment for a Substation Automation (SA) system level test of a first
Intelligent Electronic Device (lED) (21), in which test a system level function of a SA
system involving the first lED (21) and a second lED (22) is tested based on network

messages that are received by the first lED (21) over a communication network (20), the test environment comprising
a first testing device (30) different from the second lED (22), connected to the communication network, capable of reading a standardized description of implemented device functions of the second lED (22) and capable of sending network messages indicative of the behaviour of the second lED (22) in accordance with said system level function over the communication network (20) to the first lED (21).
7. The test environment according to claim 6, characterized in that it comprises means for
storing and executing (32) a test script (31).
8. The test environment according to claim 6, characterized in that the first lED to be
tested is an Operator Work Station (12) of the SA system.
9. The test environment according to claim 6, characterized in that it comprises
- a second testing device (30b) connected to the communication network (20) independently from the first testing device (30a), and capable of sending network messages indicative of a behaviour of a third lED in accordance with said system level function.
10. The test environment according to claim 6, characterized in that it comprises a remote
signal generator (42) controlled by the testing device (30) and provided for applying
simulated process signals to the analogue and binary inputs of the first lED (21).

Documents:

http://ipindiaonline.gov.in/patentsearch/GrantedSearch/viewdoc.aspx?id=E/j0tuSSU/ZTCkt7FLdEAA==&loc=egcICQiyoj82NGgGrC5ChA==

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Patent Number

269335

Indian Patent Application Number

5716/CHENP/2008

PG Journal Number

43/2015

Publication Date

23-Oct-2015

Grant Date

16-Oct-2015

Date of Filing

23-Oct-2008

Name of Patentee

ABB RESEARCH LTD.

Applicant Address

AFFOLTERNSTRASSE 44, CH-8050 ZURICH

Inventors:

#	Inventor's Name	Inventor's Address
1	VETTER, CLAUS	LINDENWEG 3, CH-5033 BUCHS
2	MAEDA, TETSUJI	BAHNMATT 15, CH-6340 BAAR
3	KIRRMANN, HUBERT	IM RUTELI 17, CH-5405 DATTWIL
4	OBRIST, MICHAEL	MADERSTRASSE 19, CH-5400 BADEN

PCT International Classification Number

G01R31/327

PCT International Application Number

PCT/EP07/53893

PCT International Filing date

2007-04-20

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	06405173.3	2006-04-24	EUROPEAN UNION