TECHNICAL FIELD

The present disclosure generally relates to communication between substations, and in particular to transmission and reception of packets in substation networks.

BACKGROUND

A substation is typically a part of an electrical generation, transmission, and distribution system. In general terms, substations transform voltage from high to low, or the reverse, and/or perform any of several other functions associated with the electrical generation, transmission, and distribution system. Electric power may flow through several substations between the power generating plant and the consumer, and its voltage may change in several steps. IEC 61850 is a collection of standards for the design of electrical

substation automation. In short, the standards define how to describe the devices in an electrical substation and how to information is exchanged between these devices at configuration time as well as at run-time. The IEC 61850 standards define strict rules for realizing interoperability between functions as well as devices used for protection, monitoring, control and automation in substations, independent of the vendor. Interoperability means the capability of two or more intelligent electronic devices (IEDs) from one or several vendors to exchange information and to use it in performing their functions and for correct co-operation. This feature together with the possibility of free allocation of functions paves the way for a vast range of possible solutions for Protection and Substation Automation (SA) systems.

As IEC 61850 covers all communication needs within a substation, it also defines the communication to and from the process level, especially the transporting of samples ("process bus"). IEC 61850 is a part of the International Electrotechnical

Commission's (IEC) Technical Committee 57 (TC57) reference architecture for electric power systems. The abstract data models defined in IEC 61850 can be mapped to a number of protocols. Current mappings in the standard are to MMS (Manufacturing Message Specification), GOOSE (Generic Object Oriented Substation Events), SMV (Sampled Measured Values), and soon to Web Services. These protocols can run over TCP/IP (Transmission Control Protocol / Internet protocol) networks or substation LANs (Local Area Networks) using high speed switched Ethernet to obtain necessary response times.

The current version of IEC 61850-90-1 ("Use of IEC 61850 for the

communication between substations") describe the use of IEC 61850-8-1 GOOSE and IEC 61850-9-2 SV, which both are Ethernet Layer 2 based protocols. (IEC 61850-90-5 includes routable SV (sampled values) through UDP (User Datagram Protocol)).

However, an Ethernet / Layer 2 protocol is not routable. An IP-based solution may therefore be more appropriate for inter substation

communication since IP provides routing capabilities. But if all substations are connected on Ethernet / Layer 2, special measures are required to limit the multicast / broadcast domain. An additional UDP layer would however require updates of the SW stacks (both 61850 stack and IP stack).

There is hence a need for improved communication between substations.

SUMMARY

In view of the above, a general object of the present disclosure is to provide methods, computer programs and electronic devices for improved

communication between substations.

The ideas presented in the disclosure are based on the understanding that electronic devices could be provided with a functionality to pack / unpack an Ethernet frame (e.g. the IEC 61850-9-2 SV frame) into an IP packet or another Ethernet frame, transparently from the protocol stack. The application and the protocol stack create the Ethernet frame, but before it is sent on the network, the frame could be re-packed into an IP packet or Ethernet frame. On the network e.g. the IEC 61850-9-2 frame would thus appear as an IP / Layer 3 packet which thus can be routed. Hence, a particular object of the present disclosure is to provide methods, a computer program and electronic devices for transmission and reception of packets in substation networks enabling routing of Ethernet frames.

Hence, according to a first aspect of the present disclosure there is provided a method for packet transmission in a network. The method is performed in a first electronic device of the network. The method comprises receiving a first Ethernet frame from an Ethernet driver via a first bus interface. The method further comprises generating a first internet protocol, IP, packet comprising an IP header and comprising the first Ethernet frame of data as payload, thereby enabling routing of said first Ethernet frame. The method further comprises generating a second Ethernet frame by adding an Ethernet header to said first IP packet. The method further comprises providing the second Ethernet frame to a MAC layer or a physical, PHY, layer or an Ethernet controller via a second bus interface.

Advantageously this enables e.g. IEC 61850-8-1 GOOSE and IEC 61850 9-2 SV frames to be routable by means of a device internal tunneling and without any modifications being made to the application or the IEC 61850 protocol stacks. Advantageously there is thus no impact on the software stacks.

Advantageously the method may be implemented by means of standard protocols. Advantageously the method is simple, thus allowing easy implementation using e.g. FPGA for frame encapsulation and/or extraction. Performing the packing and unpacking in hardware enables fast processing of the Ethernet frames. Fast processing may in some situations, such as in the case of IEC 61850-8-1 GOOSE based communications, be critical. The disclosed embodiments allows the traffic to be encapsulated in IP packets whilst fulfilling any real-time requirements associated with the transmission thereof.

Advantageously an OSI layer 2 network, like a substation station bus or process bus networks, can be connected on an OSI layer 3, thereby enabling routing.

According to a second aspect of the present disclosure there is provided a computer program for packet transmission in a network. The computer program comprises computer program code which, when run on at least one processing unit, causes the at least one processing unit to perform a method according to the first aspect.

According to a third aspect of the present disclosure there is provided a computer program product comprising a computer program according to the second aspect and a computer readable means on which the computer program is stored. According to a fourth aspect of the present disclosure there is provided a method for packet reception in a network. The method is performed in a second electronic device of the network. The method comprises receiving a second Ethernet frame from a medium access, MAC, layer or a physical, PHY, layer or an Ethernet controller via a second bus interface. The method further comprises disregarding a MAC address and an internet protocol, IP, header in said second Ethernet frame, thereby retrieving a first IP packet enabling routing of a first Ethernet frame. The method further comprises extracting a payload from said first IP packet, the payload representing said first Ethernet frame. The method further comprises providing said first Ethernet frame to an Ethernet driver via a first bus interface.

According to a fifth aspect of the present disclosure there is provided a computer program for packet reception in a network. The computer program comprises computer program code which, when run on at least one

processing unit, causes the at least one processing unit to perform a method according to the fourth aspect. According to a sixth aspect of the present disclosure there is provided a computer program product comprising a computer program according to the fifth aspect and a computer readable means on which the computer program is stored. According to a seventh aspect of the present disclosure there is provided a first electronic device for packet transmission in a network. The first electronic device comprises hardware circuitry arranged to perform a method according to the first aspect.

According to an eight aspect of the present disclosure there is provided a second electronic device for packet reception in a network. The second electronic device comprises hardware circuitry arranged to perform a method according to the fourth aspect.

It is to be noted that any feature of the first, second, third, fourth, fifth, sixth, seventh, and eight aspects may be applied to any other aspect, wherever appropriate. Likewise, any advantage of the first aspect may equally apply to the second, third, fourth, fifth, sixth, seventh, and/or eight aspect,

respectively, and vice versa. Other objectives, features and advantages of the enclosed embodiments will be apparent from the following detailed disclosure, from the attached dependent claims as well as from the drawings. Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a/an/the element, apparatus, component, means, step, etc." are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is now described, by way of example, with reference to the accompanying drawings, in which: Fig l is a schematic diagram of a substation network;

Fig 2 schematically illustrates functional modules of an electronic device;

Fig 3 schematically illustrates functional modules of a gateway device;

Fig 4 schematically illustrates computer program products; Figs 5 and 6 are flowcharts of methods for latency determination in a substation network; and

Figs 8, 9 and io are protocol stacks according to embodiments. DETAILED DESCRIPTION

The invention will now be described more fully hereinafter with reference to the accompanying drawings, in which certain embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout the description.

Fig 1 schematically illustrates parts of a substation network 1, which in turn may be a part of a power grid network. The substation network 1 comprises a number of electronic devices 2 (hereinafter represented by a first electronic device 2a and a second electronic device 2b) and a number of gateway devices 3 interconnecting the electronic devices 2a, 2b. The electronic devices 2a, 2b may be so-called intelligent electronic devices, IEDs. As used in the electric power industry an IED is a microprocessor-based controller of power system equipment, such as circuit breakers, transformers, and capacitor banks. The electronic device 2a, 2b may be operatively coupled to at least one control device 17.

Each electronic device 2a, 2b is typically part of a substation 4. However, a substation 4 may comprise more than one electronic device 2a, 2b. A substation 4 is a node in the power grid network 1. The substation 4 serves the purpose of generating, transmitting, and distributing electric energy from power sources to consumers, such as industrial plants or households. A substation 4 generally comprises primary equipment (such as switchgears, breakers, transformers, etc.) and secondary equipment (such as sensors, merging units, the electronic devices 2a, 2b, etc.).

The operation of the first electronic device 2a, the second electronic device 2b and the gateway device 3, including performing a method for transmission and/or reception of packets in the substation network 1, will now be described in more detail with reference to the substation network of Fig 1, the electronic device 2 (taking the role of either the first electronic device 2a or the second electronic device 2b) of Fig 2, the gateway device 3 of Fig 3, the computer program product of Fig 4, the flowcharts of Figs 5 and 6 and the protocol stacks of Figs 7, 8 and 9.

Fig 2 illustrates an electronic device 2. The electronic device comprises a processing unit 5, a first bus interface 6, and a second bus interface 7, collectively enabling the electronic device to perform the herein disclosed subject matter associated with the first electronic device 2a and/or the second electronic device 2b. For example, the processing unit 5 is provided using any combination of one or more of a suitable central processing unit (CPU), multiprocessor, microcontroller, digital signal processor (DSP), application specific integrated circuit (ASIC), field programmable gate array (FPGA) etc., capable of executing software instructions stored in a computer program product 12a, 12b (as in Fig 4). Thus the processing unit 5 is thereby preferably arranged to execute methods as herein disclosed. As noted above, the electronic device 2 may be an intelligent electronic device, IED. As also noted above, the electronic device 2 may be part of a substation 4.

For compatibility, a gateway device may be used to unpack packets / frames communicated between different electronic devices 2a, 2b. Fig 3 illustrates a gateway device 3. The gateway device 3 comprises a processing unit 8 (like the processing unit 5), a first bus interface 9, and a second bus interface 10, collectively enabling the gateway device 3 to perform the herein disclosed subject matter associated with the gateway device 3.

The methods may be provided as computer programs 11a, lib. Fig 4 shows one example of a computer program product 12a, 12b comprising computer readable means 13a, 13b. On this computer readable means 13a, 13b, one or more computer programs 11a, lib can be stored, which one or more computer programs 11a, 11b can cause the processing units 5, 8 and thereto operatively coupled entities and devices to execute methods according to embodiments described herein. It is to be noted that the computer programs 11a, lib may be stored on one common computer program product and hence on one common computer readable means. In the example of Fig 4, the computer program product 12a, 12b is illustrated as an optical disc, such as a CD (compact disc) or a DVD (digital versatile disc) or a Blu-Ray disc. The computer program product could also be embodied as a memory (RAM, ROM, EPROM, EEPROM) and more particularly as a non-volatile storage medium of a device in an external memory such as a USB (Universal Serial Bus) memory. The computer readable means 13a, 13b may thus represent persistent storage, which, for example, can be any single one or combination of magnetic memory, optical memory, solid state memory or even remotely mounted memory. Further, while the one or more computer programs 11a, 11b is here schematically shown as a track on the depicted optical disk, the one or more computer programs 11a, lib can be stored in any way which is suitable for the computer program product 12a, 12b. The one or more computer programs 11a, 11b could also be implemented in hardware. Computer networks use a tunneling protocol when one network

protocol (the delivery protocol) encapsulates a different payload protocol. By using tunneling one can (for example) carry a payload over an incompatible delivery-network, or provide a secure path through an untrusted network. Tunneling typically contrasts with a layered protocol model such as those of OSI (open systems interconnection) or TCP/IP. The delivery protocol usually (but not always) operates at a higher level in the model than does the payload protocol, or at the same level. Embodiments presented herein are based on adding a layer in the protocol stack used for transmission and reception of messages between substations, thereby enabling routing of otherwise non-routable Ethernet frames.

Methods for packet transmission and reception in a network l will be described next. The network l may be a substation network l (i.e. a network l of substations 4).

In a step S2 a first Ethernet frame is via a first bus interface 6, 9 received from an Ethernet driver. The first Ethernet frame may comprise a frame check sequence. The first Ethernet frame is received by the first electronic device 2a. This step may be preceded by a number of preliminary steps. For example a software application 14a, 15a, 16a may process the data to be transmitted, and also provide the data to a protocol API (application programming interface). The data may represent at least one sample value as received by the electronic device from the at least one control device 17. The used protocol stack 14b, 15b, 15c (e.g. IEC 61850-9-2) may then further process the data to be transmitted, and provide it to the Ethernet driver. In general terms the Ethernet driver may represent the software (SW) side of the MAC layer or Ethernet Controller, and be aware of the internal registers and how to operate the MAC layer or Ethernet Controller). The Ethernet driver may thus receive the data to be transmitted, further process the data and provide the data in the form of the first Ethernet frame to the Ethernet Controller or MAC layer via a serial or parallel bus interface. According to embodiments this step of providing represents the last step executed in software. According to a first embodiment a protocol layer 14c is added between the protocol stack / driver and the MAC (Media Access Controller) layer i4d or Ethernet controller. This is illustrated in the protocol stack 14 of Fig 7.

According to this embodiment the Ethernet driver thus provides its data to this layer instead of the MAC or Ethernet Controller. Thus, the first Ethernet frame may according to the first embodiment be an IEC 61850-9-2 compliant frame or an IEC 61850-8-1 generic object oriented substation events, GOOSE, compliant frame. The second Ethernet frame is then, according to the first embodiment, in step S8 (see below) provided to the MAC layer. At the MAC layer the data to be transmitted is processed and provided, typically in an Mil or RMII format, to the PHY layer 14ε. Alternatively this step is, according to a third embodiment (see below), performed in an Ethernet Controller, typically comprising both the MAC layer and the PHY layer.

According to a second embodiment a protocol layer 15c instead added between the MAC (Media Access Controller) layer isd and the PHY layer 15ε. This is illustrated in the protocol stack 15 of Fig 8. At the MAC layer the data to be transmitted is processed and provided typically in a media independent interface (Mil) or reduced media independent interface (RMII) format to the PHY layer. An additional layer is here added between the MAC layer and the PHY layer. The MAC layer provides thus its data to this added layer instead of to the PHY layer. The resulting new frame (from the added new layer) is encoded into MII/RMII signals and provided to the PHY layer. Thus, according to the second embodiment the first Ethernet frame is a MAC frame. The second Ethernet frame is then in step S8 (see below) provided to the PHY layer.

In a step S4 a first internet protocol, IP, packet comprising an IP header and comprising the first Ethernet frame of data as payload is generated. Routing of the first Ethernet frame is thereby enabled. An integrity message

authentication code may, in a step Sio, be added to the payload. According to the second embodiment media independent interface (Mil) or reduced media independent interface (RMII) signals may be utilized during generation of the first IP packet. For example, Mil or RMII signals may in a step S16 be decoded in the first Ethernet frame to determine that the first IP packet is to be generated for the first Ethernet frame. Which frames to be transmitted that should be packed into an IP packet (e.g. all 61850-9-2 frames) may thereby be identified. All other frames may be provided further, without any modifications, to the Ethernet controller or the MAC layer. In a step S6 a second Ethernet frame is generated by an Ethernet header being added to the first IP packet. A frame check sequence may, in a step S12, be added to the first IP packet. Additionally, also a preamble may be added to the first IP packet. Further, also a padding may be added to the first IP packet if the second Ethernet frame otherwise would be too short.

In a step S8 a second Ethernet frame is provided to a MAC layer or a physical, PHY, layer or an Ethernet controller via a second bus interface 7, 10.

In a step S14 the second Ethernet frame may be transmitted from the PHY layer to another device (such as a second electronic device 2b or a gateway device 4) in the substation network 1. Typically the transmission utilizes a wire or an optical fibre.

The steps S2, S4, S6, and S8 may be performed in hardware (HW) circuitry, such as the processing unit 5, 8, of the first electronic device 2a or the gateway device 3. Also the step S14 may be performed in hardware circuitry of the first electronic device 2a.

According to a third embodiment the steps S2, S4, S6, and S8 are performed by the Ethernet controller 16c which thus comprises both the MAC layer i6d and the PHY layer i6e. The second Ethernet frame is then, according to the third embodiment, in step S8 provided to a PHY layer unit of the Ethernet controller. This is illustrated in the protocol stack 16 of Fig 9.

At the receiving end the corresponding reception operations are performed. Unpacking into the original Ethernet frame can be accomplished in either a gateway device or an electronic device, such as an IED.

In a step S18 the second Ethernet frame is received from a medium access, MAC, layer or a physical, PHY, layer or an Ethernet controller via the second bus interface 7, 10. The second Ethernet frame is received by the second electronic device 2b. The second Ethernet frame may first be received, in a step S30, on the PHY layer from a first electronic device 2a or a gateway device 4. As noted above, according to the first embodiment an additional layer is added on top of the Ethernet Controller or MAC layer. At the added layer of the first embodiment it is thus detected that a frame is received and that it has been packed according to steps S4 and S6; other received frames remain unmodified. According to the first embodiment the first Ethernet frame is an IEC 61850-9-2 compliant frame or an IEC 61850-8-1 generic object oriented substation events, GOOSE, compliant frame. The second Ethernet frame is then in step S18 received from the MAC layer. According to the first embodiment the data is at the MAC layer processed and provided to the Ethernet driver.

As noted above, according to the second embodiment an additional layer is added between the PHY layer and the MAC layer. Hence, according to the second embodiment first Ethernet frame is a MAC frame. The second

Ethernet frame is then in step S18 received from the PHY layer and in step S4 (see below) first provided to the MAC layer which thus receives the frame via the Mil / RMII interface, decodes the data and provides the received frame to the Ethernet driver.

In a step S20 a first IP packet is retrieved by disregarding the Ethernet header and the IP header in the second Ethernet frame. As noted above, the first IP packet enables routing of the first Ethernet frame. As also noted above the first IP packet may further comprise a frame check sequence. In a step S28 the frame check sequence of the second Ethernet frame may be verified (and then removed). The verification in step S28 may be performed prior to the retrieval of step S20; the retrieval of step S20 may be performed exclusively in case of successful verification of the frame check sequence in step S20. If a preamble previously has been added, the preamble may be removed. Likewise, if a padding has been added, the padding may be removed. The step S28 of verifying may be performed prior to extracting the payload. Retrieving the first IP packet may utilize Mil or RMII signals. For example, in a step S32 Mil or RMII signals in the second Ethernet frame may be decoded to determine that the second Ethernet frame comprises the first IP packet. In a step S22 the payload is extracted from the first IP packet. The payload represents the first Ethernet frame. The first Ethernet frame is thereby retrieved. As noted above the payload may further comprise an integrity message authentication code. The integrity message authentication code may be utilized to verify that the original content has not been modified on its way; if the integrity has been violated, the frame may be dropped. In a step S26 the integrity message authentication code may be verified and thereafter removed from the payload. The verification is performed to verify whether or not the message is authentic. In a step S24 the first Ethernet frame is provided to the Ethernet driver via the first bus interface 6, 9. The Ethernet driver may then retrieve the

Ethernet frame, process it, and provide it to the protocol stack (e.g. IEC 61850-9-2). After that the software application may process the received data. For example, according to the second embodiment the Ethernet driver provides the first Ethernet frame by means or Mil or MRU signals to the MAC layer which in turn may verify a frame check sequence of the first Ethernet frame.

The steps S18, S20, S22, and S24 may be performed in hardware circuitry such as the processing unit 5, 8, of the second electronic device 2b or the gateway device 3. Further, also one or more of the steps S26, S28 and S32 may be performed in hardware circuitry such as the processing unit 5, 8, of the second electronic device 2b or the gateway device 3.

According to the third embodiment the steps S18, S20, S22, and S24 are performed by the Ethernet controller. The second Ethernet frame in step 18 is then received by a PHY layer unit of the Ethernet controller.

In summary, the herein disclosed embodiment relate to communication between substations, and in particular to transmission and reception of packets in in a substation networks. In order to enable routing of otherwise non-routable packets, a device internal tunneling mechanism is provided. The tunneling mechanism is provided by means of an added protocol layer. The added protocol layer does not imply any modifications to already existing protocol layers. According to the first embodiment the new protocol layer is provided on top of the medium access layer. According to the second embodiment the new protocol layer is provided between the physical layer and the medium access layer. According to the third embodiment the new protocol layer is provided as part of an Ethernet controller.

The invention has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the invention, as defined by the appended patent claims.