Transaction SCI-01: Transfer Schedule

Schlagwörter: SCI, SCI-01, Transfere Schedule

After the participation on the energy market and the coordination with the SO according to the planned schedules, the VPPOP transfers the individual schedules for the DEUs to the DEUCs. Therefore, the VPPOP creates the schedules (based on the existing asset data) and executes the transmission to the various DEUC.

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1 Scope

After the participation on the energy market and the coordination with the SO according to the planned schedules, the VPPOP transfers the individual schedules for the DEUs to the DEUCs. Therefore, the VPPOP creates the schedules (based on the existing asset data) and executes the transmission to the various DEUC.

 

2 Actor Roles

TransactionSCI-01.PNG

Figure 1: Transaction [SCI-01] Transfer Schedule, shows the sub-actors to be used in the single actors and the interaction belong them. Connection of sub-actors within one actor are out scope for interoperability testing, i.e. only the transaction between TransactionInitiator and TransactionResponder is specified in the presented profile. The internal interactions are prerequisites to enable the interoperability testing.

Tab.1 Actor Roles

Role:

FSCH-Encoder: Each actor can invoke the encoder subactor prior data is actually transmitted. The encoder has the task to map the information from LNs according to MMS into a payload data unit (PDU), which than is transported to the destination actor. Therefore, the basic encoding rules (BER) are used.

Actor(s):

The following actors may play the role of FSCH-Encoder: VPPOP

Role:

Transaction Initiator: The transaction initiator starts and executes the transport of a payload data unit (PDU) to a receiving actor’s transaction responder subactor via TCP/IP. If specified the transaction initiator uses the general “Secure Connection Profile ???” from IHE to establish a secured connection prior the data transmission actually starts, if that is not already in place.

Actor(s)

The following actors may play the role of transaction initiator: VPPOP, DEUC and DEU.

Role:

Transaction Responder: The transaction responder receives a PDU via TCP/IP and if specified, acknowledges the reception of the PDU. In case a secure connection is required it cooperates with the transaction initiator in establishing security.

Actor(s):

The following actors may play the role of transaction responder: VPPOP, DEUC and DEU.

Role:

FSCH-Decoder: The decoder decrypts the MMS notifications with PDU forwarded from the Transaction Responder into the actors respective IEC 61850 LNs.

Actor(s):

The following actors may play the role of FSCH-Decoder: DEUC.

  

3 Referenced Standards

  • IEC 61850-7-420

 

4 Interaction Diagrams

This includes the interoperability use cases of message encoding and transfer according to IEC 61850.

  Transfer_Schedule_Send_Control_Signals.png

Figure 2: Overview of Transaction Transfer Schedule SCI-01

 

SequenceDiagramEncodeFSCH.png

 Figure 3: Test steps defined for testing the encoders compliance to IEC 61850

SequenceDiagramSCI-1.png

 Figure 4: Sequence of test steps needed for the test case [SCI-01] Send Schedule. In this case, the message depicts
a secured connection (shown by the red color).

 

SequenceDiagramDecodeFSCH.png

 Figure 5: Test steps defined for testing the decoders compliance to IEC 61850

4.1 Create an MMS message

The actions performed by the FSCH-Encoder being part of a Transfer Schedule transaction (CSE-01).

 

4.1.1 Trigger Events

The VPPOP triggers the transmission of a schedule indicating the FSCH LN to be transmitted and the DEUC it is intended for.

4.1.2 Message Semantics

The FSCH-Encoder creates an MMS message from the contents of the LN FSCH: the data of the LN FSCH is mapped according to the IEC 61850-8-1 into an MMS domain using Named Variable Objects to hold the LN FSCH contents associated with their individual identifiers.

Common structure of MMS messages created from LN data: $$

Extended by LN data attributes:  $$$

Thus, the MMS messages contain the following objects/elements:

FSCH$SP$NumEntr$setVal

FSCH$SP$SchdIntv$setVal

FSCH$SP$ValASG$setMag

FSCH$SP$StrTm$setTm

 

Accronymes used:

  • FSCH: Schedule
  • SP: setting
  • SG: setting group
  • SE: setting group editable
  • NumEntr: The number of schedule entries that are valid out of the instantiated ValASG. It shall be > 0.
  • SchdInv: The schedule interval duration
  • ValASG: The ASG scheduled values (current value output as MV)
  • StrTm: Start time of the schedule in UTC time

 

4.1.3 Expected Actions

The FSCH-Encoder provides the data from the LNs in the MMS specification for the transaction initiator of the VPPOP. After receiving the MMS message, the transaction initiator shall establish a secure connection to the DEUC prior the MMS message is transmitted to the DEUC.

 

4.2 Establish Secure Connection

Actions performed by the transaction initiator of the VPPOP and the transaction responder of the DEUC in order to establish a secure connection.

 

4.2.1 Trigger Events

The transaction initiator of the VPPOP received an MMS message from the FSCH-Encoder and yet there exists no secure connection to the DEUC

4.2.2 Message Semantics

Diffie-Hellman key exchange: First, the VPPOP and the DEUC exchange a prime modulus and a generator publicly. Then the VPPOP calculates an interim result with its private key and the exchanged modulus and generator. The DEUC does the same with its private key. Both exchange their interim result publicly. After receiving the interim result from the DEUC, the VPPOP can calculate the key by applying the interim result from the DEUC in the modulus function to the power of its private key. The DEUC can do the same. The DEUC applies the interim result from the VPPOP in the modules function to the power of its private key. Both receive the same key which can be used to encrypt and decode messages.

 

4.2.3 Expected Actions

The transaction initiator calculated a secure key and can encrypt the MMS message with it, i.e. a secure connection is ready to be used (is established).

 

4.3 Transmit MMS message

Actions of the transaction initiator of the VPPOP and the transaction responder of the DEUC in order to transfer the MMS message from the VPPOP to the DEUC.

 

4.3.1 Trigger Events

The transaction initiator of the VPPOP received an MMS message from the FSCH-Encoder and a secure connection to the DEUC addressed has already been established

4.3.2 Message Semantics

The VPPOP transaction initiator pushes the encrypted MMS messages into the transmit queue of the TPKT channel connecting it with the DEUC. Whenever data is present in the TPKT transmit queue it is transmitted bit-by-bit at maximum speed (line-rate) to the other end of the TPKT channel at the DEUC, until the transmit queue becomes idle again. Here TPKT uses a virtual channel established over TCP/IP and thus, is the line-speed variable. The transmission speed depends solely on the instantaneous IP performance of the end-to-end path between VPPOP and DEUC, including delays caused by the packet repetitions in case of packet losses.

Once all bits of an encrypted MMS message have arrived in the TPKT receiver of the transaction responder (at the DEUC) the message is decrypted using the key generated during the secure channel setup and the MMS message is provided to the FSCH-Decoder.

4.3.3 Expected Actions

The decrypted MMS message containing a schedule is available at the DEUC transaction responder.

 

4.4 Forward Schedule MMS

Actions of the FSCH-Decoder to complete a Schedule Transfer transaction (CSE-01) at the DEUC.

 

4.4.1 Trigger Events

The transaction responder of the DEUC received an MMS message containing a schedule from the VPPOP, which has to be decoded by the FSCH-Decoder.

4.4.2 Message Semantics

According to the … the MMS message is decoded into the FSCH LN and … of the DEUC LC/IDC.

4.4.3 Expected Actions

The FSCH-Decoder decoded the MMS messages and has created local LNs and data objects that hold the same information as the LNs and data objects at the VPPOP, which were to be transmitted.

  

5 Security Considerations

For secure MMS services a secure connection is mandatory. 

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sobia
28. Mai 2017, 10:52
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