IEEE 1646:2004 pdf free download – IEEE Standard Communication Delivery Time Performance Requirements for Electric Power Substation Automation
4.3 Application specific communication performance requirements
Delivery time is specified in terms of the time when the message leaves the sending application to the time when thereceiving application gets the message. Figure 1 shows time components that define the time requirement.Application-to-application time is defined as the sum of the times required for the sending IED communicationprocessor to accept the data from the sending application “f1″, and exit the output queue of the sender “a”, plus timeover the communication network (including processor time required by routers, bridges, gateways, etc.) “b”, plus thetime “c”” required for the receiving IED communication processor to extract the message content and present it to thereceiving application “f2″.
Table 3 shows communication performance requirements needed to support the substation applications that use theinformation ‘. Table 4 shows the future communication requirements for transferring,in near real time over thenetwork, large volumes of data such as transducer measurements，, wave-form data from current differential relays,and synchrophasor time sync data.Values in the column titled Maximum Delivery Time” in some cases define arange,or the qualifier‘up to”, which means that the maximum delivery time is determined by specificimplementations and operating constraints for the application.
Three levels of message criticality (criticality class) are specified: high, medium and low. In addition to messagecriticality, three levels of message priority (priority class) are specified: high, normal and low. Typical messagessizes are specified in terms of the number of points transferred,message bits， message bytes, or the number ofoperations.Rate is the frequency of updating the information or the condition that causes the message to begenerated. Time skew specifies the resolution required by the data/application.
Priority: The communication system shall support four levels of access priority,，respectively: reserved,high,medium or average, and low.One level will be selected for a communication connection by its userapplication. Servicing by a communication lED of a lower-priority message will be interrupted betweenpackets by a higher-priority message or packet.
Criticality:The communication system shall support three levels of data delivery criticality named high,medium, and non-critical (see Clause 5.4).One level will be selected for a communication connection byits user application.
Security: Communication Security is defined as the immunity of the communication network to accidentalor intentional unauthorized access. The communication sysitem shall support three levels of security ofaccess to network resources: high, medium, and low.High security access will be limited to predefined andappropriately validated Clients. Medium and low security access will be granted respectively to Clientsmeeting simple or no criteria.
Integrity: Integrity is defined as immunity of the network to data transfer errors resulting from accidentalor intentional interference. The communication system shall support three levels of immunity: high,medium, and low.High integrity requires a very small probability of undetected error.Medium integrity issufficient where inherent data redundancy provides adequate error immunity.Low integrity applies whereerrors are only a temporary nuisance to the data recipient.
Table 6 describes the data transport requirements (H=high，M=medium,L=low) for priority, criticality,security and integrity needed to exchange specific types of information between applications within thesubstation and with applications external to the substation.