Introduction

For the preferential subject "The Impact of IEC 61850 on Protection and Automation" 12 papers were received and they fell into four main categories:

1. Configurations and architectures
2. Reliability and testing
3. Implementation experiences
4. Migration strategies

There were 61 contributions presented at the session in response to the 12 questions posed by the Special Reporter.
This article provides a short summary of the findings, the discussions and the conclusions of the session.

Configurations and architectures

When discussing configurations and architectures of substation automation systems, a factor is that computer and communication technologies double in performance every two years and that engineering technologies double in performance every three years. This means that during the life time of substation automation systems there will be changes or upgrades necessary to hardware or software. The question therefore becomes how to apply automation systems in substation that will have a total life time of over 25 years?
The main approach today is to standardize the substation. This however leads to a need for more detailed specifications that shall:

• identify the functionality, performance, security, availability, etc.
• define a robust logical architecture and map it on real devices
• define the communication and related aspects
• define the data model and related aspects
• initially consider various architectures until a well scoped one is found that is backed up by comprehensive tests

An advantage of modern automation systems is that hardware and software are becoming more and more independent. This leads to new possibilities such as adding functionality to existing systems. The impact of added functionality on system testing, availability and conformance requirements for the individual components is however a concern. Since hardware and software are never fully independent caution is advised. It is important that the performance and availability must be guaranteed during the system lifecycle and this can only be fulfilled through tested and certified products. A major benefit of IEC 61850 is that this can be supported by coordinating the possible IEDs and systems offered through the import and export of the standardized file formats in the System Configuration description Language (SCL).

Reliability and testing

Fault tolerant systems will provide means to increase the reliability of our systems in a cost effective way. An example of such an approach could be the replacement of the "main 1 and main 2" for protection schemes by single IEDs in a fault tolerant system. Some utilities may be opposed to this based on the requirement for independence of main and backup protections (N-1 criterion). An argument is that omitting redundancy in protection is limited because of the limitations given by the current network technologies. Main questions to be answered are what happens to the performance, reliability, security, availability, single points of failure, and redundancy? What if multiple IEDs fail or an IED has to be repaired or tested? In this environment the communication bus behavior and performance will be critical.

With increasing platform flexibility and CPU power, integration of functions into a single IED however becomes feasible. New schemes and functions are being studied and a possible solution may be the clustering of redundant IEDs. The discussion will certainly continue because modern communication networks in substation automation systems provides advantages and can help to increase the availability of the system.

The complexity of our next generation substation automation systems shall however be managed in such a way that test results remain consistent, reproducible, and comparable. This may partly be handled through quality assurance and accreditation procedures for conformance testing such as the ones defined and maintained by the UCA International Users Group. It is however clear that in order to test a complex network, the test system will become equally complex.

It is therefore important to keep in mind that when testing functions in an open system:

• conformance tests are required to verify systems against specifications
• performance tests are required on a reference configuration with special attention on mixed configurations
• interoperability is mandatory and should be certified.
• interactions between functions increase the number of tests

The impact of IEC 61850 on future test concepts is that testing the IED functionality can be achieved by using communication links for "injection" into an IED or system. A complicating factor may however be that test equipment must be connected directly to the process bus and station bus and must generate the input and monitor the output via the serial communication. This requires that tools with realistic and coherent test scenarios are available. Having test features integrated in the IEDs can further support testing since it can help to minimize the test effort and facilitate online testing

Finally when systems are upgraded each version could be considered as a different type, invoking a complete test requirement. Major question is what is to be retested? It is clear that our industry needs effective laboratories for the validation and diagnosis of our systems and their functionality. At this time however a lack of network testing standards exists.

Implementation Experiences

One of the main questions for utilities is whether detailed specifications for IEC 61850 based systems are needed or is there benefit in not having it specified in great detail? One should keep in mind that systems can very well be described using the traditional approach based on the:

• Single line diagram
• Functional requirements
• Dependability requirements
• Performance requirements
• Environmental requirements
• Project management
• Services

Advantages of not having detailed specifications is that not only optimized solutions are possible based on specified functions and performance but also that most manufacturers will be able to offer a solution complying with the specification. On the other hand a detailed specification supports the standardization of substations.

No matter what approach is chosen during the project design phase the described functionality has to be mapped by the system integrator to the IEC61850 data model and implementation agreements on the modeling of multifunctional IEDs will help in the development of tools for automatic processing of SCL files and IEC 61850 based user interfaces.

Now that the system integrator has been mentioned there exists controversy today whether the role of the integrator can be outsourced by utilities or not? The answer is nor easy nor without controversy but the main topics influencing the answer are:

• the business model that the utility has irrespective of the solutions that are chosen
• the fact that a system integrator needs a lot of expertise with the specific utility systems
• that there is a requirement for a technical think-tank to deal with new and enabling technologies
• what to do if you have multiple projects?

It is expected that pure integrators will emerge and the role of the integrator will evolve. New roles, such as that of the system architect, are envisioned.

Another controversial topic is that of project specific extensions of existing standards. It is clear that such approaches lead to an exact fit for a single project, but also to uncontrollable test efforts and specific conformance tests and test equipment. The flexible IEC 61850 toolbox and the possibility to extend the Data Model is a big seduction for experts wishing to implement their ideas and knowledge into a standardized framework. Therefore improvements and extensions must be discussed in IEC TC 57 in order to integrate them into IEC 61850 but not every wish may be fulfilled. Fortunately the IEC 61850 System Configuration description language supports the exchange of configuration data between manufacturers and warrants consistent and interpretable data in engineering. It also supports automatic test and application configuration as well as adherence to the standard, i.e. avoiding user-specific adaptations, ensures multi-vendor interoperability.

Finally one has to keep in mind that a single utility semantic model facilitates staff adjustment and work reuse in the utility and allows the application of vendor-independent tools with significant benefits for automation system operation, maintenance and diagnostics.

Migration Strategies

One of the effects of the evolution in technology and utility philosophy is that migration will be a natural phenomena over the life time of substations. System wide replacement programs for protection and control equipment will become necessary and will require many different migration solutions based on local situations. The first step in such a process should be the definition of the possible use cases as well as application of a common base of references for functionality on all levels and one of the goals of migration should be to limit the impact of the migration of substation systems on the network level.

In some cases fast migration strategies are possible for smaller substations by accepting constraint operation conditions. However the issue that remains when replacing many systems per year is to preserve a high quality on the protection and automation systems. This requires that one has to optimize the engineering, the FAT, the SAT, uptime, maintenance, etc.

A major step forward would be if new systems would be "maintenance free" so that we can concentrate on replacement instead of on maintenance of newly installed systems.
The use of standardized communication protocols such as IEC 61850 will result in a decrease in the need for gateways and protocol converters and should make migration easier. However for applications that require gateways, standardized mappings will be needed to support interoperability and engineering efforts. Since IEC 61850 is currently limited to the substation environment existing protocols will continued to be applied via suitable gateways.

For the reduction of engineering costs, versatile tools are required which support continuous engineering of pure IEC 61850 communication systems as well as legacy systems. But it is clear that tools which base on an object oriented concept are superior to signal oriented tools.

When discussing migration an important aspect are the financial consequences of the migration path. Current cost/benefit results for IEC 61850 based substation automation systems show that savings are already realized by the elimination of gateways. Future savings are expected through:

• optimization of architectures and number of IEDs
• the use of GOOSE to replace hardwired connections
• the use and re-use of SCL based engineering for new substations and migration. This has to be supported however by the right set of tools.
• Process bus applications eliminating high voltage equipment and hardwired connections

CONCLUSIONS

During the session in Paris many topics have been presented and lively presentations and discussions took place on how IEC 61850 will impact protection and automation.

IEC 61850 already has and will continue to have an impact on protection and automation. New architectures become possible and require new IEDs, new test methods, re-evaluation of existing concepts and principles and thus raise controversy regarding efficiency, performance, reliability, availability and maintainability.

The strongest benefits are expected in improvements of the engineering process, the application of the process bus and the use and re-use of the object models.

Biography

Marco C. Janssen is a utility industry professional with more than 16 years' experience. He graduated in 1983 from the Polytechnic in Arnhem, The Netherlands and has followed many additional educational programs and training courses to develop further skills to support his professional activities. He is President and Chief Commercial Officer of UTInnovation LLC - a company that provides consulting and training services in the traditional areas of protection, control, substation automation and data acquisition, as well as provide insight, training, and support on the new international standard IEC 61850, advanced metering infrastructures and power quality. He is a member of WG 10, 17, 18, and 19 of IEC TC57, the IEEE-PES and the UCA International Users Group.