Leveraging Available IED Information
The trend toward deploying more intelligent electronic devices (IEDs) in substations and within the distribution grid is stronger than ever. However, in many utilities, different departments working to solve specific problems have deployed these devices in a piecemeal fashion. Often, a unified vision for substation automation and data acquisition has been lacking. With this proliferation of IEDs, there has been an exponential increase in the amount of data available. Currently, much of this data remains stranded in the field.
At the control center, technology has had a significant impact as well. Traditionally, SCADA and other substation data have been accessed through a hierarchical system, with the Energy Management System (EMS) at its apex. In this topology, other enterprise-level applications that require this data must obtain it from the EMS. In many utilities, these other applications are increasing in both number and importance. The EMS is still a critical application for operating the utility, but it is no longer the “center of the universe.” Full-featured historians are now playing a key role in operating the power grid, and the use of third-party network and maintenance applications is becoming widespread.
These new applications are frequently interested in data that is produced by IEDs but that is not accessible through the EMS. A solution is needed for communicating this data to the applications that need it. Moving it up the traditional communications channels through the EMS is not only an inefficient use of valuable EMS resources, but in many cases the protocols used cannot handle the newer data types.
An architecture is needed that allows data from multiple sources (IEDs, RTUs, meters) to be accessed by multiple hosts (control center or enterprise applications or human users). In other words, a “many-to-many” communications infrastructure. This architecture should also be flexible enough to support the ongoing addition of IEDs and new applications or queries that require the data, in essence converting it to actionable information.
Many utilities have deployed broadband wide area networks and substation Ethernet LANs and although certain benefits are achieved through this architecture, a number of problems present themselves:
- Many IEDs have communications deficiencies. Protocol implementations are inconsistent, and in many cases data is transmitted with no confirmation, retry, error checking or security measures.
- Direct Ethernet interfaces that are retrofit to existing RTUs can result in noticeably increased latency over their serial counterparts. In a round-robin polling scheme this can result in update requirements being exceeded.
- Other key operational systems (distribution automation, GIS, outage management, other SCADA systems) can experience difficulty in getting the data they require.
- The traditional hierarchy requires considerable maintenance, particularly in data concentrator mapping tables.
In the face of these challenges, a multi-departmental effort is required to achieve true substation data integration.
Project Details
The figure below is representative of a typical architecture for data integration, where substation and distribution information is being aggregated.
Figure 1.
Note that there are two data integration servers deployed, one is the station, one in the control center. The station level substation server is responsible for integrating a large number of devices while simultaneously serving data to a local Human Machine Interface. The control center server leverages the network topology and remote, utility grade terminal servers to provide access to data in a number of IEDs and RTUs scattered throughout multiple smaller sites, such as pole top distribution automation (DA) RTUs and distribution vaults.
A primary objective of the system is to allow for multiple, simultaneous host applications to access each IED. The following describes the possible applications deployed. Note that in many cases, a single data point is served to more than one of these applications.
EMS/DMS Interface
The EMS and DMS each poll for data from the substation server or enterprise data server (e.g. RuggedCom eLAN Servers). The server provides a single, virtual RTU for each physical device. Because of the server’s processing power and the bandwidth available on the WAN, there is no need to concentrate multiple physical devices into a single virtual device. Maintaining a one-to-one relationship between physical and virtual devices allows point maps to be maintained from end to end through the system, resulting in an easy-to-understand system, and considerably reduced configuration effort.
Note that even though the network-based RTUs could be polled directly from the EMS, they are mirrored through the substation server as well. This takes advantage of the much lower poll latency of the server. Eventually, only a small subset of the available data would be reported to the EMS, with this traffic having priority over all other data.
Historian Interface
The Historian is the repository for all IED data that is believed to be of interest, either now or in the future, excluding some file types that are stored in other data repositories. The data servers maintain a separate connection with the Historian, based on either the OPC (OLE for Process Control) or DNP3 standards. The Historian information is typically displayed through a tailored browser-based interface.
Fault Record Management
The substation server also has responsibility for extracting fault records from IEDs as they are captured, and archiving them on a central file repository at the control center. Interested staff may receive notification of record capture via e-mail. This central repository for all fault records provides a consistent access point for all staff that needs this information.
IED Access Management
Another possibility of this architecture is to create an easy-to-use mechanism for remotely accessing maintenance ports on all remote devices, using the vendor’s configuration/maintenance application. The secure access management application (e.g. RuggedCom’s CrossBow) provides this functionality by allowing for transparent device connections while providing a central administrative tool for governing user roles and device access permissions. This application is commonly used in North America to address the need for securing remote user access under the NERC CIP guidelines.
Security
Network and application security is a broad issue, which should be addressed in a holistic manner across the utility. A unified security vision must exist that accommodates all networking, from SCADA data to remote IED access, to data visualization for employees. This topic is beyond the scope of this article, however, the proposed architecture takes into account best practices in authenticating devices and users, encrypting data connections, managing device and user passwords, along with monitoring all critical devices and applications through an appropriate security information and event management system.
Summary
The benefits of building a data communications infrastructure on powerful, modern substation integration and access technology can yield tremendous benefits in supporting more than just traditional SCADA applications. Turning this data into actionable information is the next natural progression in the migration to a smarter grid.
By Jeff Gill, RuggedCom.
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