Over the past 10 to 15 years, utilities have seen tremendous growth in the number of smart relays and other smart substation devices. In addition, there have been significant advancements in communications to these field devices. The devices include microprocessor-based relays, meters, fault and event recorders, transformer dissolved gas analysis (DGA) monitors, battery monitors, bushing monitors, breaker monitors and transformer temperature monitors. While some of these devices provide traditional supervisory control and data acquisition (SCADA) data, they also offer data that can be used by various departments to improve the planning, operations and maintenance of power system assets.

Communications Infrastructure Change

Driven primarily by increasing telephone circuit costs, Southern Company began a multi-year project to convert analog four-wire telecom circuits to digital frame-relay circuits in 2003. The analog four-wire circuits provided only SCADA communications, whereas the digital frame-relay circuits provide a network connectivity solution for substations, allowing SCADA communications and what the company calls “engineering access.”

Engineering access to smart substation devices is defined as the ability to remotely connect to substation devices and perform various functions, including data or file collection, troubleshooting and updates. This network connection is the conduit to collect the additional data from the smart substation devices. Southern Company has more than 750 substations with frame-relay communications and that number continues to grow as new substations are added or major substation expansion projects are completed.

With its substation network connectivity solution under way, the utility embarked on an effort to identify technology solutions that could support the collection and storage of large volumes of data, as well as provide tools for visualization and analysis of the data. One prerequisite was to not burden the Southern Company energy management system (EMS) or transmission control centers with data that was not needed for real-time operations.

Business Drivers

While there is an increasing number of breakers, transformers, coupling capacitor voltage transformers (CCVTs) and other power system equipment, the funds to maintain this infrastructure remain flat with pressures to decrease costs. This leads the substation maintenance organization to implement more condition-based maintenance programs, which require equipment data. And, there are a growing number of departments that need access to substation device data. Additionally, the difficulty and inefficiency of individuals performing ad hoc data extraction from these devices is becoming worse because of increased security around access to substation devices.

Further, there is an overriding desire in all departments to minimize both customer outages and avoid costly repairs and site cleanup from catastrophic failures. This increases the pressure on operations and maintenance organizations to predict power system equipment problems and remove equipment from service before a failure occurs.

Reducing the time it takes to collect and analyze digital fault recorder and protective relay event files reduces the time it takes to locate, isolate and restore electric service, which would contribute to improving reliability metrics and customer satisfaction. Lastly, having an easy-to-use central repository for power system data and event files, and providing more flexible tools for visualization and data analysis, will improve the results of short- and long-term power system studies.

Southern Company also needed a solution that would integrate well with its existing standard substation gateway solution, which is the Schweitzer Engineering Laboratories (SEL) 3351 running Subnet Solutions SubstationSERVER.NET software. After vendor evaluations and a request for proposal process, Southern Company selected a combination solution from two vendors: InStep Software's eDNA Historian software and Subnet Solutions' ESNET software. Southern calls the combined solution the Field Data Historian (FDH).

Pilot Project

In 2008, the utility implemented FDH in a pilot project at 13 substations where time series data are being collected by DNP and eDNA native protocols. In addition, event files from SEL relays and digital fault recorders are being transferred from the substations to a file collection server. Information such as fault current, location and phase involvement is parsed out of event files and made available for viewing by operations personnel. Other event file information such as breaker time to trip and calculated breaker contact wear is parsed out of event files and then sent to the eDNA historian for storage and analysis.

Southern Company takes a multi-layered approach to securing access to smart substation devices and access to the data available from these devices. Substations are located on a dedicated firewalled network with numerous regional firewalls to further segment substation access. Two-factor authentication is required to enter the centralized substation access control portal. The central access control portal provides detailed audit logs of all access and enforces an application air gap, which prevents users from having direct access to the substation network. Access to the historian data is restricted to approved users who have been included in a separate application access control list.

The scope of the FDH pilot project included 111 breakers, 18 transformers, 30 CCVTs, 7 DGA monitors and 25 digital fault recorders. The pilot focused on the following areas:

  • Breakers — the time to trip, continuous currents, fault magnitude, number of operation and the time since the last operation

  • Transformers — three-phase megavolt amperes, continuous currents and transformer gas data

  • CCVTs — evaluating predictive failure indicators

    • For single-phase CCVTs, comparing the sync-voltage to phase-voltage magnitudes and angles

    • For three-phase CCVTs, comparing the phase- and sequence-voltage angle deviations from 120-degree separations and monitoring negative-voltage and zero- sequence-voltage magnitudes

  • Automation of fault data event file collection from SEL relays and digital fault recorders.

Future Strategy

The objectives of the pilot project were as follows:

  • Show the value in the data and analysis

  • Learn what internal resources are required to implement this solution, both for ongoing support and data analysis

  • Evaluate three substation architectures

  • Determine what software components are required for a larger implementation.

Within 10 minutes of a power system event, event files from SEL relays and digital fault recorders are transferred from the substation to a file collection server located on a secure corporate network. The MyFaults application allows operations personnel to easily view fault and event files. The line name, phase involvement, distance to fault and duration of fault are readily available to help operators isolate the problem and restore service to customers. The application offers several ways to filter the information to only the data desired.

Before the pilot project, substation maintenance personnel had to visit the substation in person to collect DGA monitor data. Now, for the seven DGA monitors included in the pilot project, the utility collects the DGA monitor data remotely every few minutes and stores the data in the historian solution. The transformer DGA history from the pilot project monitors is available online. The historian displays and trends can be laid out to the utility's preferences and can be easily changed as desires change. Other data sources can be queried and displayed on the historian displays. Southern Company wanted to display equipment asset information such as manufacturer, equipment rating, number of phases, date of manufacture and so forth. Users are able to query the existing asset management database and display asset data alongside near real-time information on the historian displays.

Future FDH Data Interests

Southern Company is experimenting with finding an early-warning indicator for CCVT failures. The differences between the phase-voltage and sync-voltage magnitudes and angles are normally very small. Should either the magnitude or angle differences increase significantly, it could be an indicator of an impending CCVT failure. Likewise, data from early oil circuit breakers can be used to determine whether maintenance should be conducted or delayed.

Companies mentioned in this article:

Southern Company believes the future of substation asset management resides with expanding FDH. It wants to continue to integrate existing smart substation device types that will provide additional information. The utility also realizes that additional monitoring device types are needed to provide data not currently available on the system.

The FDH pilot has illuminated for Southern Company the potential value and benefits from a solution like this. In the near future, the utility will do the following in preparation for a larger FDH system expansion:

  • Develop standard data templates for each smart substation device type included in FDH. During the pilot project implementation, it was easier for the utility to gather all available data from the smart devices. It now has a better handle on what data elements are important.

  • Integrate existing smart device types into FDH, including transformer temperature controllers, load tap changer controllers and other manufacturers' DGA monitors.

  • Develop substation equipment maintenance program changes that can result from use of the FDH data.

  • Develop an architecture strategy to allow data to be collected and stored once between EMS and FDH. Southern Company selected the same historian vendor for EMS and FDH, which will make it easier to share data between the historians. Traditional SCADA data will continue to be collected by EMS. Data beyond traditional SCADA data will be collected by FDH. The utility recognizes that users need access to data from both historians for analysis and visualization.

While it will take several years to achieve full implementation, the result of this effort is the ability to collect more field data about system events and equipment performance and condition in real time. Use and analysis of this data into timely information translates into an improvement in the reliability of the power-delivery grid and improved prioritization of budgets and labor resources by optimizing the response to system events and the maintenance programs.

Operators will have more information at their disposal during outages to determine the nature and location of faults. This will allow more efficient outage restoration and more effective post-mortem analysis of system disturbances and outage events. In addition, real-time and event monitoring of the performance of substation equipment create the ability to trend equipment performance for an enterprise-level shift toward performance-based asset management versus current time-based maintenance programs.

Dawn Toporek (ddtopore@southernco.com) has worked for Georgia Power, a subsidiary of Southern Company, for 30 years. She earned a BSEE degree from the Georgia Institute of Technology and has worked in a variety of areas in T&D and marketing. Since 2000, she has been a project manager coordinating technology projects for Southern Company Transmission: enterprise geographic information system strategy, remote terminal unit monitoring, SCADA infrastructure metrics, substation wide area network conversion, substation engineering access and field device data historian projects.

Equipment Data items
Breakers Close time, closing/charging current, compressor operation (number of starts and run time), SF6 gas density and alarm, ambient temperature
Transformers Top oil temperature, winding temperature, ambient temperature, power factor from bushing sensors
Load tap changers (LTCs) Oil temperature, differential temperature, number of LTC operations, tap position, motor current, LTC filter information
Batteries Individual battery cell voltage and temperature

InStep Software www.instepsoftware.com

SEL www.selinc.com

Southern Company www.southerncompany.com

Subnet Solutions www.subnet.com