Southern California Edison (SCE) has been remote controlling and automating substations since the late 1940s using a combination of single point-to-point supervisory control and single master-to-multiple remote terminal units (RTUs). In the early 1980s, the utility pioneered the use of industrial factory-programmable logic controllers (PLC) for automatic substation control systems. The increasing confidence in the PLC led to the integration of the RTU and PLC. As the development and operational capabilities of protection relays and meters advanced, enabling communication with these substation devices, SCE (Rancho Cucamonga, California, U.S.) realized that a distributed automation system could be the next stage of development. In 1994, SCE produced a number of prototype systems that incorporated intelligent electronic devices (IEDs), substation local area networks (LANs), protocol converters, supervisory control and data acquisition (SCADA) interface and a human machine interface (HMI) workstation. Although each of these pilot systems proved that integrated and distributed substation automation was viable, several serious concerns were identified:
- To design and configure each system, considerable engineering resource time was required.
- The discrete component count was too high, and because of communications limitations, a gateway was required for every one to four IEDs.
- Manual software programming was time consuming and had a high error rate that required correction, which extended the time for final commissioning.
While these shortcomings delayed development, SCE remained focused on the advanced functionality the new generation of IEDs offered. In 1995, the utility launched a program to automate hundreds of the its substations. Following a nationwide search for the best system available to satisfy SCE’s specification, the utility selected the ABB PRICOM substation automation system on the basis of the high-speed LAN, low component count, simple integration and cost. Development of the Substation Modeling Tool At the start of the automation program, the SCE engineering team quickly realized the project would benefit if the design process was automated. Anthony Johnson, an SCE engineer responsible for one of the prototype systems, developed a Substation Modeling Tool (SMT) that could simultaneously automate the design of the system configuration and software integration requirements. The SMT used design information from the existing substation to create a point list from which the HMI and SCADA master could be configured. Johnson, working with SCE’s SCADA department, developed a common language of links that could be used to describe the points in the utility’s SCADA master databases. Furthermore, working with ABB, SCE developed a common language from which the HMI could be built.
To accomplish the planned large-scale project, SCE and ABB concluded the design work should be automated; hence, the SMT produced the following benefits:
- It eliminated the need to employ skilled programmers and engineers on manual, labor-intensive and time-consuming design work.
- It satisfied the SCE-ABB goal to eliminate or minimize errors in the manual entry and design work, bearing in mind that manual methods generate the highest error rate in the final product.
- All parties would work from the same source master document; thus, complete coordination and use of identical data were guaranteed.
Substation Modeling Tool
The SCE–SMT is a software application tool that automates the creation of design documents, point lists, tables and reports that are necessary to design substation automation/SCADA project elements. The starting point is a complete and accurate single-line diagram of the substation to be automated. Information from this diagram is entered into the SMT via menu-driven screens and diagrams, and the drop-down menu provides access to displays.
Figure 1 shows the configuration for a “B-Station” (distribution voltage), and by selecting “Voltage Configuration,” the second screen requests all the data for the configuration (Fig. 2). The check boxes and edit fields provide the default data for all typical line, transformer and capacitor dialogue screens. Following entry of the basic substation configuration (Fig. 3), each substation rack position is then configured to provide the data required to build the SCADA RTU emulator, to append the SCADA Master database and to construct the HMI control database. Figure 4 shows the user-selected graphics needed to construct the HMI screenware database (connectivity).
Finally, the SMT highlights any items that have been missed or entered incorrectly, and each dialogue sheet contains “self checking” to ensure no required steps or data inputs are missed.
When the data input process is complete, the SMT menu gives the user the option to select “Create Reports,” which displays a list of 17 reports and documents available to all the parties involved with the project (Table 1). Briefly, the key reports listed in Table 1 give the following information:
- Digital and Analog Point Lists are key elements in ensuring accuracy in the SCADA portions of the overall project and were used by ABB to generate the emulated SCADA RTU database.
- The Bill of Materials details the exact hardware that will form part of the Substation Automation System, which includes computer equipment, relays, PLCs and other hardware items.
- Factory Acceptance Test Digital and FAT Analog Forms are used to ensure that all points are properly tested and recorded during the factory acceptance tests.
- The Control Data Report (Connectivity Data) defines the topology of the circuit breakers, switches, transformers and other equipment in the substation. The data serves two purposes: it defines the layout of the basic user interface display (single-line diagram) and it provides the input to the ABB–PRICOM topology processor that employs color-tracing to clearly show the energized/de-energized status of all lines and equipment.
- Labor Estimates is used to determine SCE field personnel requirements in terms of numbers and time duration. It is used to balance resource requirements with resource availability and as a checklist for functional testing required to commission a substation.
- The Address List defines the elements of the automation system and specifies the default protective relay setting templates.
- The Drawing Schedule lists the drawings available to design and field personnel.
- A job walk is always undertaken to crosscheck the data included in various reports with the actual site conditions, any differences being resolved and corrected before the SMT process is finalized. The results are recorded as the Digital and Analog Field Reviews.
- The SMT toll includes several reports designed to ensure maximum accuracy. The SMT QA Report is an internal check of the process to determine if any errors or omissions occurred at the input stage.
PRICOM Substation Automation System Features
SCE selected the ABB PRICOM substation automation system, an integrated combination of hardware and software that enables the integration of data from various substation IEDs. The system can include a local user interface (HMI) that can be used to control and operate all elements of a substation. Additional logic is used to perform various automated functions based on real-time conditions, and PRICOM provides an interface for SCADA functions and for the supply of data to corporate data warehouses.
PRICOM software includes a general-purpose input/output processor, database, display builder and user interface controls. However, many elements must be designed and engineered or configured to operate in the environment of a specific substation or utility. These include: display functions; data and symbol definitions; user interface and operation; utility-specific functions; and off-site data and control functions.
Traditional methods, including pilot projects, generally require a labor-intensive approach to data gathering, formatting data for use by other systems, and designing and building user-interface displays. The process becomes even more complicated when a SCADA link is required, because the displays and databases for the two systems are usually built and maintained by different groups.
The ABB system has been designed with off-line software tools that extract the following information from the SMT output documents to generate the databases and HMI screens for a specific substation:
- Devices to be interfaces (complete model numbers are normally used).
- Screen arrangements (including topology and connectivity).
- Local database requirements (sizes, contents and detection of momentary changes).
- SCADA database requirements (message formats, contents and frequency).
This information is used to build the substation-specific PRICOM databases and screens. In addition, the bill of materials reports are used to define the required protection relays, PLC and rack layouts. The SMT forms are read by the ABB PRICOM Generation Tools, and a complete database is generated for all relays and other IEDs. This database includes proper scale factors, limits and display conditions for all points in the database. A SCADA table is built that extracts appropriate data points from the database when a SCADA request is received or a SCADA command is executed.
Traditionally, the installation of a substation automation system required a field engineer to attend the substation site for the majority of the time taken to construct and commission the equipment. With the automated process developed by SCE, the configuration and testing of the ABB PRICOM system is virtually complete before the retrofit package is delivered to the site. As a result, SCE technicians are able to install each system with minimal on-site support from the utility’s technical staff. Typically, three to five staff days are required for the LAN and SCADA point-to point testing and commissioning for each installation.
Table 2 includes comparative data from SCE and ABB relating to the traditional and automated methods of defining and installing a substation automation system and provides substantial evidence to show that the automated design process SMT brings many benefits to both the utility (SCE) and the vendor (ABB).
Progress Report on the SCE Project
SCE’s original target to retrofit a large number of substations annually proved to be overly optimistic. SCE has now set a more manageable target of completed installations each year, a workload that requires a small team responsible for ongoing development of the tools, production engineering management and field technical support. An additional pool of contract resources is used to generate drawings and to design the interface of the SCE/ABB retrofit package with the existing substation. The substation automation retrofit program requires significantly less engineering and technical support using these automated processes than if the work were done manually.
The authors wish to acknowledge the technical support and contributions given by William Ackerman and Joseph Mazza from ABB Substation Automation Systems.
Charles Adamson joined SCE in 1981 as a protection and control technician working on the utility’s first automation projects. As these automation systems developed, Adamson became involved in the development of many of SCE’s automation PLC logic programs. Currently, as project manager of substation automation, he has written and presented a number of papers in this subject area at Relay Conferences, DistribuTECH, vendor and utility seminars. [email protected]
William Shelley began his utility career with SCE in 1970. After seven years as a protection and control technician, he left the utility to start his own company, S&W Technical Services Inc. He returned to SCE in 1985 as a substation engineer responsible for the development of some of the utility’s first PLC substation automation projects. Since 1995, Shelley has been lead the utility’s Substation Automation System Development Group. [email protected]
William Corbell started work in the power supply department (transmission/substation) with SCE in 1967. During his career, Corbell has held a number of positions in the utility and is now managing the Substation Modeling Tool (SMT), development of SCE’s master substation PLC program, Acceptance Test Procedures and future PRICOM/HMI applications. Corbell holds an AA degree in business/data processing, an AS degree in electrical engineering, and he is working on his bachelor’s degree. [email protected]