In an effort to provide industry-leading customer service , TXU Electric delivery (Dallas, Texas, U.S.) has set an objective for achieving top-decile performance in system reliability by the end of the decade. The accelerated integration of technology into the delivery network will be a key enabler in achieving this goal. TXU Electric Delivery's recent commitment to a comprehensive deployment of broadband over power line is one example of the initiatives TXU Electric Delivery is pursuing in support of this strategy.

The large-scale application of distribution automation will be a major component of our technology strategy. TXU Electric Delivery has used distribution automation in one form or another since 1992. In fact, the automated distribution system at the Dallas-Fort Worth International Airport was among the industry's first large-scale installations.

While there have been several automated projects over the past years that have provided a lot of knowledge, most of these projects were basically remote-control schemes. Some of these were concentrated on a group of feeders for reliability, while others were spread out to provide a specific load-switching function. TXU Electric Delivery has continued to evaluate new distribution automation technologies to optimize reliability and improve customer satisfaction. In fact, in 2004, TXU Electric Delivery installed six S&C IntelliTEAM-II switches in an established neighborhood of Dallas. These switches are different from all of the utility's previous automation initiatives in that they are intelligent devices that incorporate a mesh radio network that allows them to continuously “talk” to each other, share information and make intelligent decisions.

AUTOMATION STRATEGY DEVELOPMENT

In 2002, TXU Electric Delivery created a new asset management group called Operations & Maintenance Strategy to focus on evaluating system reliability and developing maintenance and automation programs that would improve system reliability. The two primary metrics used to measure feeder circuit reliability are the system average interruption frequency index (SAIFI) and the system average interruption duration index (SAIDI). SAIFI indicates how often the average customer experiences a sustained interruption over a predefined period of time, while SAIDI indicates the total time an average customer has power interrupted during a predefined period of time. SAIDI is commonly measured in customer minutes of interruption per year.

The first two years were spent expanding the maintenance programs, evaluating the existing remote-controlled supervisory systems and learning about various automation systems that were available.

AUTOMATION PILOT PROJECT

TXU Electric Delivery encountered the S&C Electric IntelliTEAM-II product for the first time at the 2003 IEEE PES T&D Conference in Dallas. Enough interest was generated that meetings were held to review the system and determine the cost versus overall benefits. In 2004, TXU Electric Delivery initiated a pilot project to install automated switches on one feeder. The objectives of the pilot were to gain experience with fully automated switches, measure reliability improvements, evaluate automation maintenance requirements and evaluate dispatcher interaction with the product. A plan was developed to select a test area. An investigation to select the appropriate feeder included the following criteria:

• Two-year history of feeder-breaker lockouts (less than five minutes; more than five minutes)

• Two-year history of feeder reliability (SAIDI and SAIFI)

• Established area with no anticipated load growth

• Full backfeed capabilities on adjacent feeders

• No existing distributed generation resources.

The reliability data, especially the feeder-outage data, was the first filter used to select potential feeder candidates. These feeders were given to the distribution planning group to rank as strong, moderate or weak. The combination of these evaluations provided a list of potential feeder candidates. The feeder selected was White Rock 0001: a 13.2-kV feeder 14.6 circuit miles (23.5 km) long, but with only 3.4 feeder miles (5.5 km) of primary backbone. This feeder serves more than 2200 residential customers and is located in an established Dallas neighborhood, densely populated with large trees.

Distribution planning evaluated the feeder to assist in selecting the optimum number and locations for the switches. The plan was developed to install six switches along the feeder and at tie points between two adjacent feeders. This would allow the feeder to be split into three separate sections (Fig. 1). The adjacent feeders cannot pick up the entire feeder, but there is sufficient capacity to transfer a third of the load through each tie point.

AUTOMATION EQUIPMENT

The S&C Electric Omni-Rupter and ScadaMate switches were currently in use in the distribution system. A cost-benefit analysis was performed comparing the switches to determine which to use in the pilot project. The goal was to choose one switch for all automation projects.

TXU Electric Delivery decided to use the ScadaMate switch for the following reasons:

• Long-term reliability associated with totally enclosed (SF6) operation

• Less concerns due to weather (such as ice)

• Visual open indication for the personnel performing restoration or maintenance activities and it cannot be closed remotely or automatically

• Higher switch fault-closing duty cycle.

SWITCH/SCADA COMMUNICATIONS

The IntelliTEAM-II system communications use UtiliNet peer-to-peer radios with spread-spectrum frequency-hopping capabilities. The radios hop on a predetermined pattern (240 channels) without repetition for five minutes. They operate in the 902-MHz to 928-MHz frequency range and do not require a license. The radios operate with “line of sight” functionality that is designed to communicate up to 5 miles (8 km). With trees and other obstacles, the switches installed on the TXU Electric Delivery system are typically 0.25 miles to 1.5 miles (0.4 km to 2.4 km) apart.

One switch control communicates back to the SCADA Master using a CDMA/1×RTT cellular modem. It communicates the status points of all switches it interacts with to the SCADA system at our operating centers. Dispatchers use the SCADA system to monitor the automated switches, disable the automation and manually operate the switches (Fig. 2).

SWITCH RADIO SURVEY

Distribution planning identified the general switch locations based on load and backfeed capabilities. More work was needed before the work request could be designed. A field inspection and radio survey was performed. Planned switch locations were evaluated and slightly moved for better radio communications. The switch movement was based on installing the switches in bucket-truck-accessible areas and not creating a difficult installation on any pole.

Temporary radios were hung at the proposed switch locations and the radio network was tested. The RSSI (signal strength), Tick percentage (ability to match frequency hopping pattern) and Dack percentage (ability to transfer data) parameters were measured and evaluated using standard UtiliNet acceptance criteria. The direction of the antennae was noted for future work-request installation instructions.

The radio signal path is plotted on contour maps and physical items such as buildings, signs, trees and communication towers that could affect communications are noted (Fig. 3). One lesson learned was to do the radio survey when leaves are on the trees. This eliminates summer communication surprises from winter surveys.

WORK REQUEST DESIGN

Switch installation required more detailed instructions than normal installations. Specific instructions for the work-request designers were created. A few changes in process occurred before the instruction map in Fig. 4 was developed for use. It provides instructions for the designer to use such as antenna direction, the direction to face sensors on the switch and pole-replacement recommendations.

A lead protection and control (P&C) technician became the technical expert on the pilot system. He worked closely with the crews performing the switch installations. Crews were used to working autonomously and several training sessions were held. Initially, the crews did not realize that small things such as changing an antenna direction caused communication problems. One switch was installed with the sensors facing the wrong direction. It was a learning experience for everyone involved. Equipment installation standards have been updated. Installation of a ScadaMate switch and a radio repeater are shown in Fig. 5.

SAFETY

Safety was a top-priority issue during the planning stages of the pilot project. The dispatchers were not experienced with new switches that automatically operated to isolate a faulted section. The restoration resources were not experienced working with switches that operated without dispatcher intervention. Several meetings were held with safety committees, operating center personnel, restoration personnel and construction crews. The Safety Handbook was reviewed to ensure it covered safe work practices related to working on automated equipment.

Safety training was a major part of the training that occurred with all groups who would be working with the first IntelliTEAM-II system. This included the troubleshooters, distribution operating technicians, linemen, supervisors, safety representatives, dispatchers and P&C technicians.

The dispatchers were trained just prior to the new system being fully implemented. This provided an opportunity to look at the switches added to the SCADA system and become familiar with them while the training was fresh on their minds. As with all such programs, training is ongoing to keep all groups updated and refreshed on the operation of the new technology.

SYSTEM COMMISSIONING

The switch installations were tracked to keep the pilot program on schedule. S&C Electric was scheduled to work with TXU Electric Delivery personnel to field check the switches and radio communications after the final installation and commission the system (Fig. 6).

SCADA MASTER

After system commission, the next step was to install the digital cellular modem that links the system to the SCADA Master at the dispatch center. The new SCADA screens were developed and tested. The system was not fully automated until the dispatchers were trained on the system display on the SCADA Master. The system became fully automated in 2005.

There was some time lapse between the switches being installed and being fully functional on the SCADA Master. Some lessons were learned about the SCADA system. The original SCADA software was purchased in 1998 for the control and monitoring of underground switches at various critical locations. During the next five years, overhead remote-control switches were added to the system and no problems were encountered. That changed. The SCADA software had limitations that were revealed with the expanded number of new switches. A new SCADA system was developed and deployed. Some features were added to the SCADA to customize it to the logic pertaining to the new switches. SCADA control screens were created to look like the field controls to simplify communication between dispatchers and field technicians when dealing with new equipment.

CYBER SECURITY

Cyber security was a priority on this project. Appropriate cyber security steps were taken as experience has shown that hackers will try to obtain access to switches.

RELIABILITY PERFORMANCE RESULTS

Now that the first switches are operational, it is time to monitor their performance. Reliability was expected to improve in two ways. First, the sections of feeders that are not faulted should be restored quickly and improve SAIDI or SAIFI. Second, the crews can be more accurately dispatched and not spend as much time looking for the fault.

Reliability improvement related to the switches cannot be measured by feeder overall performance. Items such as the recent trimming of this feeder will positively improve feeder reliability without any support from the new switches. The best way to measure the reliability performance attributed to the switches is by manually capturing each switch operation and calculating the number of customers restored before the crews restore the balance of customers. The IntelliTEAM-II switches have operated on 12 separate occasions and have saved 184,576 customer minutes. The number of outage minutes customers experienced in 2005 (as of Nov. 1, 2005) by the three feeders was 344,109. Without the switches, customers on these three feeders would have experienced a total of 528,685 outage minutes. This equates to a 35% reduction of customer outage minutes for these three feeders due to the 12 switch operations.

EXPANSION

In 2005, the installation of 53 switches on additional applications was approved. The same criteria were used to select feeder locations. These were selected along with scattered feeders primarily across the Dallas — Fort Worth metroplex (Fig. 7). The feeders to be automated are highlighted with various colors. The strategy on feeder selection continues to evolve, and it has become a two-pronged approach. The program needs to meet reliability improvement targets. Worst-performing feeders with high feeder lockout numbers will continue to receive selection priority, but building automation areas has a long-term benefit. Both of these thoughts have been built into the 2006 Automated Switching Program.

The initial results with IntelliTEAM-II are very successful. The pilot project met the projected reliability improvement targets. Continued monitoring of reliability performance will confirm whether the distribution automation strategy is satisfying the customer service and reliability goals. The early success of this program has led to its being expanded in 2005 and again in 2006.

Alan Bern is manager of operations and maintenance strategy in distribution asset management for TXU Electric Delivery. During his 25 years with TXU Electric Delivery, he has held a variety of positions dealing with maintenance, reliability, operations, work management and automation. Bern received a BSME degree from Texas Tech University and is a professional engineer registered in Texas. Abern1@TXUED.com

2005 ScadaMate Switch and Control Status

Link to Document
Click link above for 2005 ScadaMate Switch and Control Status table.