Utilities around the United States are under increased pressure to improve their processes for capturing customer interruption data. These data are used to calculate industry-standard reliability performance indices. In many states, utility commissions are implementing reporting requirements to ensure that utilities have systems and processes in place to report performance data on a regular basis and to identify system performance issues.

Otter Tail Power Co. (Fergus Falls, Minnesota, U.S.) is a small rural utility and doesn't have an outage management system, which is the basis for most utilities' reliability tracking systems. The company has 127,200 customers spread across 50,000 sq miles (129,500 sq km) in rural Minnesota, North Dakota and South Dakota.

Historically, Otter Tail Power has used an automated interruption monitoring system (IMS), which was implemented in 1991 to gather distribution interruption data at the feeder level. Once a month, each of Otter Tail Power's 12 operations centers would download the interruption data and import it into a cumbersome database that calculated the reliability indices for each operation center and the company collectively. Due to the age of the system and its associated technology, the system became impossible to maintain.

Updating the IMS

In the fall of 2002, Otter Tail Power began searching for an economical, maintainable replacement system that would meet current and future demands for reliability reporting, as well as offer value-added system operational capabilities. Otter Tail Power's system requirements were:

• Low cost

• Easy installation and maintenance

• Economical and reliable communications method

• Supportable system that avoids technical obsolescence over its useful life

• System should provide system data used in operational optimization, such as voltage metering and alarm/notification

• System should not be located on a customer's premises for maintenance purposes

• Historic interruption data should be maintained by a third party for security purposes and overall system integrity.

Two key objectives determined the capabilities required for the IMS. The main purpose of the new system was to provide accurate data so that performance reliability indices could be calculated as required by North Dakota performance-based rates and the Minnesota Public Utilities Commission or any other regulatory entities.

The second objective was to provide the interruption data needed to make operational decisions and prioritize future resources for maintenance and upgrade projects.

To conduct an industrywide search for an optimum system, Otter Tail Power formed a cross-functional team with members representing operations, area engineering, communications, metering/systems maintenance and strategic sourcing. This team developed the system requirements and specifications and studied the available solutions in the market. They visited several utilities that had recently installed interruption-monitoring systems or systems that used similar technologies. After several months of investigation, the team proceeded with a system provided by Telemetric (Boise, Idaho, U.S.).

The system used several Telemetric voltage monitors (TVMs) capable of reporting power interruptions and voltage conditions. It provided two-way communications using the non-voice or “control” channel of the public cellular network. A TVM was installed on each of Otter Tail Power's distribution feeders, immediately following the feeder breaker at the first 120-V voltage source (pole-mounted transformer).

The operating premise of the IMS system is that each TVM device has an associated feeder in the distribution system with a certain number of customers determined by CIS data. When an interruption is reported from a Telemetric device, the system assumes that all customers on the associated distribution feeder experienced the power interruption.

Software allows users to view interruption data online, using Telemetric's secure website. Reports also may be printed directly from the website, and all report screens can be exported into comma-separated value files that are easily imported into Microsoft Access, Microsoft Excel or similar software packages.

Communications Technology

The Telemetric system is based on the registration process for a roaming cellular telephone. A roaming cellular customer is defined as a customer operating outside of his or her local system. When a cell phone is initially turned on, it compares the system identification of its home system to the identification being sent to it from the local cell tower. If a match occurs, then the telephone is operating in its home system. If not, the cell phone illuminates its roaming light to alert the customer that roaming rates will apply. When the roaming cell phone registers with the visiting cellular system, it sends its identification numbers to the local cellular provider's database.

In Otter Tail Power's IMS, a Telemetric unit replaces the roaming cell phone. Rather than purchasing airtime from the major carriers throughout North America, Telemetric purchases its communications from a control channel provider, who negotiates excess capacity from the two major carriers in each cellular region. The process works just like the roaming cell phone example, except the registration call now contains the data being reported by the Telemetric device. The local switch recognizes that the radio is not one of its own cell phones and looks up its home market, which looks like another cellular carrier to the local switch. Once the data packet arrives, the information is decoded and routing information is deleted. Because the data packet is completely passed during the registration process, sending the message does not incur any long-distance fees and is sent within seconds. Data are then passed to the Telemetric Network Operations Center via a secure TCP/IP connection.

Once the data reach the Telemetric system, Otter Tail Power can view the data on the secure web server and generate alarms/communications based on changes in data. These alarms can be delivered via any cellular text-messaging device or via e-mail.

Project Implementation

Upon approval to proceed with the project, Otter Tail Power identified 730 feeders throughout its service territory for TVM installations. These feeders spread out over nine customer service centers in five areas across three states. Lead installers were identified in each of the service centers and trained in the basics of monitor installation, setup and troubleshooting.

Locations for installation were selected on the first customer pole-mounted transformer after the distribution feeder breaker. Installation locations were documented on the company's distribution prints.

Units were shipped at a rate of approximately 100 per week. Otter Tail Power prioritized its workforce and installed all 730 units over the course of two months. Post-project expense analysis recognized an installation cost of $95 to $197 per unit.

Follow-up investigations into the reasons for installation cost variability indicated that the greater the number of installers involved, the greater the cost. This is due to the “learning curve” that exists in which installers gain efficiency as they install more units. Total project costs equates to approximately $780 per unit or feeder.

Following installation, the installer tests and verifies the device's ability to transmit and receive information with a standard half-wave, 2.5-dB (rubber duck) antenna. If the signal strength is found to be weak, a directional, high-gain antenna is used to maximize signal strength and ensure proper communications. In the project, less than 1.5% of all locations required high-gain antennas. The Telemetric website displays the data communication signal strength when it posts device status following a state change communication. Other installation options included pedestal-mounted locations at pad transformers and inside metal enclosures in certain situations.

A rigorous system checkout was conducted using the status report capability from the website. TVMs that did not communicate during system tests were physically checked out for damage or installation problems and replaced if necessary. The installation and checkout processes went well, and the system was commissioned in early July 2004.

Reliability Reporting Software

Otter Tail Power wanted to use up-to-the-minute interruption data to calculate indices such as SAIDI, SAIFI, CAIDI and MAIFI so it could quickly run reliability reports. The requirements for reliability reporting included the following items:

• Ability to run reliability performance reports by state, area, customer service center or individual feeder.

• Capability to “classify” interruption cause and add notes describing cause and follow-up in greater detail for operational optimization and follow-up investigations.

• The ability to exclude certain interruptions from indices calculations such as major events and planned maintenance activities.

• Appropriate system security provisions to allow for all employees to access interruption detail reports and appropriate office personnel to classify interruptions and run summary reports.

• Use an external resource/entity to ensure interruption data are secure, backed up and at the highest level of integrity.

• Report screens' data export capability via Comma-Separated Value (CSV) file that is easily imported into Microsoft Access, Microsoft Excel or similar software packages for further analysis and reporting.

System Benefits

Otter Tail Power has already realized benefits in the areas of system optimization, resource prioritization, problem alarming and notifications, system maintenance communications and power-quality analysis.

System optimization

The company has been able to use the new IMS to identify system issues and make required fixes. Individuals can look at current and historic data on the website for any of the system feeders.

Excessive voltage level alarms have been used to identify problems with voltage regulators. Locations that experience an abundance of momentary interruptions are followed up with the appropriate inspections to investigate vegetation management needs or other system issues requiring service. Since installation and commissioning, the company has added automated alarming and notification features to improve operational efficiency.

The system allows for the calculation of common reliability indices such as SAIDI, SAIFI and CAIDI for any block of time and any region in our entire system. Data are near real time and can be accessed from anywhere there is an Internet connection.

The system also tracks MAIFI, which is important for our large commercial, industrial and institutional customers. These reports also have been used to identify line sections where follow-up inspections and maintenance are required.

Resource prioritization

The interruption monitoring system will allow for an objective analysis of our distribution systems and its respective performance and condition. This data will be used to identify areas where capital resources should be prioritized and deployed. It also assists in forecasting the areas where equipment replacement and maintenance are needed.

Problem alarming and notification

Several individuals in the customer service areas are currently using the alarming and notification capabilities of the Telemetric system. They respond to e-mail notifications (example below) when a feeder experiences a sustained interruption:

Device 5910 LOUISBURG JCT - NORTHWEST FEEDER has experienced an interruption. Please contact the appropriate CSC to update the interruption.

For off-hours notification, individuals are set up to receive text messages on their cell phones indicating the time and location of the interruption. Currently, the reliability engineer, area engineering and individuals in the operations department are receiving notifications. Certain situations (excessive interruptions for a particular number of customers) that require immediate communications with appropriate regulatory folks are also captured and communicated to the reliability engineer and members of the regulatory reporting department for immediate follow up.

This process will continue to be refined as the system matures and more experience is gained with its capabilities.

System Maintenance Communications

The system has several features that provide essential data on the operation of the devices in the field and subsequent maintenance required.

• Missing device report: This report displays any and all devices that did not call in with their scheduled status call during a preset interval by the user. Devices showing up on this report are sent a status report request. If they still do not respond, an appropriate individual in the field is contacted and scheduled to provide an on-site inspection and make the appropriate fix.

• Low or dead battery reporting: The Telemetric voltage monitor has internal diagnostics that tests and measures the strength of the onboard battery every seven days. If the battery is found to be inadequate, an email is generated and sent to the reliability engineer indicating the unit and location. Appropriate individuals are again scheduled for follow-up maintenance following these notifications.

Power-Quality Analysis

Otter Tail Power's Technical Service Group is now using several three-phase monitors as power-quality analysis tools. The application of these units is considered part of a separate system when compared to the 730 units being used for interruption monitoring. The application of this tool in larger commercial, industrial or institutional customers' locations where power-quality issues reside has provided an excellent way for gathering data used in resolution of problems.

Future applications of this tool for power-quality analysis will continue to grow as experience is gained with the system and its capabilities.

Summary

The Telemetric interruption monitoring system has proven to be a cost-effective solution for fulfilling Otter Tail Power's original project objectives — reporting and system optimization. Reliability data are currently being collected that will be used to report required reliability indices to utility commissions in the future. Notifications of all sustained interruptions are communicated to appropriate individuals, allowing for optimized response timing for system problems that arise. Interruption classifications are also input into the system at the customer service level supplying useful data to be used to prioritize resources and capital in the future.

The system also has provided employees with a real-time tool to monitor reliability performance and indices throughout the entire service territory. This system has enhanced the company's awareness of reliability and provided a method for tracking performance easily and effectively.

Rod Jensen has 23 years of manufacturing, energy services and utility experience with 3M, Imation and Otter Tail Corp. His areas of focus have included: process control design, large capital project management, construction coordination, process optimization, product design/implementation and facility management. He received a BSEE degree from the University of North Dakota and is a licensed professional engineer in Minnesota, North Dakota and South Dakota. rjensen@otpc.com