Reliability planning analysis at the Salt River Project (SRP, Tempe, Arizona, U.S.) prioritizes geographic areas for preventive inspections based on a cost benefit model. However, SRP wanted a new application system to prioritize inspections and to predict when direct buried cable would fail using the same cost benefit model.
In the business cases, the represented type of kilowatt load — residential, commercial or critical circuit — determines the cost benefit per circuit. The preferred solution was to develop a geographical information system (GIS) application allowing for a circuit query for the specific geographic areas it crosses and the density of load points of a given type within those areas. The query returns results based on the type of equipment analysis execution: wood pole, preventive maintenance for a line or cable replacement. This differentiation insures that all the facilities relevant to a specific analysis type influence prioritization of the geographic areas.
|Number of transformers||approximately||123,000|
|Number of switches||approximately||22,100|
|Number of capacitors||approximately||2,450|
|Number of feeders||approximately||1,030|
|Number of substations||approximately||180|
|Number of poles||approximately||144,000|
The query executes through the GIS-based application RAMS (Reliability and Asset Management System). The application requires an extract of customer data containing specifics about customer type and kilowatt load. This customer data is keyed to the circuit database through the transformer quarter-section codes (traditional mapping sections), producing information about the customers and demand types for individual transformers/circuits. This procedure allows for querying a circuit based on its geographic area and load types. For wood pole and preventive-maintenance line analyses, a prioritization occurs for the geographic areas based on the highest priority circuit occupying the area.
Scope of Utility and Service Area
Determining the need for the investment in the GIS illustrates the importance of outlining the magnitude of the infrastructure maintained by the utility. The table (page 46) summarizes the quantities of candidate equipment managed by the computer application.
RAMS GIS is SRP's approach to determine the value associated to damage or failure of distribution or transmission structures and their related equipment. The general nature of reactive maintenance puts the utility in the position where a storm can leave thousands of customers without power.
The unique capabilities of a GIS allow for the mobilization of dispatchers, troubleshooters, line crews, customer service representatives, media representatives and many others normalized by the implementation of a work flow and data capture process.
Utilizing another perspective — addressed toward the availability of limited resources — is how RAMS GIS helps determine the best use of the limited capital resources.
RAMS is an evolving, growing integrated set of applications that provide a spatial view of the existing and planned work, as well as support for the inspection of various power system components such as wood poles, street lights and other devices routinely inspected using infrared technology.
The RAMS system provides predictive analysis and prioritization related to cable failures and associated replacement. Both analysis types either interface to the work management or extract data from customer information services systems. These tools provide significant improvements to the preventive-maintenance process that ultimately improves system reliability.
SRP's RAMS application consists of a GIS platform, a work order system and an Intranet Web-based application. The GIS provides all the printed map functionality, analysis capability and data capture components. The work order system is a stand-alone system leveraged by the GIS using ODBC connectivity. The Web application provides an interface to collect data about equipment inspections. The Web component is an extension of the GIS and interfaces directly with its databases and objects.
Query results remain available for later recall. The resulting analysis objects store in the GIS database capturing the analysis information. The information can be viewed through a standard reporting interface (RAMS Reporting Tool) and the GIS Object Browser.
Wood Pole Prioritization
To minimize the impact of high winds, SRP is accelerating its efforts to inspect and maintain its wood poles. Over 10 years, the utility anticipates spending US$22 million to complete a single pass through of “wood pole inspections” for its transmission and distribution lines. It will inspect, preserve or replace the 130,000 plus poles in its transmission and distribution system. Currently, crews are inspecting about 10,000 poles each year.
RAMS is built on a GIS platform and provides a single spatial application that consolidates and integrates various stand-alone processes. Previously, each department worked essentially in a vacuum, meeting the department's local needs. Occasionally, a conflict arose between other groups for resources and the repeat inspection of certain facilities. Before RAMS, there was no means of viewing what the other departments were doing in regards to inspections, prioritization of work and submittal of work orders.
RAMS provided consistency in the work order process among various departments. This program eliminated duplicate inspection efforts and ensured no multiple work order efforts.
In the wood pole and line inspection prioritization process, emphasis surrounds a 10-year inspection cycle. Therefore, predictive analysis is not used and preventive analysis is performed. This ensures the inspection results determine the likelihood of any individual piece of equipment failing. Given that approach, more kilowatts on a facility equals higher priority for inspections. Subsequently, the GIS will maximize the efficiencies of the fieldwork by logistically grouping these activities into quarter sections. In the past, an inspector could be physically close to other equipment that a schematic approach did not reveal as needing inspection.
Direct Buried Cable Prioritization
Much of the electric system that serves SRP's more than 730,000 customers is underground. SRP increased funding to its underground cable replacement program — allotting US$100 million over six years to replace damaged cable.
Underground electric systems offer many advantages, because they eliminate power poles and overhead electric lines in residential areas. However, one drawback resides in the area of repair and replacement. Over time, underground cable will fail for a variety of reasons: moisture, electric load, overvoltage or physical damage.
Until recently, solving most residential cable problems required excavation or trenching. This procedure is costly, it disrupts landscaping and pavement, and it is not popular with customers. Consequently, SRP's concentration is on fixing the cable installed in the 1970s. In selected areas, the utility uses an alternative to trenching, a process called cable cure.
In the SRP's service territory, 1970s vintage direct buried cable is failing sooner than anticipated. Annual budget constraints do not allow for replacing direct buried cable with cable in conduit before it fails. Therefore, actions were taken to determine where the utility would get the most overall benefit when deciding which cables to replace.
SRP determined that to provide the best return in terms of reliability, RAMS needed the ability to calculate the predictive customer interruption cost for all direct buried primary conductors. SRP bases the prioritization of cable replacement activity on outage cost, failure rate, probability of failure and the return on investment. The line maintenance-engineering group of the SRP performed extensive research to determine the predictive algorithms.
Menu-driven tools developed in the GIS application allow the user to preprocess the values the predictive algorithms generate. These values are assigned to a new object, which shadows the object of a “primary conductor” represented spatially on screen as a conductor route. A reporting tool allows a query of the results and sorts the appropriate values for the analysis.
Work Order Processes
Using menu-driven interfaces, the GIS technician interfaces with a work order system and creates a work order. This “inspection” work order is homogenous to other types of work orders, except its “facility” is the map quarter section.
The GIS spatially determines all the candidate equipment located within that quarter section. The GIS creates a relationship between the work order and all equipment. The GIS then identifies all other open work orders in the quarter section allowing the discretion of the GIS technician to pull equipment from the inspection punch list.
This coordination of workflow between GIS and work order eliminates the duplication of inspection and other facilities-related activities. For example, an inspection does not have to take place on a piece of equipment scheduled for replacement. The GIS automates a mapping process to produce a large-scale printed map for the field inspectors.
The results of the field inspections — problems found or not found, type of problem, suggested remedy — are input into the GIS in one or two ways, depending on the type of inspection. For instance, inspection data records into a hand-held device when contract personnel complete a wood pole examination. Data uploads to the GIS via a data dump from this device. Whereas, for an infrared inspection work order, inspectors mark field findings on a map product. Data is entered into the GIS through a custom Web application. Other users of the system may query the data for “exceptions” — problem locations and action items. These inspections may relate to one or more maintenance work orders. The exceptions are the by-product of an automated validation process that looks for completeness of data, duplication of data, and mismatched data (data for facilities not related to the work order). As a by-product to these activities, paper maps and field verification processes allow a feedback mechanism for GIS data integrity to be checked.
Finally, the inspector uses a Web-based tool for entering the inspection results back into the GIS. At this time, the GIS technician uses the results to create additional equipment based work orders. This process identifies the problems with equipment in the field, checks the integrity of the GIS data and puts the work orders in place. The inspection results capture activities performed on the spot by the inspector to fix a problem. The inspector submits a redlined version of the paper map to a mapping technician to provide an additional data integrity check, which may result in corrections to data contained in the GIS.
Integrating GIS with work order connectivity is a success with the working groups at Salt River Project.
Anthony Villocino is a GIS senior programmer analyst at Salt River Project. He is responsible for migration of GIS computer applications across ESRI and Smallworld platforms. He holds the BA degree in environmental studies from California State University, San Bernardino, California.