The Asset Management Department of Power Delivery is focused on the life cycle management of ATC’s transmission assets. The program objective is to ensure assets perform the required function in a sustainable manner, at the lowest whole life cost without compromising health, safety, reliability or environmental performance.

The coordination of design, commissioning, operation, maintenance and replacement strategy is necessary to achieve this objective. Asset renewal is the “replacement strategy” piece of the asset life cycle. Asset renewal is driven by public and worker safety, regulatory compliance, reliability performance as defined by criticality, and environmental stewardship.

State of the system

ATC benchmarks its transmission line performance with 27 other transmission operators across the United States. This comprises 54 percent of the transmission grid based upon NERC bulk power mileage. In 2009, ATC lines rated 345 kV were in the second quartile for reliability performance. ATC lines operating at 115 and 138 kV were in the top decile and ATC 69-kV transmission lines were top quartile for reliability performance. As evidenced by reliability data, our lines are generally performing well. However, significant investment will be required to maintain reliability as a number of facilities have been identified as nearing end of life or having components at end of life.

ATC operates a fleet of 175 transformers, and 40 percent of these were installed prior to 1975. We have not experienced a high failure rate of these aging transformers but our Assessment anticipates an investment to maintain reliability and manage risk.

Our protective relay systems are critical to the safe and reliable operation of the transmission system. We plan to continue to modernize our relay systems to improve operational information, minimize inadvertent operation, and increase the speed of restoration when an outage occurs.

ATC has a fleet of 1,850 circuit breakers. Of these, 1,100 use sulfur hexafluoride (SF6) as an arc quenching and insulating medium. The remaining circuit breakers are oil circuit breakers. Asset renewal, as applied to circuit breakers will target units that have specific reliability problems and SF6 circuit breakers that have environmental issues.

Our asset renewal plans for the 10-year horizon have an estimated cost of $750 million. Please note that this dollar figure includes both asset renewal and protection projects. Also refer to the 2009 Asset Renewal Financial Table for costs of specific asset renewal projects outlined in this Assessment.

Transmission Line Asset Renewal

Overhead transmission line facilities

The Asset Maintenance group of ATC monitors the overhead line facilities through a maintenance and inspection program designed to assess the condition of line facilities to maintain public and worker safety and reliability performance. ATC Operations and Asset Management personnel monitor the reliability of all our lines. Aerial surveys are performed to improve the facility information and to confirm ratings capability. The inspection, reliability performance and aerial survey programs are the initial drivers for considering asset renewal upgrades to a facility.

Once a line shows condition or operational history indicating it may not perform the required function in a sustainable manner, discussions with Planning begin to determine what system reliability needs may exist for this line or geographic area. The line is analyzed for structural- and clearance-related issues to complete the list of possible drivers. If Planning and Asset Management both have drivers for a project, a primary need driver is agreed upon and the project progresses as a network (Planning driven) or asset renewal (Asset Management driven) project.

Asset renewal transmission line project scopes will vary from complete rebuilds to replacements of problematic elements (poles, cross arms, insulators). The extent of renewal driven work is determined by line criticality and customer impact. When a decision is made, net present value (NPV) analysis may be used to evaluate various options and determine the least cost means of maintaining the required reliability.

Underground transmission line asset renewal

Our underground transmission system consists of high pressure fluid filled cable systems (HPFF), High Pressure Gas Filled cable systems (HPGF), solid dielectric cable (SD) systems and self contained fluid filled system (SCFF).

The condition of high pressure fluid and high pressure gas filled systems is such that no investment is expected in the 10-year horizon. Several of the solid dielectric cable installations are approaching end of life and will require replacement and are included in the ten year plan. The self contained fluid filled cables between upper and lower Michigan are expected to reach end of life near the end of the 10-year horizon.

Asset renewal investment is anticipated for the transmission line facilities identified in

Table AR-1. Scopes described may be modified as the scope development is refined. Our plan to maintain safe transmission line facilities and improve reliability performance over the 10 year horizon is approximately $400 million.

Transformer Asset Renewal

The intent of the transformer asset renewal program is to make an assessment for each transformer in the fleet based upon condition, criticality and the probability of failure. This assessment is used to determine a spare or renewal strategy such as a site spare, system spare, or renewal candidate (Please refer to Figure AR-1).

• Healthy units with high criticality and high probabilities of failure based upon age may warrant site spares or a system spare in the area to minimize transport times.
• Units with poor health, high criticality and high or low probability of failure based upon age are candidates for renewal.
• Healthy units with low criticality and a low or high probability of failure based upon age will be backed up with a system spare.
• Units with poor health and low criticality will be backed up with system spares regardless of the probability of failure based upon age.

Condition is monitored as part of the asset maintenance program through off-line electrical tests, on-line oil tests, infrared inspection, vibration analysis and acoustic condition assessments.

The criticality of a particular transformer to the network is based upon a series of planning studies that look at the severity of the contingencies following the failure of a unit. Given the long lead and transportation times for auto transformers of the size used by ATC, these double-contingency studies provide guidance for the operation impact.

A fleet approach has been taken to estimate the investment in the 10-year horizon and for consideration in determining the number of system spares. The fleet approach uses a curve that represents 50 percent of transformers will fail by age 50 years. A probability of failure for each unit is determined from the curve and aggregated for each year in the 10-year horizon. Assuming a level aggregate probability of failure equates to the existing level of reliability, the expected investment will be approximately two 138/69-kV transformers per year in the 10-year horizon. For 345/138-kV transformers, the expected investment will be one transformer every two years. The cost estimate for this program over the 10 year horizon is $140 million. Actual replacement will be based on the results of our condition monitoring program and assessments of criticality. Please refer to Table AR-2 for details.

Relay Asset Renewal

Relays are the cornerstone of a reliable transmission system. The goal of the ATC relay asset renewal effort is to improve relay performance, provide information for operations, and reduce maintenance cost. We are able to improve relay performance with microprocessor based relays by eliminating over-reaching while maintaining adequate back up protection. The improved performance of the microprocessor relays allows us to increase system reliability and security via the expanded use of carrier and fiber optic communication. The newer technology has better factory support and we are able to minimize the risk of relay failure due to availability of spare parts and minimize repair times due to lack of factory support or software upgrades. Additionally, we are able to replace relay systems that limit line ratings.

Microprocessor based relays offer valuable information for operations. System operations is able to direct field resources to the problem area of a line based upon fault location information provided by the microprocessor based relays. Additionally, fault location information is used with the lightning detection network to correlate lightning strikes with line outages. This enables us to  direct patrols to sites of potentially damaging lightning strikes and detect problems that  occur during lightning storms that are not lightning related.

The self check and remote monitoring capabilities of microprocessor based relays allow longer maintenance cycles and reduce costs.

Approximately 12,000 relays protect our network. The asset renewal program is prioritized by replacing the least reliable relays by type and relays at end-of-life and relay locations with schemes that have a higher inadvertent operation history. This includes single relays that require remote back-up, electromechanical relays that do not provide fault location, do not self alarm and have a higher tendency of inadvertent operation than microprocessor relays. In addition, obsolete schemes without spare parts availability and/or no technical support from vendor are targeted. Other asset renewal candidates are relay schemes that limit loading or use only directional over current elements that increase coordination complexity and raise the likelihood of inadvertent operation.

ATC plans to spend approximately $130 million for relay renewal in the 10 year horizon. This equates to about 40 relay panels per year. Please refer to Figure AR-2 for details.

Circuit Breaker Asset Renewal

Circuit breakers are essential to the reliability and safety of the network. We own and operate over 1,850 gas and oil circuit breakers. The goal of the circuit breaker renewal program is to improve reliability and environmental performance by reducing maintenance outage requirements (duration, # of outages) thereby increasing availability, reducing SF6 emissions, and increasing safety by reducing the number of unplanned eventful outages. Our plan to maintain the safety and improve the environmental performance of our circuit breaker fleet over the 10 year horizon is approximately $80 million. Please refer to Table AR-3 for details.