Aclara has published a white paper, “Evaluating Total Cost of Ownership Models When Choosing Advanced Metering and Communications Networks,” that emphasizes the need to evaluate the total cost of ownership (TCO) rather than focus on the cost of initial implementation when selecting advanced metering and communications networks.
The white paper is based on interviews as well as regulatory filings and other publically available information gathered by the Wired Group consultancy. The Wired Group provides objective and independent analyses of the technological advances, customer expectations and environmental issues facing distribution utilities.
The research indicates that:
- The choice of the meter communications network has significant impact on the total cost of ownership (TCO).
- Point-to-multipoint networks may offer the lowest TCO when compared with the alternatives of mesh, drive-by and manual networks.
- The meter communications network chosen by a utility impacts future capabilities, with point-to-multipoint networks offering a robust platform for additional smart infrastructure solutions such as load control and distributed automation that enable utilities to optimize networks and enhance the level of service they provide to customers.
“Taking a long-term, macro view of both costs and the robustness of the communications network are key points for utilities to consider when choosing an AMI solution (planning the future of their networks). One can assess the true costs of an AMI network only by evaluating the total cost of ownership over the network’s lifetime. While not insignificant, implementation costs over the first couple of years paint only part of the picture, whereas the network configuration plays the major role in the lifetime operating costs that the utility needs to assess,” said Kumi Premathilake, Senior Vice President Advanced Metering Infrastructure.
Comparative CAPEX and OPEX of Network Types
The white paper discusses comparative capital and operating expenditures of point-to-multipoint, wireless mesh, drive-by and manual read network configurations. A model illustrating TCO over a two-year deployment period followed by a 15-year lifespan shows that point-to-multipoint networks have the lowest TCO of the four configurations, largely because of the dramatic reduction in operating costs, which are less than half that of manual networks and significantly less than operating costs of mesh or drive-by networks.
The Effect of Network Selection on Ongoing Costs
The Wired Group found that, according to utilities, one differentiator between mesh and point-to-point network configurations was that mesh networks must re-create pathways to access points after an electric outage. This process can require a few hours to a few days to complete once electric service is restored, during which time the meters which have yet to reconnect with an access point are unreachable.
This is an important consideration because a major impact on utility costs and operations involves service orders, such as disconnects and reconnects for service changes, which must be carried out manually for meters that are temporarily unreachable. Effects can be seen in service order completion rates, which are generally lower for utilities using mesh rather than point-to-multipoint networks.
In addition, manual service orders increase when manual reconfigurations and/or field device adjustments must be made to reconnect some meters to mesh access points after pathways are automatically reconnected after outages.
Some utilities using mesh networks also report that meter pathways that had been purposely established by network engineers – for example, to balance access point data loading – become unraveled as the meters automatically re-establish pathways after an outage.
Network Selection and Outage Management
The white paper suggests that point-to-multipoint networks may integrate outage reports from meters into their outage management systems (OMSs) better than utilities using mesh networks. One-on-one interviews indicate that point-to-multipoint networks are less likely to become overwhelmed, and fail, when thousands of meters report an outage simultaneously than mesh networks.
Though bandwidth increases in networks are possible with increased capital investment, this could be the reason why utilities with point-to-multipoint networks are more likely than others to utilize their meters’ “last gasp” capabilities in their outage management systems.
The implications for customers and utilities go far beyond outages. There are several situations in which a utility or third-party energy manager might want to communicate with thousands of meters simultaneously. Utilities using meters as gateways to customer energy management systems might want to communicate instructions to loads through meters during demand response events, while third-party energy managers might want to access thousands of customers’ usage data in near-real time to determine which load management actions to take during high cost periods. Networks incapable of handling thousands of simultaneous communications could not complete these functions.
The researchers found that utilities using point-to-multipoint networks may be more likely to use those networks to communicate with non-meter distribution devices, such as switches, reclosers, capacitor banks, sensors and other devices, than utilities using mesh.
Meter Data and Distribution Automation
In its research, Wired Group also found that utilities using point-to-multipoint networks were more likely than those using other types of fixed networks to use meter data in distribution automation applications such as integrated Volt/VAR control. When in use, most integrated Volt/VAR control applications require continuous, near real-time data feeds on voltage and power factor conditions from thousands of distribution grid endpoints. Interviews found that utilities with mesh networks often use line sensors rather than meters to provide voltage and power factor data, and use distinctly separate distribution communications networks to monitor these devices.
Reaching Hard-to-Reach Meters
Meters in rural areas, as well as meters located below grade or deep within large structures, present challenges to most meter communications networks. However Wired Group researchers found these issues were most frequently mentioned by utilities that had deployed mesh networks. While utilities described addressing these issues through the use of meter data repeaters and range extenders, such solutions entail greater initial costs. Such solutions also represent additional points of potential failure that could conceivably impact network reliability, though adverse impact on network reliability was not detected in reported meter read success rates.
The Wired Group’s study comprised several steps including evaluation of the experience of both for-profit and non-profit utilities regarding various types of deployed meter communications networks; examination of technical product specifications available from suppliers of various meter communications network types; and interviews with investor-owned utilities, municipals and rural electric cooperatives ranging in size from 30,000 to over five million endpoints. The full white paper is available for download on the Aclara website, www.aclara.com.