AMI and realising the distribution smart grid


By David G. Hart and Ron D. Pate

Many electric utilities are deploying or planning to deploy smart grid technologies. For smart grid deployments, advanced metering infrastructure (AMI) offers exciting opportunities for new smart grid applications. This article explores several important AMI considerations for the smart grid, exciting AMI applications yielding true smart grid benefits, and trends that will impact AMI systems going forward.

A well thought out AMI system has the following basic elements. 

  • Multi-utility solution – The AMI infrastructure must provide a complete solution to utilities with electric, gas and water meters. This allows the utility to implement improved customer service and operations for its customers without deploying a redundant infrastructure for gas and water.
  • Smart meters – There are two approaches to smart meters – keeping the customer meter data in the meter and transporting it over the AMI network or computing the meter data in the communications module. To avoid concerns over billing data accuracy all meter data, including consumption data as well as interval and time-of-use data, should be computed in the meter itself. This approach provides an enhanced ability for the utility to audit the billing data received through the AMI system, and ensures that the communications module firmware can be updated without potentially altering metering data. 
  • Multi-technology solution – A key to successful smart grid implementation is that the AMI solution provides a multi-technology framework that can adapt to emerging technologies without stranding investments. For example, the ideal solution should not rely exclusively on either elevated or meter-based infrastructure and should be able to adapt to the use of different communications modules as needed for the particular purpose at hand. Further, the solution should ideally allow various types of communication network infrastructures, such as mesh or point-to-point, to seamlessly co-exist so that appropriate technologies can be deployed based on the targeted needs of the utility. 
  • Open systems and standards – In order to realise the benefits of an AMI system, standards are a key component to allowing systems to inter-operate and provide capabilities across the utility. The AMI solution should aggressively implement standards in a way that is practical and well thought out, and the AMI provider should be a strong supporter of standards. Emerging standards, such as 802.15.4g, should also be taken into account, with a focus on covering real world use cases utilities will face such as the need for battery operated devices used in gas and water applications.

With the deployment of AMI systems, there are several stages that all AMI systems go through, as described below.

Communications network performance
One of the most critical considerations in any AMI system is the communications network performance. This is driven by many factors including robust communication algorithms, optimal path communication determination and bandwidth. Some systems today are realising acceptable daily read success rates above 99%, while other recently implemented technologies are continuing to undergo optimisation to reliably realise these rates. Other critical considerations are how the network will perform in light of on-demand control activities and during device firmware upgrades.

Daily reads of consumption, time-of-use and interval data
Once the communications system is operational, utilities focus on daily delivery of the metering data. Utilities typically expect fully deployed systems to exceed 99% daily read success of typical metering data, while performing on demand activities. Ideally, all metering data will be computed in the smart meter, not the AMI communications module, allowing accurate data that can be easily audited or performance verified by the utility.

Integration into the utility IT infrastructure
If not integrated earlier, then once the communications network is performing and providing metering information with a high daily success rate, utilities often look to integrate the system into the utility IT infrastructure. This involves close coordination between the utility IT departments, the billing department, operations, and the AMI provider. The greater the experience of the AMI provider in actual integration of the AMI head end system with other utility systems, the lower the risk of unexpected challenges in this phase.

Grid modernisation
Given a fully deployed and operational AMI system, utilities look for additional ways to leverage the AMI infrastructure. Many of the efforts in the industry have focused on distribution grid functions typically performed by the utility’s SCADA group. However, there are many opportunities to leverage AMI infrastructure to begin capturing real value today as technology integration between DA and AMI matures. The key for AMI solution providers is to partner with other technology providers to find ways to augment traditional SCADA functionality. Some examples of novel applications of AMI technology in commercial use today are described below.

Voltage conservation

A well known method to realise green benefits on the distribution system is voltage conservation. By voltage conservation, the utility uses the AMI system to monitor the voltage at key points on the feeder and uses this information to better regulate the voltage along the feeder. By pushing the voltage to the lower range of the allowed voltage limit at service delivery points, the utility can reduce loads along the distribution system as well as customer loading. Since distribution operation is a core competency of utilities, this provides an easy and effective means to implement a utility focused green programme with immediate benefits.

Commercial load shedding
As the utility system becomes stressed at peak loading times, utilities often look for a means to reduce large groups of load with minimal impact to the customers being served. An opportunity for large load shedding with minimal customer impact is AMI-based commercial load shedding of less sensitive commercial loads, such as irrigation pumps. In addition to shedding of loads, the AMI infrastructure enables supplemental customer benefits such as device status visibility and remote customer driven control opportunities.

AMI deployments

Phases of AMI deployments

Transformer load monitoring
One aspect often overlooked is how difficult it is for utilities to monitor the loading on secondary transformers and to know the voltage at the point of service along all points of the distribution feeder. As new loads are added, secondary transformers can become overloaded and be driven to failure. AMI offers a cost effective means to not only monitor the transformer loading, but also the voltage at the customer service point. Business benefits include: 

  • Transformer loading, voltage readings, reliability statistics 
  • Capital deferral of transformer replacements 
  • Significant CMO improvements by reporting outage on a per transformer level to the control room 
  • Reduction of momentary outages by analysing data to identify source 
  • Preventive investments leading to capital deferrals 
  • Data gap closing (transformer loading, transformer to customer relationships, phase loading, outage records).

Loss detection
Following a field study, a major utility in North America determined non-technical losses to be approximately 8% in the area studied. In other countries non-technical losses have been found to further exceed this percentage. Using AMI-based distribution transformer monitors along with data gathered from service delivery point meters allow ready detection of non-technical losses.

Other applications – AMI and DMS integration
In addition to AMI, the distribution management system (DMS) is an operations decision support system that greatly improves operator visibility and control of the electric distribution system for improved power efficiency, reliability and quality. Individually, the AMI and DMS systems provide major steps forward in helping the electric utility achieve its future vision. However, leveraging the facilities and capabilities of these two systems through integration is what will offer truly “world class” benefits in performance that go well beyond the benefits of the individual systems. AMI solution providers must thus work closely with DMS providers to provide additional capabilities to utilities to optimize the joint capabilities of these systems.

Technology continues to evolve and by its very nature this evolution will have profound impacts on AMI systems in fulfilling the needs of the smart grid. Some major trends in the industry include:

  • Continued expansion of new communications technologies – Continued expansion of WiMax, public wireless and improved dedicated SCADA WAN systems will continue to influence smart grid deployments. In the public wireless space, stadium pricing based on bytes transferred, not the number of endpoints, will offer new opportunities for AMI access points and stand alone smart meters. As the communication options evolve, AMI systems need to be able to seamlessly accommodate a myriad of choices. 
  • Continued separation of metering and AMI communications functions – Similar to Measurement Canada, utilities will want to make sure that meter functions such as interval and TOU data calculation are separate from AMI communications modules to insure accurate and auditable billing data. 
  • Standards will continue to improve interoperability – New standards will be completed allowing for greater interoperability and benefits from AMI systems.

As utilities evaluate AMI systems, they need to consider factors such as covering the industries’ basic requirements, system performance, ability to realise new applications and the ability of the system to adapt to new technologies. The implementation of a successful AMI system is a key step towards the accomplishment of the future “smart grid” vision. Leveraging AMI system capabilities to enable new smart grid functions provide benefits that go well beyond that provided by traditional “stand alone” distribution systems.