Application Layer Smart Grid Smart Grid Enterprise Smart Grid Enterprise Applications Enterprise Applications Applications Enterprise Bus ICT Layer Information Technology Infrastructure Security Regime Power System Layer Communication Infrastructure Utility Assets Generation Transmission Distribution figure 5. A hierarchical smart grid system integration map. the top of the chain through adopting and integrating new enterprise bus functions. that approach is understandable and very much in line with the current constraints on utility assets and organizational structures. in fact, the early attempts to modernize the system had to take into account the realities of a highly compartmentalized system and operational hierarchy tasked with delivering a critical service to customers while meeting the challenges with which most utilities grapple. Figure 5 depicts the approach utilities in general have taken in their integration of smart grid functions. the point of entry of new functions into the hierarchical structure of the utility system has been at the interface with customers (e.g., smart meters), together with the associated support functions within the enterprise bus, such as meter data management (mdm) systems. Patches of plumbing to connect the two ends of the function (e,g., the required communication system to support the capture and exchange of data for the purpose of billing and revenue management) are thus inserted within the appropriate information and communication technologies (iCt) layer of the system. the question utilities have not answered here concerns what other smart grid capability the chosen ami technology can support. the current integration of ami systems across many b#3 Public Switch Network b# 4 D-Sub#1 T-S u D-Sub#2 D-Sub#4 M1 HAN#1 M2 HAN#2 M3 HAN#3 Utility Field Network T-Sub#2 Power Plant#1 T-S u T-Sub#1 b# 3 SG-A pp#5 SG-App#3 SG-A pp#4 Utility Core Network Feeder D-Su SG-App#1 SG-App#2 Power Plant#2 Wide Area Network (WAN) Local Area Network (LAN) Home Area Network (HAN) figure 6. Disjointed network domains in a legacy grid. 60 ieee power & energy magazine may/june 2014