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Much of the discussion around smart cities centers around smart buildings and the proliferation of smart meters (i.e., advanced metering infrastructure). Also discussed is the growing importance of distributed energy resources (DER) and the multitude of smart devices that make up the Internet of Things (IoT). However, the criticality of the electric transmission and distribution (T&D) grid that powers the smart city or smart community is rarely or only casually mentioned. Regardless, many T&D technologies and features will likely be critical to the smart city of the future.

Generation: The shift from local coal or nuclear generators supplying urban population centers to remote utility-scale wind and solar generation resources is rapidly occurring and can be seen across North America and Europe. Large-scale wind and solar generation farms are becoming an increasing portion of the generation mix. Electric power must be transferred from these remote sites to urban populations over hundreds (if not thousands) of miles of new high-voltage transmission lines using high-voltage direct current (HVDC) and extra high-voltage alternating current (HVAC) transformers and converter stations.

Transmission grid technologies: In turn, these lines require new approaches to monitoring and control necessary to maintain voltage levels and synchronize the three-phase power delivery at each substation along the way. Relatively new phasor measurement units (PMUs) and digital protective relays collect voltage, current, and power factor information up to 60 times per second, time stamping it for comparison purposes. Synchrophasor analytics make real-time comparisons of status at each end of the transmission lines, warn operators, and automatically correct voltage or power factor when readings diverge from optimal operating conditions. These high-speed incidents go largely unnoticed with traditional SCADA monitoring and control and can sometimes create major reliability incidents.

Distribution substations: The digital substation will also be a critical part of the new smart city. As every device in the substation is upgraded to have digital communications and control, substations will be ringed with high-speed fiber optic networks. These networks connect the various devices, including transformers, switchgear, protective relays, and other intelligent electronic devices. This sets the stage for the virtual substation, where every piece of equipment is modeled, operating data is shared, and system operations are monitored, controlled, and automated at the local and centralized operations centers.

Distribution feeders and low-voltage (LV) distribution transformers: Distribution feeders connect the substation with customers in both urban and rural locations. Urban distribution feeder systems are complex meshed networks, with fleets of disconnect switches, reclosers, and other devices that allow the network to be reconfigured and continually operated when isolated system faults occur. These intelligent electronic devices increasingly include local and autonomous decision-making and control capabilities. They communicate with adjacent devices and reconfigure the network or managing voltage and power factor without control by the substation or central operations center.

There are also millions of LV distribution transformers that operate at the edge of the grid, stepping down voltage for delivery to the customer. These transformers have traditionally been mechanical/electrical devices with no monitoring capabilities, but are now being gradually replaced with smart transformers that measure and report critical operating condition information. Sophisticated transformers may provide control and automation capabilities, which are becoming increasingly critical for managing the distribution grid as DER penetration increases. Retrofit monitoring and control devices are also now available and can be installed close to problematic or overloaded transformers.

Navigant Research recently released my global market study and forecast for substation and distribution automation and maintains an extensive library of subscription reports on smart cities, microgrids, and transmission and distribution technologies.  They can be found at www.navigantresearch.com.

Smart Cities and the Smart T&D Electric Grid is my final blog published by Navigant Research. Mt future blogs published on IntelligentNRG will focus on emerging smart grid technologies and IT systems, as well as drones, UAVs, robotics, physical security, and IoT.

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Both physical and cyber security threats to the electric utility transmission and distribution (T&D) grid in all regions of the world are real. Part 1 of this blog series discussed the physical security problem and some of the measures North American utilities are taking to respond to the North American Electric Reliability Corporation (NERC) CIP-14 requirements. Regardless of whether replacement high-voltage transformers, switchgear, and breakers need to be ordered from major vendors such as ABB, General Electric (GE), Siemens, or other regional companies, replacement equipment is not warehoused. Instead, it must be special ordered, manufactured, and shipped to the transmission substation where the replacement will be made.

Manufacturing lead times are typically 12 to 18 months, which is an issue the North American transmission system operators are dealing with by participating in Grid Assurance, banding together to create stockpiles of critical equipment in multiple locations across the nation. And while Grid Assurance will own and provide timely access to an inventory of emergency spare transmission equipment, the regional or national shipping and transportation issues are daunting.

Issues of Size

The sheer size of 250 kV to 750 kV high-voltage transformers makes physical transportation a logistical nightmare, regardless of whether large-scale trucks or railroad transportation is used. Companies such as ABB and Siemens have highly specialized trucks and flatbed rail cars dedicated to high-voltage transformer transportation. A huge flatbed truck designed to transport from 100 tons to 500 tons of high-voltage transformers can be seen below. These trucks need to be routed over roads that are certified for heavy loads and often have circuitous routes because of height and width clearance issues.

Transformer Shipping Using Lowboy Flatbed Truck

big truck jpeg

(Source: ABB)

However, the largest 500 kV and 750 kV extra high-voltage transformers may require specialized rail transport with similar clearance issues, bridge weight restrictions, and even access close to the transmission substation. Shipping and transportation from regional sites, vendor manufacturing centers, or overseas shipping yards may take weeks or even months, again lengthening the restoration timeframe. Moving huge transformers by rail has a similar set of constraints, based on the vicinity of rail lines to the transmission substation location.

Unfortunately, extra high-voltage and high-voltage transformers are huge pieces of equipment, and replacement and restoration time following a physical attack or transformer failure is not an overnight event. It could take months for parts to be manufactured, delivered and installed. It is clear that restoration initiatives are intimidating. Examples will be provided in Part 3 of the Physical Security blog series.

This blog was also published at http://www.navigantresearch.com/author/jmccray on February 11, 2016.

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