New areas, such as demand-side management, will require both customer and distributor control along with visibility.  As a result, power companies will need to focus more attention on their communication networks: networks that will be characterized by higher bandwidth capacity and the deployment of Ethernet and other high-performance technologies.

The traditional approach to electric power can no longer handle the changes that have taken place over the past 10 years. This is due to several factors:

•    Huge increases in bulk power shipments from one region to another
•    A shift toward distributed generation, which scatters many smaller power plants closer to customers
•    A shift toward renewable sources of energy, such as wind and solar
•    An increasing need to regulate and control the demand side; and
•    Far more stringent regulations for reliability, security, and reporting
 

The changes associated with this new approach to electric power generation and distribution add considerable automation and communications load to the existing network. Most of these changes are taking place in the delivery infrastructure, where the new smart grid concept employs digital technology in three important ways:

•    Intelligent devices monitor and measure what is going on.
•    Two-way communications allows those devices to talk to each other; and
•    Advanced control systems enable computers to automatically make low-level decisions, leaving human operators to oversee and control large areas from a central station.

Changes in Generation and Distribution
Recent changes in policy mean that electricity companies are under pressure to increase the amount of electricity derived from renewable sources. This has resulted in the emergence of wind turbines, photo-voltaic cells, and tidal turbines, all of which generate power at far lower voltages and connect to the grid at lower distribution levels (not at the transmission level). For example, the Danish electrical grid, at the beginning of the 1990s, had eight generation centers. By 2006, the number grew to more than 4,000, largely through the introduction of wind farms.

The implications of these few requirements are that every distributed generator and every plant item, no matter how small, may need to be monitored and controlled remotely. For example, a village of the future may be its own micro-grid supplying its own electricity locally, and only drawing energy from the main grid in times of faults or failure of wind, sun or sea waves. Therefore, these grids will need accompanying communications technology for this monitoring.

Substation Automation: The IEC 61850 Framework
The IEC 61850 standard offers a broad framework for substation automation based on huge advances in networking technology. Technologies such as carrier Ethernet switching, high-speed wide area networks and high-performance low-cost computers are providing capabilities that could scarcely be imagined when most legacy substation automation protocols were designed.

The IEC 61850 framework provides the foundation for a communications network for the next generation substation that offers higher integration, greater flexibility, and plug-and-play functionality replacing hard-wired connections. In particular, the 61850 series standardizes the mechanisms used to access and exchange data within the substation. It standardizes SCADA data and services, and encourages peer-to-peer exchange between intelligent electronic devices (IEDs).

IEC 61850 defines an interoperable communications system for the exchange of information between devices within a substation, and the structure chosen to implement this follows the ISO layer communications model. Specifically, the primary protocols chosen for the various layers include Ethernet and IP.

Since Ethernet plays a critical role in the protection and control tasks in the utility, the communications architecture, including the switches, must be designed to meet the most stringent requirements of availability and low packet latency: A packet delay of 4 milliseconds is required for peer-to-peer communication. An interesting outcome of these issues is that an optical fiber network becomes a necessity. High-speed interfaces are needed to meet the 4 msec delay requirements and all standardized interfaces above the fast Ethernet (either electrical or optical) are exclusively optical.

Dealing with Aging Infrastructure
The planning lifecycle of an electrical plant is often 40 years or more, and delaying the upgrade of an expensive plant can be massively beneficial to the distribution company’s business model. An application capable of measuring plant degradation through monitoring assets for unusual activity may be able to predict failures and hence influence replacement cycles.

Similarly, temperature monitoring of circuits enables distributors to use circuits up to the maximum practical load rather than at lower theoretical thresholds, thereby allowing greater efficiency and capacity enhancements to be delayed or even avoided. 

Transition toward the smart grid will be achieved gradually. It will therefore be necessary to concurrently support both legacy interfaces, such as V11, V24, and V35, along with Ethernet and other optical interfaces to maintain the current mode of operation while enabling the smooth introduction of new ones. A key feature in this context is the support of Ethernet over existing PDH and SDH radio links. This application requires a high-speed, real-time communications network that extends deep into the distribution network.

Utility Telecommunications Network Infrastructure
The communications network within the distribution company environment needs to undergo transformation. The control and communications networks must extend to all customer points if real-time demand side management is to be used effectively. Similarly, if customers are to be encouraged to become generators, an additional data stream must be aggregated to the network extending to the home. And if both distribution company and customer control are to be supported, data requirements increase even more.

At its edge, the network does not need to have very high capacity. But it must have high service penetration. One can envision a mix of technologies at the edge, with an aggregation into a core network that is built on optical fiber.

An Integrated Communications Infrastructure is a fundamental requirement for the other key technologies in the functioning of the smart grid. Most utilities have implemented very large, privately owned and operated telecommunication transport networks, supporting both fixed and mobile voice and data communications for its operational (i.e., support for grid monitoring, SCADA, remote management of substations, etc.) as well as corporate (internal telecommunications, IT, and business applications) functions. Although these two major areas typically make use of the same facilities, their needs are quite different in terms of bandwidth, traffic, availability, performance, and security and communications protocols.

In addition, these networks are supported by a variety of technologies, including microwave radio with high capacity links, trunked radio systems, mobile data radio systems, PDH, SONET/SDH, and PCM (n x 64 Kbps), which include an immense variety of interfaces such as V11, V24, and V35 for SCADA applications, IEEE C34.37 for teleprotection, FE for video surveillance, as well as PDH and SDH interfaces facing fiber and radio links. Distribution companies require fiber at aggregation points to collect information from large groups of houses, and at data centers to manage the interchange of information for real-time decision-making and control. Aggregation points may be local substations, where fiber, for example, may also be a good choice as a passive temperature and monitoring sensor for electricity cables.

IP Becomes a Unifying Technology
The Integrated Communications Infrastructure must address not only the backbone, but also the spur segments. While core utility operational networks can be based on a number of technologies, the most prevalent is Next Generation SONET/SDH also known as MultiService Provisioning Platforms (MSPPs). Packet-switched networks (PSNs) are also gaining attention in the utility telecom market. Next-generation (NG)-SDH is attractive, as it can support IP and Ethernet applications and legacy services simultaneously. In addition, NG-SDH augments the functionality of the existing SDH network and enables its evolution to IP/MPLS by providing very effective Ethernet transport over SDH. Both pure PSN and Ethernet over SDH are considered Carrier Ethernet networks.

Carrier Ethernet is a connection-oriented protocol that provides “carrier grade” performance for mission-critical applications, including high reliability, QoS, provisioning, and security. The challenge is to combine these features with the cost-effectiveness and simplicity of Ethernet.

There are two main alternatives for providing Carrier Ethernet services:

1.    Ethernet over SDH (implemented by the MSPPs)
2.    Packet-switched Networks (Carrier Ethernet Switch Routers)
 

Figure 2 illustrates the technology alternatives for implementing a Carrier Ethernet transport network.

Both solutions offer a number of advantages and disadvantages. MSPP is a proven and mature carrier-class infrastructure offering robust reliability, protection, and operations, administration and maintenance (OAM), while Carrier Ethernet routers offer higher-capacity Ethernet services. The optimal utility telecommunications network is the one that enables a combination of both.

The key technology is an MPLS-based Ethernet network that uses MPLS as a circuit-oriented layer spanning the entire carrier Ethernet and SONET/SDH network.

The Need for Optical Communications
In addition to the IEC 61850 framework, below are two examples where an optical communications network is required as a consequence of the traffic engineering of the network – smart metering and reducing the vulnerability to intra-substation electromagnetic and radio frequency interference inherent in copper cables, as in the case of the optical IEEC C34.97 interface. 

Utility Telecom Network Sizing for Smart Metering
Assume that a data rate per monitoring point of only10 Kbps is required for all applications, billing, demand side management, safety and supply continuity, and generation and distribution management.

If we consider that a distribution company serves some 2.5 million households, and if we make a further assumption that about 5% of all households will install some form of generation and that commercial generation, for example, wind farms and other ventures, gain 15% and 25% of generation at distribution points respectively, we can calculate total demand.

Because of the large number of users, it is clear that fiber is required at aggregation points. In fact, assuming that fiber
and WiMAX services are currently the only  reasonable option above 30 Mbps, fiber or WiMAX are needed to backhaul from every group of 3,000 houses. Since small towns of 3,000 houses often do not have broadband or effective wireless broadband data services, distribution companies may have to put their own infrastructure in place. In more heavily popula­ted towns, it is clear that fiber is the best solution – from the aggregation point all the way back to the control center.

Distribution companies require a far greater degree of visibility and control deep within the distribution network as data collection and real-time analysis become a more fundamental part of the business model. Fiber networks play an essential role in supporting the information exchange requirements between customers, the distribution network, and the data centers carrying out the real-time analysis of the data. The aggregated volume of data is unlikely to be supported without a fiber infrastructure in some parts of the distribution network.

Low Speed Optical Communications – Eliminating Electromagnetic Interference on Data Networks
Historically, copper interfaces between the teleprotection equipment and multiplexers transfer critical information to the command center. These high-speed low-energy signal interfaces are vulnerable to intra-substation electromagnetic and radiofrequency interference (EMI and RFI), signal ground loops, and ground potential rise (GPR) – all of which considerably reduce the reliability of communications during electrical faults.

Optical fibers do not have ground paths and are immune to noise interference; making optical data links a superior interface for intra-substation communications. Replacing copper interfaces with optical fiber ensures isolation from dangerous GPR, prevents induced electrical noise, and eliminates the signal ground loops and data errors common to electrical connections.

The IEEE C37.94 standard defines an N x 64 Kbps multimode optical fiber interface between teleprotection and digital multiplexer equipment. Teleprotection equipment is used for quickly isolating faults in power transmission systems and is crucial for preventing damage to the network in the event of power outages (blackouts). Teleprotection is aggressively being deployed on communication links residing in harsh high-voltage substation environments. The optical data link replacing existing electrical interfaces in these systems provides immunity to intra-station electromagnetic interference (EMI) and reduces data errors.

Conclusion
The challenges of rising global energy demands, climate change, increasing import dependence, aging infrastructure, and higher energy prices are driving the need to deliver sustainable, secure, and competitive energy. As utilities move toward smart grids, it becomes critically important that they look toward a communications architecture that can be shared among multiple applications that can be supported by the speed, reliability, and security of the infrastructure.

Although communications is not the fundamental activity of electric utilities, a smart grid requires a communications system with the capacity to support traditional utility functions and the flexibility to adapt to new requirements, such as advanced metering, demand response, distributed generation, and more.

Since they provide highly reliable IP/Ethernet networks, the deployment of MSPPs and Carrier Ethernet switch routers to build IP utility telecommunication networks is constantly increasing. Through careful planning, designing, engineering, and application of these technologies, utilities can achieve the business objectives of a smart grid while preserving current infrastructure investments.