Building Smart Grid Core Networks
- Written by Arvind Durai and Vikram Varakantam
The ability of a utility to create ubiquitous connectivity between all of its current data sources and decision-making systems is essential for the success of smart grid deployments. Yet the characteristics and performance requirements for wide-area networks are quite complex due to the multitude of grid applications and enterprise applications that are essential to utility operation.
Among the many challenges utilities currently face in operating the electric grid, the most prominent are:
- the limited number of digital sensors that can collect raw data from the grid
- a limited number of communications to existing digital sensors to permit collection of data
- limited analytic capabilities for assessing grid condition data so that actionable information can be inferred
- limited integration of information from various places in the grid to provide an integrated awareness
The vision of a smarter grid can be defined in terms of those challenges. A smarter grid will be connected with sensors at various locations communicating the generated data. The smarter grid will be intelligent, such that predictive analytics turn data into actionable information and connections are used to control sensors. The grid will be integrated so that information from one place in the network can be shared with another; intelligence in one place can be controlled or used by another resource located in the network.
The ability of a utility to create ubiquitous connectivity between all of its current data sources and decision-making systems is essential for the success of smart grid deployments. An intelligent communication infrastructure that can efficiently transport various types of data with varying degrees of security and reliability is a core requirement.
The Wide Area Network (WAN), or core network, connects various smart grid networks and forms a vital connected, intelligent and integrated smart grid. Naturally it has to support the applications and the corresponding requirements in each of the various networks it interconnects.
The characteristics and performance requirements for WANs are quite complex due to the multitude of grid applications and enterprise applications that are essential to the operation of a utility. Grid-oriented applications include synchrophasors, supervisory control and data acquisition (SCADA). Among the utility enterprise applications are video conferencing, IP telephony, storage and physical access security.
As critical services such as voice, video and SCADA data converge on IP, the resiliency, scalability and availability of the core infrastructures become very important. Architectural options for different WAN designs, as detailed in our IEEE paper on the subject, involve a number of considerations.
The proposed models for smart grid WAN connectivity are: multi-service IP core; multi-service core with multiprotocol label switching (MPLS); MPLS networks with a regionalized model; and WAN core nodes options for the aforementioned three models. The options include single core, dual core and multi-planar.
With the exception of the first option, all the other options use MPLS as a key technology for deploying converged WAN networks. Some key characteristics of MPLS architectures are that new features can be added to modify the design for better resiliency, and that new application requirements can be easily supported.
One such feature is known as Routed Pseudowire. Routed Pseudowire is a combination of Layer 3 Virtual Routing and Forwarding (VRF) instances and its extension through Layer 2 pseudowire across a MPLS cloud to the a branch or substation site.
In most MPLS networks, while building Layer 3 VPN configurations, all of the nodes in the network should be configured to participate in both the data and control planes. A typical Layer 3 VPN build-out needs a number of relatively arcane network features–BGP, VRF, MPLS, IGP–to be configured and operational, and troubleshooting these complex configurations across all the nodes in a utility network requires trained eyes.
With the Routed Pseudowire feature, only the hub sites need to have a complete configuration of the Layer 3 VPN based features compared to the edge sites; they only need MPLS, routing and Layer 2 VPN configurations, which facilitates the addition of the remote sites. As this option simplifies the configuration of the nodes at the edge sites, it eases the operational complexity and the skill levels required to operate and troubleshoot these complex networks and yet provides the advantages and flexibility of all the MPLS based architectural options.
MPLS network architectures allows adoption of newer technologies such as MPLS-Transport profile (MPLS-TP) based networking. MPLS-TP is an IETF standards-based specification that simplifies the packet forwarding paths. As MPLS-TP technology matures, it will provide more diversity in terminating the circuit switch links (Digital Subscriber Line Access Multiplexers or DSLAMs, gateways, T1/E1 aggregators, broadband remote access servers or BRAS, and so on) in a core MPLS cloud of packet transport networking technology, thus integrating legacy and new transport assets.
The concept of routed pseudowire can be applied in this environment to extend Layer 2 pseudowire to edge sites; their access links will be a combination of packet and circuit switched links. These access links can be aggregated in a MPLS/IP core with a Layer 3 VPN head end.