The main objectives of adopting information and communication technologies (ICT) for any discom are business continuity; efficiency in business processes, operations, metering, billing and collection; capacity building; aggregate technical and commercial loss reduction; proper energy accounting; and consumer satisfaction. Further, IT ensures world-class practices and controls at the operational level and an overall improvement in the quality and flow of information for decision support systems for a discom. IT is used in the power distribution segment as an enabler for commercial decision-making, planning, business process management, asset optimisation and resource allocation.
Choice of connectivity
Depending on the available media, bandwidth requirements and usage, various connectivity solutions are available for utility applications. The key technologies available for backhaul transport communication networks are synchronous digital hierarchy, multiprotocol label switching (MPLS), MPLS-Transport Profile and carrier Ethernet. For access communication networks, the available technologies are high tension power line communication (PLC), radio frequency (RF) mesh, GPRS/GSM, CDMA and virtual private networks (VPNs). For last mile connectivity, the technologies available are ZigBee and low tension PLC.
Tata Power Delhi Distribution Limited’s (TPDDL) 350 km fibre network consists of a mix of leased fibre from service providers, an optic fibre cable (OFC) network as well as an optical ground wire system. Further, over 180 locations (including grid substations, district offices and zonal cash collection centres) are connected through optic fibre, RF, GSM and GPRS technologies.
The company’s communication network has a core ring with a capacity of STM 16 or 2.4 GHz. Both its data centres are on the core ring network. The subrings have a capacity of STM 4 and data from these merges with the core ring. The communication network consumes around 400 Mbps of bandwidth for various applications. RF connectivity technologies are also being used in the communication network. In the case of a fibre cut, data is transmitted through 100 Mbps microwave links between adjacent subrings.
Design and performance requirements
While designing communication networks, the key factors that need to be considered are budget constraints and time frames; the applications and services required to run on the network; bandwidth estimate of each application and service per user; the number of users and locations to be connected on the network; and centralised and decentralised server architectures as well as main and backup centres.
The backbone media selection can be wired, wireless, OFC, copper, buried, overhead, owned or leased. The last mile media selection can be wired, wireless, owned or a VPN option or have the right-of-way availability option.
The strength of a communication network can be assessed based on several parameters. One of the important performance requirements for any communication technology is network availability. The amount of time the network is available for use (along with other performance parameters) should be stated in the service-level agreements signed with telecom service providers. Another performance requirement is network latency, which can be measured in terms of the response requirement (when data is needed) and the data rate requirement (how much data can be made available in a given amount of time). Response requirements (measured in seconds) are distinct from data rate requirements (measured in kbps or Mbps), and must be met independently.
Further, another performance requirement for a communication network is that it should be able to support the quality of service provisioning mechanisms, that is, control mechanisms that can provide different service qualities or priorities to various users or data flows. This involves agreement on “traffic contracts” with the application software and reserve capacity in network nodes. However, in the case of more-than-adequate bandwidth availability, this is not an essential requirement.
Capacity planning is also an essential performance requirement of communication technologies. This refers to the amount of traffic that can be managed on a communication network. Traffic capacity planning needs to be based on the operational support traffic, substation traffic load on the backbone transport network, distribution automation load on the access network, advanced metering infrastructure (AMI) traffic load on the access network as well as the overall combined traffic effects on the total network.
Based on a presentation by Sanjeev Kumar Rana, Senior Manager, Smart Grid Group, TPDDL, at a recent Power Line conference