A smart grid uses advanced automation, control, information technology and operational technology systems for real-time monitoring and control of power flows from generation sources to consumers. Advanced metering infrastructure (AMI) or smart metering forms the core of smart grid architecture. It comprises smart meters, data concentrator units, a meter data management system, a head-end system, etc. It facilitates bidirectional communication between the meter and the systems at the utility control centre. Private discoms are taking significant steps towards its adoption. CESC Limited is implementing AMI based on radio frequency (RF) mesh technology in Kota, its franchise area under Jaipur Vidyut Vitran Nigam Limited. This is India’s first AMI roll-out and involves the deployment of 65,000 smart meters in Kota and 15,000 smart meters in Kolkata, West Bengal.
AMI components and benefits
There are three components of AMI – smart meters, communication network, and head-end system and analytics. The communication network is one of the crucial elements. The network should be universal and equipped with multiple applications. While several communication technologies have emerged over the years, the common technologies are power line communications (PLC), RF mesh, cellular and Wi-Fi. Every utility should choose its technology taking into account the type of meters deployed and the area of deployment, among other parameters. Interoperability is the ability of smart meters to communicate with the head-end system at a device level or server level. This can be achieved through the incorporation of a network interface card.
Meter data acquisition systems help in collecting the data remotely. Remote data collection enables error-free and transparent billing. It also reduces provisional bills. In Kota, CESC has reduced its provisional bill from 10 per cent to less than 1 per cent. AMI helps in early detection of meter defects, and provides other benefits such as improvement in power quality, proactive outage management, objective resolution of consumer grievances and electronic consumer indexation.
CESC’s metering scenario
The company has around 3.3 million low tension (LT) consumers with direct connected meters. Of these, 3 million meters are single phase and the remaining are polyphase. Currently, meters are read manually by meter readers. CESC has around 1,700 high tension (HT) meters, 8,500 LT transformer-operated meters, 8,300 distribution transformer meters and 14,000 street light metering points. All these meters are part of the AMI and AMR roll-out. AMR has significantly transformed the utility’s business operations. Apart from remote billing and energy auditing, identification of metering defects, overloading and underloading of transformers, identification of unbalanced loading, SMS-based outage management, etc. have become possible. But this is restricted to the high-end consumer segment. In order to achieve operational efficiency and remote manageability in a big way, AMI is required.
Before selecting a final technology, the company conducted two proofs-of-concept (PoCs) on RF mesh (865-867 MHz) for 65-67 MW along with one PoC on RF mesh (2.4 GHz). For proper comparison between the two projects, the PoCs were conducted in the same area.
Based on the PoCs, the company is deploying an RF mesh (865-867 MHz) pilot project in Kolkata. Different types of meters have been deployed under the project. The project has adopted the capex model with a multi-application communication canopy. Optic fibre cable (OFC) has been used as the primary backhaul and cellular as the secondary one. It is developed on the software- as-a-service model with the head-end system and analytics. So far, meters have been installed for 13,000 single-phase consumers and 1,500 three-phase consumers. Further, 14 distribution transformers have been deployed along with two automated ring main units. Typically, two communication devices can cater to about 10,000 smart meters. In this project, four communication devices will be used, which will ultimately cater to 20,000 smart meters. with the project has a success rate of 99.5 per cent.
Deployment models and components
Based on all the pilot studies and PoCs, RF mesh in 865-867 MHz has been selected as the appropriate technology for AMI roll-out. Under RF mesh, two models can be deployed. The first one involves the sharing of geo-coordinates of the boundary area and the assets within the area with the communication solution provider followed by the deployment of smart meters as per the utility’s requirement. The other type of model involves the deployment of the smart meters first followed by network devices. The second model is less flexible as shifting of network devices may be required in the future for better network optimisation and coverage. In terms of backhaul, OFC is more reliable than cellular technology. Although OFC involves a higher cost, it is preferred for primary backhaul.
There is also a need to address other critical components before AMI’ roll-out. These are mapping of meter parameters, and integration with utility applications including end-to-end testing, and data storage and backup. For mapping meter parameters, different types of smart meters send data to the head-end system. This is a one-time activity, and can be carried out during end-to-end testing. Further, the head-end system has to be integrated with the existing utility application for smooth data flow. Data storage or backup is a key component of AMI. The analytics will be effective only if data storage is managed and governed well.
Challenges and the way forward
The evolving metering systems face several challenges and constraints. In India, meter reading is mostly outsourced and is a labour-intensive job. The people who will be affected by smart meters oppose their deployment. The perceived health hazards associated with smart meters have also created negative sentiments among consumers. Space constraint is another issue faced by utilities, particularly in congested areas. Since smart meters have larger dimensions than conventional meters, their installation is difficult within the existing meter board. These boards require modification, resulting in additional cost. Further, the technology is facing teething troubles owing to the complexity of smart meters. The existing processes need to be modified to align them with AMI.
In India, there are very few reputed manufacturers ready with a PLC solution. PLC is suitable for cluster deployment and highly dependent on the quality of LT networks. This type of communication is further affected when the consumer uses a water pump and there is noise interference. Also, cellular technology, which is suitable for supervisory control and data acquisition deployment, depends on mobile signal strength. It is difficult to operate this type of technology without any service-level agreements with the network service provider. Wi-Fi, meanwhile, is prone to security concerns. The communication between smart meters and data call centres can be intercepted. Although RF mesh provides larger bandwidth, it faces line-of-sight limitations.
To overcome these challenges, strong government policy support, innovative financing models and efficient communication technologies will play a crucial role. Overall, the benefits of smart metering exceed the cost of AMI implementation. That said, utilities will have to efficiently manage and maintain their systems and processes.
Based on a presentation by Santosh Chattopadhyay, Manager (Metering), CESC Limited, at a recent Power Line conference