Better Monitoring

Implementing PMUs and WAMS to enhance grid visibility and management

The complexities in grid operations have increased with the increasing share of renewable energy, growing number of distributed energy resources (mostly connected at the distribution level), and higher growth in power demand as compared to transmission network capacity. This calls for the use of new monitoring methods and technologies. As per the Smart Grid Vision and Roadmap for India document prepared by the Ministry of Power in 2013, wide area management systems (WAMS) and phasor measurement units (PMUs) should be implemented across the transmission system.

A WAMS pilot project was undertaken at the northern grid from April 2010 to May 2011, wherein PMUs were installed across eight substations. Subsequently, similar projects were initiated in other regions with the installation of 64 PMUs. Following the success of the pilot projects, in 2012, Power Grid Corporation of India Limited (Powergrid) rolled out the Unified Real Time Dynamic State Measurement (URTDSM) project to improve system operations through the implementation of WAMS. To provide dynamic visibility of the grid, WAMS are being installed across the country under the URTDSM project. Under the URTDSM scheme, Powergrid is installing PMUs at all substations at the 400 kV and above voltage levels and all generating stations at the 220 kV and above levels. The project also entails the installation of PMUs at high-voltage direct-current terminals, as well as at important international and interregional connection points. Subsequently, the utility will undertake analytics development for the better utilisation of data. The PMUs will provide real-time measurements and reduce the dependence on estimates for managing the energy flow in the grid. This will increase the capacity of congested corridors, improve transmission asset utilisation and lower energy costs for consumers. The total cost of setting up WAMS under the project is estimated at Rs 2.39 billion. Of this, about Rs 1.7 billion is for Phase I while the remaining is for Phase II. Two packages have been awarded for the implementation of the project – Package-I for the northern, eastern and north-eastern regions and Package-II for the western and southern regions. These packages have been awarded to Alstom SAS (France), Alstom Grid (UK) and GE T&D India Limited (earlier known as Alstom T&D India). The project is currently under way.

As per the information available from the southern regional power committee, the total number of PMUs to be installed in the southern region under Package–II of the URTDSM project has increased from 240 to 270 due to the commissioning of new stations and feeders. In Southern Region-I, a total of 107 PMUs have been supplied, of which 97 have been commissioned and 85 have been integrated. In Southern Region-II, 109 PMUs have been installed across 32 substations while 103 PMUs across 31 substations have been integrated. A total of 286 PMUs have been envisaged to be set up at 78 substations in the eastern region. Of these, 211 PMUs at 52 substations have been installed and 114 PMUs at 24 substations have been integrated.

Meanwhile, there are only eight PMUs in the north-eastern region at Bongaigaon, Balipara, Sarusajai, Misa, Badarpur, Agartala, North Eastern Hill University (NEHU), Shillong, and Imphal, installed as part of a pilot project. Under the URTDSM scheme, around 90 PMUs are expected to be installed at various locations across the region.

Challenges and the way forward

One of the challenges faced during the implementation of the project has been the reluctance of power producers to install PMUs at their sites. Further, the number of PMUs planned to be installed has been under continuous revision, with new substations coming on-line. This has led to a lot of rework in the contract with Alstom, thus delaying the execution of the project. Powergrid had submitted a petition to the Central Electricity Regulatory Commission (CERC) to obtain regulatory approval for the implementation of Phase-II of URTDSM. The commission denied the approval for Phase-II in September 2016 in view of the delay in the execution of Phase-I of the project. It directed Powergrid to expedite the works under Phase I and seek approval for Phase-II only after substantial progress has been made under Phase I.

The implementation of the project has been very slow and there is a need to step up efforts to complete the lagging Phase-I of the project and avoid much delay in the initiation of Phase-II. Due to the delay in the commissioning of PMUs under URTDSM, monitoring and analysis of grid events cannot be done. Hence, it is necessary to expedite the commissioning of PMUs under the URTDSM scheme. Once commissioned, the project is expected to improve grid management.

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