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WAMS: A new and emerging technology for efficient electricity grid performance

Last updated 18 January 2017

The current installed capacity of grid interactive Renewable Energy power plants in India is 46.6 GW ( as on Nov 2016); with still more ambitious projects to materialize in the coming decades. Renewable energy generation is intermittent in nature and with its integration to the grid in a large quantum would increase the complexity regarding monitoring and control of a large grid such as the Indian power grid.

Modern interconnected power transmission network require a close monitoring and control of equipment and grid operation. Even small disturbances, if not detected at an early stage, may lead to widespread and cascading failure of the electrical grid. Accurate and reliable real time sensors are required to make the electric grid a smart one. Smart electricity grid means a more resilient, reliable and capable grid, needed to manage the variable Renewable Energy sources and other intelligent equipments and systems. Currently Supervisory Control and Data Acquisition (SCADA) is widely used by utilities to monitor and control the grid operations. The SCADA measurements are made once every 4 to 10 seconds or so, and is no longer a fast measurement to provide adequate observations.

Because of the widely spread grid and with the advent of open access and electricity market, wide area monitoring and control is the need of the hour. In this scenario, new and emerging technology such as Wide Area Measurement System (WAMS) is needed to enhance the efficiency and performance of the grid. 
"Wide Area Measurement Systems (WAMS) consists of advanced measurement techniques, information and communication tools and operational features that facilitate the monitoring, and control of a more complex interconnected power system, particularly with large penetration of Renewable Energy"
Presently WAMS is used as a complementary system to enhance the real time 'situational awareness' much needed for the safe, efficient and reliable operation of the grid. It requires installation of Phase Measurement Units (PMU) at strategic locations throughout the grid such as power plants and major substations. This technique incorporating synchro-phasor measurements (Phasor measurements that happen at the same time is known as synchro-phasor measurements) facilitates dynamic real time measurements and visualization of the power system which is much needed for the safety and security of the grid.

PMU measurements are taken at nearly 25 to 50 samples per second or even 200 samples per second which is quite high compared to the conventional measurements. Thus, PMU essentially requires a very robust and highly scalable data communication network to facilitate a more clear view and control of the power system. The information from the PMUs is passed on to a Phasor Data Concentrator (PDC) installed at central locations; and further forwarded to the SCADA system. For the fast data transfer high bandwidth communication networks are needed.

Global application of WAMS:

Many utilities in America, Europe, Brazil, China etc. have started developing and using this emerging technology in operating their large electrical grids. China has been using the WAMS technique since 2006 and has installed several hundred PMUs at its key locations.

WAMS technique in Indian Grid:

In India also, the process of installation of PMUs has already began and 8 PMUs already installed and commissioned in the Northern Region (NR). The data to the PDC, located at the Northern Region Load Dispatch Centre (NRLDC), is transferred through fibre optic communication link. From the Phasor data, more accurate information about the load angle at different location of the grid, with updation in few ms, is available. This enhances the capacity of the tools available for grid operation. About 1000 to 1500 PMUs and 30 to 60 PDCs are proposed for installation in the 12th FYP. The State Load Dispatch Centre (SLDC) may have the Master PDCs and the National and Regional Load Dispatch Centres (RLDC) may get the Super PDCs.

Ref:
1.       “Draft National Electricity Plan”, Vol-II, Transmission, Government of India, Ministry of Power, CEA, 2012.  

2.       Progress update by Ministry of New and Renewable Energy (MNRE), Government of India