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PMU TECHNOLOGY

A phasor is a complex number that represents both the magnitude and phaseangle of the sine waves found in AC system as shown in figure 1.1.

Fig.1.1: Phasor representing magnitude & phase angle of sine wave of voltage or current.

Phasor measurements that occur at the same time are called synchrophasorsand can be measured precisely by the Phasor measurement units !P"#s$. P"#measurements are ta%en at high speed typically ' or '( samples per second )compared to one every * to 1( seconds using conventional technology. +achmeasurement is time,stamped according to a common time reference. -imestamping allows phasors at different locations to be time,aligned !or

synchroni ed$thus providing a comprehensive view of the entire grid at centrallocation.

A typical P"# installation as a part of wide area monitoring system !/A"0$networ% consists of phasor measurement units !P"#s$ dispersedly placedthroughout the electricity grid at strategic locations in order to cover the diversefootprint of the grid.

A Phasor ata Concentrator !P C$ at central location collects the informationfrom P"#s and provides alert and alarm for emergency situations as well asfacilitates development of different types of analytics for smooth operation of grid

on real time basis. -he P"# data is also transmit to 0upervisory Control andata Ac2uisition!0CA A$ system after time aligning the same. -he /A"0technology re2uires high bandwidth communication networ% for rapid datatransfer matching the fre2uency of sampling of the P"# data.

Phasor "easurement 3n 3ndia ,Phasor "easurement Practice in 3ndia4ational and 5egional 6oad espatch Centres in 3ndia are being operated byPower 0ystems 7peration Corporation!P707C7$8 a wholly owned subsidiary of P7/+5953 8 whereas 0tate 6oad espatch Centres are operated byrespective 0tate utilities. -hey are e2uipped with 0tate,of,the,Art 0CA A +"0

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system. -elemetry from different sub,stations and power plants are beingreceived at each 06 C 56 C and subse2uently to 46 C which are beingutili ed in day to day operations of the regional grid.

0ynchronous 3nterconnection of regional grids forming large interconnected

system!for example formation of 4+/ grid $ and various changes undergoing inthe 3ndian power industry re2uires better situational awareness of the grid eventand visuali ation at the control center for real time system operation. ;nowledgeabout the angular separation between different nodes of a power system hasalways been of great interest for power system operators. Phase anglemeasurement is commonly used in auto synchroni ation of generating stationsand chec% synchroni ation relays used at substations for closing of lines as wellas during three,phase auto,reclosing. All these applications are at the local level.

Prior to the introduction of Phasor "easurement #nits !P"#s$ at control centrelevel this analogue value is normally not considered as measurable in 0CA A

system and hence does not form a part of the 0CA A measurement. sin ,1 !P?@ 1? $. Angularinformation at control centre is also obtained by placing phase angle transducerat strategic locations and interfacing it in existing 0CA A system .