A Speculative Survey On
(Phasor Measurement Unit)
Under the guidance of Mr. Koushik Neogi, our
What is Phasor?
What is PMU?
Communication Infrastructure Of PMU
Phasor Data Concentrator (PDC)
The electrical grids are amongst the most complex systems worldwide.
Traditionally, the power system protection and control was designed for protecting
the power system from the large disturbances due to the faults.
However the lessons from several recent major blackouts indicate that current
protection systems were not always sufficient to slow or stop an uncontrolled
cascading failure of the power system and the application of existing protection
system should be revisited.
The increasingly installations of synchronized phasor measurement units (PMUs) in
power grids have made it possible to improve power system protection and control.
Synchronized phasor measurements are ideal for monitoring and controlling the
dynamic performance of a power system, especially during high-stress operating
PMUs were introduced into power system in 1980s and in recent years, varieties of
PMU applications have been studied, proposed and implemented with their
In our current power grids, a large number of PMUs also have been installed and
more will be installed.
The wide area measurement system (WAMS) that gathers real-time phasor
measurements by PMUs across broad geographical areas has been gradually
implemented across the United States.
What is Phasor?
Rotating “Phase Vector”
An alternative expression of a sine wave.
A phasor can express voltage or current at any point
in a power grid.
Phasor representative of a sine wave:
What is PMU?
PMU is essentially a digital recorder with synchronized capability.
It can be a stand-alone physical unit or a functional unit within another
By measuring the magnitude and phase angles of currents and voltages a
single PMU can provide real-time information about power system events
in its area, and multiple PMU can enable coordinated system-wide
PMU also can time-stamp, record, and store the phasor measurements of
power system events. This capability has made PMU become the
foundation of various kinds of wide area protection and control schemes.
In power engineering, these are also commonly referred to as
synchrophasors and are considered one of the most important measuring
devices in the future of power systems.
The analog input signals are obtained from the secondaries of the voltage
and current transformers.
The analog input signals are filtered by anti-aliasing filter to avoid aliasing
Then the signals will be sampled by the A/D converter.
The sampling clock is phase-locked to the GPS time signal.
The GPS receivers can provide uniform time stamps for PMUs at different
The phasor microprocessor calculates the values of phasor.
The calculated phasors and other information are transmitted to appropriate
remote locations over the modems.
Communication infrastructure of
Figure above illustrates the PMU communication infrastructure, where a
hierarchical structure is used.
PMUs first send the data to their respective data concentrators, where those
data concentrators are connected to a centrally located data concentrator in a
central control station.
And the data concentrators are connected locally to their respective host
computers via ethernet.
The communication between a PMU and the data concentrator is carried over
Phasor Data Concentrator (PDC)
In the PMU communication infrastructure the PDC serves as the hub of the
measurement system, where data from a number of PMUs or other PDCs is
brought together and then fed out to other applications.
The PDC correlates phasor data by its timetag and sample number to create
a system-wide measurement set precisely synchronized in time.
It also performs quality checks on the data and inserts appropriate flags
indicating data quality into the correlated data stream.
Besides, the PDC also performs extensive functions in the measurement
system as shown in Figure above.
It buffers the data stream internally and spools it out to other applications.
It can send out a continuous stream of all data over ethernet or selected
data based on application or flag status.
The PDC also monitors the overall network and includes a network client
program for user access.
Therefore, the specific program on the PDC can indicate system
disturbances and records a file of data once disturbance occurs.
A smart grid is a modernized electrical grid that uses information and
communications technology to gather and act on information, such as
information about the behaviours of suppliers and consumers, in an automated
fashion to improve the efficiency, reliability, economics, and sustainability of
the production and distribution of electricity.
Features of the smart grid:
Flexibility in network topology
A microgrid is a localized grouping of electricity generation,
energy storage and loads.
It normally operates connected to a traditional centralized
The microgrid can function autonomously.
Generation and loads in a microgrid are usually
interconnected at low voltage.
Microgrid generation resources can include fuel cells, wind,
solar, or other energy sources.
Micro-grids were proposed in the wake of the July 2012 India
PMU in Smart Grid
High speed sensors called PMUs distributed throughout
a transmission network can be used to monitor the state
of the electric system.
In the 1980s, it was realized that the clock pulses from
global positioning system (GPS) satellites could provide
very precise time signals to devices in the field
A wide-area measurement system (WAMS) is a network
of PMUS that can provide real-time monitoring on a
regional and national scale.
Smart Grid is the integration of new technologies that
allow Utilities and Suppliers to rethink electric grid
design and operations.
Synchrophasor and Future………
• Phasor Measurement Units have progressed from the
evaluation stage to operational tools and a valuable source of
post disturbance data.
• Future work involves integrating the data into protection and control
schemes which will improve the reliability and quality of the power
• In this paper, a new concept for synchronized testing of PMUs and WAMPAC
applications during steady state and transient conditions will be presented. An
attempt to define standardised voltage and current signals will be given, as well.
Overview of the synchrophasor initiative in India
In India, fourteen (14) Phasor Measurement Units (PMUs) have been
commissioned as on 31st May 2012.
In the Northern Region, the PMUs have been placed at nine 400 kV
substations viz. Vindhyachal (HVDC back-to-back station), Kanpur (with SVC),
Dadri (HVDC inverter terminal), Moga, Kishenpur, Agra, Bassi, Hisar and
Western Region PMUs have been placed at two 400 kV substations viz.
Raipur and Bhadravati.
In Southern Region, they have been placed at three 400 kV substations viz.
Salem, Hyderabad and Bengaluru.
The three Phasor Data Concentrators (PDC) have been installed at the
respective Regional Load Despatch Centres (RLDCs) located in New Delhi,
Mumbai and Bengaluru.
The WAMS in Western and Southern Region are demonstration projects,
while in the Northern Region the expenditure under the pilot project was
approved by the Honourable Central Electricity Regulatory Commission
(CERC) and funded from the Unscheduled Interchange Pool Account.
Suggestions and scope for future work
Ramp up all activities related to
Explore application of
synchrophasor data in
• Integrate regional pilot projects at the national
• Establish Quality of Service (QoS) norms for
• Adaptive protection and control
• Transmission planning and generation siting
• Calibration of instrument transformers
• Create a library of grid incidents and events
Capacity building for improving
characterized in phasor data.
• Establish a policy / mechanism for sharing