A speculative survey on pmu

A Speculative Survey On PMU

(Phasor Measurement Unit)

Under the guidance of Mr. Koushik Neogi, our project coordinator.

Submitted by:

Sl.No. Name Roll No.

1. Supriya 10801610010

2. Dipkanta Mondal 10801610014

3. Dali Das 10801610020

4. Vivek Mitra 10801610023

5. Pintu Khan 10801610028

Contents…. Introduction What is Phasor? What is PMU? Inside PMU Communication Infrastructure Of PMU Phasor Data Concentrator (PDC) Smart Grid

INTRODUCTION 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 condition.

PMUs were introduced into power system in 1980s and in recent years, varieties of PMU applications have been studied, proposed and implemented with their significant benefits.

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 protective device.

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 measurements.

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. 

Inside PMU• Block representation of PMU:

Inside PMU(Continued)….

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 errors.

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

locations. 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 PMUs

Communication infrastructure of PMUs (continued)….

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 phone lines.

Phasor Data Concentrator (PDC)

Phasor Data Concentrator (PDC) continued….

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.

Smart GridA 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: Reliability Flexibility in network topology Efficiency Load adjustment Sustainability

MICROGRID A microgrid is a localized grouping of electricity generation,

energy storage and loads. It normally operates connected to a traditional centralized

grid (macrogrid). 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

blackout.

A typical Microgrid is shown below:

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 supplied.

•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 KarchamWangtoo.

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

synchrophasor initiative

•Integrate regional pilot projects at the national level.•Establish Quality of Service (QoS) norms for Indian conditions

Explore application of synchrophasor

data in

•Adaptive protection and control•Transmission planning and generation siting•Calibration of instrument transformers

Capacity building for improving

comprehension/interpretation of synchrophasors

•Create a library of grid incidents and events characterized in phasor data.•Establish a policy / mechanism for sharing synchrophasor data