A DEMO WIDE
AREA MONITORING SYSTEM
Introduction
Grid operations are
complex in nature and it is becoming more complex when system to be
maintained under strict grid codes and operational efficiencies. When
system stretching limits/optimal loading of power system equipments
are to be determined dynamically, availability of real time data
representing real time network conditions (V, Hz, angle) becomes
very critical. SCADA systems are widely deployed in transmission and
grid operation centers for monitoring of the network parameters,
which updates data only at every 5,10 seconds hence data will not
represent real time state of the network. Usually to represent
dynamic state of system the information
need to be acquired in milliseconds.
In AC power system, Power
flows from a point of high voltage angle to a point of low voltage
angle. The higher the angle the greater the power flow, hence
determination of angular displacement and its magnitude (phasors) is
important. Synchronized measurement of phasor plays an active role in
determining stability of the power system as angular displacement
(power angle) determines the stability of the network system.
Following events can change voltage angle to increase or decrease
- Unscheduled power transfers between source and sinks.
- Transmission lines removed (forced or scheduled) from service between source and sink, without adjusting schedules.
- Loss of generation in the sink area.
- A sudden load throw
General applications
of synchronized phasors data
- Use of real-time PMU data for improved situational awareness
- Oscillation monitoring(analysis of sustained oscillations)
- Voltage stability Analysis
- Supervised Zone 3 protection function
- System protection scheme using PMU data
- Transfer capacity calculation
- CT/CVT calibration
Phasor
measuring unit (PMU)
PMU (Phasor Measurment Unit) derives magnitude and power
angle of the voltage and current with respect to a reference signal,
which is generated from a synchronized GPS clock. As the PMUs are
synchronized to single clock system (GPS), the data collected will
have a common time stamp reference to UTC time. The collected data
will be sending to a phasor data concentrator located at control
centre over IEEE C37.118 communication protocol and updates to master
station at a rate defined by user and measurement requirement,
usually 25,50,10 samples/second.
Wide Area monitoring system for a Load Disptach Center
Kalkitech’s Wide Area monitoring system (WAMs) comprises Phasor Measurement Units(PMUs) of model NI Compact RIO, Phasor Data Concentrator(PDC) of model Kalkitech SYNC4000 and a Historian and visualization system. PMUs are installed at three major locations as indicated by the below figure, in southern region and sends phasor data to the regional load dispatch control centre(RLDC) for real time monitoring and system analysis. The main objective of the pilot is to derive applications using PMU data and understand the capabilities of communication systems available with the transmission operator and its readiness to take up PMU project and also to understand specific features required in the southern sub system operations.
Wide area monitoring applications and phasor data concentrator(PDC) are installed at RLDC control centre and each PMU communicates to control centre over dedicated 64 kbps utility telecom network(E1 network). V.35 modems located at each PMU site provides necessary interface for the PMU to connect to the ULDC network. At control centre PDC time aligns the C37 frames of PMUs and output to the historian and OMS(oscillation monitoring system) application and also provides protocol conversion on ICCP and IEC-879-5-104 for SCADA. The application server has visualization tools and storage application providing displays for phasor monitoring, oscillation monitoring enhancing situational awareness. The information derived from the applications can be used for planning system operation during contingencies.
WAMS user interface
Fig: Oscillation monitoring system and Hz & df/dt plots
