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Transmission Line Protection
PCS-996 Phasor Measurement Unit
In order to improve the dynamic stability monitoring and analysis abilities, Phasor Measurement Units (PMUs) are installed in the corresponding substations and power plants. Furthermore, the use of a wide area measurement system (WAMS) serves to view the system’s state from the dispatching center.
The PCS-996 Phasor Measurement Unit (PMU) is mainly applied for the measuring synchronized phasor, and the recording dynamic process of the power system. The PCS- 996 consists of Phasor Measurement Units (PMU) and phasor data concentrators (PDC). The core phasor measurement unit characteristics include the synchronized phasor measurement, based on standard clock signals and timekeeping capacity without the standard clock signal. In addition, the system is designed to achieve high-speed communication capacities between the localized PMUs and the central WAMS. The standard communication protocol is IEEE C37.118. A PDC is used to collect data from several PMUs, and then the PDC sends the data to the WAMS control center. In addition, the auxiliary function of the local storage of the phasor data can be equipped with PDCs. WAMS consists of PCS-996 series PMUs and PDCs, a clock synchronization system, high-speed communication network equipment and the analysis systems of the master substation. Furthermore, WAMS can realize dynamic process monitoring and analysis of the regional electric network and the cross-regional electric network.
The PCS-996 Phasor Measurement Unit (PMU) relies on GPS time signals in order to provide extremely accurate time stamping for the power system’s information. The measured vector quantities are sent to the control center in effort to provide a basis for monitoring, protecting and controlling power networks.
PMUs are installed in substations and power plants as a part of the Wide Area Measurement System (WAMS). PMUs improve the system’s economic operation and enhance power stability and protection against any severe disturbances. PMUs installed in different locations are synchronized by a GPS clock. If the GPS source is lost, an internal high-precision clock source is used as a fallback.
Phasor Data Concentrators (PDCs) receive and store the synchronized phasor data from PMUs through optical fibers, and send the collected information to the WAMS in real-time. One phasor data concentrator can communicate with more than eight WAMS stations.
Integration to WAMS
The PCS-996 fully supports communications to the Wide Area Measurement System (WAMS) based on international protocols (IEEE Std C37.118-2005, IEC 60870-5-103 and IEC 61850). The measured phasors are transmitted from PCS-996 to WAMS via a communication network and assembled for advanced supervision and analysis. This allows direct phasor comparison from various locations in the power system.
Integration to PSCS
The measured phasors can be transmitted from PCS- 996 to the Power Stability Control System (PSCS) for stability control. In case of an imbalance between power generation and load or severe power oscillations due to system disturbances, PSCS can take fast and reliable emergency actions, such as: generator shut-down, load-shedding, etc. These actions are taken in effort to ensure the system’s stability and in defending the power system against blackouts.