Page 62 - From Smart Grid to Internet of Energy

48 From smart grid to internet of energy

and rapid frequency response capabilities of PMU provides accurate detection
of power network disturbances. The application areas of PMU include advanced
network protection and advanced control besides real time monitoring of power
networks [4, 7, 28].
The PMUs play crucial role in wide area monitoring of power systems due to
its rapid and accurate measurement capability. PMUs associated with IEDs are
used for fault detection, fault recording and advanced protection controls. The
acquired and processed measurements are transmitted to phasor data concentra-
tors (PDCs) with tagged time stamps in a high-speed transmission technology
where maximum delay should be lower than 20 ms and each measurement is
repeated between 20 and 100 ms intervals. PDCs are located at monitoring
and control centers and proceed power network monitoring depending to anal-
ysis of different measurement data acquired at independent nodes and IEDs.
The analyzed data of PMU and PDC provide real time monitoring of power
network, detection of any disturbances along power network, immediate power
flow control, accurate and instant detection of faults and fault locations, and
utilization monitoring [14].
The PDC is used to combine several PMU or PDC data together and assigns
time stamps for each data set to transmit combined data stack to microprocessor.
PDCs uses data buffer to cope with time delays occurred during transmission
from sensors to PMUs and data packet latencies. The data streams are stored
in data buffer in order to wait compilation of each PMU data receive and then
aggregated data sets are transmitted to microprocessor at one interval. The
PDC provides data checksum control, validity check, integrity and complete-
ness controls to detect if there is a faulty data exists in dataset. PMUs operate
according to particular standards such as IEEE 1344, IEEE C37.111 and IEEE
C37.118 for data format, data rates and data acquisition operations, and several
communication protocols as TCP, User Datagram Protocol (UDP) and Internet
Protocol (IP) for data stream process. There are three types of PDCs as substa-
tion PDC, control center PDC, and super PDC are used in WAMPAC applica-
tions. The substation PDCs are also known as local PDCs that are located in
substations to collect datasets from various PMUs and perform communication
along the control center.
The latency of substation PDC is as low as possible since it is very close to
PMU sources in substations, and it is used as local substation controllers. The
substation PDC stores acquired data in very short intervals to prevent data loss
against any communication failure. Therefore, it collects measurement data and
immediately transmits. The control center PDC is associated with PMU of any
field device, substation PDCs, and other neighbor control center PDCs. It is
capable to collect and transmit very long data sets generated from multiple
devices and applications in the field. It is compliant with plug-and-play type
device integration to utility grid, with new protocol and data formats, and
new applications. The super PDC is on the top of hierarchical organization com-
prised by local PDCs, and control center PDCs. It is used to combine wide