Copel GT experiences

Authors: G. F. Krefta, COPEL GT, and C. E. F. Pimentel, GE Grid Solutions, Brazil

The measurement of electrical phasors, analogs signal and digital signals that inform the behavior of the power system can be acquired at the same base of time applying the Phasor Measurement Unit (PMU) based on the protocol IEEE C37-118-2011. It means that one disturbance in the electrical power system interconnected can be analyzed from a thousand kilometers far, at same base of time.
Synchrophasors that are components of PMU can be defined as phasors calculated in separate facilities, geographically distant, using the same time reference. There is a need for a single time reference, i.e. Synchronization. Figure 1 shows the concept of Synchrophasors.

In addition, current SCADA systems are not able to show to system operators dynamic behavior of the system, so utilities in general operate their system using large security margins to avoid system blackouts and use data from relays or Digital Disturbance Recorders (DDR) to analyze a system disturbance. However, this approach is not always cost effective, quick or easy to perform, as there is the need to use different systems and equipment, which are not always time synchronized or have same accuracy. Thus, Synchronized Phasor Measurement Systems (SPMS), also known as Wide Area Measurement System (WAMS), were developed and have been increasing their usage in power utilities.
WAMS systems had been recognized as the main alternative to improve real-time monitoring of power systems. These systems, composed by Phasor Measurement Units (PMU), communication system and Phasor Data Concentrators (PDC), have the advantage to have their measurements time-synchronized by a common time base, which makes it possible to compare directly measurement from all system installations to visualized real-time power system conditions in terms of angles between busbars.
Brazilian utility Copel G&T has been facing these challenges in the last years and, in 2015, commissioned its first WAMS where the benefits of this new system and applications are being applied to the company.

Copel's GT Wide Area Measurement System

The system was initially composed by 37 PMU, function that is embedded in their DFR system, distributed in all Paraná State territory, located at Brazilian south region. By now the system is composed by 59 PMU and cover the north, northeast and southeast regions of Brazil while new power plants and substations were built by Copel GT. Two central PDC servers, installed in Copel's control center, receive data from the PMU installed at the substations, and PMU send two streams of data to each PDC. As there is no substation PDC from PMU and central PDC, there are distances over 3,300 km from the substations where the PMU are installed and the control center, where the PDC receives PMU data. Figures 2 and 3 show system architecture.

After the first year of operation, the company stated to increase their PMU database, including also generator measurements in low side and electromechanical signals, such as generator current and voltage, governor position, voltage regulator values, power system stabilizer signal (PSS) and even digital signal to check if operation is performed by Brazilian National Operator (ONS) or locally by Copel. Initial experiences lead the company to adopt these signals, as it was noted that system observability would increase significantly with these signals.

Thus, hydroelectric power plants (totalizing 4,436 MW) were included in the system. Finally, as Copel's wind generation is increasing in the last years, it also included more than 800 MW wind farm, which is in Brazilian northeast region, more than 3,000 km far from Copel's control center. Figure 5 shows an example of the main screen of the WAMS system in operation currently in Copel.
Experience acquired by Copel's personnel in WAMS usage shown that, even though there is a big advantage of using angle differences to operate the system, which nowadays only WAMS systems can perform, there are several additional benefits that these systems offer to utilities, even though if they don't have autonomy to operate their system, as it is Copel GT case in BIPS.
Having a single database, time-synchronized and with the resolution that a PMU can perform, increases significantly the capacity of operators to diagnose and increase operational margins, using their assets better, even though it is not used mainly angle differences. Synchrophasors measurement treated on the PDC operating in the Copel GT is presented as a multifunctional tool included in the concept of smart grid, way beyond the proposed angle between busbars and which came to complement the SCADA system and do not replace it.

The picture in Figure 4 shows resolution difference between SCADA and WAMS. The first does a scan of 4 to 3 seconds while the second system makes a reading every cycle. The result is that when you overlap those two systems measurements, the SCADA system showns a single data point of active power while the WAMS describe an entirely electromechanically oscillation of the system.

Figure 6 shows a SCADA system screen where PMU frequency data were imported from PDC using DNP3 protocol, showing an example of how to integrate both systems.

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