Data Acquisition System for Synchronous Generator Transient Performance

When a fault occurs in a system with a synchronous machine, the generator angle will increase and may behave as motor after the stability boundary has been exceeded. If the generator angle exceeds 𝛿max, shown below, the generator will slip a pole.

To combat this problem, it is necessary to create a fully automated system to acquire measurements from a synchronous generator under transient conditions. This project collects measurements such as speed, torque, load phase angle, terminal current, terminal voltage, field current, field voltage, and power from the system. This data will be used to create software and hardware to capture irregular measurements and protect the synchronous generator from their deleterious effects.

=Project Scope= This project requires selection, installation, programming, and reading of several sensor devices. The captured data must be synchronized and correlated carefully. Data must be transmitted to storage for retrieval on demand. Analysis of data in real time to determine appropriate response is an option. This project has the opportunity to operate several products from Schweitzer Engineering Laboratories to acquire data and to find appropriate responses to combinations of conditions within the measured data.

=Design= This is the data acquisition system topology. There are a total of 10 differential analog signals measured by both data acquisition devices, the PXI 6251 and the PXI 6289.



PXI 1052
This data acquisition chassis PXI-1052 has several mounting slots for various data acquisition devices.

PXI 6251
This data acquisition board is synchronized with the PXI 6289 and acts as a master device.

PXI 6289
This data acquisition board is synchronized with the PXI 6251 and acts as a slave device.

PXI 8360
This device is mounted in the PXI 1052 chassis and communicates with the PCIe 8361 in the PC.

PCIe 8361
This device is mounted in the PC via PCI and communicates with the PXI 8360 in the data acquisition chassis.

TB-2706
Analog signal measurement cables are screwed to the pins of these shielded terminal blocks. One block is screwed to each data acquisition board.

Shunt Resistors
We are using high accuracy shunt resistors to create a DC circuit to measure the field current and voltage. R1 is large enough and R2 and R3 are small enough that the leakage current is negligible.

Torque Transducer
The Himmelstein MCRT 48202(1-3) consists of three port connections: a 2-pin DC power input, a 3-pin RS232 serial connection, and a 4-pin analogue readout. We have used serial communication to a PC with the Himmelstein DT 482 software simultaneously with analogue capture into LabVIEW to map a relationship between the average digital torque measurement and the magnitude from the analogue measurement. The magnitude of analogue average torque is calculated by dividing the analogue peak by 1.18. The harmonics in the analogue are the same as the mechanical frequency. The figure below shows the correlation and regression of average analogue measured torque versus average digital measured torque.



Software
National Instruments LabVIEW

In order to ensure all measurements are properly time synchronized, both data acquisition boards must capture simultaneously. In LabVIEW, one DAQ is designated as a master device and the other DAQ is designated as a slave device. The figure below shows the same analogue signal being captured by both boards simultaneously with no time skew.



=Budget=



=Project Learning=

LabVIEW is the software platform allowing us to communicate, configure, and display data from National Instruments devices. It has the ability to communicate with a DAQ using instrument drivers VISA or interface driver.



The data acquisition boards share the maximum sampling rate across all channels. Adding more input channels will reduce the maximum available sampling rate.



The following block diagram shows the sampling logic of the SCXI. A multiplexer cycles through each input buffer, causing a slight timing skew between channels.



In order to determine the timing skew, we input the same signal into channels 0-3 and 13-15. The error was later determined to be negligible for our purposes.



If the error was of significance, we found a solution in a different type of SCXI. This device trigger holds each input for the multiplexer. This has the effect of perfectly simultaneous sampling at the cost of reduced sampling rate.



=Final Design= To be completed

=Validation= To be completed


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=Team Members=

=Additional Documentation=

Team Contract



Project Schedule



Meeting Minutes



Presentations