Documents

All documentation related to the project

P.H.A.T.C.A.T.

Phasor-Harmonic Analysis for Transformer Assesment and Telemetry
On all fronts—academic, political, and industrial, there is a great deal of change and growth occurring in the electrical power industry. This comes after a period of long stagnation which has resulted in a high need for educated, young power engineers. One key facet of power systems is their protection and control. Sparked by a desire to both learn and create a needed educational resource, PHATCAT was conceived to provide insight into the design and functionality of modern microprocessor relays, which are the heart of the power system’s protection and control.

Subsystems

ADCs
P.H.A.T.C.A.T uses two external ADS8588S analog digital converters to process the six voltage & eight current inputs. The A.C signals which P.H.A.T.C.A.T will be monitoring will swing from both the positive and negative rails. By using a bipolar input, the ADS8588s eliminates the need for additional hardware. Through the process of the internal low-pass Butterworth filter and oversampling of the ADC, we eliminate the antialiasing that can occur by switching between the analog to discrete-time signals. Lastly, the ADC uses simultaneous sampling to take all eight inputs and keep the phase consistent between each input. This is useful when considering the use of the FFT in the protection algorithms in the software. performing correctly.

Desktop Application
The desktop application was written in python 3 to allow the user to configure the device. It used pyserial to be able to communicate with the device through UART. Which would send and receive the settings between it, and the TI F28379D MCU

TMS320F28377S
The TMS320F28377S was the MCU of the project and handled all of the protection algorithms. This also made it possible for us to develop on the LAUNCHXL-F28379D developmement board and fine tune all our embedded programs before flashing to the main board. MCU

Transformer Protections

Instantaneous Overcurrent:
Provided for both phase and ground currents, PHATCAT has instantaneous overcurrents which operate when the measured current reaches a user-defined threshold.

Time-inverse Overcurrent:
Provided for both phase and ground currents, PHATCAT has time-inverse overcurrent functions that offer an operating characteristic with operation time decreasing exponentially as fault current increases. PHATCAT supports user-definition of the pickup value, time dial, and standard U.S. relay curve to define this characteristic.

Restrained Differential:
Intended as the primary protection for power system transformers, PHATCAT has a restrained current differential operation that operates based on the difference between the transformer’s input and output current for each phase. Minimum pickup and percentage slope values can be set to decrease the function’s sensitivity for large external faults that might otherwise cause misoperation.

Overexcitation:
PHATCAT has an overexcitation element that looks at the per-unit ratio of overvoltage to underfrequency to provide protection against excessive flux in the protected transformer’s iron core.