Evaluation of a Constant Parameter Line-Based TWFL Real-Time Testbed

This paper presents a testbed for real-time testing of Traveling-Wave Fault Locators (TWFLs). A Field Programmable Gate Array (FPGA) is used as the main hardware platform for conducting the real-time simulation. To accurately reproduce fault-launched travelling waves, the simulated power system is executed at a 500 ns time-step. The fault locating device is the SEL-T400L relay with a sampling rate capability of 1 MHz. The simulated grid is composed of constant parameter (CP) transmission lines (TLs). The paper presents the capabilities and limitations of such an approach and assesses the suitability of the line model for testing TWFL. Firstly, off-line analyses and validation are performed using EMTP. It is found that the CP line model can be incorporated in the double-ended TWFL testing setups. For the single-ended TWFL testing, it is shown that the CP line model can introduce false transients due to ground propagation mode which can affect testing accuracy. Secondly, real-time experimental simulations are done to elaborate the importance of sub-microsecond time-steps for testing of TWFL.