Protection system of auxiliary three-phase circuits - SZDK

SZDK is designed to protect the power supply circuits of the locomotive's auxiliary systems

The system includes phase current sensors and voltage sensors, including a phase-to-ground fault sensor. The phase current sensors are split-core current transformers, and the voltage sensors are resistive dividers. The current sensors are installed on the power cables near the generator, before the first branching point, and the signals to the voltage sensors should come from the terminals of the farthest motor

To perform the overcurrent protection function, the device uses a selective algorithm that allows determining protection criteria depending on the generator's voltage and frequency, as well as the symmetry and duration of the overload

When the protection is triggered, the system generates a signal to activate the independent trip unit, which breaks the excitation winding power circuit of the generator. The trip unit control circuit is continuously monitored for open circuits and short circuits

The system includes an emergency recorder function that allows for the analysis of currents and voltages during the event that triggered the protection. During operation, instantaneous values of currents and voltages are recorded into non-volatile memory with a 0.5 ms period and can later be transferred to an external flash drive

De-energizing the excitation winding of the traction generator in case of:

1. An open circuit in one of the power phases
2. Phase-to-ground short circuit in the power supply
3. Phase-to-phase short circuit
4. Overcurrent

The project has been successfully implemented in Mongolia on locomotives of the series 2TE116UM, 2TE116UD, and 3TE116UD