Fault to Earth and Electric Shock Protection System Minimising Stray Currents Caused by 3 kV D.C. Traction System
Demanded electric shock protection level in powering circuits of DC traction is achieved by fast break of fault current in high speed breaker (HSB). HSB’s breaking time capacity is no longer then 30 ms usually. The presented system, equipped with low voltage limiters TZD, guarantees breaking earth-fault current (after quick conversion the earth fault into a short-circuit between plus and minus poles with high value of current), assures the suitable electric shock protection level and minimization of stray currents.
The presented system consists off:
- earth fault protection devices mounted on feeder stations and sectioning cabins,
- low voltage limiters TZD (short-circuiting thyristor devices) mounted in open group bonding network,
- low voltage limiters TZD mounted for protection other constructions near traction powering line,
- TCK tester used for monitoring continuity of circuit between rail and minus bar in substation and for earth resistance measurement,
- diagnostic or measurement equipment: for earth resistance (IMR-4) of objects near 3 kVDC traction network , low voltage limiters tester TOZ for checking TZDs in terrain.
The system provides requirements:
- guarantees breaking earth-fault current in DC traction powering system,
- assures the suitable electric shock protection level,
- significantly limits stray currents.