Problems Analysis and Improvement for Resistance Type Neutral DC Current Blocking Device Used in Converter Stations

Resistance Type Neutral DC Current Blocking Device has insufficient experience in design and operation on UHVDC station. Improve its operation reliability is of great significance to the safe and stable operation of related UHVDC systems. Analyze the Structure and Protection Principle of resistance type neutral DC current blocking device, Focus on the abnormal breakdown and adhesion and confirm that the device abnormal exit is the main cause of this block. The experimental platform has been built for the test of Voltage breakdown and current flowing of graphite gap, test the stability of device after the Voltage breakdown and current flowing. Propose to cancel the graphite gap protection function. Simulation calculation verifies that the thermal stability of the isolation resistor under different working conditions has stable operating ability. Proposed add delay logic for over current protection, proposed operation and maintenance improvement measures, etc. The conclusions obtained such as experimental and simulation calculation conclusions and improvement measures have certain guiding significance for converter stations using neutral DC current blocking device, it also has significance for the design in substations.