Scientific and technical recommendations

BOLID can provide computer simulation of electromagnetic processes under transient and steady state conditions in 6-35 kV networks.

We offer the following investigations and calculations:

  • Transient processes at single line-to-ground faults, including intermittent arcing faults.
  • Quasi-stationary processes under stable and unstable ferroresonance conditions with voltage transformer core saturation.
  • Transient processes at transformer switching, motor switching, and others, by various high-voltage circuit breakers (e.g. vacuum circuit breakers).

These investigations and calculations allow:

  • Determining of overvoltage levels on unfaulted phases at ground faults, including faults in networks with ground-fault neutralizers having various detuning ratios.
  • Evaluating of possibilities for ferroresonance phenomena development and determining of voltage transformer primary currents in comparison with values permissible by thermal stability.
  • Determining of switching overvoltage levels after a circuit breaker and at equipment terminals when feeders are switched by vacuum circuit breakers.

After investigations and calculations, we develop recommendations on neutral grounding, such as: implementation of compensation and overvoltage limitation methods at single line-to-ground faults, connection of resistors to the neutral circuit, tuning of ground fault neutralizers in 6-35 kV networks. If required, we can choose surge suppressors for 6-110 kV networks.

Implementation of such arrangements allows:

  • Getting experience of resistance-grounded system operation.
  • Protecting equipment insulation from overvoltages at single line-to-ground faults.
  • Solving a problem of the transition of single line-to-ground faults to short circuits.
  • Providing ground relay selectivity with guaranteed faulty feeder detection.
  • Increasing of power supply reliability

For calculations and investigations, you should provide the following information:

  • Power system diagram with all loads (all electrical consumers) shown.
  • Lengths, markers and types of cables and overhead lines.
  • Specifications on installed equipment.
  • Availability of ground fault neutralizers.
  • Instruction on capacity current compensation at single line-to-ground faults.
  • Possible emergency and maintenance conditions.
  • Specifications on installed ground relays.