Short circuit emulator

This unit generates controlled short circuit events in a laboratory model grid.

It has two main usages:

• Expose a model grid to a defined short circuit event.
• Create dips in the supply voltage in order to see how various types of equipment responds.

Design data:

• Nominal grid voltage 400V
• Continuous current: 225A RMS
• Short circuit current thyristors: 1400A RMS.

Shorting is performed by triac connected thyristors.

Two inductors, the series inductors and short circuit inductors determine the short circuit current level and the depth of the voltage dip. These inductors are placed outside the unit, on each side of the cabinet, so that they can be easily changed. By using inductors with large airgap or air core saturation at peak short circuit current is avoided.

The series inductor limits the current drawn from the supply grid during the short circuit event. It can be shorted by a bypass contactor in normal state, outside the shorting events.

Voltage dip depth is determined by the ratio between the short circuit impedance and the sum of the short circuit impedance and the effective series impedance, which includes the supply grid impedance

Shorting is synchronized to grid voltage, delayed by an adjustable phase angle.

1, 2, 3 phase short circuits can be applied.

The short circuit event last for a preset time.

At the end of the short circuit event the thyristors remains on until the current reaches zero. This is similar to the behaviour of a short circuit arc in a real grid.

Short circuit emulator unit