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What is switch syncronisation?


Many powergrids today are characterised by the long distances between generation and consumers. Therefore, long wires with variable loads are common. That brings the use of capacitor banks to compensate the loss of effect. Switching these banks causes transients. The transients causes problems on the power grid.


Therefore some breakers are connected with switch sync mechanisms, which allows the breaker to operate at voltage zero crossing. By point-on-wave switching at the most appropriate moment, inrush currents or repercussions can be reduced to non-critical values.


Shunt capacitor banks

Basic aim is to control closing, to minimise the energising transients (voltage transients as well as inrush currents). To improve interrupting performance, controlled opening can also be utilised.


Shunt reactors

Basic aim is to control de-energising to ensure reignition-free behavior. In addition, controlled closing also serves as a useful method for minimising inrush currents.


Switch control

No-load transformers

The purpose of controlled no-load transformer switching is to minimise the inrush currents (and voltage distortion) by taking residual flux into account. Depending on the type of application and type of controller, controlled opening can serve as support for controlled closing.


No-load overhead lines

Controlled re-energising or energising of overhead lines ensures minimised switching transients.


The SA10 equipped with an FSU30 offers you the following measurement possibilities

When using FSU10 together with the SA10, you can fully test your controlled switching CB's. Line currents and voltage are displayed at the same time as any other inputs connected to the breaker.

Analysis is made manually by oscilloscope functions or automatic by the software representing numeric results. Limits and warnings can be implemented if required.

To verify the switch sync performance, the following should be recorded:

  • Busbar voltages (or at least the reference voltage)

  • Current in each phase

  • Output commands from controller

  • Functioning times of precision auxiliary contacts (if adaptation control is used)

  • Monitor the signal from the control room that initiates the relay.

  • See the signals out from the relay to the breaker trip and close coils.

  • The main contact can be connected to verify the switching.

The equipment

The FSU30 (Art.No: S155) is a plug-in box to the SA10 and it is delivered complete with current clamps for easy testing. This equipment also allows for first trip measurement.


First trip analysis 2

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