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Snubbers

Application

A snubber is an electrical apparatus that is highly effective in protecting medium-voltage transformers from electrical transients. It is a passive electrical device, cialis comprised of appropriately selected resistors and capacitors. While lightning arresters help protect the transformers from the high voltage transients that appear on the line after a lightning strike, order snubbers are more suited to the more common problem of transients that typically arise due to switching of circuit breakers in the system. Examples of the switching operation include instances where a circuit breaker switches between transformer primaries, or automatically triggered switching between grid and reserve power.

When a circuit breaker interrupts current flow, an arc develops across its contacts. The rapid current interruption usually occurs somewhere other than the current zero-crossing point, giving rise to a Transient Recovery Voltage (TRV), which has significant high-frequency content. If the transients are at the natural resonance frequency of the system, then there is a possibility of internal oscillatory voltages developing in the primary windings of the transformer. A high turn-to-turn voltage will result, which will lead to damage of the insulation.

The problem is further exasperated with modern vacuum-type circuit breakers, which have shorter distances between contacts. This serves to increase the speed of the interrupting cycle. The transient level and frequency are functions of the physical distance between the breaker and transformer, transformer construction, the type of load being switched, and the switching characteristic of the breaker.

The RC-snubber network lowers the frequency of the transient voltage applied to the transformer primary below the resonance frequency of the circuit. It reduces the development of the oscillatory voltages and provides a low impedance path to ground for the transients.

Snubbers are a low cost means for protecting a transformer against a costly repair and related downtime. In designing medium voltage power systems, it is a good practice to at least leave space for future installation of a snubber network.

Available sizes & Construction

Rex Power Magnetics can supply snubbers separately or as an option that is available for its power transformers. The Resister and Capacitor are also mated with a fuse for protection of these components.

Rex snubbers are available for primary voltage levels 480/600 up through to 46 kV. Specifically, designs are available for the following voltage levels:

  • 2400 V
  • 4160 V
  • 13.8 kV
  • 18 kV
  • 26 kV

Please contact our engineering department for details: This email address is being protected from spambots. You need JavaScript enabled to view it.