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Model SVI-50 11V BLOCKER® Stray Voltage Isolator

BLOCKER Stray Voltage Isolator


Off-site stray, or neutral-to-earth (NE), voltage can result from primary neutral currents, off-site faults, or marginal groundings. Ronk BLOCKER is designed to reduce the off-site contributions to the stray voltage, allowing the utility to focus on the on-site sources.

The device operates directly on the principle of magnetic saturation and does not depend on external controls or internal logic signals; therefore, it reacts instantaneously, providing immediate, continuous protection at all times.

Tech Spec | Installation Instructions | Stray Voltage Investigation


Model: SVI-50 11V
Series: BLOCKER Stray Voltage Isolator
Blocking Volts: 11 V
Energy: 10,000 Joules
Impedance: 0.01%
Peak Current: 80,000 A
Peak RMS: 100 V
Weight: 14 lbs. (approx.)
Enclosure: NEMA 3R aluminum

NEMA 3R Enclosure

Enclosure Dimensions

Configuration & Description

BLOCKER is installed between the primary and secondary neutrals of the distribution transformer.

BLOCKER has a very low impedance (less than .5 Ohms) for a voltage level above 12 V. This provides the fault current path in the event of a primary to secondary short in the distribution transformer (with a 7,200 V primary, the voltage drop of 12 V across the BLOCKER is less than 0.2% and is, therefore, negligible).

Typical Applications

  • Dairies
  • Homes
  • Swimming pools
  • Fountains
  • Swine parlors
  • Poultry farms

Application Notes

  • Role of the Ronk BLOCKER
    The BLOCKER®, a neutral isolation device, is placed in the interconnection of the primary and secondary neutral. It has approximately 2000 ohms resistance at 6 volts and drops to approximately 1500 ohms at 9 volts [more...]