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High Voltage Isolation Units
     Noramco makes High Voltage Isolation Units (HVIUs) which protect telecommunications equipment from damage, and personnel from injury, when high-current faults develop in power plants or substations. These faults most often occur when lightning or wind causes power lines to short-circuit. But sometimes these faults occur without warning when power generation or transmission equipment fails.

     The high fault currents are conducted to ground, and travel through the ground, producing high-voltage surges called Ground Potential Rise (GPR). These surges can get on the metallic cable circuits which are used for substation monitoring and control, metering, protective relaying, and voice telephones. These surges may exceed 10,000 volts and last much longer than a lightning strike; no common surge protector can survive.

     NORAMCO's High Voltage Isolation Units keep the surges out of the equipment and out of the voice telephones. Communications continues uninterrupted on these critical circuits. The utility's equipment is able to report the problem, and the utility dispatchers can command the equipment to restore service. For more detail, see pages titled The Need For High-Voltage Isolation and Technologies for Isolation.

     Noramco makes several series of isolation units for different types of circuits:

For isolating meter pulses into demand recorders:
6011 HVIU to isolate one set of KYZ meter pulses plus timing pulse
6063 HVIU to isolate three sets of KYZ meter pulses plus timing pulses

 

For isolating one dialup voice telephone line (Plain Old Telephone Service, "POTS"):
7395 HVIU for most tone/pulse-dial circuits
7395-500 HVIU optional wink-off adapter for forced disconnect of automated dialup equipment

 

For permanent tone telemetry data circuits (SCADA):
7547 HVIU for 2-wire and 4-wire data circuits
6547 HVIU for 1-4 2-wire data circuits, or 1-2 4-wire circuits, rack mount

 

For a typical substation's telephone cable enterance:
6030 HVIU for one 4-wire data circuit and one 2-wire dialup voice telephone line

 


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