TERMINOLOGY

Bi-directional TVSS

Conventional surge suppressors are connected between the hot, neutral and ground wires.  A transient detected on any of the connections will fire the suppression device, creating a circuit to shunt the fault current. When the ground wire is the source of the transient the surge protector "back-fires" - fault current flows from the ground to the neutral connection and then to the protected equipment.

 

Circuit Isolation

Opening the AC circuit obviously isolates the powered equipment from faults on the AC power service.  Additionally, opening the AC circuit further isolates the equipment by eliminating the secondary fault paths between the terminal ground and the power neutral system, and between the telco lines and the power neutral system.  Circuit isolation eliminates the lower, remote ground reference that induces fault current.

 

L-GPR

During a lightning event very high voltage is concentrated in the immediate strike area of the earth – earth voltage rise or Ground Potential Rise.  The difference between this local, high voltage and remote, lower voltage ground references produces strong fault current across the earth’s surface.

 

Induction

Current flow produces a magnetic field around the conductor that induces additional voltage in the conductor in the opposite direction of the current flow.  As the magnetic field expands, inductance opposes the increase of current.

 

Impedance

Impedance is a measure of the opposition of a circuit to alternating current. Impedance includes resistance, capacitance and inductance.  Resistance is the opposition to steady direct current.  Inductance and capacitance are components in opposition: inductance is proportional to the frequency of alternating current, and capcitance is inversely proportional.

 

Multi-grounded neutral system

The commercial power neutral is grounded at multiple locations – the substation, transformers and power pedestals. Similarly the telco shield is grounded at multiple locations along its path between the central office, remote terminal and subscriber.  These grounding networks are bonded together on the common ground buss of remote terminals, effectively creating an extended neutral ground system.

 

Parallel or secondary impedance paths

A parallel impedance path is an alternate path for current.  In a remote terminal, elevated voltage on the ground buss will "back-fire" the surge protector, creating a secondary path through the protected equipment to the lower ground references on the power neutral system.

 

Phase shift

Phase shift means the current and voltage are out of step with each other.  This is produced by the inverse proportionality of inductance and capacitance to the frequency of alternating current.

 

Pre-emptive isolation

The Lightning Shield detector identifies impending lightning strikes and proactively opens the AC Service, isolating equipment before the strike event.

 

Safe-mode

Safe-mode refers to re-connecting AC power at the the zero voltage cross-over point of the AC sine wave; power-up will produce minimum loading (in-rush current) on the circuits.

 

Saturated grounding system

Severe lightning can momentarily exceed the grounding system’s ability to dissipate instantaneous energy.  The fault current will seek alternative dissipation paths.

 

Single point grounding

A single point ground is a single ground reference; in other words, the absence of other potential references. Fault current can not flow in the absence of a second potential reference.  Unfortunately, the the single point ground configuration at a site is pre-empted by the safety ground connection between the site and the AC power neutral ground.