Guardian CAT Terminal Principles
A Guardian CAT terminal consists of a grounded blunt lightning rod surrounded by an electrically floating medium. Rounded or blunt tips have proven to be more efficient than sharp points by producing minimal corona effect. This has been clearly proven in tests conducted at South Baldy Peak in the Magdalena Mountains of central New Mexico, USA. (Source: “The Measurement of Lightning Rod Responses to Nearby Strikes” by C.B. Moore, G.D. Aulich, and W. Rison/ May 2001)
During the static thunderstorm phase when the electric fields are steady at around 5-15 kV/m and even in the very early stages of leader approach, the medium presents as a relatively low field intensification surface due to the blunt configuration of the finial tip. This restricts the production of “corona” or “point discharge” ions and is critical because excessive production of ions (corona) results in a “space charge cloud” above the air terminal which masks the electric field at the tip of the terminal when the leader eventually approaches within range.
The Guardian CAT terminal is comprised of four separate electrically isolated panels arranged to allow the section facing the step leader to rise in voltage due to a capacitive coupling effect. Because the CAT terminal is essentially isolated from the ground potential, the electric field increases as the discharge approaches closer to the panel facing the step leader. It then experiences repeated pulsing until this section (panel) rises in voltage to the point when a triggering arc is generated at precisely the right time, which in turn initiates the streamer, which connects with the approaching down leader.
This triggering arc creates two key effects. First it produces a large number of ions which are needed to initiate an upward leader. Secondly it causes a large snap change in the electric field immediately above the air terminal which provides the necessary “kick” for the inception of an early, stable, propagating upward leader. The initiation of such advanced triggering results in the approaching leader being intercepted earlier, which ensures a larger protective area around the Guardian CAT terminal.
- Blunt finial tip which minimizes corona effect.
- 4 electrically isolated panels.
- High Voltage connection at the base.
- Triggering procedure allows the initiation of an intercepting streamer.