Rings on high voltage connectors?

[Edgardo]

Hi all,

I'd like to know what these rings at high voltage connectors are good for:
http://www.surplec.com/hvt_polemount_shipping.jpg [Broken]
http://www.surplec.com/hvt_inventaire_15.jpg [Broken]
http://www.recursivemediaone.com/high%20voltage%203%20gs.jpg [Broken]

 

[Integral]

It is my understanding that the rings serve to increase the surface distance from the conductor to ground. Thus preventing arcs.

 

[Astronuc]

The rings are ceramic insulators to insulate the high voltage line from the connectors and the pole to which they are connected, or in the case of the transformer, insulate the high voltage cable/wire from the metal casing of the transformer. The transformer may be attached to wood pole or may sit on a metal frame.

The rings also provide a discontinuity, so that a continuous conducting path does not form, especially when it rains (water with impurities conducts).

Insulators do accumulate dirt (fine particulates, dust, bird droppings and mold). Periodically, they need cleaning.

 

[berkeman]

It is my understanding that the rings serve to increase the surface distance from the conductor to ground. Thus preventing arcs.

That's correct. There are generally two distances that you are concerned with when insulating a high voltage circuit -- "creepage" and "clearance". The clearance distance is the distance through the air between the HV conductor and Earth or any other low-voltage conductor. The creepage distance is the distance along any non-conducting surface between the HV and LV conductors.

Especially when the surface is wet or dirty, you can draw an arc farther along a surface than you can through the air, so the creepage distance specification for good isolation will typically be larger than the clearance distance specification. The ripples, ridges and rings that you see in HV insulators are meant to increase the creepage distance along the surface of the insulator.

 

[Edgardo]

Thank you all, your answers were helpful.