FAQ

What is the function of the black (RF) glaze?

A/ One of the problems in the field of manufacturing and use of insulators on which the greatest amount of resources has been invested, is the irregular behavior of the insulating parts with respect to the generation of noise signals that significantly affect communications, when operating at their normal service voltage. Research into the solution of this problem has been directed towards achieving glazes whose properties improve the electrical behavior of insulators. One such development is the semiconductor compression glaze (RF). The basic principle underlying the RF semiconductor glaze consists of standardizing the potential gradient, in order to avoid excessive concentrations, which would give rise to capacitive arcs generating noise at radio communication frequencies. In short, the aim is to improve distribution of the electric field in these areas by improving conductivity.

What types of defects and how many are allowed in the insulators?

R/ In line with the parameters defined in international technical standards such as IEC, we have the following definitions:

Surface appearance

Glazed and unglazed surfaces must meet the following properties:

– The glaze must be smooth, shiny and resistant. Surfaces must be free of cracks, scratches, wrinkles, bubbles, glaze inclusions or other defects detrimental to satisfactory operating performance. These defects are treated as simple glazing defects in the assessment of allowable defect sizes; glaze chipping at the edge to be polished as well as chamfered surfaces are not allowed.

– Presence of cement on the internal or external surfaces of the insulator is not allowed.

External surfaces: glaze inclusions must not protrude more than 2 mm from the surface.

Internal surfaces:

– No surface bulges or depressions are allowed;

. Small holes or tool marks up to 2 mm deep are allowed.

Glazing defects

Glazing defects include unglazed spots, chipped surfaces, glaze inclusions and holes.

Is there any product (spray) or resin on the market that can be applied to chipped porcelain insulators, ensuring that the insulation properties are preserved?

If there is a crack or fissure in the porcelain, the unit must be replaced, since the dielectric has been pierced. If the problem is a chipped surface on one of the bells or at the base of a bushing, the surface can be repaired with an epoxy resin:

100 parts ARALDIT GY 6010
22 parts hardener HY 956

Note 1. This chemical product is corrosive and can cause severe irritation to the skin and eyes.  It must be handled with caution. After handling the product wash your hands thoroughly.

Note 2. To add viscosity to the mix and make it more paste-like for easier application, alumina or powdered silica sand with an ASTM 270 sieve may be added.

Note 3. It is very important to clarify that the repair work done on the insulator is a temporary solution until replacement units are procured and installed since these repairs cannot be guaranteed in the long-term.

How is the insulator glaze color determined?

A/ Color is not a relevant factor for the electrical or mechanical performance of the insulators. Worldwide, the most commonly used colors are gray and brown, gray often being preferred because it has less visual impact and contrasts better with the blue color of the sky, so it is the color of preference in the specifications of many utility companies. ANSI standards, available only for gray, require compliance with Munsell notation 5BG7.0/0.4, with the following tolerances:

  1. a) Hue: ±12 (3G to 7B)
  2. b) Value: ±0.5
  3. c) Chroma: -0.2 to +0.6

Questions about radio-influence: Is there a standard RIV value for different voltage levels?

Each insulator design has a standard radio-influence value. Check out the various ANSI models in our catalogues. It prevents the insulator from generating noise at high frequencies that might affect telecommunications.  If the value is lower, it will generate less noise and there will therefore be less interference in telecommunications.

What is the recommended procedure for the final disposal of porcelain insulators?

Insulators removed from distribution or transmission lines can be used as landfills. They can also be ground or milled for use as fillers in refractory material, in mortars or as construction landfills, given the high stability characteristics in the porcelain. Note: In the case of insulators containing metal parts, the metal hardware must be separated. The porcelain can be used as described above and the hardware may be used as scrap metal in iron-melting processes.