Standards and Ratings Insulators

Standard Features

Voltage Ratings

- Polycast insulators consist of a solid mass of epoxy, usually with imbedded UNC threaded metallic inserts on standard bolt circles to permit attachment. All bolt hole patterns consisting of three or more inserts have these inserts tied (common), to allow selective use, without floating those not used.
- Creepage distances are maximized by the addition of skirting (petticoats). Loss of skirts, or damage to the skirts, will not affect the mechanical strength of the insulator, nor can such damage lead to further deterioration of the insulator.
- PII20A, PII30A and PII40A insulators have the same strength when mounted upright or inverted, obliquely or horizontally.

- During the past twenty-five years, Polycast has designed, and now manufactures, a wide range of electrical insulators to meet North American and International standards. We have welcomed the opportunity to engage in the development of new insulating devices for special applications, and new designs have been carefully type tested according to the appropriate standards.

Type testing is done to confirm the adequacy of our designs for specified conditions, but because the conditions of use of any of our insulators is beyond our control, it is always the responsibility of the user to ensure that the insulator they select is suitable for their application.

Polycast
Voltage
Ratings

Nom.
Voltage
Class
kV

Low
Freq.
Dry
kV

Impulse
kV Crest
1.2x 50us

0.6

1.2

2.5

5.0

8.7

15.0

15.5

110

18.0

125

25.0

150

170

34.5

200

46.0

105

250

Polycast has designed and manufactures a variety of insulators for switchgear and other power applications to meet North American and International Standards. Mechanical type testing includes tension, cantilever (deflection), torsion, and compression. Thermal type testing includes thermal withstand and thermal cycling. Electrical type testing includes
lightning impulse withstand, power frequency withstand, power frequency flash-over and partial discharge testing.

The mechanical withstand values stated in our literature are 80-90% of ultimate test values. Working loads up to 50% of these stated values are considered safe for all insert options, but maximum loading will vary with the application and the conditions under which the insulator will be used.

Indoor Insulators: Ambient -55C to +55C
Outdoor Insulators: Ambient -55C to +55C
These ambient temperatures are considered safe for all insulator applications. The various epoxy systems used by Polycast in insulator design have continuous operating capabilities ranging from 120C to 180C, and all of these systems are capable of even higher temperature withstands on an intermittent basis.
Please consult catalog pages for recommended maximum continuous operating temperatures, or contact Polycast for any special requirements.

Indoor insulators are manufactured using an EC-A (Bis-A) epoxy material. EC-A epoxy is satisfactory for most indoor applications where UV, heavy pollution, or condensation are not factors.
Outdoor insulators are manufactured from EC-O (cycloaliphatic epoxy). Cycloaliphatic epoxy has superior arc track resistance and excellent weathering and UV resistance.
Metallic inserts are usually zinc plated steel, but brass or aluminum are standard on some insulators and
are optional on most designs. Standard inserts are UNC, but metric options are available.