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Page 375

Table A-3

Comparison of Contamination Performance of Polymer versus Porcelain Housed Intermediate Class Arresters (Courtesy Hubbell Power Systems)

Partial Wetting Test

5 Hr. Slurry TestMaximum Currenr After Slurry Number

| MCOV (kV) |

Housing Material

Housing Leakage Distance (in)

Max. Current (mA crest)

Max. Disc. Temps. (°C)

5

10

15

20

57

Polymer

81

<1

<38

35

42

44

44

66

Porcelain

54

68

>163

84

Polymer

109

<1

<38

50

52

60

60

98

Porcelain

122.4

18

<82

143

160

175

185

Tested using the 5-hour uniform slurry test procedure. This test consists of applying a uniform coating of standard 400 ohm-cm slurry to the test arrester. Within 30 seconds, MCOV is applied for 15 minutes, during which time the surface leakage currents cause the surface to dry. Slurry applications are repeated for a total of 20 test cycles. After the 20th test cycle, MCOV is applied to the arrester for 30 to 60 minutes to demonstrate thermal stability. Surface leakage currents were measured at the end of the 5th, 10th, 15th and 20th test cycles.

| explode causing porcelain fragmentation in the process; the one-piece fiberglass insulator will not experience puncture. |

| The polymer suitable for high voltage application consists of these materials: |

| 1. Ethylene Propylene Monomer (EPM) |

| 2. Ethylene Propylene Diene Monomer (EPDM) |

| 3. Silicone Rubber (SR) |

| Both EPM and EPDM, jointly referred to as EP, are known for their inherent resistance to tracking and corrosion, and for their physical properties, SR offers good contamination performance and resistance to Ultra Violet (UV) sun rays. The result of combining these is a product that achieves the water repellent feature (hydrophobic) of silicone and the electromechanical advantages of EP rubber. |

| Different polymer materials may be combined to produce a polymer with special properties; for example, a silicone EPDM is highly resistant to industrial type pollution and ocean salt. |

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