page_233

< previous page | page_233 | next page >

Page 233

TABLE 12-2 Troubleshooting Lightning or Surge Arresters

Trouble

Cause

Suggested remedy

Flashover of porcelain

Dirty or polluted surfaces

| Insufficient line to ground or to line clearances |

| Unusual severity of discharge; incorrect arrester rating |

Clean or replace if necessary

| Replace with unit having greater clearances |

| Replace arrester with one having correct rating |

| Lightning damage to protected equipment |

| Arrester rating too high for circuit voltage |

| Improper arrester location or connections; poor ground |

| Equipment insulation of inadequate impulse strength Air gap set too wide |

| Replace arrester with one having correct rating |

| Install arrester closer to equipment and obtain a reliable low-resistance ground. Inter-connect all equipment, arresters, lines, cable sheaths, structures, etc., and grounds. Use shorter ground connections. |

| Make sure equipment has minimum standard insulation level |

| Adjust gap according to specifications |

| Arcing or corona discharge from gap assembly; too frequent sparkovers |

| Loose or broken connection Incorrect gap setting |

Tighten or repair connections

| Set gap according to specifications |

| Excessive operating temperature; discoloration of metal parts |

| Excessive ambient temperature |

| High internal losses; incorrect arrester rating Loose connections |

Relocate to better location

| Replace arrester with one having correct rating Tighten or repair connections |

| these elements be coordinated for their proper operation and protection. Coordination of this kind will be discussed in connection with relays. |

| For causes and remedies when troubleshooting lightning or surge arresters, see Table 12-2. |

| Review |

| 1. Lightning or surge arresters serve the same purpose on an electric circuit or line as a safety valve on a boiler. When a voltage surge induced by a nearby lightning stroke, or caused by switching, reaches an arrester, it finds a lower resistance path to ground than that presented by the equip- |

< previous page | page_233 | next page >