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TABLE 14-1 (cont.) Troubleshooting Protective Relays

Condition

Possible Cause

Suggested Remedy

Poor contacts

| Realign contacts. Clean and dress them or replace if necessary. Tighten connections. |

Improper contact motion

| Check restraining spring tensions; adjust or replace. Check dashpot or bellows relief vent. Clean and adjust. Replace oil in dashpot if necessary. |

| Auxiliary relays not functioning |

Poor contacts

| Check and adjust contacts; clean and dress. Replace if necessary. |

Open circuit

| Check connections; tighten. If wire is broken, repair or replace. |

Coil not operating

| Wrong coil; voltage too low; insufficient current supply. Open coil or shorted turns; replace coil. |

Failure to release

| Armature out of adjustment; low voltage or current; wrong coil; replace. |

Relay coils overheated

Overload
Shorted turns in coil

Wrong coil; replace.

| Check cause; repair or replace if necessary |

Contacts overheated

| Corroded, pitted, or burned contacts Insufficient pressure |

| Clean and dress; replace if necessary. |

| Check spring tension; check contact alignment; adjust. |

Noisy relay

Loose connection

| Armature or plunger mechanism binding or dragging |

Tighten connection.
Realign or replace if necessary.

| Review. |

| 1. Protective relays must coordinate with other protective devices such as fuses, reclosers, lightning or surge arresters. As a practical matter, coordination generally involves a series of approximation and compromises. |

| 2. Electric systems can be adequately protected by dividing them into protective zones (Fig. 14-5), and subdividing them further as desired. The zones may comprise: sources of generation and their outlet circuits; subsources, substations; local or distribution circuitscoordinated in reverse order. |

| 3. Distribution circuits are most often radial circuits, supplied from only |

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