Wednesday, February 19, 2014
Interesting statistics that may help tell the power restoration story. Santee Electric Cooperative has 5,517 miles of line spread over a 20,000 square miles coverage area of four counties. Because we are a RURAL Electric Cooperative, we only have about 7 members per mile of line.
This is a little information about how the restoration process goes. The damage repair challenge for power systems can vary widely by type of weather situation, type of damage caused, and the individual situation at the specific repair. This is a general example, for illustration purposes only, of a scenario of line repair in an ice storm.
Consider a situation where multiple spans are damaged. A span is a length of conductor wire between two poles.
1. The weight of ice on trees or the wire itself breaks the wire and/or poles.
2. The tension on the wire as it breaks may pull it the distance of two or more poles - the length of a football field for each span of wire between two poles - 300 feet.
3. The repair crew arrives. It may be a bucket truck or it may be lineworkers who are climbing the poles with gaffs (an apparatus worn on the lower leg).
4. If a pole or poles have been broken, simply removing the 400-pound broken pole, re-digging a hole, and setting a new pole can take as much as 45 minutes per pole.
5. The ice must be broken off the wire for the entire span being repaired.
6. The line workers must pull the broken wire back into place.
7. A new span of wire is put in place and connections between existing and new wire spans are made.
8. The wire is connected to the pole-top transformers.
9. The service wires (that go from pole to home or business) must be re-strung and connected.
10. The line must be re-energized by manually closing the circuit in the field (at the fuse, main line or substation).
This time-consuming and multi-part process can add up to many hours for only a few spans of wire. Then in a frustrating and not uncommon turn of events in an icing situation, another section of that same power line can later break because of the weight of ice on nearby lines or trees.
— From Santee Electric Cooperative
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