Power plants generate power from hydroelectric, geothermal, natural gas or nuclear power and boosted up to transformers to transport electricity over long distances. The power then goes in to industry where they utilize high voltage in their operations. Distribution substations reduce the voltage down so they can be utilized by residential and commercial customers. Usually this is 120 KV or 480 KV.
When you look at a power pole you may see varying levels of lines on the pole. The top line is generally the transmission line carrying a higher KV. This line is utilized to carry electricity further distances. The lower lines are primary and secondary lines that will be lower voltage carrying electricity to individual homes or subdivisions. The lowest lines are often black coated and are telephone or cable.
Resistance = Something is on the line or within the line, hardware problems or a line down is stopping the flow of electricity. Remember electricity flows like water. Fault = This can be caused by equipment malfunction and trigger a stop in the flow of electricity Arcing = Can result from equipment failure. Electricity goes to ground or vegetation is to close. Overload = Too much demand on the line and trips a fuse that can cause fire.
This is a universal fuse. It has the capability of starting fire. Note that hot material can be expelled if it is tripped. This is why clearance around poles should be done if this fuse is used in wildland area.
This is another type of fuse called an open link fuse. It can drop molten material if tripped. This fuse is not used in Southern Ca. In Northern CA we see it but pole clearance is required. It is a cheap fuse a lot of companies choose to use.
Here’s an example of the fuse blowing
This has been tested and proven not to have the potential to start fires.
These have potential to cause fires. Clearance around poles should be done in wildland areas. In CA any pole with this on it is required to have a 10’ clearance.
And a fuse can blow
These clamps have the potential to start fire. There are 2 types. The bad design can unscrew under vibration and have the potential to arc. The spring loaded stays in place on the line. Some smaller utility companies may be using the lower type of clamps because they don’t want to spend the $ to swap out to the newer design.
These connectors can come loose and have potential to arc. Clearance required in CA.
Lines that are overloaded by too many people taping the system (may see this during hot periods, folks cranking up their electricity) Line tension problems, lines with LONG spans Heating can cause lines to sag or swag. This can cause vibrations at the pole and hardware can get loosened up. Changes in elevation can cause tension on the line and stress at the pole with connectors and bolts.
Failures can occur iuf there are splices in the line, heat arcing or contact with trees.
Here is a “burner” a tree on the line. The sap conducts heat and will start to ignite.
Insulators can arc or flashover. Salt build up dust, dew can all contribute to arcing that can result in a fire, causing a hot piece of metal or meltage that drops to the ground under the line.
Here’s an example of arcing. Note the black section of line. A hot piece of metal can drop off the line. Fire investigators will look for the soot on the line.
They can become a conductor of electricity causing a fault. They can catch fire and drop to the ground.
Transformers transform line voltage in to useable electricity. This is not a fire starter, however, often lightning arresters are place on transformers.
Service interruption can be a cause of fires. Investigators will take the type of interruption in to account for investigation.
Here's an example of pole clearance
P 101 ep 3-f
Lesson Objectives• Identify the basic components of the utility power distribution system.• Identify how powerlines can cause wildfires.• List mitigation measures to prevent powerline related fire causes. 3F-02-P101-EP
Introduction• Powerlines can pose a threat to ignition of wildfire in various fuel conditions.• Fires of this cause are generally large and damaging. 3F-03-P101-EP
• Generally start during dry windy periods.• High winds blow trees across power lines. 3F-04-P101-EP
• Some states have passed laws requiring fire safe precautions for powerlines.• Fire protection agencies can work closely with utilities to minimize customer and public safety. 3F-05-P101-EP
Discussion Items with UtilityCompany• Focus on high hazard, high risk areas• Maintenance schedule• Attention to high stress poles• Conductor (powerline) inspection 3F-35-P101-EP
Summary and Review Lesson Objectives• Identify the basic components of the utility power distribution system.• Identify how powerlines can cause wildfires.• List mitigation measures to prevent powerline related fire causes. 3F-36-P101-EP