Q: What is a Distribution Substation?
A: A Distribution Substation is a facility within the distribution system, and is a critical part of the Electrical Power System that includes generation, transmission, and distribution. Distribution substations transform voltage generally from high to low, so that it can be distributed down either overhead or underground power lines before being delivered to the customer. A substation includes transformers, control equipment for switching and system protection to transfer power to distribution lines.
Q: How does a substation benefit me?
A: A new substation means that you will be assured of continued power quality and reliability as your area continues to grow and the demand for electricity increases. Overloaded substations and power lines have a higher frequency of failure, and under peak conditions, power quality issues such as blinks and brown-outs can occur.
Q: Why would the PUD consider a location in a residential/neighborhood area?
A: It is necessary to locate substations at or near the electrical demand. The substation will be located in the demand area whether it is serving residential, commercial or industrial. Substations convert the power system voltage from transmission levels to distribution levels so that it can be safely and efficiently delivered down our streets. If distance thresholds are exceeded low voltage levels will result.
The PUD currently has nine substations in the Wenatchee and Cashmere area that are immediately adjacent to residential neighborhoods. The PUD also has four substations in the Chelan area that are within 1,000 feet of residences. (Please see Wenatchee residential locations map)
Q: How does the PUD decide when and where to locate a substation site?
A: There are numerous factors that go into the PUD making a decision on when and where to locate a new substation. Selection criteria include:
- Forecasted load
- Ensuring that existing stations do not exceed 100 percent of rated capability
- Planning for new substations before an existing substation reaches 80 percent capacity
- Meeting expected growth that is forecast based on county construction estimates
- System requirements
- Location in proximity to existing transmission lines
- Location in relation to existing load and load growth – the substation must be reasonably central to the distribution area to be served
- Meet National Electric Safety code standards for supply stations
- Land purchase price
- Land availability
- Land parcel size – adequate for equipment
- Slope requirements of flat terrain
- Groundwater issues
- Conditional Use Permit – governed and issued by the City or County depending on location of site
- Environmental permitting considerations
- Disturbance of greater than 1 acre
- Historical significance
- Flood Zone
- Site must have access for mobile substation in an outage and allow for regular maintenance
- Security of location
- Aesthetics/public perception
- Required easements
Q: What type and size of substation does the PUD build?
A: Most new substations will be 28 MVA (or 28 million watts) substations. The PUD generally needs a minimum of one acre of flat land for a substation. This one acre includes a set back and the fencing that surrounds the actual substation equipment. The substation itself has about a half-acre footprint.
Q: Is there audible sound from a substation?
A: The main noise heard from a substation is a hum coming from the transformer. This hum is the same type of hum, only greater as the transformer is bigger, to other transformers or streetlights, found on most street corners. Modern substation transformers are quieter than transformers built just a few years ago – often 10 decibels (dB) quieter for an equivalent transformer due to recent advances. Chelan PUD purchases new transformers that meet this lower sound level. A typical new substation transformer will produce approximately 65 dB of noise measured at 2.0 meters from the transformer. This is about the loudness of a newer standard residential outdoor air conditioning unit. The sound level diminishes the further away from the sound producing source. At the substation perimeter fence the sound level has dissipated to lower levels.
Q: What type of mitigation can a neighborhood expect to help improve the aesthetics of a substation?
A: When planning the construction of a substation, PUD staff will work with the community to discuss design and landscaping alternatives. These include:
- Reduced sound design to national standards
- Fencing enhancements
- Managed profile
- LED lights to reduce light pollution
- Other possible design elements that may be identified
Q: Why doesn't the PUD build underground Transmission?
A: There are two reasons Chelan PUD has not chosen to build underground transmission - higher costs and the complexity of the engineering and maintenance. In addition to high initial construction costs compared to above ground transmission, it also would require Chelan PUD to create a new division internally, to hire additional engineering staff and trained maintenance crews, and to stock spare parts and other assets to maintain a limited amount of underground transmission. Creating this business unit in the timeframe to construct needed substations and transmission lines in the near term is not feasible at this time.
Q: What are the health risks of living near a substation?
A: Electromagnetic fields (EMF) are the invisible fields that surround all electrical equipment and power lines. Electric fields exist everywhere we live or work. Any electric line or appliance emits both electric and magnetic fields, which combined create EMFs. All things electrical, from your toaster to high voltage power lines, are surrounded by EMFs. These fields drop off rapidly with distance from the source.
There are conflicting research results on whether EMFs affect human health. Hundreds of scientific studies have been carried out around the world over the last thirty years to answer the question, “Can exposure to EMF have harmful health effects?”. These studies have used a variety of approaches to explore the potential health effects of EMF. Scientific evidence does not support a cause-and-effect relationship between EMF exposure and health risks.
People get most of their EMF exposure from electrical wires along the street and from wiring in their homes. People also get short-duration higher field exposures when they pass close to electrical appliances (see table below). Outside the home, people can experience EMFs from cell phones, in schools, industrial warehouses, offices, electric vehicles, etc.
From the electricity system, high-voltage power lines produce higher fields than substations. As a whole, not many people live within 100 yards of a high-voltage power line. More people live close to a substation of one sort or another, but even if you live very close, the level of exposure is minimal.
A Gauss meter measures the EMF levels of electronic devices and equipment. The Gauss meter measures in units called milligauss, abbreviated mG. A gauss is technically a “unit of magnetic flux density”.
|Table 1: Typical values of magnetic fields measured at normal user distance
||Range of measurements (mG)*
| Electric stove
| Personal computer
| Electric blanket
| Hair dryer
| Pedestal fan
| Table 2: Typical values of magnetic fields measured near power lines and substations
|| Location of measurement
|| Range of measurements (mG)*
| Distribution line
|| directly underneath
| Distribution line
|| 10 meters away
|| at substation fence
| Transmission line
|| directly underneath
| Transmission line
|| at edge of property easement
*Note: Levels of magnetic fields may vary from the range of measurements shown
**Table source: https://www.arpansa.gov.au/understanding-radiation/radiation-sources/more-radiation-sources/measuring-magnetic-fields
EMF and Your Health – Electric Power Research Institute, January 2012
Q: What are the potential environmental concerns at a substation and how are they addressed by the PUD?
A: The primary materials in substations are metals. The power transformer is filled with non-toxic and non-hazardous mineral oil that is used for cooling and electrical insulating. In an event of a leak, the station has a designed secondary containment to prevent the oil from leaving the station. The high voltage circuit breaker or circuit switcher does contain three hermetically sealed bottles of sulfur hexafluoride (SF6) gas which is a greenhouse gas.
Q: What type of equipment and chemicals are used inside the substation?
A: A typical substation contains equipment including transformers, circuit breakers, protective relays and associated controls, a control building, steel supporting braces and batteries. The battery bank includes eight batteries which are similar to a vehicle battery. These batteries are contained inside the substation control building.
Another type of equipment is the circuit breakers that protect the individual feeder lines leaving the substation to serve homes and businesses. There are typically four of these circuit breakers that are located inside the substation control building. Each of these circuit breakers is about the size of a kitchen oven. These circuit breakers do not have SF6 gas like higher voltage circuit breakers but rather utilize vacuum bottles about the size of a coffee can.
A combination switch/circuit breaker, generally called a circuit switcher, is used on the higher transmission voltage. This circuit switcher has three separate hermetically sealed bottles that contain some amount of SF6 (sulfur hexafluoride) gas used as an electrical insulator. Chelan PUD does not perform regular maintenance on these bottles but does inspect them monthly. If they are found to be in need of maintenance, they are replaced.
Q: What assurance does the public have that the PUD protects the public from potentially dangerous or hazardous materials at substations?
A: Electric power substations are required to meet various government regulations and industry standards. There are many standards for the various types of equipment, maintenance, and operation of a substation. Standards include OSHA, IEEE, ASTM, ANSI, IEC, NEMA, NFPA, ICEA, NESC, and others. Chelan PUD uses the applicable standards for each item inside a substation as required.
Q: Can drinking water from a well be contaminated by a nearby substation?
A: No, the only thing of a substantial quantity to penetrate the soil in a typical distribution substation is an insulating light mineral oil. This oil meets OSHA 29, CFR 1910, ASTM D117, and ASTM D 877 standards. The insulating oil is contained inside the transformer. This is the same oil that is inside the common smaller distribution transformers found in close proximity to homes and businesses.
Under Federal law, substations are required to have a Spill Prevention and Counter Measures plan to ensure oil is all contained within the station. Chelan PUD’s standard is a water-tight mote around the transformer to contain any oil.
Q: What type of maintenance is performed inside the substation and on what schedule?
A: Monthly inspection is scheduled at each of the PUD’s substations and takes place during working hours where a single person will inspect the station taking about one hour. Yearly maintenance takes place during working works and can last from one day to two weeks. Major maintenance is scheduled on an eight-year rotation and typically takes place during working hours. This maintenance can last up to two months. Rarely is this maintenance work done at night, outside working hours.
The substation nor the equipment inside the station requires waste to be removed or treated. The portable restroom facilities located at each substation for the use of PUD staff and contractors requires regular maintenance.
Q: How long does it take to construct a substation and what type of equipment is used?
A: For the type of substation needed in the north shore area, construction is expected to last about six months. This is from the time the first piece of machinery shows up on the site to the time the construction is complete. Constructing during this time includes excavation, digging, fencing, placing equipment, etc. Equipment being used during this time includes excavator, crane, cement truck, and flat bed trailer carrying substation equipment. The equipment to be installed including the power transformer and circuit breakers are specialized equipment. Because they are specialized the delivery time is 12 to 18 months.
Q: From the time construction is finished how long until the substation is energized?
A: Testing and commissioning of the substation equipment lasts for about two months after construction is complete. Then, the transformer is energized and ready to serve customer load. Some small PUD trucks may be seen driving to and from the site during this time.
Q: How and when can residents and property owners provide public comment on the siting of the new substation?
A: The PUD is always open to hear public comment. Please visit the Substations page for more information about current projects and how to provide comment.
The PUD is also required to follow the Conditional Use Permitting (CUP) process when property is acquired for building a new substation. Depending on where the final determination is made for each of the substations, the PUD will work with either Chelan County Planning Department or the municipal planning departments in the appropriate area. If a site is located within the Urban Growth Area, but outside city limits, Chelan County will follow municipal requirements. For example, in Chelan, the current potential sites both lie outside the city limits and the Urban Growth Boundary so the CUP will be handled by Chelan County Planning.
As part of the CUP process, Chelan County Planning will notify property owners in writing within a 300-360 foot radius (depending on any roads) of the potential substation site. A public comment period is then opened for 14 days and comments are made directly to Chelan County through the channels defined in the written notification. An examiner’s hearing is then held where property owners still have an opportunity to provide public comment. After the hearing, a final decision is made which can be appealed to Chelan County.
For more information on the CUP process, please visit the links below:
Chelan County – Information materials for a Conditional Use Application
City of Chelan – Conditional Use Permit
City of Leavenworth – Conditional Use Permit Application