Post on 03-Apr-2018
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7/28/2019 Haman Stray Voltage
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7/28/2019 Haman Stray Voltage
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STAR Energy Services, LLC
Alexandria, Minnesota tel 320.762.1697 fax 320.762.1479 alhaman@star-energy.com
Terminology
0Primary Neutral-to-Earth Voltage (PNEV)
0Voltage measured between the utility primary neutraland an earth reference point which is generally a ground
rod placed specifically for this purpose
0Secondary Neutral-to-Earth Voltage (SNEV)
0Voltage measured between the farms secondary neutraland an earth reference point which is generally a ground
rod placed specifically for this purpose.
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STAR Energy Services, LLC
Alexandria, Minnesota tel 320.762.1697 fax 320.762.1479 alhaman@star-energy.com
Terms
0Stray Voltage0Difference in voltage measured between two surfaces
that may be contacted simultaneously by an animal*
[cow contact areas]
0Isolation0Separation of the primary neutral from the secondary
neutral through the use of an approved isolation device
0Isolation Device
0Piece of equipment which is accepted by the NationalElectrical Safety Code for purpose of isolation
*Effects of Electrical Voltage/Current on Farm Animals: How to Detect and Remedy Problems;
US Department of Agriculture, Beltsville, MD; December 1991; Page 9-4
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STAR Energy Services, LLC
Alexandria, Minnesota tel 320.762.1697 fax 320.762.1479 alhaman@star-energy.com
Neutral-to-Earth or
Stray Voltage?0PNEV is measured at the transformer location orother spots off farm
0SNEV is measured at spots within the secondary
system on the farm0Could be utility-owned or consumer-owned
0Could fall under NESC or NEC jurisdiction
0On properly installed and maintained secondary
systems without isolation, PNEV and SNEV are nearlyequal
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STAR Energy Services, LLC
Alexandria, Minnesota tel 320.762.1697 fax 320.762.1479 alhaman@star-energy.com
Field Connections
Transformer
Utility
Barn
Isolator
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STAR Energy Services, LLC
Alexandria, Minnesota tel 320.762.1697 fax 320.762.1479 alhaman@star-energy.com
Neutral-to-Earth or
Stray Voltage?0Properly installed and maintained isolation devices
separate PNEV and SNEV at the transformer
location during low (less than 10 volts) voltage levels
0Is SNEV present in cow-contact areas?
0Measurements should be made to determine voltagelevels in cow contact areas
0Initial inspection0Chart recordings taken over a several-hour period
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STAR Energy Services, LLC
Alexandria, Minnesota tel 320.762.1697 fax 320.762.1479 alhaman@star-energy.com
Stray Voltage
0All animals are affected by current flow, not voltage.However, current flow has historically been difficult to
measure, which is why voltage has become the
standard.
0Stray voltage (as defined by USDA) will exist on allfarms. The investigator must properly measure the
magnitude and interpret results.
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STAR Energy Services, LLC
Alexandria, Minnesota tel 320.762.1697 fax 320.762.1479 alhaman@star-energy.com
Source: Stray Voltage Detection A Self-Help Guide, Wisconsin Farm Electric Council
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STAR Energy Services, LLC
Alexandria, Minnesota tel 320.762.1697 fax 320.762.1479 alhaman@star-energy.com
How Do We Determine Conditions?
0Todays one and only equation:
0Voltage = Current x Impedance
0Impedance is a complex variable which is dependentupon frequency of the power source R+jX
0Studies have shown impedance of a dairy cow canbe reduced to the resistance component of the
complex variable
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STAR Energy Services, LLC
Alexandria, Minnesota tel 320.762.1697 fax 320.762.1479 alhaman@star-energy.com
University Studies
and Field Trials0University studies yield typical cow resistance for various
situations STAR chooses 500 as level of interest
0University studies yield typical cow behaviors for varyinglevels of current passed through the body STAR chooses
1 mA as level of interest
0V=500x 1 mAV=0.5 V
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STAR Energy Services, LLC
Alexandria, Minnesota tel 320.762.1697 fax 320.762.1479 alhaman@star-energy.com
Looking for Voltage
0Cow resistance published through research
0Behavioral response to current flow publishedthrough research
0Voltage is the variable quantity and must beinvestigated at each farm and its cow contact areas
0Many unique characteristics of the farm and myriad ofvariables can make this challenging
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STAR Energy Services, LLC
Alexandria, Minnesota tel 320.762.1697 fax 320.762.1479 alhaman@star-energy.com
Cow Reaction to 60 Hz
Electrical Current0Primary impact of stray voltage/currents on milk
production involves changes in behavior1 [dairy cows]
0Electrical current cannot directly cause infections2
[mastitis]
0Numerous causes of behavioral changes andphysiological changes in animals3
Effects of Electrical Voltage/Current on Farm Animals: How to Detect and Remedy Problems;
US Department of Agriculture, Beltsville, MD; December 1991:1Page 1-42Page 3-23Page 3-2
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STAR Energy Services, LLC
Alexandria, Minnesota tel 320.762.1697 fax 320.762.1479 alhaman@star-energy.com
Steps to Successful Stray
Voltage Investigation0Have a plan and follow it0Build trust with the farmer
0Investigator should interview the farmer and note
behavioral characteristics of the animals, managementpractices, electrical incidents and other items of interest
0Initial inspection using a digital multi-meter, measurePNEV, SNEV, and cow contact areas with the farmer
present0Examine farm wiring for NEC compliance
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STAR Energy Services, LLC
Alexandria, Minnesota tel 320.762.1697 fax 320.762.1479 alhaman@star-energy.com
Overnight Recording
0Test Setup
0PNEV and SNEV
0Cow contact areas selected by the investigator basedupon experience and the farmer interview
0This recording period may be more than one day inlength
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STAR Energy Services, LLC
Alexandria, Minnesota tel 320.762.1697 fax 320.762.1479 alhaman@star-energy.com
Off-Farm Items
0Primary neutral has a high resistance
0Poor neutral connectors, specifically bolted connectors
0Poor neutral grounding in immediate area, need moreand deeper ground rods
0Underground cable with bare concentric neutral
0Primary neutral return current is high
0Load balancing on three-phase circuits
0Undersized neutral conductor; on a typical system,about 1/3 of return current flows on the neutralconductor
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STAR Energy Services, LLC
Alexandria, Minnesota tel 320.762.1697 fax 320.762.1479 alhaman@star-energy.com
Other Things
0Items of concern on neighboring secondary servicescan cause hard to find NEV conditions
0The isolation device is bypassed by another utility0The isolation device is defective
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STAR Energy Services, LLC
Alexandria, Minnesota tel 320.762.1697 fax 320.762.1479 alhaman@star-energy.com
Why This Renewed Interest?
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STAR Energy Services, LLC
Alexandria, Minnesota tel 320.762.1697 fax 320.762.1479 alhaman@star-energy.com
Items to Remember
0Build trust with the farmer
0Stray voltage, as defined by USDA, will be found on the
farm0Stray voltage research is voluminous
0Use NESC and NEC experts to investigate andinterpret measurements
0Implement recommendations of the experts
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STAR Energy Services, LLC
Alexandria, Minnesota tel 320.762.1697 fax 320.762.1479 alhaman@star-energy.com
Items for Communicators
0Use consistent terms
0Publish notices regularly in cooperative newsletters
0Treat all member inquiries carefully
0Respond to inquiries in a timely fashion0Designate one person to handle inquiries
0Have a plan and follow it
0Understand and respect this is a scientificphenomenon, therefore quite complex
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STAR Energy Services, LLC
Alexandria, Minnesota tel 320.762.1697 fax 320.762.1479 alhaman@star-energy.com
Key Points for a Good Plan0Designate a single point of contact
0Receptionist should be familiar with keys of a strayvoltage inquiry
0Single point of contact must return call in timelyfashion
0Follow a prepared procedure once in the field
0Get the results back to the farmer in a timely fashion
0Make reasonable accommodations0FOLLOW THE RECOMMENDATIONS!!!!
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STAR Energy Services, LLC
Alexandria, Minnesota tel 320.762.1697 fax 320.762.1479 alhaman@star-energy.com
Questions?