haman stray voltage

7/28/2019 Haman Stray Voltage

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STAR Energy Services, LLC

Alexandria, Minnesota tel 320.762.1697 fax 320.762.1479 [email protected]

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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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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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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Field Connections

Transformer

Utility

Barn

Isolator


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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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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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Source: Stray Voltage Detection A Self-Help Guide, Wisconsin Farm Electric Council


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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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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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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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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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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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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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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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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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Why This Renewed Interest?


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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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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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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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Questions?

haman stray voltage

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