Stray Voltage Detection

A Self-Help Guide From…

Midwest Rural Energy Council Table of Contents 2

Introduction ...... 3

What is Stray Voltage...... 4

Types of Voltage Sources...... 4

Causes of Stray Voltage...... 4

Stray Voltage Detection ...... 5

Making Electrical Measurements...... 6

Recording Voltage Data...... 7

Interpreting Voltage Data...... 7

Monitoring Stray Voltage...... 8

Farm Wiring Checklist...... 9

Data Collection Form...... 10

Mission Statement...... 11 Introduction 3

his publication is intended to give you a basic understanding of stray voltage, some of its common Tsources, how to determine if it exists on your farm at levels that may be harmful, and when to call for assistance to help reduce stray voltage levels. This document is not intended to make you a stray voltage expert, but should provide you with the information necessary to safely determine if a problematic level of stray voltage is present on your farm at locations that are accessible to your livestock.

This booklet is specifically oriented toward the dairy farmer; however, most of the information provided is applicable to all livestock operations. The Farm Wiring Checklist, located on page 9, is included to assist you in visually inspecting your farm’s electrical system and noting potential stray voltage sources. A Data Collection Form is included on page 10 to help you record milkhouse and livestock area voltage measurements. In addition, this publication will suggest methods for monitoring stray voltage levels on your farm—a practice that is strongly recommended for all livestock operations. What is Stray Voltage? 4

WHAT IS STRAY VOLTAGE? the watering device and the adjacent necting metal objects) and - ow levels of AC (Alternating floor. It is important to note, howev- ing. It is recommended that you Current) voltage between er, that these same symptoms, as well identify the source of the voltage and Lgrounded conductors and as a number of other behaviors and continue to take voltage measure- conductive surfaces of a livestock health concerns can be the result of ments after improving bonding and confinement facility are a normal and numerous other non-electrical farm grounding. Continuing measurements unavoidable consequence of deliver- factors. will confirm that the changes made ing and using electricity. These volt- have successfully reduced the voltage ages are termed “stray voltage” when As a farm manager, you should inves- that animals may experience to an they can be measured between two tigate all possibilities, including stray acceptable level, and will also help objects that may be simultaneously voltage, when attempting to resolve to ensure continuing farm electrical contacted by animals. Occasionally, a behavioral, production, or health safety. stray voltage levels are significant problem. enough to be felt by you as a “tin- Symptoms present, but no tingle gling” sensation. This publication sensation is felt concentrates exclusively on measur- TYPES OF SOURCES Livestock may feel voltages not ing and minimizing AC voltages. t is important to make a distinc- sensed by humans because an ani- Small levels of DC () tion between low-level stray mal’s exposure conditions are differ- voltage from naturally occurring Ivoltage which is a normal and ent than that of a human. Animal sources (galvanic action of metals in unavoidable consequence of using contact voltage measurements should contact with the soil) is also present electricity, and the more hazardous be taken if livestock exhibit avoidance on farms, but these small DC voltages voltages related to electrical faults. behaviors. This publication will help pose no risk to farm animals. you make your own voltage measure- Personal Shock ments to determine the level of stray REPORTED SYMPTOMS If you experience a painful shock voltage on your farm, and whether wide variety of symptoms when you touch a metal object in corrective action might be required. have been attributed to stray the barn, it is likely that there is a If you are unsure how to take these Avoltage, although relatively severe fault in your electrical system. measurements, you can ask for as- few of these have been confirmed Your animals may also be exposed to sistance from your electric service in controlled studies. The effects of excessive voltage levels, depending supplier. excessive stray voltage exposure on on the location of the fault. These farm animals are all “behaviorally conditions are hazardous and could CAUSES OF STRAY mediated.” In other words, animals result in serious personal injury or VOLTAGE show avoidance behaviors in areas start a fire. Call an or your ome level of stray voltage will where contact with excessive voltage electric service provider if you receive always be present, even on a is perceived as annoying or painful. an electrical shock on your farm. Sproperly wired farm. Voltage is This may appear as reluctance to developed on the grounded neutral cross building thresholds where a Tingle Sensation system as the result of load current significant ‘step’ potential (voltage If you feel low-voltage “tingling” flowing through the resistance of the between front to rear hooves of a when you touch equipment in the grounded-neutral network. This volt- cow) may be present; or reluctance barn, it is possible that your live- age is typically made up of several to drink at watering devices at which stock may be experiencing a similar voltage sources acting simultaneous- a significant ‘touch’ potential (volt- sensation. Tingle from metal objects ly. Both on-farm and off-farm sources age between the watering device and frequently can be eliminated through may contribute to the level of stray the floor) may be present between better bonding (electrically intercon- voltage present. Stray Voltage Detection 5

A common on-farm source of stray Off-farm voltage sources may also be a voltmeter to measure the voltage voltage is the inappropriate intercon- present on your farm. If requested, between two points that may be nection of equipment grounding con- your electric service provider will simultaneously contacted by livestock. ductors with the neutral conductors of conduct an investigation (usu- the farm wiring system. The ground- ally at no charge) using controlled, CAUTION: For your own safety, ing conductor is intended to ground standardized test procedures to do not attempt to make electrical metal equipment and should never be determine to what extent electri- measurements on one of the conductors used to supply cal distribution facilities or other or within electrical boxes or power. The neutral, or other conduc- off-farm sources contribute to stray cabinets unless qualified to do so. tors supplying power, should never voltage levels. If an abnormal volt- be connected to the metal case of age from the distribution system is SUITABLE VOLTMETER equipment or be interconnected with found, your electric service provider Many of the voltmeters in use today the grounding conductor at any point will take action to help reduce the can give you misleading readings other than the main electric service level of stray voltage on your farm. because of the manner in which they panel for the building. are constructed and the voltage levels STRAY VOLTAGE they are intended to measure. A suit- Other on-farm contributors to stray DETECTION able voltmeter must not be affected voltage levels include: ou can detect the presence by DC voltage when operating on • Unbalanced 120-volt loads (includ- of stray voltage on your farm the AC scale. The meter should also ing loads in the house and other Ysafely and easily by using “screen out” low level voltage sources buildings) that increase current on neutral conductors • Corroded or loose electrical con- nections anywhere on the neutral conductor • Missing or inadequate grounding systems • The normal operation of large elec- trical equipment (such as welders, motors, pumps and conveyors) in remote areas of the barn or other Wire buildings Double Nuts Banana The degree to which these sources Plug Banana contribute to stray voltage levels Plugs depends upon many factors including the layout of the farm wiring system 500-Ohm Resistor 500-Ohm Resistor and relative strength of the source. A Figure 1: Figure 2: visual inspection checklist of poten- Digital Voltmeter with 500-ohm, Analog Voltmeter with 500-ohm, tial on-farm problems (Stray Voltage two-watt, Flameproof Resistor two-watt, Flameproof Resistor Checklist, page 9) is included at the Note: the resistor should be removed from the meter before making any end of this publication. Correction measurements other than stray voltage (cow-contact measurements). of on-farm deficiencies will normally require the services of a qualified CAUTION: The shunt resistor is designed for use with very small voltages and MUST be removed from the meter before using the meter to measure the much electrician. larger voltages on energized conductors. Making Electrical Measurements 6

which are incapable of affecting your curately display voltages less than 1.0 point) method and the point-to-refer- livestock. A shunt resistor is used for Volt. A meter with a full-scale reading ence ground method. this purpose. of 2.5 Volts AC is ideal. A full-scale reading of 5.0 Volts AC is normally Animal contact measurement To accurately measure the stray acceptable. Any full-scale reading The animal contact method is a voltage that livestock may feel, a greater than 5.0 Volts AC is generally measurement of your animals’ voltage shunt resistor that approximates the not sensitive enough for stray voltage exposure. It allows you to determine resistance of a cow and its contact to measurements. the levels of voltage that the animals the surfaces it is touching should be may actually come into contact with. connected across the voltmeter leads. Your analog voltmeter must also be This is the most important measure- (Refer to Figures 1 and 2) A two-watt, capable of measuring only AC volt- ment and it simply means taking volt- flameproof resistor of approximately age. Some analog voltmeters do not age measurements between two points 500-ohms is recommended. This discriminate between DC and AC that can simultaneously be touched by type of resistor is available at most voltage and may provide you with livestock. electronic parts stores. You may misleading information. An analog use either a digital voltmeter or an voltmeter can be tested by setting The animal contact measurement will analog (needle-type) voltmeter to the meter on the AC scale and touch- usually be from metal equipment that measure stray voltage. However, you ing the leads to the ends of a 1.5 volt animals can access (such as drinking must understand the limitations of battery. The leads should then be cups or metallic feeders), to the floor. each in order to ensure accurate and reversed and the procedure repeated. Make sure you have a firm connec- meaningful measurements. If, in one of these two positions, the tion to a cleaned surface on metallic meter’s indicating needle initially contact points. Digital voltmeter “jumps” and then settles to a steady The digital voltmeter has a digital reading of 0.0 volts, the meter is ac- The meter lead in contact with the display and is the preferred method ceptable. An analog voltmeter with floor must be in a wet location with of monitoring stray voltage. A digital a full-scale reading of 5 volts or less good contact pressure to ensure voltmeter with a 500-ohm shunt resis- and a 500-ohm shunt resistor will electrical contact. Attaching the lead tor is easy to read and accurate when give you an accurate measurement of to a copper plate placed under pres- measuring small voltages. A digital the stray voltage that your livestock sure on the wet concrete floor is the voltmeter without a shunt resistor, may perceive. recommended method. However, other however, has an extremely high input alternatives such as standing on the resistance (several million ohms). This MAKING ELECTRICAL voltmeter probe or clamp may work high input resistance makes it very MEASUREMENTS satisfactorily for an approximate read- sensitive to extremely weak voltage ing. sources. Low-level voltage sources do CAUTION: For your own safety, not have the ability to affect your ani- The animal contact measurement mals. In order to accurately measure do not open or attempt to measure method, which uses a copper plate the voltage your livestock may feel, voltage inside electrical devices on the floor in the rear-hoof area you must use a shunt resistor to make or equipment or on any other and a 500-ohm shunt resistor across your digital voltmeter “look” like a electrical wiring unless qualified to the leads of a digital voltmeter, most cow in the electrical circuit being do so. accurately represents the actual measured (See Figure 1). exposure voltage for dairy cows. Only here are two basic measure- measurements of the exposure voltage Analog Voltmeter ment methods for diagnosing will allow you to determine if the stray If you use an analog voltmeter (one Tpotential stray voltage situa- voltage present can be harmful to your with a moving needle), it must have a tions: the animal contact (or point-to- livestock. voltage scale sensitive enough to ac- Recording Voltage Data 7

Point-to-reference ground When you measure voltages on INTERPRETING VOLTAGE measurement outside equipment, such as feeders or DATA The point-to-reference ground method stock waterers, you may use a metal esearch regarding the levels of testing is not used to determine rod driven 12 to 18 inches into the of stray voltage that should exposure voltages. It is used to help ground approximately six feet from Rcause concern has taken place the investigator diagnose the sources the equipment being measured. This at several US universities and in at of stray voltage and involves the is an adequate method of determin- least five (5) other countries over the use of a remote ground probe as a ing if an unacceptable voltage is last 40 years. This extensive body reference. For reliable accuracy, the present on the device being checked. of research has shown that animal remote ground probe should consist A more thorough investigation may contact voltage levels below 2.0 of a metal stake or rod driven into be required to accurately measure Volts AC are not harmful to dairy moist soil and located at least 30 feet animal-contact (exposure) voltage cows. Many electric utilities have away from any electrical grounds, levels. taken a conservative approach and water pipes or grounded metal recommend a thorough stray voltage equipment. An insulated wire (no. RECORDING VOLTAGE DATA investigation whenever voltages of 18 is adequate) should then be used ormally, stray voltage should 1.0 Volt AC or greater are measured to connect the ground probe to the be measured during milking, across cow-contact points using the common terminal of the voltmeter. Nwhen the highest electrical animal contact measurement method The other voltmeter probe is used to loads are present and the highest described. Sheep and pigs have levels contact the metal objects within the stray voltage levels will occur. It is of sensitivity similar to dairy cows animal confinement area. The 500- recommended that you take volt- while poultry are much less sensitive ohm shunt resistor is not used. age measurements at several animal to voltage exposure. contact locations to determine where This method of measuring usually the voltage is greatest. Use the data TAKING ACTION results in higher voltage readings sheet at the end of this publication f animal contact voltage measure- than the animal contact method, but for recording voltage measurements. ments, taken during milking or the voltages measured are not mea- The date and time that measure- Iat any other time of day, do not surements of animal exposure. They ments were taken should also be exceed 1.0 Volt AC, research indicates are not measurements of exposure included. This information may serve that the voltage is too small to affect because an animal cannot simultane- as a future reference to detect any your livestock. An ample margin ously contact these two points and, significant changes in farm electrical of safety is built into this number. therefore, cannot be harmed by the system sources. Under these circumstances, it is measured voltage. recommended that you use a voltme- NOTE: Your electric service ter in your barn to regularly monitor Practical suggestions supplier may use specialized the level of stray voltage present. If Most voltmeter leads are too short equipment and test procedures that animal contact voltage levels are later to make even animal contact voltage allow them to analyze the worst found to exceed 1.0 Volt AC, you may measurements. You may want to use case loading condition at any time want to contact your electric service a set of light-duty car battery jumper during the day so that they may not supplier for a more thorough stray cables or some other type of wire to need to be present during milking. voltage investigation as a preventive extend the length of the voltmeter measure. leads when making measurements to the various contact points. Jumper cables may also be used as temporary bonding jumpers to determine the effect of additional bonding. Monitoring Stray Voltage 8

If animal contact voltages exceed 2.0 system. If a higher than expected location where it can be conveniently volts AC you should take immediate contribution from off-farm sources is read during milking time. Not all action to determine the source(s) of found, your electric service provider voltmeters are suitable for constant the contact voltage, and the safest will take action to reduce stray volt- exposure to the damp environment and most economical way to reduce age from these sources. Your electric found in many locations in a barn. them. service supplier may also identify Carefully choose the right meter and on-farm sources of stray voltage for the proper installation location. Call your electric service supplier to you. A qualified electrician may be request a stray voltage investigation. required to perform work necessary It will help the investigators if you FOR MORE INFORMATION to reduce stray voltage contributions dditional publications related provide the voltage measurements from these on-farm sources. to stray voltage are listed at recorded on the data collection form the end of this document. Im- at the end of this publication. A MONITORING STRAY properly installed electric fencers and Finding the sources of stray voltage VOLTAGE cow trainers are another common can be difficult and time consuming. permanently installed voltme- cause of unwanted electrical expo- It requires knowing where and what ter in your barn is a good way sure and more information on these to measure, knowing what type of Ato regularly monitor the level is provided in the MREC publication sources to look for, being familiar of stray voltage present. Through reg- in this list. For more information with the nature of electricity, and ular observation, you can quickly be- about stray voltage or its detection, having the ability to perform con- come aware of any voltage increase, call your electric service supplier for trolled tests using suitable measuring possibly due to equipment or wiring assistance. Your electric service pro- instruments. shorts, which otherwise may go un- vider can assist you in determining noticed. Figure 3, below, indicates if stray voltage is present, and more Stray voltage sources may originate typical voltmeter connections. The importantly, how excessive levels of from the electrical distribution voltmeter should be installed in a dry stray voltage can be minimized.

FIGURE 3: Typical Voltmeter Connections #18 Insulated Wire To Voltmeter Location

Outside Main Barn Service Wall Panel Inside Barn

Service Ground Ground Wire Rod Outside Barn

Milking Parlor or Stanchion Barn Service Panel Point-to-Point Stray Voltage Measurement Point-to-Reference Ground 30 (For diagnostic purposes only.) feet Farm Wiring Checklist 9

This checklist will assist farmers in visually inspecting their electrical systems and noting potential stray voltage sources. A check mark placed in the “yes” column indicates a potential problem. In most instances, a qualified electrician should be contacted if any electrical equipment or wiring needs to be repaired or replaced. Yes No MAIN FARM SERVICE Connection to the ground rod - loose, corroded...... ______Ground rod(s) missing at the service entrance...... ______BARN SERVICE ENTRANCE Ground rod(s) missing at the service entrance...... ______Connection to ground rod(s) - loose, corroded...... ______Large accumulation of feed dust or other debris in or on service box...... ______Corroded or loose neutral connection...... ______Panel cover missing or removed...... ______MILKHOUSE Wires sitting in water...... ______Electric portable heaters on bulk tank...... ______Broken or missing bonding strap for milkline...... ______Damaged or missing seals on electrical fixtures, switches, outlets, lights, etc...... ______Corrosion of electrical fixtures...... ______IN THE PARLOR OR AROUND THE BARN Pulsator wiring —Pinched wires...... ______—Loose, hanging wires, stripped screws...... ______—Scrapes, breaks or cracks in insulation exposing the conductors...... ______—Broken stall cocks...... ______Wires lying in damp or wet areas...... ______Loose, hanging wires...... ______Broken or bent conduit Energized open wires taped or untaped and extending from ceiling or wall, not in a junction box...... ______120-volt non-polarized or non-grounded appliances used in barn (clocks, heaters, radios, stereos, etc.)...... ______Cow trainer insulators broken, missing, dirty or covered with whitewash...... ______Other Observations Lights alternately brightening or dimming when motors start...... ______Lights seem too bright...... ______Electrical shocks from any equipment...... ______Wires, electrical boxes or motors in wet or damp areas...... ______Frequent fuse blowing...... ______Electric fence or cow trainer ground connected to farm electric system ground...... ______Electric fence or cow trainer ground connected to water or milk lines or stanchions...... ______Bent or broken conduit...... ______Damaged wire insulation exposing conductors...... ______Insulated wires wrapped around metal pipes...... ______Damaged or frayed extension cords...... ______Motors, operating irregularly under load, sparking, etc...... ______Electrical outlets not properly grounded to accept a three-prong plug...... ______Data Collection Form 10

This sheet should be used to record milkhouse and barn area voltage measurements. If any of the animal contact measurements in Section B made WITH a 500 Ohm resistor are greater than 1.0 Volts AC, you may want to call your electric service provider and request assistance in conducting a more thorough stray voltage investigation. NAME: ADDRESS: PHONE: VOLTAGE MEASUREMENTS DATE TIME A. Diagnostic Measurements (taken without 500-ohm resistor) Contact Points VOLTS VOLTS FROM To (AC) (AC) Bulk Tank...... Milkhouse Floor Drain...... ______Milk Pipeline...... Milkhouse Floor Drain...... ______Water Pipe...... Milkhouse Floor Drain...... ______Barn Entrance Panel...... Remote Reference Ground...... ______Water Bowl...... Remote Reference Ground...... ______Stanchion...... Remote Reference Ground...... ______

B. Stray Voltage Measurements (all measurements should be taken with and without 500-ohm resistor to make sure your electrical connections are good) Record voltages at several locations in barn while milking equipment is running. Note which equipment is running during measurements. 1st Measurement 2nd Measurement Cow Contact Points volts (AC) VOLTS (AC) Volts (AC) VOLTS (AC) FROM To (with 500-ohm resistor) (without resistor) (with 500-ohm resistor) (without resistor) Drinking Cup...... Floor...... ______Stanchion...... Floor...... ______Waterer ...... Floor...... ______

Drinking Cup...... Floor...... ______Stanchion...... Floor...... ______Waterer ...... Floor...... ______

Drinking Cup...... Floor...... ______Stanchion...... Floor...... ______Waterer ...... Floor...... ______Mission Statement 11

his publication was developed by the T Midwest Rural Energy Council.

The mission of the MREC is to support outreach, education and research on rural energy issues for the benefit of: • Farms and other rural energy consumers • Rural energy suppliers • Farm organizations and agricultural trade associations • Electrical equipment and allied industries • Government regulatory agencies

Related Publications from the Midwest Rural Energy Council • Farming Safely and Efficiently with Electricity • Equipotential Planes for Stray Voltage Reduction: Installation Guidelines • Planning Electrical Systems For Dairy Expansions • Wiring Handbook for Rural Facilities • Power Quality and Computers on the Farm • Installation and Operation of Fencers, Cow Trainers and Crowd Gates

Midwest Rural Energy Council July, 2010