NON-TRADITIONAL STRAY VOLTAGE: AS LEARNED IN THE FIELD

Transcription

1 NON-TRADITIONAL STRAY VOLTAGE: AS LEARNED IN THE FIELD This presentation will concentrate on areas of stray voltage that do not fit the normal stray voltage patterns. I have come across these different stray voltage situations over the years in the field. The animals indicate that they are having problems but the basic stray voltage measurements do not indicate a problem. I keep an open mind, look at the situation, and try to figure out what is causing the problem. After changing the situation, I check back to see whether animal behavior changed. Some of these problem areas I have heard about from other people. That information enters into my investigative procedures. My field experiences have led me to believe that the following situations do affect animals and need to be corrected. INDUCED VOLTAGE Induced voltage is the first of these areas. Induced voltage is a voltage that comes from nearby wiring and shows up on ungrounded devices. Building wiring is manufactured with insulation around it to protect individuals and animals from getting shocks. If that insulation is damaged, then a voltage field exists between the wire and earth. The wire would have 120-volts and earth would have zero volts. The voltage can show up on ungrounded metal devices. An example of induced voltage would be the voltage that exists on a fence located under a high power line and parallel to it. Fences like this are constructed with alternating wood and metal posts. The metal posts allow the induced voltage to be bled off to the earth. Clothes lines with metal wires and wood posts that are built parallel to power lines will also have induced voltage on them. If you try to measure induced voltage with a resistor between the leads, you will always measure zero. You will not see it. This is one reason that I do not use a resistor when checking for stray voltage. A farm that demonstrated induced voltage the best was a stanchion barn where the cows had a high somatic cell count and would not clean up their feed. They would always leave a layer of feed on the floor. Since they were not cleaning up their feed, production was down. We measured two volts between the head stanchions and the floor. With a resistor between the leads, the voltage was zero. These head stanchions were the type that hangs, by chain, between two beams of wood. The head stanchions are metal with wood attached to the inside of the metal, attached by bolts. We shut off circuit breakers in the barn electrical panel to determine where the voltage was coming from. The voltage went to zero when we shut off the circuit supplying electricity to lights in the back part of the barn. With the circuit breaker on and the lights off, the voltage was still there. This was in the summer and the farmer said he could get along without those lights. We shut off the breaker. Within two milkings the concrete was wet from the cows cleaning up the feed. The farmer said that feed was not as good as some that had been fed earlier, when they would not clean it up. The stanchions had a bolt that would touch the cow s neck when she would have her head down eating. When her tongue touched the concrete, or earth, she would get a shock. If the cow maintained contact with the concrete there would be no sustained current. Since the induced voltage came from an alternating current source, the voltage would reappear immediately after the cow broke contact with the concrete. The cow would get another shock the next time she touched the concrete. Basic stray voltage would say this induced voltage would not cause a problem, since there is no sustained current. So, are the cows feeling the voltage or the brief, instantaneous current caused by the induced voltage?

2 Either way, the cow was experienced a shock every time she made contact, which created a stressful environment. I am reminded of a meeting I went to one winter where there was a lot of static electricity. We know that when walking across a carpet, on a dry winter day, a static charge is built up. When we touch something metal, we get shocked. We can touch the metal again, without moving, and nothing happens. Everyone at this meeting was getting shocked when they would touch a drinking fountain, elevator button, or their room door knob. Was there enough voltage or current to cause damage? No, but there was enough to cause discomfort and stress. I have never seen so many nervous people. They were trying to invent ways to touch metal and experience less of a shock. I have also seen induced voltage on milk lines. Researchers have said that voltage on milk lines cannot reach the cows because of the plastic hoses. Induced voltage is also not a problem. My field experience has shown that cows do feel voltage from milk lines, even induced voltage. Milk lines in barns or parlors with a glass milk jar can pick up induced voltage. Sometimes this can come from wiring in the ceiling that has been damaged or from wiring in the barn that has had insulation broken down because of flies. Evidently fly manure is extremely corrosive. One farm had voltage on the milk line when the pit sump pump would turn on. Cows experiencing voltage on the milk line will be nervous whenever the milkers are attached. If they normally stand still, then start moving around when the milkers are attached, and continue until the milkers are taken off, I suspect stray voltage coming from the milk line. This can also be caused by bad vacuum pressure or other problems, but stray voltage is a possibility. I have seen a milk line in a parlor that had plastic elbows at every corner. The milk line sections could be at whatever voltage might be near it. An ungrounded milk line can be grounded to the electrical grounding system by installing a wire between it and the transfer pump on the other side of the milk jar, or back to the electrical panel. I was on a dairy goat farm that was at a point of throwing away their milk because of the high somatic cell count and about to go out of business. This farm had the utility out to check for stray voltage. The utility did not find any problems, but did note that the milk line was not grounded and should be. My investigation did find the ungrounded milk line. It had voltage on it that came from some nearby fluorescent lights. There was voltage between the milk line and the platform where the goats stood while being milked. We attached a wire between the milk line and the platform, which eliminated the voltage difference. The somatic cell count dropped and the farmer is still milking goats. Wiring damaged by flies has also caused voltage on head stanchions. Wire type UF, which is permitted to be used underground, is approved for wiring in animal confinement structures. This wire can also be damaged by flies. My recommendation for barns is to install the barn wiring, especially lighting circuits, in conduit. It costs a little more to do this but it protects the wire from the flies and any other damage, reducing the possibility of stray voltage. ELECTROMAGNETIC FIELDS Alternating current flowing through a conductor sets up an electromagnetic field around the conductor. About twenty years ago there was a nationwide concern about electromagnetic fields

3 causing leukemia in children. That concern was based on some people realizing there was childhood leukemia in certain neighborhoods. They looked around to see what might be common among the neighborhoods. They saw high power lines and decided that these lines might be the cause. There was no actual data to link the high power lines and the leukemia. Many people were concerned about this, resulting in much research being conducted. There was no data that linked the two. I worked for a utility at the time and we had EMF meters to measure electromagnetic fields in and around homes. EMF fields do drop off significantly with distance. The household item that seemed to be the biggest problem was the cordless phones plugged in by the bed and placed on the night stand. It has a transformer, which produces electromagnetic fields and is located near the head of a person sleeping in the bed for extended periods every night. This had a much higher EMF field than EMF fields coming from utility lines. It appears, now, that exposure to electromagnetic fields is causing problems in animal environments. Current passing through an equipotential plane will set up an electromagnetic field. The first dairy where I experienced this was on a farm near Ivanhoe, MN. This was a new building that was designed for robot milking. There was a slotted floor in the free stall area with a pit below the floor. There was no re-rod in the floor, since it was a slotted floor. Water fountains were located on the slotted floor and did not have any electricity to them. With no power to the fountains and no equipotential plane in the floor, there was no voltage between any of the fountains and the floor. The farmer had water meters to monitor the water intake of the animals. The nutritionist had me come to the farm that day, since he was concerned about the low water intake per cow. I did not find any traditional stray voltage problems that might cause low water consumption. There were other people at the farm that day doing their own investigations. Current was flowing into the re-rod in the pit walls. When the last utility neutral was disconnected, the current into the re-rod stopped. This was on a Friday afternoon. The farmer used a standby generator for the weekend. There was no current going to the pit re-rod when the generator was operating. The animal water consumption went up. The only thing that changed was that there was no current going to the pit re-rod. A second dairy where this was demonstrated was on a farm south of Saint Cloud, MN. This farm had two barns constructed the same. The bottom half of the walls were concrete, with rerod in the walls. Both barns were an open bedding pack barn. The cows could lie wherever they wanted to. One barn, used for calving and hospital, had the electrical panel grounded to a ground rod. The other barn, with production cows, had the electrical panel grounded to the re-rod in the walls. The wire coming into the panel from the ground rod was too large to fit into the neutral/grounding strip, so the electrician did not attach it. The animals in the calving barn would lie up against the walls. The production cows would not lie at least eight feet from the walls. Cows would spend time in both barns depending on where they were at in their production cycle. They would lie up against the walls in the one barn, but not in the other. This had been happening for years. The farmer and his wife had noticed this but did not have any explanation as to why. At the production barn we disconnected the wire going to the re-rod and attached the wire going to the ground rod. According to the farmer, the first night the production cows were within the eight foot zone. After that they would lie up against the walls. Milk production went up and production stayed up longer than normal when the warmer summer weather started. The cows could decide where they wanted to be and it was not near the walls where there was current in the re-rod.

4 Electromagnetic fields can also come from electrical equipment. Some stray voltage investigators say that all fluorescent lights, especially the screw-in type, should be removed and replaced with incandescent lights. I have seen some fluorescent lights that do need to be changed, but not all. This is especially true of those lights that are near the end of their lifetime, when the ballast is old and failing. When I detect an electromagnetic field in the animal area, I start by shutting off circuit breakers to determine what circuit is causing the problem. We narrow it down from there. There was a large dairy in Iowa that seemed to be having production problems in one barn. I had been there once and measured with a volt meter looking for traditional stray voltage and did not find any problems. They had me make a return trip along with and a person that uses divining rods to find problems affecting cows. He found some things I could not detect, but in the barn in question I found an electromagnetic field that he did not detect. We shut off breakers in that barn s panel until the electromagnetic field stopped. That circuit was for an outside security light. The farmer said that security light was broken about three months earlier. I asked when they started having production problems in that barn. He said it was about the same time. They had not made the connection between the two. The breaker had been left on even though the light was broken. He shut off the breaker. Checking back later, the farmer said the production in that barn was improving. Another farm south of St Cloud was having problems with high somatic cell counts. I checked out his stanchion barn and he had some electromagnetic fields in the barn. We found some of that coming from a screw-in fluorescent light back by the gutter cleaner motor. Some fields were coming from a fan and from two thermostats mounted on wood posts. Other fields were coming from some other screw-in fluorescent lights. He installed LED lighting in the barn and new thermostats. He also had the fans rewired for 240-volt operation. His cows are doing much better. A beef cattle farm northeast of Pipestone has had problems with raising yearling beef cattle since building an open front shed several years ago. The yearlings have not gained weight in the new building like they had before the barn was built. Recently he was having problems with the yearlings dying because of complications with kidney stones. This was last July. The veterinarian from Pipestone recommended he have a stray voltage check, since most things pointed to poor water consumption. I checked the barn and did not find any voltage at the fountains, as expected, since an equipotential plane was installed in the floor. I also did not detect much current in the floor near the fountains. My checks did not indicate there was a stray voltage problem. We did observe that the yearlings were not drinking normally. They would crowd around the fountains and were lapping at the water. The building, in addition to having the equipotential plane, had a four wire service. Both the equipotential plane and four-wire service are required for new buildings to prevent stray voltage. We did measure current in the grounding wire going to the equipotential plane. The farmer had another service down the road that served some grain bins. When he turned on the bin fans, the current going to the barn equipotential plane increased. That told us that there was current from the utility going into the ground through the equipotential plane. The farmer was going to talk to the utility about installing a neutral isolator at the farm transformer, which would keep the utility neutral current from going through the plane. A few days later, prior to the neutral isolator, the farmer was

5 watching the yearlings having trouble drinking water. His son, who works for an electrician, disconnected all wires going to the barn, including the fourth wire. The yearlings immediately started putting their mouths in the water and drinking. The animals would then satisfy their thirst and move away from the fountain. The main problem causing the kidney stones was that the dominant animals would just stay at the fountain and the other animals would get very little water. After disconnecting the wires, there were no more calf losses. He sold the yearlings shortly after disconnecting power. As of mid-november, he has just brought new calves into the facility and the utility has installed a neutral isolator. Some people have wondered if there should be a name other than stray voltage for the problems caused by currents and/or electromagnetic fields. My opinion is that coming up with a new name would cause more confusion for everyone. Since both are associated with electricity, the term stray voltage is still appropriate. HARMONICS Another non-traditional area is harmonics. This is linked with the discussion on both electromagnetic fields and current in the equipotential planes. Our normal electricity is alternating current at 60 cycles per second. Harmonics are multiples of 60 cycles, such as 120 and 180 cycles per second. Harmonics are the reason that wiring in office buildings have changed. Computers generating harmonics cause an increase in the neutral current. Circuits can no longer share a neutral and the neutral conductor must now be at least as large as the hot wire. Harmonics in a dairy environment are primarily caused by electronic equipment; such as computers, electronic ballasts in fluorescent lighting, and variable speed motors. Since July 2012, only electronic ballasts are available for fluorescent lights. I was on a farm north of St Cloud that had current in the equipotential plane. They had fluorescent light fixtures with electronic ballasts. Normally, as mentioned in the previous session on basic electricity, the neutral carries the difference in current between two circuits on different phases. There were two circuits for the lights in the tie stall barn. Each circuit used five amps on both the hot wire and neutral. I expected zero amps on the neutral at the main panel when both circuits were energized. The neutral current actually went to nine amps. I had a meter that measured harmonics and found that there were harmonics on both circuits. This extra neutral current was going to the equipotential plane. Filters were installed at the circuit breakers in the barn electrical panel to eliminate the harmonics going to the equipotential plane. Variable speed, or variable frequency, motors have been the cause of several problems in dairy parlors. If not wired properly, they will interfere with reading cow ID s, as well as putting harmonics on the barn grounding system. Filters should be installed in the motor controller and a special shielded wire should be run between the controller and the motor, and should be as short as possible. The newer LED lights do not have any harmonics associated with them, since ballasts are not used. They also work well in cold weather. They are much more efficient than incandescent lights and more efficient than fluorescent lights. LED lights are more expensive to purchase, but are less expensive over the life cycle of the light. We will see more LED lights in the future.

6 As we have seen, stray voltage affects animals in various ways. Many of the stray voltage symptoms can have several possible causes, but we need to keep stray voltage as an option. I think we have to continue to approach stray voltage with an open mind. I believe that stray voltage should be checked on every livestock farm. It should be one of the items that need to be checked periodically. Many times stray voltage is checked as a last result, when nothing else corrects a problem. Stray voltage is present many times and does correct the problem. Stray voltage is something we can t see and don t feel; therefore, we don t think of it. Pay Attention to the Cows! Try to figure out what the cows are telling us. I know you already to do this in your profession. As we work together as a team to help Minnesota livestock producers, consider the possibility of stray voltage.