Until the ongoing investigations are complete, it will be impossible to say exactly what caused the tragic death of two racehorses at Newbury Racecourse on Saturday. However, electrical test equipment expert Megger can suggest a likely scenario that explains why the horses died while people in the same area were only minimally affected.
The root of the problem appears to have been an underground electric cable with faulty or damaged insulation, which allowed electricity to leak into the ground. The effect of this would have been to raise the voltage of the ground around the fault.
The voltage rise would have been highest near the fault, falling away at distances further from the fault. This means that the voltage difference between a location close to the fault and one, say, twelve inches further away would have been small, but the voltage difference between a location close to the fault and one four or five feet away would have been much larger.
This is the key to the mystery, as it’s not voltage that causes electrocution, but current. And it’s voltage difference that makes current to flow.
Because people stand with their feet close together, the voltage difference between the feet of someone standing close to the fault would have been quite small, and only a small current would have flowed through their body. They would probably have felt a small electric shock, but have experienced no harmful after effects. This is exactly what the trainers reported.
The situation for horses is very different, as there is a considerable distance between their front and rear feet. This means that for a horse standing in the vicinity of the fault there would have been a big voltage difference between its front and rear feet. This would have allowed a large current to flow, with the fatal results that were seen.
Other factors would also have been involved. Horses have metal shoes that make good electrical contact with the ground, making it easy for current to flow, whereas people normally wear shoes or boots with soles that are electrical insulators and impede the flow of current.
In addition, sudden collapse from electric shock is typically the result of heart failure caused by current passing through or near the heart muscle. An electric current flowing from leg to leg in a person, however, doesn’t go anywhere near the heart, whereas a current flowing from the front to the rear legs of a horse most certainly does.
This explanation doesn’t make Saturday’s events at Newbury any less tragic, but it does offer a solution to the apparent mystery of why the horses and were affected when people in the same area were not. It also highlights the importance of regularly testing the protection systems that might have been expected to automatically disconnect the electricity supply to a faulty cable before the fault was able to cause injury and death.
