TOUCHED LIVE WIRE

Timaru Herald, Volume CXLIX, Issue 21963, 15 May 1941, Page 4

TOUCHED LIVE WIRE

Highfield Fatality Question Of Safety Devices Evidence At Inquiry The comment that the safety devices which should have disconnected the power when the lines were contacted by the fencing wire did not act as intended or were not adequate for the purpose was made by the Coroner, Mr C. W. Wood, yesterday, when giving his verdict at the inquest into the death of Thomas Robson, who received a fatal electric shock at Highfield on April 5 when engaged in fencing operations. The formal verdict was: “That Thomas Robson came to his death through his own action in accidentally breaking a high voltage power line, the fallen end of which electrified a wire fence on which he subsequently and in Ignorance of the fence being alive, placed his hand, resulting in his death.” Sergeant J. Crowley conducted the proceedings for the police and Mr J. M. Bishop, who also gave evidence, watched the proceedings for the South Canterbury Power Board. “I have to congratulate you on your attempts to release your father. You took risks as you probably knew, but you did your level best,” the Coroner commended the son during the hearing. Medical evidence was given by Dr. C. S. Fraser, who was called to Highfield to attend Robson, who was lying in a paddock. With the help of two other men he attempted artificial respiration for some time. There seemed a prospect of recovery at the start but he later considered the man dead. He also conducted a post-mortem examination. He found no signs of external serious injury. Knowing the circumstances of the electrifying of the fence which Robson touched, ire considered the cause of death was shock from contact with a live wire fence. He did not consider the condition of the heart would have any bearing one way or the other, except to be a factor in recovery from the artificial respiration. Geoffrey Stewart Robson said that on the day before the accident his father was assisting him to erect a new fence. All the posts were in place and the top wire stapled to the posts all the length of the fence except at the strainer post in the gully at the south end of the fence. There the wire was still attached to the strainer and the loose end was lying on the ground around the post. They then went across the gully and cut the wires of another fence which they were going co straighten and connect with the new fence and carried the loose ends over the gully and dropped them at the new strainer post. The next day his father left with a horse to drag a wire from another fence to the new fence. He later met his father coming up from the gully. He said: “You will have to go and ring up the Power Board. There is a wire broken down here and it is sizzling. As he spoke he half turned and put his hand on the top wire ot the new fence. Witness was looking towards the gully to see where the line was, broken when he heard his father call out, “Oh! Geoff pull me off.” Witness grabbed his father's hand but received an electric shock. He must have been unconscious for he next remembered getting up from the ground. He got hold of his father's leg and managed to free him from the fence. He was still breathing, but choking. Witness summoned medical aid. Condition of Line Stuart Maxton Nicol, a testing engineer employed by the Public Works Department at Christchurch, said that when the accident occurred he was Instructed by the Christchurch District Electrical Engineer to visit the scene and make an examination of the line. He produced a copy of his report. His duties did not include checking to see whether the line was erected to regulation height, but he believed it was so. The line was not equipped with every safety device. At the Coonoor Road sub-station the 11,090 volt side of the transformer was without an overload protection and the safety switch was not in order. The first and only switch to open was Waimate No. 2 feeder switch at the Public Works sub-station at Timaru, known as Grant’s Hill. There was another safety switch between the break in the line and Grant’s Hill, the 6600 volt Glenitl feeder switch at Coonoor Road sub-station. The 6600 volt switch on the evidence of the Power Board was faulty. Their explanation appeared logical. The 11,000 volt transformer switch was, he was told, without protection. The effect of the No. 2 switch being without protection would he to prevent the power line from being automatically disconnected with the supply. It was more likely that the broken end of the transmission line on the Coonoor Road sub-station side of the break would automatically have opened the switch, immediately cutting off the power from the fence. If the switch had been functioning the power would probably have been off a quarter of an hour later when Robson touched ths fence. The cutting off of the supply through the opening of the switch would be the normal effect of an overload when the barbed wire touched the power line. The length of time the power would be off would depend on the policy of the Power Board as ro when it would be closed normally. He was not aware of any general regulations. but in the Public Works policy a switch opening automatically was closed twice and then if opening again was left open until the cause was found. About two minutes would elapse between the first automatic opening and the time it would be lift open. To the Coroner, witness said that the 6600 volt line had a second switch according to the regulations, but according to the Power Board it was not in order. Had the 11,000 volt switch at Coonoor station opened, the chances of death occurring would have depended on the policy of the Power Board in closing the switch after its automatic opening.

Condition of Relays To Mr Bishop: In the light of experience after the accident, the only experience he had had of Coonoor substation, the relays failed to clear the initial fault and the explanation c .cred appeared electrically sound. He wov’ 1 agree that the excessiveness r f the current flow due to the initial short circuit might have caused the relays not to function, but to a suggestion that the relays could have been in good order before the accident, he replied that the severity of the fault caused the relays automatically to trip the switch and the relays should have been capable of doing their job. It v> is a remote possibility that the switch itself may have failed to clear the fault.

To the Coroner: He could not say directly that the switches and protective apparatus were not in order, but would infer so from the fact that they did not function and the evidence of the Power Board. All regulations wire observed with the exception of the overload protection on the 11,000 volt line.

John Montague Bishop, qualified electrical engineer, said that shortly before the accident the 6600 volt s~itch at Coonoor Road was tested and found to bo in order. The contention was that it was the fact that the barbed wire pulled by the Robson’s horse across a gully enabled the barbed wire to touch the Board’s power lines. There were two effects. One to cause the automatic switch at Grant’s Hill to trip, and the other for the 6600 volt switch at Coonoor Road to trip. It appeared that the Grant’s Hill switch did in fact trip and the 6600 volt switch at Coonoor Road tended to trip. In so doing, by the evidence he saw himself, the protective relays had been damaged, thus preventing the completion of the actual tripping of the switch. He added that in his opinion there was sufficient automatic protection for an adequate safeguard to the line in spite of the fact that there was no overload protection on the 11,000 volt side of the

transformer bank at Coonoor Road. He agreed with the previous witness in saving that it was possible that ven with the protection required by the regulations in the 11,000 volt side thgt the protective device might not have operated. It was with confidence that there was adequate protection in ’he 6600 volt side that no steps had 1 —n taken immediately before the accident to instal protective gear on the 11,000 volt side.