Northwest Hydro Tech Session_2017

Transcription

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2 STEP POTENTIAL FROM AN OPERATORS VIEW Presented by Fred

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4 WAC ELECTRICAL WORKERS SAFETY RULES-FOREWORD. This chapter is not intended to be a complete job description nor is it expected that the chapter covers every hazard that an employee may encounter. When a hazard exists that is not covered by this chapter, the leadworker and employees are expected, in good faith, to mutually discuss the hazard and agree how to perform the work with the greatest degree of safety.

5 WAC ELECTRICAL WORKERS SAFETY RULES Experience has proven that the majority of injuries and deaths are preventable. Most injuries and deaths are not due to defective equipment but are due to failure on the part of the employees and those in authority to observe safety rules and failure to use safety devices. In the last analysis, this chapter is a compilation of experience and common sense. Electrical safety requires that the work be properly planned, executed by the use of good judgment and under the direction of intelligent supervision.

6 WAC SCOPE AND APPLICATION. (1) This chapter covers the operation, maintenance, and construction of electric power generation, control, transformation, transmission, and distribution lines and equipment. These provisions apply to:

7 WAC SCOPE AND APPLICATION. (a) Power generation, transmission, and distribution installations, including related equipment for the purpose of communication or metering, which are accessible only to qualified electrical employees;

8 WAC Working on or near exposed energized parts. THIS SECTION APPLIES TO WORK ON EXPOSED LIVE PARTS, OR NEAR ENOUGH TO THEM, TO EXPOSE THE EMPLOYEE TO ANY HAZARD THEY PRESENT. (1) GENERAL. ONLY QUALIFIED ELECTRICAL EMPLOYEES MAY WORK ON OR WITH EXPOSED ENERGIZED LINES OR PARTS OF EQUIPMENT. ONLY QUALIFIED ELECTRICAL EMPLOYEES MAY WORK IN AREAS CONTAINING UNGUARDED, UNINSULATED ENERGIZED LINES OR PARTS OF EQUIPMENT OPERATING AT 50 VOLTS OR MORE. ELECTRIC LINES AND EQUIPMENT SHALL BE CONSIDERED AND TREATED AS ENERGIZED UNLESS THE PROVISIONS OF WAC THROUGH OR HAVE BEEN FOLLOWED.

9 WAC : Grounding for the Protection of employees (3) EQUIPOTENTIAL ZONE. TEMPORARY PROTECTIVE GROUNDS AND BONDING JUMPERS SHALL BE PLACED AT SUCH LOCATIONS AND ARRANGED IN SUCH A MANNER AS TO PREVENT EACH EMPLOYEE FROM BEING EXPOSED TO HAZARDOUS DIFFERENCES IN ELECTRICAL POTENTIAL.

10 Hazard Avoidance Practices The employer must assure that each employee has been trained to recognize and is appropriately qualified to work near any electrical hazard that might be encountered at a worksite. Tree workers using ladders, platforms, and aerial devices, including insulated aerial devices, are subject to the same minimum approach distances as other tree workers.

11 In touch potential, if someone touches what is in contact with the powerline, electricity will travel through that person s body to get to the ground.

12 TOUCH OR STEP POTENTIAL?

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15 Potential Hazard Situations Lightning Downed wires Energized vehicles or tools Energized, grounded trees or tree limbs

16 In step potential, electricity spreads like ripples or rings over the surface of the ground away from the point of the contact. Each ring carries a different voltage as it travels into the ground. If they step on one ring while their foot is on the other ring electricity will make up to difference in voltage through the body.

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18 In August of 2013 Madras mourns a local farmer killed by lightning beneath a tree.

19 OSLO (AFP) - MORE THAN 300 WILD REINDEER HAVE BEEN KILLED BY LIGHTNING IN SOUTHERN NORWAY, OFFICIALS SAID MONDAY, IN THE LARGEST SUCH INCIDENT KNOWN TO DATE. THE 323 REINDEER, INCLUDING 70 YOUNG, WERE FOUND ON FRIDAY BY A GAMEKEEPER ON THE HARDANGERVIDDA PLATEAU, A NATIONAL PARK WHERE EUROPE'S LARGEST HERD OF SOME 10,000 WILD REINDEER ROAM FREE

20 Researchers suspect what happened to the caribou was: a single bolt of lightning hit the ground and the electric current spread horizontally along the moist top soil. As it hit the front legs of the caribou, a "potential difference developed between the animals' front and back hooves." That causes a jolt, which stopped their hearts, and that's how you kill 53 caribous in a split second.

21 This is a very strong reminder of what Lightning can do. This was somewhere in McCook County. There is 21 head of cattle that were around this metal bale feeder when it was hit with one bolt of lightening and it killed them all. That is about $45,000 worth of loss.

22 All the cows facing the lightning strike would have their fore hooves closer to the strike point than their rear hooves. This would result in a difference of potential between their fore and rear legs, causing current to flow through their bodies, including the heart area, and killing the cow. On the other hand, those cows with their flanks turned towards the lighting strike would have a greater chance of surviving, as the distance between their fore legs and therefore the voltage applied between them, would be relatively small, resulting in a lesser current flow.

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24 Probably the most commonly noted Ground Potential Rise or Earth Potential Rise event involves the death of cows in a field during a lightning strike. Imagine lightning striking the center of an open field where cows are standing. The current injected into the earth flows radially away from the strike point, in all directions, creating voltage gradients on the surface of the earth, also in a radial direction.

25 According to the NOAA, there were five people killed in the U.S. last year by lightning strikes: two in Florida, two in Louisiana and one in Mississippi. There were 27 deaths in 2015.

26 As the severe weather starts to roll in this summer please keep this in mind. If you start to see lightning and hear thunder you need to get out of the open. Off of the Lakes, off of the Golf Course etc so that you are safe.

27 Aerial devices brought into contact with energized electrical conductors shall be considered energized. Contact with the vehicle and/or any attached equipment such as brush chippers must be avoided

28 Workers must never assume that a conductor lying on the ground is deenergized unless a utility representative on-site has confirmed that it is so.

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30 Escaping Step Potential Hazards Use very short, shuffling steps, or move away from the electrical fault keeping both feet close together. Avoid taking large steps. Avoid direct or indirect contact with any objects as you exit the hazard area.

31 FRED L. NAUGHT, C.U.S.P. High Voltage Consultant Department of Labor and Industries Division of Occupational Safety and Health Cell #(509) FAX #(509)