In order to determine feasibility of SF6 gas insulated equipment for HVDC station technology a testpole was built and subjected to a long term test of 2 years. The test pole consisted of slightly modified commercially available 550kV ac and 800kV ac gas insulated components. The components were SF6 -air bushings, an air insulated arrester, a SF6 insulated arrester, a SF6 -oil bushing, disconnectors, bus ducts and conical spacers. Testing involved continuous dc stress (500kV and 600kV) lightning and switching impulse tests, polarity reversal tests and ultrasonic partial discharge measurements. Thermal cycling was performed during dc load and went uninterrupted for more than 1 year. No internal breakdowns occurred during any tests. Visual inspection of the spacers at various times during tests and final disassembly revealed no visible flashover traces. The testing has demonstrated that the gas insulated technology is well suited for commercial HVDC applications.test pole consisted of: CIS (Cas Insulated Switchgear) bus spacers, SF6 air bushings, air insulated arrester, SF6 insulated arrester and SF6 oil bushing. The primary concern was the dielectric performance of the components. This project was performed using a combination of 550kV ac equipment (ELK3) and 800kV ac equipment (ELK4). All equipment was modified for dc application by installing special CIS ac spacers. The long term tests were successfully completed in 1996. SF6 insulated CIS is a well established technology and has been used for more than 30 years in high voltage (HV) ac power transmission systems. Applications of CIS technology for HV dc converter stations have been discussed by several authors, see e.g. [1,2]. Several studies have been performed regarding behavior of epoxy spacers under H V dc stress, see e.g. [3,4,5] with references therein.

No abstract

No abstract

In 1991, a Bonneville Power Administration (BPA) worker suffered severe injury during an elechical contact accident involving a welding machine. This incident occurred during a complete station outage at a BPA substation. Injuries to the employee consisted of muscle, tissue, and bone damage to one of the worker's shoulders. Tests simulating the accident were performed at BPAs High Voltage Laboratory and at the substation where the accident originally took place in order to determine why the electrical shock occurred and how this type of accident can be prevented in the future. It was concluded from testing and analysis that the injuries occurred to the worker because he came in bare handed contact with a grounded steel structure and a riser that was being welded. In such a situation, the 60 Hz voltage output from the welding machine had the capability of generating enough current to tetanize the muscles in the worker's arms and chest, probably leading to the muscle, tissue, and bone damage to his shoulder. In February 1991, a BPA employee suffered injury during an electrical contact accident involving a welding machine. The accident occurred at BPAs Spearfish Substation, and injuries consisted of muscle, tissue, and bone damage to the left shoulder. Spearfish Substation taps into the Chenoweth/Goldendale 115-kV line, and then feeds out at 125kV to Klickitat County PUD (Figure 1). A complete station outage was taken at Spearfish to tie expansion work that Klickitat County PUD had been doing into BPA. Disconnect switches to the 12.5-kV regulators were CLOSED.