Reducing air clearance requirements for voltage uprating of overhead line by use of line surge arresters
While uprating an overhead line to a higher voltage level, it is often difficult to achieve the required clearance level for the uprated structure. Use of Transmission Line Arresters (TLAs) is an effective technique in controlling overvoltages and thereby, achieving the required clearance margin. In this paper, suitability of this technique in reducing the clearance margin is discussed. A case study on uprating an existing 275 kV overhead line to 400 kV is investigated here.
An application of metal oxide surge arresters in the elimination of need for closing resistors in EHV breakers
At Florida Power & Light Co., a large percentage of the 500 kV circuit breakers were found to have broken or failing closing resistor mechanisms. A simulation study using the EMTP program for the statistical evaluation of switching surge flashover rates in the absence of breaker closing resistors is described. The stress on the metal oxide (MOV) surge arresters at the line ends is also evaluated. The conclusion is that with the MOV surge arresters at the 500 kV line terminals, breaker closing resistors are not required for the system studied. >
Role of the coronoid process in varus osteoarticular stability of the elbow.
The role of the coronoid process in varus osteoarticular stability of the elbow was investigated in 10 cadaveric elbows. Testing was performed at multiple flexion angles after incremental removal of the coronoid. At each flexion angle, removal of more than 50% of the coronoid produced a statistically significant decrease in the load resisting varus displacement compared with all lesser resection levels (P < .003). There was a trend for decreasing load after removal of 50% of the coronoid. The mean decrease in load across all flexion angles was 10.1%, 50.4%, and 75.4% after removal of 50%, 75%, and 100% of the coronoid, respectively. Resistance to varus displacement tended to decrease more as a percent of control at lower flexion angles than at higher flexion angles after removal of more than 50% of the coronoid. The coronoid process was found to be a key varus stabilizer in the elbow and may contribute more to elbow stability in extension than in flexion.