Harmonic

Conventional ground fault protection schemes can be applied for any generator terminal connection but it covers at most 95 % of generator stator length. 100 % protection for synchronous generator stator winding can be achieved by a combination of zero sequence and third harmonic protection schemes. The implementation of the third harmonic scheme on any generator is determined by magnitude of third harmonic voltage produced in the generator. The methods of connecting the generator terminal also influence the range of third harmonic voltage at the stator terminal and neutral. An investigation into the compatibility of particular generator configuration with the third harmonic scheme is important to prevent protection mal-operation since the scheme is hampered in performance by certain factors which include grounding method employed and generator terminal connection among others. In this paper, the modelling of parallel unit-connected generators of the second order is presented to stud...

Since Kocher and Billroth refined an acceptable technique, the thyroidectomy has become one of the most frequent procedures in endocrine surgery and bilateral total thyroidectomy is performed in the majority of thyroid diseases. This work evaluated the use of the Harmonic(®) FOCUS and traditional suture ligation (knot and tie) technique in a prospective, randomized study of open thyroidectomy. Eighty two patients were randomized and divided into two similarly sized groups: the Harmonic(®) FOCUS group (F group) and traditional group (T group). The use of the harmonic FOCUS shows some statistically significant advantages limited to a few intraoperative parameters: surgical time and volume of blood loss. The surgical time was significantly shorter in F group than in the T group (105 ± 27 min vs 143 ± 32 respectively; p < 0.05). Intraoperative volume blood loss was significantly more in the T group than in the F group (36 ± 23 ml vs. 24 ± 18; p < 0.05). The postoperative parameter...