The Effect of Controlling Stray and Disc Capacitance of Ceramic String Insulator in the Case of Clean and Contaminated Conditions

Due to their flexibility against the tension force and the easiness of maintenance characteristics of overhead transmission line, one of the biggest problems when using ceramic string insulator is the non-uniform voltage distribution on each insulator disc that connected on the string. This paper analyzes the effect of controlling stray capacitance (Kcsc), disc capacitance (Kcdc) and contaminated pollution (Kccp). In this paper research study considerations, the Electricity Generating Authority of Thailand (EGAT) 115 kV overhead transmission line power towers are simulated in EMTP/ATP drawing and the results were analyzed. As it was found that in the clean condition, when the constant (Kcsc) was conducted and adjustment when Kcsc value has low value (decreases), the string efficiency would be high value (increases) for instances Kcsc=0.01 string efficiency=99%, Kcsc=0.50 string efficiency=64%. When the constant (Kcdc) was adjusted; if Kcdc is low, the string efficiency will also be low for instances at Kcdc=0.01 string efficiency=33%, Kcdc=0.50 string efficiency=40%. Nevertheless, Kcdc adjustment utilizes the appropriate value gained from factory that the k=0, so the value will be 90% higher. As for the contaminated condition, when the constant (Kcsc) was adjusted as shown in Fig.11, if Kcsc value is low, the string efficiency will be high for instances Kcsc=0.01 string efficiency=99%, Kcsc=0.05 string efficiency=65%. When the constant (Kcdc) was adjusted; if Kcdc is low, the string efficiency will also be low for instances at Kcdc=0.01 string efficiency=17%, Kcdc=0.50 string efficiency=40%. Considering on Kccp, for example Kccp=0.01 string efficiency=82% Kccp=0.50 string efficiency=55%.