Testing of Insulators Q. Describe in brief various tests carried out on overhead line insulators. Insulators are used on transmission line towers for providing support to conductors and to provide insulation between line conductor and transmission line tower. The commonly used insulators are pin type, suspension type, string type. The entire HV tests on insulators … Read more

Power Frequency Tests of Insulators Dry Flashover Test Wet Flashover Test Wet and Dry Withstand Test 1. Dry Flashover Test The insulator is in completely dry and clean state. It is connected to the metallic structure or tower as shown in Figure A. Figure A The power frequency source is connected across the insulator string … Read more

Schering Bridge There are various methods for the measurement of capacitance and di-electric loss. Schering Bridge method is very important and popular method to determine these terms.  In this method imperfect capacitor can be compared with a perfect capacitor. (C2 is compared with C1). The imperfect capacitor is represented by its equivalent loss free capacitor C in … Read more

Measurement of Dielectric Constant and Loss Factor Introduction to Dielectric Loss Dielectric constant is also called relative permittivity of the insulating material. Many of the insulating materials have dielectric constant more than unity. These materials show dielectric loss when subjected to AC voltages. Dielectric constant as well as dielectric loss depends on magnitude of voltage … Read more

Loss of Charge Method to Measure Resistance and to Calculate the Resistivity of a Specimen Refer Figure in this figure when B is taken on position 1, the voltage is applied and circuit is charged. But after this if the switch B is taken to position 2, it is disconnected from the supply and the capacitance … Read more

Measurement of Resistivity by Wheatstone Bridge Method (For Liquid Insulators) For liquid insulators the measuring unit (cell) has the following construction. Procedure to find resistivity of a liquid insulator As explained in the previous case of solid insulation, the experimental set up w the same i.e. H.V stable supply voltage to the circuit of Wheatstone … Read more

Measurement of Resistance (Resistivity) by Simple DC Galvanometer Galvanometer is first calibrated by use of standard resistance of the values 10 MΩ with tolerance ± 0.5 to ± 1 %. Calculations The resistance of the specimen (RP) is given by RP = V / D x G Where D = deflection in cm with specimen G = Galvanometer sensitivity A … Read more

Measurement of D.C. Resistivity D.C resistivity can be measured by various methods such as using Galvanometer using D.C. Amplifier and using wheatstone bridge. Prior to study the above methods, let us take the idea of shape of specimen of insulation, and electrode system.Specimen and Electrode For facilitating calculation of D.C. resistivity, the shape of specimen … Read more