Resistive Shunts There are various types of resistive shunts used in “Impulse current measurements”. Such shunts are : Low ohmic resistive shunt Bifilar flat-strip type resistive shunt Co-axial Tubular / Park shunt Co-axial squirrel cage type resistive shunt Characteristics of such shunts and their limitations Low ohmio resistive shunt : Large dimentions and hence it … Read more

Potential Divider Across Low resistances arm R2 electrostatic voltmeter or high impedance voltmeter is connected. Low resistances arm R2 and potential divider are connected as shown in the Figure. Due to sudden changes in voltage caused by Switching operations Flash over of test voltage Short circuit flash over or damage may occur divider elements. This is due … Read more

High Series Resistance with Micro Ammeter A very high resistance of the value of a few hundreds of megaohms is connected in series with a micrometer for measurement of High dc voltages as shown in Figure. A large celebrated resistance R is connected in series to the moving coil micrometer. The current I flowing the … Read more

Impulse Current Generator Protective gear like surge diverters have to discharge the lightning circuits without damage. Figure A Therefore, generation of impulse current waveforms of high magnitude (100 KA peak) find application in test work as well as basic research on non-linear resistors, electric arc studies, and studies relating to electric plasmas in high current … Read more

Tripping and Control of Impulse Generators Q. With a neat sketch explain trigatron spark gap used in impulse generators. Figure A Tripping : The gaps are stanged such that the parking of one pap results in automatic sparking of other gaps as overvoltage is impressed on the other. In order to have consistency in sparking … Read more

Generation of Impulse Voltages  Transient overvoltages due to lightning and switching surges cause steep build-up of voltage on transmission lines and other electrical apparatus .  It is therefore necessary to generate these kind of transient overvoltages in laboratories so as to check our protective systems. These transient overvoltages are of impulse type. Impulse voltage is … Read more

Resonant Transformers Q. Describe the principle of operation of a resonant transformer ? How to advantageous over the cascade connected transformers ? Resonant transformer work on the principle that the load capacitance is variable and for certain loading when the capacitance is equal to inductance of the circuit resonance may occur. Under this condition then, … Read more

Cascade Transformers Q. What is Cascaded Transformer? Explain why cascading is necessary? With neat diagram, explain a three stage Cascaded transformer system. Necessity of Cascade Transformers : For higher voltage greater than 700 kV` single unit constructions becomes difficult and costly due to insulation problems.  Figure A Also, transportation and erection of large transformers become difficult. The … Read more

Types of Devices to Measure High Currents Use of co-axial park’s shunt Squirrel cage shunt. Use of Rogowski coils Use of magnetic links Faraday’s ammeters C.R.O.

Use of Current Transformer (CT) for High Current Measurement Difference in Use of CT and Shunt Sr. No. CT Shunt 1. Power loss in measuring is very small or Nil. Power loss is more when shunt is used for H. V. Current measured. 2. Electrical isolation from High voltage circuits in power system. Electrical isolation … Read more