Suspension insulators or string insulators are very widely used in electrical overhead transmission system. National institute of technology rourkela certificate this is to certify that the thesis entitled, measurement of voltage distribution on high voltage suspension insulator string under polluted. In case of the clean string insulator condition, the string efficiency which the insulator consists of 5, 6, 7 insulator string without guard ring equals 69. Vph the phase voltage across the subsequent units measured from the ground respectively.
Measurement of voltage distribution on high voltage. The following points may be noted regarding the potential distribution over string of suspension insulators. However, the electric field and potential distribution along an insulator string owing to the existence of metal conjunctions and resulting stray capacitances is not uniform and the. Field distribution over 230 kv insulator strings, international journal.
Sep 25, 2011 string efficiency is an important consideration since it decides the potential distribution along the string. Potential distribution over suspension insulator string. Determine the potential distribution along the insulators strain. Using post insulator in higher voltage is not economical and suspension type insulator is evolved. The greater the string efficiency, the more uniform is the voltage distribution. Potential distribution along a suspension insulator string have been determined by fem kontargyri et al, 2005 and theoretical model which considered the contamination effect in dhalaan 2003 b. String efficiency conductor voltage nxvoltage across the disc nearest to conductor n number of discs in suspension insulator. Voltage distribution over suspension insulator string. For suspension type of insulators, the ratio of voltage across the whole string to the product of number of discs and the voltage across the disc nearest to the conductor is known as string efficiency.
Effects of transmission tower and conductor in order to investigate tower and conductor effects on voltage distribution, a string of insulator. Due to the presence of shunt capacitor, the voltage. The disc near the line conductor is extremely stressed and takes the maximum voltage in the absence of stress. First of all thanks for visiting electrical engineering info now let us discuss p otential distribution in a string of suspension insulators. Therefore it is very much essential for insulator string to relate the potential distribution and electric field distribution to that of the respective ideal string accurately. Xv international symposium on high voltage engineering t1272. Pdf suspension insulator string is widely used as insulator structures in high voltage overhead power. A string of suspension insulator consists of a number of porcelain discs connected in series through metallic links. The porcelain portion of each disc is in between two metal links. Let us suppose that self capacitance of each disc is c. Simulation of potential and electric field due to defective. Thus if the voltage across each disc becomes equal then string. String efficiency of suspension insulators is an important consideration since it decides the potential distribution along the string.
Voltage across the string number of discs in the string voltage across disc nearest to conductor. Fundamentals of electric circuits national university. Voltage distribution in a suspension insulator strain. Several experimental and simulation methods have been developed for the computation of electric fields and potentials along an insulator string 4. The greater string efficiency of suspension insulators, the more uniform is the voltage distribution. The computation of electric potential distribution across suspension insulator strings used for high voltage overhead transmission lines is very. An overhead 3phase transmission line, which has phase voltage 30 kv, is hanging from a three insulators suspension strain. Suspension insulators or string insulators are very widely used in an. Voltage distribution over a suspension insulator string. String efficiency of a suspension insulator youtube. In case of the clean string insulator condition, the string efficiency which the insulator consists of 5, 6, 7 insulatorstring without guard ring equals 69.
Pin type insulator consists of single or multiple shells arranged in parallel and mounted on a crossarm of the pole or tower. This phenomenon can lead to corona discharge on insulator surface and therefore should be considered before insulator usage. Fig 11 shows the equivalent circuit for a 3discs string. The effect of stray capacitance over voltage distribution the presence of stray capacitance causes unequal potential distribution over the string. The simulation methods give the possibility to examine the. The voltage across the various discs of a string of suspension insulator having identical discs is different due to a. Potential distribution over suspension insulator mathematical expression. Grading ring or guard ring equalizes the potential distribution across each disc in suspension insulator. Calculation of voltage distribution along porcelain. Thus 100% string efficiency is an ideal case for which the volatge across each disc will be exactly the same.
The end unit of the string which is the closest to the line takes maximum potential difference and the upper units have a gradually decreased potential difference until the uppermost unit which has. String efficiency of suspension insulators and methods of. The capacitance between the links and the earth is 0,2 c, where c is the capacitance of an insulator determine the potential distribution along the insulators strain. A string of suspension insulator consists of a number of porcelain discs connected in. Jul 23, 2017 in the previous article, we have discussed different types of insulators used in an overhead transmission line. Evaluation of string efficiency and voltage distribution of. Potential distribution over a suspension insulator string the figure below shows a 3disc string of suspension insulator. String efficiency of suspension insulator electrical. String efficiency of suspension insulators and methods of improving.
In this article, we will be talking about voltage distribution and string efficiency of suspension insulator. The suspension insulator type 523 was used by provincial electricity authority pea in thailand. On the voltage distribution across a string of suspension. Orientsuspension insulators,voltage distribution in. We talked about advantages and disadvantages of each type of insulators. Potential distribution over suspension insulator string string efficiency the voltage applied across the string of suspension insulators is not uniformly distributed across various units or discs. Insulator string, electric potential distribution, comsol multiphysics, solid dielectric material. Electrical transmission and distribution insulator.
Voltage distribution over suspension insulator string efficiency. Structural advantage of using vstrings when comparing the relative advantages and disadvantages of using suspension insulators vs. String effeciency and methods to improve string effeciency. This unequal potential distribution is undesirable and is usually expressed in terms of string efficiency. Optimal corona ring selection for 230 kv ceramic istring. String efficiency of suspension insulator when the voltage is applied across the suspension insulator string, it is unequally distributed across the individual unit. Each suspension disc is designed for normal voltage rating. In this project, calculate the voltage distribution along a string of 5 suspension insulators, and determine the efficiency of string and we get efficiency equal to. Insulators types of electrical insulators in overhead lines.
To perform testing of ct, pts and string insulators. This structure can enabled them form the insulator string by fitting into themselves one another as per voltage requirement. The capacitance between the links and the earth is 0,2 c, where c is the capacitance of an insulator. Suspension insulator for voltages greater than 33 kv, it is a usual practice to use suspension type insulators, consisting of a number of glass or porcelain discs connected in series by metal links in the form of a string. The voltage across the nearest disc to the conductor is maximum than others disc.
Let us further assume that shunt capacitance c1 is some fraction k of self capacitance i. Solved reasons for unequal potential distribution over a. Ceramicporcelain insulators are widely used in power transmission lines to provide mechanical support for high voltage conductors in addition to withstand electrical stresses. String efficiency of suspension insulator electrical concepts. Jan 07, 2019 in suspension insulator numbers of insulators are connected in series to form a string and the line conductor is carried by the bottom most insulator. Simulation and measurement of the voltage distribution on. Mirzaie abstract porcelain string insulators are extensively utilized in high voltage transmission lines. Potential distribution over a suspension insulator string. Potential and electric field distribution of 220kv insulator. The effect of stray capacitance over voltage distribution using kcl at each node it can be found that.
A suspension type string insulator consists of a number of porcelain discs connected in series through metallic links. The figure below shows a 3disc string of suspension insulator. Let us know how the potential is distributed over each unit of suspension insulator whether is it uniform or nonuniform. Disc insulators are connected together in series to make a string which is suspension type insulators. The designing of sheds or petticoats should be such that even when the outer surface is wet due to rain,the inner dry surface provides sufficient leakage resistance. The conductor is suspended at the bottom end of this string while the top end is secured to the crossarm of the tower. This is because of the capacitances formed between the metal parts of the insulators and tower structure.
Modeling of high voltage insulator strings through finite. Structural advantage of using vstrings power line systems. Explicit closedform solution is given for the case in which cg does not vary from unit to unit and the form of tapering needed. Pdf a set of models for investigation of voltage distribution along. Pdf simulation of potential and electric field across. They are used to provide support to the conductors and to. However, there is a significant thing to be considered in case of these string insulators, known as string efficiency. As per the voltage grade the no of disc isolators are increased or decreased so that is is suitable for any voltage level. In operational high voltage, the nonuniformity of potential distribution across the insulator string is due to the presence of stray capacitance. Suspension insulators or string insulators are very widely used in an electrical overhead transmission system. Types of insulators in transmission lines electrical4u. Each insulator of a suspension string is called disc insulator because of their disc like shape. Due to the presence of shunt capacitor, the voltage across the suspension insulators does not distribute itself uniformly across the each disc.
Mar 16, 2017 evaluation of string efficiency and voltage distribution of 400 kv over a string of glass suspension type insulator in different atmospheric condition ijsrdvol. The effect of stray capacitance over voltage distribution stray capacitance causes unequal voltage distribution over the string. On the top of the insulator the conductor bound into a groove,which is cemented on to a galvanized steel. Faulty insulators could appear in the hv transmission line insulator string under the comprehensive effect of electrical, mechanical and environmental factors and they can be detected according to the space potential and electric field distribution variation characteristics around the insulator string. However, there is a significant thing to be considered in case of these string. These capacitances could be made negligibly small by increasing the distance between the. The efficient string, efficient string upgrade, and solved problems on string efficiency and voltage distribution should be introduced in a complex way, and use many formulas, if you need the details about voltage distribution in suspension insulators please contact orient. Apr 25, 2018 string efficiency conductor voltage nxvoltage across the disc nearest to conductor n number of discs in suspension insulator. Modeling of high voltage insulator strings through finite element. The following points may be noted regarding the potential distribution over a string of suspension insulators.
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