Dec 07, 2017 a suspension type string insulator consists of a number of porcelain discs connected in series through metallic links. A difference equation formulation is given for the problem of determining the voltage distribution across a string of suspension insulators, taking into account the capacitance cg between the insulator hardware and the guard ring, and the conductance of the insulator. Voltage distribution over suspension insulator string. Xv international symposium on high voltage engineering t1272. Voltage distribution in a suspension insulator strain. The capacitance between the links and the earth is 0,2 c, where c is the capacitance of an insulator. Voltage across the string number of discs in the string voltage across disc nearest to conductor. A suspension type string insulator consists of a number of porcelain discs connected in series through metallic links. Let us suppose that self capacitance of each disc is c.
String efficiency of suspension insulators is an important consideration since it decides the potential distribution along the string. The effect of stray capacitance over voltage distribution stray capacitance causes unequal voltage distribution over the string. Potential distribution over a suspension insulator string the figure below shows a 3disc string of suspension insulator. 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 effeciency and methods to improve string effeciency. On the voltage distribution across a string of suspension. Optimal corona ring selection for 230 kv ceramic istring.
Potential distribution over suspension insulator string eeeguide. 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. This phenomenon can lead to corona discharge on insulator surface and therefore should be considered before insulator usage. Evaluation of string efficiency and voltage distribution of.
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. As per the voltage grade the no of disc isolators are increased or decreased so that is is suitable for any voltage level. Pin type insulator consists of single or multiple shells arranged in parallel and mounted on a crossarm of the pole or tower. Thus if the voltage across each disc becomes equal then string. Determine the potential distribution along the insulators strain. Ceramicporcelain insulators are widely used in power transmission lines to provide mechanical support for high voltage conductors in addition to withstand electrical stresses. A string of suspension insulator consists of a number of porcelain discs connected in series through metallic links. Pdf simulation of potential and electric field across. 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.
Potential distribution over a string of suspension insulators. These capacitances could be made negligibly small by increasing the distance between the. Fundamentals of electric circuits national university. The greater the string efficiency, the more uniform is the voltage distribution.
Potential distribution over a string of suspension insulators p. Orientsuspension insulators,voltage distribution in. Simulation and measurement of the voltage distribution on. The computation of electric potential distribution across suspension insulator strings used for high voltage overhead transmission lines is very. 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. 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. String efficiency of suspension insulators and methods of. Let us further assume that shunt capacitance c1 is some fraction k of self capacitance i. Voltage distribution over a suspension insulator string. The insulators used in over head electrical power transmission lines for suspension of over head conductors, perform significant role in the transmission of power. Effects of transmission tower and conductor in order to investigate tower and conductor effects on voltage distribution, a string of insulator. 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. 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.
Apr 25, 2018 string efficiency conductor voltage nxvoltage across the disc nearest to conductor n number of discs in suspension insulator. A string of suspension insulator consists of a number of porcelain discs connected in. Potential distribution over suspension insulator mathematical expression. 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. 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. Let us know how the potential is distributed over each unit of suspension insulator whether is it uniform or nonuniform.
In the previous article, we have discussed different types of insulators used in an overhead transmission line. Structural advantage of using vstrings power line systems. The voltage across the nearest disc to the conductor is maximum than others disc. The voltage across the various discs of a string of suspension insulator having identical discs is different due to a. Explicit closedform solution is given for the case in which cg does not vary from unit to unit and the form of tapering needed. Fig 11 shows the equivalent circuit for a 3discs string. Suspension insulators or string insulators are very widely used in an. 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. As a result of lightning, switching or temporary over voltages that could initiate flashover under worst weather conditions, and to operate within interference limits.
Types of insulators in transmission lines electrical4u. Modeling of high voltage insulator strings through finite. We talked about advantages and disadvantages of each type of insulators. The greater string efficiency of suspension insulators, the more uniform is the voltage distribution. String efficiency of a suspension insulator youtube. The disc near the line conductor is extremely stressed and takes the maximum voltage in the absence of stress. Due to the presence of shunt capacitor, the voltage. Solved reasons for unequal potential distribution over a. Potential and electric field distribution of 220kv insulator. Disc insulators are connected together in series to make a string which is suspension type insulators. An overhead 3phase transmission line, which has phase voltage 30 kv, is hanging from a three insulators suspension strain.
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. However, there is a significant thing to be considered in case of these string. Insulator string, electric potential distribution, comsol multiphysics, solid dielectric material. The conductor is suspended at the bottom end of this string while the top end is secured to the crossarm of the tower. The porcelain portion of each disc is in between two metal links. Modeling of high voltage insulator strings through finite element. The suspension insulator type 523 was used by provincial electricity authority pea in thailand. To perform testing of ct, pts and string insulators. In operational high voltage, the nonuniformity of potential distribution across the insulator string is due to the presence of stray capacitance. String efficiency of suspension insulator electrical concepts. Sep 25, 2011 string efficiency is an important consideration since it decides the potential distribution along the string.
Jul 23, 2017 in the previous article, we have discussed different types of insulators used in an overhead transmission line. String efficiency of suspension insulator electrical. Electrical transmission and distribution insulator. 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. Potential distribution over suspension insulator string. Thus 100% string efficiency is an ideal case for which the volatge across each disc will be exactly the same. This structure can enabled them form the insulator string by fitting into themselves one another as per voltage requirement. Field distribution over 230 kv insulator strings, international journal. Suspension insulators or string insulators are very widely used in an electrical overhead transmission system.
Pdf suspension insulator string is widely used as insulator structures in high voltage overhead power. Structural advantage of using vstrings when comparing the relative advantages and disadvantages of using suspension insulators vs. Mirzaie abstract porcelain string insulators are extensively utilized in high voltage transmission lines. The figure below shows a 3disc string of suspension insulator. Suspension insulators or string insulators are very widely used in electrical overhead transmission system.
The simulation methods give the possibility to examine the. Simulation of potential and electric field due to defective. Using post insulator in higher voltage is not economical and suspension type insulator is evolved. This is because of the capacitances formed between the metal parts of the insulators and tower structure.
The following points may be noted regarding the potential distribution over string of suspension insulators. Voltage distribution over suspension insulator string efficiency. First of all thanks for visiting electrical engineering info now let us discuss p otential distribution in a string of suspension insulators. Potential distribution over a suspension insulator string.
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. They are used to provide support to the conductors and to. Several experimental and simulation methods have been developed for the computation of electric fields and potentials along an insulator string 4. The effect of stray capacitance over voltage distribution the presence of stray capacitance causes unequal potential distribution over the string. String efficiency of suspension insulator when the voltage is applied across the suspension insulator string, it is unequally distributed across the individual unit. On the top of the insulator the conductor bound into a groove,which is cemented on to a galvanized steel. Each insulator of a suspension string is called disc insulator because of their disc like shape. This unequal potential distribution is undesirable and is usually expressed in terms of string efficiency. String efficiency of suspension insulators and methods of improving. Due to the presence of shunt capacitor, the voltage across the suspension insulators does not distribute itself uniformly across the each disc. 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. Effects of disc insulator type and corona ring on electric. Each suspension disc is designed for normal voltage rating.
Measurement of voltage distribution on high voltage. Vph the phase voltage across the subsequent units measured from the ground respectively. However, there is a significant thing to be considered in case of these string insulators, known as string efficiency. 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. 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. Solved calculation of string efficiency for suspension. Pdf a set of models for investigation of voltage distribution along.
String efficiency conductor voltage nxvoltage across the disc nearest to conductor n number of discs in suspension insulator. In this article, we will be talking about voltage distribution and string efficiency of suspension insulator. The following points may be noted regarding the potential distribution over a string of suspension insulators. If a protective corona ring inserts capacitances from the line, with the link of the middle.
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