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