FI105855B - Voltage divider for insulation structure - Google Patents

Description

105855 Voltage divider for insulator structure The invention relates to a voltage divider for insulator structure according to the preamble of claim 1.

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According to the prior art, the phase voltage of the network in high, medium and low voltage distribution networks has been measured by means of a resistive voltage divider located in the insulators, where the phase voltage has been reduced to the intermediate level by measuring and shielding. Voltage splitters typically consist of a single high resistor formed by a high voltage resistor and one or more parallel lower resistors electrically connected in series therewith. In some cases, for example, in a 20 kV network, the upper resistor is formed of a few high voltage resistors, whereby the voltage acting over one resistor has been in the order of 2-3 kV.

• ·. 20 The disadvantage of prior art has been the high cost of high voltage resistors and the interference caused by other phases. • measurement errors and phase error in accurate measurements. In addition, mechanical stress caused by cast shrinkage and temperature changes in the resistor have caused, among other things, accuracy problems.

l .::. It is an object of the present invention to overcome the drawbacks of the above-described technology and to provide a completely new type of voltage divider for the insulator structure.

The invention is based on the fact that a voltage divider is formed by two nested series resistors,] which are, in one preferred embodiment of the invention, spiral voltage series resistors 35 connected in series.

More specifically, the voltage divider according to the invention is characterized in what is set forth in the characterizing part of claim 1.

The invention provides considerable advantages.

When voltage distribution is achieved with a sufficient number of series-connected resistor components, low-cost constant resistors with low voltage resistance can be used. Typically, these resistors may be, for example, constant resistors with a voltage of 500V. The transformer ratio of the divider can be easily adjusted exactly as desired by using parallel coupled resistors. For example, when applied to a resin, the voltage divider is not mechanically stressed due to the different thermal expansion coefficients of the resin and resistors. Reduction of mechanical stress improves tension strength and also reduces creep due to temperature variation. For example, a · ·. 20 Voltage divider achieves a good degree of insulation • · and high creep distance between the turns of the coil. The resistance value of a multiple resistor] '. T is more accurate than the accuracy of a single resistor, because the errors of individual "**. Resists partially overlap. Two t: \\\ 25 electrically parallel and physically nested divider- The use of an i:: 'element forms a linear variable electric field around the actual divider element used to measure, which minimizes the effect of stray capacitances.

• · · * · '* The second voltage divider also protects the measuring divider from interference.

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The invention will now be further explored by way of an exemplary embodiment of the accompanying drawings.

According to the figure, the measuring element of the voltage divider 2, 3 105855 according to the invention is arranged by way of example inside the tu-clamp 1. The voltage divider 2 consists of separate high resistance elements 5 and one or more low resistance elements 12 connected in series 5 to each other. At its ends, the voltage divider 2 is coupled to the upper electrode 7 in the phase voltage, which in turn is galvanically connected to the voltage bus 6 and, respectively, at its other end to the lower electrode 8, which is in the ground potential. Voltage is measured across one or more low resistors 1210 from terminals 9. A second resistor circuit 3, a shielding element, is coupled to and parallel to the voltage divider and acts as a coaxial shield against other phases and also reduces phase error. The shielding element also consists of separate resistor elements 4. The shielding element 3 is also coupled between the electrodes 7 and 8.

Mechanically, both resistor chains 2 and 3 can be wound around a suitable core 10 or 11 and then cast / ·. 20 resin inside. The massive resin structure is surrounded by a suitable shell structure which can also serve as a molding tin.

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Instead of resistor chains 2 and 3, for example, I * · Γ.Ι 25 suitable resistor films can be used.

t · · m. The divider can be used in a solid insulating structure as well as in gas or liquid. In gas or liquid insulation, the resistance structure must be rendered mechanically sufficiently rigid.

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The functions of the protection element 3 and the measurement element 2 can be • M t. ··. also replaces if a larger source of interference is inside the insulator, for example, if there is a grounded center tube inside the insulator. In this case, the inner element acts as a filtering element and the outer element acts as a filtering element.

The invention is applicable to support insulators and bushing insulators as well as other insulators and insulators of low, medium and high voltage ranges 5. The invention can also be used in the construction of various devices such as circuit breakers.

In experiments, a voltage divider of 100 to 10 resistors formed on a 24 kV support insulator has achieved an accuracy of better than 1%, with a temperature dependence of less than 0.1% in the temperature range 40 to 100 ° C.

Resistor chains consisting of individual resistors can be formed, for example, by soldering each resistor to one another.

According to the invention, the voltage distribution of the resistor chain can be implemented in such a way that the upper resistors are always in series and the lower resistors are formed either by a single resistor, · · · *, a series resistor connection or series and series *. • · · · to obtain the correct voltage distribution ratio.

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Within the inventive idea, a voltage divider can. be traditional, whereby the protection element consists of a resistor chain according to the invention.

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Claims (7)

105855 Voltage divider for an insulating structure (1) comprising a voltage divider (2) connected between the upper (7) and lower electrode 5 (8) - at least one upper resistor (5), - electrically connected thereto, at least one lower resistor (12) , and - in the vicinity of the voltage divider (2) from a shielding element (3) electrically connected thereto, to reduce interference, characterized in that the shielding element (3) has a helical structure. 4 · 4 20 • I I Voltage divider, p · P according to claim 1, characterized in that a protective element (3) is provided on the inner side of the voltage divider (2). • «• · · Voltage divider according to claim 1, characterized in that the voltage divider (2) has a protective element (3) on the inside and outside. ·· ♦ • · • · ι · «. Voltage divider according to claim 1, characterized in that both the voltage divider (2) and the protection element (3) are formed of separate resistor elements. Voltage divider according to claim 4, characterized in that the separate resistor elements 105855 are low-voltage components. Voltage divider according to claim 1, characterized in that the protection element (3) is a continuous resistor film structure. Voltage divider according to claim 1, characterized in that the voltage divider (2) is formed of several tens of low voltage resistors. • • • • • • • · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · • · • «• · · 1 ^ I e 105855