DD220704B1 - CIRCUIT ARRANGEMENT FOR HIGH VOLTAGE MESSAGES - Google Patents

Description

For this 1 page drawing

Field of application of the invention

The invention relates to a circuit arrangement for a mixed Hochspannungsmeßteiler, with parallel circuit of ohmic resistance and capacity, with the various ratios for the measurement and registration of switching voltage and arc voltage curves can be adjusted during the testing of high-voltage circuit breakers in synthetic test circuits.

Characteristic of the known technical solutions

There are known Hochspannungsmeßteiler whose upper and lower voltage part each consist of a parallel connection of a capacitor and a resistance. In this case, the transmission ratio of Hochspannungsmeßteilers is constant on the low side by the parallel connection of a capacitor and an effective resistance or can be made variable by switching a plurality of such constructed parallel circuits of capacitance and ohmic resistance. The disadvantage of this solution is that on the low-voltage side of the high-voltage measuring very high capacitance values result, because for a linear voltage distribution along the Hochspannungsmeßteilers the capacity of the upper voltage side arranged capacitors can not be kept arbitrarily small, a variety of gear ratios are required and large translations of the Hochspannungsmeßteilers be needed. The increase in the capacitance values also results in a corresponding space requirement which can not be realized without considerable expense with regard to the spatial arrangement of the components in the undervoltage part of the high-voltage measuring divider. Also, the required transmission behavior with regard to high bandwidth and the behavior of the high-voltage measuring divider during voltage breakdown from the peak value of the switching voltage to be measured to zero can not be achieved. From GB PS 1112737 an ohmic high-voltage divider is known whose upper voltage part consists of a damping resistor and a resistive and whose undervoltage part in addition to a resistive this has a parallel ohmic voltage divider, which is dimensioned so that an adjustment of the total resistance of the high voltage divider to the lower side him connected measuring line with the wave impedance Z is reached. A disadvantage of this arrangement is the low-pass behavior of this Hochspannungsmeßteilers and the lack Möglickeit switching to different ratios.

In the DD-WP 100810 a mixed FV / C high voltage divider is also described with constant transmission ratio, the upper voltage part has a relation to the lower voltage part reduced time constant for the compensation of the low-pass behavior of the divider due to the inductance of its supply to the DUT in the frequency range of interest.

However, both arrangements do not meet the demanding transmission behavior in the measurement of switching voltages, especially in dielectric restrikes of high voltage switches and large Teilerübersetzungsverhältnissen. In the case of measuring switching voltages on high voltage switches, large divider ratios and the consequent large amounts of capacitor capacitance in the undervoltage section are required

for the transmission behavior to be demanded for a high inductance amount, there is a detuning of the ratio in the C branch of the high voltage divider, since the amounts of the inductances of the capacitors in the upper and lower voltage part do not correspond to the transmission ratio of the divider. The solutions mentioned thus do not offer the possibility of an inductance adjustment. The result is signal distortions at the divider output and changes in the transmission ratio of the divider in the range of high frequencies, especially in dielectric restrikes on high voltage switches after short circuit current shutdown with high voltage gradients.

Object of the invention

The aim of the invention is to eliminate the deficiencies of the prior art and to realize a Hochspannungsmeßteiler that allows a trouble-free and economical measurement of switching and arc voltages with a minimal amount of components in a space-saving design.

Explanation of the essence of the invention

The invention has for its object to propose a circuit arrangement for a Hochspannungsmeßteiler, with the various ratios can be set under the condition that the capacity of the capacitor in the undervoltage part in terms of value small and thus can be carried out to save space for each selectable gear ratio in achieving a high transmission bandwidth , The Hochspannungsmeßteiler invention consists of upper and lower voltage part, each having at least one parallel connection of ohmic resistors and capacitors, and a switch which is connected via a measuring line to the input resistance of an oscilloscope and with which the transmission ratio is changed by switching the lower voltage part. Furthermore, the high-voltage measuring divider has a common undervoltage partial capacitor. For undervoltage part capacitor mixed voltage dividers are connected in parallel via contacts of a first switch level of the switch, is connected to the voltage divider taps via contacts of a second switch level of the switch, the input resistance of the oscilloscope. The dimensioning of the voltage divider resistors R _a and Rb is performed such that the total resistance R ₃ + Rb // R2 is equal to the input resistance R ₂ . To achieve a large bandwidth capacitors are connected in parallel to the upper side arranged individual resistors of the ohmic voltage divider, which are designed by the amount by a factor of 10 ³ lower than the undervoltage part capacitor.

In an embodiment of the invention, a capacitor whose capacitance is equal to the capacitance of the measuring line to the oscilloscope is arranged at the output of the circuit arrangement. As a result, no influence on the transmission ratio of the high-voltage measuring device via measuring lines of different lengths. To protect the oscilloscope from any interference voltage spikes a varistor is arranged at the output of the circuit arrangement. The circuit arrangement according to the invention ensures that only one capacitor is used for all selectable gear ratios, which is designed for the setting of the smallest gear ratio. With this circuit arrangement, it is thus possible, with a constant bandwidth and low component cost, in particular by the use of capacitors of small capacity, whose inductive component is also low, each set according to the interpretation possible ratio. This results in small spatial dimensions that allow a housing in a shielding housing, which has ground potential. This shielding housing enables the use of the bypass technique with the aid of a double-shielded coaxial cable to suppress interference signals.

embodiment

The invention will be explained below with reference to an exemplary embodiment. The accompanying drawing shows:

Fig. 1: Circuit arrangement for a mixed Hochspannungsmeßteiler, consisting of upper and lower voltage part.

The high-voltage divider according to the invention has a high voltage part, which consists of the capacitor C ₁ and the resistor R ₁ , and an undervoltage part, with the various ratios can be set and to the over a double-shielded acting as a measuring line M RF coaxial line of the oscilloscope Os for registration the measuring signal is connected. The transmission ratio can be changed by means of a switch S, which has a first switching level S ₃ and a second switching level S _b . The first and second switching levels of the switch S each have a plurality of contacts S _a 4bisS _a3 and S _b4 bisS _b8 . The gear ratios are adjustable in steps of Ü = 10 ³ ... 10 ⁵ and can be extended to larger gear ratios. For the smallest transmission ratio U = 10 ³ , the low voltage partial capacitor Сз, whose capacitance moves in дР-Вегеісгі, forms with the input resistance R _{2 of} the oscilloscope the RC parallel connection of the low voltage part of the high voltage divider. In order to select larger transmission ratios to the lower voltage part capacitor C ₃ ohmic voltage divider R4; R5; R6i R7. consisting of the individual resistors R ₄₃ , R _4b ; Rs ₃ ; Rs _b ; R6a- ^ вь or R _7a, R composed _7b and their amounts to the amount of the input resistance R ₂ of the oscilloscope Os are equal, connected in parallel, the input resistance R ₂ to the respective measuring pickoff of the ohmic voltage divider R _4, R _6, R ₆ , R _{7 is} parallel. As a result, the time constant of the undervoltage part of the high-voltage measuring divider remains constant at each ratio stage. For a good transmission behavior of the circuit arrangement according to the invention at high bandwidth, a capacitor C _{2 is} arranged at the output of the circuit arrangement, which is of the order of magnitude of the capacitance of the RF coaxial line designed as measuring line M, compensates for differences in the Meßleitungslänge and depending on selektählem

Ratio of the individual resistors R ₄ b, ^ ъы Рвь / ^ Ьь connected in parallel. The individual resistors R _4a , R _5a , R _6a , R _{7a of} the ohmic voltage divider R ₄ , R ₅ , R ₆ , R ₇ are capacitors C ₄ , C ₅ , Ce, C ₇ connected in parallel, so that the time constants of the connected ohmic voltage divider to the high voltage side and the Meßabgriff are the same. The capacitors C ₄ , C ₅ , C ₆ , C ₇ are capacitively in the nF range and thus by a factor of 10 ³ below the capacity of the capacitor C _3rd To protect the oscilloscope against possible interference voltage peaks, a varistor R _{3 is} arranged at the output of the circuit arrangement.

Claims (3)

1. Circuit arrangement for a mixed Hochspannungsmeßteiler consisting of upper and lower voltage part, each having at least one parallel connection of ohmic resistors and capacitors, further consisting of a switch which is connected via a measuring line to the input resistance of a Oszillograph and with the by switching the Undervoltage part, the transmission ratio is variable, as well as from an undervoltage part capacitor, characterized in that the lower voltage part capacitor (C ₃ ) via contacts (S _a4 , S _a5 , S _a6 , ...) a first switch level (S ₃ ) of the switch (S) mixed Voltage divider (R ₄ , R ₅ , R ₆ , ...) are connected in parallel, at the voltage divider taps via contacts (S _b 4, S _b 5, Sb6, · · ·) a second switch level (S _b ) of the switch (S ) in a conventional manner, the input resistance (R ₂ ) of the oscilloscope (Os) is connected and die'Dimensionierung the voltage steeper resistors (R _a and R _b ) is such that the total resistance (R _a + R _b // R2> is equal to the input resistance (R ₂ ) and that the capacitance of the capacitors (C ₄ , C ₅ , C ₆ , .. .) The mixed voltage divider by a factor of 10 ^{3 is} lower than the capacity of the undervoltage sub-capacitor (C ₃ ). 2. A circuit arrangement for a mixed Hochspannungsmeßteiler according to claim 1, characterized in that to compensate for different Meßleitungskapazitäten at the output of the circuit arrangement, a capacitor (C ₂ ) is arranged, whose capacity is equal to the capacity of the measuring line (M). 3. Circuit arrangement for a mixed Hochspannungsmeßteiler according to claim 1 and 2, characterized in that at the output of the circuit arrangement, a varistor (R ₃ ) is arranged.