DE3009997A1 - Voltage limited active capacitive voltages divider - has varistor limiters in parallel with earth connected auxiliary capacitors - Google Patents

Abstract

The active capacitive potential divider has an overvoltage capacitor (1) connected via a cable from the pick-off side electrode (5) to an under voltage capacitor (12) in the reverse feedback circuit of an amplifier (11). It is a simply constructed circuit which extracts a measurement parameter accurately proportional to a high voltage. The pick-off side electrode (5) of the overvoltage capacitor is connected to earth via an additional capacitor (16). The input (10) of the amplifier is also connected to earth via a further auxiliary capacitor (19). One or both auxiliary capacitors are connected in parallel with a semiconductor arrangement (17,20) which performs a limiting function. The limiting semiconductor arrangement consists of a varistor. The arrangement eliminates the danger of damage by an excess voltage at relatively low cost.

Description

Active capacitive voltage divider

The invention relates to an active capacitive voltage divider with a high voltage capacitor, which with its tap-side electrode over a connection line is connected to an undervoltage capacitor, the is arranged in the negative feedback branch of an amplifier. Such an active capacitive Voltage divider is in the magazine "Smit Mededelingen" 24 (1969) 4, page 229 described.

With such a capacitive voltage divider, small Structure and line inductances are already very high voltage drops when the high voltage to be detected by means of the voltage divider is relatively high Experiences changes at a relatively high rate of change. Such conditions occur in medium and high voltage switchgear, especially in SF6-insulated ones systems, operationally when operating disconnectors and circuit breakers on; This applies in particular to systems with vacuum switches. Also result such voltage conditions in the event of a fault in the event of short circuits. The described Changes in the high voltage lead to large changes in the current over time the capacitive voltage divider, which leads to very high overvoltages due to its inductances can lead.

These overvoltages not only endanger the isolation of the tap side Electrode of the high-voltage capacitor, but also the one that may be present Insulation of a bushing for the tap-side end of the high-voltage capacitor and the isolation the connection line to the amplifier. This can be inadmissibly overdriven or even destroyed, and any existing ones Intermediate transformers can become saturated. This is the detection or monitoring the high voltage is no longer guaranteed.

To counteract this, it is already known ("Electrical Review" Vol. 198, 21, pages 31 to 33), into the connection line between the high-voltage capacitor and the amplifier one-step filter.

However, this results in restrictions in the frequency bandwidth, and it becomes the frequency dependence and the angle error of the active capacitive Voltage divider changed disadvantageously.

The invention is based on the object of an active capacitive To propose a voltage divider that is relatively simple and yet the acquisition of a high-voltage-proportional measured variable that allows a true Represents image of high voltage.

The solution to this problem is with an active capacitive voltage divider of the type specified at the outset, according to the invention, the tap-side electrode of the high-voltage capacitor Connected to earth potential via an additional capacitor.

The voltage divider according to the invention has the advantage that on the tap side Electrode of the high-voltage capacitor, the overvoltages that occur are reduced, so that there is a risk to the insulation of the high-voltage capacitor and possibly existing implementation for the tap-side end of this capacitor and also the insulation of the connection line is not endangered. The additional capacitor has no influence on the transmission behavior of the according to the invention Voltage divider, because there are capacities in the area of the connection line are practically without significant influence on the accuracy of the voltage divider.

It is also considered advantageous if the input of the amplifier is connected to ground potential via another additional condenser. This one more Additional capacitor supports one additional capacitor in its effect.

The voltage divider according to the invention is advantageously the one and / or the further additional capacitor is a semiconductor arrangement with a limiter effect connected in parallel. This semiconductor arrangement preferably consists of a varistor; however, it can also consist, for example, of Zener diodes connected in anti-parallel. The semiconductor arrangement is advantageous with regard to its limiting effect designed in such a way that they can only be traced back to extraordinary processes Overvoltage responds, including a breakdown in the high-voltage capacitor or a disconnection of the connection line is understood.

To explain the invention is in the figure in a schematic representation an embodiment of the active capacitive voltage divider according to the invention shown.

The capacitive voltage divider shown contains a high voltage capacitor 1, which in the embodiment shown in a metal capsule 2 is otherwise Metal-enclosed high-voltage switchgear 3, not shown further is. The high-voltage capacitor 1 is connected to a high-voltage connection 4 guided, which in the exemplary embodiment shown is the inner conductor of the high-voltage switchgear 3 acts. The tap-side electrode 5 of the high-voltage capacitor 1 is huber a connecting line 6 led out of the metal capsule 2; for this purpose is An opening 7 with a passage 8 is provided in the metal capsule 2.

The tap-side electrode 5 is connected via a connecting line 9 of the high-voltage capacitor 1 is connected to an input 10 of an amplifier 11. The amplifier 11 contains an undervoltage capacitor in its negative feedback branch 12. At the output 13 of the amplifier 11, a voltage U2 can be tapped, that of the high voltage U1 between the high-voltage connection 4 and the metal capsule which is earthed via a line 14 2 is proportional.

The earth-side tap 5 of the high-voltage capacitor 1 or the The beginning 15 of the connecting line 9 is connected to ground via an additional capacitor 16. The additional capacitor 16, a semiconductor arrangement 17 is connected in parallel, the consists of a varistor 18 in the illustrated embodiment.

The input 10 of the amplifier 11 is via a further additional capacitor 19 also connected to earth potential; him is another semiconductor arrangement 20 connected in parallel, which in the illustrated embodiment from a further Varistor 21 is made.

With the invention, an active capacitive voltage divider is proposed, in which there is a risk of overvoltages by means of a comparatively low additional circuit complexity is avoided, with the additional circuit complexity an impairment Impairment of the transmission accuracy of the capacitive Voltage divider is largely excluded.

4 claims 1 figure

Claims (3)

Claims: reactive capacitive voltage divider with a High-voltage capacitor, which is connected to its tap-side electrode via a connection line is connected to an undervoltage capacitor in the negative feedback branch an amplifier is arranged, d u r c h e k e n n n z e i c h n e t that the tap-side electrode (5) of the high-voltage capacitor (1) via an additional capacitor (16) is connected to earth potential. 2. Voltage divider according to claim 1, d a d u r c h g e k e n n z e i c h n et that the input (10) of the amplifier (11) via a further additional capacitor (19) is connected to earth potential. 3. Voltage divider according to claim 1 or 2 d a d u r c h g e k e n n z e i c h n e t, daX one and / or the other additional capacitor (16; 19) a semiconductor arrangement (17; 20) is connected in parallel with a limiter effect. 4, voltage divider according to claim 3, d a d u r c h g e k e n n z e i c h n e t that the semiconductor arrangement (17) consists of a varistor (18).