DD267361A1

DD267361A1 - PROCESS FOR SURFACE GLUING OF SPECIAL PAPERS

Info

Publication number: DD267361A1
Authority: DD
Publication date: 1992-05-07

Abstract

Ziel der Erfindung ist eine kostenguenstige Verringerung der Spannungsbeanspruchung beim Schalten von Wicklungen um die Lebensdauer der Isolierung zu erhoehen und Schaeden infolge schneller transienter Ueberspannungen zu vermeiden. Aufgabe der Erfindung ist eine wirksame Absenkung der Amplitude schneller transienter Spannungswellen durch Ueberspannungsableiter unter Beruecksichtigung des Restspannungsverhaltens der Ueberspannungsableiter. Erfindungsgemaess wird diese Aufgabe dadurch geloest, dass Kondensatoren und Ueberspannungsableiter parallelgeschaltet und in unmittelbarer Naehe des Schaltgeraetes zwischen Schaltgeraet und Wicklungseingang angeordnet sind.The aim of the invention is a cost-effective reduction of the voltage stress when switching windings to increase the life of the insulation and avoid damage as a result of rapid transient overvoltages. The object of the invention is an effective lowering of the amplitude of fast transient voltage waves by surge arresters, taking into account the residual voltage behavior of the surge arresters. According to the invention, this object is achieved in that capacitors and surge arresters are connected in parallel and are arranged in the immediate vicinity of the switching device between the switching device and the winding input.

Description

Durch die Schaltung wird die Röstspannung der Überspannungsableiter auf die Ansprechspannung abgesenkt. Es wird erreicht, daß am Schaltgerät installierte Ableiter in der gleichen Weise die Überspannung wirksam begrenzen wie bei ihrer Installation in unmittelbarer Motornähe. Die Tiefpaßwirkung des Motoranschlußkabels vergrößert die Stirnzeit der Überspannungswelle an den Eingangsklemmen der Ständcrwicklung. Es tritt keine Reflexion der Spannungswelle auf.By the circuit, the roasting voltage of the surge arrester is lowered to the response voltage. It is achieved that arresters installed on the switching device effectively limit the overvoltage in the same way as in their installation close to the motor. The low-pass effect of the motor connection cable increases the front time of the overvoltage wave at the input terminals of the stator winding. There is no reflection of the voltage wave.

Ausführungsbelsptel

Die Zeichnung zeigt das einphasige Ersatzschaltbild der erfindungsgemäßen Schaltungsanordnung. Ein 6-kV-Motor 5 ist über ein Anschlußkabel 4 und über einen Vakuumschalter 1 mit dem Netz verbunden. Kondensatoren 2 und Überspannungsableiter 3 sind in unmittelbarer Nähe des Schaltgerätes über ein 10m langes Kabel gegon Erde geschaltet. Zwischen der Schutzbeschaltung und dem Motor befindet sich ein 30m langes Kabel 4. Die installierte Kapazität beträgt 16OnF.The drawing shows the single-phase equivalent circuit diagram of the circuit arrangement according to the invention. A 6 kV motor 5 is connected via a connecting cable 4 and a vacuum switch 1 to the network. Capacitors 2 and surge arresters 3 are earthed in the immediate vicinity of the switching device via a 10m long cable. There is a 30m long cable between the suppressor and the motor. 4. The installed capacity is 16OnF.

Claims

Circuit arrangement for reducing the stress caused by rapid transient voltages when switching windings by using capacitors and surge arresters ^, characterized in that the capacitors (2) are connected in parallel to the surge arresters (3) and in the immediate vicinity of the switching device (1) between the switching device and the winding input (4 ) arranged sinri.

For this 1 page drawing

Field of application of the invention

The invention relates to a circuit arrangement for reducing the burden of rapid transient voltages when switching windings using capacitors and surge arresters.

Characteristic of the known state of the art

At a very high stress of windings by fast transient voltages destruction of the insulation, in particular of the input turns, the result.

A number of technical solutions are based on the fact that effective protection of the motor windings against fast transient voltage waves is only possible in the immediate vicinity of the input terminals of the motor. Thus, arrester circuits are arranged to limit the amplitude of the voltage waves in the immediate vicinity of the motor. It has been found that the residual voltage of these arresters, which consist of a series circuit of quench spark gap and Zinkoxidvaristoren, because of the inertia of the current flow through the varistors, especially in strains with fast fast transient voltage waves can be more than 1.5 times their Ansprechspannung. As a result, the voltage load, as a rule, increases inadmissibly by at least 50% with respect to the insulating capacity. In addition, the insulation is additionally charged high due to the high-frequency Ausgl'jichsvorganges during Ansprc- hens the quenching spark gap.

An accommodation of the surge arrester in the terminal box is impractical for thermal reasons. They are therefore connected to the winding via an additional cable of a few meters in length. However, this increases the voltage stress of the winding by about 1 kV per meter of cable with fast transient voltage waves. Furthermore, it is known to install capacitors with small capacitances to increase the rise time of the voltage wave in the immediate vicinity of the motor. However, this requires additional installation area and an electrical operating room, which represents additional expenses or is not available for retrofitting. R-C protection circuits installed directly in front of the input terminals and consisting of a resistance R matched to the supply line impedance and a capacitance blocking the high frequency AC voltage reduce the amplitude of the voltage stress to 50%, but do not generally prevent rapid transient voltage stresses. In addition, there is again the problem of installation near the winding. WP 238488 envisages a specially designed low-inductance capacitor whose capacitor pads are connected directly into the current path. This capacitor, housed in the terminal box, wears all the shaft ends and does not lead to a reduction in the phase-to-earth overvoltage.

In order to avoid multiple re-ignition when blanking with vacuum switching devices, according to WP158450 large capacities are installed via separate cables in the load-side network at a greater distance from the motor. These capacities change the course of the load-side transient paunting so that intersections of the transient voltage are excluded with the Wiederverfestlgungskennlinie the switching path and thus reignifications are avoided. This solution offers no protection against fast transient voltage waves that occur during pre-ignition switch-on processes. Moreover, this solution is not generally applicable because arc instabilities can lead to the creation of additional fast transient voltage waves due to the large capacitances connected via separate cables. This would create additional stresses on the winding. The response and residual voltage behavior of the surge arresters during switch-on is not affected.

Object of the invention

The aim of the invention is a cost-effective reduction of the voltage load be'rr switching windings in order to increase the life of the insulation and to avoid damage due to rapid transient overvoltages.

Explanation of the essence of the invention

The object of the invention is an effective lowering of the amplitude of fast transient voltage waves by superposing the residual voltage behavior of the surge arresters. Erfindungsgemäf.i this object is achieved in that capacitors and surge arresters are connected in parallel and arranged in the immediate vicinity of the switching device between the switching device and winding input.