EP1037232B1 - High-tension switchgear with at least two vacuum switches connected in series for operating the high-tension switchgear - Google Patents

Description

The invention relates to a high-voltage switching device with series connection of at least two vacuum interrupters according to the preamble of claim 1 and to a method for operating the high-voltage switching device. The invention can be used for example in gas-insulated switchgear. The term "high voltage" in this context means the voltage range above 1000 V.

In high voltage switching devices, the series arrangement of vacuum interrupters is applied in special cases on the basis of two basic principles, in an uncontrolled design according to H. Fink, E. Sonnenschein, SF6-isolated 52 kV medium voltage switchgear with vacuum switch, etz, Vol. 115 (1994 ) H. 11, pp 622-626 and using control capacitors. The uncontrolled design focuses on the use of the vacuum switching principle in voltage levels above 36 kV, realized by a series arrangement of two vacuum interrupters (standard chambers) limited to the rated voltage of 36 kV. From an economic point of view, an unavoidable taxation due to scattering phenomena (stray capacitances) becomes possible with regard to the potential distribution accepted. The design of the series arrangement must therefore be carried out according to the most heavily loaded vacuum interrupter chamber due to the inhomogeneous stress distribution, while the other vacuum interrupter chamber is exposed to a lower voltage stress and thus is not optimally utilized.

An example of a series arrangement of two vacuum interrupters with control capacitors is the use in the traction power supply with a frequency of 16 2/3 Hz. Compared to the arc times of 10 ms / 8.3 ms occurring at 50 Hz / 60 Hz, the contact paths are claimed 16 2/3 Hz with arc times of 30 ms. The associated comparatively high thermal stress and the resulting greatly increased burnup leads to a strong reduction in the dielectric strength in the off-state. This effect is counteracted by applying for rated voltages of e.g. 17.5 kV two vacuum interrupters connected in series and additionally taxed capacitively.

The previous design of series arrangements of two or more vacuum interrupters basically requires the use of similar interrupters, which are switched on and off simultaneously.

The integration of the series arrangement of two vacuum interrupters as the heart of a high-voltage switching device requires a capacitive control especially when used within a gas-insulated switchgear. The background of this measure is a linearization of the voltage distribution over the two vacuum interrupters, although the control capacities can adversely affect the extinguishing capability, as described in T. Betz, D. Koenig, Influence of grading capacitors on the breaking capability of two vacuum circuit breakers in series, IEEE 18 th Int. Symp. On Discharges and Electrical Insulation in Vacuum, pp. 679-683, Eindhoven, The Netherlands, August 17-21, 1998.

Document US 3 708 638 shows a high voltage switching device according to the preamble of claim 1.

The invention has for its object to provide a high-voltage switching device with series connection of at least two vacuum interrupters of the type mentioned, which is optimally loaded with respect to the voltage load. there the listed measures should ensure that the series arrangement to compensate depending on the geometry, use and environmental conditions differently precipitating influences on the turn-off without having to control the outside with the help of control capacitors rigid.

Furthermore, a method for operating the high-voltage switching device should be specified.

This object is achieved with respect to the high-voltage switching device in conjunction with the features of the preamble according to the invention by the features specified in the characterizing part of claim 1.

The object is achieved with respect to the method for operating the high-voltage switching device by the features specified in claim 4.

The achievable with the present invention consist in particular in that the voltage distribution is achieved on the basis of a natural, exclusively influenced by the intrinsic and stray capacitive voltage distribution and without additional control capacity. This eliminates the resulting during re-ignition and re-ignition of a vacuum interrupter and the control capacity flowing equalizing currents whose amplitudes increase with increasing control capacity, thus leading to a heating of the contact pieces of the vacuum interrupters and finally reduce the breaking capacity.

A particular advantage is the ability to solve the task of mastering switching cases (Kurzschlussausschaltvermögen, Einschaltvermögen) regardless of the task of mastering the dielectric requirements by a suitable choice of vacuum interrupters.

By additional measures on the drive unit, the arc behavior can be directly influenced and thus allows the introduction of a separate degree of freedom for the interpretation of both the dielectric behavior and the turn-off behavior under arc influence.

The proposed measures lead by combining different vacuum interrupters with different size (different nominal voltage, different breaking current) and / or different contact piece design (different contact piece diameter, different contact spacing of the contact pieces, different contact piece types) and generally different self-capacitance to different arc behavior. Through targeted use of this effect, the design diversity for controlling the individual cases of switching in comparison to known arrangements is significantly increased. If, for example, two suitable different vacuum interrupters with different contact piece diameters are used in series, the different inherent capacities of the vacuum interrupters and the different arc behavior can advantageously be combined with the aim of increasing the switching capacity.

Background of the use of series circuits of vacuum interrupters is the desire to use both the technical advantages of the vacuum circuit breaker in the form of a high di / dt and du / dt breaking capacity (di / dt = current gradient, du / dt = voltage slope) as well as the economic benefits such as freedom from maintenance, low drive energy and compact design. These advantages occur in a pronounced form especially in vacuum switching chambers with small contact distances of the contact pieces and can be used by connecting two or more vacuum switching chambers and thus switching distances to the effect that vacuum switching chambers beyond the 36 kV voltage range also come at higher nominal voltages used. This results in possible alternatives to the sulfur hexafluoride (SF6) extinguishing medium, which has hitherto dominated the voltage range above 36 kV, and which is also of environmental interest.

Further advantages will be apparent from the following description.

Advantageous embodiments of the invention are characterized in the subclaims.

Fig.1

ein Prinzipschaltbild der Serienschaltung von Vakuumschaltkammern für Hochspannungsschaltgeräte,

Fig. 2

ein vereinfachtes Ersatzschaltbild zur Potentialaufteilung,

Fig. 3

ein Spannungs/Zeit-Diagramm zur Erläuterung des Phänomens einer Spannungsübernahme durch eine Vakuumschaltkammer bei einer Wiederzündung der weiteren Vakuumschaltkammer.

The invention will be explained below with reference to the embodiments illustrated in the drawings. Show it:

Fig.1

a block diagram of the series connection of vacuum interrupters for high voltage switching devices,

Fig. 2

a simplified equivalent circuit for potential distribution,

Fig. 3

a voltage / time diagram for explaining the phenomenon of a voltage transfer by a vacuum interrupter chamber at a re-ignition of the other vacuum interrupter chamber.

A high voltage switchgear has two main tasks to deal with. On the one hand, it must withstand the dielectric stresses with open contacts, on the other hand, the thermal and mechanical effects in the elimination of a short-circuit arc dominate and resist after successful deletion of this short-circuit current of the recurrent voltage in the form of a transient transient. The associated period of time extends over several 100 microseconds and, in the case of the arrangement in series, is demonstrably characterized by the choice of the capacitive circuitry and the plasma events inside the switching chamber. A targeted influence on the transient processes following the end of the arc period should be achieved by different design of the vacuum interrupters and the contact pieces, by measures on the drive and by using different arc characteristics.
In this case, the ability of a series circuit should be particularly exploited that in the case of re-ignition of a switching chamber, the unaffected switching chamber can take over the entire voltage stress. This is referred to below as a takeover process and represents a particular advantage for the capacitive switching to control reignitions.

In Fig. 1 is a block diagram of the series circuit of vacuum interrupters for high voltage switching devices using the example of a Schalterpols shown. A first vacuum switching chamber 1 and a second vacuum switching chamber 2 are connected in series between a high-voltage side terminal 3 and a ground-side terminal 4. Between the common connection point 5 of both vacuum switching chambers 1, 2 and the ground-side terminal 4 occurs to be considered stray capacitance Cst.

FIG. 2 shows a simplified equivalent circuit for potential distribution. As can be seen, the self-capacitance CE1 of the first vacuum switching chamber 1 is in series with the parallel circuit formed of the self-capacitance CE2 of the second vacuum interrupter chamber 2 and the stray capacitance Cst. Both in FIG. 1 and in FIG. 2, the partial transient voltage U1 at the first vacuum interrupter chamber 1, the partial transient voltage U2 at the second vacuum interrupter chamber 2 and the total transient voltage U3 = U1 + U2 are indicated.

The invention is based on the principle of a series arrangement of two or more different vacuum interrupters 1, 2 as the heart of a high voltage switching device. By using different types of vacuum switch chambers within a switch pole, both the inherent capacitances and the arc behavior of the two different vacuum interrupters can be advantageously combined with regard to the voltage stress and the extinction capability of the series arrangement.

A special feature of the invention is the design of the high voltage side terminal 3 lying first vacuum interrupter chamber 1 with a larger contact piece diameter and thus an increased self-capacitance CE1. In contrast, the second vacuum switching chamber 2 connected to the ground-side terminal 4 has a comparatively smaller contact piece diameter with correspondingly comparatively lower inherent capacitance CE2, but is supplemented in the installed state by the stray capacitance Cst effective against ground potential. If appropriate Choice of the vacuum switch chamber types, therefore, this influence of the stray capacitances can be minimized or completely eliminated. The condition for this is: $$\mathrm{<figure-callout\; id="1"\; label="CE"\; filenames="imgf0001.png"\; state="\{\{state\}\}">CE</figure-callout>}1\cong \mathrm{<figure-callout\; id="2"\; label="CE"\; filenames="imgf0001.png"\; state="\{\{state\}\}">CE</figure-callout>}2+\mathrm{cst},$$

The compensation of the effective stray capacitances by a suitable choice of the inherent capacitances of the vacuum switch chambers results in a linearization of the potential distribution of an uncontrolled switch pole, which is particularly advantageous when using the high-voltage switchgear in a gas-insulated switchgear, since in this case higher stray capacitances become effective.

Another advantage of the series arrangement of at least two vacuum interrupters 1, 2 is that a re-ignition of a vacuum interrupter chamber does not necessarily lead to the re-ignition of the entire switch pole. This is due to the time of reclosure far advanced dielectric strength of the unaffected switching chamber. Especially in the case of capacitive switching, due to the appropriate selection of the series-connected, different vacuum interrupters results in the optimized ability of the voltage pickup.

A different arc behavior can be enforced by staggered opening of the contacts of at least two vacuum interrupters. In a series circuit consisting of two vacuum interrupters, both the contacts of the upper vacuum interrupter chamber 1 and the lower vacuum interrupter chamber 2 can be opened with a time delay. In case of staggered switching on and off of the vacuum interrupters 1, 2 results in a desired manner a targeted distribution of the switching stress on both vacuum interrupters, expressed by the adjusting by this measure at the respective vacuum interrupter proportion of recurring after a switching voltage. Furthermore, in the case of time-shifted switching on and off of the vacuum interrupters 1, 2, the voltage distribution in the case of pure dielectric voltage stresses can be influenced in the desired favorable manner.

Multiple reignifications, which occur predominantly at small contact distances at the upper vacuum interrupter chamber 1, have a conditioning effect on the extinguishing behavior of the lower vacuum interrupter chamber 2 and lead to an increase in the dielectric strength in comparison to an arrangement with only one vacuum interrupter chamber.

As a special feature of a series arrangement of at least two vacuum interrupters results specifically for the capacitive switching the advantage that re-ignition and re-ignitions of a vacuum interrupter chamber of the other vacuum interrupter chamber (or more other vacuum interrupters) are controlled. This is not so much the retrofitting of the vacuum switching principle to achieve higher rated voltages in the foreground, but the use of the technical advantages of a series arrangement of at least two vacuum interrupters for a special switching case, based on the usually required in the 36 kV voltage range rated voltage already from a single vacuum switching chamber could be controlled.

In Fig. 3 for this purpose, a voltage / time diagram for explaining the phenomenon of a voltage transfer by a vacuum interrupter chamber at a re-ignition of the further vacuum interrupter chamber is shown. It is the course of the transient voltages U as a function of time t to recognize. At time 0, the mains voltage recurring after successful arc quenching begins in the form of a transient transient voltage U3. About the series arrangement, the dotted Total injured voltage divides U3 so that a dash-dotted Teileinschwingspannung U1 and a Teileinschwingspannung U2 (solid line) is formed. At time t1, reignition occurs at the first (upper) vacuum switching chamber 1. The second (lower) vacuum interrupter chamber 2 takes over the entire voltage stress at this point in time t1, ie the total transient voltage U3 effective at this point in time. Subsequently, the upper vacuum interrupter chamber 1 solidifies and can again assume a small proportion of the total voltage U3.

The switch-off behavior of the series connection can be attributed to the singular behavior of the individual vacuum interrupters, taking into account the potential distribution. The potential distribution is determined in the first microsecond of the transient voltage due to effects of the post-current arc by ohmic (plasma) resistors, which describe the process of reconsolidation within the switching path. After a few microseconds, this plasma resistance has already grown so much that the intrinsic and stray capacitances determine the voltage distribution over both switching paths. The voltage distribution is significantly influenced by the stray capacitance Cst of the (lower) vacuum interrupter chamber 2 to earth, d. H. the stray capacitance Cst acts in the sense of a precontrol (but without the disadvantages explained above).

Claims (5)

1. High-voltage switching device having at least two series-connected vacuum switching chambers, with the vacuum switching chambers (1, 2), which are arranged in series, being designed differently with regard to their physical size and/or contact arrangement, such as the contact diameters, the separation between the contacts, and the contact types, with at least one vacuum switching chamber of a first type being provided, and at least one vacuum switching chamber of a second type being provided, and with the vacuum switching chambers (1, 2) being selected in such a manner that reignitions and restrikes of a vacuum switching chamber of the first type are coped with by at least one other vacuum switching chamber of the second type, with the vacuum switching chamber (1) which is connected to the connection (3) on the high-voltage side having a greater intrinsic capacitance (CE1) than the vacuum switching chamber (2) which is connected to the connection (4) on the earth side, characterized in that the sum of the intrinsic capacitance (CE2) of the vacuum switching chamber (2) which is connected to the connection (4) on the earth side and the stray capacitance (Cst) that acts to earth potential is approximately equal to the intrinsic capacitance (CE1) of the vacuum switching chamber (1) which is connected to the connection (3) on the high-voltage side.
2. High-voltage switching device according to one of the preceding claims, characterized by installation in a gas-insulated switchgear assembly.
3. High-voltage switching device according to one of the preceding claims, characterized in that the insulation between the quenching chamber and the enclosure is produced by SF6, N2, air or some other gaseous or liquid dielectrics.
4. Method for operation of the high-voltage switching device according to Claim 1, characterized by the contacts of at least two vacuum switching chambers (1, 2) opening at different times.
5. Method according to Claim 4, characterized in that the contacts of the vacuum switching chamber (1) which is connected to the connection (3) on the high-voltage side are opened with a time delay.

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