DE1952582A1 - Circuit arrangement for protecting an electrical high-voltage circuit against overload - Google Patents

Description

Circuit arrangement for the protection of an electrical high-voltage circuit against overload.

The invention relates to a circuit arrangement for protection an electrical heavy current circuit against overload, with a device for generating one of the current flow in the Power circuit dependent DC voltage that controls the potential of a time-determining cone generator that controls the Triggers the activity of a protective circuit, whereby the operating energy for the protective circuit is taken from a memory.

In the electrical industry, it often proves to be necessary dig to measure the current flowing in a power circuit and provide a protective effect if the current exceeds a predetermined value. For example, it may be necessary to either give a warning signal or one Trip circuit breaker. The necessary measurement is usually performed on a time / current basis because the The speed required for the protective effect is very high depends essentially on the size of the overload.

009817/0486

Conventional devices for this purpose can consist of directly actuated overload devices, which either go directly into the power line or powered by current transformers or relays of the magnetic induction type. Although this is in Light circuits can be carried out, requires the protection of power circuits either to be inserted in the power line, expensive direct current coils or large current transformers. "In high-voltage distribution systems, for example, the Current transformer connected directly to the line and thus for the full voltage, as the protective effect is brought about on the low voltage side. Such current transformers are P bulky and expensive because they are sufficient for the protective effect itself Have to deliver energy. As an alternative, it is therefore possible to use a smaller current transformer that only reduces the overload accepts and the protective device transmits a signal, with the energy necessary for operation of a separate Source, e.g. taken from a stationary battery. This in turn has considerable disadvantages, since such systems are frequent are in remote locations and large and expensive batteries are required to avoid frequent maintenance.

In a circuit arrangement of the type mentioned at the outset, the device for generating the DC voltage is according to the invention connected to the memory in order to load it.

This has the advantage that the device for generating the DC voltage, which is dependent on the current flowing in the power circuit, which preferably consists of a current transformer with a downstream rectifier, can be made very small, and that, in addition, the memory, which is expediently a secondary battery, can be correspondingly small because it is powered by electricity from the current transformer or other device is maintained in a charged state. Such a circuit arrangement can therefore work safely over long periods of time without maintenance, and the battery or some other type of memory only needs to have a capacity that is sufficient to operate the protective circuit sufficient. , - ^

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A circuit arrangement according to the invention can have two types of delay work. So the time delay in the operation of the protective circuit can be the reciprocal of that in the power circuit to be proportional to the flowing strokes, and for this purpose the time-determining capacitor part of a voltage-reciprocal charging circuit. Such a working circuit is called the reverse, certain minimum time switching (IDMT system) usually denotes ο

In the case of an alternative system - usually as a double or triple, specific minimum time switching (DDMT or TDMT system) - are two or more specific time delays provided, each of which is selected as a puncture of the permissible current flowing in the power circuit. With this bowl ' type of operation, two or more time-determining capacitors are required, which are connected in parallel circles, of which one the protection circuit as a result of one above a minimum value can trigger during a predetermined time flowing current. In practice, these circles are set in such a way that that one on a combination of a relatively high current and one responds to a shorter time while the other responds to a combination of a lower current and a longer time. · ...-. · -. "

The invention is explained below on the basis of exemplary embodiments and the drawing explained in more detail.

Fig. 1 is a block diagram of an inverted particular mini circuit; ,,

Fig. 2 and 5, .are Diagr amme _x , which the characteristics of the switching ■ v-. - .-; .-: tung ^ nachvFig, 1 showjai, ._. . _,

Fig, A; is a block scherna ^ · a double, definite. Minimum: _-: -. ^ circuit; _{,, ν Ύ}

Fig. 5 is a diagram showing the characteristics of the circuit of Fig. K. . :. '

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The one in Pig. The circuit arrangement shown in FIG. 1 is intended to protect a power circuit which is formed from a conductor 1 enclosed by a current transformer 2. The output voltage of the current transformer is thus proportional to the current flowing in the power circuit, and the flowing current is rectified in a rectifier circuit J. In addition to rectifying the current, this circuit distributes the current between a memory K, which can be a secondary battery or a large capacitor, for example, and a time-determining circuit 5 the voltage exceeds a value which is predetermined by setting the circuit 6 and corresponds to the value of the current in the conductor 1, above which a protective effect may be necessary.

The time-determining circuit 5 contains a time-determining capacitor which is charged by the memory 4 as a function of the voltage signal received from the current transformer 2. Thus it works to generate a delay which is proportional to the reciprocal of the charging voltage, ie proportional to the reciprocal of the current in the conductor 1. The characteristics of this' circle are shown in FIGS. In Fig. 2 it is shown that for successive voltages in the range of an order of magnitude from V1 to V6 until a capacitor voltage VC, which is referred to as the triggering threshold, is reached, a time elapses which varies inversely with the magnitude of the voltage. In other words, the time at a charging voltage V2 is less than at a lower voltage V1, and the time gradually decreases up to a charging voltage V6. Since the. Charging voltage is proportional to the current flowing in the conductor 1, the time until the trigger value is reached can be plotted against the current, as shown in FIG. 3. Here you can see that the time until the triggering threshold is reached, ie the time delay, is proportional to the reciprocal of the stroke I. As already explained, the time-determining circle does not come into action at all until "Mihmäl- '""value of the current is exceeded, after which ^' the time-determining ¹ ^

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Capacitor is charged until the voltage crosses the trip level achieved.

This corresponds to the voltage required to operate a Trigger circuit 9 is necessary, which draws its energy from the memory 4 and sends a signal to a protection circuit Io, which is a mechanical / electrical release device and operates the circuit breaker and thus the circuit to the conductor 1 interrupts. The protection circuit Io contains a static switch, the energy from the memory 4 to operate a Release coil releases and thus interrupts the circuit to conductor 1. ·

It is therefore understandable that the current transformer 2 is only a very needs to supply small current in order to keep the memory 4 charged at its full voltage and also the necessary To supply electricity for the time-determining circuit. It can be there « a small current transformer can be used, and accordingly a small memory is sufficient to supply the for operation necessary energy, as it is kept in a constant state of charge by the current transformer »

The one in Pig. 4 essentially corresponds to the circuit arrangement shown those after Pig. 1 and matching items are given the same reference numerals. The only major difference is that instead of the time-determining circuit 5 has two separate delay circuits 12 and IJ are provided, the short and long time delays respectively revealed. The two circuits are connected in parallel to one another and connected to the trigger circuit 9. The characteristics these two circles are shown in Fig. 5 and with arrows. 12 and IJ. According to Fig. J5, the one in conductor 1 The flowing current is denoted by I, while t is the time up to Reaching the trigger threshold for the trigger circuit 9 represents. For the delay circuit 12 is at a relatively high value of the current I reaches the triggering threshold after a period of time t ^, these two values being adjustable, as by

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the arrows 14 and 15 are indicated »The delay circle has such a characteristic that a considerably smaller one Current value of Γ the time-determining capacitor to a voltage corresponding to the triggering threshold after a longer period Duration tp charges, taking the relevant values of current and time are adjustable, as indicated by arrows 16 and 17. When the timing capacitor is in one of the charged both delay circuits 12 and IJ to a value which corresponds to the triggering threshold, the trigger circuit 9 is actuated as described above and provides a signal ^ the protection circle Io, in order to bring about the necessary protective effect- ™ lead, for which the necessary power is taken from the memory 4 »

Although the circuit arrangement shown in Figure 4 _e opposite that of the Pig. I has different operating characteristics, but it has the same advantages in that both the current transformer 2 and the memory 4 can be made considerably smaller and cheaper than in known circuit arrangements. Although both circuit arrangements show a current transformer for generating a voltage that depends on the current flowing in the power circuit, the necessary voltage can also be eifcalten by tapping the ψ voltage drop between two points in the power circuit that are at a distance from each other .

Patent claims:

9817/0486

Claims (7)

P ate η ta η s ρ r ü cha: Circuit arrangement for protecting an electrical high-voltage circuit against overload, with a device for generating a direct voltage which is dependent on the current flow in the high-voltage circuit and which controls the potential of a time-determining capacitor that triggers the activity of a protective circuit, with the operating energy for the protective circuit being stored in a memory is removed, characterized in that the device (2, 3) for generating the direct voltage is also connected to the memory "( ¹ I-) in order to charge it, 2. Circuit arrangement according to claim 1, characterized in that the device (2, 3) for generating the direct voltage ρ consists of a current transformer (2) with a downstream rectifier (3) 3 circuit arrangement according to claim 1 or 2, characterized in that that the protection circuit (lo) operated a circuit breaker 4. "Circuit arrangement according to claim 1 to 3, characterized in that the memory (4) is a secondary battery, that of the device (2, 3) for generating the direct voltage is fed in continuous charge. 5ο circuit arrangement according to claim 1 to 3 »characterized in that that the memory (4) is a capacitor. .6 ", circuit arrangement according to claims 1 to 5, characterized by a time-determining circuit (5) with a time-determining capacitor. 7. Circuit arrangement according to Claim 1 to 5, characterized in that that one time-determining capacitor in two 00-981 7 / Q4.8 6 *,, .., ■ delay circuits (12 / ljj) connected in parallel are provided is that each of the delay circuits as a result of one above a minimum value during a predetermined Time flowing current can trigger the protection circuit (lo), with one of the delay circuits on a combination a higher current and a shorter time responds than that assigned to the other delay circuit Combination. 0 0 9 8 1 7/0486 Blank page