FI62599C - KOPPLING FOER MAETNING AV EN DEFEKTSTROEM OCH OEVERFOERING AV MAETINFORMATIONEN FRAON EN POTENTIALNIVAO TILL EN ANNAN - Google Patents

Description

[B] (11) ANNOUNCEMENT £ O C Q q

Jma al J '' utläggningsskrift oloyy C Patent granted 10 Cl 1933 Patent minkel «« v * ,, 3 ,, ..,., 3 G 01 R 15/02 // G. 01 R 19/165 (51) Kv. ik. /Int.ci. H 02 H 3/08, 7/16 SUO MI - Fl N LAN D (21) P »*« nttlh «k * mu · —PKmcaraeknint 783972 (22) HakamlspUvl - Ajw6knlngtdtf 22.12.78 ^ ^ (23) Alkuptivi — GIHI | h «tsdt {22.12.7 8 (41) Interpreters | ulklMktl - Bllvtt offantllg 23 q6 80 latent. J * r.ki.t «rlh.llltu. date_ - ‘

Patani och registerttyrclten λ Ans & kan uttafd och iitUkriften publlcermd ju.uy.o ^ (32) (33) (31) fyyd «** y * Tuo) k * u« - & «fird prltrtMt (71) Oy Nokia Ab, Pursimiehenkatu 29 -31, 00100 Helsinki 10, Finland-Finland (FI) (72) Pekka Johannes Ritamäki, Tampere, Finland-Finland (FI) (7 * 0 Oy Kolster Ab (5h) Connection for measuring fault current and transferring measurement information from one potential level to another - Koppling för mätning The present invention relates to a circuit for measuring a fault current, and in particular a direct current in high-voltage batteries, and for transferring measurement information from one potential level to another via an optical transmission path.

Such a connection is needed, for example, in high-voltage capacitor banks to detect a faulty capacitor which causes a rectifying current between different groups. By measuring the magnitude of this direct current, for example by means of a bridge connection, it is known how large an overvoltage acts over a faulty capacitor group.

The fault current is normally transferred to the ground potential by a current transformer, which must be dimensioned to withstand the voltages present in the battery. However, when going to high voltages, the price of transformers rises very sharply.

Another possibility is to use an optical signal transmission path. This solution, in turn, brings with it other cost factors, such as the need for a separate supply voltage source and protection of electronic components.

The object of the present invention is to eliminate the above-mentioned disadvantages and to provide a simple means for determining the current limit value and transferring the related information to another potential level.

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The invention is based on the idea that the current to be measured is used to generate the required operating power and that by properly dimensioning the small iron core auxiliary current transformer, the transformer becomes saturated with high currents and the components of the measuring circuits are easy to protect.

More specifically, the connection according to the invention is mainly characterized in that the connection comprises - an iron core current transformer through which the fault current is allowed to flow, - a rectifier connected in a manner known per se to the an emitting element (LED) connected to the output of the level detector, and - a resistor connected in a manner known per se to the input terminals of the secondary or level detector of the current transformer '.

It should be noted, however, that in defining the scope of protection, this patent specification and the accompanying drawing must be taken into account in their entirety, as required by the Patent Act.

The advantage of the connection according to the invention is that it does not need its own power supply and that it makes it possible to use a small and therefore cheap current transformer.

The invention will now be examined in more detail with the aid of the accompanying drawing.

Figure 1 shows one embodiment of a connection according to the invention as a schematic connection diagram.

Figure 2 shows the curves of the primary current, the secondary current and the current flowing through the light emitting member in the case of a normal fault current.

Figure 3 shows the curves of the corresponding currents under the influence of an exceptionally high fault current.

In the case of Figure 1, the rectifying current i? Passes through the saturable current transformer CT. At the normal primary currents i1, the current i2 flowing in the secondary of the current transformer proportionally follows the primary current and is converted to a voltage equal to the directional RF in the resistor R. This voltage is connected to a planar dimmer D, which is, for example, a thyristor with a zener diode. When this level detector D is operating, the secondary current i ^ passes through the LED of the semiconductor lamp. This emits light through the optical cable F to the ground potential. The light in the light transistor Q is converted back into an electrical signal.

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Figure 2 shows the waveforms of the primary current i ^, the secondary current ij and the semiconductor Lump LED current i ^ in the normal current ranges. In Fig. 3, the stallion basically shows the same currents in the event of a fault, in which case the primary current can be up to a thousand times higher than the normal measuring current. However, the current current I2 does not now follow the primary current i 1, even if the iron core 1C becomes saturated and the effective current i 1 is much smaller than would be required by the conversion ratio. In other words, a small iron core IC does not transmit high powers. However, for each semiconductor, the semiconductor lamp LED will illuminate and transmit information about the limit current being exceeded.

In the example case, the circuit is selected to alarm if the primary current i ^ exceeds IA, or to trip if the primary current exceeds 2A. When the current conversion ratio in the current transformer CT stallion is 10: 1 (rotation ratio 5:50), then the value of the secondary current is then 100 and. 200 mA.

The control resistor R is set so that the voltage acting over it in the above-mentioned case is e.g. 3V. Thus, when the voltage reaches this value, the parasite ιόν is released ± 2 partially through the level detector, presenting as a current passing through the LED of the semiconductor lamp iy

When, in an exceptional fault case, e.g. in the event of a short circuit in the capacitor bank, the primary current i ^ increases to 1200 A, the secondary current j. compared to. For this reason, the relay connection vo: i is damaged La to operate even in an exceptional fault.

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The cross-sectional area of the iron core IC is preferably about 6 cm, whereby a saturation limit of 0.0 ^ 5 Vs is reached.

Within the scope of the invention, it is also possible to consider solutions that differ from the embodiment described above. Thus, instead of a semiconductor limb LED, for example, an incandescent lamp, a gas discharge latch or other light emitting element can be used.

Instead of the control resistor R, a fixed resistor or an adjustable resistor arrangement can be used.

Instead of a full-wave rectifier, a half-wave rectifier can also be used. When using a half-wave rectifier, a resistor R can be connected to the secondary terminals of the current transformer.

A series resistor (eg 1 ohm) can also be connected to the secondary circuit, which enhances the protection effect. This is based on the fact that the voltage rises faster, which in turn results in the fastest saturation of the iron core. When the series resistance is selected to be small, the level detector D does not warp 1; u> nc ·? substantially change.

Claims (6)

1+ Claims: 625 9 9 A circuit for measuring a fault current, and in particular a rectifying current (i ^) in high voltage batteries, and for transmitting measurement information from one potential level to another via an optical transmission path (F), characterized in that the circuit comprises - an iron core (IC) current transformer (CT). i1) may be energized, - a rectifier (RF) connected in a manner known per se to the secondary of the current transformer (CT), - a level detector (D) whose input is connected to the output of the rectifier (RF), - a light emitting element (LED) which is connected to the output of the level detector (D), and - a resistor (R) connected to the input terminals of the secondary or level detector (D) of the current transformer (CT) in a manner known per se. A circuit according to claim 1, characterized in that the level detector (D) is a thyristor with a zener diode in the gate. A circuit according to claim 1, characterized in that the light emitting element is a semiconductor lamp (LED). U. A circuit according to claim 1, characterized in that the light emitting element (LED) is an incandescent lamp. A circuit according to claim 1, characterized in that the light emitting element (LED) is a gas discharge lamp. Connection according to Claim 1, characterized in that the cross-section of the iron core (IC) of the current transformer (CT) is selected so as to achieve a saturation limit of 0.0U to 0.05Vs. i