SU964839A1 - Device for differential protection of dc network sections - Google Patents

Description

(54) DEVICE FOR DIFFERENTIAL SECURITY OF DC POWER SUPPLY AREAS

The invention relates to electrical engineering and can be used to differentially protect sections of a DC network.

A device for differential protection of sections of the DC network is known, which contains sensors of the current derivative, a thyristor connected to the mains voltage, the anode circuit of which includes a diode and an automatic release switch winding of the supply connection, a storage capacitor connected through the aforementioned diode to the primary terminals the network, the beginning of the output, the windings of the sensors of the derivative of the current are connected to a common point, and the ends are connected. To the inputs of the diode half-bridges, the common outputs of which include two connected sequentially identical resistors to a common point which is connected a control electrode of the thyristor and one of the terminals of the differential resistor, the other terminal of which is connected to the cathode of the thyristor and one of the terminals of the capacitor, the connected Nogo its second terminal to the common point of the windings of the current sensors derivative 1J.

This device has insufficient selectivity in the modes of external damage in which (due to the different degree of saturation of the current derivative sensors) on the differential resistor can. allocate a voltage sufficient to falsely trigger the thyristor.

Most. Close to the previous one

10 the technical solution is a device for differential protection of sections of the DC network, which in addition to the indicated elements contains a blocking thyristor and a relay, the clocks of which are connected in series with the release coil 2,

The disadvantage of this device lies in the fact that the release triggering in the mode of

20 external damage is carried out mechanically (the relay contacts break when the blocking thyristor is turned on). Therefore, there may be a lag gap

5 contacts of the relay y the release of the circuit breaker has time to work, i.e. The device has insufficient selectivity. In addition, it is difficult to coordinate work

30 sufficiently powerful thyristors with

low current circuits by microreactors connected at the outlet of a rectifying bridge. These resistors must be sufficiently high impedance since the current-derivative sensors work practically in idle mode. The difficulty in coordinating the joint operation of the above protection elements causes the unreliable functioning of the reacting and blocking thyristors.

The purpose of the invention is to increase the selectivity and reliability of the device.

The goal is achieved by the fact that the device for differential protection of sections of the DC network, containing sensors for the derivative of the current of the supply and supply connections, a rectifying bridge whose input terminals are connected to the outputs of the sensors, a capacitor connected through a diode to the supply voltage, first a thyro-stor connected to a capacitor through a series-connected winding of the relay and its normally open contact, the second thyristor / connected in series with the winding of the release The power supply switch, and resistors, are equipped with additional resistors and two additional thyristors, the anodes and cathodes of which, through resistors, are connected to the circuit terminals of the first thyristor connected in series and the relay windings, the cathodes of the additional thyristors are also connected to the control electrodes of the aforementioned thyristors accordingly, their control electrodes are connected through some resistors to the rectifier bridge poles, and through others to the cathodes of the mentioned thyristors, which are connected connecting a supply point of attachment of the sensor output to the output of the sensor attachment fed, wherein the bridge between the poles of the resistor included, the outputs of sensors are connected in series, and the circuit .From series connected thyristor and the second winding is included paral- releasers. for the first thyristor.

In addition, a resistor is barely turned on in parallel with the winding.

The drawing is a diagram of the device.

The device contains. Sensor 1 derived supply current and sensor 2 powered connections, high bridge 3, to the output of which three main -4-6 and two additional 7 and 8 resistors are connected, diode 9, storage capacitor 10, limiting resistors 11-14, reactive additional 15 and primary 16 thyristors and blocking additional 17 and main 18 thyristors, the windings of the release 19 of the power supply circuit breaker and the relay 20, the relay contact 21 and the shunt resistor 22.

The device works as follows.

As information signals for differential protection 0, voltages and acting on the control electrodes of the thyristors 15 and 17 are used.

In normal operating conditions (when connecting or removing 5 loads) the following

ratios between stresses and

V,

Uca 0 / i

(Uca 7 0 /

)or

0 tU-bc Oh, Oh. .

 Positive direction C; and Y-ls Ukaz.any-arrows. At the first of the indicated ratios (UCQ Ut) c 0) is neither reacting 15 nor thyristors blocking 17, they do not work. When U-fjc 7 o triggers the thyristor 15, turns on the main reactive thyristor 16 and a discharge current of the storage capacitor starts to flow through the release coil. But the inertial release mechanism does not have time to work, because simultaneously with the thyristor 15 triggered, the thyristor 17 triggers (at 0), turns on the main blocking thyristor chorus 18, which bypass

the winding disengaged 19. The investigator-. . but, the defense does not match. in the specified mode. Similarly, the protection is valid when. external short-haul

0 Turning off the thyristors occurs when the relay 20 is triggered and its contacts are opened 21. In the internal short circuit mode. the following relationship holds:

 7 o

{and 0c.

When and about 7, the additional 15, and then the main 16 reacting thyristors, work initially.

l and the discharge current of the capacitor 10 flows through the winding of the release, causing it to disconnect.

The blocking thyristor 17 does not operate when the UCQ – Shunt resistance 22 is used to increase the response time of the relay 20 compared to the trip time of the circuit breaker. In this case, the order of operation is ensured during internal

0 him k.z. first the automatic switch and only then the relay.

Thus, the proposed device functions correctly in all possible modes. Connection

5 main blocking thyristor 18

allows shunting of the release winding and thereby increase the selectivity of the protection device. The use of low-power additional thyristors 15 and 17 makes it possible to coordinate the work of sufficiently powerful. Main thyristors 16 and 18 with low-current output circuits of the bridge bridge rectifier. 3 and thereby increase the reliability of the protection operation. Increasing the selectivity and reliability of the protection device is the positive effect of the invention,

Claims (2)

1. Device for differential protection of network sections of direct current, containing sensors of the derivative of current of the supply and supply connections, a rectifying motor, the input terminals of which are connected to the outputs of the sensors, a capacitor connected through a diode to the supply voltage, the first thyristor connected to the capacitor through the successively connected winding of the relay and its normally open contact, the second thyristor connected in series with the winding of the switch of the power supply circuit breaker, connection nor, and resistors, characterized in that, in order to ensure selectivity and reliability, it is provided resistors and two additional thyristors, the anodes and cathodes of which, through resistors, are connected by circuit terminals from the series-connected first thyristor and. relay coils, cathodes of additional thyristors are also connected to control electrodes of said thyristors, respectively, their control electrodes are connected to the rectifier bridge poles through some resistors and through cathodes of said thyristors through others that are connected to the output connection point of the supply terminal sensor to the sensor output of the powered supply, and a resistor is connected between the poles of the bridge, the sensor outputs are connected in series, and the circuit is in series the connected second thyristor and the release winding are connected in parallel with the first thyristor. 2. The device according to claim 1, which is based on the fact that a resistor is connected in parallel with the winding of the relay.  Sources of information taken into account in the examination 1. USSR author's certificate. 723716, cl. H 02 H 3/28, 1977. 2. USSR author's certificate No. 832644, cl. H 02 H 3/28, 1979 (prototype). I / -Y