SU851603A2 - Device for differential protecting of collecting buses - Google Patents

Description

(54) DEVICE FOR DIFFERENTIAL PROTECTION

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The invention relates to relay protection and can be used for differential protection of busbars of AC networks.

According to the main auth. No. 6 26463, a device for differential busbar protection is known, which contains current-voltage converters, the output windings of which are connected in series and connected to the inputs of a multi-shoulder rectifying bridge, and with two extreme leads connected to the primary winding of an isolation transformer, to the secondary winding of which is a rectifying bridge, working and braking resistors and reacting authority 1.

However, the known device has insufficient reliability. This is because it does not monitor the health of the output windings of the transducers and connecting wires (secondary protection circuits). These elements of difzashchity most often than others, can be damaged, and the lack of control of their health significantly reduces the reliability of protection.

The purpose of the invention is the reliability of the device. TIRED TRAINS

This goal is achieved by the fact that the device for differential protection is equipped with an additional rectifying bridge, the input of which is connected to the alternating voltage source, and its output is connected to one of the extreme terminals of the series-connected output windings of the converters ok-voltage

10 and with one of the primary output pins, the coils of an isolation transformer, as well as with the pins of the additionally installed capacitor and with the pins of the additionally installed alternating resistor, the average output of which is the current and the average point of the current-voltage transducer connected in series to the signaling organ.

The drawing shows a diagram of the proposed device.

The circuit contains current transformers of power supply 1 and power 25 connections, the output windings of which are connected in series and connected to the inputs of the multi-shoulder rectifying bridge 3, two extreme .1 windings of the windings are connected 30 to the primary winding separation

transformer 4, to the secondary winding of which a rectifying bridge 5 is connected, brake b and operating resistors 7, reactance unit 8, additional rectifying bridge 9, capacitor 10, variable resistor 11 and signaling authority 12.

The operation of the proposed protection device is similar to the known

The monitoring of the resistance of the output windings of the converters and connecting wires between them (according to the resistance value of the indicated elements, their condition is determined) is carried out using the bridge method. The two shoulders of the bridge are formed; output windings of converters, divided by the midpoint between them into two parts, almost identical in their resistance. E of one of these shoulders includes the primary winding of an isolation transformer, the resistance of which is comparable with the active resistance of the OUTPUT winding of the converter voltage. The other two arms of the bridge are formed by two parts of the variable resistor. The bridge diagonal (the medium terminal of the variable resistor and the midpoint between the windings of the transducers) is connected to the organ signal of the position. The average output of the variable resistor when the protection is commissioned is set so that at the input of the signaling organ there is almost zero voltage. If there is a short circuit or a break in the output windings of the transducers or connecting wires between them (i.e., if the equal resistance of the bridge shoulders is violated) in the diagonal of the bridge, a potential difference occurs, to which the signaling organ responds. This potential difference is created by the flow of direct current across the arms of the bridge, due to the voltage at the output of the rectifying bridge 9 (in the drawing, the arrows indicate the flow of direct current through the secondary circuits of protection). With the proposed method of controlling resistance, low requirements are imposed on stabilizing the DC voltage at the output of the bridge, the input of which is connected to a source of alternating voltage of the required value.

Therefore, it suffices to smooth the output voltage of the rectifier bridge by the capacitor 10.

It should be noted that the high resistance brake resistor 6 has almost no effect on the accuracy of the proposed resistance control, since its resistance is 2-3 orders of magnitude higher than that of the bridge, and the connection of the additional rectifying bridge, capacitor and variable resistor in series with the output windings of the converters It does not reduce the sensitivity of protection in its camera, since almost the entire variable differential signal is released on the primary winding of the separation transformer. opa. This is due to the high inductance resistance of the winding of the latter (magnetic permeability of the transformer core by 2-3 times higher than the magnetic permeability of the cores of the transducers) to alternating current and low resistance in parallel with the newly introduced elements interconnected between themselves.

The presence of a time delay in the signaling organ excludes its operation during short circuits and operation of the differential protection.

The automatic control of the state of the secondary protection circuits proposed in the device, which makes it possible to detect their damage before the onset of an emergency mode / increases the reliability of the proposed device for the differential protection of busbars. This causes a significant positive effect.

It is most expedient to use the proposed device for the protection of autonomous electric power systems, where the consequences of emergency operation may be most severe.

Claims (1)

1. USSR author's certificate 626463, cl. H 02 H 3/28, 1976.