RU2481686C2 - Protective cutout device - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: device comprises a differential current transformer, a relay acting at an automatic circuit breaker, besides, through a window of a core of the differential transformer there are two wires of an overhead power transmission line stretching, to which two capacitors are connected in the beginning of the line, connected to the first grounding device and two capacitors in the end of the line connected with the second grounding device.

EFFECT: provision of protection for humans and animals in case of breaks of overhead power transmission line wires and in case of short circuits between wires.

1 dwg

Description

The invention relates to the protection of single-phase electrical installations with voltages up to 1000 V from emergency conditions that can cause electric shock to people and animals, as well as fires from short circuits.

Known protective shutdown device (S.I. Kostruba. Electrical safety on farms. - M .: Agropromizdat, 1990, p. 31, Fig. 10). This device is selected as an analog. The known device contains a differential transformer, to the secondary winding of which a sensitive organ (relay) is connected, acting on the protective device. Through the window, made in the form of a torus, the core of the transformer passes the zero and three phase wires, which are the primary winding of the differential current transformer. A disadvantage of the known device is the impossibility of triggering during breaks and falling to the ground wires of an overhead power line.

As a prototype, a residual current device (patent RU 2273936 C1) was selected, containing a differential current transformer, to the secondary winding of which a relay acting on the circuit breaker is connected, and the phase wires of the power line serving as the primary winding pass through the window of the differential transformer core, the first two are connected in series capacitors are connected by their own conclusions to the phase conductors of the line to the differential transformer and the second two in series connected capacitors are connected by one conclusions to phase wires at the end of the line.

The disadvantage of the prototype is the long shutdown time of remote short circuits between the wires on the power line, which are disabled by the thermal release of the circuit breaker, and the complexity of the device with a large number of capacitors in operation.

The technical task of the invention is to accelerate the shutdown of remote short circuits between the wires on the power line and simplify the circuit of the protective shutdown device.

A protective shutdown device is proposed, which includes a differential current transformer, through the window of the core of which two wires of the power line pass, and a relay acting on the circuit breaker is connected to the secondary winding. To the two wires of the power line to the differential transformer are connected the first two series-connected capacitors with their own conclusions; the second two series-connected capacitors are connected by one terminals to two wires at the end of the power line. The common point of the first two capacitors is connected to the first grounding device, and at the end of the power line a second grounding device is introduced, to which the common point of the second two series-connected capacitors is connected. A secondary winding of a single-phase transformer is introduced into the circuit of the proposed protective shutdown device, and the two wires of the power line must have different resistance.

The technical result of the invention is the accelerated disconnection of short circuits between the wires on the power line and the simplicity of the device with a small number of elements.

Figure 1 presents the circuit diagram of the proposed protective shutdown device.

The proposed protective shutdown device contains a differential current transformer 1, to the secondary winding of which 3 is connected a relay 4, the output of which is connected to the circuit breaker 5. The first two capacitors 6 are connected in series to the terminals of the secondary winding of the step-down transformer 10, the common point of which 13 is connected to the first ground device 12. From the circuit breaker 5, two wires 2 of the power line pass through the window of the differential current transformer 1, I have these wires t different resistance. At the end of the power line at points 9, a second two series-connected capacitors are connected, the common point of which 15 is connected to the second grounding device 14.

The proposed device works as follows. When the transformer 10 and the circuit breaker 5 are turned on, load currents 16 of equal magnitude flow through wires 2. At the beginning of the line, under the influence of the secondary voltage of the transformer, current flows through equal capacitors 6. Half of the supplied voltage drops on each of them. The load current in the wires with different resistances causes a different voltage drop, so between points 9 the voltage supplied to the capacitors 8 will be slightly less than the voltage supplied to the capacitors 6. Each capacitor 8 will have half the voltage applied. The resistances of wires 2 are different in magnitude, each of them will have different voltage drops. Under the influence of the difference in voltage drops in the wires 2 between the common points 13 and 15 of the capacitors 6 and 8, a small current will flow to which the differential transformer does not respond.

When one of the wires 2 is broken, a current flows through one of the capacitors 8 and grounding devices 12 and 14, which closes in addition to the window of the differential transformer 1, relay 4 activates at its output and switches off the circuit breaker 5.

If the insulation of any of the wires 2 is damaged, the wire is connected to the ground, a current flows through the place of insulation damage and passes through one of the capacitors, which closes in addition to the window of the differential transformer 1, relay 4 is activated at its output and the circuit breaker 5 trips.

With a short circuit between wires 2, the voltage drop will increase on each of them, and the difference in voltage drops will increase, under the influence of this difference in voltage drops through capacitors 8, grounding devices 12 and 14 and capacitors 6, a current will flow, which closes in addition to the window of differential transformer 1 , at its output, relay 4 activates and trips the circuit breaker 5.

Thus, the proposed device responds to all types of damage on a two-wire power line; short circuits by the device are disconnected accelerated in comparison with the prototype.

Claims (1)

A residual current device containing a differential current transformer, through the window of the core of which two wires of the power line serving as the primary winding pass, and a relay acting on the circuit breaker is connected to the secondary winding; - the first two series-connected capacitors are connected by their own conclusions to two wires of the power line to the differential transformer; - the second two series-connected capacitors are connected by one terminals to two wires at the end of the power line, characterized in that the secondary winding of a single-phase transformer is connected to the circuit, to which the two wires of the power line are connected, connected through a breakdown fuse to the first grounding device to which is connected a common point of the first two capacitors, and at the end of the power line a second grounding device is introduced, to which a common point of the second two series-connected capacitors, wherein the resistance of one wire over a second resistance wire transmission line.