SU1376130A1 - Device for protecting against short circuit steady leakage current - Google Patents

Abstract

The invention relates to electrical engineering and can be used for high-speed protection of triggering equipment. The aim of the invention is to increase the speed. The device contains two shoulders U-shaped electrodynamic element (EDE) 1, rigidly mounted on a rotating insulating frame (PR) 2 so that the rotary axis 3 of the PR 2 coincides with the axis of symmetry of the EDE 1. Looped current leads 4 and . 5 are electrically connected in series with each other by means of a jumper 6 connecting the ends of those branches of the current leads 4 and 5, in the direction towards which EDE 1 is turned and with EDE 1 by means of a flexible connection 7. 3 Il. "

Description

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The invention relates to electrical engineering, in particular to electrical equipment of low-voltage electrical power networks, and can be used for high-speed protection of control gears containing semiconductor elements.

The purpose of the invention is to increase speed.

FIG. 1 shows the device

in general view; in fig. 2 is a diagram of the flow of current in the device (the direction of the current is shown by arrows); in fig. 3 - oscillograms of current changes.

The device for protection of electrical equipment from short-circuit through currents contains (Fig. 1) two shoulders U-shaped electrodynamic element 1 rigidly mounted on a rotating insulating frame 2 so that the axis 3 of the rotation of the frame 2 coincides with the axis of symmetry of the electrodynamic element 1, two loop current leads 4 and 5, electrically connected in series with one another by means of a jumper 6 connecting the ends of those branches of the conductors 4 and 5, in the direction to which the rotation of the electrodynamic element 1 is necessary, and with the electrodes namic element 1 using a flexible connection 7, a current supply 8, electrically connected to an electrodynamic element 1 using a flexible connection 9, a current supply 10, electrically isolated from the current supply cable 4, 5 and 8 and from an electrodynamic element 1, and shunt contacts 11 and 12 , of which the moving contact 11 is fixed, is the chain of the arm of the electrodynamic element T, with which the current lead 8 is connected, and the fixed contact 12 on the insulated current lead 10. I.

The rotary frame 2 with the electrodynamic element 1 fixed on it is held in the initial position by a return spring 13. In this position the rotary frame 2 spirals onto the corresponding branches of the loop current leads 4 and 5. The gaps between the arms of the electrodynamic element 1 and those branches of the current leads 4 and 5 are in the direction which need to be rotated, is chosen more than the clearance of the shunt pins 11 and 12 so that

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the closed state to prevent other contact between the current leads 4 and 5 with the electrodynamic element 1.

The protected electrical equipment 14 (Fig. 2) is connected to the current leads 8 and 10, and the device is connected to the power grid by current leads 4 and 10. The devices can be made as a structural unit embedded in the protected electrical equipment, or it can be universal A new structural unit with an operation current regulator. The device operation current is regulated by the tension of the return spring 13.

On the oscillogram (Fig. 3) it is indicated: 1 - current in the power grid, current in the protected

- current in ts0

eo about electrical equipment, I

sc

pi of the shunt contacts, t, is the moment of occurrence of a short circuit, t is the moment of closing of the shunt contacts of the device, t is the moment of operation of the feeder automatic switch; t is the moment of complete disconnection of current I., 1 is the load current.

The device works as follows.

When normally possible modes of operation of electrical equipment leaks5

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five

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The current 1 „(Fig. 3) that does not exceed the maximum allowable. The turning point of the electrodynamic forces generated by this current between the loop current leads 4 and 5 and the corresponding arms of the electrodynamic element 1 is insufficient to overcome the moment created by the force of the return spring 13. In this In this case, the entire network current supplied to the current lead 10 flows through a circuit consisting of a series connection of electrical equipment 14 of the current lead 8, a flexible connection 9, an electrodynamic element 1, a flexible connection 7 loop current lead 5, jumpers 6 and

loop current lead 4.

I,

When a short circuit occurs in the electric power network at time t (fig.Z), a rapidly increasing through current 1 flows through it. At the same time, the moment created by electrodynamic forces relative to the rotary axis 3,

exceeds the moment of force of the return spring 13. The electrodynamic element 1 together with the rotary frame 2 rotates around the rotary axis 3, - and at the moment of time t the shunt contacts 11 and 12 are closed after which the main portion of the short circuit current flows from the current supply 10 to the loop current lead 4 through shunt contacts 11 and 12, electrodynamic element 1, flexible connection 7, loop current supply 5 and jumper 6. At the same time, the current in the protected electrical equipment I, Q flows through the device protected by electrical equipment for 14 h Through the current lead 8 and the flexible connection 9, ten times smaller than the through short circuit current. Therefore, during the short-circuit current off time, the feeder circuit breaker (time interval t, -t4 in FIG. 3) does not cause electrical damage.

Due to the fact that the inertia of the U-shaped electrodynamic element 1, whose shoulders are as close as possible to the rotary axis 3, is significantly (almost) less than the inertia of the electrodynamic elements with identical shoulder sizes in known devices, the speed of the proposed device is above. In addition, the speed increase is facilitated by the fact that regardless of the state of the shunt contacts 11 and 12 (closed or open), the entire short current always flows through both loop current leads 4 and 5 and electrodynamic element 1, i.e. the electrodynamic tripping force is developed by the entire electrodynamic circuit of the device and does not change when the shunt contacts 11 and 12 are closed. This also ensures reliable contacting of the shunt contacts

11 and 12 after their closure. Improving the reliability of contacting the shunt contacts 11 and

12 is also achieved by the fact that, in the U-shaped electrodynamic element 1, they are located at a much smaller distance from the axis of rotation than in known devices (with identical shoulder sizes).

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five

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five

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At the same time, the contact pushes on the shunt contacts increase accordingly.

The high speed and reliable contacting of the shunt contacts allow it to be used for the protection of electrical equipment containing semiconductor elements, both from the through short-circuit currents and from the long-term unacceptable overload currents of the conductive elements (for example, in emergency operation-induced operating modes).

In order to avoid false triggering of the rotary electrodynamic element 1 when operating the device under shock and vibration conditions (for example, on ships of the navy), it together with the rotary frame 2 is statically balanced relative to the rotary axis 3,

With identical shoulder sizes of electrodynamic elements, the response time of the proposed device is on average about 3 times less than the known one.

For example, with a short circuit current in a test circuit of 10 kA (steady-state value) and a time constant of the circuit of 2.5 ms, the response time of the device with the U-shaped electrodynamic element is no more than 0.003 s, and y. known device reaches 0.005 s. The shunt contacts at this current are 68 and 38 N, respectively. Testing the layout of the proposed device with a semiconductor converter protected by it for a rated current of 300 A shows that for all through short-circuit currents that are installed in the test circuit (up to 20 kA), no failure of semiconductor elements is observed.

The proposed device is most appropriate to use for fast-acting protection against both short-circuit through currents and unacceptable overload currents of low-voltage electrical equipment containing semiconductor elements and / or installed in high-power electric power networks

Claims (1)

lengths in which short-circuit currents reach hundreds of ki-amperes (e.g., in shipboard electrical installations). A device for protection against short-circuit through currents containing a rotary axis, a two-arm electrodynamic rotatable element statically balanced with respect to the rotary axis, two loop current leads electrically connected to a two-arm rotatable electrodynamic element with flexible connections, and shunt contacts, of which are movable mounted on one of the shoulders of the two shoulders of a rotating electrodynamic element, and the fixed one on the third electrical lead, electrically isolated from the two shoulders turning electrodynamic element, due to the fact that, in order to increase speed, it is equipped with a jumper and a rotating insulating frame, rigidly connected to the rotary axis, the two-arm rotary electrodynamic element is U-shaped and rigidly fixed on the rotating insulating frame so that that the pivot axis coincides with the axis of symmetry of the two-armed rotary electrodynamic element, and the loop-back conductors are electrically interconnected by the indicated jumper at the ends of those branches to which two lechy electrodynamic rotary member and covers portions dvuple- Chenoa electrodynamic pivoting element, which are arranged parallel to the pivot axis. „, - Phage. 2 Ih 30 Ih 4UA / tj tztj tif Fig.Z h