RU2160478C2 - Dynamically disconnected single-phase ac circuit breaker - Google Patents

Abstract

FIELD: circuit-opening devices for ac tractive equipment of electrified railways. SUBSTANCE: circuit breaker has current sensor 10 whose input is connected to movable contact of vacuum arc-control device 3; terminal leads of current sensor 10 are connected to input of rectifier unit 11 whose output is connected to mean-current storage unit 12; output of the latter is connected to coil of circuit breaker 6; polarity of signal is same as that of circuit-breaker OFF-signal coming from circuit-breaker control unit. EFFECT: fast response to overload and short-circuit currents; provision for dynamic disconnection of load current depending on its magnitude. 4 dwg

Description

 A single-phase AC circuit breaker with dynamic shutdown refers to switching devices used in the traction power supply system of AC electric railways, and is intended for accelerated shutdown of short circuit currents and overload currents of the AC electric traction network.

 In the electric traction AC network, a short circuit may occur [1]. Short circuit currents, especially with close short circuits, can have the most negative thermal and dynamic effects on electric traction equipment, including power step-down transformers. The occurrence of a short circuit is accompanied by a shock current of a short circuit, the value of which can exceed the maximum permissible values for traction equipment. Therefore, short-circuit currents must be disconnected as soon as possible, before the occurrence of a short-circuit shock current, that is, faster than 10 ms.

 Existing AC circuit breakers, including vacuum circuit breakers, do not have time to disconnect the short circuit before the occurrence of a short-circuit shock current, since for them to trip, it takes time that it takes to analyze the change in the load current - short circuit current, time the increase in magnetic flux in the electromagnetic drive of the circuit breaker, the intrinsic time of movement of the circuit breaker trip rod - the total time is 40-100 ms [2].

 Known are automatic high-speed DC switches that analyze the mode of change of the load current already at the time of its sharp change from the load current to the short-circuit current or the current of dangerous overload and automatically send a command to the circuit breaker to shut it down. An example of such a switch is VAB-43 (VAB-45, VAB-49) [3].

 An automatic high-speed DC switch is switched on by a signal supplied to its closing coil, the holding coil of the switch is constantly energized and creates the necessary magnetic flux to keep the switch in the on position. The electromagnetic flux of the switching coil is added to the electromagnetic flux of the holding coil, the switch turns on and reduces the magnetic gap between the contacts and the main magnetic circuit. Then the closing coil is turned off, the electromagnetic flux of the holding coil is enough to hold the switch in the on position.

 In the on position of the circuit breaker, the load current flows through the main current loop of the circuit breaker, which creates a demagnetizing electromagnetic flux in the main magnetic circuit of the circuit breaker. In operating mode, the electromagnetic flow of the load current is insufficient to trip the high-speed circuit breaker. When the load current increases to a short circuit current or to a dangerous overload current, the electromagnetic flux of the main current loop of the circuit breaker increases. It turns out to be more than the electromagnetic flux of the holding coil, and the circuit breaker trips under the influence of mechanical springs.

 However, automatic high-speed DC switches capable of extinguishing an electric arc when a short-circuit or overload current is interrupted, capable of disconnecting the operating load current if necessary during operation, are designed for use with direct current and therefore cannot be used with alternating current. Analog device - automatic high-speed switch VAB-43 has an electromagnetic circuit to hold the switch in the on position. The design of the analog device and its principle of operation are given in Appendix 1.

 To date, a vacuum circuit breaker type BB-TEL is known [4]. This switch consists of three poles with integrated electromagnetic drives, which are located in the common base of the switch. By the “turn on” command coming from the control unit of the circuit breaker, the switching current flows along the circuit breaker coil, the circuit breaker armature moves upward, compressing the circuit breaker springs. Together with the anchor, the movable contact of the vacuum interrupter chamber moves. The movable and fixed contacts of the vacuum interrupter chamber are closed. The switch coil is de-energized. The drive of the circuit breaker is held in the on position due to the magnetic latch, that is, due to the residual magnetic induction of the permanent ring magnet of the mechanism for holding the circuit breaker in the on position.

 By the command “disconnect”, the circuit breaker trip current is supplied from the control unit to the circuit breaker coil. The polarity of the application of the trip current is opposite to that of the circuit breaker. The tripping current, flowing along the coil of the switch, creates an electromagnetic flux directed opposite to the direction of the magnetic flux of the permanent ring magnet of the magnetic latch of the switch. The switch resets from the magnetic latch. Breaking springs cause the switch armature to move down. The movable and fixed contacts of the vacuum interrupter chamber open. The switch trips. It is possible to trip the circuit breaker manually by turning the shaft of the circuit breaker drive. The design of the BB-TEL vacuum circuit breaker is given in Appendix 2.

 The specified switch is closest in design and construction to the claimed one, and it is selected as a prototype.

 The inventive switch is intended for accelerated shutdown of short-circuit currents or overload currents when they reach the threshold of the current sensor setting of the circuit breaker until these currents reach their maximum values - shock current, steady-state short-circuit current, maximum dangerous overload current. The switch is designed to quickly disconnect the load current dynamically - depending on the magnitude of the current flowing along the load circuit.

 To do this, into a single-phase AC circuit breaker with dynamic shutdown, containing a vacuum arcing chamber, a stationary contact of a vacuum arcing chamber, a movable contact of a vacuum arcing chamber, preload springs, opening springs, a circuit breaker coil, a magnetic mechanism for holding the circuit breaker in the on state - a magnetic latch, a drive circuit breaker, circuit breaker control unit, according to the invention, a current sensor, a rectifier device, a memory unit are further included The average current value.

 The current sensor (DT) 10 is connected by its input to the movable contact of the vacuum interrupter chamber 3, that is, to a controlled electrical circuit through which the load current flows. The electric circuit, the load current of which is controlled by the current sensor 10, receives power from the fixed contact of the vacuum interrupter chamber 2 and from the movable contact of the vacuum interrupter chamber 3. The terminals of the current sensor 10 are connected to the input of the rectifier device 11 (VU). The rectifier device 11 rectifies the alternating current flowing in the load circuit into direct current flowing through the control circuit of the switch. At the output of the rectifier device 11, a memory unit for the average current value 12 (PSU) is turned on. The outputs of the rectifier device 11 with an average current value memory unit 12 included in them are connected directly to the coil of the switch 6.

 The single-phase AC circuit breaker with dynamic shutdown is turned on by the command received from the control unit of the switch 9 (BUV). The turn-on current flows from the control unit of the switch 9 to the coil of the switch 6 in the turn-on polarity (see Fig. 1). The current of the circuit breaker creates an electromagnetic flux in the coil of the circuit breaker 6, which is summed with the magnetic flux of a permanent ring magnet of the magnetic latch of the circuit breaker. The switch armature moves up. In this case, the disconnecting springs of the switch 5 are compressed. Together with the armature, the movable contact of the vacuum arcing chamber 3 moves. The contacts movable 3 and the stationary 2 of the vacuum arcing chamber 1 are closed. The coil of the switch 6 is de-energized. The drive of the switch is held in the on position due to the residual magnetic induction of the permanent ring magnet of the magnetic mechanism for holding the switch in the on position 7.

 In normal operation of the electric traction network, the switch is turned on, the load current does not exceed the settings of the current sensor 10. In this case, the load current is converted to the corresponding current of the control circuit of the switch, which does not exceed the settings of the current sensor 10. This current flows through the rectifier 11, which rectifies the variable current in constant. Standing in the output of the rectifier device 11, the average current value memory unit 12 smooths the pulsating direct current and stores the average current value. A smoothed rectified current flows through the coil of the switch 6, and the electromagnetic flux of this current is opposite to the magnetic flux of the permanent ring magnet of the magnetic latch of the switch 7. But the current magnitude of the normal mode of operation of the electric traction network is not enough to overcome the magnetic flux of the ring magnet 7 (see Fig. 2). The switch does not reset from the magnetic latch and remains in the on position.

 In the event of a short circuit or a dangerous overload mode, the load current of the circuit breaker exceeds the setting of the current sensor 10. Current sensor 10 converts the load current into the current of the control circuits. The rectifier device 11 rectifies this converted alternating current into direct current, and the average current value memory unit 12 smooths out the ripple of this current. The rectified smoothed current flows along the coil of the switch 6 (see figure 3). In this case, the electromagnetic flux of the rectified smoothed current flowing along the coil of the switch 6 is opposite to the magnetic flux of the permanent annular magnet 7 of the magnetic latch of the switch. With a short circuit or with a dangerous overload, the current transformed by the current sensor 10, the rectifier 11 and the memory unit of the average current value 12 is enough to overcome the residual magnetic induction of the permanent magnet 7 of the holding mechanism. The drive of the circuit breaker is reset from the magnetic latch, the circuit breaker trips.

 When the circuit breaker is disconnected from the control unit of the circuit breaker 9 in case of need during the operation, the trip current flows from the control unit of the circuit breaker 9 (see figure 4). The electromagnetic current flowing through the coil of the circuit breaker 6 from the control unit of the circuit breaker 9 is sufficient to overcome the force of the permanent magnet holding the circuit breaker in the on position.

List of references
1. Marquardt K.G. Power supply of electric railways. Textbook for high schools. M., Transport, 1965 .-- 464 p.

 2. Handbook of high voltage electrical installations. Ed. Baumstein I.A., Bazhanova S.A. - 3rd ed., Revised. and add. - M .: Energoatomizdat, 1989 .-- 768 p.

 3. Prokhorsky A. A. Traction and transformer substations. Textbook for technical schools. transp. - 4th ed., Revised. and add. - M.: Transport, 1983.- 496 p.

 4. The data of the manufacturer of the vacuum circuit breaker type BB-TEL "Tavrida - Electric" for 1997.

Claims (1)

 A single-phase AC circuit breaker with dynamic shutdown, comprising a vacuum arcing chamber, a stationary contact of a vacuum arcing chamber, a movable contact of a vacuum arcing chamber, preload springs, breaking springs, a circuit breaker coil, a magnetic latch of a circuit breaker with a permanent ring magnet, a circuit breaker drive, a circuit breaker control unit, characterized in that the circuit breaker additionally includes a current sensor, a rectifier device, a medium memory unit current values, the current sensor being connected to the movable contact of the vacuum interrupter chamber by its input, the current sensor leads are connected to the input of the rectifier device, the average current value memory unit is turned on at the output of the rectifier device, the output of the rectifier device is connected directly to the circuit breaker coil, when the circuit breaker is turned off, the electromagnetic flow The current flowing through the coil of the switch is opposite to the magnetic flux of the permanent ring magnet of the magnetic latch of the switch.

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