SU1570939A1 - Apparatus for protecting d.c. traction substation converter from overvoltage - Google Patents

Abstract

The invention relates to electrified transport, in particular, to technical means of traction substations of electric railways of direct current. The purpose of the invention is to increase reliability. The device protects the converter transformer and the semiconductor converter rectifier from overvoltage, and contains a discharge circuit 11 with a current limiting resistor 13, two storage capacitors with discharge and charging resistors, a diode, a voltage relay, a charging unit, and a control unit for the discharge and voltage control voltage meter. A second memory capacitor, gaps for controlling the voltage and voltage control, and a voltage meter are also introduced into the device. 1 il.

Description

The invention relates to electric railways and is intended to protect against overvoltages of high-power semiconductor converters for traction substations.

The purpose of the invention is to increase reliability.

The drawing shows a single-line electrical circuit of the device.

The device comprises associated with busbars 1, disconnector 2, oil switch 3, transformer 4, semiconductor converter 5, voltmeter 6, high-speed switch 7, disconnector 8, buses 9 and connecting wires 10 of discharge voltage 11 with a spark gap 12, current limiting resistor 13 and diode 14. The device also contains a first storage capacitor 15 with a discharge resistor 16, a second storage capacitor 17 with a discharge and charging resistors 18 and 19, a voltage meter - a voltmeter 20, a charging unit 21, the control unit 22 and the control unit 23. The charging unit 21 consists of a rectifier 24, a charging resistor 25, limiting the charging current of the capacitor 15, boosting 26, and lowering 27 transformers. The control unit 22 has a variable 28 and a constant 29 resistors, a voltage relay 30 with buttons 31 and 32 for controlling its position. The control unit 23 includes an isolation transformer 33, a rectifier 34, a stabilization chain 35 containing a resistor 36 and a zener diode 37, a dividing diodes 38 and 39, a voltage relay 40 and 41, respectively, with storage capacitors 42 and 43, a button 44 for position control relay 41, indicator light 45.

The drawing shows possible embodiments of the charging unit 21, the adjusting unit 22 and the control unit 23, which are convenient for implementing the proposed device when using commercially available electrical products for traction stations.

A special feature of the charging unit 21 is a two-stroke (rectifying both half-waves of sinusoidal voltage) rectifier circuit 24 and the inclusion of charging resistor 25 between its input and the secondary winding of transformer 26. This allows current to flow in circuit 11 from the primary winding of the transformer 33 of the control unit 23 and thus it is easy and convenient to control the time of extinguishing the arrester with the help of the relay 41 and isolate the relay 40 protecting the discharge arrester from damage when the continuous current is not breaking. The latter improves the usability of the protection device. A feature of the charging unit 21 in comparison with the analogous unit of the known device is that

that the current of the arrester 11 flows through the diodes of the bridge rectifier 24 and therefore there is no need for a shunt capacitor 15 diode, which has a known device.

A distinctive feature of the control unit 22 is its series connection with the charging unit 21. The control unit 22 can be switched on

only as shown in the drawing, and, for example, in series with the primary winding

transformer 27. In the control unit 22, instead of a variable resistor 28, an autotransformer or any known device with varying

5 AC resistance, such as a magnetic amplifier. The inclusion of the control unit 22 shown in the drawing is most appropriate since its circuits are under low voltage.

0 The differences between the control unit 23 are determined by the presence of a transformer 33 in it and the connection of its primary winding parallel to the input of the rectifier 24 of the charging unit 21. This transformer isolates

5 low-voltage circuits, which are necessary for control and protection, from high-potential converter power circuits. This isolation allows you to perform manipulations necessary for control (press buttons). Specified

0 the inclusion of the primary winding of the transformer 33 in combination with the considered distinctive features of the charging unit 21 makes it practically simple to implement quenching time control, which is an informatively important parameter of the bit. The control unit 23 may have several circuits that are similar to a circuit containing a isolation diode 39, a voltage relay 41, a storage capacitor 43 and a button 44, and several circuits similar to the circuit formed by the voltage relay 41 and the light indicator 45.

The drawing does not show the contacts of the voltage relay 40 involved in the control circuit of the oil switch 3 and the high speed switch 7.

The operation of the device is characterized by two modes: the normal operating mode, when the device is in the initial state, when dangerous transients in the power circuits of the converter are triggered and protects its equipment, and the mode in which the technical condition of the device is monitored protection, performing their own protective functions.

5 In the first mode, the proposed device operates as follows.

With disconnectors disconnected x 2 and 8, the voltage does not flow into the power circuit

converter and protection device. After switching on the disconnector 2 from busbar 1, a high voltage is applied to the primary winding of the step-down transformer 27 of the charging unit 21. From the secondary winding of this transformer, the reduced voltage goes to the primary winding of the step-up transformer 26. The increased voltage of its secondary winding is rectified by rectifier 24 . The rectified voltage charges the capacitor 15 through a resistor 25, which limits its charging current. The voltage of the capacitor 15 has the polarity shown in the diagram. The time constant of the circuit formed by the capacitor 15 and the resistor 16 is significantly longer than the period of the voltage supplying the rectifier 24. Therefore, the voltage of the capacitor 15 does not pulsate and the meter 20 indicates the magnitude of this voltage.

The AC voltage input to the rectifier 24 of the charging unit 21 is applied to the primary winding of the transformer 33 of the control unit 23. The secondary voltage of this transformer is rectified by rectifier 34. The rectified voltage is stabilized by the chain 35 and then supplied through a separating diode 38 to the voltage relay 40 and to the capacitor 42. This capacitor charges to the threshold voltage of the zener diode 37 of the chain 35, Voltage relay 40 is activated, changes the position of its contacts (not shown) and thus removes the prohibition on switching on the oil switch 3 and the on-speed switch 7

In this mode of protection device of the relay 30, the voltage of the control unit 22 is de-energized, its contacts are open, and a resistor 29 is inserted into the charging unit circuit. In the control unit 23, the voltage relay 41 is also de-energized and closes with its contacts the circuit of the indicator light 45, which is lit, indicating the presence of voltage in the charging unit 21 and the control unit 23.

When the switches 3 and 7 are off, the spark gap 12 of the discharge capacitor 11 through the diodes of the converter and the diode 14 applies the voltage of the capacitor 15. After the switches 3 and 7 are turned on, the capacitor 17 is charged through the diode 14 from the converter 5 to the amplitude value of its rectified voltage (voltages on tires 9 tons of a govaya substation). The resistor 19 limits the charging current of the capacitor 17 at the first moment after turning on the switches 3 and 7. The voltage of the capacitor 17 has a polarity, which is shown in the diagram.

When voltages are present on capacitors 15 and 17, their total voltage is applied to spark gap 12. In normal operation modes

the substation this voltage does not exceed the magnitude of the breakdown voltage of the arrester and in the control unit 23 the capacitor 42 is charged and the voltage relay 40 is turned on.

The charged state of the capacitors 15, 42 and the on position of the voltage relay 40 provide the voltage of the charging unit 21. If for some reason, for example, when the contact is lost, the voltage of the charging unit 21 disappears, then the capacitors 15 and 42 begin to discharge to press. The capacitor 15 is discharged through the resistor 16, the capacitors 42 through the winding of the voltage relay 40. After the termination of the charge of the capacitor 42, the voltage relay 40 is

energy stored in it continues to be in the on position for some time, then disappears and changes the position of its contacts (not shown), which leads to the opening of the switches 3 and 7, which relieve the voltage

0 from the power circuit of the converter of a govt substation and its removal from operation. Thus, the operation mode dangerous for the power equipment of the converter substation, when the voltage is

, - on the capacitor 15 is absent and the discharge voltage 11 can be triggered when an overvoltage occurs that exceeds the permissible level.

When appearing in power circuits, an overvoltage converter, in which

0 the sum of the instantaneous value of the rectified voltage of the converter 5 and the voltage of the capacitor 15 exceeds the breakdown voltage of the spark gap 12, the latter breaks through and creates a circuit for the flow of current between the poles of the rectified voltage of the converter 5. At the first moment after the breakdown of the spark gap 12, this current flows through a capacitor 15, which in this case is discharged to zero. After the capacitor 15 is completely discharged, the current from its circuit is transferred to the diodes of the rectifier 24 of the charging unit 21. During the flow of the current through these diodes, the voltage of the capacitor 15 does not vary in time and has a small value equal to voltage drop

The diodes of the two arms of the bridge are rectifier 24. The polarity of the voltage of the capacitor 15 is opposite to that shown in the drawing.

The magnitude of the current of the surge capacitor 11 is limited by the resistance of its resistor 13. The overvoltage energy at the first moment after the protection device trips is spent on recharging the capacitor 15, then dissipated in the resistor 13 of the discharge capacitor 11, released as heat. As a result of this, overvoltage is limited.

After limiting overvoltage, the surge voltage 11 breaks (dampens) the current accompanying it, which flows in its circuit under the action of the rectified voltage of the converter 5. At the time of the discharge of this current discharge 11, the voltage of the capacitor 15 has a small value and therefore to the spark gap 12 The discharge element 11 applies only the amplitude value of the rectified voltage of the converter 5, a lower voltage that acts on the spark gap 12 during normal operation of the converter. Further, the voltage of the charging unit 21 charges the capacitor 15. As this capacitor is charged, the voltage of the spark gap 12 increases and reaches the value that occurred before its breakdown during the appearance of overvoltage.

During the flow of the discharge voltage 11 through the diodes of the rectifier 24, it forms a short whip circuit for the secondary winding of the transformer 26 and its voltage is fully applied to the resistor 25. Therefore, starting from the moment of the occurrence of the discharge current in the rectifier 24 diodes , the voltage is removed from the primary winding of the transformer 33 of the control unit 23. The occurrence of the voltage on this winding corresponds to the termination of the suppression of the accompanying current when the current in the arrester circuit and, accordingly, in the diode circuit of the rectifier 24 stops. In the time interval when the transformer 33 does not receive voltage, the capacitor 42 is discharged through the winding of the voltage relay. Isolation diode 38 eliminates the influence of shunt circuits (light indicator circuit 45) on the discharge time of capacitor 42. If there is a disconnecting diode 38, the discharge time of this capacitor is determined by its capacitance and parameters (resistance, inductance) of the voltage relay 40, allows you to control the discharge time of the capacitor 42 and, accordingly, the flow time of the accompanying current in the circuit of the arrester 11 as follows. If during the flow of the accompanying current in the circuit of the discharge capacitor 11, the capacitor 42 does not have time to discharge before the voltage at which the voltage relay 40 disappears, then after removing the overvoltage and damping of the follower current discharge the traction substation continues to work, and the charge The unit 21 charges the capacitors 42 to a voltage corresponding to the initial state of the protection device. When the quenching process of the accompanying current discharges is tightened and, accordingly, the current flow time in the discharge circuit increases, the voltage of the capacitor 42 decreases to such a value that the voltage relay 40 drops and changes the position of its contacts (not shown). As a result, switches 3 and 7 remove the voltage from the power circuit of the converter substation and it is taken out of operation. Next, the accompanying current in the discharge circuit is stopped, the charging unit 21 charges the capacitors 15 and 42 to a voltage that corresponds to the initial state of the protection device, trips the voltage relay 40 and removes the prohibition to turn on the switches 3 and 7 of the converter substation and sootvetstv

of course, in bringing it to work.

0

The mode in which the technical condition of the arrester is monitored is carried out by performing the following operations.

5 By disconnecting the high-speed switch 7 operating on the load, the converter is turned to idle. At idle converter, its rectified voltage has a stable amplitude, non-changing shape and is formed

0 from a segment of sinusoids, the duration of which is determined by the rectification circuit (with 6- and 12-pulsating rectification, respectively, 60 and 30 degrees. El.). In this case, having the indications of a voltmeter 6, which measures the average value of the rectified voltage, it is possible by simple calculation to determine its amplitude value, which memorizes the capacitor 17 and which is the component of the spark gap 12, 11. The recalculation consists in that the readings of a voltmeter 6 with 6- and 12-pulsating rectification multiply, respectively, by 1.0472 and 1.0116.

Next, pressing button 44 causes the relay 41 to trip, the light indicator 45 goes out in the control unit 23. As a result, the capacitor 43 is charged to the threshold voltage of the zener diode 37. The capacitor 43 is chosen such that, in the presence of a separation diode 39, the effect of parallel circuits (chain 35 of stabilization, etc.), for voltage relay 41, the time delay for falling off corresponds to the characteristic value of the discharge current quenching time, 5 is an example of the average, maximum or minimum value of this time.

After that, pressing the button 32 triggers the relay 30, which, by changing the position of its contacts, shunts the resistor 29 of the control unit 22. The shunting of this resistor leads to an increase in the voltage at the input of the rectifier 24, the capacitor 15 remembers the new increased amplitude of this voltage and the voltage meter 20 increases its readings.

By performing the above operations, slowly and smoothly reduce the resistance of the resistor 28 until the spark gap 12 of the bit 11 is broken,

and observe the readings of voltmeters 6 and 20. The readings of the first voltmeter do not change, the second one increases. At the time preceding the breakdown of the spark gap 12 of the bit 11, the readings of voltmeters 6 and 20 are recorded and the readings of the voltmeter 6 are recalculated. By adding the recalculated readings (from average to amplitude) of the voltmeter 6 with the readings of voltmeter 20, the breakdown voltage of the spark span of the controlled discharge.

After the breakdown of the spark gap 12, the capacitor 15 is quickly recharged, a discharge current flows through the rectifier diodes, and as a result, the voltage is removed from the primary winding of the transformer 33 of the control unit 23. The resistance of the current-limiting resistor 13 and the capacitance of the capacitor 15 are selected in such a way that the time of its recharging is significantly less than the time of quenching of the discharge.

In this case, the time of breakdown of the spark gap 12 of the bit 11, which is the starting point of its quenching time, and the moment of relieving voltage from the control unit 23, used to determine quenching, are shifted in time significantly less compared to the quenching time. Therefore, if this condition is observed, the process of recharging the capacitor 15 does not affect the results of monitoring the quenching time of the surge voltage generator 11 by the control unit 23.

Starting from the moment of occurrence of the current of the discharger 11 in the diode circuit of the rectifier 24, the voltage is removed from the control unit 23 and the capacitors 42 and 43 of this unit begin to discharge through the windings of the voltage relay 40 and 41, respectively, the voltage relay 30 disappears and opens their shunt resistor contacts 29.

After a certain time (quench time) has passed, the pattern 11 suppresses the accompanying current. After that, the capacitor 15 is charged by the voltage of the charging unit 21. At the moment of the end of the charge of the capacitor 15, its voltage is less than that which was before the breakdown of the spark gap 12 as a result of overvoltage simulation, since after a breakdown into the winding circuit transformers 26 and 27, the resistance of resistor 29 was introduced. Therefore, after the end of the charge of the capacitor 15, the spark gap 12 does not penetrate again. In this way, multiple breakdowns of the spark gap 12, which are undesirable in the monitoring process, are eliminated.

The discharge of capacitors 42 and 43 continues until the voltage on the primary winding of the transformer 33 of the control unit 23 appears. With a constant circuit time, capacitor 15 is a resistor 25, much shorter discharge coil time, rectifying rectifier voltage

body 34, substantially greater than the threshold voltage of the zener diode 37, the moment of cessation of the current of the arrester, which is the end of the reference time of its quenching, almost coincides with the moment of the occurrence of voltage in the control unit 23 and with the moment of the end of the discharge of the capacitors 42 and 43. After that capacitors 42 and 43 begin to charge before the threshold voltage of the zener diode 37.

Thus, subject to certain requirements that are listed for the parameters of the elements of the charging unit 21 and the control unit 23, the time for the discharge of the discharge and the discharge time of the capacitors 42 and 43

5 have almost the same size. Therefore, if the time for quenching the discharge time exceeds the delay time required by the storage capacitor 43 of the voltage relay 41, this relay disappears and remains in this state after the voltage is restored in the control unit and the control indicator light 23 turns on. This indicates that for a controlled bit the quenching time exceeds a certain normalized value, for example, an average value for a certain type of glitter. The control system consists of several light indicators identical to the indicator 45 and several relays similar to relay 41 in the functions performed during the control process

0 and having different delay times, allows the determination of the time interval in which the quenching time of the controlled discharge is. For example, when using three relays with time delays corresponding to the minimum,

5, the average and maximum quenching time, the lighting of the light indicators of the three relays indicates that the quenching time of the controlled discharge exceeds the maximum value. When tanned light

0 is a relay indicator with a minimum time delay, the arrester quenching time is between the minimum and average values.

If the controlled discharge voltage has 5 unacceptably long quenching time, then during the breakdown of the spark gap of the discharge discharge by simulated overvoltage in the control unit 23, the voltage relay 40 disappears. In this case, as in the similar case of the converter operating mode, 0 its switch 3 is turned off and the voltage is removed from the power circuits of the converter.

When conducting the described counter-voltage, the voltage of the capacitor 15 changes only upwards in relation to 5 to its initial value in the operating mode. Therefore, the operations necessary for control are accompanied only by decreasing the pick-up setting over voltage.

protection devices (the difference between the breakdown voltage of the spark gap 12 of the discharge voltage 11 and the voltage of the capacitor 15 measured by the device 20) cannot damage the power equipment of the converter.

After completing the monitoring described, the voltage relay 41 can be in any position, the voltage relay 30 should be turned off. If, for some reason, for example, as a result of the erroneous pressing of button 32, the winding of this relay is under voltage, then pressing the button 31 releases the voltage from this winding. The need for this is caused by the fact that if you set the trigger point of the protection device when the voltage relay 30 is turned on, then after the first trip of the protection, relay 30 disappears and increases the trigger point of the protection device, which is undesirable.

Next, set the operation setpoint of the protection device based on the results of the control being performed. To do this, from the breakdown voltage of the spark gap of the discharge, which is measured during the control, subtract the required setpoint value and use the resulting difference of these voltages as the required voltage of the capacitor 15. By varying the resistance of the resistor 28 of the adjustment unit 22, the meter 20 corresponds to this voltage value.

Then, by turning on the high-speed switch 7, the idle converter is switched to the operating mode of the load supply.

Claims (2)

1. An overvoltage protection device for a converter of a direct current substation comprising an arrester with a current-limiting resistor connected to one output of the first storage capacitor shunted by the first discharge resistor, the other output of which is connected to one output of the converter output of the converter, charging unit, connected to the input busbars and made in the form of rectifiers and down and step-up transformers in series, one output of the last connection n with the first charge resistor, a diode, the conclusions of which are associated with the transducer and the surge arrestor, a control unit, configured as a relay in parallel with the voltage switched first storage capacitor and the first isolating diode differing 0 5 0 from 0 five 0 5 0 5 Moreover, in order to increase reliability, it is equipped with an additional transformer and an additional rectifier, voltage regulator in the form of a series-connected resistor and a zener diode, at least one additional voltage relay with a second storage capacitor connected in parallel and a series-connected second separation diode , at least one light indicator, a voltage control unit, a second storage capacitor with a shunting second discharge resistor Yes, and a second charge resistor connected in series with it, the other output of which is connected to the output of the arrester connected via a diode to another output of the converter, one output of which is connected to the common free output of the second storage capacitor and the second resistor of the discharge and one of the conclusions The output of the rectifier is a different output of which is connected to one output of the first storage capacitor, and the output terminals to the first charging resistor and another output of the step-up transformer, moreover, These input pins are connected to the primary winding pins of the additional transformer, which are the inputs of the control unit, the secondary coils of which are connected to the pins of the additional rectifier input, to the output pins of which a voltage regulator is connected, parallel to the zener diode of which , at least one additional voltage relay and at least one light indicator, and the outputs of the additional rectifier are connected to one of the terminals block rows voltage control, the other terminals of which are connected in series in one of the wires, binding transformers charging unit. 2. The device according to claim 1, characterized in that the voltage control unit is made in the form of series-connected DC and AC resistors, connected in parallel, opening and closing control buttons and a voltage relay connected in series, one closing contact of which is connected in series opening the control button, and the other parallel to the constant resistor, the free terminals of the resistors being the other terminals of the voltage regulating unit, and some The voltage inputs are the free output of the voltage relay and the total free output of the control buttons.