RU102843U1 - TRANSVERSE CAPACITY COMPENSATION DEVICE - Google Patents

Abstract

 A transverse capacitive compensation device in an AC traction network containing a single-phase capacitor bank connected to the buses through a first switch with a drive, a reactor for limiting resonance phenomena, the first terminal of which is connected to a capacitor bank, the second terminal is connected to the first terminal of the second switch with a drive and the anode of the power diode, the cathode of which is connected to the first terminal of the third switch with the drive, and the second terminals of the second and third switches with the drives are connected to the ground, characterized in that an additional resistor with a small resistance value is introduced into it, one terminal of which is connected to the second terminal of the damping resistor, and the second terminal is connected to ground, two circuits are connected in parallel with the additional resistor, the first voltage sensor and the first low-current diode are connected in series and the first low-current switch connected between the cathode of the diode and the ground, in a different circuit, a second voltage sensor, a second low-current diode and a second low-current switch connected m Between the diode anode and ground, the first low-current switch is controlled through the pulse duration limiter and the first timer by the first RS-trigger, the S-input of which is connected to the Start button, and the R-input is connected through the fourth timer to the Stop button, the output of the first voltage sensor is connected to The S-input of the second RS-flip-flop, the output of which controls the second low-current key, the output of the second voltage sensor is connected to the S-input of the third RS-flip-flop, the output of which is controlled by the second switch with the drive through the third timer and the third

Description

The utility model relates to the electric power industry, in particular, to transverse capacitive compensation devices in a traction AC network of 25 kV and 2 × 25 kV systems.

A device for lateral capacitive compensation in a traction AC network of 25 kV [1, Fig. 9], comprising a single-phase capacitor bank connected to the buses through a first switch with a drive, a reactor for limiting resonance phenomena, a damping resistor shunted by a second switch with a drive, and connected by one terminal to the reactor, and the other terminal to earth.

In [2, 3], it was proposed that shunt resistor be additionally shunted with a thyristor key, which shunts the resistor when the KU is switched to zero current, for effective damping of current and voltage surges during switching KU (switching on / off).

In [4, 5], a simpler device was proposed compared to a thyristor switch - a hybrid switch, which can also shunt a resistor to zero current. To do this, instead of the thyristor switch, a third switch with a power diode connected in series is connected.

We accept [5, Fig. 1] for the prototype.

So, we consider a transverse capacitive compensation device in an AC traction network, which contains a single-phase capacitor bank connected to the buses through the first switch with a drive, a reactor for limiting resonance phenomena, the first terminal of which is connected to the capacitor bank, the second terminal is connected to the first terminal of the damping resistor, as well as to the first output of the second switch with the drive and to the anode of the power diode, the cathode of which is connected to the first output of the third switch with the drive, the second s second and third breakers with drives connected to the ground.

The second and third circuit breakers with drives together with a power diode form a hybrid circuit breaker according to the prototype [5].

The disadvantage of the prototype is as follows. In [5] they focus on high-speed switches (in [5] they are called switches), the turn-on time of which is less than 10 ms. However, industrial switches, such as the BB / TEL-10 vacuum circuit breakers, have a trip time of 70 ms.

Therefore, the procedure for switching switches adopted in the prototype is unacceptable for switches with a trip time of more than 10 ms. In particular, in [5], after closing the contacts of the third circuit breaker, it is proposed to give a switching command to the drive of the second circuit breaker. When the second switch is turned on for more than 10 ms, this can lead to a break in the current in the circuit of the third switch with subsequent unacceptable surges of current and voltage in the switchgear.

The purpose of the proposed solution is to increase the reliability of the KU when switching with switches manufactured by the electrical industry, whose own turn-on time exceeds 10 ms.

This goal is achieved by the fact that in the transverse capacitive compensation device in the AC traction network, containing a single-phase capacitor bank connected to the buses through the first drive switch, a reactor for limiting resonance phenomena, the first terminal of which is connected to the capacitor bank, the second terminal is connected to the first the output of the damping resistor, as well as the first output of the second switch with the drive and the anode of the power diode, the cathode of which is connected to the first output of the third switch with the drive m, and the second terminals of the second and third circuit breakers with drives are connected to ground, an additional resistor with a low resistance value is introduced, one terminal of which is connected to the second terminal of the damping resistor, and the second terminal is connected to ground, two circuits are connected in parallel with the additional resistor, in one circuit the first voltage sensor, the first low-current diode and the first low-current switch connected between the cathode of the diode and the ground are connected in series, the second voltage sensor is connected in series in another circuit, the second weak a low-current diode and a second low-current switch, connected between the diode anode and ground, the first low-current switch is controlled through a pulse-width limiter and a first timer by the first RS-trigger, the S-input of which is connected to the Start button, and the R-input is connected through the fourth timer to the button Stop, the output of the first voltage sensor is connected to the S-input of the second RS-trigger, the output of which controls the second low-current key, the output of the second voltage sensor is connected to the S-input of the third RS-trigger, the output of which controls the second lyuchatelem driven by a third timer and a third switch driven by a second timer stop button is connected to the R-inputs of the second and third RS-flip-flops, and the output of the first RS-flip-flop controls the first switch to the actuator.

Figure 1 shows the structural diagram of the device.

The device comprises a first switch 1 with a drive, a capacitor 2 for reactive power compensation, a reactor 3, a damping resistor 4, an additional resistor 5 with a low resistance value, the first voltage sensor 6, the first low-current diode 7, the first low-current switch 8, the second voltage sensor 9, the second low-current diode 10, the second low-current switch 11, the power diode 12, the third switch 13 with the drive, the second switch 14 with the drive, the first RS trigger 15, the second RS trigger 16, the third RS trigger 17, the Start button 18, the Stop button 19, first 20, second 21, third 22, fourth 23 timers and a pulse width limiter 24.

The device operates as follows.

In the initial state, before turning on the installation, all RS-triggers are in the zero (reset) state: the voltage at their direct outputs has a low potential, i.e. on all direct outputs of RS-flip-flops, the signal is logic zero. There are no signals at the inputs of switches 1, 13, 14 and low-current switches 8 and 11, and switches 1, 13, 14 and low-current switches 8 and 11 are in the off state.

When a single signal from the Start button 18 or from the automatic control system to the input S of the first RS-trigger 15 is applied, this trigger switches from the zero state to the single state. At its direct output, signal 1 appears, which turns on the first switch 1.

After turning on the switch 1, a transient begins in the power circuit, consisting of a capacitor 2, an inductive reactor 3, a damping resistor 4 and an additional resistor 5, during which the capacitor 2 is charged to a voltage that exceeds the amplitude value of the supply voltage by about 1.1 times. The damping resistor 4 limits the amplitude of the current and the amplitude of the voltage across the capacitor 2. After the capacitor 2 is charged to the above voltage, and this happens, as shown by the authors, after two full half-periods of the supply voltage (0.02 s), the damping resistor 4 is no longer required and should be shunted, providing normal mode of installation of reactive power compensation. Shunting of the ballast resistor, so as not to cause large overvoltages on the capacitor 2, as shown by the authors, should be done at the moment the current passes through zero.

The passage of current through zero is determined in the proposed device as follows. We call the half-period of the current, the polarity of which coincides with the conductive direction of the power diode 12 and, accordingly, the low-current diode 7, the positive half-period, and the opposite half-cycle, the polarity of which coincides with the conductive direction of the low-current diode 10, negative.

After a time equal to or more than (0.02 + Δt) s, where Δt is the response time of the first power switch 1, a single signal appears at the output of the first timer 20 and a short-term signal with the duration of several half-periods of the supply voltage is output from the output of the pulse duration limiter 24 the control input of the first low-current key 8 and the key 8 is turned on. The limitation of the duration of the pulse supplied to the control input of the key 8 is necessary so that the key 8 could work only for a short time after turning on the device. Later in the process, the key 8 remains in the off state.

The inclusion of key 8 can occur in any half-cycle. If the inclusion of the key 8 occurred in the negative half-cycle, then the low-current diode 7 blocks the operation of the voltage sensor 6, and it can only work in the next - positive half-cycle. If the key 8 closes in the positive half-cycle, then the voltage sensor 6 will work immediately in the same positive half-cycle. Thus, the voltage sensor 6, regardless of which half-cycle the key 8 is switched on, always works in the positive half-cycle. Therefore, the signal from the output of the first voltage sensor 6 is fed to the input S of the second RS trigger 16 always in the positive half cycle and the low-current switch 11, to the input of which the signal is supplied from the output of the second RS trigger 16, always turns on the circuit with the voltage sensor 9 precisely in the positive half cycle. The circuit with the voltage sensor 9 is prepared for operation, but the second sensor 9 is blocked, it cannot work, since the diode 10 does not pass current into the positive half-cycle. The second voltage sensor 9 will work at the beginning of the negative half-cycle.

Thus, the second voltage sensor 9 always trips at the beginning of the negative half-cycle. This ensures the synchronization of switches 13 and 14 with the drives, as will be shown below.

Note that the additional resistor 5 can be replaced by a current transformer with a resistor at the terminals of the secondary winding to power voltage sensors 6 and 9.

Specially conducted studies showed sufficient stability of operation of switches 13 and 14 (BB / TEL-10 switches were used): the maximum spread in turn-on time was -0.6 ms. This is due to the presence of a voltage stabilization device in the control unit of the circuit breaker drive. When the temperature changes (from -30 to +30), the spread will increase, but in any case it will not exceed ± 3 ... 4 ms.

Thus, if it is noted that the circuit breaker will turn on in the middle of the half-cycle, then the spread of the switching time on the half-cycle can be assumed to be ± 5 ms. Therefore, the indicated 3..4 ms fit into the allowable 5 ms. This configuration principle is taken into account in the operation of the device, as shown below.

The signal from the output of the second voltage sensor 9 sets the third RS trigger 17 to a single state and the signal from the output of the trigger 17 is fed to the inputs of the second 21 and third 22 timers. The time delay of the second timer 21 is selected so that the third switch 13 is turned on in the middle of the negative half-cycle. It is such a time delay of the second timer 21 that is selected from those considerations so that a deviation from the turn-on time of the second power switch would not cause the switching output to go beyond the negative half-cycle. For example, if the time delay of the timer 21 is zero, then when the switch 13 is turned on for 70 ms, the switch 13 will always turn on after 7 half-cycles, i.e. at the beginning of a positive half-cycle, which is undesirable, since taking into account the variation in the response time may turn on at maximum current. A time delay of 0.015 will shift the moment the circuit breaker 13 is turned on by one and a half periods to the lag side and the turn-on will occur in the middle of the negative half-cycle. For a different switch time, a different setting is required. Thus, taking into account the deviation of the turn-on time of the second power switch, the moment of its turn-on does not go beyond the negative half-cycle. So, the switch 13 closes its contacts in the negative half-cycle and prepares a circuit with a power diode 12, shunting the damping resistor in the positive half-cycle. This circuit cannot operate in the negative half-cycle, since the flow of current into the negative half-cycle is blocked by the power diode 12. As soon as the current changes polarity and passes through zero, i.e. a positive half-cycle of the current occurs, the current begins to flow through the power diode 12, bypassing the damping resistor 4.

Simultaneously with the signal being supplied to the second timer 21, a signal is also sent to the third timer 22. The time delay of the third timer 22 is selected by the half-period value, i.e. 0.01 s more than the setting of timer 21. This means that after the switch 13, in the middle of the next positive half-cycle, the second switch 14 is turned on and the damping resistor 4 is bridged. Thus, the shunt of the ballast resistor occurs at the moment the current passes through zero. The spread of the response time of the switches 13 and 14 within no more than ± 0.005 s does not cause the deviation of the shunting process of the damping resistor 4 from the optimum. Indeed, the response time of the switch 13 can be any, as long as it fits during the negative half-cycle. The response time of the switch 14 can also be any, as long as it fit during the positive half-cycle when the power diode 12 is conducting. In order for the switch 13 to have a specified margin in response time in the negative half-cycle, the inclusion of two branches with low-current diodes and the timer 22 enables the switch 13 to be turned on in the middle of the negative half-cycle.

Thus, additional low-current diodes and timers compensate for the imperfection of circuit breakers with a significant turn-on time; compensate for the variation in the operating time of the switches in when the ambient temperature changes and depending on their adjustment and mechanical characteristics, and the power diode 12 makes the circuit with the switch 13 synchronized with the current of the transverse capacitive compensation device

Disconnecting the device is as follows. When a single signal is received from the Stop button 19 or from the control system, the input recovery signals of the second and third RS flip-flops 16 and 17 receive single triggering signals and the RS flip-flops 16 and 17 go from the single to the zero state and the second and third switches 14 and 13 are turned off . The low-current switch 8 also cannot turn on, since the signal from its input has been removed by the pulse width limiting device 24. A damping resistor 4 is included in the power circuit, which consists of a series-connected capacitor 2 and reactor 3. The presence of a damping resistor facilitates the operation of the first power switch 1 when the capacitive current of the installation is turned off. After a period of time sufficient to turn off the switches 13 and 14, a signal appears on the output of the timer 23 and the first RS trigger 15 goes into zero state and the switch 1 turns off the installation. The circuit is initialized and ready for a new start, after which the processes will be repeated in the sequence already described above.

Technical appraisal and economic advantage of the Utility model is determined by the increased reliability of the transverse capacitive compensation device.

Information sources

1. Borodulin B.M., German L.A., Nikolaev G.A. Condenser installations of electrified railways. - M.: Transport, 1983 ,. -183

2. Application for invention No. 2009104683 of 02/11/2009. The device of transverse capacitive compensation (authors Serebryakov A.S. and German L.A.). Positive decision 04/15/2010.

3. German L.A., Serebryakov A.S. Adjustable lateral capacitive compensation for traction AC networks. Electro No. 6 2009, from 29 - 35.

4. Utility model No. 66602. (application dated 05/02/2007) Device for controlled switching of capacitor banks.

5. Alferov D.F., Akhmetgareev M.R., Budovsky A.I. and others. Hybrid switch with controlled switching for circuits with capacitor banks. Electrical Engineering No. 32010, p. 49-56.

6. Power equipment of traction substations of railways (collection of reference materials) of JSC Russian Railways PKB for electrification of railways. M.6 "TRANSISDAT", 2004 - 384 p.

Claims (1)

A transverse capacitive compensation device in an AC traction network, comprising a single-phase capacitor bank connected to the buses through a first switch with a drive, a reactor for limiting resonance phenomena, the first terminal of which is connected to a capacitor bank, the second terminal is connected to the first terminal of the second switch with a drive and the anode of the power diode, the cathode of which is connected to the first terminal of the third switch with the drive, and the second terminals of the second and third switches with the drives are connected to the ground, characterized in that an additional resistor with a low resistance value is introduced into it, one terminal of which is connected to the second terminal of the damping resistor, and the second terminal is connected to ground, two circuits are connected in parallel with the additional resistor, the first voltage sensor and the first low-current diode are connected in series and the first low-current switch connected between the cathode of the diode and the ground, in another circuit, a second voltage sensor, a second low-current diode and a second low-current switch connected m Between the diode anode and ground, the first low-current switch is controlled via the pulse duration limiter and the first timer by the first RS-trigger, the S-input of which is connected to the Start button, and the R-input is connected through the fourth timer to the Stop button, the output of the first voltage sensor is connected to The S-input of the second RS-flip-flop, the output of which controls the second low-current key, the output of the second voltage sensor is connected to the S-input of the third RS-flip-flop, the output of which is controlled by the second switch with the drive through the third timer and the third switch with the drive through the second timer, the Stop button is connected to the R-inputs of the second and third RS-triggers, and the output of the first RS-trigger controls the first switch with the drive.