SU1705946A1 - Short-circuit shock protector - Google Patents

Abstract

The invention relates to electrical engineering. The purpose of the invention is to increase the efficiency of limiting cw currents by providing selective current limiting. The device allows to provide current limiting both at the short circuit on the 1ins supplying the high-voltage electric motors and at the short circuit in the external power supply system. In this case, the device facilitates the conditions for switching off the switching equipment of not only the individual engine, but also the group of switching devices of the power supply system. The selectivity of the current limiting allows you not to interfere in the mode of operation of those conductors, the motors of which in a particular short circuit mode do not have a large feeding effect of the short-circuit point. silt g (L

Description

The invention relates to electrical engineering, in particular to devices for limiting the impact current of a short circuit (short-circuit).

The aim of the invention is to increase the efficiency of limiting short-circuit currents. by providing selective current limiting.

FIG. 1 shows a block diagram of a short-circuit shock current limiting device {Fig. 2 is a block diagram of the thyristor key control unit; in fig. 3 - timing diagrams of the signals of the thyristor key control unit in normal and emergency modes; in fig. k - time diagrams of signals of the centralized control system.

Device for limiting the shock current short-circuit contains a step-down transformer 1 (Fig. 1), the high voltage winding of which is connected to the power supply system through the input switch 2, and the low voltage windings are connected to the first 7, second 8, third 9 and fourth 10 current conductors through low-voltage switches 3-6 Respectively. Motor load 11-12 is connected through switches 13 and I1 of the engines. with the first protected conductor 7. The motor load 15-16 is connected through the switches 17 and 18 of the engine with the second protected conductor 8. The motor load 19-20 is connected through the switches 21 and 22 of the engine with the third protected conductor 9. The motor load 23 is connected through switches 25 and 26 engines with the fourth protected current

with

Ј

0

317059 6

wire 10. At the power inputs of the first 7, second 8, third 9 and fourth 10 protected conductors, current sensors 27, j 28, 29 and 30 are connected, respectively, and voltage sensors 31 32, 33 and З1 are connected respectively to conductors. In addition, these conductors contain control units 35, 36, 37 and 38 for thyristor keys, as well as thyristor keys 39 0, 1 and

42, the first terminals of which are connected to the corresponding protected conductor, and the second terminals are grounded 15 through current-limiting resistances, d, 5 and. At the same time, the input of the thyristor switch of each conductor is connected to the second output of the control unit of the thyristor switch of this 20 conductor. The first and second inputs of each thyristor key control unit are connected respectively to the output of the current sensor and voltage of the current conductor, the third input is connected25 to the output of the centralized system

7 controls, and the first output - with one of the inputs last.

Centralized control system 47 for power on. The inputs of the differentiating unit 51, the dual differentiation unit 5, the first inputs of the third adder 58 and the power control authority 63 are combined and the first input of the thyristor control unit 37 is located. The output of the differentiating block 51 is connected to the inputs of the first block 53 through the first p-unit block 52 and a square is erected. The output of the latter is connected to the first input of the first adder. The output of the double-differentiation unit 5 is connected through the second pro- posal block 55 to the second input of the third adder 58 and to the two inputs of the second ejection unit 56 square. The output of the latter is connected by the second input of the first adder 5 The output of the first adder 57 is connected by cutting the square-root extracting unit 60 to the first input of the second adder 61, and the output of the third adder 58 through the rectifying circuit 59 to the second input of the second adder 6 the main input of the electronic key 65 through the threshold element 62 with tert

The laziness unit comprises an adder 8, a threshold jg input of the organ 63 of the direction of the power element 9 and the organ 50 of the time delay. The number of inputs of the adder 8 is equal to the number of protected conductors (in this case, four). At the same time, the inputs of the adder W are also the inputs of the centralized control system 7, and the output through the threshold element 9 is connected to the time-delaying organ 50. The output of the last one. The second input of the power control unit 63 is connected to the output of the memory circuit 6k, and the output to the control input of the electronic switch 35 65. The memory circuit input b1 is the second input of the thyristor key control unit 37. The output of the electric key 65 is the first output of the thyristor cell control unit 37.

Signap on inclusion. The inputs of the differentiating unit 51, the double differentiation unit 5, the first inputs of the third adder 58 and the power direction organ 63 are combined and form the first input of the thyristor key control unit 37. The output of the differentiating block 51 through the first proportional block 52 is connected to both inputs of the first block 53 of squaring. The output of the latter is connected to the first input of the first adder 57. The output of the double differentiation unit 5 is connected via the second proportional unit 55 to the second input of the third adder 58 and to both inputs of the second squaring unit 56. The output of the latter is connected to the second input of the first adder 57. The output of the first adder 57 is connected via the square root extraction unit 60 to the first input of the second adder 61, and the output of the third adder 58 via the rectifying circuit 59 to the second input of the second adder 61. The output of the latter is connected with the main input of the electronic key 65 and through the threshold element 62 with the third

input authority 63 direction of power. The second input of the power direction organ 63 is connected to the output of the memory circuit 6k, and the output is connected to the control input of the electronic key 65. The memory circuit input b1 is the second input of the thyristor key control unit 37. The output of the electronic key 65 is the first output of the thyristor key control unit 37.

This is the centralized output and is connected to the first input by the login of the control system 47.

The thyristor control unit 37 of the third protected conductor 9, as well as the rest conductors blocks 35 36 and 38, contains differential block 51, first proportional block 52, first square squaring block 53, double differentiation block 51, second proportional block 55, second block 56 squaring, first adder 57, third adder 58, rectifying circuit 59, square root extraction unit 60, second adder 61, threshold element 62, power direction organ 63 with circuit b of memory, electronic key 65, logic element t I 66, time delay authority 67, logical element OR 68 and formation circuit 69

45

50

55

The I66 combinator, the second input of which is the third input of the thyristor key control unit 37. The output of the Ibb logic element is connected to the first input of the OR 68 logic element, the second input of which through time delay 67 is connected to the output of the protection circuits of the motors of the protected current conductor, and the output is connected to the input of the turn-on signal 69. The output of the latter is the second output of the thyristor key control unit 37.

The blocks of the device can be obtained on the basis of the existing element base. The differentiation unit can be performed on a DC operational amplifier with constant current.

which is connected to the first log entrance

The I66 combinator, the second input of which is the third input of the thyristor key control unit 37. The output of the Ibb logic element is connected to the first input of the OR 68 logic element, the second input of which through time delay 67 is connected to the output of the protection circuits of the motors of the protected current conductor, and the output is connected to the input of the turn-on signal 69. The output of the latter is the second output of the thyristor key control unit 37.

The blocks of the device can be obtained on the basis of the existing element base. The differentiation unit can be performed on a DC operational amplifier with constant current.

a feedback resistor and an input capacitor. For a double differentiation unit, the indicated scheme is doubled. Proportional blocks can be made on the basis of an operational amplifier of direct current, at the input and in the feedback circuit of which a constant resistor is connected. Squaring blocks can be obtained on the basis of an analog multiplier with parallel-connected inputs. The square root extraction unit can be implemented on the basis of an operational amplifier with the inclusion of a multiplier in the feedback circuit. Threshold elements can be made on the basis of the comparator. The memory circuit can be implemented on the basis of a circuit using an RC circuit. The electronic key can be implemented on the basis of an analog key. Time delay organs can be implemented on the basis of an integral timer. Current sensors are current transformers, and voltage sensors are voltage transformers. The power direction organ must be fast-acting and can be

is generated in time, and at the output of this block, a signal (t) is formed, which enters the input of the second proportional block 55. At the output of the latter, a signal K2p2i (t) (K2 CfP2-) is formed, fed to the inputs of the second block 56 of squaring and at the second input of the third adder 58 At the output of the second block 56 of erecting a coadrat, a signal ЈKjpzi is generated (arriving at the second input of the first adder 57. At the same time, the total signal at the output of this block is equal to 4 rat of the amplitude Im of the current i (t). This signal is fed to the input of block 60 extracting the square root, at the output of which a signal 1 of the amplitude of the periodic component of the current i (t) is formed, arriving at the first input of the second adder 61. At the output of the third adder 58, the signal l (t) + K2p2i (L)} is input to the input rectification circuit 59. At the output of the latter, an input signal module i (t) + Ј2p2i (t) J is formed, equal to the aperiodic component of current i (t) and arriving at the second input

25

made on the basis of the known device of the second adder 61. The signal on the wiring circuit, for example, based on the power direction of the power supply system with current limitation.

The device works as follows.

First, we consider the operation of the thyristor key control unit 37 (Fig. 2). The signal i (t) from the current sensor 29 is supplied to the first input of the thyristor key control unit 37, where it branches into the differentiating unit 51, the double differentiation unit 5, to the first inputs of the third adder 58 and the power direction unit 63. In differentiating unit 51, the signal i (t) is differentiated in time, and at its output a signal pi (t) (pd / dt) is formed) received at the input of the first proportional unit 52. At the output of the last signal K, pi ( t) (K (), arriving at the inputs of the first squaring block 53, at the output of which a signal K, pi (t) 2 is formed. This signal arrives at the first input of the first adder 57. In the double differentiation block 5, the input signal is i (t) twice differential about 0

is generated in time, and at the output of this block, a signal (t) is generated, which enters the input of the second proportional block 55. At the output of the latter, a signal K2p2i (t) (K2 CXP2-) is formed, which is fed to the inputs of the second block 56 the input of the third adder 58. At the output of the second construction unit 56, a signal ЈKjpzi (t) J arriving at the second input of the first adder 57 is formed in the coadrat. At the output of this block, the total signal is equal to a quadrant of current i (t). This signal is fed to the input of the square root extraction unit 60, at the output of which a signal 1 of the amplitude of the periodic component of the current i (t) is formed, which is fed to the first input of the second adder 61. At the output of the third adder 58, the signal l (t) + K2p2i (L )} arriving at the input of the rectifying circuit 59. At the output of the latter, an input signal module i (t) + Ј2p2i (t) J is formed, equal to the aperiodic component of current i (t) and arriving at the second input

five

five

0

during the adder - there is a shock current iu In the normal mode, the current i (t) has only a periodic component with an amplitude defined by the load value of the conductor (Fig. 0 at t with t 0, where 70 is the dependence of the time variation of the signal i (t) ; 71 — time dependence of the K signal, p i (t); 72 — time dependence of the K2p2i (t) signal in normal mode). The aperiodic component of the current is absent, therefore, there is no signal at the second input of the second adder 61. At the same time, 5 the shock current iui is equal to the amplitude 1 of the current i (t) in the normal mode. This signal is fed to the inputs of the electronic key 65 and the threshold element 62. The value of the C-iB signal in this mode is 1 less than the threshold signal in the threshold element 62, therefore, at the output of the latter, the signal V is absent (Fig. ЗД, 1 at tt t0, where 73 is the dependence time variation of signal 7 time dependence of the change in time of the GKO signal + + K2p2i (t) l, 75 (time dependence of the signal of the DTV signal in the normal mode). For this reason not

0

the power direction organ 63 is turned on and there will be no signal at its output, the electronic key 65 will not be turned on, the signal C "to the first input of the thyristor control unit 37 and the first input of the AND 66 logic element will not arrive. Consequently, the intHe value will be transmitted to the centralized control system (Fig. 1). When the last control signal comes from the output of the logic element And 66, the V signal will not be

ten

The latter ensures the operability of the power direction organ with large voltage drops in emergency conditions. If the power direction changes, the signal Vu turns on the electronic key 65, and the signal 1c, the passage through it, goes to the first output of the thyristor control unit 37 and to the first input of the AND 66 logic element. When the Wave signal comes in, the third input of the block 37 control thyristor key and then to the second input of the logical

formed. If at this time also ts element I 66 at the output of the last

there will be no V-signal from the devices; a signal V is formed, which, in the engines 19 and 20 of the given one, arrives at the first input of the logical

protected conductor 9, then there will be no element OR 68. At the output of this

element, a signal V is formed, allowing the signal 69 to be turned on. At the output of the latter, a signal V is generated, which arrives at the second output of the thyristor key control unit 37.

VЈKA signal at the output of circuit 69 for25

and the signals V, Vg, VfcKA and the thyristor key will not turn on.

In emergency mode, both the periodic component of the current i (t) and aperiodic occur, therefore, at the second input of the second adder 6C, the signal i (t) + К2р 2.i (t) is zero (Fig. 3, O B, c, t when t te where 76 is the dependence of the time variation of the periodic component of the current i (t) i 77 is the dependence of the time variation of the aperiodic component of the current 30 the input of the time-period organ 67 i- (t) 78 is the dependence of the change in A long signal V $ is lost from the time of the current i (t) j 79 - the dependence of the protection roystviag, and at its output the shape of the signal 80 changes in time - depending The time variation of the signal (t), 81 is the dependence, the time variation of the signal 82 -; the time dependence of the signal i (t) K, p2i (t) J in emergency mode). The magnitude of the shock current C is determined before its occurrence, i.e., | d0 signal Vf, triggering circuit 69 is predicted. If you exceed the world of the signal to turn on. Scrap 1 "4d values of the threshold signal for the output of the latter generates a signal Uzdv threshold element 62, the output Vj arriving at the second output of the block produces a signal Vj, 37 controlling the thyristor key, arriving at the third input of the organ 63 d $ the duration of the signal VgKA the direction of power and triggering Tak e, as well as its V signal (Figs. 3, 6 with, where 83 is the time dependence of the signal ia-; 8C is the time dependence of the signal V $ 0; 85 is the dependence of the change in time signal V, in emergency mode). At the output of the latter, the VH signal is formed only if the direction of power through the current sensor 29 is reversed. The signal u (t) is supplied from the voltage sensor 33 to the second input of the power direction organ 63 through the circuit 6 of the memory. A signal on switching on will also be formed when the protection devices of motors 19 and 20 of this conductor 9 are triggered. At the same time,

A short pulse of the V signal is detected. The width of this pulse is equal to the off time of the switches 21 and 22 of the Switching motors 19 and 20, respectively. The signal V is fed to the input of the logical element OR 68, the output of this element is formed

55

Let us now consider the joint operation of the thyristor key control units 35, 36, 37 and 38 together with the centralized control system U7 (Fig. 1). When k.z. at point K1 of the external power supply system, the step-down transformer 1 must be disconnected from the damaged one and connected to the backup line. However, the currents from the motors 11, 12, 15, 16, 19, 20, 23, and 2k feed the point to. deteriorate the conditions for disconnecting the input switch 2. In this mode, the currents

The latter ensures the operation of the power direction organ at large voltage drops in emergency conditions. If the power direction has changed, the signal Vu includes the electronic key 65, and the signal 1c, the passage through it, goes to the first output of the tirris control unit 37 and to the first input of the AND 66 logic element. When the Wave signal comes in, the third input of the control unit 37 thyristor key and then to the second input of the logical

element is formed, the signal V, which starts the circuit 69 forming a signal to turn on. At the output of the latter, a signal V is generated, which arrives at the second output of the thyristor key control unit 37.

VЈKA signal at the output of 69 odds

The time delay organ input 67 will receive a long signal V $ from the protection devices, and at its output a form signal Vf triggering the turn-on signal formation circuit 69. At the output of the latter, a signal Vj is generated, which arrives at the second output of the thyristor key control unit 37, and the duration of the signal VgKA is Tak e, as well as the signal V

the activation signal will also be formed when the protection devices of the motors 19 and 20 of the current conductor 9 are triggered.

The input of the time-delaying organ 67 will receive a long signal V $ from the protection devices, and at its output a form-signal Vf triggering the turn-on signal 69 formation circuit. At the output of the latter, a signal Vj is generated, which arrives at the second output of the thyristor key control unit 37, and the duration of the signal VgKA is Tak e, as well as the signal V

A short pulse of the V signal is detected. The width of this pulse is equal to the off time of the switches 21 and 22 of the Switching motors 19 and 20, respectively. The signal V is fed to the input of the logical element OR 68, the output of this element is formed

The time delay organ input 67 will receive a long signal V $ from the protection devices, and at its output a form signal Vf triggering the turn-on signal formation circuit 69. At the output of the latter, a signal Vj is generated, which arrives at the second output of the thyristor key control unit 37, and the duration of the signal VgKA is Tak e, as well as the signal V

Let us now consider the joint operation of the thyristor key control units 35, 36, 37 and 38 together with the centralized control system U7 (Fig. 1). When k.z. at point K1 of the external power supply system, the step-down transformer 1 must be disconnected from the damaged one and connected to the backup line. However, the currents from the motors 11, 12, 15, 16, 19, 20, 23 and 2k, feeding the point k., Worsen the conditions of the disconnection of the input switch 2. In this mode, the currents

317

through current sensors change their direction to the opposite, and the signals taken by these sensors are processed in blocks 35, 36, 37 and 38 of the control of thyristor keys From the output of each of these blocks, the signal to the input of the adder 48 of the centralized control system 47 comes in if the expected shock current of the corresponding current is greater than the threshold value. Let this condition be met for all four conductors and at the first outputs of all control units.

thyristor keys have signals iy, (Fig. 4a, S, 6,2), where 86 is the dependence of the time variation of the signal iu, 1, 8 is the dependence of the time variation of the signal iy2 88 is the dependence of the time variation of the signal iu "; 89 - dependence of the time variation of the signal Ts.v in emergency mode). Adder 48 summarizes the shock currents of the individual conductors, the sum of which iu is fed to the input of the threshold element 49 (Fig. 4a, where 90 is the dependence of the change in time of the signal in, 91 is the level of the threshold signal M in emergency mode). If the total shock current iu is greater than the threshold value, then the signal Vf is fed to the input of time-delaying organ 50. The latter has a very short delay and is intended for detuning from switching current surges in transient conditions. At its output, a signal Vu, is formed, which is fed to the third inputs of the thyristor key control units 35-38 (Fig. 4e, where 92 is the dependence of the change in the signal time Vu in emergency mode). At the same time, only those of thyristor keys 39-42 will be generated at the second outputs of only those blocks 35-38, VjKftn signals will be generated, from the control blocks of which information has been received to the adder 48. As a result, the shock current will be limited, which greatly facilitates disabling the down-voltage transformer 1 input switch 2 from the damaged line When kz. at point K2 on the third cable 9, the directions of the currents are changed through the current sensors 27, 28 and 30 and remain unchanged through the current sensor 29. Therefore, the blocks 35, 36 and 38 control thyristor keys are triggered

ten

0

five

0

five

five

under the same conditions as when k. at point K1, and the thyristor key control unit 37 does not work. This is necessary because turning on the thyristor key 41 will increase the current flowing through the linear switch 5 and worsen the conditions for turning it off. In addition, the currents of the motors 19 and 20 do not affect the conditions for switching off the linear switch 5. Otherwise, the operation of the device is similar to its operation at a short circuit. at point 1 (1.

When k.z. at the short-circuit point, the thyristor key control blocks 35–38 operate in the same way as in the short-circuit. at point K2. However, the high-speed protection of the motor 19, the signal Vi with which (Fig. 2) enters the time-delay organ 67, of the thyristor key control unit 37, will work. In this case, the output of block 69 receives the V8Krt signal to turn on the thyristor key 41. The joint operation of blocks 67, 68 and 69 is described above. In this case, the shock current is limited both from the conductors 7, 8, 10, and from the engine 20, which improves the conditions of the shutdown of the switch 21 of the engine 19. In general, the number of simultaneously protected conductors can be any, while the number of these conductors determines the number of inputs of the adder 48.

Mathematically, the operation of the thyristor key control unit 37 is described as follows.

In normal operation, the current i (t) is equal to:

i (t) i sinoot, and in emergency mode

i (t). I sinCOt + i

(O t

(2)

ao - j

where T is the amplitude of the periodic component of the current,

the initial value of the aperiodic component of the current.

Cho

In normal mode, with differentiation and double differentiation, we obtain

45

pi (t) G) ImcusG3t 55 p2i (t) -W I sinGDt

(3)

Multiplying the first equation of system (3) by K, (K, (), and the second by K2 (K2 “CO), we get

 I cosCDt

(four)

I sinOOt fn

We square and add the equations of the CO system:

P, 5)

K, pi (t) "+ (t)

 I (cos Wt sin2 (Ot)

in

Removing the positive quadratic root from Eq. (5), we obtain Irt in its right side.

Next, add equation (1) and the second equation of the system (0:

„SinG3t i (t)

 K2p i (t) O

Lm

- Imsin (x) t Then the shock current is: 1GO + 0 - I,

(6)

iyV Im + u Ы- (7) In emergency mode, with differentiation and double differentiation, we get

pi (t)

0) IwcoS (Ot - 1 i-Q0e T

 - (j3 Imsin (Ot

h

lo.o "

Substituted in the system of constant time

X

T a - 1

(JR is the best

(8) expression

(9)

pi (t) - (Od coecOt - |

i (t)

- (0 (IjBinGi) t w

What's

R x

i t

)

Rz. t

 xyou (10)

Since in the power supply system the reactance X is significantly greater than the active resistance R, the second term in equation x45 of system (10) can be neglected. Then equations (3) - (5) are also valid for emergency mode.

Next, add equation (2) and the second equation of the System (M:

50

i (t) + K2p2i (t) I sinQt +

-i1t (11)

 WOWOT Winc.

Then the shock current at time T is equal to: W

hp

1a.ve

(12)

th

ten

15

20

25

eight)

not

ten

 )

15

ten

h45 and

50

)

55

The proposed device, in comparison with the prototype, provides a more efficient, high-speed current-limiting shock current short-circuit, consisting in the fact that the current limitation is provided as in short-circuit current. on the conductors supplying high-voltage motors, and at k.s. in the external power supply system. At the same time, this device in emergency mode facilitates the conditions for shutting down an entire group of switching devices, which increases the durability of these devices, thereby increasing the reliability of power supply. In addition, this device allows, due to the selectivity of the operation of the thyristor switches of individual conductors, not to interfere with the mode of operation of those conductors whose motors are in a particular short-circuit mode. do not have a large feeding effect point k.z.

Claims (1)

Invention Formula A device for limiting the shock current of a short circuit of a power supply system consisting of conductors with a motor load connected to a power source, containing a thyristor switch with a series-connected current limiting resistor, designed to be connected to one of the conductors with a motor load, a current sensor of the conductor, a control unit a thyristor key, made in the form of a differentiating unit and a double differentiation unit, whose inputs are interconnected and connected The output of the differentiating unit is connected to the current sensor through a serially connected first proportional unit and a first squaring unit to the first input of the first adder, the output of a double differentiation unit is connected via a serially connected second proportional unit and a second squaring unit to the second input of the first adder, and the output of the first adder is connected via a square root extraction circuit to the first input of the second adder, the first input of the third adder is connected to the sensor t the second input is connected to the input of the second squaring unit, and the output is connected via | cutting the rectifying circuit to the second input of the second adder, the output of which is connected to the input of the threshold element 5, is characterized in that, in order to increase the efficiency of limiting short-circuit currents. By providing selective current limiting, a thyristor key with a current-limiting resistor, a current sensor and a thyristor key control unit are installed on the other conductors, each current lead is additionally equipped with a voltage sensor, and the power direction organ is added to the thyristor key control block 5 with a memory circuit, an electronic key, a logical element AND, a logical element OR, and a time delay organ, the first inputs of the power direction organ being the third The adder, the inputs of the differentiating unit and the double differentiation unit are combined and form 25 the first input of the thyristor key control unit connected to the current sensor, and the second input of the power direction organ is connected to the output of the memory circuit, the input of which is the 30th second input of the thyristor key control unit and connected to a voltage sensor, wherein the third control input of the power direction organ is connected to the output of the Threshold element, and the output is connected to the control input of the electronic key, the main input of which is connected to the input of the second threshold element, in turn, the output of the electronic key is the first output of the control unit of the thyristor key and connected to the first input of the logical element AND, the second input of which is the third input of the logical element OR, a second input through which the holding body is connected to a terminal for connecting to the protection circuits of the electric motors of a given conductor, and the output is connected to the input of the switching signal formation circuit, while the output of the latter is the second output of the thyristor key control unit and is connected to the thyristor key control circuits, the device also further comprises a centralized control system including an accumulator, a threshold element and a time delay organ, the inputs of the adder being inputs of the centralized control system and connected to the first outputs of the control modules of the thyristor keys of the conductors, and the output of the adder is connected via a threshold element to the time delay authority, the output of which is a yield of a centralized control system and is connected to the third input keys thyristor control units protected TO- JKonpovodov. RG five -PHHZ Ј-№Ј} Uh I  g; about. about. S ". about in and 2 C-C gn-I PJ FIG. four