SU1573497A1 - Device for protection of electric circuit from damage - Google Patents

Abstract

This invention relates to electrical engineering, in particular, to relay protection devices against short circuits and leakage currents. The purpose of the invention is to increase the reliability of operation by improving the accuracy of measurement of monitored parameters. This goal is achieved by measuring the average values for a given integration time and periodically zeroing the integrators, introducing the measurement of network parameters and calculating the active component of leakage resistance for a specific network length. 1 il.

Description

The invention relates to electrical engineering and can be used to protect electrical networks with insulated neutral from leakage currents and short circuits, including for mining machines with an adjustable electric drive.

The aim of the invention is to increase the reliability of operation by improving the measurement accuracy and controlled parameters.

The drawing shows a diagram of the device

The device contains a source of operating voltage of alternating current with an isolation transformer at the output, mains voltage sensors 2 and load current 3, the first 4 and second 5 keys, the first 6 and second 7 integrators, the first 8 and second 9 elements of MEMORY, installation unit 10 in O, trigger 11, pulse shaper 12, pulse divider 13, splitter amplifier unit 14, display module 15 and connection 16, load resistor 17, third 18 and fourth 19 integrators, first 20 and second 21 threshold elements, first 22, second 23 and third 24 dividers n apr, the first 25 and second 26 adders, the first 27 and second 28 sets of settings, multiplier 29, reference element 30, element 31, mains voltage sensors 32 and load current 33, power source 34 — controlled rectifier, output Executive unit 35, diode 36, resistor 37. In the drawing, the resistance RM of the insulation of the cores of the cable relative to the earth, capacitance CJ. lived

sl vi

with

Ј

cable to earth, insulation resistance R and capacitance C between cable power conductors, resistance LKS of the network section & 1, electric motor 38 direct current, shunt electric motor 39 - semiconductor diode

Source 1 operating voltage has a transformer output

The first output winding of the isolation transformer through the second switch 5 is connected to the conductors of the power network. The output parameters of this source are measured by the sensors of the operating voltage 2 and current 30 The second switch b is controlled by the separation and amplification unit 14 o

The first integrator b is used to sum up the load current of the operating voltage generator ia for a specified period of time determined by the time delay t (created by the sequentially connected pulse generator 12 and the pulse divider from its first output. The delay t value for increasing the measurement reliability can be taken from units to tens of periods of network or operating voltage.The first key 4, when opened, connects the output of the first integrator 6 to the input of the first SAM element TH 8, which serves to memorize the magnitude of the current from the output of the first integrator L0 The second element MEMORY 9 serves to memorize the output voltage of the operational generator 10 The second integrator 7 serves to sum the signal proportional to the magnitude of the total (active and capacitive component) leakage current generated a power source 37 in a controlled geti. The third integrator 18 serves to gum the load current of a violet source 34 ". The fourth integrator 19 serves to sum the signal proportional to ionalnogo output AC voltage of the power source of the P-LCA 34 and summation is performed for a period of time t, given by divider 13 second pulses with its vyhodao

The setup circuit 10 in O serves for the initial setup at zero

five

0

five

0

five

five

0

five

The new state of the integrators, the memory elements and the trigger 1 "The latter determines the operating mode of the separation and amplification unit 14 and the elements And 31"

A pulse driver 12 and a pulse divider 13 serve to form a time interval t during which the reference voltage source is connected to the network, and a time interval t for which the load and leakage currents in the power network are measured. The introduction of a single-periodic rectifier with a load resistor in the input circuit of the pulse shaper allows one to obtain a time delay that is a multiple of an integer number of operating voltage periods.

The separation and amplifying unit 14 is used for matching the output circuit of the trigger 11 with the input circuits of the second key 5 and galvanic isolation between the high-voltage circuits of this key and the low-voltage control circuits

The display unit 15 provides service personnel with information on the operation of protection in case of emergency operation0

The connection unit 16 performs the functions of separating the power and measuring circuits of protection against current leakage0 The load resistor 17 is the measuring element of the leakage current of the power source 34 to the ground0

The first threshold element 20 serves to set the trigger threshold corresponding to the magnitude of the operational current in the event of a short circuit in a de-energized power network. The setting of the second threshold element 21 corresponds to the triggering level of the protection against leakage current 4 to ground 0

The first voltage divider 22 serves to calculate the magnitude of the resistance of the load circuit of the operational generator 1 o

The second voltage divider 23 calculates the short-circuit protection operation setpoint in the power network corresponding to the minimum value of the short-circuit current at the effective voltage at the output of the power source 340 The third voltage divider 24 is used to calculate the complex leakage resistance to earth in the power elements

network o The first adder 25 is used to calculate the value of the conductor resistance of the power cable taking into account the resistances of the second switch 5 and the power diodes 39, the values of which are predetermined and entered into the first block 27 of settings, i

The multiplier 29 with the second setting block 28 is used to calculate the capacitive component of the leakage resistance of the power network elements to ground. In the block 28 of the settings entered haraksoteristika power cable Xtl./R

K YES

Yc

capacitive X response

and the active Rc components of the kilometer resistance of the power cable

Using the comparison element 30, the current value of the load current is compared with the set value calculated in the second voltage divider 23.

In the second adder 26, the active leakage resistance component Rpo is calculated.

Element And 31 serves to block, excluding the supply of control signals, to the output execution unit 35 for the duration of connection to the mains of the source 1 of the operating voltage. The output of the Executive unit 35 provides control of the power source 34 according to a predetermined law.

The device works as follows

When a device is applied to the input of the set, its source voltage starts to work

The keys 4 and 5 are in the closed state. The installation unit 10 in the O sets the integrators 6, 7, 28 and 19 to the zero state, the elements of MEMORY 8 and 9 and turns on trigger 11, As a result of triggering 11 trigger by a signal from its first output through the separation and amplifying unit 14 turns on the second switch 5 and the operating voltage generator 1 is connected to the conductors of the monitored power network. At the second output of the trigger 11, a logic zero signal is generated and the drive control signal of the blocking element I 31 o is inhibited

By means of a pulse shaper 12 and a pulse divider 13, the time delay t is counted, connection 10

15

20

neither generator 1 operational voltage to a controlled network.

The magnitude of the operational source voltage from the operational voltage sensor 2 is supplied to the second element MEMORY 9 and is stored therein.

The current in the source voltage circuit 1 is created by the distributed leakage resistance, the network capacity, the resistance of the motor winding and the current through the diode 39. This current contains constant and alternating components. The variable component is determined by the complex impedances of the leakage and the electric motor core circuit. The constant component Ip is determined by the resistance of the cable cores, 1 by the resistance of the elements of the second switch 5 and the diode 39 in the conducting state, and is:

P

U0n

Rc + RK, + R

 5I

J

0

five

0

where u

on

R. R

ki

R

39

the value of the output voltage of the operational generator 1;

resistance of the power cable;

respectively, the resistance of the key elements 5 and the diode 39 in the conducting direction

In the first integrator, b, the signal is proportional to the current of the source 1 of the operating voltage. The output voltage of the first integrator 6 during the operational voltage period is proportional to the constant component of the current. The summation of the current value over a period of time t provides an average value of the current magnitude 5, which reduces the probability of error.

After a time delay t, determined by the driver 12 and the pulse divider 13, a pulse is formed at its first output, which switches trigger 11 to the second state. The voltage at the output of the first integrator during this time reaches the level

0

and,

- к, t «f)

where K is the proportionality coefficient;

on

voltage frequency of the operational generator,

and through the first key 4 is written to the first element MEMORY 80 Trigger 11, by switching its first output, turns off the separation and amplifying unit 14, and the second output forms a logical unit at the first input of the element 310 As a result, the second key 5 is turned off on the control network, and the lock is removed, prohibiting the passage of a control command to the output execution unit 35 o

The signal from the first element MEMORY 8 is supplied to the first threshold element 200 In the short circuit in the power network, the constant component of the output voltage U, the first integrator 6 is less than the specified threshold value A of the first threshold element 20, t0e0 U4 A ,. When this condition is fulfilled, a command is generated at the output of the first Threshold Element 20 that prevents the output executive unit 35 from being turned on. And information is given to the indication unit 15 about the presence of an emergency mode, which leads to de-energizing the power source 34 o

In the absence of a short circuit in the power network, the condition Uj A is fulfilled and the signal at the output of the first threshold element 20 is absent. This completes the process of measuring the resistance of the conductors of the power network and monitoring the presence of a short circuit in the de-energized state of the network and the drive can work in operation

In the operating mode, using the first voltage divider 22, the voltage Uon is divided from the output of the second element MEMORY 9, corresponding to the average value of the operational voltage and voltage U, from the output of the first element MEMORY 8o. As a result, the first output divider 22, a signal Ucu is formed which is proportional to the total resistance of the power network, the switch 5 and the diode 39 to the operating current, m0.

Wow.

and and

kgkg

where K, is the ratio proportional

bones,-

Using the first adder 25, the total resistance RR of the second key 5 in the open state and the diode R ,,, in the conducting state, the values of which are set in the first setting unit 27, are subtracted from the total resistance R-.

The signal at the output of the first adder 25 is proportional to the resistance of the cores of the power cable Rc, t „e„

Is, Kj (R2.) K3Rc; where K- is the transfer coefficient of the adder ,,

Using the second voltage divider 23, the setpoint of the operation of the protection device against short-circuit currents I k, MI is calculated; corresponding to the effective voltage in the power network in operating mode U and short circuit at the most specific point of the network, i0 0

I.,

K.Z. MIJ

-v and -K4 R,;

where K c. - divider transfer ratio of 29 o

The value of UH is provided from the output of the fourth integrator 19.

Comparison element 30 compares the pickup setpoint to 3. min calculated by the voltage divider 23, with the load current I / c, the value of which is formed at the output of the third integrator 18

When a short circuit I IK. with the formula

, x R ° i;: where X ,,., and R ,,,. - kilometric characters CM

capacitance and ohmic resistances of the power cable cores, the values of which for a particular type of cable are known and entered into the second setting unit 28

Using the third voltage divider 24, the impedance of leakage in the power network RU is calculated in accordance with the formula

and"

Vir

where i

U

- a leakage current, the value of which is fed to the second input of the divider 24 from the output of the second integrator 7.

In the second adder 26, the active resistance component is calculated.

9

leakage r equals rd xc

With the help of the second threshold element 21, the magnitude of the active component of the leakage resistance Cd is compared with the leakage protection setting

R

and under the condition

R06

yst

6, the output of the threshold element 21 is formed to command the shutdown of the output actuator unit 35 and the signal to the display unit 15.

Thus, the invention allows to control the occurrence of emergency conditions in the electrical network of mining machines with adjustable drive - short circuits and leaks to the ground.

Claims (1)

Invention Formula Device to protect the electrical network from damage, containing a source of operating voltage of alternating current with an isolation transformer at the output and terminals for connection to a monitored network , load current sensor, operating current sensor, the first integrator and the first switch in series, as well as the second and third integrators, the second switch, two threshold elements, two adder, multiplier, element And, two voltage divider and output control unit, characterized in that, in order to increase reliability by improving the accuracy of measurement of monitored parameters, an operational voltage sensor, two elements of O, are additionally introduced connected pulse shaper and pulse divider, third voltage divider, two sets of settings, reference element, trigger, switching and amplifying 40 45 50 55 To the winding of an isolation transformer, an operational voltage sensor and the first output current sensor are connected, the second output terminal of which and the second output of the operation voltage sensor are connected to the inputs of the second switch, the outputs of which are intended for connection to the controlled network, the output current sensor output connected to the input of the first integrator, the output of the first switch is connected to the first input of the first element of the MEMORY, the output of the sensor of the operational voltage is connected to the first input of the second element of the MEMORY Connected to the installation of the first integrator, the first element of the MEMORY, the second element of the MEMORY, the second integrator, the third integrator, the fourth integrator and the installation input of the trigger, the output of the first element of the threshold element and the first the input of the first voltage divider, with the second input of which is connected to the output of the second element MEMORY, to the second output winding of the isolation transformer through 1 diode connect a shunt resistor, to the output terminals of which the inputs of the converter are connected The pulses, the first output of the pulse divider is connected to the control input of the first key and the counting input of the trigger, the first output of which is connected to the control input of the second key through the switching and amplifying unit, and the second output the second output of the second integrator, the first input of the fourth integrator and the first input of the third integrator, the second input of the last one is connected to the output of the load current sensor, to the output of the sensor the network voltage is connected to the second inlet of the fourth integrator, the second input of the second integrator is connected to the output of the connection block, the output of the second integrator is connected to the first input of the third voltage divider, the first input of the second voltage divider is connected to the second input of the third voltage divider and exit ne the block, the fourth integrator and the block of the new adder, and the output with the first B73497u diction, grigre this to the first weekend ten 15 20 25 thirty 35 40 45 50 55 To the winding of an isolation transformer, an operational voltage sensor and the first output current operating sensor are connected, the second output of which and the second output of the operational voltage sensor are connected to the inputs of the second switch, the outputs of which are intended for connection to the controlled network, the output current operating sensor is connected to the input of the first integrator, the output of the first key is connected to the first input of the first element MEMORY, the output of the operating voltage sensor is connected to the first input of the second element MEMORY, output The installation unit in О is connected to the installation inputs in О of the first integrator, the first element MEMORY, the second element MEMORY, the second integrator, the third integrator, the fourth integrator and the installation input of the trigger, the output of the first element MEMORY is connected to the input of the first threshold element and the first input of the first voltage divider, with the second input of which is connected to the output of the second MEMORY cell, to the second output winding of the isolation transformer, through the diode, a shunt resistor is connected, to the output terminals of the cat The inputs of the pulse former are connected, the first output of the pulse divider is connected to the control input of the first key and the counting input of the trigger, the first output of which is connected to the control input of the second key through the separation and amplifying unit, and the second output is connected to the first input of the And element, the second input which is connected to the Start button, the second output of the pulse divider is connected to the first input of the second integrator, the first input of the fourth integrator and the first input of the third integrator, the second input of the last n The second input of the fourth integrator is connected to the output of the load current sensor; the second input of the second integrator is connected to the output of the connection block; the second integrator output is connected to the first input of the third voltage divider; the first input of the second voltage divider is connected to the second the input of the third voltage divider and the output of the first element of the comparison element, the second input of which is connected to the output of the third integrator, and the output to the output of the first threshold element, with this output the first voltage divider is connected through the first adder, multiplier, the second adder and the second threshold element connected in series to the output of the first threshold element, to the second inputs The first adder, multiplier and second adder are connected respectively to the outputs of the first setpoint setting unit, the second setpoint setting unit and the output of the third voltage divider, the output of the first threshold element is connected to the input of the display unit and the first input of the output execution unit, connected to the output of the AND