SU792404A1 - Device for testing maximum current protection in disconnected state - Google Patents

Description

one

The invention relates to the technique of preventive checks and adjustment of the means of overcurrent protection of electrical networks and electrical equipment in the disconnected state, directly at the place of installation of protective equipment, including in field conditions.

. Devices are known for testing the means of overcurrent protection at the installation site l. Portable test equipment for testing alternating current and voltage protection allows testing primary and secondary current protection, measuring the protection response time by synchronously starting the electrosecond counter with the start of load current flow by supplying a stopwatch from the auxiliary winding of a constant voltage located on the adjustable rod load transformer, the primary and secondary windings of which are galvanically isolated from each other. The equipment is powered from the AC mains.

The disadvantages of this equipment are large size and weight, the need to use the ne network.

belt current as a power source, the presence of normally sparking elements. These shortcomings do not allow the use of equipment in field conditions in explosive atmospheres, and it is difficult to verify the means of protection at the place of installation.

Of the known devices for checking the maximum current protection, device 2 is the closest to the technical essence. This device has an independent power source, an adjustable transducer, measuring shunts (oscillatory circuits, capacitors and an adjustable choke which are interconnected via a two-position switch, and the capacitors are connected through

20 switches and a converter with an autonomous power source and windings of additional relays through their contacts, an adjustable choke is connected to the measuring shunt, and the tested protection circuits are connected in series with the above measuring shunt and windings of additional relays.

However, this device due to the use of paper capacitors, and adjustable throttle, forming the contours of the damped oscillatory bits, has a relatively large weight. and the size and low efficiency of using the energy of an autonomous pulsed source, since not all the accumulated energy in the capacitors is used to test the protection. By means of the device, the protection is checked only by the secondary current — to check the primary current (up to 2500-3000 A), it is necessary to add another load transformer to it, which additionally increases the size and weight of the device. In addition, the presence of contact devices in a non-explosion-proof design and the lack of control over the reliability of contact in the furniture to connect the tested protection to the device makes it impossible to use it in explosive rooms. The aim of the invention is to reduce the size and weight of the device and increase the efficiency of using the energy of an autonomous pulsed current source. To do this, in a device having an autonomous pulse current source connected to the primary winding of a load transformer, the secondary winding of which, through a measuring shunt, is connected to the protection being tested, as well as a clamping current meter, is connected to the said shunt and a shield response meter connected to its executive contact, the start inputs of which are connected to the control unit of the verification process, which includes the contact control elements and the setting knob of the magnitude and duration AC load current pulse, autonomous pulse current source is made in the form of a single current pulse source, the autonomous power inverter is reintroduced to the load current frequency, the input and output of which are connected respectively to the current source and the primary winding of the load transformer and the inverter control circuit connected to the newly introduced control panel generator. The source of unipolar current pulses may contain a series-connected power supply battery, for example, a battery of batteries or dry cells, a controlled semiconductor converter of low DC voltage to high voltage of alternating current, pulsed electrolytic capacitors of aperiodic discharge circuits, and power non-contact cascade 1 switch-distributor, and the controlled converter is connected to the power supply through its switch through the switch, and with the output - I connect Condensing rectifying diodes with capacitors, the same plates of which are connected to the switchboard distributor inputs, the output of which and the common point of the other capacitor plates are connected to the input of the inverter, while the control inputs of the switchboard and the inverter are connected via an isolation transformer to the output of the controlled driving frequency generator of the load current, and the control inputs of the converter and the master oscillator are connected respectively to the direct and inverse outputs of the newly introduced trigger Schmitt control unit having an input through the start button device tokoogranychivayuschy zener diode and a resistor connected to the battery supply, while the output latch further connected signal lamp. In order to simplify the circuitry of the device when used to test the protection of load current with a shock effect, the number of capacitors in the above embodiment is calculated. the pulse current of a unipolar current can be reduced to one. At the same time, it is connected directly to an autonomous inverter with an adjustable pulse duty cycle to maintain a given value of the effective load current, in connection with which the output of the controlled decelerating generator is connected to the control input of the inverter through the Inhibit circuit, the prohibiting input of which is connected to the output of the pulse width setting device load current, the triggering input of this setpoint is connected to the inverse output of a Schmitt trigger, the control input of the inverter is connected to the output cxeNBd of the control the duty cycle of the pulses connected to the start input to the output is given by the generator, the control input to the unit of the load current, and to the control input to the pulse capacitor. The source of unipolar current pulses in the device can be made in the form of a small starter-type battery, for example, silver-zinc, connected via a fuse directly to an autonomous inverter with an adjustable duty cycle, and a differential circuit can be inserted into the control unit In connection with this, the setpoint input of the pulse current of the alternating load current is connected to the direct output of the Schmitt trigger, and the output of the setpoint device is connected to the input through the differentiating chain om of the mentioned trigger. In addition, in order to eliminate open arcing when using a device to test protection in explosive rooms, for example.

shafts, switching contact controls (pushbutton switch) and fusible fuse have explosion-proof design, the time meter input circuits to which the contacts of the tested relays are connected have intrinsically safe parameters, and the load transformer has an additional winding to which the low-power converter key regulator is connected a stable current, a switching input connected to the output of an uncontrolled high-frequency master oscillator, and successively turn on A diode and a current-limiting resistor connected to the input of a Schmitt trigger, and in parallel with the power secondary winding of the load transformer are connected spark-burning resistors.

As a controlled converter, in the above versions of an impulse source, a stable current converter can be used, consisting of a key controlled current regulator, the switching input of which is connected to the output of an unregulated high-frequency generator, the stabilizer output is connected to the primary region of the converter transformer, and It is also connected to the regulator of the load current magnitude due to the voltage level across the pulse capacitors (capacitor). This regulator is designed as a potentiometer, the slider of which is connected to the input of a Schmitt trigger, and the direct output of the latter is connected to the control input of the key stabilizer.

FIG. 1 is a block diagram of a device for testing overcurrent protection; in fig. 2 - part of the block diagram of the device with the option of a single-capacitor source of unipolar current pulses; in fig. 3 - a part of a block device with a battery version of a pulsed source.

The device contains an autonomous pulse current source 1, made in the form of a source of unipolar current pulses, a load transformer 2, a measuring shunt 3, a clamping current meter 4, a protection response time meter 5, a control unit 6 for testing, a switch 7, a device start button 8, unit 9 load current values, autonomous power inverter 10 at the frequency of the load current, generator-11 of the frequency of the load current.

In addition, it contains a low-power supply battery 12, a control voltage converter 13 pulsed electrolytic capacitors 14 included in the aperiodic circuits, a power contactless switch-distributor 15 made, for example, on the basis of a thyristor power pulse distributor developing diodes 16, simultaneously performing the functions of rectifier TCA, isolating and matching transformer 17, Schmitt trigger 18, zener diode 19 and current limiting resistor 20 of the circuit

starting the device, signaling device normal alarm 21, logic 22 Forbatching device, load current pulse width adjuster 23, pulse duty ratio adjusting circuit 24, fuse 25, differentiating chain 26, current metering circuit’s intrinsically safe input resistors 27, additional winding 28 load transformer, "Key current regulator 29 low-power stable current converter, uncontrolled master oscillator 30 of increased frequency, diode 31 and current The limiting resistor 32 of the device start-up blocking circuit with a loose contact of the circuit of the protection being tested with the device output, spark-fighting resistors 33, key controlled

a current stabilizer 34 of a controlled stable current converter, a converter transformer 35, a diode 36 and a load current resistor 37, a capacitor 38, limiting the duration of the pulse through the isolation transformer.

The device works as follows. After the device has been prepared for operation, the circuit of the protection to be tested is connected and its start through the switching control elements of the switch 7 and button 8 installed

in the control unit 6 of the testing process, an autonomous inverter 10 under the action of control pulses with a frequency of load current generated by a backward generator, for example

symmetric transistor multivibrator 11, control unit 6, inverts the current source of unipolar pulses 1. After transferring the invested current in the secondary winding of the load transformer

2 a pulse of alternating load current passes, creating a voltage pulse proportional to the current on the measuring shunt 3.

Simultaneously with the launch of the device, a pulse from the master oscillator 11 is applied to start the current meter 4 with fixation of the readings, performed, for example, in the form of an amplitude-time converter with a key circuit

Claims (5)

D fill pulse counter with digital indication of stable frequency pulses. In addition, a pulse from the master oscillator 11 simultaneously with the start-up of the device and the beginning of the passage of load current through the circuit of the protection being tested, triggers a time meter, executed, for example, in the form of a counter with digital indication, filled with stable frequency pulses. The time meter is stopped by either making or closing the actuating contacts of the protection to be protected by shunting the pulses at a stable frequency or, respectively, removing the supply voltage from the time meter input circuits. The magnitude and duration of the pulse of variable load current pre-sets with intermed. In the setting of knobs 9 and 23, respectively. In the case of using a capacitor source of monolithic current pulses, the device operates as follows (Fig. 1). After pressing button 8 through Zener diode 19 and resistor 20, the Schmitt trigger 18 is turned on, provided that the voltage of the supply battery 12 is higher or equal to the stabilization voltage of the Zener diode 19. From the direct output of trigger 18, a signal is given, permitting the correct voltage converter to operate 13, feeding through the switch 7 from the battery 12. At the same time, the lamp 21 lights up, indicating that the device has started up normally. The alternating voltage removed from the output of the converter 13 and rectified by the diodes 16 is supplied to n pulsed electrolytic capacitors 14, which are charged to the level n determined by the load value at the setpoint 9 of the load current, the signal from the output of which resets the trigger 18 which, in turn, stops the transducer 13. The lamp 21 goes out. Diodes 16 simultaneously perform the function of uncoupling capacitor circuits — incoming and separate circuits of a periodic discharge. At the inverse output of the flip-flop 18, a signal appears, working out the work of the back-up generator 11 of the load current frequency, the pulses from which through the capacitor 38 and the coupling matching transformer 17 arrive at the control input of the autonomous power inverter 10 and synchronously with this switch-switch 15. Switch 15. Cascadely connects to the input of the inverter 10 charged condensates, snoods 14. Unipolar pulses obtained as a result of aperiodic discharges are inverted and fed to a 1 W winding load. A new transformer 2, which is the load of the discharge circuits. The constant time of the contour sparing can be chosen such that in one case the capacitor 14 will be discharged over the full load-current period, and in the second - over the half period. In the first case, the circuit of the source of unipolar current pulses 1 is fairly simple, however, its efficiency is 0.6-0.7, and the shapes and amplitudes of the positive and negative half-current of the load current differ. In the second case, the source 1 circuit is somewhat complicated, but its efficiency increases to 0.92–0.98, and the shape and amplitude of the half-waves of the load current are identical. The simplification of the source 1 circuit in one case and its complication in the other is due to the fact that in the first case the control pulses of the switch 15 are removed from one arm of the multivibrator 11, and in the second from both, i.e. the switching frequency of the capacitors is doubled. The last execution of the circuit allows production. Switching the capacitors 14 is synchronized with the operation of the inverter 10, thereby improving the shape of the load current curve. The use of pulsed electrolytic capacitors 14 as accumulative elements of a pulsed load current source allows us to obtain the weight and dimensions of the device required by its manual carrying in cramped production conditions, for example, mine conditions. Pulsed, the source 1 can be made on the basis of a single electrolytic capacitor 14 with a constant capacitance. In this case, the scheme works in the following way (Fig. 2). After charging the capacitor 14 to the determination of the voltage level by the setting device 9, the trigger 18 is reset, enables the generator 11 to operate, and simultaneously sets the setting device 23 for the duration of the load current pulse. The pulses from the generator 11 through the logic circuit of the Inhibit 22 simultaneously receive the preemptive input of the inverter 10, which inverts the exponentially damped discharge current of the capacitor 14 with the frequency of the load current. To maintain the current value at a given level, the load current of the inverter 10 is made with an adjustable pulse duty cycle and at its control input signals are received from the pulse duty cycle control circuit 24 operating synchronously with the beginning of each half-wave of the load current specified by the generator 11, and the duty cycle of the half-wave It is inversely exponential with the voltage across capacitor-14. The initial duty cycle (of the first half-wave) depends on the value of the setpoint on the setter 9. After the setting of the setpoint 23, for example, made in the form of two series-connected pulse width limiters, the signal c. its output blocks the passage of the generator pulses 11 through the Ban on the control input of the inverter 10. However, the generator 11 pulses continue to flow to the starting input of the circuit 24, which causes the inverter 10 to stop without inverting if a small starter battery is used as a switching current source such as, for example, silver-zinc batteries, the scheme works in the following way (figure 3). After pressing button 8 through Zener diode 19 and resistor 20, the Schmitt trigger 18 is turned on, provided that the voltage on battery 1 is not less than the voltage of stabilization of the Zener diode. Using the signal of its direct output, the trigger 18 starts the frequency generator 11 and the setpoint 23 of the load current pulse duration. From the output of the generator 11, the pulses are fed to the control input of the inverter 10 with a controlled duty cycle, and through the pulse duty cycle control 24 to its controllability input. The actual value of the load current is set by the corresponding value of the half-period pulse duration, which is almost unchanged during the whole time of the load current pulse. Therefore, the control input of the duty cycle control circuit 24 is connected to a setting device 9 for a load current. After the pulse duration pulse current sensor 23 triggers its output signal with its leading edge through differentiation, J10 chain 26 resets trigger 18, which blocks the operation of multivibrator 11 and inverter 10 stops. To control the state of the external output power circuit is closed, open, the contact density, which is very important from the point of view of safety in case of using the device in explosive rooms, for example, mines, used an additional winding 28 of the load transformer 2, which is powered from the key stabilizer current 29 of the low-voltage converter with stable current pulses, therefore the voltage and winding is determined by the product of the resistance of the load transformer 2 and the load (tested protection) and the magnitude of the stable current pulses. This voltage through the diode 31 and the current-limiting voltage of the resistor 32 is applied to the input of a Schmitt trigger 18, which, if the voltage on the winding 28 exceeds the allowable value specified by the value of the resistor 32, is blocked and cannot be started by pressing the button 8. The key current regulator 29 receives pulses from an uncontrolled master oscillator 30 of high frequency (1000 Hz). To weaken the effect of the residual inductance of the transformer 2, resistors 33 embedded in an epoxy compound are connected in parallel with its secondary winding. The magnitude of the stable current pulses and the resulting voltage on the secondary winding of the transformer 2 are selected from the condition of providing intrinsically safe non-inductive circuit. Based on the intrinsic safety of using the device, the input circuits of the protection response time meter are equipped with 2T current-limiting resistors filled with epoxy resin; Contact switching elements (button 8, switch 7) are designed to be explosion-proof in order to prevent open arcing. The key controlled current stabilitator 34 is authorized to operate from the direct output of a Schmitt trigger 18. In addition, the key input of the current stabilizer 34 is pulsed from the output of the frequency generator 3. As a result, the output of the stabilizer 34 produces stable current pulses through the transformer 35 of the voltage converter 13 and through the diodes 16 linearly charge n capacitors 14, since the voltage on the primary winding of the transformer 35 linearly depends on the reduced value of the load resistance (voltage across the capacitor 14) multiplied by the constant current pulse, this voltage can be used as information about the magnitude of the charge capacitor. For this purpose, the voltage from the primary winding of the transformer 35 is supplied to the setpoint 9 of the load current, which has a potentiometer. From the slider of the potentiometer, through the diode 36 and the resistor 37, the voltage is applied to the control input of the trigger 18. Due to the current shortage of compact starter-type batteries (e.g., silver-zinc), the most optimal use of the unipolar current pulses of aperiodic discharge circuits based on pulsed electrolytic capacitors, which provide a pulse of a continuous load current, the shape of the curve and the amplitude of the current in the half-periodes of which are the same. If it is necessary to check the protection with load current with a shock effect, aperiodic discharge of only one pulsed electrolyte of a high capacitance capacitor with simultaneous inversion of the discharge current to the frequency of the load current (for example, 50 Hz) can be used. Inverting current sources in the device this current and its increase by means of a load transformer in order to obtain an alternating load current pulse of 25003000 A differs favorably from the method Such a current is obtained by using damped oscillating circuits, including paper capacitors of rather large dimensions and BecaJ as well as inductance in the form of a heavy throttle, using load; the transformer and in the latter case cannot be avoided when large currents are needed (2500 -3000 A). The differences mentioned above mainly consist in the following: the use of compact electrolytic capacitors and the abandonment of the cores significantly reduce the size and weight of the device as a whole; using an almost complete capacitor range (up to 98%) increases its efficiency — in a device with oscillating discharge circuits, the energy of a charged capacitor is used — only by 40-50%, since only one period of oscillating discharge is used to generate pulses} the device, which is safe in operation due to power supply autonomy (there is no option to connect to the AC network), has enhanced safety properties from the point of view of its use in explosive rooms (e.g., mines); the use of the device allows the simultaneous verification of the current setting of the protection operation to verify its speed. Approximate calculations showed that the mass of the device can be reduced from 35 to 20 kg, which creates ho. Other possibilities even for manual transportation in cramped production conditions. Claim 1. Device for testing the maximum current protection in the disconnected state, containing an autonomous switching current source connected to the primary winding of the load transformer, the secondary winding of which is connected to the tested protection through a measuring shunt, as well as a clamping current meter connected to said shunt, and the protection response time meter, connected to its executive contact, the start inputs of which are connected to the control unit of the verification process, Contact control elements and a unit for the magnitude and duration of an alternating load current pulse are expensive, characterized in that, in order to reduce the size and weight of the device and to increase the efficiency of using the energy of an autonomous pulsed current source, the latter is designed as a source of unipolar current pulses, and the autonomous power inverter was reintroduced to the frequency of the load current, the input and output of which are connected respectively to the current source and the primary winding of the load transformer, and the control circuit An inverter is connected to a newly introduced master oscillator of the control unit. 2. The device according to claim 1, characterized in that the source of unipolar current pulses contains subsequently connected supply batteries, a controlled charging voltage converter of the pulsed electrolytic capacitors of the aperiodic circuits, and a power proximity switch-distributor, the capacitor plates of the same name being connected to corresponding power inputs of the above-mentioned switch, the output of which and the common point of the other capacitor plates are connected to the input of the inverter, while the control inputs the switch and the inverter directly through an isolation transformer are connected to the control current of the load current frequency generator, and the control inputs of the converter and the master oscillator are connected to the forward and inverse outputs of the new control Schmitt trigger, the zener diode and The current limiting resistor is connected to the supply battery. . 3. The device according to paragraphs. 1 and 2, it is understood that, in order to simplify the circuit when using it to test the zetscite with a shock effect current, the source of unipolar current pulses is made on a single pulsed electrolytic capacitor connected directly to an autonomous inverter with a variable pulse ratio, moreover, the output of the controlled master oscillator is connected to the control input of the inverter through the Inhibit circuit, the prohibiting input of which is connected to the output of the setpoint for the pulse current of the load current, for repentieth input of the setpoint Cpd, nen latch with an inverted output Schmitt, the inverter control input is connected to the output of the pulse duty cycle control circuit, connected by the start input to the master oscillator output, the control input to the load current value controller, and the control input to the pulse capacitor. 4. Device on PP. 1, 2 and 3, characterized in that the source of unipolar current pulses is made in the form of a small starter-type battery connected via a fuse directly to a stand-alone inverter with adjustable pulse power, and a differential circuit is inserted into the control unit, and the setpoint input for the gel is inserted into the control unit Pulse AC load current connected with the direct output of the Schmitt trigger, and the output of the setter through the differentiating chain is connected to the input of the said trigger. 5. Device on PP. 1-4, characterized in that, in order to prevent open arcing during testing of protection in an explosive environment, such as mine atmosphere, its load transformer is provided with an additional winding, to which the key current regulator is small, a stable current converter, connected to the output of an uncontrolled high-frequency generator and a series-connected diode and current-limiting resistor connected to the Schmitt trigger input, and in parallel a power secondary Spark-fighting resistors are connected to the winding of the load transformer. b. Device on PP. 2 and 3, characterized in that a stable current converter consisting of a key controlled current regulator, the switching input of which is connected to the output of an unregulated high-frequency master oscillator, is used as a controlled converter, the stabilizer output is connected to the primary winding of the converter transformer, It is also connected to the regulator of the magnitude of the load current in the form of a potentiometer, the slider of which is connected through the diode and the resistor to the Schmitt trigger input, and the direct output is Lednov coupled to a control input of the key stabilizer. Sources of information taken into account in the examination 1.Patent Poland 3834, cl. 21 37/30, 1955. 2. USSR author's certificate number 417867, cl. H 02 H 3/08, 1974.