SU744832A1 - Device for differential-phase protection of electric equipment with voltage regulator - Google Patents

Description

It is also known a device for differential-phase protection of an electrical installation, comprising current transformers installed at the ends of the protected object, to which an output conversion unit connected to it through a braking unit in a transient mode is connected, a comparison unit with a reactive Body on the output and a differential current converter, also connected to a conversion unit for output values, a third-harmonic filter of differential current, a steady-state braking unit, two differentials citing blocks, two time memory blocks, three keys and a time delay block, the third harmonic filter of the differential current being connected to the output conversion unit, the output from the nepBEJM input of the first temporary memory block and the first of the main inputs of the first key, block inputs In the steady state mode, they are connected to the outputs of the output conversion unit, its output is connected to the input of the first differentiating unit, the second main input of the first key, and also to the main / and control inputs of the second key, the output of the first differentiating unit is connected to the second input of the first temporary storage unit, the third input of which is connected to the voltage regulator of the protected object, ei output is connected to the control input of the first key whose output is connected to the second input of the comparison unit, the output of the converter the differential current is connected to the main input of the third key and to the input of the second differentiating unit, the output of which is connected to the first input of the second temporary memory unit, its output to the control input of the third key, you the stroke of which is connected to the third input of the comparator through the time delay block, the output of the second key is connected to the fourth input of the comparator block, and the output of the braking unit in transient conditions is connected to the fourth input of the first temporary memory block and the second input of the second temporary memory block 2j

However, this device may work falsely when a powerful impulse noise appears in its circuits, such as from newer circuits or directly relayed in the circuits of the relay from an external electromagnetic field with close short circuits, lightning discharges, and t , D. And indeed, with an abrupt increase in the signal at the input of the second differentiating unit, it interrupts the operating circuit of the relay and, if this does not start the braking circuit, the relay may operate

is false. The same can happen, for example, with such a damage of the second differentiating unit, when a signal appears abruptly at its output with a constant signal at the input and with any other damage in the relay circuit that causes the third key to open.

The purpose of the invention is to increase noise immunity and reliability.

This goal is achieved by using a device for differential phase protection of an electrical installation with a voltage regulator containing current transformers installed at the ends of the protected object with an input unit for conversion of input values, a braking unit connected to it in a steady state to which a differential current converter, a braking unit in a transient mode, a harmonic filter, and an output of a braking unit in a steady state at through the differentiating unit the first temporary storage unit and the first key, the comparison unit with the reacting body, the output of the differential current converter through the differentiating unit, the second temporary storage unit, the second key, the temporary unit connected to the comparator unit and directly to the second key, the output unit braking in a transient mode is connected to the first temporary storage unit, to the second temporary storage unit and to the comparison unit, the output of the harmonic filter is connected to the first temporary storage unit and to The first key, which is connected via the control circuit to the third key and to the braking unit in a steady state, and the third key output is connected to the comparison unit, the time block is designed as a memory unit of the magnitude of the previous mode, the output of the differential current converter is additionally connected with the input of the comparison block.

The drawing shows a structural diagram of the relay.

The proposed relay contains a block 1 for converting input values, connected to protection current transformers and designed to convert secondary currents of current transformers into values convenient for protection operation. The outputs of block 1 are connected to block 2 of braking in set: lems mode. The braking unit 2. is designed to provide the required braking characteristic of the relay and has an output signal that is proportional to the difference in the sum of the modules of the arms of the protection arms and the differential current. Such an algorithm of operation of block 2 provides the maximum brake signal at the output in case of an external short circuit with a 180 ° current shift and the absence of a brake signal in case of an internal short circuit and no shift between the currents. In a differential current circuit, unit 2 is connected to a differential current converter 3, a transient braking unit 4 and a harmonic filter 5. A differential current converter 3 contains a device splitting the incoming signal proportional to the differential current into several components (two or three) followed by rectification and smoothing, and is intended to convert an ac signal proportional to the differential current to a corresponding dc signal. The block 4 torus of possible transient conditions is intended for braking in transient protection inrush of magnetizing current and an external short circuit. It can be made on the basis of a scheme comparing the amplitudes of the half-periods of the waves of the differential current, which distinguishes the even harmonics of the differential current, and other well-known principles. Harmonic filter 5 can be made in the form of a third or fifth harmonic filter and is designed to inhibit protection in the operating mode of a protected transformer with shifting, for example, if it is switched on a high voltage transmission line disconnected from the reverse side. A differential block 6 is connected to the output of block 3, which is designed to detect a sharp change in the signal at the output of the differential current converter 3. A temporary memory unit 7 is connected to the output of differentiating unit 6 for storing the presence of a signal at its input for ipaBHoe time, for example, 5-6 periods of power frequency. A switch 8 is connected to the output of block 7; it is intended for switching from the current taken from converter 3 to memory block 9. The memory unit 9 is designed to store the signal at its input for a time of, for example, 2 seconds. This unit may consist of a capacitance shunted by a high resistance resistor and charged from a small time constant up to the voltage supplied to block 9 of the memory of key 8, and a source follower whose input is connected to the indicated capacitance and the output is output block 9. By varying the value of the resistor shunting the capacitance, it is possible to change the time for which the memory received by block 9 is memorized: the signal within the required limits. The source follower, which has a large input impedance (on the order of 10 MΩ or more for serial chips), provides the required output value of memory block 9 without practically reducing the discharge time of the above-mentioned capacitance. If necessary, memory block 9 can be executed on any other principle. The output of block 9 is connected to the input 10 of block 11 of the comparison. The input 12 of the comparator unit 11 is connected to the output of the differential current converter 3. Comparison unit 11 has five inputs and one output and can be performed on a serial operational amplifier in a microchip design or any other similar device. The input 10 of the comparator unit 11 is intended to compensate for the positive signal received at the input 12 of the comparator unit 11 with the time delay determined by the time unit 7 of the time variable. The signal input to input 10 is inhibitory. Input 12 of block 11 is intended to act on a trigger. The input 13 of the unit 11 is designed to degrade the relay to the level of the operation current equal to, for example, 0.4 nominal and higher, depending on the magnitude of the incoming signal to it. Input 14 of block 11 is designed for intensive braking of the relay during external short circuits. The input 15 of the block 11 is designed to brake the protection in transient conditions. To the output of the comparator unit 11, a reacting body 16 is connected, which is intended to give a signal for disconnecting the current transformer. The key 17 in the control circuits is connected to the braking unit 2 and is intended for switching the signal also coming from the unit 2 to the input 14 of the comparator unit 11. The differentiating unit 18 connected to the output of the braking unit 2 is designed to perform functions similar to the functions of the differentiating unit 6. The temporary memory unit 19 also performs the same functions as the temporary memory unit 7, but remembers the signal for a time equal to 7 -9 periods of industrial frequency. The key 20 is designed to switch a whole series of deceptive signals to the input 13 of the comparator block 11. To such signals RELEVANT signal about the slave voltage regulating device under load, signals from the harmonic filter 5 and the braking unit 2 In addition, the key 20 provides the ability to adjust the initial amplification of the signal that provides the current of protection in the open position of the key 20 at the level of 0 , 3-0.5 rated current of the protected transformer, Inputs of blocks 7 and 19 of temporary memory are connected to the output of block 4 of braking in transient modes in order to ensure with these blocks the open state of key 20 and zak ytoe state switch 8 during the transition time. The input 15 of the comparator unit 11 is connected to the output of the unit 4 to provide braking protection during transients of magnetizing current surges and external short circuits. The proposed relay works with; During a short circuit in the protection zone, the signal at the output of the differential current converter 3 increases sharply, and at the output of the differentiating unit b a positive signal appears, under the influence of which the temporary memory unit 7 is activated, remember the fact that a positive signal appears at its input time equal to 5-6 periods of industrial frequency. Under the influence of a signal received from block 7 of the temporary memory, the key 8 is closed for the same Lam time: the signal F not passing to the block 9 of the signal f proportional to the new, increasing differential current value. Memory unit 9 stores the value of the signal proportional to the magnitude of the differential current before it is increased. This signal is supplied to the input 10 of the comparator block 11. The input 12 of the block 11 receives a signal proportional to HOBONrsI that increases the value of the differential current. As a result of this output, a comparison unit 11 for a time equal to 5-6 periods of the industrial frequency appears a signal proportional to the difference between the magnitude of the differential current and its previous value. Under the influence of this signal, the response element 16 is triggered and gives a signal to turn off Genius of the protected object. If the internal short circuit is accompanied by the appearance of a significant periodic component in the primary current and transients 1 and current transformers, then during the entire transient time, the output of block 4 has a signal supporting block 7 of the temporary memory in an open state key 8 is in the closed state, providing the effect at block 11 of the comparison of the difference between the signals at its inputs 12 and 10; To -avnoy change signal, propogl.onalnogo differential hoke .. At the input 15 of the unit 11 comparison in ZTO1-1 mode, a signal from (block 4j which has a braking effect on the relay. In addition, in this mode from block 4 also opens block 19 and key 20. From the key 20 to the input 13 of the comparator unit 11, an additional brake signal is also given, the deeper protection actuation current is approximately to the level of 0.4 of the rated current of the protected transformer. The protection occurs at the moment when the action of the signal proportional to the differential The potential current, and the input to the input 12 of the comparison unit 11, overcomes the braking effect of the signals arriving at the inputs 10, 13 and 15 of the comparison unit 11. The speed of the proposed relay, as well as the speed of the known protections, is ensured by the correct choice of the type of braking unit 4 in the transient modes and the magnitude of the signal fed from it to the unit 11. Comparison. With a short circuit on the protected transformer, the change in the differential current can be quite small (15-20% of the rated current). In this case, there will be no noticeable transient process in current transformers, the output of unit 4 also has practically no signal and the protection will work with its minimum value, equal to 10% of the rated current through the circuit of unit 1, unit 3, unit 11, reactive body 16 The sensitivity of protection in this mode is determined by the design of unit 3, as well as by the level of: the magma-max sensitivity of the pea.ijipyrc.j3ro organ 16. When the voltage regulating device of the protected transformer is under load (RPN), the current in the differential circuit also may increase, as a result of which key 8 closes and different in magnitude signals come back to inputs 12 and 10 of block 11, which can lead to false positives. To prevent a false action in this mode, the signal from the on-load tap-changer goes to block 19 of temporary memory which opens the key 20 and coarsens the protection for the entire duration of the on-load tap-changer to a level of approximately 0.4 of the rated current of the protected transformer (or higher, if the key 20 receives additional brake signals from the braking unit 2 or harmonic filter 5. Current magnitude protection operation in this mode can be increased if the unbalance current in the normal mode okazhuts commensurate with it (e.g., if. wide range of voltage regulation). When the protected transformer is turned on at idle, there can be a large inrush of magnetizing current. In this case, the protection is triggered along the working circuit and the input 12 of the comparator unit 11 receives a signal greater than that of input 10. However, the protection is inoperative due to the brake signal applied to the input 15 of the unit 11 from the braking unit 4 in transient conditions. If a magnetized current surge does not occur when the protected transformer is turned on, and the differential current increases by the magnitude of the steady-state magnetizing current, the protection does not work by selecting its minimum pickup current with a larger steady-state magnetization current, i.e. adjusting the sensitivity of the reacting organ 16. When the current increases magnetization of the protected transformer due to its overexcitation, for example, when disconnecting from the reverse end of the high voltage transmission line w audio, the second end of which is under ostals Turning to the protected voltag py inaction protection is provided by the braking action of the signal taken from the harmonic filter 5 (with the incoming its composition straightening Meath Lemma) .vklyuchennogo output unit 1 n forming the input quantities. The signal from the output of the harmonic filter 5 p leads to the triggering of block 19 and the opening, key 20, through which this signal enters input 13 of comparator block 11, and brakes the protection to the required level during the whole time of operation of the protected transformer with overstimulation. When an additional load is connected to the protected transformer, the differential current may also increase stepwise. In this case, the protection inaction is provided by the braking unit 2. The signal at the output of block 2 is proportional to the difference of the sum of the modules of the currents of the arms of the protection and the module of the differential current. This signal is maximum at a 180 ° current shift in the protection arms and is zero at a shift equal to 0 °. When the protected transformer operates under load, the signal at the output of the braking unit 2 increases with increasing load. Thus, with an abrupt increase in load, the signal at the output of block 2 also increases abruptly and a positive signal appears at the output of differentiating block 18, which starts temporary memory block 19, which opens the key 20 and the signal from block 2 enters input 13 unit 11, providing deeper protection as a function of the load current of the protected transformer. The protection actuation current always remains above the unbalance current. In the event of a short circuit outside the protection zone, the signal at the output of the braking unit 2 increases sharply. If it exceeds the value corresponding to the current flowing from the protection zones, approximately 200% of the nominal, the key 17 is opened and the signal from block 2 is fed to input 14 of block 11, providing intensive braking and protection failure in this mode. If an external short circuit fails with a transient process, the protection is additionally provided by an additional braking unit 4 in transient conditions. If, as a result of damage caused in blocks b, 7, and 18, or due to the impulse noise induced in these circuits, the protection is briefly activated, i.e., key 8 is closed for a while (within 2 seconds), then the spurious action protection does not occur, since the signals arriving at the inputs 10 and 12 of block 11 balance each other, and also, due to the proper operation time of block 11 together with the reacting authority 16. Thus, while maintaining the speed, selectivity and sensitivity of the known, the proposed differential The o-phase relay has higher noise immunity and HSS. Experiments show that the proposed device makes it possible to further increase the hardware reliability of the protection and ensure the level of this reliability, despite the complexity of the circuit, at the level achieved for the existing protection. The minimum tripping current of the protection using the proposed relay can be approximately taken equal to 10% of the nominal protection. In the established modes of external short circuits, the protection allows an error in the module of arm currents equal to 70-90%, accompanied by an angle error of 60-80 el. hail. Failure of protection in transient modes of magnetizing current surge and external short circuits

Claims (2)

Claim A device for differential-phase protection of an electrical installation with a voltage regulator, containing current transformers installed at the ends of the protected object with an attached unit for converting input values, a braking unit connected to it in a steady state, to which a differential current converter, a braking unit in transient mode are connected via a differential current circuit harmonic filter, and to the output of the braking unit in the steady state is connected through the differentiating unit first a temporary memory lock and a first key, a unit for comparing with a responsive organ, a differential current converter output through a differentiating unit, a second temporary memory unit, a second key, an E-change unit connected to the comparison unit and directly to the second key, the output of the braking unit in transition mode is connected to the first block of temporary memory, to the second j block of temporary memory and to the unit of comparison, the output of the harmonic filter is connected to the first block of temporary memory and to the first key, which is connected via a chain to the third key and to the braking unit in steady state, and the output of the third key is connected to the comparison unit, characterized in that, in order to increase noise immunity and reliability, the temporary unit is made in the form of a memory unit of the value of the previous mode, when this output of the differential current Converter is additionally connected to the input of the comparison unit. 20 Sources of information taken into account in the examination 1. USSR copyright certificate And 173254, cl. H 02 H 3/28, 1975. 2. USSR copyright certificate 25 according to application No. 2406390 / 24-07, class. H 02 H 3/28, 1976. TSNIIIPI Order 3829/20 Circulation 783 Subscription PPP Branch - '' Patent '', Uzhhorod, Project 4,