RU2581607C1 - Method of protection from breaks of phase and neutral wires of four-wire overhead line of electric mains voltage of 380 v and device therefor - Google Patents

Abstract

FIELD: electronic equipment.

SUBSTANCE: method comprises use for protection of three-phase line of electric energy meter installed at input of consumer, in addition it functions to detect breakages phase and neutral wires, formation in counter command disconnecting signal transmitted in transformer substation, supply overhead line. Command of disconnecting signal acts on release of automatic circuit breaker installed at beginning of overhead line, and provides switching off damaged line. Device for protection against breaks phase and neutral wires four-wire overhead line comprises a transformer substation, automatic circuit breaker, four-wire air line, a microprocessor electric energy counter, load measurement unit of phase voltages relative to zero wire, a unit for determination of phase and neutral wires, a unit for generating disconnecting signal transmission channel shutting down command signal and actuator.

EFFECT: higher reliability of electric circuits with voltage of 380 V and improved electrical safety.

8 cl, 5 dwg

Description

The invention relates to electrical engineering and can be used to protect against breaks in the phase and zero wires of the overhead line of an electric network with a voltage of 380 V.

There are a large number of protection devices against phase and zero wire breakage of overhead lines of electric networks with a voltage of 380 V.

A device is known for current protection of a portion of a three-phase line from a break in one of the phase wires [A.S. USSR No. 714562, class H02H 5/10; H02H 3/08; publ. 02/05/1980, BI No. 5], containing the filter of currents of the reverse sequence, the protection unit and the executive body, designed to protect the three-phase motor load. For work, information on currents of the negative sequence is used. When the phase wire of the supply line is broken, the symmetry of the phase currents is broken and a signal proportional to the currents of the negative sequence appears at the filter output, which leads to the operation of the protection unit and the motor is disconnected from the line by the executive body. The disadvantage of this device is that it is installed in front of the engine and can protect only a separate power receiver.

A device for protecting electrical networks of 0.38 kV when the wires are broken, containing a negative sequence voltage filter, a protection unit and a short circuit, installed at the end of the line in front of the consumer, as well as a current protection device installed at the beginning of the supply line [R. Sagutdinov. et al. Protection of electrical networks 0.38 kV in case of wire breakage. Power stations, 1982, No. 7. S. 56-58]. When the phase wire is cut off, a signal proportional to the voltage of the reverse sequence appears at the filter output, which leads to the operation of the protection unit, which includes a short circuit, creating an artificial short circuit at the end of the line. The current protection installed at the beginning of the line should feel this short circuit and disconnect the line with broken wires. The disadvantages of this device are, firstly, that an artificial short circuit is created to turn off the damaged line and this generally adversely affects the equipment of the electrical network, and secondly, it is known that current protections installed at the beginning of overhead lines have insufficient sensitivity to remote short circuits and cannot turn them off.

A device for protecting against an asymmetric mode of operation of an electric network with isolated or compensated neutral [A. S. USSR No. 815833, cl. H02H 3/24; H02H 5/10, publ. 03/23/1981, BI No. 11], which contains AC voltage converters connected to each phase of the network with a logic signal with voltage settings, a logic circuit and an executive body. When a phase wire breaks, the corresponding converter, which has a minimum voltage setting, changes the output signal from a logical unit to a logical zero. The logic circuit, analyzing the combination of the output signals of the converters, detects a broken phase wire and, acting on the executive body, disconnects the consumer from the network. The disadvantage of this device is that it protects only a separate power receiver.

Known electric energy meters with protective shutdown, one of the technical tasks of which is to provide protection from raising or lowering the voltage [Pat. RF №2498322, class G01R 11/00, publ. November 10, 2010; Three-phase active and reactive electric energy meter CE 303 / Operation manual. - Stavropol: CJSC Energomera, 2012. - 65 p.]. This counter function is designed to protect power consumers when voltage parameters exceed acceptable values — when the voltage decreases or rises below or above certain values, the meters disconnect consumers from the mains using the load control relay. The disadvantage of these devices is the protection of only individual consumers, as well as the lack of a function for determining the breakage of the phase and zero wires of the power supply network.

A device is known for protecting an electrical installation from a zero wire break in a network with a dullly grounded neutral, in which, to control the integrity of the zero wire of a four-wire electric network, a non-industrial frequency current is introduced into the zero-sequence circuit using a special generator. The protection unit that controls the flow of non-industrial frequency current along the zero sequence circuit, in the event of a decrease or disappearance of this current, acts on the actuator that disconnects the damaged line [A.S. USSR No. 854249, class H02H 5/10; publ. 05/07/92, BI No. 7]. The disadvantage of this device is the deterioration in the quality of electrical energy supplied to the consumer.

Closest to the claimed device in technical essence and the technical result achieved is the "Method of measuring electric energy in two-wire networks with theft protection and a device for its implementation (their options)" (Pat. RF No. 2087918, G01R 11/24; publ. 20.08 .1997), adopted for the prototype, which consists in the fact that in an electrical network consisting of a power transformer, a supply line and a load, a microprocessor electric energy meter is used to measure power.

The disadvantage of this device is the lack of recognition of emergency situations that occur in the supply air line when the phase and neutral wires are broken.

An object of the invention is to increase the reliability of electrical networks with a voltage of 380 V and improve electrical safety conditions.

The technical result is achieved by the fact that the device for protecting against phase and zero wire breakages of a four-wire overhead line of an electric network of 380 V, connected via a circuit breaker to a supply transformer substation, which contains a microprocessor-based electric energy meter and an electrical load connected in series, further comprises a channel connected in series transmitting commands of the disconnecting signal and the executive unit, and the microprocessor counter is electric The energy supply further comprises a series-connected phase voltage measuring unit relative to the neutral wire, a phase and zero-wire break detection logic unit and a trip signal generating unit, the phase voltage measuring unit being connected to three phase and zero wires of a four-wire overhead line, an output of the disconnecting command generating unit the signal is connected to the input of the command channel of the trip signal, the output of the executive unit is connected to the automatic a circuit breaker, while the logic block for detecting phase and zero wire breaks contains the first three converters of the instantaneous phase voltage to a logic signal with a minimum voltage setting, a series summing unit of three instantaneous phase voltages relative to the neutral wire and the fourth converter of the instantaneous voltage to a logic signal with a maximum setting voltage, two logical blocks OR, and the inputs of the first three converters of instantaneous phase voltage in l a logical signal with a minimum voltage setting and three inputs of the summing unit of three instantaneous phase voltages with respect to the neutral wire are connected to three outputs of the instantaneous phase voltage measuring unit with respect to the neutral wire, the three inputs of the first logical OR block are connected to the outputs of the first three instantaneous phase voltage to logic converters with a minimum voltage setting, the two inputs of the second logical block OR are connected respectively to the outputs of the first logical block OR And the fourth converter of instantaneous voltage to a logical signal with a maximum voltage setting, and its output is connected to the input of the block forming the command of the disconnecting signal.

In FIG. 1 shows a diagram of a device for protecting against phase and zero wire breaks of a four-wire overhead line of an electric network with a voltage of 380 V; in FIG. 2 shows a diagram of a first embodiment of a logic unit for detecting phase and neutral wire breaks; in FIG. 3 is a diagram of a second embodiment of a logic unit for detecting phase and zero wire breaks; in FIG. 4 is a diagram of a device of a unit for generating a trip signal command; figure 5 shows a diagram of the Executive unit.

The 380 V electric network contains a transformer substation 1 connected in series, a circuit breaker 2, a four-wire overhead line 3, at the end of which a microprocessor-controlled electric energy meter 4 and an electrical load are connected, serially connected a transmission channel of a trip signal command 8 and an executive unit 9, a microprocessor the electric energy meter 4 contains series-connected phase voltage measuring unit with respect to left wire 5, a logic block for detecting phase and zero wire breaks 6 and a block for generating a trip signal 7, the four inputs of a block for measuring phase voltages relative to the neutral wire 5 connected to three phase and zero wires of an overhead line 3, the output of the block for generating a trip signal 7 connected to the input of the transmission channel of the tripping signal 8, and the output of the Executive unit 9 is connected to the circuit breaker 2.

To explain the operation of the device, we will consider how the voltages in the electric network with a voltage of 380 V change under different modes of its operation.

Under normal operating conditions of the electric network, the phase voltage values relative to the neutral wire are close to the nominal values, and the asymmetry voltage of the three-phase voltage system relative to the neutral wire, even with extreme variants of the consumer phase load asymmetry (no load on one or two phases at once) does not exceed 60% of the phase values.

When the phase or neutral wires are broken, an emergency occurs on the four-wire overhead line, which is dangerous both for the electrical equipment of the electric network, consumers of electric energy, and people and animals located near the broken wires. When a phase wire breaks, the voltage in the phase relative to the neutral wire behind the damage site (from the consumer side - at the input of the microprocessor counter) becomes close to zero. In the event of a break in the neutral wire, the phase voltages relative to the neutral wire in the electric network section behind the damage site (from the consumer side - at the input of the microprocessor counter) depend on the symmetry of the consumer phase loads and, in extreme cases, the load asymmetries can be:

- voltages in phases relative to the neutral wire in some phases can increase up to 0.866-1 linear values, and in other phases can decrease up to 0.866-0 phase values;

- the asymmetry voltage of a three-phase voltage system relative to the neutral wire can increase within 1.5-3 phase values;

- the voltage of the neutral wire relative to the ground can increase up to 0.5-1 phase values.

Changes in phase voltages with respect to the neutral wire and asymmetry voltage can be used to detect breaks in the phase and zero wires of the four-wire overhead line of an electric network with a voltage of 380 V - for this, a logic block for detecting phase breaks is introduced into the microprocessor-based electric energy meter installed at the end of the line at the consumer input and zero wires.

The device operates as follows.

In a 380 V electric network, from a power transformer of a transformer substation 1 with a circuit breaker 2 turned on, a consumer of electric energy is fed through a four-wire overhead line 3, at the input of which a microprocessor-based electric energy counter is turned on. Unit 5 measures the phase voltages relative to the neutral wire and feeds them to the inputs logic block for detecting phase and zero wire breaks 6. During normal operation of the electrical network at the output of the logic block definition phase and neutral wire breaks 6, the signal is logical zero, the microprocessor counter 4 does not generate any tripping commands, the circuit breaker 2 is in the on state, supplying voltage to the overhead line 3, through which consumers of electric energy are fed.

When the phase or zero wires of the overhead line 3 are cut off, the logic unit for determining the breaks of the phase and zero wires 6 detects this break, its output signal becomes equal to a logical unit, and block 7 generates a trip signal command. The trip signal command via transmission channel 8 (for example, via the channel of a GSM cellular communication operator) is transmitted to transformer substation 1 and, acting on executive unit 9, turns off circuit breaker 2, removing voltage from the overhead line with broken phase or neutral wires. Thus, an emergency situation is eliminated in the electric network voltage of 380 V.

In microprocessor counters, the information on the instantaneous phase voltages relative to the neutral wire or the processing of information on the rms phase voltages relative to the neutral wire are used to measure the consumed electric energy. In this regard, the application considers two versions of the logic unit for detecting phase and neutral wire breaks 6. Accordingly, the phase voltage measuring unit relative to the neutral wire 5 at its outputs can select instantaneous or rms phase voltages relative to the neutral wire.

In FIG. 2 shows the first embodiment of a logic unit for detecting phase and zero wire breaks 6, which contains the first three converters of the instantaneous phase voltage to a logic signal with a minimum voltage setting of 10, 11, 12, connected in series to the summing unit of three instantaneous phase voltages relative to the neutral wire 14 and the fourth converter of instantaneous voltage to a logical signal with a maximum voltage setting of 15, two logical blocks OR 13, 16, and the inputs of the first three converters lei 10, 11, 12 and three inputs of the summing unit 14 are connected to three outputs of the unit for measuring instantaneous phase voltages relative to the neutral wire 5, three inputs of the first logical block OR 13 are connected to three outputs of the first three voltage converters 10, 11, 12, two inputs of the second logical block OR 16 are connected respectively to the outputs of the first logical block OR 13 and the fourth Converter 15, and its output is connected to the input of the block forming the command shutdown signal 7.

The logical unit for determining the breakage of the phase and neutral wires 6 according to the first embodiment operates as follows. The instantaneous voltage of the network phases relative to the neutral wire U _AN , U _BN , U _CN are supplied to the inputs of the first three converters 10, 11, 12 and the inputs of the adder 14. As a result of the vector summation of three instantaneous voltages at the output of the adder 14, an instantaneous asymmetry voltage U _{HC of the} three-phase system is obtained instantaneous voltage relative to the neutral wire. The first three converters 10, 11, 12 have a minimum voltage setting (for example, U _УСТ1 = 0.1 · U _Ф ), which provides a change in the output signal F of these converters from a logical zero to a logical unit when the phase wire breaks with a corresponding decrease in voltage by phase relative to the neutral wire. Logical signals F from the outputs of the first three converters 10, 11, 12 are fed to the inputs of the first logical element OR 13. Its output signal K in the normal mode is logic zero, and when a wire break occurs on any of the phases of overhead line 3 it becomes equal to a logical unit. The fourth converter 15 has a maximum voltage setting (for example, U _УСТ2 = 0.7 · U _Ф ) when the neutral wire breaks and the asymmetry voltage U _HC rises, its output signal N changes from a logical zero to a logical unit. The signals K and N from the outputs of the first logical element OR 13 and the fourth converter 15, respectively, are fed to the inputs of the second logical element OR 16. Its output signal L in normal network operation is logic zero, and when any phase wire or neutral wire breaks, it becomes logical unit. Thus, when an emergency mode of operation of the overhead line occurs, the logic unit for detecting phase and neutral wire breaks 6 generates a corresponding logical signal.

In FIG. 3 shows a second embodiment of a logic block for detecting phase and zero wire breaks 6, which contains the first three converters of the rms phase voltage to a logic signal with a minimum voltage setting of 10, 11, 12, and a series-connected unit for calculating the rms voltage of the asymmetry of three rms phase voltages relative to zero wires 17 and a fourth converter of rms voltage to a logical signal with a maximum voltage setting of 15, two logical blocks OR 13, 16, and the inputs of the first three converters 10, 11, 12 and three inputs of the calculation unit 17 are connected to three outputs of the unit for measuring the rms phase voltage relative to zero

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wires 5, three inputs of the first logical block OR 13 are connected to three outputs of the first three converters of the rms voltage 10, 11, 12, two inputs of the second logical block OR 16 are connected respectively to the outputs of the first logical block OR 13 and the fourth converter 15, and its output is connected with the input of the block forming the command disconnecting signal 7.

The logic unit for determining the breaks of the phase and neutral wires 6 according to the second embodiment operates similarly to the logic block for determining the breaks of the phase and neutral wires according to the first embodiment. The difference is that the rms asymmetry voltage U _{HC of the} system of three rms phase voltages relative to the neutral wire at the input of the microprocessor counter U _AN , U _BN , U _CN are calculated using calculation unit 17, and the first three converters of the rms phase voltage to logic signal with a minimum setting voltage 10, 11, 12 are comparing the phase rms voltages with the minimum voltage _setting (for example, U _УСТ1 = 0,1 · U _Ф ) and the fourth rms converter LfTetanus voltage logic signal with a maximum setpoint voltage 15 comparisons rms voltage unbalance with the maximum setpoint voltage (e.g., U _UST2 = 0,1 · U _F).

In FIG. 4 is a diagram of a block for generating a trip signal 7 command, which contains a series-connected random response filter 18, a block for converting a logical signal into a signal of a communication channel 19 and a transmitting modem of a communication channel 20, the input of the filter 18 being connected to the output of the logic block for detecting phase and zero wire breaks 6, and the transmitting modem 20 has an output to the transmission channel of the trip signal 8 command (for example, to the channel of a GSM cellular communication operator).

Block forming the command shutdown signal 7 operates as follows. The filter 18 blocks the passage of random responses that may be caused by industrial or other interference. The logic of the filter 18 can be built, for example, on two- or three-fold confirmation of the output signal coming from the logic block for detecting phase and zero wires breaks 6. In the event of an emergency operation of the electric network, when the output of the logic block for detecting phase and zero wires breaks 6, a “stable” logical unit appears, passing through the random response filter 18 and arriving at the input of block 19, which converts the logical signal into a signal of the communication channel, and transmitting second modem 20 provides its transmission via the communication 8 (e.g., the cellular operator communication channel GSM) channel to the operation unit 9 to cut off the line, in which the breakage occurred or zero phase conductors, the circuit breaker 2.

In FIG. 5 is a diagram of an actuator unit 9, which contains a receiving modem 21 in series, a trip unit 22, and an independent release 23, the input of the receiving modem 21 being connected to the command channel of the trip signal 8, and an independent trip 23 connected to the circuit breaker 2.

Executive unit 9 operates as follows. In the event of an emergency mode of operation of the electric network, the trip signal command transmitted from the microprocessor electric energy meter 4 via transmission channel 8 (for example, via the channel of a GSM cellular communication operator) is sent to receiving modem 21 (for example, GSM receiving modem) and disconnecting unit 22. Block 22, by supplying voltage to the shunt trip 23, provides the operation of the circuit breaker 2, which disconnects the voltage from the overhead line with broken phase or neutral wires and eliminates the emergency a situation in an electrical network with a voltage of 380 V.

Claims (4)

1. Device for protecting against phase and zero wire breakage of a four-wire overhead line of an electric network of 380 V connected with a circuit breaker to a power transformer substation, comprising a microprocessor-based electric energy meter and an electrical load connected in series, characterized in that it further comprises connected in series the transmission channel of the trip signal command and the executive unit, and the microprocessor counter of electrical energy up to additionally contains a series-connected phase voltage measuring unit relative to the neutral wire, a phase and zero-wire break detection logic unit and a trip signal command generating unit, the phase voltage measuring unit being connected to three phase and zero wires of a four-wire overhead line, the output of the trip signal command generating unit with the input of the channel for transmitting the trip signal command, the output of the executive unit is connected to the circuit breaker, etc. and the logic block for detecting phase and zero wire breaks contains the first three converters of the instantaneous phase voltage to a logical signal with a minimum voltage setting, a series summing unit of three instantaneous phase voltages relative to the neutral wire and the fourth converter of the instantaneous voltage to a logic signal with a maximum voltage setting , two logical blocks OR, and the inputs of the first three converters of the instantaneous phase voltage to a logical signal with a minimum voltage setting and three inputs of the summing unit of three instantaneous phase voltages with respect to the neutral wire are connected to three outputs of the instantaneous phase voltage measuring unit with respect to the neutral wire, the three inputs of the first logical OR block are connected to the outputs of the first three converters of instantaneous phase voltage to a logical signal with a minimum voltage setting, the two inputs of the second logical block OR are connected respectively to the outputs of the first logical block OR and the fourth eobrazovatelya instantaneous voltage logic signal with a maximum setpoint voltage, and its output connected to an input unit for generating the trip signal command. 2. The device according to claim 1, characterized in that the logic unit for detecting phase and zero wire breaks of the microprocessor-based electric energy meter contains the first three converters of the rms phase voltage to a logic signal with a minimum voltage setting, connected in series to the rms voltage asymmetry calculation unit of the three rms phase voltage relative to the neutral wire and the fourth Converter rms voltage to a logical signal with m the maximum voltage setting, two logical OR blocks, the inputs of the first three converters of the rms phase voltage to the logic signal with the minimum voltage setting and the three inputs of the rms voltage calculation unit of the asymmetry of the three rms phase voltages relative to the zero wire are connected to the three outputs of the rms phase voltage measurement unit relative to the neutral wire, the three inputs of the first logical block OR are connected to the outputs of the first three developers of the rms phase voltage to a logic signal with a minimum voltage setting, the two inputs of the second logical block OR are connected respectively to the outputs of the first logical block OR and the fourth converter of the rms voltage to a logic signal with a maximum voltage setting, and its output is connected to the input of the command generation unit disconnecting signal. 3. The device according to p. 1, characterized in that the block generating the command of the disconnecting signal contains a series-connected filter of random responses, a unit for converting a logical signal into a signal of a communication channel and transmitting a modem of a communication channel, wherein the input of the filter of random operations is connected to the output of the logic block for determining breaks phase and neutral wires, and the transmitting modem has an output to the transmission channel of the trip signal command. 4. The device according to claim 1, characterized in that the actuating unit comprises serially connected a receiving modem of the communication channel, a circuit breaker tripping unit and an independent trip, the input of the receiving modem being connected to the transmission channel of the tripping signal command, and an independent trip unit connected to the circuit breaker.

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