RU2740025C1 - Device for prevention of occurrence of fire-hazardous features and unreasonable emergency outages at crossing of wires of overhead power lines with voltage of 380 v - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: invention can be used in electric engineering for protection of power transmission lines with voltage of up to 1,000 V from formation of fire-hazardous features and emergency outages due to wire crossing. Device for preventing occurrence of fire-hazardous signs and unreasonable emergency shutdowns when crossing wires of overhead power lines with voltage of 380 V, installed in four-wire three-phase network, includes current-limiting unit, installed between automatic circuit breaker and three phase current transformers, which are installed in network, in-series connected short-circuit current measuring unit, time delay unit, logic element, control unit, as well as unit for measuring wind speed, wherein three short-circuit current measurement unit inputs are connected to three current transformers secondary windings, short-circuit current measurement unit output is connected to time delay unit input, which output is connected to first input of logic element, with second input of which is connected wind speed measurement unit output, note here that logic element output is connected with control unit input with its output connected with current-limiting unit input.

EFFECT: prevention of formation of fire-hazardous signs at crossing of overhead power line wires and exclusion of line disconnection at this crossing.

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Description

The invention relates to electrical engineering, in particular to the protection of power lines with voltages up to 1000 V from the formation of fire hazard signs and emergency shutdowns due to wire entanglement.

Emergency shutdowns in distribution networks are largely influenced by external climatic factors, as well as their intensity. The failure rate due to the influence of external climatic factors ranges from 35 to 86%. A significant part of the outages are associated with wire entanglement, which, in turn, depends on wind loads and is dangerous in terms of the possibility of fire hazard signs (sparks and molten metal droplets).

The existing methods of preventing the formation of fire hazard signs when the wires are clasped are reduced to the spatial separation of the wires within the specified limits (distance spacers of various types), or damping possible vibrations leading to the clashing of the wires (dampers). Thus, all existing technical solutions prevent the formation of fire hazard signs by mechanical elimination of entanglement. However, these solutions are not always effective.

From the prior art, rigid spacers are known installed between the wires of overhead power lines (hereinafter - overhead lines) to reduce the amplitude of the dance of the wires and reduce the likelihood of their clashing (Andrievsky V.N. and others. Operation of overhead power lines. M., Energy, 1976. - 616 s.).

The disadvantage of these spacers is that vibrations of one of the wires cause additional dynamic loads on the other wire.

From the prior art, a spacer for overhead lines is known, containing a rod with devices for fixing to the wires (RF Patent No. 2504876, publ. 20.04.2014).

The disadvantage of this spacer is that it facilitates the transfer of energy from one vibrating wire to the other, which leads to an additional dynamic load on the wire and causes both wires to vibrate with high amplitudes.

Various designs of rigid struts also have drawbacks associated with shortcomings in the design of the clamps, as well as with their structural complexity and unjustified manufacturing cost (Inventory Certificate No. 687515, publ. 09/25/1979).

Known devices for preventing entanglement of wires, made in the form of a cord or cable made of insulating material or the so-called elastic spacers (RF Patent No. 2331147, publ. 10.08.2008).

The disadvantage of these devices is their low mechanical strength, especially at the points of connection to the wire. In addition, these devices have limited resistance to partial discharges, which leads to a decrease in dielectric strength.

The efficiency of using elastic spacers is mainly related to their damping properties and depends on the characteristics of the elastic element. However, the spacers do not have sufficient rigidity, which negatively affects the conditions of reliable operation under the action of short-circuit currents.

Devices are known that prevent wire from snagging by damping vibrations. For example, a vibration damper for wires (USSR AS No. 712884, publ. 01/30/1980). Such devices are made in the form of an elastic damping element, weights fixed at the ends of this element, and a clamp for attachment to the wire. There are various design options for the dampers, as well as precisely calculated installation schemes.

The disadvantages of these devices as applied to lines with voltages up to 1000 V are economic inexpediency due to relatively short spans.

The technical objective of the invention is to improve fire safety during operation of overhead lines with a voltage of 380 V and reduce the intensity of emergency shutdowns when wires are snagged.

The technical result is to prevent the formation of fire hazard signs when the wires of the overhead line with a voltage of 380 V are clasped and to exclude an unjustified emergency shutdown during this clashing.

The specified technical result is achieved due to the fact that the device for preventing the occurrence of fire hazard signs and unreasonable emergency shutdowns when the wires of overhead power lines with a voltage of 380 V are clasped, installed in a four-wire three-phase network, includes, according to the invention, a current-limiting unit installed between the circuit breaker And three phase current transformers that are installed in the network, a short-circuit current measuring unit, a time delay unit, a logic element, a control unit, and a wind speed measuring unit, connected in series, and three inputs of the short-circuit current measuring unit are connected to the secondary windings of three current transformers, the output the short-circuit current measuring unit is connected to the input of the time delay unit, the output of which is connected to the first input of the logic element, to the second input of which the output of the wind speed measuring unit is connected, and the output is logical th element is connected to the input of the control unit, the output of which is connected to the input of the current-limiting unit.

The use of a short-circuit current measuring unit in the proposed device makes it possible to generate an output signal depending on the type and possible cause of the short circuit. This unit measures the values of short-circuit currents.

The use of a time delay unit provides control of the duration of the short circuit - when a signal is received from the short-circuit current measuring unit from one or two current transformers, a time counter is turned on, contained in the time delay unit.

The use of the wind speed measuring unit allows to determine the dangerous value of the wind speed from the point of view of the conditions of a possible collision.

The use of the control unit in conjunction with the current-limiting unit provides regulation (reduction) of the short-circuit current to values at which no fire hazard signs are formed, taking into account the cross-section of the phase wires, the values of which were entered when the proposed device was installed on the corresponding line.

The use of the logical block "AND" provides a change in the output signal (from a logical zero to a logical one and vice versa) entering the control unit.

The essence of the invention is illustrated with the help of a drawing, which shows a functional diagram of a device for preventing the occurrence of fire hazard signs and unreasonable emergency shutdowns when the wires of an overhead line with a voltage of 380 V.

A device for preventing the occurrence of fire hazard signs and unreasonable emergency shutdowns when the wires of overhead power lines with a voltage of 380 V collide (drawing), installed in a four-wire three-phase network 4 after circuit breaker 2, it includes a current-limiting unit 3, installed between circuit breaker 2 and current transformers 5, 6, 7, a short-circuit current measurement unit (BITKZ) 10 connected in series, which measures currents flowing in the network 4, a time delay unit (BVV) 11, a logical element "I" 8 and a control unit (CU) 9, as well as a block wind speed measurement (BITKZ) 12, and three inputs BITKZ 10 are connected to the secondary windings of three current transformers 5, 6, 7, the output BITKZ 10 is connected to the input BVV 11, the output of which is connected to the first input of the logic element "I" 8, the second input which is connected to the output of the wind speed measurement unit 12, and the output of the logical block "AND" 8 is connected to the input BU 9, the output of which is connected to the input of the current-limiting unit (TOB) 3.

Several possible modes of operation of the device are considered: under unfavorable meteorological conditions (under unfavorable conditions in this case we mean the wind at a speed at which the wires can collide), under normal meteorological conditions (when the wind speed is less than the lower threshold value at which the wires can collide).

The operation of the device for preventing the occurrence of fire hazard signs and unreasonable emergency shutdowns when the wires of the overhead transmission line with a voltage of 380 V clash is carried out as follows.

At a permissible, from the point of view of the conditions of a possible collision, the value of the wind speed (BISV 12 provides control of the value of this speed), the system is in standby mode, i.e. TOB 3 passes the load current. Since in this case the setpoint for the wind speed (controlled by BISV 12) is not exceeded, the output signal of the BISV 12 unit is equal to logical zero, which is fed to one of the inputs of the logical block "AND" 8, at the output of which a logical zero is also stored, supplied to input BU 9 without causing it to operate. In the event of a short circuit between the wires of the overhead line 4, when the current setting (monitored by BITKZ 10) exceeds the permissible value (accordingly, a logical unit appears at the output of BITKZ 10), the short circuit current will not be limited, because the wind speed measuring unit 12 does not confirm the creation of conditions for the wire entanglement. In this case, the resulting short circuit must be turned off by the circuit breaker 2 installed at the beginning of the overhead line 4.

In a strong wind, when the wires may clash, the setpoint for wind speed (controlled by BISV 12) is exceeded, the output signal of the BISV 12 unit becomes equal to a logical unit supplied to one of the inputs of the logical element AND 8. When a short circuit occurs at the output of BITKZ 10, a logical a unit supplied to the second input of the “AND” element 8. When two logical ones appear at the inputs of the “AND” element 8, a logical unit appears at its output, which forms a signal to turn on the BU 9, which initiates the operation of TOB 3 (conduction angles from maximum values are reduced to values that ensure the limitation of the short-circuit current), while the line is not disconnected. BU 9, taking into account the cross-section of the phase wires, the values of which were entered when installing the proposed device on the corresponding line, initiates the operation of TOB 3, while setting the current in the line at which no fire hazard signs are formed.

If the signal does not disappear at the input of BITKZ 10 after 5 s (time control is carried out by the BVV 11 time delay unit), then a logical zero is received from the BVV 11 output to the corresponding input of the "I" 8 element, and BU 9 turns off the TOB 3, and the line is de-energized to the maximum overcurrent protection of the circuit breaker 2.

If the signal to BITKZ 10 comes simultaneously from three current transformers (5, 6, 7), then there will be no signal at its output, i.e. a logical zero will be formed, since in this case we are dealing with a symmetrical short circuit caused not by the clashing of any two wires, but by some other reason. In this case, TOB 3 does not operate on current limitation, and the corresponding line will be disconnected due to the operation of the circuit breaker 2.

An example of the device.

The current-limiting unit is made in the form of three thyristor switches, which are normally open (conduction angles are maximum) and pass the load current of the overhead line. When a short circuit occurs in thyristor switches, a decrease in the conduction angles is introduced, which ensures the limitation of the short circuit current to the required values.

BITKZ consists of three blocks for comparing the current value of the phase current of the overhead line with the setting current. The setting current is determined by the value of the load current of the overhead line. In normal operation of the overhead line, when the phase currents are less than the setting current, the BITKZ output signal is equal to logical zero. When any type of short circuit (one-, two- or three-phase) occurs on the overhead line, the phase currents exceed the setting currents of the corresponding comparison units and the output signal of the BITKZ changes to a logical unit.

The wind speed measurement unit BISV contains an electronic anemometer and a wind speed converter into a logical signal with a minimum speed setting.

The time delay block contains a time counter and a closure duration converter into a logic signal with a time setting.

The AND block contains the conjunction logical block (AND gate).

The control unit CU contains a regulator of the switching angle of thyristor keys The control unit converts the logical signal of the logical element AND into the control signal of the current-limiting unit TOB.

The CU, with the output logical signal of the logical block AND equal to logical zero, sets the operating mode of the TOB with open keys and it passes the load current from the power transformer into the overhead line. When the output signal of the AND gate becomes equal to a logical unit, the CU control unit reduces the conduction angles of the thyristor switches TOB in order to limit the short-circuit current. In this case, the current in the overhead line decreases to the value of the load current.

The use of the control unit in conjunction with the current-limiting unit provides regulation (reduction) of the short-circuit current to values at which no fire hazard signs are formed, taking into account the cross-section of the phase wires, the values of which were entered when the proposed device was installed on the corresponding line.

Thus, the proposed device makes it possible to prevent the formation of fire hazard signs when the wires of an overhead power transmission line with a voltage of 380 V collide and to exclude cases of unjustified emergency shutdown during this collision.

Claims (1)

A device for preventing the occurrence of fire hazard signs and unreasonable emergency shutdowns when the wires of overhead power lines with a voltage of 380 V clash, installed in a four-wire three-phase network, including a current-limiting unit installed between the circuit breaker and three phase current transformers that are installed in the network, a series-connected current measuring unit short circuit, a time delay unit, a logical element "AND", a control unit, and a wind speed measurement unit, moreover, three inputs of the short circuit current measurement unit are connected to the secondary windings of three current transformers, the output of the short circuit current measurement unit is connected to the input of the holding unit time, the output of which is connected to the first input of the logical element "AND", to the second input of which the output of the wind speed measurement unit is connected, and the output of the logical element "AND" is connected to the input of the control unit, the output of which is connected with the input of the current-limiting block.

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