RU2127937C1 - Device for line protection in case of ice melting - Google Patents

Abstract

FIELD: power engineering; protection of overhead power transmission lines deiced by three-phase short-circuit current. SUBSTANCE: double-output transient-condition sensor, second delay element, as well as AND gate are newly introduced to record two changes in line condition; first output of transient-condition sensor is connected to input of second delay element whose output is connected to first input of AND gate; second output of transient- condition sensor is connected to second input of AND gate whose output is connected to disconnecting circuit of main deicing switch. Information about disconnection of short-circuiting switch is obtained without using special data transmission channel. EFFECT: improved reliability of disconnection of line circuit breaker in case of trouble caused by ice melting. 1 dwg

Description

 The invention relates to the electric power industry and can be used for melting ice on overhead power lines (OHL) by the method of a three-phase short circuit.

 When ice is melted by this most common method on a heated line, the protection output contactor deactivates the overcurrent protection and remains the current cut-off [1]. To ensure selective operation of the current cutoff, its operation current is set above the melting current by a safety factor. If during the smelting of ice, a wire break occurs, two-phase short circuits on the heated line or short circuits (including three-phase) on the tap, the current at the beginning of the heated line may not reach the current cutoff current. Therefore, the heated line is unprotected from such emergency conditions.

 Known remote control circuits of short-circuit breakers, that is, switches that create a three-phase short circuit, the shutdown of which after the melting is done using the minimum current relay [2]. In this case, after completion of the ice melting process on the heated line, the head switch is turned off, the current flow stops at the installation location of the short-circuit breaker, the minimum current relay trips and connects the power source (usually a capacitor block) to the short-circuit breaker shut-off electromagnet [3]. However, such circuits for closing the short-circuit breaker were not used to protect the line during melting, and the short-circuit breaker was turned off only if the head switch was turned off.

 Closest to the invention is a power line with a device for melting ice [4]. In this solution, the line is protected, that is, the head switch is turned off after the short-circuit breaker is turned off when the melting current decreases. Indeed, with two-phase short circuit, a wire break on the heated line, short circuit on the branches, the current flowing at the installation location of the short-circuit breaker decreases. It turns off, a signal is transmitted to the head switch, which is also turned off. The device consists of a power line containing an ice melting switch, a communication channel and a minimum current relay located at the installation location of the short-circuit breaker, the contacts of which are included in the circuit for disconnecting the short-circuit ice melting switch.

 The disadvantage of this technical solution is the need for a reliable channel for transmitting information from the installation site of the short-circuit breaker to the overhead switch. The transmission range is equal to the length of the heated line, that is, tens of kilometers. Transmission using, for example, a radio channel has a limited duration, depending on the configuration of the route, etc. Using the wires of a heated line requires additional processing of the RF signal, and, in addition, in the considered modes, for example, wire breakage, it can turn out to be an unreliable method.

 The task to be solved by the claimed invention is aimed at increasing the reliability of tripping a line circuit breaker in case of damage on it in the ice melting mode by obtaining information about tripping a short-circuit breaker without using a special information transmission channel.

 The problem is solved in that in a device for protecting the line during ice melting, comprising an ice melting switch, a minimum current relay, a first time delay element located at the installation location of the short-circuit breaker, the minimum current relay contacts being connected to the input of the first time delay element, a transient sensor with two outputs, responsive to the rate of change of current or the presence of an aperiodic component, a second time delay element, an AND logic element, the first the output of the transient sensor is connected to the input of the second time delay element, the output of which is connected to the first input of the logical element And, the second output of the sensor of the transition mode is connected to the second input of the logical element And, the output of which is connected to the trip circuit of the melting head switch.

 Figure 1 presents the structural diagram of a device for protecting the line when melting ice.

 It contains a power line 1 with a branch 2, fed through the head switch 3 from the source of melting ice 4. At the end of the line there is a short-circuit breaker 5, which is equipped with a minimum current relay 6 and the first time delay element 7 with a certain time delay. On the side of the main switch, a transient sensor 8 with two outputs is installed, which can be used as current sensors that respond to the rate of change of current. The first output of this sensor through the second time delay element 9 supplies a signal to the first input of the logical element And 10, the second output of the sensor 8 is connected to the second input of the logical element 10 directly. The output of the logic element 10 is connected to the trip circuit of the head switch 3. As a logical element And microchips of any series can be used, for example, K155LI.

 The introduction of the transient sensor 8 allows the device to not work, for example, with a decrease in the melting current at the end of the melting process. The presence of two outputs allows the circuit to work only if two conditions are met - the presence of a transient at the initial moment of operation of the device and a change in the operating mode after a strictly defined time, corresponding to the time of disconnection of the short-circuit breaker 5, which increases the noise immunity of the circuit. So, in case of a short circuit on another line 1, the transient sensor 8 is triggered and sends a signal to element 9, if the second output is also triggered during automatic reclosure, then by this time the signal will not go from the first output, since the time delay of element 9 is equal to the time delay of element 7 at short-circuit breaker 5 and detaches from the reclosure time. Logic element 10 allows the device to work only with the simultaneous receipt of signals from both inputs.

 The device operates as follows.

 When melting ice short-circuit switch 5 is on, the current relay 6 has open contacts. If damage occurs on line 1, a transition mode occurs, and differential link 8 is activated, from the first output of which a pulse is applied to the time delay element 9. At this time, due to a decrease in current at the installation location of short-circuit breaker 5, the undercurrent relay 6 trips and after a while corresponding to element 7 turns off the short-circuit breaker. There is again a transition mode, which is recorded by the transient sensor 8, and from its second output, power is supplied to the second input of the element And 10. By the same time, the time delay on the element 9 ends and a signal is also sent to the first input of the element And 10. From the output of the And element, power is supplied to the tripping electromagnet of circuit breaker 3. The circuit may not work with three-phase short circuits close to a short-circuit breaker, but, firstly, the repeatability of three-phase short circuits is small, and secondly, near the installation location of a short-circuit breaker, interphase voltages are close to zero , which leads to a very low probability of this type of damage.

 Sources of information.

 1. Santotsky V. G. Automatic control of short-circuiting apparatus during ice melting during ice melting in 10 kV networks. // Electrical stations, 1971, N6.- 51-52.

 2. A.c.N 599306. A method for remote control of a shorting apparatus during ice melting / Rudakova R.M., Kazadaev A.P., Guzairov MB Publ. in B.I., 1978, N11.

 3. A. p. N 752588. A control device for a short-circuit breaker in ice melting circuits. Rudakova R.M., Usmanov F.Kh., Guzairov M.B., Kurbanov I.G. Publ. in B.I., 1980, N 28.

 4.A.S. N1387086. Power line with a device for melting ice. Livshits A.L. Publ. In BI N3.1988.

Claims (1)

 A device for protecting the line during ice melting, comprising an ice melting switch, a minimum current relay, a first time delay element located at the installation location of the short-circuit breaker, the minimum current relay contacts being connected to the input of the first time delay element, characterized in that a sensor is inserted into it transition mode with two outputs, the second time delay element, AND gate, and the first output of the transition sensor connected to the input of the second time delay element, output which is connected to the first input of the AND gate, the second output of the transient sensor is connected to the second input of the AND gate, the output of which is connected to the trip circuit of the melting head switch, and the output of the first time delay element is connected to the trip circuit of the shorting circuit breaker.