RU2663413C1 - Overhead power transmission line automatic re-closure method - Google Patents

Abstract

FIELD: electrical equipment.SUBSTANCE: according to the overhead power transmission line (OPTL) automatic re-closure method, applying voltage to the transceiver, whose load is one of the transformer windings, and this transformer another winding is included into the OPTL cable metal sheath earthing circuit. From the transmitter output through the transformer supplying the continuous signal to the OPTL cable metal sheath, from the receiver output supplying the control signal to the logic circuit, from the relay protection kit output supplying the switching on / off signal to the logic circuit via the switch terminals system. At that, the signal to the cable metal sheath is supplied in the form of continuous signal with frequency, which is a multiple of 50 Hz, connecting the receiver to the overhead power transmission line current transformers outputs, and permission for the overhead power transmission line automatic re-closure is issued from the logic circuit output to the relay protection kit in the event of coming through the metal sheath to the cable conductors continuous signal absence, and then through the current transformers to the receiver input.EFFECT: enabling the authorization signal issuance for re-closure, if the fault occurred only in the overhead power line air sections.1 cl, 1 dwg

Description

The invention relates to the field of electrical engineering and can be used for cable overhead power lines.

According to the Electrical Installation Rules [Electrical Installation Rules (PUE), 7th edition (approved by Order of the Ministry of Energy of 08.07.2002. No. 204], clause 3.3.2. "... Automatic re-activation (AR) of air and mixed (cable- ") air lines of all types of voltages above 1 kV. Refusal to use automatic reclosure must be justified in each individual case."

However, in electrotechnical practice there are no typical technical solutions that provide ARs for high-voltage cable-air transmission lines (for example, 110 kV and higher).

To ensure economic efficiency, high-voltage cable-air power lines are used in the area of megacities. At the same time, from the point of view of safety and the prevention of personal injuries, it is advisable to implement the automatic reclosure of cable-overhead power lines in case of damage in the air sections and prohibit the reclosure in case of damage in the cable sections. Indeed, re-supplying high voltage to the high-voltage cable passing in the area of residential buildings can lead to significant damage, injury and even death. At the same time, transitions of cable sections into air ones, usually performed directly on power transmission towers, are of particular danger. It should be noted that on high-voltage cables, as a rule, there is no mechanism for self-repair of damage and for voltage re-supply they should be tested.

Therefore, for effective AR of high-voltage cable-air power transmission lines, it is necessary to determine with high accuracy on which of the areas (air or cable) the damage occurred and, when the damage is eliminated in the air section, to realize the AR of power transmission lines.

From the point of view of the above logic, the existing methods of AR-LEP [For example, Bogorad A.M., Nazarov Yu.G. Automatic reclosing in power systems. - M .: "Energy", 1969.] for cable lines are not directly applicable.

A known method of automatically reconnecting a power line [RF Patent No. 2365013 IPC H02H 3/06, publ. August 20, 2009], in which AR is performed in case of a positive result of the diagnosis of the status of power lines, the diagnosis of the state of power lines is carried out by receiving and analyzing at each phase continuous high-frequency signals containing at least one information sign of the performance of power lines or the presence of permanent damage, the reception and analysis of high-frequency signals is carried out at one end of the line, and informative signs are formed on the basis of the intrinsic and mutual resistances of the phases of the power lines at different frequencies.

However, the application of the known method and the corresponding AR devices is difficult on cable-air transmission lines because of the reflections of continuous high-frequency signals at the junction of cable and air sections, since each of the sections differs significantly in the values of wave impedances.

The closest technical solution to the alleged invention is a method implemented in a device for frequency current protection of cable lines [RF Patent No. 2094920 Device for frequency current protection of cable lines, H02H 7/26, publ. 10.27.1997], containing equipment blocks at the supply and receiving substations, connected by a communication channel, each of which includes a frequency signal transceiver, a logic circuit, a cable line switch with a drive and a trip coil, and a set of current transformers, an equipment block at the supply substation contains a set of maximum current protection, the input of which is connected to the output of the set of current transformers, and the output with the trip coil of the cable line switch drive, the circuit breaker drive contains make and break contacts, the input logic circuit is connected to the output of the transceiver receiver, one output is connected to the input of the overcurrent protection kit, and the other output is connected to the input of the transceiver transmitter through the break contact of the drive of the switch, the make contact of the drive of the switch is included in the power supply circuit of the transceiver and logic circuit, the logic circuit at the receiving substation at one input is connected to the output of the set of current and voltage sensors, the inputs of which are connected to the output a set of current transformers and a voltage transformer at the receiving substation, at the second input with the output of the transceiver receiver, and at the output with the trip coil of the cable line switch drive. According to the proposal, the communication channel is formed by a metal sheath of the cable and ground, connected by grounding conductors, a frequency signal transformer is introduced into each unit of the equipment, one of the windings of which serves as a grounding conductor, and the other is connected to the transceiver, while the logic circuit at the power substation is designed to provide shutdown cable line circuit breaker without time delay during a short circuit in the zone between the current transformers of the supply and receiving substations and ensuring a selective work overcurrent protection when a short circuit is in this zone, the logic circuit on the receiving substation is arranged to provide a short transceiver receiver power on and off switch of the cable line after the circuit breaker on the supply cable line substation.

The device operates as follows:

a) in the normal mode of operation of the power supply circuit and with a through short circuit (not in the device coverage area). During normal operation of the power supply at the receiving substation, the output of the set of current and voltage sensors has an output voltage (the set of sensors can be implemented as a power supply unit for current (BPT) and voltage (BPN)). This voltage is supplied to the transceiver and through the isolation diode to the capacitor. The transmitter load is one of the transformer windings, the other winding of which is included in the ground circuit of the cable’s metal sheath. In the ground loop, the sheath of the earth cable circulates the generator frequency signal. At the supply substation, a transformer is included in this circuit. One of its windings is included in the grounding circuit of the metal sheath of the cable, and from the output, another signal is supplied to the transceiver. In the transceiver only the receiver (amplifier) works. The supply voltage is supplied to it through the make contact of the switch. From the output of the receiver, a high-frequency signal is fed to a logic circuit. The logic circuit includes a sawtooth voltage generator (GPN), a threshold element, a single-acting relay, an isolation diode, a capacitor. In the presence of high-frequency signals in the GPN circuit, sawtooth-shaped signals are generated, and the maximum voltage value of these signals is much lower than the threshold threshold element. Since the switch is on, the capacitor will be constantly recharged through an isolation diode.

With a short-circuit fault at the receiving substation, the generator will continue to work, since voltage will come from the output of the kit. At the power substation, the state of the logic circuit will also not change. However, overcurrent protection, including current relays and time relays, will start to work. At the same time, MTZ will start working on the feeder where the short circuit occurred. But since the setting for the time relay in the MTZ scheme of the outgoing line of the receiving substation is less than the time setting for the relay, the damaged section will be disconnected, and the switch will remain on;

b) with a short circuit in the cable. If there is a short circuit in the cable at the receiving substation, there will be no voltage at the output of the kit. The generator will stop working. There will be no high-frequency signals at the output substation at the output of the receiver, therefore, the operation of the SPS will stop and at its output the voltage will reach the threshold value. From the output of the threshold element, the signal is fed to a single-acting relay. The peculiarity of the circuit of this relay is that when a signal is applied, this relay operates instantly, but after 0.5-1.0 s its contact opens even if there is a signal to operate. Returning to the initial state is done by removing the supply voltage from the relay. The relay contact is switched on in such a way that the signal from the contacts of the current relays is applied to the trip coil of the switch. Thus, during short circuit in the cable, the current relays instantly operate in the cable and the relay works almost instantly (the delay is determined by the rise time of the voltage on the GPN). Thus, the time relay is excluded from operation during short circuit in the cable.

When the switch is turned off, its block contacts are switched. The voltage is removed from the receiver and from the logic circuit. The supply voltage to the transmitter is supplied from the capacitor through the opening block contact of the switch. The transmitter provides a high frequency signal to the communication channel during the discharge time of the capacitor. This high-frequency signal is transmitted through the communication channel to the transceiver. In the absence of voltage from the kit, the supply voltage to the receiver of the transceiver comes from the capacitor. The high-frequency signal through the NC contact of the voltage monitoring relay is fed to the thyristor control electrode. The thyristor turns on the relay. The relay supplies voltage to the circuit breaker coil.

Thus, with a short circuit in the cable, the damaged cable is almost instantly disconnected on both sides. Opening the circuit breaker will activate the device for automatically turning on the backup power of the receiving substation. Thus, the device allows you to quickly restore the voltage at the receiving substation with short circuit in the cable.

A distinctive feature of the device is the ability to transmit a signal about a short circuit in the area of the protected line through the grounded cable sheath.

The disadvantage of the prototype method is that it is intended only for cable power lines, involves the placement of equipment at both ends of the cable line and it is impossible to use it for automatic overhead cables.

Currently, there is a known technical solution for the AR of cable-overhead power lines developed as a result of R&D in PJSC MOESK [Dogadkin D., Marine R., Shirshova E., Ismukov G., Kulikov A., Lint M., Podshivalin A. Device automatic re-inclusion of cable-overhead power lines of megacities // Electricity. Transmission and distribution. No. 5 (38). 2016 p. 114-119.]. The basis of this technical solution is a patent for a utility model [Patent for a utility model of the Russian Federation No. 1655635 Device for automatically re-activating a cable-overhead power line H02H 03/06, G01R 01/00, publ. 10/27/2016, B.I. No. 30]. A functionally appropriate device involves the detection of damage in the air areas and, when they are eliminated, permission to re-enable the cable-air power line. However, a prototype of such an automatic reclosure device is quite difficult to implement, since it includes a wave-based fault location device (WMD) and an active sensing device using complex modulated high-frequency signals.

When a cable-overhead power line includes only cable approaches to substations or there are cable inserts on overhead power lines with corresponding transition points at the junction of cable and air sections, the task is greatly simplified.

In this case, it is advisable to monitor only the state of the high voltage cable. The simplest technical solution will be to supply a special signal to the metal sheath of the cable. Damage to the high-voltage cable is accompanied by arc faults with violation of insulation and overlapping on the metal sheath of the cable. In this case, a special signal is supplied to the cable cores. The fact of the presence of a special signal on the cable cores indicates damage to the cable section of the cable-air power line. In case of damage in any of the air sections, there will be no special signal on the cable conductors. Thus, absolute selectivity is achieved when determining a damaged air or cable section of a power transmission line.

It should be noted that to simplify the technical solution, it is advisable to use a special continuous frequency signal that is a multiple of 50 Hz, for example, 200 Hz. At the same time, current transformers can be used as current sensors for detecting such a signal, and the receiving device can be performed, for example, according to the principle of the usual maximum current protection tuned to a frequency of 200 Hz. The special signal transmitter is also simple as a frequency multiplier of 50 Hz. Additionally, a frequency signal of 200 Hz is suppressed in the measuring bodies of digital relay protection [eg, Schneerson E.M. Digital relay protection. - M .: Energoatomizdat, 2007.], so that the generated special signal will not affect the relay protection.

Thus, the implementation of the AR of cable-overhead power lines, taking into account the above features, greatly simplifies the technical performance of the corresponding device.

The objective of the invention is the creation of a method of automatic reconnection for cable-overhead power lines, which ensures the issuance of an enable signal for reconnection if damage has occurred only in the air sections of the power lines.

The task is achieved by the method of automatically reconnecting the cable-overhead power line (PTL), according to which voltage is supplied to the transceiver, the load of which is one of the transformer windings, and the other winding of this transformer is included in the ground circuit of the metal sheath of the power transmission cable, from the output of the transmitter a special signal is fed through the transformer to the metal sheath of the power line cable; from the output of the receiver, the control signal is fed to the logic circuit, the on / off signal li ne set from the output protection relay through a contact breaker system is fed to the logic circuit. According to the proposal, the receiver is connected to the outputs of the current transformers of the cable-air power line, and permission to automatically reconnect the cable-air power line is issued from the output of the logic circuit to the relay protection kit in the absence of a special signal coming through the metal sheath to the cable conductors, and then through the transformers current to the input of the receiver.

The proposed method for automatically reconnecting a cable-air power line can be implemented by the device shown in FIG. one.

The device (Fig. 1) includes: a transceiver 1, consisting of a transmitter 2 and a receiver 3; switch 4; current transformers 5; relay protection kit 6; logic 7; special signal transformer 8.

The method is implemented as follows.

A voltage is supplied to the transceiver 1, which ensures the functioning of the transmitter 2 and receiver 3. The transmitter 2 generates a special continuous signal (for example, a frequency of 200 Hz), which, through a special signal transformer 8, enters the metal sheath of the cable. As the transformer of the special signal 8, a conventional current transformer can be used, and a special signal from the output of the transmitter 2 is supplied to the secondary winding of the current transformer.

Thus, the load of the transmitter 2 is one of the windings of the transformer of the special signal 8, the other winding of which is included in the ground circuit of the metal sheath of the cable. A special continuous frequency signal of the transmitter 2 circulates through the metal sheath of the cable.

In the normal mode of operation of the cable-air power transmission line, as well as during short circuit in the air sections of the power transmission line, since the internal insulation of the cable is not damaged, a special signal of the frequency of the transmitter 2 does not enter either the cable conductors or through current transformers 5 to the input of receiver 3. Accordingly, the control signal with the output of the receiver 3 does not go to the input of the logic circuit, therefore, an output signal from the output of the logic circuit 3 is issued to the relay protection kit 6 on the automatic reclosure cable-air line. Therefore, in case of damage in the air section of the cable-air transmission line, its automatic reclosure occurs.

With a short circuit on the cable, the internal insulation of the cable breaks into the metal sheath. A special signal from the output of the transmitter 2, through the transformer of the special signal 8, the metal sheath of the cable, the core (s) of the cable, the transformer (s) of current 5 is fed to the input of the receiver 3. Receiver 3 captures the special signal of the transmitter 2 and sends the control signal to logic 7 . If there is a trip signal of switch 4, as well as the control signal received from the output of receiver 3, logic 7 generates a signal that prevents the automatic reclosure of the cable-air power line to relay protection kit 6, since the receiver 3 cable damage is encoded.

Thus, the proposed method of automatic reconnection for cable-overhead power lines implements the objective of the invention - provides the issuing of an enable signal for reconnection if damage occurred only in the air sections of the power lines and prohibits automatic reclosure in case of damage to cable sections.

In addition, it should be noted that the proposed AR method of cable-overhead power lines also prohibits the manual inclusion of power lines in case of damage on cable sections, for example, when putting it into operation from repair.

Claims (1)

A method for automatically reconnecting a cable-overhead power line (power transmission line), according to which voltage is supplied to a transceiver, the load of which is one of the transformer windings, and the other winding of this transformer is connected to the ground circuit of the metal sheath of the power transmission cable, a continuous signal is supplied from the transmitter output through the transformer on the metal sheath of the power line cable, from the output of the receiver, the control signal is fed to the logic circuit, the on / off signal from the output of the relay kit protection through the contact system of the switch is fed to a logic circuit, characterized in that the signal to the metal sheath of the cable is supplied as a continuous signal with a frequency that is a multiple of 50 Hz, the receiver is connected to the outputs of the current transformers of the cable-air power line, and permission to automatically turn on the cable an overhead power line is issued from the output of the logic circuit to the relay protection kit in the absence of a continuous signal coming through the metal sheath to the cable conductors, and then through current transformers to the input of the receiver.

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