SU655006A1 - Device for selective protection from earthing in mains with insulated neutral wire - Google Patents

Description

Of the known devices for selective protection against earth faults in networks with insulated neutral, the closest to the technical essence is a device for protection against earth leakage without using an alternating operating current of a lower frequency 4, consisting of a source of operating current, an auto-regulator, , local filters and amplifiers. As a source of operating current, an electromagnetic frequency divider is used, which is connected to the protected network through an attachment filter consisting of a three-phase throttle and capacitance. The single-phase choke and capacitor are a resonant circuit that adjusts to the operating current frequency. The disadvantage of this device is that the operating current source in it operates continuously, as a result of which reliability is reduced.

The aim of the invention is to increase the reliability of the device.

This goal is achieved by introducing a trigger into the network-wide block of automatic insulation resistance control, the first output of which is connected to the trigger input of the non-industrial frequency generator, and the second output is connected to the operating winding of the output relay, the blocking winding of which through the storage capacitor and auxiliary power remote control wires The cable is connected to the first output of the trigger in the protective disconnecting unit at each connection of the trigger, the second output of which is connected to you one relay, and an input connected to said rectifier. The zero sequence signal sensor is designed as a zero sequence voltage filter.

The drawing shows a block diagram of a device for selective protection against earth faults in a network with insulated neutral.

A network-wide unit 1 for automatic control of insulation resistance is installed in the node of the local area network; its functions are performed by a protection device containing a voltage filter of the bullet sequence 2, to the output of which an electronic amplifier 4 is connected through the band-pass filter 3, to the output of which through the rectifier 5 a trigger 6 is connected, which serves to start the generator of a non-flash-frequency 7, and the last-night output is connected through the attachment filter 8 to three conductors 9 of the power cable 10. In addition, to the output Trigger 6 has an operating winding 11 of output relay 12 connected, contacts KOTOpojo iiaxod in the circuit of the tripping coil 13 of the automatic feeder switch (AFV) 14. Output relay 12 has an interlock winding 15, which is connected to two terminals dnstappo P10 through the storage capacitor 16. control cable 17 of the power cable 10. A network-wide unit 1 controls the operation of the AFL 14, from which electric power is supplied to the power cable 10 to explosion-proof intrinsic starters 18, through which line 19 (L), JIj, etc., to the armored cable 10. e.) consumer th power. Each of these starters has a protective disconnecting unit 20 (BZb BZ, etc.) containing a bullet current detector (FTNP) 21 filter, to the output of which, through a non-saturated frequency current filter 22, a foam-amplified current amplifier is connected 23, to the output of which, in turn, through the driver 24 of the key switch trigger 25, and the output winding of the output relay 26 of the unit 20 is connected to its output, the contacts of which are located in the winding circuit of the disconnector 27 of the trigger 18. In addition, to the output of the trigger 25 connected two cores distance One control 17 power armored cable 10.

The device works as follows.

Reducing the insulation resistance relative to the earth at one or two phases of any of the lines 19 (for example, line L) at the output of the voltage filter} of the electrical grid 2 of the power grid appears a signal of zero zero continuity, which is fed to the bandpass filter 3. Nose filter 3 is necessary to suppress all signals, except the zero sequence voltage signal, which is amplified by amplifier 4, rectified by rectifier 5 and fed to the input of trigger 6, which is then thrown and triggers the low-frequency generator 7, low-frequency pulses from it through the attachment filter 8 through three conductors 9 of the power cable 10 are sent from the grid node to all lines 19 of the power supply network that connect the power armored cable 10 to the power cable 18 via the start-up unit. output Tj) Hrrepa 6 receives the working winding 11 of the output relay 12; the disconnection of the entire power grid will not occur, since at the same time the impulses of the low frequency current pass through the armored cable 10, but one of the lines 19 (nanometer, JIi), which received Intervention, at the site of damage 28 through the ground 29, and it goes to the low-frequency generator 7.

Thus, the loop for the LF currents is closed through the damage site 28 of lipia 19 (L)). For the other lines (Lg, etc.), the LF current does not flow, since there is no closed loop for it. The occurrence of an LF current through a fault contact causes the appearance of a weak IF signal in the filter and a zero sequence current 21. In addition to the LF signal, the output of the FTNP 22 filter also contains a zero sequence current signal. From the output of the filter 21, the total signal is fed to the input of the filter for the low-frequency currents 22, where the low-frequency current signal is filtered from the zero current signal and the network, then the filtered low-frequency signal from the output of the filter 22 is passed to the electronic amplifier 23, and from its output a trigger is fed through 24 25, which as a result of this, overturns, turns on the output relay 26 of the protection unit 20. And with its contacts it turns off the power supply to the winding 27 of the actuator 18, and the contacts 30 and the actuator 18 open, disabling the emergency line 19 (L). At the same time, from the output of the trigger 25 via the two cores of the remote control 17, the interlock capacitor 15 of the output relay 12 is powered through the storage capacitor 16 for some time, and the relay is locked. Therefore, while the contacts 30 and the trigger 18 of the damaged line 19 (L) are triggered, the network-wide unit 1 does not disconnect the entire power grid. After 1-2 seconds, the storage capacitor 16 is charged, the current in the interlock winding 15 almost disappears, and the protection device is unlocked. But the damaged line 19 is already disconnected, and the grid will continue to work. Thus, selectivity of protection is provided.

In case the damaged one is not disconnected by its own protection device during the blocking time, the protection device and after unblocking it will disconnect the entire sub-grid. If the damage to the line, nai.mer L2, is not turned off by the contacts of the 30 PVM sockets, although 6; iOK of the actuator will work, then after blocking, the protection switch will disconnect the entire local power grid. This ensures redundancy of local line protection devices. In the case of a gate: and in the power cable 10 of the network-wide bl (the KOHI role is 1 mg} and it will simply disconnect the entire network, since in this case the loop for low frequency currents does not cover the lines. The proposed device increases the sensitivity of protection and cnoco6) io ensure selectivity, continuity KOirrpo; | isolation, redundancy and performance.

An experimental sample of this device for protection against earth faults in the underground electrical network has shown, in the laboratory, reliable operation with a single-phase leakage resistance of 80 kΩ and a earth fault current of 2.75 mA (mains voltage of 380 V). In the known devices iri6ch 380V single-phase resistance of the wiki P; .H; IO 6000 Ohm; 6,660 V single-phase leakage resistance 11000-14000 Ohm; The single-phase leakage resistance is 40,000 ohms.

F o) m y, 1 a and 3 o b e e e u u

Claims (4)

1. A device for selective protection against earth locking in an insulated neutral network containing a network-wide automatic isolation control unit installed} ia to the remote end of the loose cable connected to an automatic feeder switch and made on a non-hygroscopic current generator connected to the protected the network through an attachment filter and having a connection to the ground, on the carrier connected to the zero-sequence signal sensor, band-pass filter, silytel and rectifier and at the output by the bottom of the relay, the protective disconnecting unit at each location, performed in series with the zero-sequence current filter, current-frequency-frequency filter, amplifier, rectifier, and output relay connected to an explosive-hazardous starter, which is the only reason reliability, a trigger is added to the network-wide block of automatical control of the C01 rotivle} 1 and isolation, the first output of which is connected to the trigger input of the generator and its frequency loop, and the second BI input to the working the output relay, whose interlock winding through the accumulative capacitor and auxiliary conductors of a distant wired power cable is connected to the first output of the protective disconnection unit: at each connection of the pschter, the second output of which is connected to the output pe, i.e. connected to specified find out. 2. The device according to claim 1, of which the sensor of the signal of zero continuity is taken out in the form of a filter and a direct sequence of zero sequence. Source of information Irish exerti.che 1. Leibov R.M. Leaks in smart electrical networks, M, Ugletekh1 zdag 1952, p. 304-305, Fig. 118. 2. Shutsky V. 11. 1 p. The experience of the use of protective devices in electric systems and international systems up to 1000 V. .1., ZPPEM, 1970, p. 13. 3.Shiunov M.V. Zashchitnoye otk.iocheeie, L., “Energy, 9ti8, fig. 7--5. 4. Avtorskoe sni.i-tei i tvvo USSR LL 180238, cl. H 02 H 3/16, 19 (53. 18 21