SU892557A1 - Device for earth protection in network with insulated neutral wire - Google Patents

Description

(54) DEVICE FOR PROTECTION AGAINST LOCK ON GROUND IN A NETWORK WITH ISOLATED

The invention relates to electrical engineering, in particular to devices for protection against earth faults in networks with insulated neutral.

A device for protection against earth faults in insulated neutral networks contains a zero-sequence voltage transformer, to the secondary winding of which a starting element is connected, zero-sequence current transformers, secondary windings of which are connected to reacting bodies, and actuators to.

A disadvantage of this device is the possibility of non-selective actuation from its own capacitive currents.

The closest in technical essence to the present invention is a device for protection against earth fault, which reveals the damaged phase, connects to the damaged NEUTRAL

the phase of the reference generator with a grounded pole, forming a circuit for the flow of the current of the reference generator through the fault, in case of exceeding the specified current of the set point of the actuator, the latter is triggered 2.

However, the known device can work nonselectively in networks with a large capacitive current. The presence of a reference generator complicates the device and increases power consumption.

The aim of the invention is to reduce power consumption and increase selectivity.

This goal is achieved by the fact that a device containing a zero-sequence voltage transformer, to the output of which is connected a starting organ, selector of the damaged phase, whose inputs are connected to the network through a transformer. voltage matrix, zero sequence current transformer, k

The secondary winding of which is connected to the reacting body and the executive body is equipped with an automatic phase disconnecting unit for the power supply network switch, an automatic phase switching unit for the power supply network switch, an additional switch, an additional switch control unit, a single-action support unit and power supply position sensors, respectively, for the power supply phase switch, the switch of accession and the additional switch, at the same time exits the elector of the damaged phase Connected to the inputs of the aforementioned automatic shutdown unit, to the trigger input of which the output of the triggering organ is connected, to the blocking input is connected the output of the one-time operation unit, the inputs of which are connected respectively to the output of the control unit with an additional switch, to the output of the said automatic shutdown unit of the automatic switch-on unit, the inputs of the latter are connected respectively to the output of the unit for one-time operation, to the output of the starting To the outputs of the position sensors of the connection switch, position sensor of the additional switch, and position sensors of the phase switch of the power source, the outputs of the latter are also connected to the inputs of the control unit by an additional switch, the output of which is connected to the control input of the disconnecting key connected parallel to the secondary winding of the current transformer sequence, and the above-mentioned voltage transformer is connected to the terminals of the power source of the network up to the phase switch of the source pi tani.

The drawing shows a block diagram of the device.

The device contains a voltage transformer with a secondary winding connected in an open triangle, which is a zero-sequence voltage transformer (TNNP) 1 connected to the terminals of the mains power supply, a trigger (2) connected to the secondary open winding of the TNNP at the output which is the zero sequence voltage.

damaged phase selector (IPF) 3, the inputs of which are connected to the secondary winding of the transformer 1, cot with a single star, the unit automatically

disconnecting the phases of the power supply network (BAOF) k, the inputs of which are connected to the outputs of the IPF 3 and to the output of software 2, and the outputs to the disconnecting circuits of phases 5-7 of the input switch (not shown),

a power source automatic switching unit of a power source of a BAVF 8 network, the inputs of which are connected to the output of software 2 and to the disconnected position sensors (DOP), input switch phases and to DOP 12, 13 switches 1A and 15 installed respectively in the power supply neutral and on the protected connection (lines) 16, a zero-sequence current transformer (TTPC) 17 installed at connection 16, the breaker key 18 and the reacting element (PO) 19, made in the form of a trigger, the output of which is connected to the secondary winding of which n to the executive body (IO) 20, the control unit (CU) 21 with an additional switch 1A, the inputs of which are connected to the outputs OP. 9-11, PO 2 and PO 19, and the outputs to the control input of the switch 18 and to the control circuit of the switch H (not shown), the unit for providing a one-time operation of the device (BOOD) 22 connected to the BAOF k, BAVF 9 and BU 21, a resistor 23 connected between the switch k and the ground,

IAP 3 selects the damaged phase. BAOF 4 simultaneously disconnects two healthy phases of the network, and

The BAVF 8 re-enables them after a certain period of time after switching off the switches 1 and T5.

BAOF also performs the disconnection of all phases of the input switch in case of failure of protection of line 16 or the non-connection of the switch 15.

0 block contacts of their switches.

Claims (1)

The control unit 21 provides automatic shutdown and switching on of switch 1 after a specified period of time. Its shutdown is performed after a time sufficient for reliable operation of the PO 19BoED 22 eliminates the possibility of repeated operation of the device in the event of failure of any element or node. The device works as follows. In the absence of an earth fault, the phases of the input switch and the switch 15 are on, and the switch I is off, software 2, PO 19, IO 20 are in the initial state. Key 18 lock whip. This eliminates the false operation of the PO 19 from the surge of its own capacitive currents during external ground loops. The signals at the outputs of the sensors 9-13 are missing. When a single-phase ground fault occurs on line 16, for example, at the lower phase at point K 1, software 2 is triggered, which sends signals to the inputs of BAOF t, BAVF 8, BU 21. At the same time, a signal indicating the damaged phase appears at one of the BAOF inputs, and at the two outputs of this block, signals appear in the 6.7 switch-off circuit of the healthy phases. After they are turned off, the signals appearing in BAVF 8 and control unit 21 appear at the DSP 10, 11 outputs. The latter generates a pulse to turn on the switch 1 and open the switch 1 The switch T turns on and the supply network neutral is connected to ground via a resistor 23 . The magnitude of the resistance of the resistor 23 is selected from the condition of reliability of operation of the PO 19 and electrical safety. Phase 5 i. damaged, remains in the on position. This creates a closed loop formed by the point K 1, the wire of the lower phase of the line 16, the switch 15, the phase switch 5, the lower winding of the power source, the switch 14, the resistor 23 and the ground. In this circuit, a ground fault current flows due to the phase voltage of the damaged phase. As a result, RO 19 and IO 20 are triggered and switch 15 is turned off. After this, switch 14 is first switched off, then phase-disconnect switches 6 and 7 are turned on with the help of BAVF 8 and the pre-emergency mode is restored in the network. When a single-phase circuit is closed on the mains tires, for example at point K 2, first the healthy phases of the input switch (6 and 7) are disconnected, then the switch 14 is turned on and PO 19 connected to the TTPV 17 secondary (by unlocking the key 18). Since the point K 2 is outside the working area of PO 19, the latter does not work. In this case, after a certain period of time, the CU 21 turns off the switch 14, and the BAOF 4 turns off the phase 5 of the input switch. The automatic switching on of phases 6 and 7 of the input switch does not occur. Similarly, the device operates when the circuit on the other phase. Introduction to the device of an additional switch with a control unit and a series-connected resistor, automatic shut-off and re-switching of the phases of the input switch with phase control, as well as a disconnecting key, with which the reacting element is put into operation, allows to perform on the basis of simple current relays elements are reliable protection against earth faults, the selectivity and sensitivity of which do not depend on the magnitude of their own capacitive currents, changes in network parameters, etc. Claims An apparatus for protection against earth fault in an insulated neutral network containing a zero-sequence voltage transformer, to the output of which a triggering organ is connected, a fault phase selector, whose inputs are connected to the network via a voltage transformer, a zero-sequence current transformer The coil of which is connected to the reacting body and the executive body, characterized in that, in order to reduce power consumption and increase selectivity, it is provided About the unit for automatically disconnecting the phases of the power supply network switch, the unit for automatically switching the phases of the power supply switch of the network, an additional switch, the control unit for the additional switch, the unit for providing one-time operation and position sensors of the corresponding phase switch for the power supply, connecting switches and additional