SU845214A1 - Device for protective cutout of electric installation in three-phase ac network with neutral wire - Google Patents

Description

(54) NIKOLAEV'S DEVICE FOR PROTECTIVE DISCONNECTION OF ELECTRICAL INSTALLATION IN A THREE-PHASE AC NETWORK WITH ZERO WIRE

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The invention relates to electrical engineering, and specifically to protective disconnecting devices operating on operating alternating current, and is intended for use in all sectors of the national economy in the operation of various machines powered from three-phase networks with a deafened grounded neutral, agricultural objects (livestock), especially boosted cranes in construction, requiring increased electrical safety.

Protective disconnect devices are known 1.

These devices do not exclude the use of protective earthing and zeroing, since under normal conditions they cannot be adjusted for all cases of contact with the current-carrying parts of one of the phases - especially with a “non-admitting current of not more than 5 milliamperes. In addition, there is no continuous automatic control for an open ground circuit and a neutral wire at the consumer-current source section, no automatic control of the increase of the ground resistance and the neutral wire, there is no possibility to quickly measure the resistance of the ground circuit and the neutral wire at the consumer-current source device setting cCvieKTHBHoM for various operating conditions.

The closest solution to the technical essence and the achieved result of the invention is a device for protective disconnection of an electrical installation in a three-phase AC network 2. It provides protection from deafening to the housing, controls the compliance of the resistance of the grounding circuit to the vanishing value, and the voltage of the neutral wire is safe size, allows for selective adjustment. However, connecting a dead-circuit latching relay and a neutral-wire resistance control relay to a single power source reduces the reliability of the device.

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

To do this, in a known device containing an operating current transformer, the primary winding of which is connected to the network via a switch, the first secondary winding is connected to the dissecting of the neutral wire and connected in series with the primary winding of the measuring transformer

the current, the secondary winding of which is connected via a rectifier to the winding of the neutral wire resistance control relay, and the second secondary winding of the operating current transformer is connected to the alarm element, the dead fault latching relay and the actuator, the dead winding relay winding through the newly introduced first additional rectifier and an adjustable resistor is connected to the said connected in series secondary winding of the operating current transformer and primary winding of the measuring trans current format transformer, the secondary winding of which is connected in series with the newly introduced additional secondary winding of the operating current transformer, to which a rectifier is connected, connected to the winding of the neutral conductor resistance control relay, shunted by the newly introduced charging capacitor, parallel to the second secondary winding of the operational current transformer through the connected in series closing contacts of the relay to monitor the resistance of the neutral wire and the opening contacts of the relay Blind circuits are connected to a second additional rectifier and a winding of an intermediate relay, newly connected in parallel, the closing contacts of which are included in the power supply circuit of the actuator, the primary winding of the operating current transformer transformed by the first additional capacitor, through a second additional capacitor and a resistor connected to the switch .

In this case, the switch is provided with contacts of antiphase connection and contacts of zero connection, and parallel to the winding of the relay of control of resistance of the neutral wire, an ohmmeter is switched on via an adjustable resistor.

The drawing shows the proposed device.

The device contains an operating current transformer 1, a measuring current transformer 2, a rectifier 3 relays monitoring the resistance of the neutral wire and an ohmmeter, a rectifier 4 relays for fixing blind circuits, a rectifier 5 for the intermediate relay, a relay 6 for monitoring the resistance of the neutral wire, a relay 7 for fixing blind circuits, intermediate relay 8, discharge resistor 9, adjustable resistors 10-13, network switch 14, toggle switches 15-17, signal lamp 18, additional winding with terminals 19-20 of transformer 1; capacitors 21-23, ohmmeter 24, actuator (linear contactor) 25, button “Start 26, button“ Stop 27, contacts 28-30, respectively, relay 8, 6, 7, contact 31, relay 8, first secondary winding with terminals 32- 33 transformer 1, the second secondary winding with leads 34-35, transformer 1, the primary winding with leads 36-37 of transformer 2, the secondary winding with leads 38-39 of transformer 2.

The device works as follows.

The source of operational alternating current is transformer 1, included in the neutral conductor. When the voltage is set, the current in the neutral wire depends on its impedance. A change in grounding resistance changes the voltage of the secondary winding of the transformer 2,

which after rectifier 3 goes to relay 6. When the resistance of the monitored circuit increases by 1 ohm or when the circuit is broken, the current in the coil circuit of the control of the neutral conductor 6 controls the decrease or loss of current causes the relay 8 to turn off, open its contacts and turn off the contactor 25. If the increase Resistance will occur before the installation is put into operation, the device will not turn on, the light bulb 18 will not light up, since the voltage

the rectifier will not sufficiently charge capacitor 21 for relay 6. To start the 6 volt relay. the operation of the toggle switch 15 is set to the "open" position, the contacts of the toggle switch are open, the load is removed from the rectifier 3, the voltage on the capacitor 2 reaches the maximum value giving the starting charge. When the contacts of the toggle switch 15 are set to the upper position, the operation closes its contacts, the relay 6 is put into operation, and the voltage of the rectifier drops to the minimum value for keeping the relay in working condition. The operation setting of relay 6 with the maximum allowable increase in the resistance of the monitored circuit is achieved by a resistor 10. Expansion of the limits of operation of the device with large resistances of the controlled circuit, for example 30 ohms or more, is achieved by increasing the alternating voltage at the input of the rectifier 3 from the terminal winding 19-20 transformer I connected in series to the secondary winding of transformer 2, the magnitude of the additional voltage is set depending on the resistance of the controlled circuit using taps from this winding (or potentiometer). Setting the toggle switch 15 to the “open” position

0 on the opening of its contacts, and it identifies the breaking of the ground circuit, the electrical installation is turned off. Reliable start of relay 6 is achieved by the combined action of the discharge current of the capacitor 21 and the shunting of part of the resistor 10, and the reliability of the disconnection

5 with the minimum holding current of the relay 6 due to the discharged capacitor 21 and the additionally included part of the resistor 10. With a dangerous voltage in the neutral wire circuit, the series-connected terminals 32-33, 36-37 windings of transformers 1 and 2 produce a voltage greater than that generated by transformer 1 This voltage through the resistor 12, the rectifier 4 enters the winding of the relay 7, while the relay 7 opens its contacts 30 in the circuit of the rectifier 5 of the relay 8, resulting in the opening of the contacts 28 of the relay 8 in the circuit of the organ 25 (linear contactor). The electrical installation is disconnected from the network, the device is brought to its initial state of readiness for operation. The threshold for triggered voltages is set by adjustable resistor 12. Relay 7 power supply directly from transformer I ensures independence of relay 6 and 7 adjustments. Relay 7 operability is short to rectifier 4 and the full voltage of the winding is applied to the rectifier 16 pins 32-33, relay 7 turns off relay 8, contactor 25 is kept off until the toggle switch 16 is in the “work. In the “work” position, the contacts of the toggle switch 16 are opened, and the current to the winding of the relay 7 goes through a resistor 12. The independence of the device operation mode from network oscillations is achieved by the simultaneous operation of capacitors 22, 23 together with the primary winding of transformer 1. Capacitor 22 causes ferroresonance, and capacitor 23 filters harmonic oscillations associated with non-linearity of the operating mode of the transformer core 1. By selecting the value, the sinusoidal current of the secondary windings of the transformer 1 ,, is restored, the load decreases ny current its primary winding. Switch 14 sets the mode of power supply of transformer 2 by the current of the first secondary winding of transformer 1 in position "C - phase, in position" PF - antiphase to the current of the neutral wire or in the position "O - zero, only the current of the neutral wire. The "C - network" position is operational when the phase imbalance and the neutral wire current is insignificant. The “PF” position is used when a large distortion of the wire is close to critical. In this position, the current of the neutral wire and its voltage on the electrical installation case are partially compensated by the current and voltage of the first secondary winding of the transformer 1, which expands the ability of the device to operate. When the phase imbalance is on the verge of a critical and corresponding to this current value and voltage of the neutral wire, when in the "PF device gives a trip, in necessary cases it is switched to the position" O in which the network is disconnected, and the first secondary winding of the transformer 1 and secondary the winding of the transformer 2 is powered only by the current of the neutral wire. If in this case the voltage of the neutral wire exceeds

critical, relay 7 will turn off the electrical installation and will not allow it to be turned on until the voltage on the neutral wire is normalized. The capacitor 23 in, the zero position of the filtering harmonic turns into a load primary winding transformers, which, reducing the reactance 32-33 windings, conclusions, increases in the winding of the transformer 2, the current required for operation of the devices. When the toggle switch 17 is set to the "Ohms" position, the rectifier 3 is connected via resistor 11 by an ohmmeter shunted by a low-resistance resistor 11. Due to the low impedance of the ohmmeter circuit, the latter becomes the main load, the rectifier voltage 5 mitel drops sharply, the relay 6 switches off the electrical installation if it was turned on, There is only one ohmmeter in operation.

Resistor 11 sets the smoothness of the ohmmeter arrow deflection and protects

from overload currents. The peculiarity of the ohmmeter adjustment is the adjustment of the ohmmeter pointer by the resistor 11 not to the zero position, as is customary, but to the indication of the limiting resistance value

5 of the monitored circuit, which achieves an increasing accuracy of the indication of the ohmmeter as it approaches the critical value of the resistance of the measured circuit. In order to eliminate the influence of the current of the neutral wire on the measurement result, the measurement is performed in two positions of the switch 14 (in the position "C" and "PF), the average value of the measurement results is equal to the value of the measured resistance. When the switch 14 is set to the zero position, the ohm meter simultaneously serves as an indicator of the current value of the neutral wire. The magnitude of the deviation of the arrow from the zero position indicates the relative magnitude of the current and voltage of the neutral wire, the greater the current of the neutral wire, and therefore

0 and the voltage across it, the greater the deviation of the arrow.

This device provides instant disconnection of electrical installations from the network in cases of breakage of the neutral conductor, grounding, increase of the circuit resistance.

5 earths and a neutral conductor just 1 Ohm from the set nominal, single-phase deaf and incomplete closure, when a dangerous voltage appears on the case of the installation, when a zero wire that supplies single-phase loads to the case;

provides automatic protection of the power circuits of the device against short circuits by switching to "standby mode and automatic restoration of the operating mode after the removal of a short circuit; ensures the independence of the device operation from network voltage fluctuations within wide limits;

carries out end-to-end monitoring of the grounding circuit and the neutral conductor at the current source-electrical installation section with their total resistance ranging from 3 to 30 ohms or more, allows switching on the electrical installation only in the absence of a single-phase short circuit and in good condition of the grounding circuit and the neutral conductor, according to their total resistance set by the regulation;

gives the choice of the mode of power supply of the controlled circuit with the operating current depending on the dynamic state of the network: phase, antiphase current of the neutral wire or only the current of the neutral wire;

the operational control of the resistance of the grounding circuit and the neutral conductor ensures the possibility of timely normalization, guaranteed reliability of the protective action of this circuit;

The versatility of the device gives a great economic effect when used in areas with large specific earth resistances, where obtaining normal resistances of grounding devices is impossible or requires the construction of complex, expensive artificial earthings provided for by the Electrical Installation Rules. Under normal conditions, the economic effect is achieved by the possibility of increasing the resistance of grounding devices, wider use of natural grounding, reducing the cross-section of the neutral wire, since the disconnection of single-phase short circuits is guaranteed, even at currents many times smaller than the worker.

Claims (3)

1. Device for protective disconnection of an electrical installation in a three-phase AC network with a neutral wire, containing an operational current transformer, the primary winding of which is connected to the network through a switch, the first secondary winding is connected to the neutral wire and connected in series with the primary winding of the current transformer, the secondary the winding of which is connected through a rectifier to the winding of a relay controlling the resistance of the neutral wire, and the second secondary winding of the transformer of operational t The eye is connected to an alarm element, a dead-lock relay and an actuator, characterized in that, in order to increase reliability operation, a dead-circuit latching relay winding through the newly introduced first additional rectifier and adjustable resistor is connected to the series-connected secondary winding of the operating current transformer and the primary winding of the measuring current transformer, the secondary winding of which is connected in series with the newly introduced additional secondary winding of the operating transformer current, to which is connected the world connected to the winding of the control relay of the neutral wire, locked by a newly introduced charging capacitor, and parallel to the aforementioned second secondary winding of the operating current transformer through connected in series closing contacts of the control relay of the neutral conductor and disconnecting contacts of the control monitoring the resistance of the neutral conductor and disconnecting contacts of the de-closure latching relay, a second additional rectifier and an intermediate relay winding are inserted, the closing contacts of which are included in the power supply circuit of the executive body, and the primary winding of the operational current transformer, clamped by the first additional capacitor, ithout second additional capacitor and a resistor connected to said switch. 2. The device according to claim 1, characterized in that the switch is additionally provided with anti-phase connection contacts and zero connection contacts. 3. The device according to claim 1, characterized in that an ohmmeter is connected in parallel with the winding of the control relay of the neutral wire through an adjustable resistor. Sources of information taken into account in the examination I. Motusko F. Ya. Protective devices in electrical installations. M., 1973, p. 185-187. 2. USSR author's certificate No. 587554, cl. H 02 H 3/16, 1975. // Ult / 7 s l one 7 v7 I „j /