SU1359843A1 - Device for protecting three=phase electric mains with isolated neutral against earthing - Google Patents

Abstract

The invention relates to the field of electrical engineering and is intended to protect electrical networks from damage. The purpose of the invention is to increase the speed of the device. When the insulation resistance in the network is lowered to the set point of relay 2, it affects the opening of the switch 4 with its contacts. . 2 Il. g (L coed with 00 N4 co

Description

This invention relates to devices for protecting electrical networks against deterioration of insulation, leakage and short circuits at three-phase electric networks with insulated neutral, both under voltage and disconnected:, and can be used in mine electrical equipment, in perorgan 3, reaches the magnitude of its operation is quite fast. Or- gan 3, having triggered, outputs a signal to a high-speed drive, which simultaneously switches off the switch and turns on the short switch of the switch - short circuit switch 4. If you use the operating current only from

explosion-proof auto- Q 3 V, then when insulation deteriorates in two

matic switches

The aim of the invention is to improve the speed of the device.

In Fig. Depicts a functional diagram of the proposed device; figure 2 is a variant of the principle electric cxeNfti.

The device contains three valves 1, the first actuator on the relay 2 and the second high-speed actuator 3, which are triggered at a certain amount of leakage resistance, giving a signal to turn off the switch-short circuit

Mykatel 4, resistors 5 and 6 with adjustable- 25 cut relay 2 and. Adjustable resistor

resistive, element 7, time delay, source B, of operational voltage, direct current, diode 9.

In the static state, when the phase isolation to earth is good in a three-phase electrical network with an insulated neutral, the current through the coil of relay 2 and resistor 5 does not flow, the relay 2 and actuator 3 of the device are in the initial state.

With slow deterioration (aging) of the insulation, simultaneously in three phases, a current begins to flow, mainly from 3 V, through a parallel circuit; the relay coil 2 and the resistor 5. A part of the voltage drop across the resistor 5 is applied to the input of the high-speed actuator 3. When the current of the relay 2 reaches the response value, the last, acting, acts on the electromagnetic release switch 4 and the switch 4 5, does not reach the trigger value of the organ 3.

If instantaneous destruction of the insulation (mechanical damage or electrical breakdown) occurs in the protected mains, then the current in coil of relay 2 instantly cannot rise to the magnitude of the operation current, and the voltage supplied to the input

organ 3, reaches the magnitude of its operation fairly quickly. Or- gan 3, having triggered, outputs a signal to a high-speed drive, which simultaneously switches off the switch and turns on the short switch of the switch - short circuit switch 4. If you use the operating current only from

or one phase there appear dips in the current curve of the relay 2 and a voltage curve at the input of the organ 3, and in this device there are no dips in the current and voltage curves, since they are blocked by the source 8 of the independent operational voltage.

With gradual or instantaneous deterioration of insulation in two or one

In the phase of the protected network, the device operates as described above. In order that the internal resistance of the source 8 of the operational voltage does not limit the current to 5 when operating from 3 V, the source 8 is shunted by the diode 9.

The setting of the operation of the relay 2 and organ 3 is selected with the help of resistors 5 and 6 with adjustable resistance.

In order to prevent false alarms of the device, the input voltage to the organ 3 is fed through element 7

time delay

In the static state of the condensate.

the high-speed actuators 3 are charged from a power source (not shown) to

stabilized voltage, the value of which is below the threshold of the triggering of the dynistor 13, and the capacitor 14 is charged to the amplitude value from an autonomous source of alternating

current (not shown). The capacitor element 7 time delay discharge. The closing contact of the relay 2 is introduced into the circuit of the independent release of the switch 4, the closing contact of the relay

15 with a magnetic latch - into the circuit of the zero-voltage release switch 4, and the pulse signal of the capacitor 11 through the distor 13 is fed to the control circuit of the high-speed switch-4 drive. The device operates as described above.

When insulation deteriorates slowly in the protected network when the current in relay 2 reaches the response magnitude, it trips the independent trip circuit, disconnecting switch 4. After switching off switch 4 of the protected network, relay 2 remains in the on state, as the device goes into operation interlock leakage relay mode and does not allow the switch 4 to be turned on. After the elimination of faults that have caused the leakage of current to earth, the relay 2 returns to its initial state, the circuit breaker can be turned on.

With a sharp deterioration of the insulation in the protected network, dynistor 13 opens earlier than relay 2. The discharge pulse of the precharged capacitor 11 through the open direction 13 is fed to the control circuit of the high-speed drive (not shown) of the switch 4, which, a short circuit breaker and an independent trip unit 4, disconnects and shorts the outgoing network. At the same time, the precharged capacitor 12 ,. discharged through the working coil of the relay 15 and the open dynistor 13, it throws the relay contacts, breaking the zero voltage trip circuit, blocking the on switch 4.

I

After troubleshooting the protected network, it is necessary to unlock the relay 15. When you press the button 16

the capacitor 12, having discharged through the brake coil of the relay 15, transfers the contacts, closing the circuit of the zero voltage release. After that, you can turn on the switch 4.

Claims (1)

Invention Formula A device for protection against earth fault in a three-phase electrical network with insulated neutral, containing three valves connected in a star with terminals for connection to the protected network, a common point of stars. dy are connected to the first executive body in series with which the first resistor is connected, and also the second - the resistor connected between the common point of the star and the source of the operative voltage of direct current, the second output of which is intended to be connected to earth, a time delay element and a diode connected in parallel with the indicated source, which differs from the fact that, in order to increase the device speed, DC power supply source is connected by one output to the second output of the first resistor, and parallel to the second resistor is connected via a time delay element the newly introduced second high-speed execution unit In addition, said valves, a diode and a source of operational DC voltage are connected in the same direction. Lj 2 G Editor N.Slobod nickname Compiled by L.Vaskova Tehred M. Dtstsyk Corrector.Pojo Order 6159/53 Circulation 618 Subscription VNIIPI USSR State Committee for Inventions and Discoveries 113035, Moscow, Zh-35, Raushsk nab, 4/5 Production and printing company, Uzhgorod, st. Project, 4