SU995186A1 - Device for single-phase earthing protection in network with insulated neutral - Google Patents

Description

(54) DEVICE FOR PROTECTION AGAINST SINGLE-PHASE LOCKS ON EARTH IN A NETWORK WITH ISOLATED

one

The invention relates to electrical engineering, in particular to devices for protection against single-phase earth faults in a network with a low earth fault current.

A device for protection against earth fault, containing zero sequence current transformers installed at each connection, the secondary windings of which through current converters are known, is known. the rectified voltage is connected to the reacting elements, the start body connected to the zero-sequence voltage transformer (TNNP), the executive bodies connected through the elements: you match the outputs of the reacting elements and the outputs of the start body 1.

A disadvantage of the known device is the inadequate actuation of the inrush of its own capacitive currents, which can be commensurate in magnitude with the total ground fault current. Detuning from these currents is associated with a deeper protection, t; e. with a decrease in its sensitivity, and can lead to failures in response.

NEUTRAL The closest to the proposed technical entity is a ground fault protection device, containing according to the number of TTPN connections, current transducer - rectified voltage, storage cells, integrating - elements, comparators, memory actuators, disconnecting coils , according to the number of connections, the opening keys controlled from the starting start-up

JQ of the voltage control unit J2.

However, this device is characterized by the possibility of false operation and low sensitivity.

The purpose of the invention is to increase the selectivity and speed of the device.

The goal is achieved by the fact that a device containing sequentially connected TTPD converter installed on each connection current to the reacting element connected to the output of the actuator with a memory, the output of which is connected to the disconnection switch disconnecting coil, start body , connected by its input to the zero-sequence voltage transformer (TNNP), and by its output to the first input of the control unit, which is the input of the element HE, the output to the second input of which is connected to the output of the element LIMITED MEMORY, whose input is the E input of the control unit, the output of the element OR control unit, which is its first output, is connected to the control input of the closing key connected parallel to the output of the corresponding converter, the current is a rectified voltage, equipped with a common for all connections with a correction unit, made on the elements HE, AND, and OR according to the number of connections, and common to all connections an adder of response signals of reacting elements with a threshold element at the output and locking keys at the inputs, the control inputs of which are connected to the outputs of the actuators, and the output of the threshold element is connected to the second input of the control unit and one of the inputs of the AND elements, the second inputs of which are through the elements connected to the outputs of the corresponding reacting elements, the outputs of the elements AND through the elements OR are connected to the control inputs of the executive bodies, the second inputs of the elements OR are connected to the second in swing control unit, representing the output of a NOT element.

The drawing shows a diagram of the device for protection against single-phase ground fault.

The device contains TTPDs 3 and 4 installed at connections 1 and 2, the secondary windings of which through converters 5 and 6 current - rectified voltage and repeaters 7 and 8 of the signals are connected to reacting elements 9 and 10, a triggering organ II connected by its input to TNNP 12, the executive bodies 13 and 14, the inputs of which through the elements 15 and 16 are connected to the reacting elements 9 and 10 and the output of the starting body 11, and the outputs to the coils 17 and 18 of the circuit breakers (not shown) of the connections 1 and 2, closing keys 19 and 20 with consecutive p by the sistors 21 and 22, key control unit 23 and keys 19 and 20, the outputs of which are connected to the control inputs of these keys, and inputs to the output of the trigger 11 and one of the inputs of the correction unit 24 connected by their other inputs to the outputs of the response elements 9 and 10, the executive bodies 13 and 14 and to one of the outputs of the block 24 correction.

Transducers 5 and 6 contain transformers, rectifiers, and memory capacitors. They can also be made on operational amplifiers. As repeaters 7 and 8 signals. Can be used emitter repeaters with high input resistance and low output.

The control unit 23 consists of the elements NOT 25, LIMITED MEMORY 26 and OR 27, the output of the latter connected to the control inputs of keys 19 and 20, and the inputs through the elements NOT 25 and LIMITED MEMORY 26 connected to the output of the trigger 11 and to one of the outputs block 24 correction.

Block 24 correction performed on the elements NOT 28 and 29, and 30 and 31 and OR 32

and 33, as well as on the adder 34 of the response signals of the reacting elements, the inputs of which through the input resistors 35 and 36 and the closing switches 37 and 38 are connected to the source of standard signals Uc, and the output through the threshold element 39 is connected to one of the inputs of the elements 30 and 31 , the second inputs of which are connected through HE elements 28 and 29 to the outputs of reacting elements 9 and 10, and the outputs through the first inputs of elements OR 32 and 33 are connected to control inputs of executive bodies 13 and 14, the second inputs of which are connected to the output of element NO 25 block 23 control and.

The threshold element 39 is triggered when

condition on the occurrence of the adders 34

signals of two or more signals, i.e. when

two or more react

an item.

The device works as follows.

In the absence of a single-phase interlock in the network, the reacting elements 9 and 10, the launching body 11, the executive bodies 13 and 14 and the threshold element 39 are in the initial state, while the reacting elements 9 and 10 have the minimum settings of operation ( are in maximum sensitivity mode).

Keys 19 and 20 are closed, and keys 37 and 38 are open.

When a single-phase ground fault occurs in the network, for example at junction 1, the total ground fault current flows through it, the value of

which is usually greatest. Through intact connection flows its own capacitive current. At the output of the TNN 12, a zero-sequence voltage appears, under the action of which

the starting element 11. The keys 19 and 20 open, and the capacitors of the converters 5 and 6 begin to charge from voltages proportional to the zero-sequence currents of connections 1 and 2.

If the summing current of the ground fault is greater than the response setpoint of the reacting element 9, then it is triggered, and if the reacting element 10 does not operate, the signal appears at the input of the actuator 13, and the latter triggers and causes the connection switch 1 to open.

If the value of the intrinsic capacitance jHpro of the intact attachment 2 is sufficient for the response of the reacting element 10, then it, like the reacting element 9, is activated and a linear law changes through the disconnecting coils 18. At the same time, a signal appears at the output of the threshold element 39, under the action of which the keys 19 and 20 are closed and the voltage at the outputs. The capacitors of the converters 5 and 6 begin to decrease approximately linearly and at the same speed, because the time constant of the discharge of the capacitors of the converters 5 and 6 at all connections are identical. The highest value of this constant should be less than the tripping time of the connection switches. When the voltage reaches a certain value (return voltage), the reacting elements 9 and 10 begin to return to their original state. The reacting element 10 is the first to return to this state, since the value of the own capacitive current of connection 2 is less than the total earth fault current. The signal at the output of the reacting element 10 disappears. As a result, a signal appears at the output of the element OR 33, and the memory of the element 14 is cleared, the coil 18 is de-energized, and the threshold element 39 returns to its initial state. After a short delay, depending on the rate of rise of current in the disconnecting coil 17 and bringing the actuator of connection switch 1 to a working state, this switch disconnects the damaged connection from the mains supply source.

After that, the reacting element 9, the launching body 11, the executive body 13, the element

LIMITED MEMORY 26 and is broken Ie key 37 and the closure of keys 19 and 20. The scheme is ready for re-action.

Similarly, the device operates in single-phase circuit on the connection 2.

Typical elements, such as microcircuits, thyristor, transistors, reed switches, etc., can be used to manufacture the device.

An introduction to the device for simple current protection of a correction unit performed on the accumulator of response signals of reacting elements, NOT, AND, and OR elements, the total number of which is equal to the number of protected connections, of keys with a control unit allows to create a more perfect protection of a single-phase earth fault satisfying at the same time, they require selectivity, sensitivity, speed and do not require an individual choice of settings.

The proposed solution can be used not only to create new devices for protection against single-phase earth fault, but also to improve existing devices, which creates an economic effect due to increased reliability of power supply to consumers, improved electrical safety and reduced costs

on setting up and setting up protection.

Claims (1)

Invention Formula 5 Device for protection against single-phase earth faults in the network with insulated neutral, containing sequentially connected zero-sequence current transformers installed at each connection, current transformer - 0 rectified voltage and reacting element connected to the output of the actuator with memory, the output of which is connected to the disconnecting coil of the connection switch, the starting body connected to the transformer of the zero-sequence voltage with its input and the output to the first input of the unit control, representing the input element NOT, the output of which is connected to the first input of the element OR, the second input of which is connected to the output of the element OG RANICAL MEMORY, the input of which is the second input the control unit, the output of the OR control unit, which is its first output, is connected to the control input of the closing key connected in parallel with the output of the corresponding converter — the rectified voltage, characterized in that, in order to increase speed and selectivity, it is equipped common for all connections by the correction unit performed on the elements NOT, AND and OR according to the number of connections and common for all connections by the adder of the response signals of the reacting elements with the threshold element on output and locking keys on the inputs, the control inputs of which are connected to the outputs of the actuators, and the output of the threshold element is connected to the second input of the control unit and one of the inputs of the And elements, the second inputs of which are NOT connected to the outputs of the corresponding reacting elements, the outputs of the elements And through the OR elements are connected to the - control inputs of the executive bodies, the second inputs of the OR elements are connected to the second output of the control unit, which is the output of the HE element. Sources of information taken into account in the examination 1. Journal “Industrial Energy, 1968, № 3, p. 4-7. 2 USSR Author's Certificate in Application No. 2893998 / 24-07, cl. H 02 H 3/16, 1980, 2nd version.