SU754547A1 - Device for protecting ac mains from earthing - Google Patents

Description

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The device relates to electrical engineering and is intended for the selective fixation of single breakdowns of insulation, arc and metal <short circuits. Phase to earth in networks with insulated and compensated neutral. This device in combination with high-speed disconnecting and shunting devices can be used to protect people from electric shock in high-voltage networks with increased risk of touching.

A device for protection against 15 damage in an AC network [1] is known, which contains sensors of compared values, a pictransformer, a logical Element And and an executive organ. The principle of operation of the device is based on determining the sign of power.

However, the specified device for selective shutdown of the damaged area, as a rule, requires additional fixation of the level of monitored values, which serves to construct it.

It is also known a device for protection [2 ^, containing threshold

elements of current and voltage, connected by inputs to current and voltage sensors, and outputs through a logical element I - to the executive body.

However, this device has no directivity, which reduces its sensitivity.

The aim of the invention is to increase the sensitivity of the device by ensuring the focus of its action.

This, according to the invention, is achieved by the fact that a known device containing the main current and voltage threshold elements, the first inputs of which are connected to current and voltage sensors, respectively, and the first 20 outputs through the main logic element I to the actuator, introduced additional current threshold elements and voltage, additional logic element 25 And and the return unit, and additional threshold elements of current and voltage with respect to the main ones are made with opposite polarities, and their inputs are connected to dates ICAM naprya30 zheniya and current, respectively, and outputs via

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additional logical element I - to the executive body, the second outputs of the main and additional current and voltage threshold elements are connected to the blocking inputs of the additional and main threshold and

current and voltage elements, respectively, the input of the return unit is connected to the voltage sensor, and the outputs to the additional inputs of all threshold elements. A pictransformer was used as a current sensor, and an active-capacitive voltage divider as a voltage sensor.

The drawing shows a functional diagram of the device.

The voltage sensor 1 is connected to 15 inputs of the main 2 and additional 3 threshold voltage elements, and the current sensor 4 is connected to the inputs of the main 5 and additional 6 threshold elements. The main 2 and 5 and additional 20 and 6 threshold elements are made raenopolar and mutually blocking each other through blocking entrances. As a voltage sensor, an active-capacitive voltage divider can be used, and a current sensor can be used as a pictransformer, to the inputs of which voltage and current zero-sequence components are fed. The outputs of the main threshold elements 2 and 5 through the main logic element And 7, as well as the outputs of the additional threshold elements 3 and 6 through the additional logic element And 8 are connected to the actuator 9. The threshold element 10 together 35 with the return element 11 are included in Composition of the return unit 12.

When a ground fault occurs in the protected zone, threshold elements 2 and 5 or 3 and 6 are triggered and, through the corresponding logical element I, give a signal to the actuator 9, which records the occurrence of damage. The selectivity of the device and the detuning from the influence of interference is provided by selecting the trigger level of the threshold elements 2, 3, 5 and 6.

When any of the threshold elements is triggered, the corresponding element of reverse polarity is blocked and the return unit 12 is started, which, after a time sufficient for the actuator 9 to operate and a clear fixation of the single insulation breakdown, removes power from the circuit 55 short circuits threshold elements, and the scheme as a whole returns to its original state. Thus, control of electrical

values corresponding to the initial moment of damage. If the initial insulation breakdown immediately goes into arc or metal boiling, the return unit 12 is blocked due to the presence of voltage sufficient to trigger the threshold element 10. In this case, the return of the circuit to its initial state is delayed until the circuit disappears.

Increasing the sensitivity of the device allows you to securely fix the damage to the protected area and quickly prevent the development of an accident.

Claims (2)

Claim 1. A device for protection of the AC network against earth fault, containing the main current and voltage threshold elements, the first inputs of which are connected to the current and voltage sensors, respectively, and the first outputs through the main logic element I to the actuator, differing from that, in order to increase the sensitivity, additional threshold elements of current and voltage, an additional logic element, and and a return unit, with additional current and voltage threshold elements with respect to the main ones made oppositely polar, and their inputs are connected to current and voltage sensors, respectively, and outputs through an additional I logic element to the actuator, the second outputs of the main and additional current and voltage threshold elements connected to the blocking inputs of the additional and main current and voltage threshold elements, respectively, the input of the return unit is connected to the voltage sensor, and the outputs to the additional the inputs of all threshold elements. 2. A device according to claim 1, characterized in that a pictransformer is used as a current sensor, and an active-capacitive voltage divider as a voltage sensor.