SU668036A1 - Device for protective cutout of electric installation in ac mains - Google Patents

Description

I

This invention relates to a technique for protecting people from electric shock.

Devices are known for the protective disconnection of an electrical installation based on the formation of a tripping signal based on the change in leakage current to earth in absolute terms.

The closest technical solution to this invention is a device in which a detuning of protection from natural leakage currents to earth (through insulation) 2 is provided.

The known device comprises a zero-sequence current transformer, a signal generating unit with respect to the derivative of the leakage current, a threshold element of the absolute value of the leakage current, and a load current transformer.

However, current leaks on the ground can generate current pulses of various amplitudes, steepness and duration, associated with various transients, as well as very short-lived, life-threatening human touches and small rodents. Disconnections for these reasons can significantly reduce the reliability of power supply.

The purpose of the invention is to improve the reliability of power supply.

This is achieved by reducing the number of interruptions in the power supply by adjusting the protective disconnect devices from the leakage current pulses that are not life-threatening.

The goal is achieved by the fact that a device containing a zero-sequence current transformer, the output of which is connected to the inputs of a signal generating unit based on the derivative of the leakage current and the threshold element of the absolute value of the leakage current, load current transformer, to the input of which the input of the prohibition signal generating unit is connected the derivative of the load current, the output of which is connected to the prohibitive input of the signal-shaping unit based on the derivative of the leakage current, the output relay element into it

Claims (2)

A leakage current integration unit is introduced over time, the input of which is connected to the output of a zero-sequence current transformer, the first triggering input of the specified block is connected to the output of the signal shaping unit by the derivative of the leakage current, and the second triggering input with the output of the threshold element of the absolute value of the leakage current, and the output of the block integrating the leakage current over a timeconnected to the output relay element. The drawing shows a block diagram of the proposed device. The device contains a zero-sequence current transformer 1, a load current transformer 2, a signal-generating unit 3 based on the derivative of the leakage current on earth, a signal-generating inhibit signal-generating unit 4 based on the derivative of the load current, a leakage current integrating unit 5 in time, a threshold element 6 of the absolute value of the leakage current To Zymlyu, triggered when the leakage current exceeds the absolute value of more permissible, the output relay element 7, acting on the control unit 8 of the switching device. The principle of operation of the device is as follows. In the event of an earth leakage current surge, unit 3 issues a signal for the start of the integrating unit 5. The magnitude of the pickup setting Uj ,, is chosen from the condition acceptable for a person, without harmful consequences, of pulsed power. Depending on how the transient process changes the leakage current, unit 5 generates a tripping signal or is reset to zero, before it has enough energy to operate the device. In case of occurrence of large slowly varying current leaks, exceeding the permissible values in absolute value. block 6 generates a signal that triggers block 5, which generates a tripping signal when the setpoint value is exceeded. Thus, the proposed device favorably differs from the known ones due to the fact that the number of unjustified power cuts in the network is reduced and thereby the reliability of the power supply is increased. Claims. A device for protective disconnection of an electrical installation in an AC network containing a zero-sequence current transformer, on whose output the inputs of the signal generating unit are derived from the derivative of the leakage current and a threshold element of the absolute value of the leakage current, load current transformer, to the output of which the prohibition signal generation unit is connected on the derivative of the load current, the output of which is connected to the prohibiting input of the signal generating unit based on the derivative of the leakage current, the output relay element, characterized in that, in order to improve the reliability of power supply, a leakage current integration unit is introduced into it over time, the input of which is connected to the output of the zero-sequence current transformer, the first triggering input of the specified block connected to the output of the signal shaping unit according to the leakage current leakage current, and the second triggering input is with a threshold element output of the absolute value of the leakage current, and the output of the leakage current integration unit is connected to the output relay element by time. Sources of information taken into account during the examination 1. USSR Author's Certificate No. 476333, cl. H 02 H 5/12, 1975. 2. USSR author's certificate N ° 465690, cl. H 02 H 3/14, 1973.  R CP / 77 I IT