SU890511A1 - Resistence relay for protecting from grounding - Google Patents

Description

(54) RESISTANCE RELAY TO PROTECT AGAINST SHORT CIRCUIT ON EARTH

I

The invention relates to remote, relay protection of three-phase power lines against short circuits to earth.

A reactance relay is known, whose operation is based on comparing the angle of the zero-sequence current Jo and the compensated voltage of the damaged phase UL From- (5 -f + xJo) Z., 1.F.

The disadvantage of it is the possibility of improper functioning when imposing oscillations on a short circuit, elimination of this disadvantage by means of interlocks from oscillations leads to complication of protection and limiting its sensitivity.

The closest to the proposed one is a relay operating on the basis of comparison of the signs of the instantaneous values of the compensated voltage of the Ulp phase and the total voltage drop in the resistance of the protected zone AUq (Zf + K3o) Zj at the time of the zero-sequence current passing through zero instantaneous 20 value 2.

The relay's disadvantage is the possibility of incorrect operation when the out-zone is closed through the contact resistance in the event that the current in phase mismatches 5 ° at the relay installation site with the current D ok in the transition resistance. The angle JS arg to / lloK is almost always due to the fact that the resistances of the systems in the zero-sequence circuit are inductive, and the resistances of the lines are active-inductive.

The purpose of the invention is to increase the reliability of the relay by improving its detuning from an external short circuit.

Claims (2)

The goal is achieved by the fact that in a known resistance relay for protection against short circuits to earth in a high voltage electrical network with a solidly grounded neutral, containing a voltage shaping unit, the inputs of which serve to connect respectively the sources of phase voltage, phase current and zero-sequence current, and the outputs are connected respectively to the inputs of the first and second limiting amplifiers, the outputs of which are connected respectively to the first and second inputs of the phase comparison unit, tively inserted block phase shift of zero sequence current, which serves for connection to said input source of zero sequence current, and an output connected through a series connected third usilitelogranichitel further inputted to the newly introduced third input of said phase comparator block. FIG. 1 shows the scheme of the proposed relay; in fig. 2 - the characteristic of the relay when closing through contact resistance. The device contains a unit for voltage regulation, OF and DOP; block 2 of the current shift JO in phase by angle fly, determined by a short circuit at the end of the line; limiting amplifiers3, forming square arc pulses with polarity determined by the polarity of the input voltage; The comparison circuit 4 of the polarity of the values at the inputs 1 and 2 at the time of the reversal of the polarity of the value at the input 3. The device works as follows when the metal ground faults in the protected zone of the phase of the values of Of and coincide and. at the moment of polarity reversal of the current Z i, the output of the element 4 causes a trigger signal. When the metal closures are outside the zone of magnitude Of and Lee, the p is out of phase and no signal appears at the output of element 4. When closing through transient, the resistance of the relay has in the plane the characteristic shown in FIG. 2 for the case of closure at the point Zi (is the value of the angle corresponding to the given closure point). With a short circuit at the end of the line, the angle difference j becomes equal to zero and the characteristic circle disappears, i.e. the device provides a clear failure during a short circuit outside the protected line, regardless of the presence of transient resistance and the ratio of zero-sequence currents. Claims of the Invention Resistance relay for protection against short circuits to earth in a high-voltage electrical network with a low-grounded neutral, containing a voltage shaping unit, the inputs of which serve to connect respectively the sources of phase voltage, phase current and zero-sequence current, and the outputs are connected to the inputs respectively the first and second limiting amplifiers, the outputs of which are connected, respectively, to the first and second inputs of the phase comparison unit, characterized in that, with the aim of increasing reliability of operation by improving the detuning of the relay from an external short circuit, a zero-sequence current phase shift block is added to the relay. Its input serves to connect a zero sequence current source to the current source, and the output is connected via a serially connected additional third limit amplifier to the newly introduced third input of the phase comparison unit. Sources of information taken into account in the examination 1. Atabekov GI. Simplified protection of the remote type from earth faults. - “Electricity, 1940, № 4. 2. Muton L., Sullar M. High-speed static resistance relays. Modern relay protection. M., “Energie, 1970.