SU982136A1 - Method of redundancy protection of transformer - Google Patents

Description

(54) METHOD FOR RESERVE PROTECTION OF THE TRANSFORMER

one

The invention relates to electrical engineering, in particular, to the provision of long-distance reserving by protection of transit electric power lines of transformers of the back-up substations connected to them.

Methods are known for long-range backup, which are based on the name of line relay devices that react to negative sequence components til, Q

Since the two-phase asymmetrical short-circuits in the complex distribution device of the secondary step-down substation most often turn into three-phase symmetric short-circuits (ka), to which the indicated filter protections do not react, in order to provide long-distance protection of the short-circuit transformers jq, the creation of an artificial current imbalance switching on the variable transducer in one of the phases of the power supply of the transformer. From current short circuit transformer

in the additional inductor, the winding is disconnected, which changes its resistance, causing current to be unbalanced in the line and its protection C2 to react.

This method of remote fovashsh reserve requires the inclusion of a special additional route with the scheme of its lagging, and it provides reagent protection of the line protection at the short-circuit. for transformers of low power.

The purpose of 1Ebotey is to increase the sense of protection of any type of k. A. behind the transformer by creating an artificial asymmetry.

Claims (2)

The goal is achieved by the fact that according to the backup protection method of the transformer of the backup substation 4-11, the protection of the power supply of the power supply unit for measurement transmission; the asymmetry of the magnitude of the line currents and its comparison with the setpoint, which exceeds the magnitude of the linear balance of the symmetric mode of the line, and & In the case of measured current, above the line setpoint for setting the signal to disconnect the line with a higher time than the set time of the transformer protections in the emergency substation, the short-circuit current is measured. three phases, one of the transformer phases is magnetically rectified by the sum of these currents and the current unbalance is measured by comparing the extracted third harmonic current of this phase with the third harmonic current of any other phase of the supply line. The current of each phase of the transformer is rectified and summed up for additional ampere turns of one of the phases of the protected transformer. Then, in the normal mode of loading the transformer, it cannot then cause the magnetic conductor to saturate, since this is an insignificant addition to the existing magnetizing current. When k.z. at any phase due to the significant frequency ratio of the Q. 3 current, in relation to the nominal mode, the additionally magnetised magnetic circuit is saturated. The spreading of the additional magnetic flux through the other two rods cannot cause the same significant saturation in them; therefore, a significant difference arises in the shape of the currents with the corresponding component of the third harmonic current. Transformers at nominal voltage; The work is performed with the maximum possible induction in the region of the saturating part of the no-load characteristic of the transformer. A slight increase in the magnetic flux Causes a sharp increase in the current of the idle current and the higher harmonics in it. If the increase in losses in steel jfi this occurs in proportion to the square of the voltage, the increase in the magnetizing current and the components of the higher harmonics in it increase due to the saturation of the magnetization of the steel to an even greater degree. When k.z. for a low power transformer, the mains voltage and induction are not substantially reduced. To detect the difference of the third harmonic currents on the power transmission line, including a setpoint adjusted from the normal load mode and a slight overload, the null indicator on the third harmonic current difference from the filters and transformers of the magnetizing phase and the other phase of the line current. The inclusion of a reacting authority on the difference of the currents of the third harmonic of the two phases eliminates the possibility of false triggering of protection with a symmetrical voltage increase in the network, when all phases are equally saturated and the currents are eliminated with the appearance of the components of zero-sequence currents is zero. For stitching from the Transformer protection and transient processes in the network, the reacting body with a time delay acts to turn off the line switch. And the similar principles of protection are performed on the opposite side of the transit power line. The drawing shows a schematic diagram of an exemplary embodiment of a device for reserving transformer protection. The magnetic circuit of the transformer 1 at one of the phases has an additional bias bias winding 2, which is connected through a three-phase rectifier 3 from the transformers 4 of the current of all phases. On the supply line, a zero-indicator 5 is connected to the difference in the output of the third-harmonic filters of the indicated phase 6 and the other phase 7 from their current transformers 8 and 9. A null indicator 5 is included in the circuit breaker disconnect switch 10 lines through time relay 11. I In the normal loading mode of transformer 1, its current transformers 4 through rectifier 3 supply additional winding 2 bias current, the value of which cannot cause a significant change in the mode of appreciating the transformer 1 magnetic circuit, therefore there is no voltage at the output of the third harmonic filters tripping of the null indicator 5. With an increased voltage in the network, from which the magnetic conductor of all phases of transformer 1 is saturated, a third harmonic current into the transformer appears Orach 8 and 9 and the current at the output of filters 6 and 7, but the third harmonic zero sequence match current phases can also trigger the null indikatfa 5 included in the difference of output currents of filters 6 and 7. The short-circuit occurs Pier between any phases behind transformer 1, the corresponding current through transformer 4 of current and rectifier 3 causes in the additional winding 2 magnetic bias, which creates saturation of one of the phases to a much greater extent than the other two. This difference causes 145 flow in different phases of the line through transformers 8 and 9 of the current and the corresponding filters 6 and 7 of different magnitudes of the third harmonic currents, ensuring the operation of the null inaccuracy 5 and its operation through the relay 11 to turn off the switch 10. The time setting 11 of the relay is rebuilt from the time of action of the own protection of the tapping transformer and transient processes in the network. Similar protection is established at the 1-line terminal. When they are triggered, damage to the expensive equipment of the seal stations of the gfi is prevented in case of a failure of the own protection of transformers or their switching devices. As a result, the artificial distortion of currents in the line of gri K. On a tapping transformer, the most gfostno increases the reliability of operation, protects the substations from their complete destruction due to the failure of protective devices. Claims The backup protection method of the TGpa discharging station gsformforma by the protection of the power supply transit line by measuring the voltage of the line current and comparing it with the set value of the unbalance of the unbalance of the line and exceeding the signal for switching off the line with hold greater time delay for transformer protection at the secondary substation, characterized in that, in order to increase the sensitivity protection to any short-circuit Ivda for granformaforrm by creating artificial asymmetry, additionally measure the short-circuit currents of the three phases, magnetize the transformer with the calculated sum of these currents, and measure the current unbalance of the third harmonic with the third harmonics of any fugue phase supply line. Sources of information, one in view of your expertise 1. The author's certificate of the USSR NC 684667, cl. H 02 H 7/04, 1977. 2. To a prisoner Yu. S. Using () “ltrovye relays. -Electric sgantsiv, 1975, No. 7.