CN85201172U - Field discharge device of generator - Google Patents

Abstract

The utility model discloses a quick de excitation protection device for a large-sized synchronous generator. The protection device is an important method for ensuring the safe operation of a large-sized simultaneous generator set. The utility model adopts a zinc-oxide nonlinear resistor as a power absorbing element. The protection device of the utility model adopts the method that a mechanical switch and the direct current breaking technique of manual zero cross are matched. An excitation source can be reliably cut off and an exciting current can be covered into the zinc-oxide nonlinear resistor. An ideal effect of demagnetization is obtained. The accompanying diagram is the electric schematic diagram of the device.

Description

The artificial zero-based field suppression equipment of a kind of generator

The utility model belongs to the electric machines control technology field.

The quick de-excitation protective device of large synchronous generator is the necessary means that guarantees the large synchronous generator safe operation.In modern age large synchronous generator rotor loop,, and generally adopted the thyristor excitation power supply, caused the problem of generator quick de-excitation protection to become increasingly conspicuous because its rotor energy storage and time constant constantly increase with single-machine capacity.What external general at present field suppression protection device adopted is the way that quick mechanical switch matches with silicon carbide nonlinear resistor.Typical Route as shown in Figure 1, power-absorbing wherein is a silicon carbide nonlinear resistor, because its non-linear voltage-current characteristic is nothing like the znr ideal, so dynamic characteristic in the demagnetization process and desirable demagnetization curve apart from each other.If the generator single-machine capacity further improves the quick mechanical switch of its direct current also can run into very big difficulty on making in addition.In the present method that is still automatic field suppressing that generally adopts of China as shown in Figure 2.A large amount of operating experiences prove that this type de-excitation system accident is frequent, mainly are that suicide contactor burns, so that cause that overvoltage punctures, and causes heavy economic losses.

The utility model is improved the artificial zero-based field suppression equipment of the generator of having developed two types to existing demagnetizing technology.

First kind: the artificial zero-based of vacuum switch, as shown in Figure 3.It is main flow passage switch with three-phase alternating current vacuum switch (3); open vacuum switch during quick de-excitation protection action earlier; triggering discharge controller (4) (can also can be with controllable silicon or the like with triggering the gap) then will give the converting capacitor (5) that is filled with electric charge and discharge to vacuum switch; force the electric current that wherein flows through to support zero and cut-off with certain electric current fall off rate; thereby thyristor excitation power supply (2) and rotor winding (1) are disconnected the change of current of finishing to znr (8), and make rotor current in znr, reduce to zero with speed sorrow near desirable demagnetization.The vacuum switch direct current cut-offs technology is used widely in the controlled nuclear fusion engineering, and the cooperation of each component parameters is no longer described in detail here with selection.

Second kind: the artificial zero-based of the controllable silicon secondary change of current.See with respect to the mode of connection of rotor-exciting winding and can be divided into two kinds of parallel connection type and tandem types that from reverse-blocking tetrode thyristor its elementary diagram as shown in Figure 4 and Figure 5.Wherein Fig. 4 is the artificial zero-based of the controllable silicon series connection secondary change of current, and Fig. 5 is the artificial zero-based of the controllable silicon secondary change of current in parallel.The course of action of two types field suppression equipment is as follows: normal operating exciting current flows to excitation winding by mechanical switch (3); the field suppression protection action time at first disconnects mechanical switch (3), and the exciting current IL by mechanical switch (3) changes reverse-blocking tetrode thyristor (4) automatically over to and forms afterflow.Then auxiliary controllable silicon (6) is triggered and conducting, reverse voltage on the converting capacitor (5) is prominent to impose on (4), force and flow through the current over-zero in (4) and turn-off, exciting current IL continues reverse charging to electric capacity (5), (8) conducting when voltage reaches the conducting voltage of znr (8), IL changes (8) over to and finishes the change of current for the second time.The rapid sorrow of IL subtracts under the back-emf that provides in (8).Obviously, it seems that equivalently reverse-blocking tetrode thyristor (4) only plays a kind of state type arcing contact, the through-flow time is of short duration, is about 40～60ms, thus need not to add any cooling provision, and can transship.Mechanical switch has then been avoided the direct cutout to strong inductive load, so the energy that mechanical switch absorbs in the interrupting process seldom, and the result of experiment measuring shows: the energy-absorbing of each open mechanical switch only is about 1% of the total energy storage of rotor.So just improved the useful life of mechanical switch greatly, can consider to be designed to the device of frequent operation,, improved the reliability of whole excitation system so that simplify the thyristor excitation power supply.The charge power supply of giving of change of current electric capacity (5) is provided after by transformer (13) and diode (15) halfwave rectifier by generator self-excitation anode voltage.(6) and the triggering power supply of (4) disconnect the back at mechanical switch (3) and provide by energized circuit self, and need not any accessory power supply and light current electronics element, thereby system has very high antijamming capability.The triggering signal that silicon controlled main rectifier (4) turn-offs is sent by the auxiliary normally closed contact point of main frame tool switch (3), through 30ms time-delay back (with the complete blow-out of assurance main switch, IL all changes (4) over to) start a pair of normally closed of a high-voltage relay, (6) can be triggered in normal opened contact (9), (10) turn-offs (4).In addition in order to prevent that (6) and (4) trigger electrode from bearing back-pressure and and each is gone here and there a 3000V, the little silicon stack (11) of 0.2A, (12) being arranged in the trigger electrode loop.

(see figure 5) should be considered to make it set up sufficiently high arc voltage when mechanical switch designs for parallel connection type controllable silicon secondary change of current scheme.So both made when (4) contingency occurs refusing conducting, and promptly also can independently interdict exciting current IL under the situation of a commutation failure and guarantee that field suppression protection moves successfully.If turn-off failure so that secondary change of current inefficacy exciting current IL can pass through silicon controlled main rectifier (4) just in case reverse-blocking tetrode thyristor takes place, change the afterflow demagnetization automatically over to, and can not produce any serious consequence, so protection is a multiplicity, thereby also can be reliable.

The utility model compared with prior art; because znr has the volt-ampere characteristic more even more ideal than silicon carbide nonlinear resistor; the demagnetizing time that can make generator is very near desirable demagnetizing time; simultaneously reduced requirement to mechanical switch owing to used reverse-blocking tetrode thyristor and mechanical switch way of combining to cut-off direct current; improve the life-span of mechanical switch and the reliability of device action, thereby can satisfy the requirement of modern large synchronous generator quick de-excitation protection.

This selection of installing each component parameters needs to decide according to the concrete parameter of generating set.Be the parameter that example provides each element of one group of controllable silicon secondary change of current in parallel type field suppression equipment with homemade SF125 type hydraulic generator unit below.The maximum rotor magnetic storage energy that can try to achieve SF125 type hydraulic generator unit by the generator amature demagnetization energy software for calculation of our establishment is 1.5 megajoules.With the monolithic that I produced can hold be your znr element of 30 kilojoules after the znr demagnetization optimum organization program of our establishment is preferred, can obtain 3 strings 30 and totally 90 elements combination.The conducting voltage of each branch road nonlinear resistance can be taken at 1800V, and ceiling voltage is limited in 2000V with the interior requirement of satisfying the de-excitation system insulation level.For the forward leakage current that reduces in the nonlinear resistance can seal in one group three diode connected in parallel (7), every parameter is: 2000V, 800A.Mechanical switch (3) is selected the 2000V of special development for use, the 2000A dc switch.(4), (6) be 4500V, the 1500A high-power silicon controlled rectifier.(5) get 500 μ F, 5000V pulse capacitor group is given charging voltage 2000V.(5) the former limit of charging transformer (13) is 760V, and paying the limit is 1430V, capacity 500VA, withstand voltage level: exchange 5000V, 1 minute.Current-limiting resistance (14) is 10k Ω.Rectification silicon stack (15) is back-pressure 5000V, electric current 0.2A, and (16) get 50 μ H for current limiting reactor.(4) trigger electrode resistance (17) is got 10 Ω, and the trigger electrode resistance (18) of (6) is got 5K Ω.All need reach between the contact of high-voltage relay and to insulation and exchange 5000V.

Fig. 6, Fig. 7, Fig. 8 are the dynamic analog test oscillogram of this device under the 1:1 condition of laboratory.Wherein Fig. 6 is that the rotor current maximum is 1640A, vertical axis 416.67A/ lattice, trunnion axis 92.5ms/ lattice.Fig. 7 is a rotor winding both end voltage, maximum 2000V, vertical axis 384.6V/ lattice, trunnion axis 92.5ms/ lattice.Fig. 8 is the electric current in the znr, maximum 1567A, vertical axis 277.8A/ lattice, trunnion axis 92.5ms/ lattice.Znr energy-absorbing 946KJ, mechanical switch energy-absorbing 28KJ.By oscillogram as can be seen: the voltage waveform rising front is level and smooth and (being several microseconds) rapidly, has eliminated mechanical switch and has built arc voltage jitter phenomenon in the pressure.Flat part voltage descends less, no overvoltage spike.Current waveform is triangular in shape in the znr, very near desirable demagnetization curve, can satisfy the requirement of large synchronous generator group quick de-excitation protection.

Claims (5)

1, generator quick de-excitation device is the protective device of large synchronous generator internal fault, and traditional technology has mechanical switch to match with silicon carbide nonlinear resistor and two kinds of suicide contactors.The utility model is the artificial zero-based field suppression equipment of a kind of generator, it is characterized in that being formed with znr (8) and the artificial zero-based switch of controllable silicon, the artificial zero-based switch of controllable silicon is mainly by a mechanical switch (3), silicon controlled main rectifier (4), auxiliary controllable silicon (6) and converting capacitor (5) are formed by connecting.

2, the artificial zero-based field suppression equipment of generator according to claim 1 is characterized in that this znr (8) and generator amature winding are to be connected in parallel.

3, the artificial zero passage field suppression equipment of generator according to claim 1 is characterized in that artificial zero-based switch of controllable silicon and generator amature winding are to be connected in parallel.

4, the artificial zero-based field suppression equipment of generator according to claim 1 is characterized in that artificial zero-based switch of controllable silicon and generator amature winding are to be connected in series.

5, artificial zero-based field suppression equipment according to claim 1 is characterized in that comprising a vacuum machine switch that is connected with the rotor windings in series.

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