SU1727186A1 - Device for protection of synchronous electric machine against internal damage - Google Patents

Abstract

Use: relay protection of synchronous compensators, regardless of the environment. The essence of the invention: the device contains three channels for comparing signals: a differential channel consisting of a measuring body 6 and a time delay body 8; The symmetry detection channel, consisting of a comparison and conversion organ of the signal generator 12 and a trigger delay organ 13. The current cutoff channel, consisting of the comparison block 5. The appearance of voltage at the output of any of the channels. acting on the executive 11. The executive body through an external relay circuit affects the shutdown of the synchronous machine. 2 Il. with C

Description

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The invention relates to electrical engineering and can be used to protect brushless synchronous machines (in particular, synchronous compensators, regardless of the cooling medium) from internal damage in the rotating part of the pathogens.

The known method of protection of a synchronous machine, based on a comparison of the simulated emf of the main machine with the excitation current of the auxiliary generator, and in case of violation of the established relationship between the specified values, sends a signal to the output protection element.

The disadvantages of a protection device built on this principle are the complexity of signal formation, proportional to the machine excitation current, obtained as the vector sum of the stator current and voltage of the synchronous machine, as well as the inadequate determination of the alarm condition of the excitation circuits and the slow response.

There is also a known method of protecting synchronous machines, in which a signal proportional to the current of the excitation winding and a signal proportional to the current of the core winding are compared to the circuit and the signals are compared, and in the case of difference of the signals from zero, a short circuit is detected.

It is known a protection device used about a brushless exciter of a synchronous machine, where in order to increase its reliability in the space between the main poles, an additional winding is placed in the transverse axis of the inverter generator, which is connected to one of the differential relay windings, another winding of this relay is connected to a current sensor ( voltage) excitation of the reversed generator, and the output of the differential relay through a time relay connected to the executive body, disconnecting the power in the excitation circuit.

In the experimental verification of the operation of a protection device based on this method, it was established that the coefficient of proportionality between the excitation current of the exciter, i.e. signal U0c. and the voltage at the terminals of the additional winding of the exciter, referred to as the core current sensor, i.e. signal UK. changes dramatically, causing the protection not only to trigger if there is any internal damage in the driver, but also when the synchronous machine is switched to forcing mode with excitation current

exciters in the range

 c.nome IB S2le.HOM.

A device for protection of a brushless synchronous machine is known, which contains sensors for the current of the core and exciter excitation current, connected to the inputs of the measuring unit, the time delay unit and the actuator, additionally equipped with the transformers of the current signal and the exciter current and a corrective body.

The advantage of this protection device is the use of a corrective body in it, which incrementally increases the dead zone of the measuring body in IB "IB.HOM and further.

The disadvantage of the protection device is the presence in its measuring organ of a large threshold dead band, which does not change in proportion to the change in iB.

The closest in technical essence to the present invention is a device based on this method. additionally equipped with two drivers of current and core current (voltage) excitation of the exciter, a unit comparing the absolute magnitude of the current signal of the core with a given value, an adjusting element and an OR element, the measuring element of which is made in the form of an extractor of the signal difference module and the reacting body. An adjusting element of the protection actuation level is connected to one of its inputs, the input of which is connected to the driver of the excitation current signal. The output of the module of the signal difference module is connected to another input of the reacting organ, and the signal conditioners are switched on at the outputs of the respective sensors. The descent of the absolute value comparison unit and one of the inputs of the measuring organ are connected to the output of the current signal generator cor. The other input of the measuring organ is connected to the output of the signal conditioner by the current (voltage) of the excitation of the exciter. The outputs of the absolute value comparison unit and the measuring body with the time delay body switched on at its output are connected via an OR element to the actuator, the output relay element of which is self-locking.

The advantage of this protection device is the presence in it of a high-speed channel that reacts only to asymmetrical short circuits.

A disadvantage of the known protection device is the presence of a significant threshold.

dead zone measuring body.

In the course of experimental studies of transient processes in brushless exciters and generalizing the experience of protection devices built according to the well-known principle, it has been determined that their false alarms are caused by the appearance of static or dynamic unbalances of measured signals UK and Uoc. Unbalance occurs due to differences in the time constant of the compared signals, as well as when their proportionality factor is disturbed as a result of a change in the forcing mode of the excitation winding of the main synchronous machine and the exciter generator, which depends on the temperature mode. The occurrence of unbalance of the input signals in the measuring protection body is affected by the change in the UK signal, which is the induced harmonics of the high-voltage harmonics. windings of the driver core in the circuit of the excitation poles (i.e. in the measuring coil) total emf. consisting of harmonics with a frequency that is a multiple of six in relation to the fundamental frequency — for pathogens having a three-phase bridge circuit for switching on the diodes in a rotating rectifier, or the total emf, consists of harmonics with a frequency multiple of three relative to the fundamental frequency, - for pathogens that have a three-phase zero circuit for incorporating a rotating rectifier diode oo. It is established. that the harmonic retains its percentage in the measured signal UK in the entire range of variation of the excitation current of the pole exciter (third). From its effective value linearly depends on the value of c. those. on Uoc. The false triggering of the device by the t of the switchboard is also caused by the passage of a signal-interference from the measuring coil of the current sensor of the core of the inverted generator to the measuring unit of the device, which does not have galvanic isolation on this input.

The purpose of the invention is to increase the sensitivity and enhance the functionality of the protection device.

This goal is achieved by that the protection device against internal damage of the synchronous machine, containing the exciter core current sensor, the output of which is connected to the input of the first signal generator, the first output of which is connected to the first input of the comparison unit, the second input of which is connected to the voltage source, the output of the comparison unit is connected with the first entrance

the OR element, the output of which is connected to the input of the executive body, the exciter current sensor, the second pulse shaper, the output of which is connected to the second input of the measuring body through the measuring element and the time delay organ, to the second input of the OR logic element, additionally equipped with an asymmetry detection unit, a unit for changing the cooling gas setpoint of a synchronous machine, whose input is connected to an excitation current sensor the driver and the output to the input of the second pulse generator, the first input of the asymmetry detection unit is connected to the first output of the first signal generator and the second output of this driver is connected to the second input of the unbalance detection unit, which consists of a serial connection of the comparison and conversion signal and the trigger delay organ, the output of which is the output of the unbalance detection unit, connected to the third input of the OR logic element, and the inputs of the comparison and conversion organ no signal.

Figure 1 shows the block diagram of the device; Fig.2 is a graph of measured signals and boundaries; k; insensitive device latch.

The device (Fig. 1) consists of an exciter core current sensor 1, an exciter excitation current sensor 2, a first signal generator 3, a second pulse generator 4, a comparison unit 5, a measuring unit 6, an asymmetry detection unit 7, a time delay unit 8. source 9 of the reference voltage, the logic element OR 10, the executive body 11, the body 14 changes the setting of the cooling gas of the synchronous machine. The asymmetry detection unit 7 consists of a comparison and conversion body 12 and a trigger delay body 13.

From the sensor 1 of the current core and the sensor 2 of the excitation current of the exciter, the signals U and Uoc are proportional to these values. which arrive at the corresponding drivers 3 and 4. where their conversion is realized. At the first output of the imaging unit 3, a signal is received and k. and on the VTR, the output of the same shaper is a signal. At the output, the drivers 4 receive signals U oc. The voltage source 9 provides the voltage protection device required for powering the electronic circuitry, as well as the signal U0n. AT

the measuring body 6 compares the incoming signals and U oc. The triggering of the measuring body occurs when the following relations are violated: U K U oc or U oc 2: K UK, where K is the safety factor. A time delay body 8 is used to tune out false alarms during transients. At the inputs of block 7, asymmetry is detected, i.e. The UK and UK signals are fed to the inputs of the comparator and signal transducer. The principle of the signal transform and signal transformer is based on extracting current pulses in the branches of a rotating rectifier and tracking the time between two adjacent pulses. The current pulses are extracted by comparing the signal UK (rectified voltage) with the signal UK (its average value).

In normal operation, the rotating rectifier current pulses follow with a certain periodicity. The damage in the rotating rectifier causes the disappearance of one or several current pulses, which leads to the appearance of voltage at the output of the comparison and conversion body, and further through the response delay organ 13, the asymmetry detection unit 7 is triggered. The inputs of the comparison unit 5 receive signals UK and Uon. Exceeding the UK signal over the Uon signal triggers the comparison organ 5 without time delay.

Thus, the protection device circuit has three different signal comparison channels: a differential channel (first channel) consisting of a measuring body 6 and a time delay body 8; an asymmetry detection channel (second channel) consisting of a comparison and conversion organ 12 and a response delay organ 13; current cutoff channel (third channel) consisting of unit 5 of comparison. The occurrence of voltage at the output of any of the channels triggers the operation of the logic element OR 10. acting on the actuator 11. The executive organ through an external relay affects the switching off of the synchronous machine or the excitation of the excitation or signaling.

In order to prevent the protective device from malfunctioning during signal-to-noise transmission from the sensor 1 current of the exciter core to the measuring element 6, the first driver 3 of the signal is equipped with a galvanic isolation transformer.

Between the exciter excitation current sensor 2 and the second pulse generator 4, a change setting element of the cooling gas of the synchronous machine is included. In synchronous machines, air or hydrogen can be used as the cooling gas, which imposes different requirements on the power used by the machine. For this purpose, the relay

the protection of a synchronous machine have two elements of the same type, one for each of these variants (for example, there are two current relays of the stator current overload and others that are put into operation

overlays with Air and Hydrogen positions). Usually, the transfer of a synchronous machine to another cooling gas is carried out on a machine not working in the network. After the machine body is filled with new cooling gas, the relay equipment is switched, the protection device is reconfigured, and only then the machine is turned on. Consequently, the organ for changing the cooling gas setpoint of the synchronous machine performs the function of a step change in the magnitude of the signal Uoc when the cooling gas of the synchronous machine, i.e. for the same value of excitation current

the input of the imaging device 4 signal U0c takes only one of two possible values. To determine which channel triggered the protection device, the logical element OR 10 can be

it is supplied with channel bodies of indication. If it is necessary to perform a channel health check during operation, channel check organs can be added to the device circuit.

The use of the differential channel constructed in this way makes it possible to increase the sensitivity of protection, and the presence in the channel of variable

proportional to the change of the U and Uoc signals of the deadband boundary reliably protects the exciter of the brushless synchronous machine in the entire range of excitation current excitation from

zero to twice the value (Fig. 2). Eliminate false positives of the device. The use of the asymmetry detection channel in the specified protection device allows the asymmetry to be detected not only in

the voltage of the rotating rectifier and preserve the intact rotor diodes, but also indirectly detect the asymmetry of the rectified voltage of the thyristor power converter from the excitation winding of the exciter generator.

The use of a unit for changing the cooling gas supply unit eliminates the cost of resetting the protection device when transferring a synchronous machine from one cooling gas to another and protects the input of the second pulse generator. Thus, the technical and economic effect of using the proposed protection device consists in reducing the forced downtime of the main equipment due to the false operation of the ultrasonic type 2. reducing damage caused by damages in the rotating exciter generator and eliminating the cost of resetting the protection device during the transition of the synchronous machine from one gas to another.

The protection device can be used in brushless synchronous generators, compensators and motors.

Claims (1)

The invention The protection device against internal damages of a synchronous machine, containing an exciter core current sensor, the output of which is connected to the passage of the first signal conditioner, the first output of which is connected to the first input of the comparison unit 5, the reference input is connected to the second input of which, the comparison unit is connected to the first input of the logical element OR. the output of which is connected to the actuator input, the exciter excitation current sensor, the second pulse shaper, the output of which through the measuring and time delay organ is connected to the second input of the logic element OR, the second output of the first signal shaper connected to the second input of the measuring body, characterized in that. what. In order to increase sensitivity and expand functionality, it is additionally equipped with an asymmetry detection unit, a unit for changing the cooling gas setpoint of a synchronous machine, the input of which is connected to the exciter excitation current sensor, and the output to the input of the second pulse shaper, the first the input of the asymmetry detection unit is connected to the first output of the first signal conditioner and the second output of this driver is connected to the second input of the asymmetry detection unit, which consists of a series-connected organ cf. and converting the signal and the response delay body, the output of which is the output of the block asymmetry events connected to the third the input of the logical element OR, and the inputs - the inputs of the comparison and conversion organ. Breakdown of the rotary diode I if to Asymmetrical short circuit (Mx) V / Border of zone I of destruction / third channel Uoc (2l. Number) UK IS-HO} and dig. Mr.) - At wasps (is. non) / / / / / // /; g / / / Expansion of boundaries / zones not / g / VSl7bi / 77lnos / 77 {/ first channel Neububs / lobeness of the urban canal border  /  / Simme / gtrmnoe X.E. ft / xl I ABOUT Ib. nom (Rig. G Simme / gtrmnoe X.E. ft / xl CL & HOM