SU983874A1 - Device for protecting synchronous generator from earthing in one point of ebcitation circuit - Google Patents

Description

location closure location. This is related to the following. The sensitivity of protection, characterized by the value of the transient resistance trt, and in which, it reacts, is determined by the expression J- -. JucT. -Sh ot. ). where OCP is the current operating current; M is the voltage of the auxiliary voltage source; and - voltage between the point of the circuit and the point of the auxiliary source connected} Gr - resistance of the winding of the current relay. The first of the numerators is that the voltage of the auxiliary source varies almost insignificantly (± 10–15%). The second term is the voltage at the site of the damage — the value is peremesh and varies from 0 to the minimum excitation voltage and cannot be directly measured. For power generators, the nominal excitation voltage exceeds the voltage of the auxiliary source by 3-6 times (for example, when the auxiliary source UH.-T - ® metering from the counter current winding of the current relay is used, we have G - Cyst). the same current value, the first term is a constant value, and the second term is a variable value and can exceed the constant one - a value 6 times. Consequently, the magnitude of the transient resistance at which the protection operates may differ from the final value by a factor of 7. When shorted to earth at any place of winding and excitation of an unexcited generator, protection is minimally sensitive to transient resistances. The purpose of the invention is to improve the accuracy of protection by eliminating the dependence of sensitivity on the place of silence and the magnitude of the excitation circuit of synchronous generators. The goal is achieved by the fact that a known device for protecting a synchronous generator from earth fault at one point of the excitation circuit, containing a time relay, whose input is connected to the comparator output, one of the inputs of the comparator is connected to the negative output of the rectifier and the executive the organ further comprises a null indicator, a digital-to-analog converter, a square pulse generator, first, second and third keys, a subtraction unit, a pulse counter, a decoder, and a block of settings, while the generator is direct The pulse pulses are connected to the inputs of the digital-to-analog converter, the first and second keys, the control inputs of the latter, and the stop input of the digital-to-analog converter are connected to the output of the comparator, to which the starting input of the settings block is also connected, the output of the first key is connected to the input of the time relay, the output of the second key is via the third key connected to the main input of the subtraction unit, the output of which is connected to the main input of the pulse counter, the main | the output of which is connected through the decoder to the first input of the setting block, the second input of which. and control input; The third key is connected to the output of a null indicator connected by one output to the ground. and the second to the comparator, the positive output of the rectifier is connected to the positive output of the excitation winding, the output of the digital-to-analog converter is connected to the input of the supervisor, the output of the unit is us (barks are connected to the input of the executive unit, the output of the time relay, the inputs are set to zero of the setting unit, the counter pulses, a subtraction unit and a digital-to-analog converter are interconnected with each other and with the output of the digital-analog converter and a pulse counter output. Fig. 1 shows a block diagram of the proposed device; Fig. 2 shows the voltage at the output of the converter. The excitation source 1 is connected to the excitation winding 2 of the synchronous generator. The winding and the excitation source of the synchronous generator have a transient insulation resistance 3 and a distribution capacitance presented on the unit circuit relative to the ground (housing). with a concentrated capacitance 4. The positive terminal of the sensor 5 is connected to the positive view of the excitation winding of the synchronous generator and the source of excitation, and a negative output through co.parator 6 and the zero switch 7s one with the grounding circuit, the comparator compares the current flowing in the circuit: insulation resistance obmot ka excitation vshr DC converter, a comparator 1Chl-shschikator, a ground loop with a predetermined current value. In the null indicator, the current flowing through the circuit described above is compared with the specified current value. It is triggered by changing the negative polarity of the current to positive. The input is connected to the output of a digital-to-analog converter (D / A converter) 8 and a ШШ 8 serves to convert the input pulses into a step voltage at the output. The main input of the DAC is connected to a generator of square impulses 9. Each pulse arriving at this input corresponds to a certain step in the output voltage. The stop input is connected to the comparator output and serves to stop the rise of the output voltage when the next pulses arrive at the main input. The zero input and the overflow of the DSP are connected together and combined with the output of the time relay 1O, the overflow output of the counter 11, the zero-setting inputs of the pulse counter, the subtraction unit 12 and the setting unit 13. The input set to zero of the D / A converter serves to set a zero potential at the output and a pulse at the output of an overflow in the case when the voltage is at the output of the digital converter. reached a maximum, and the next impulse passes to the main entrance. The main inputs of the electronic switches 14 and 15 are connected to the generator output 9 of rectangular pulses, the keys control inputs are connected to the output of the comparator 6. The output of the key 15 is connected to the input of the key 16, and the control input of the key 16 is connected to the output of the optical indicator 8. Time relay 10 its input is connected to the output of the key 14. The calculator 12 is designed to subtract from the total number of pulses received on. its input, the number of pulses corresponding to the block setpoint and proportional to the total internal resistance of the detector, comparator and null indicator (l VtVTP ° to the installation input), the recorded (setpoint) number of pulses before each new device operation cycle is reset to the zero state. The subtraction unit 12 is connected to the output of the key 16. A pulse counter 11 counts the number of pulses proportional to the transient isolation resistance. The input of the unit is zero and the output is full and the unit 11 is Inen and are connected to the time relay output 10, the DAC overrun output 8, the DAC zero setting inputs, the subtraction unit and the settings block. Overflow ixchulse at the indicated output of the block 11 after the next pulse arrives at the input, and the counter returns to its original state (zero). The input of the decoder 17 is connected to the main output of the counter 11. In block 13 of the fixing, a comparison of the magnitude of the transient resistance of the isolator is performed with the set point of protection. The first input of the unit of settings is connected to the output of the decoder 17, the second input is with the input of the nullbreaker 7, the start-up input - with the output of KbMnapaixjpa 6. The executive authority 18 will record the impulse passing from the output of the block of 13 settings. The operation of the device is considered in the following four cases: the transition resistance of the isolation of the excitation circuit approaches infinity; transient insulation resistance is less than the threshold of sensitivity of the device, but more than the limit of the measured resistance; the transient resistance of the insulation to the booplie. the resistance of the set points, but less than the predetermined measured resistance} the transient resistance of the system is less than the resistance of the set point. The transient resistance of the isolation circuit excitation approaches infinity. The pulses from the square-wave generator 9, operating non-electric, but coming in at the input of the DAC 8, to the input. an open key 14 and to the input of the key 16 through a closed key 15. The output rectangular voltage modulated by the step voltage (Fig. 2) of the converter 8 is fed to the input of the drive 5. The straightened step voltage is applied to the field winding. Since the voltage as a voltage has a stepped form, then with the advent of a new stage, a bright current begins to flow along the circuit: rectifier, comparator, zero indicator, grounding, and field circuit capacitance. The time between two pulses of the generator, and, consequently, the duration of one step, is chosen so that during this time the capacity of the excitation circuit is fully charged. The comparator and the null indicator are implemented so that they can only be triggered before the start of a new stage and, therefore, does not respond to the charging current.

The pulses arriving at the input of the transducer 8 draw in an increase for example. At its output, and, consequently, at the output, rectifier 5, However, the magnitude of the maximum output voltage, 5 Bsr, because of the high insulation resistance is insufficient for; receiving in the circuit a null indicator and a comparator of the current required for their replication. wipe, and the signal at their output is missing - About vuet. After the arrival of the th pulse at the input of the converter, the voltage on the BI course reaches the maximum value, and after the arrival of the (I) pulse at the overflow output, a signal appears that sets the settings block, the pulse counter, and the block to zero. subtraction. Since no information was received at the inputs of these blocks during the work cycle, this signal will not change the constituent blocks. However, if interference was received at the input of a block, the signal of setting to the zero state will set the block to the zero state. Thus, the immunity of the protection device is increased. With the arrival of a subsequent impulse, the described process begins anew. At the output of the executive body there is no signal and the protection device does not work. Maximum voltage at the output of the rectifier

J BblXNVWC, GLOC-S,

; - the maximum number of steps of the generator, equal to the number of pulses at its input, is the voltage of one step. The transient resistance of the insulation is less than the threshold. Sensitivity of the device, but greater than the limiting measurable resistance. As in the first case, the superimposed voltage superimposes on the excitation circuit and increases stepwise, G increases with a stepwise voltage, when the current in the null indicator changes direction, and at the moment it crosses zero, the output of the zero indicator turns out the signal, which closes the electronic key 16, the rectangular pulses arrive at the input of the subtraction unit 12. At the output of the subtraction unit, pulses of TC are in the case when the number of pulses exceeds the setpoint of this block 7. From the output of the subtracter, pulses arrive at the input of the counter of 11 pulses, through the decoder 17 to

block 13 settings. When the number of pulses arriving at the counter, its capacitance, is exceeded, a signal appears at the overflow output, which sets the well, the left state of the setpoint block 13, 11AP 8 and the subtraction block 12. With the arrival of the post-pulse pulse, the described process begins anew. Since the value of the insulation resistance exceeded the value of the setpoint, there were no signals at the output of the setpoint block and the actuator and the protection device does not work.

Insulation resistance

Claims (6)

1. Author's No. 189594, ki. H 02 F 7AD6, 1966 2. USSR author's certificate number 612338, cl. H O2 H 7/06, 1978. 3. Guganov D V. Sensitive protection of the excitation circuits of the generators and synchronous compensators against a ground fault at one point. Operating experience of relay protection, automation and remote control in the Dneproenergo system, BTI ORGRES, 1964, p. 92-96. 4. The patent of Germany No. 2545325, cl. C O1R 27/18/1979. 5. USSR author's certificate number 402114, cl. H O2 H 7 / O6, 1973. 6. Guidelines for relay protection, out. 5, 1963, p. 39, j-, i0i-fig. 2