SU758357A1 - Device for differential-phase protection of electric equipment - Google Patents

Description

The invention relates to the field of relay protection and can be used to protect "busbars, transformer busbars, power transformers, autotransformers, generators and large electric motors of power plants and substations.

A device is known for differential-phase protection of station and substation busbars, which contains current sensors, a diode conversion circuit for input values, a comparison circuit, a phase element, a starting element [].

This device is not applicable to (5 transformer protection, as the measuring element of the Phase organ has a constant threshold for measuring the duration of the input signal, as a result of which the protection has a low sensitivity to internal damage with leakage current, ie, it is not sensitive to coils in the transformer. In addition, it may have insufficient 25 speeds during short circuits, accompanied by a transient process in current transformers, since the blocking angle corresponds to the response time When the internal 30

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their damage, also the protection has a complex diode conversion circuit of the input values.

It is also known a device of differential-phase protection of a transformer, containing current sensors, a diode circuit for converting input values, a comparison circuit on resistors and zener diodes [2]. However it is. the device has a complex scheme for converting input values and low speed for internal faults, since a polarized relay with a relatively long intrinsic response time is used as the response body.

A device is known for differential-phase busbar protection, containing current sensors included in each arm of protection, a multi-shoulder diode half-bridge, a two-arm comparison circuit connected to it on resistors and zener diodes, a phase element connected with a comparison circuit through a rectifier bridge, a starting element, a logic unit, and , two inputs of which are connected to the outputs of the starting and phase organs G3].

"-" '7 h. 758357

However, this device cannot be used to protect transformers. In it, the measuring element of the phase organ has a constant threshold for measuring the duration of the input signal. Transformer protection must go to the differential-phase mode with input points equal to 1 _ax = 1> 8 - 2.0 1 _N (1 _n is the rated current). · ·

Phase blocking angle. ~

70-80 ° when the input signal is straight ..... coal form, when the input current

Ιβ / ^ Ιη at the same time, the response current of the transformer protection must be equal to 0.25-0.3 1 ^ so that the protection will operate when there is a short circuit. Consequently, the level of the input signals of the phase organ during the turn-around closure is 6-7 times less than the level of the input signal in the differential-phase mode at that time

as the maximum possible angle at which it is still possible to trigger (180 °), only 2.5-3 times the "" blocking angle. Therefore _{, the} protection of small signals will not succeed in triggering. In addition, it has a low speed of internal damage, since the blocking angle corresponds to the response time of the near-point damage. --------- ', ....'., ...,

The purpose of the invention is to expand the 'functionality and improve performance.

This is achieved by the fact that, in the preface, the “GGSHMO device is a trim!

comparison made on resistors, diodes and zener diodes, the cathodes and anodes of which are connected respectively ....... to the cathodes and anodes of the diode

block conversion of input values, starting body included between the common point of the secondary windings. input current sensors and diodes 45

“Comparison unit, rectifier bridge,

'the output of which is connected to the input

phase organ, logical block TH, '

whose entrance ^; Soi Di yena with outputs of the phase and starting organs / entered 53

---------- Limit voltage, two. Expensive • element, block 'electroplating .....

the separation of the chains of the cotsr'bgo chain is connected to the output of the comparator unit,

'...... and the output is at the rectifier input $$

the bridge to which the output is connected

..... voltage limiter, and the input of the second ------------- go ’of the threshold edement, the output is ......

—The threshold elements are connected to the input of the phase reference voltage ’

...... authority, the entrance of the first threshold element 60

'Menta' is connected to the cathode of one zener diode of the comparison circuit, and the anode. another stabilitron comparison circuit

with anode rectifier DNR

1 bridge.

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The drawing shows a structural diagram of the proposed device.

The device contains a block of input current sensors 1, whose ends of the same name are connected, and a diode block 2 converts input values to another, a comparison block 3 made on resistors, diodes and zener diodes whose cathodes and anodes are connected to the cathodes and the anodes of the diode unit 2 conversion of input values, the starting body 4, connected between the common point of the secondary windings of the input current sensors 1 and the diodes of the comparator unit 3. To the output of the comparator unit 3 through the unit 5 galvanic isolation of circuits connected pit bridge 6, the second diagonal of which is connected to the voltage limiter 7.

The threshold elements-8 and 9 are connected between the comparison unit 3 and the phase, organ 10. The logic unit 11 is connected between the starting organ 4 and the phase organ 10.

The device works as follows.,.

The currents from the current transformers of the protection arms arrive at the primary windings of the sensors. The currents, the secondary currents of which are separated by the half-period sign of the diode-conversion unit 2. Both Zener diodes of the comparison unit open and limit the voltage on his shoulders. If .. while doing this, one of the current transformers of the protection arms is saturated, the tone of the output of the comparison unit appears-. There is a sequence of pulses of unchanged amplitude with a duration proportional to the phase error of the current transformer. With an increase in the short circuit current multiplicity, these pulses approach the rectangular form. The indicated sequence of pulses through the electroplating separation circuit 5 and the rectifier bridge 6 enters the working input of the phase element 10, where the voltage suppressor 7 is limited in amplitude. ^: The input of the reference voltage of the phase organ 10 is supplied to it either from the output of the first threshold element 8 or from the second 9. The first threshold element 8 opens when the voltage is between the points. "A" and "b." The comparison unit approaches 2 and _st , where Ost is the voltage stabilizing one stabilizer of the comparison circuit. In this case, the second threshold element 9 is locked.

In the above, the case of external short circuit voltage between the Points "a" and "b" of the comparison unit is 2 равно, τ therefore, at the input

five

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the reference voltage receives a signal amplitude and, from the output of the first threshold element 8.

The sensitivity of the measuring element of a phase organ, for example, a single junction transistor, decreases with increasing voltage at the reference voltage input (voltage base 1 - base 2). Consequently, the blocking angle of the phase element 10, made, for example, according to the time relay scheme, depends on the voltage value at the input of the reference voltage, the signal value at the working input of the phase element and the value of the parameters of the time relay elements. audio, K and C for example, and with increasing cheniem signal ^e at the input of the reference 'voltage phase angle lock body increases. When an external short circuit and saturation of one of the current transformers of the protection shoulders to the working input of the phase body 10 receives a sequence of pulses limited by the voltage limiter 7. If the phase error is less than the blocking angle, the 25 phase body 10 does not work and 1 on one from the inputs of block 11, the signal will be equal to zero, so even if the triggering organ 4 is triggered, there will be no signal at the output of the block (protection does not trigger 30). In case of internal short circuit of large multiplicity (phase mode of the relay), only one arm of the comparison unit 3 flows through the current, therefore, the threshold element 8, 35

will be closed and the input signal of the reference voltage of the phase organ will receive a signal from the output of element 9. The voltage of this signal is proportional to the signal at the working input of the phase dd

organ 10. This increases the sensitivity of the threshold element of the phase organ (unijunction transistor). The working input of the phase organ receives a signal determined by the voltage of the voltage limiter. The parameters of the time relay did not change, therefore ', in' mode, internal circuit, the blocking angle is reduced compared with the external short circuit mode. Starting body in this mode is triggered, voltage is applied to both inputs of the block, therefore, the output of the block AND also has a signal (protection triggers). 55

When an internal short circuit with phase-in flowing currents at an angle close to, the input signal of the reference voltage of the phase organ receives a signal from the output of the first threshold element 8, because for some time they will flow around the currents of both arms of the comparison unit. In this mode, the blocking angle keeps the same value

60

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as with external short circuit. However, the probability of such a mode is small, since the zener diodes of the comparator unit open in this mode approximately at a current exceeding (1.8-2.0) 1 _And by the magnitude of the response current, i.e. about 2.3.

Such a short-circuit current, shifted to / is almost unbelievable, since the main component of the shift is the mutual angle between the emf of power sources, the value of which increases with the resistance of the connection between the sources operating in parallel. But the same resistance, and limits the short circuit current.

At low short-circuit currents, the protection will operate in a differential mode, since the signals in comparison unit 3 are not limited in amplitude and not limited to voltage limiter 7, while regardless of the phase of the input signals, the input voltage of the reference voltage is proportional to the signal at the working input

phase organ, and the sensitivity of the measuring element of the phase organ 10 remains constant, i.e. the presence of leakage currents in case of internal damage does not deaden the protection. The scheme also works for large inflowing and low flowing currents, since there will be no doubling of voltage in the comparison circuit. In this case, the sensitivity of protection in general will be determined by the triggering threshold of the triggering organ 4, since until both inputs of block I .11 do not receive a signal from the triggering and phase organs, the protection does not work, and the sensitivity of the triggering organ is lower than the sensitivity of the phase organ.

Thus, the proposed device for differential-phase protection compared to the most advanced technical solutions,

In particular, compared with proto-. pom, provides higher speed in the internal damage mode, sensitivity in the internal short circuit mode with a flowing current of Mer ~ .θ 31 kt \ which allows its use to protect tires, busbars of power transformers, generators, powerful motors, as well as when connecting to it is a block of detuning from magnetization current surges to protect power transformers.

Expansion of functionality, i.e. using the same device to protect various elements of power plants and substations, will reduce the cost of production of protection, and their *

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operation. High sensitivity protection will reduce the amount of damage during winding short circuits in power transformers. High speed of protection reduces damage in case of system accidents, as well as the amount of destruction of the protected object.

Claims (1)

Claim A device for differential-phase protection of an electrical installation, containing a comparison unit, made on resistors, diodes and zener diodes, the cathodes and anodes of which are connected respectively to the cathodes and anodes of the diode conversion unit of input quantities, the starting element connected between the common point of the secondary windings of the input current sensors 20 and the diodes of the unit comparison, the rectifier bridge, the output of which is connected to the input of the phase organ, the logical block I, the inputs of which are connected to the outputs of the phase and starting '25 organs, characterized by the fact that, in order to expand functionality and increase speed, a voltage limiter, two threshold elements, a galvanic separation circuit, the input of which is connected to the 5th output of the comparator and the output to the input of a rectifier bridge, to the output of which the voltage limiter and the input of the second threshold element, the outputs of the same threshold elements are connected to the input of the reference voltage of the phase element, the input of the first threshold element is connected to the cathode of one zener diode of the block with alignment, and the anode of the other Zener diode on the comparison unit is connected to the anode of the rectifier bridge.