SU945935A2 - Device for starting quick-action relay protection system - Google Patents

Description

The invention relates to electrical engineering, in particular to devices for starting relay protections of three-phase high-voltage power lines;

According to the main author. St. No. 845212, a device is known that contains a three- ⁵ phase current filter of the direct sequence, a three-phase current filter of the reverse sequence, the outputs of which are through three-phase rectifiers _{) 0 are} connected to the inputs of the first threshold unit ', a one-shot, the output of which is connected to one of the inputs of the output Executive unit, performing OR function, the second threshold _15, traction unit, RS-trigger, the logical OR block-HE, wherein vhody- second threshold unit connected to the outputs of three-phase rectifiers, output - with R-input of RS-trigger and to a second the way is the OR-HE logical unit house, the first input of which is connected to the output of the first threshold block, the output of the OR-HE logical unit is connected to the S-input of the trigger, the output of the latter is connected to the input of the one-shot and the other input of the output executive unit, the output of which is the output the whole DJ device, however, the known device has insufficient sensitivity with asymmetrical short-circuit through significant transient resistances. It works provided

(P

The sensitivity of the device increases with the ratio of proportionality coefficients ^

The value of γ is selected from the condition.

failure of the device in symmetrical modes (including symmetrical short-circuit), taking into account the unbalance current • z!

reverse sequence caused by errors in current transformers and reverse sequence current filters. The reverse sequence unbalance current Ij_ nb is proportional to the direct sequence current 1 ^ (2)

NOT . where N is

From (1) the choice of »Ν (σ _ττ + σφ) ΐ,

Coefficient of proportionality;

- relative errors of current transformers and filters. the reverse current flows of a-15 sequence, respectively. .

and (2) we can write the conditional coefficients K ^ and in (I)

..

K _g 'and glOx F (3)

The value of the relative error of current transformers Ογγ depends on ₂₅ values of currents flowing in the transformers, and the error increases with increasing values of currents. Given this, in (3), when choosing the ratio, one should take (Jj-j- maximum (6 _τ γ), that is, the corresponding maximum current flowing through current transformers. This condition limits the sensitivity (value • y) of the device for starting at short-circuit currents less than the maximum possible.

The aim of the invention is to increase the sensitivity for starting at short-circuit currents, less than the maximum possible.

This goal is achieved by the fact that in the device for starting high-speed relay protections, a functional converter is additionally introduced whose inputs are connected to the outputs of three-phase rectifiers, and the output to additional inputs of the first and second threshold blocks.

In FIG. 1 shows a functional diagram of a device; in FIG. 2 an example of the implementation of a functional converter in the form of a precision rectifier - inverter with a stable voltage source connected to the input; in FIG. 3 “response and return characteristics of known and proposed devices.

The device contains a three-phase current filter 1 direct follower40

945935 4 knots, three-phase current filter 2 of the negative sequence, three-phase rectifiers 3 and 4, first and second threshold blocks 5 and 6, logic block TsLI-NOT 7, RS-flip-flop 8, one-shot 9, output executive block OR 10, and additionally introduced / functional Converter 11. The device operates as follows.

When the unbalance in zaschischa- _(emoy filter outputs on lines 1 and 2 appear symmetrical three phase, voltage, currents proportional to the reverse and forward sequences which are rectified three-phase rectifiers 3 and 4 and at the inputs of inverter 11 govyh functional blocks 5 and 6 appear 2Q supply and - K, 1 ₄ , the voltage bf = -f (1 ^, j, which is also fed to the inputs of threshold blocks 5 and 6, is output at the output of the national converter 11.

At the output of the threshold block 5, the signal Logical 1 appears if - f (I ₂ , <K4I4, and the signal · ^ Logical О if - f (I ^, I.) 7

7Κ ₄ Ι ^, and at the output of threshold block 6, the signal is Logical 1 ^: at ¹ K ^ f ₂ - f and the signal is Logical О at К _2. ( ₂ - К _В К ₄ 1 ₄ , where Кр is the device return coefficient (Κθ <1).

In the mode when - f (I ₂ , I ^) <

Logic signals S-input of the RS-flip-flop 8 'Logical O and for a short time function 1 come to the inputs of the logical block OR-NOT 7, the signals are Logical О and, since the logic-1 signal is received at the R-input of trigger 8 from the threshold block 5, then the output The RS-flip-flop 8 has a logical O signal, the same signal is present at the output of the one-shot 9 and the output executive block OR 10, i.e. the output signal of the device is Ug _{b! X} = 0.

In the mode when - f (1. ^,) 7> at the outputs of both threshold blocks 5 and 6, the logic O signals appear, and consequently, the R-input of the RS-flip-flop 8 is supplied with Logic O and, since Logic 1 is applied to the signal trigger 8 fires, feeds a single-shot 9 triggered by the trailing edge of the control signal and is executed to the output _; S-input signal then control 945 935 6

In the case of σ _ττμο ^ <and currents

1 _K , ₃ <I nom *. ^{it is possible to} provide greater sensitivity of the device for starting high-speed relay protections.

At currents of symmetrical short circuit

to ⁵ block OR 10. Logical 1 signal appears at the output of the device. The appearance of this signal at the output of trigger 8 indicates the presence of an asymmetric mode. This state of trigger 8 persists even when K_ ₂ , 1 _g decreases, but only when K ^ I ^ - f (1 ^, 1 _g ) <К _В К ₄ 1 ₄ , trigger 8 returns when the RS-trigger is at the R-input 8, the logic 1 signal appears. At the output of trigger 8, the control signal disappears, the one-shot 9 starts, the output of which and the device as a whole for a given time keeps the logic I signal. The presence of the signal at the output of the one-shot -9 indicates the presence of a symmetrical mode, which was preceded unbalanced mode.

If a precision rectifier - inverter with a reference voltage source U _o n (Fig. 2) is used as a functional converter, the functional conversion. The tel performs the function of transforming the view.

£ (1 ^, 1 ^) = 0 for U _on <О ί ·· '. ·.

and: η "*

Then the operating conditions of the device can be written as

44 ^ 44 at K ^ -1 <O

44¾ - P ”W ⁰

The return condition also changes. By choosing, for example, U _on = K ₄ 1nrk _{<0, we} provide

4W < ⁿ ₽ ^and .44 - ΚΚΛ ₊ ki _op 7 K, I. for KD7 ^, 1 ^ In this case, based on assurance, selectivity in the symmetric mode,., We obtain

4.¾. '^< Chom _;

In this case, the condition must be met

CHOLL * ^ *. ^. ^ 4 * jvsokc selectivity is provided subject to the conditions

The triggering condition can be represented as.

h

А - у .1 Si characteristic where А = Κι (1 — К) В = KUo / K,. · In FIG. 3 shows the operation 12 and return 13 of the known device, as well as the response 14 and return 15 of the proposed device for starting high-speed relay protections in the case of a functional converter in the form of a precision rectifier-inverter.

Thus, the operation of the device for starting high-speed relay protections occurs at - f (L ·, ^) * 7, and the return at ^Λ

1 ^ 4 - f (I _T , I ₄ ) <Κ ₆ ΐς I,. Introduction of the conversion function £ (1 ^, 1 ^) in response conditions. and return of the starting element allows you to coordinate the response of the start-up organ with the characteristics of the measuring current transformers and reduce the ratio I ^ / lf necessary for the device to operate at short-circuit currents that are less than the maximum possible, i.e., increase sensitivity.

The choice of more complex conversion functions £ (1 ^, 1 ₄ ) allows you to further increase the consistency of the response characteristics of the device. with the characteristics of measuring transformers to increase the current more, which means more sensitivity.

Claims (1)

1. USSR Author's Certificate No. 845212, cl. H 02 H 3/08, 1979