JPS5928834A - Transformer protecting relay unit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a transformer protection relay device u, and in particular, a detection method suitable for distinguishing between 61L of magnetizing inrush and fault current. Conventionally, the present invention is a method for preventing malfunction caused by magnetizing inrush current in transformer protection relays. As a result, when the second harmonic content of the current differential output signal in the protection zone is higher than a predetermined value (for example, 15 or more), it is determined whether the excitation inrush current is 1/, and the operational output of the transformer protection relay is blocked. That's what I do.

However, even in the event of an internal failure of a transformer, harmonics are generated due to the influence of the eight electrostatic charges in the connected system, and as the system becomes larger,
Components close to the 216th harmonic often occur, and their attenuation time constant tends to increase, making it difficult to distinguish between the two in terms of the content of the second harmonic.

An object of the present invention is to provide a method for correctly identifying the distorted wave current and the transformer's excitation inrush current bW at the time of an internal fault in the transformer.

The main point of the present invention is to focus on the fact that the condition for increasing the current in the transformer excitation inrush 1d is due to the unipolar saturation phenomenon on the DC side of the excitation circuit (m), and the positive half-wave and negative half-wave of the applied voltage are The difference in the fact that the distorted wave at the time of an internal fault is supplied to the linear inductance of both waves, whereas the inductance becomes unbalanced due to the ratio of the differential value of the current differential signal to the voltage applied to the transformer, is This is a method for determining whether there is an internal deviation (therefore f).

FIG. 1 shows a complete diagram of the overall configuration of an embodiment according to the present invention.
o The symbols and operations in the figure will be explained below.

■N, 1 is the transformer to be protected, P is the primary side, S&;
1.2 The side is shown at t', and the subscript P of each part and signal name is shown below.

8 indicates the meaning of primary and secondary sides.

Cr3 &J: L or breaker, CT is a current transformer, I) T is a 'TfLLE transformer. YLY is a transformer protection relay according to the present invention.

1 (, Y input signal is the voltage IK applied to transformer 1, 11 III P, I) via T3,
Each is equivalently converted to, for example, 11 ov at a rated 1% L pressure and is taken in. -Denote the signal as vP, vs.

You're talented, Den? +IC communication phase -CCT p, CT s
Via +, -C.

Manually convert the equivalently converted values i, . . . iB in the same way as voltage 3
, ! The polarities of p and i6 are the same under the conditions of flowing into the transformer. V, , V8 are similarly input in the same direction when 1 is healthy.

Le Y detected an internal accident, C13p, CIs
Make it s? 1.Prayer command 1.Responsibility to strengthen
It is.

Figure 2 shows the contents of 几Y in Figure 1 (~. [Figure 11 □
The same i symbol in Figure 1 is Jlarr.
They are equivalent to those shown in Figure 1.

21 is a 'ld current differential circuit, i P-I B total 3+)
↓I ↓I the output i. 22 is to obtain the minimum value of '11L voltage at the same time of VP and V8.If it is an ideal transformer, VP and ■ are equal and v:=vP=:Vs, etc., but in case of internal failure, The larger voltage ffE drop appears as the output.

23 is a differential circuit for current differential output i, and d i/di
The output will be generated.

24 is a circuit for finding the interftance, so we focus on its absolute 11α.

The reason why the absolute value II, 1 is determined here is that positive and negative values of different signs can be considered in view of the excitation impedance and leakage impedance of the transformer, as well as the excitation characteristics due to the hysteresis loop.

In the present invention, when the absolute value of the inductance (2) is small, it is determined that there is a possibility of an internal failure, and how long that absolute value lasts during one cycle of the fundamental wave is determined four times.

However, I L l cannot be calculated when I / (I t is zero, so in 24, however, I+,: Judgment level setting value, L L l2 L6 s song... Song... Let it be song (4).However, Lol+ is set to a value sufficiently larger than the level judgment LL that will later judge whether the value of l L + is low.

25 is a level determination unit of l L l, and II=l<
LL ・・・・・・・・・・・・・・・(
5>, an output is generated at 26.

Reference numeral 26 denotes an integrator, which integrates from 25 the condition f'1=-r when there is an output when formula (5) is satisfied, and subtracts the integral value when there is no output. Let the output of 26 be ]c.

27 is a level judger of Ls, and the integral value L g of 26 is
When exceeds the set value of Ls+, as ltY,
Detects an accident inside the transformer and generates a crest.

FIG. 3 shows an example of the operation according to the present invention using a waveform diagram. The figure is an example of a waveform assuming the excitation inrush current of a transformer.
1miv is a fundamental wave, and '1(') is shown in a shape close to a half-wave rectifier b1c.

di/di level judgment It, There is It, IL
When I is L+ or less, the integral value is increased in the increasing direction, LL
In the above, integration is performed in the decreasing direction, and the output thereof is indicated by Ls. When Ls>Lst, the operation output of ILY is obtained. Third
In the figure, the integral value decreases more than the increase, and the ILI is inactive.

Figure 4 shows the assumption of an internal failure in the transformer.
1L Jin no Tsuki issue 8 and ILY! Complete contents of iib work.

If'L voltage V is an example in which there is an internal fault but a fundamental waveform with residual voltage, '1llJbii is 1 which includes transient Irf flow.
1]. The phase of V and i produces a difference corresponding to the innovidance angle at the time of a transformer failure, but here it is considered to be almost inductive reactance, and Vd1 is shown with a phase of 90 degrees. l
~ Therefore, di/dt and V are in phase, and 1b
+ -l-,4-t/d〒l constant value tonal.

However, ldi/dtl (1'L is 1 block, 1 performance) 1
without performing 1Tll2Log.

The 41-segment value between IJ,l<:T,,L gradually increases, and BY operates according to ■,8>TJIIL at time 1R.

From the above, it can be seen from FIGS. 3 and 4 that the present invention can detect internal moon failure.

Next, even if we consider the case where the phase difference of ■dt I is not 90 degrees and the phase difference of position 7 is 1 (1t/dt l <
I! , the inductance is high only at , but conversely, l
d i /(lt 1) L 1. In this case, since the lower the level of ■, the lower the inductance lLl, it is natural that RY becomes on the active side.

However, in the case of excitation inrush current, the inductance is high during either the positive or negative half cycle and low during the other half cycle, which can be distinguished from an internal fault.

Also, in the event of an external failure,
It becomes 0 and becomes inoperable.

Next, even if we consider the case where harmonics are superimposed during an internal accident, the impedance at the time of failure can be considered to be constant, so if we apply the waveform diagram shown in Figure 4 to all harmonics, the same result will occur. There is no problem as long as the result is obtained and the superposition theorem holds in the circuit that produces V,i.

FIG. 5 shows an embodiment in which the calculations of the present invention are executed using a digital computer.

In the figure, reference numeral 51 denotes an input section which obtains input data by limp ringing. Also, input various setting values.

52 is the 'rlt flow differential meter η'' part, I-=-tP-
53 indicates a function for storing i in order to obtain di/dt.

54 outputs the output in part 1 of performance 1, which takes out the small force values of VP and V.

55 tit: d i /(lt (7)Nl'3
! In ff1t minutes, the value is -3,'5.
/ is the memory time).

When it holds, calculate ll71 at 57, and when it does not hold, set it as ll-1" 11os at 58, and set 11os at 59.
111 <I, L is determined, and when the same conditions are met, the counter of 6() is increased (+>T,); if not, the counter is decreased (M!) with the OR condition with 58.
At J)L,,at, it is determined whether or not the counter has reached a predetermined level. If the same condition is satisfied, it is determined that the transformer is malfunctioning, and if it is not satisfied (1-), it is determined that the transformer is healthy.

62 has an output for internal failure, CBp shown in Figure 1,
Give a cutoff command to C1's. When it is in good condition, it is output to 63, and if necessary, it is provided with a function to display that Example 1 is complete.

As described above, the first embodiment of the present invention (a 28-wire transformer has been shown as an example, but even a multi-winding transformer can have an input voltage of 5 voltages).

The same implementation is possible only by increasing the number of signals.

Example of the sixth example - (l uses the minimum value of V and 17 and VP and Internal with or condition - 1
1 reason may be 1' (1 constant l~).

Also, l 1'-l < l, 1. In the judgment, i also L< is 11・, is TJL by each scale 711
It is possible to perform so-called ratio differential determination that changes the level of .

If you trace IT, l<]le+I(R(l ipH-11gl)
...(6) is an example. However, I(R is a suppression constant.

Furthermore, the level of LsL may be changed by a scalar sum.
By using it with a differential relay, high performance and increased reliability can be obtained. According to 1jllJ, it is possible to realize a transformer capable of high-speed operation with a simple 11) transformer that can operate at high speed.

Therefore, even as a relay device using a computer, it is economical and effective.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram for explaining the overall concept of the present invention, FIG. 2 is an operational block diagram of the present invention, and FIG. 3 is a diagram showing the excitation inrush current! 1
FIG. 4 is an explanatory diagram of transformer internal failure detection, and FIG. 5 is a calculation flow diagram of the present invention. 21... Current differential circuit, 22... Voltage minimum value deriving circuit, 23... Differentiator circuit, 24... Inductance calculation circuit, 25... Level judgment circuit, 26... Integrator , 27... Level determination circuit. Agent Patent Attorney Akio Takahashi Figure 4 Figure 5

Claims (1)

[Claims] 1. Differential of transformer terminal current difference current and transformer terminal '+U
, find the ratio of IJ2, and period 1 during which the ratio exceeds a predetermined value.
A transformer protection relay device which determines the protection of the transformer from a period not exceeding 1, . 2. Find the ratio of the transformer terminal 'elf, the difference in current 1, the differential of the current and the transformer terminal M, 7 voltage, from the period t1) during which the ratio exceeds a predetermined value, and the period IP during which it does not exceed, . a first IJ l/- providing the protected output of said transformer;
A transformer protection relay box that protects the transformer from two outputs and is equipped with a second relay that detects and outputs an internal fault in the transformer according to the L flow.