JPS58123317A - Transformer protecting and relaying device - 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 protective relay device for a transformer with measures against magnetizing inrush current.

When a transformer is connected to a large-capacity system, a magnetizing inrush current containing harmonic components flows into the system, causing the differential relay used to protect the transformer to malfunction.

A number of countermeasures have been taken in the past for this phenomenon, but currently the most effective measure is a method that utilizes the second skin wave component, which is contained in large quantities in the excitation inrush current. is used.

As a protective relay device using this second harmonic component,
There are two types: digital and traditional analog.

Figure 1 shows the inside of a circuit showing a digital protection relay with a countermeasure against magnetizing inrush current malfunction using the second harmonic belonging to the former type, and in the figure, the ratio differential relay (1) is connected to the input line (2). The port in response to a fault current from the transformer closes the normally open contact (1a) and sends a trip signal to protect the transformer (not shown). - When the detection circuit (3) detects the second harmonic component in the fault current, the signal line (
4) sends out a locking signal which prevents the ratio differential relay (1) from responding. The normally open contact (la) of the ratio differential relay (1) therefore remains open. In other words, the ratio differential relay (1) maintains a non-operating state and does not malfunction in response to an excitation inrush current that contains many second harmonic components.

Figure 2 is a circuit diagram showing an analog protection relay device with second harmonic suppression that belongs to the latter category. However, even if the normally open contact (5a) is closed, the second harmonic suppression element (6) does not operate, and since the normally open contact (6a) is open, the whole does not operate, and the magnetizing inrush current There is no chance of it malfunctioning.

Here, the principle of detection of the second harmonic wave will be explained with reference to FIGS. 8 and 4. First, as shown in the eighth factor and Figure 4, take the sampled values of the current at 180 degrees,
Calculate the sum of C and detect.

In other words, in the fundamental wave current shown in Fig. 8, the current value at sampling point (7) is t (t-180), the current value at sampling point (8) is i (t), and when the sum is taken, the following equation is obtained. .

1(t) 10i (t-180)=0
...(1) Next, for the second harmonic current shown in Fig. 4, the sampling point (9) is set to 1 (t-180
), taking the sum with the sampling point αQ as 1(t), we get t(t)+t (t-180)←0
...(2) becomes. Therefore, the sum of equation (2) is 0
If it does not, it is determined that there is a 2nd harmonic component.

By the way, the frequency of transformers in power plants changes from 0 to about twice the rated frequency. Therefore, when using the digital protective relay device described above, there is a frequency at which the sum of the sampled values of the currents shifted by 180 degrees does not become 0, and even if an internal failure occurs in such a case, the detection circuit (3 )
Therefore, the ratio differential relay (1) may be locked and the trip signal may not be sent. In addition, even in the case of an analog protective relay device, the second harmonic suppression element (6) works at a frequency that is approximately twice the rated frequency, and does not operate even in the event of an internal failure and sends out a trip signal. It disappears.

This invention was made in order to eliminate the above-mentioned drawbacks of the conventional technology. During operation at the rated frequency, the locking mechanism using the second harmonic and the second harmonic suppressing element are activated, and the rated Even during external frequency operation, in the event of an internal failure,
The purpose is to provide a protective relay device for transformers that operates reliably.

An embodiment of the present invention will be described below with reference to FIG.

(1), (2J, (3) and (4) shown in the figure
are the ratio differential relay (1) and the input line (2) explained in Figure 1.
), a detection circuit (3) and a signal line (4), αυ is a frequency relay that operates at a frequency other than the rated frequency and opens a normally open contact (llb).

In the case of rated frequency operation, the frequency relay Oυ shown in the figure is inactive and the normally closed contact (Hb) remains closed, so the second adjustment is performed by the detector @ (3) as in the conventional device shown in Figure 1. It will not malfunction due to waves. - In the case of operation at a frequency other than the rated value, the normally closed contact (LLB) is activated by the operation of the frequency relay aυ.
is opened and the signal line (4) is cut off, so the operation of the ratio differential relay (1) will not be locked. Therefore, in the event of an internal failure, it operates reliably and sends out a trip signal.

By the way, the pressure regulator (not shown) is not turned on when operating at the rated frequency, so there is no malfunction due to the sulfur intrusion flag when operating at a frequency other than the rated frequency.

In addition, in the above embodiment, the normally closed contact (
I tried to cut off the lock signal by opening 1lb), but
As shown in Figure 6, the system frequency from the outside opens the normally closed contact (12b) of Kamisuke Relay 4, which is activated by the command for rated external frequency IkI operation, and the signal line (4) of the detection circuit (3)
Alternatively, as in the seventh cause, the normally closed contact (12b) of the auxiliary relay trunk may be detected (b) omitted (3).
Even if it is inserted into the input line (2) of 0, the same effect as in the above embodiment can be obtained.

Furthermore, as shown in Fig. 8, for a ratio differential relay with second harmonic suppression, the normally open contact (12
a) is closed, the second harmonic suppression element (6)
Of course, it is also possible to keep it in an operating state.

As described above, according to the present invention, when operating at a frequency other than the rated frequency, the trip signal of the ratio differential relay is disabled, or the suppressing force of the 2nd i#l harmonic suppressing element is prevented from working, so that the rated frequency can be reduced. A protective relay device for transformers that can reliably detect faults even when using external frequencies is now available.

[Brief explanation of the drawing]

Figures 1 and 2 are circuit diagrams showing conventional protective relay devices for transformers, Figures 8 and 4 are diagrams of the second harmonic detection method, and Figure 8 shows the basic waveform. , FIG. 4 is a diagram showing the second harmonic waveform, FIG. 5 is a circuit diagram showing an embodiment of the protective relay device for a transformer according to the present invention, and FIGS. 6, 7, and 8 are diagrams showing the second harmonic waveform. FIG. 3 is a circuit diagram excluding another embodiment of the present invention. (1) is a ratio difference wJ relay, (1a) is a normally open contact, (2
) is the input line, (3) is the detection circuit, (4) is the signal line, αυ
is a frequency relay, Q2 is a passive relay, (llb), (
12b) C is a normally closed contact. Note that the same reference numerals in each of the above figures indicate the same or corresponding parts. Agent Shin Haru Shima - Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (3)

[Claims] (1) A ratio differential relay that sends out a trip signal in response to a fault current in the transformer; a trip signal for the ratio differential relay in response to the second harmonic in the excitation inrush current of the transformer; a second harmonic detection circuit that sends out a lock signal; and a frequency relay that detects that the excitation frequency of the transformer deviates from the rated frequency and prevents the second harmonic detection circuit from sending out the lock signal. A protective relay device for transformers featuring: (2) The protective relay device for a transformer according to the first claim, wherein the frequency relay cuts off the input to the second harmonic detection circuit when the frequency relay detects an out-of-rated frequency. (3) A protective relay device for a transformer according to the first claim, characterized in that the output of the second harmonic detection circuit is cut off when the frequency relay detects an out-of-rated frequency.