JP2556927B2 - Ratio differential relay for transformer protection - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ratio differential relay for protecting a transformer, and more particularly, to prevent malfunction caused by an inrush current of excitation and speed up at the time of internal accident at power-on. The present invention relates to a ratio differential relay for protecting a transformer.

[Prior Art] A ratio differential relay is generally used for protection of a transformer, and when a transformer is connected to a grid, a rush current of 10 times more than the rated current may flow in the transformer. Is the same as the reactor because the magnetic energy on the primary side and the secondary side of the transformer are not the same, and it looks like an internal accident, and the differential relay malfunctions.

Therefore, there is a ratio differential relay with second harmonic suppression in the related art for making a distinction between the inrush current and the internal fault current. FIG. 3 is a circuit diagram showing a conventional ratio differential relay with second harmonic suppression disclosed in, for example, Japanese Patent Application Laid-Open No. 53-111451. In the figure, (21) is a CT differential circuit, and (22)
Is the input transformer, (23) is the second harmonic stop wave transformer, (24)
Is a working coil, (25) is a second harmonic pass wave filter with fundamental wave blocking, (26) is a suppression coil, and (27) is a working coil (2
4), a relay element composed of a suppression coil (26).

Next, the operation of the conventional ratio differential relay shown in FIG. 3 will be described. When an internal fault current or excitation inrush current input occurs in the CT differential circuit (21), the DC component in these differential currents is removed by the input transformer (22). After that, the second harmonic blocking wave device (23) of L and C causes the harmonic components other than the fundamental wave and the second harmonic to flow into the operating coil (24). On the other hand, the second harmonic component flows into the second harmonic passing waveguide with basic blocking (25), so that only the second harmonic component flows into the suppression coil (26). Since the excitation inrush current contains a large amount of the second harmonic as compared with the fault current, the fault current flows through the operating coil (24) and the excitation inrush current flows through the suppression coil (26). Therefore, the internal accident current and the magnetizing inrush current can be discriminated, and the operation coil (24) causes the trip after the internal accident.

[Problems to be Solved by the Invention] Since the conventional ratio differential relay for transformer protection is configured as described above, the second harmonic blocking wave and the second harmonic passing wave with fundamental wave blocking are Depending on the difference in phase characteristics or power-on, the conditions other than the second harmonic wave may flow into the operating coil side and cause malfunctions depending on the conditions for applying the next inrush current and system specifications. Although it is not detected, the relay is unnecessarily locked due to the content ratio of the second harmonic, and there is a problem that it cannot operate at high speed due to an internal accident at power-on, residual magnetic flux on the suppression coil side, etc. It was

The present invention has been made to solve the above problems, and a transformer capable of preventing a malfunction caused by an exciting inrush current at power-on and speeding up an internal accident at power-on. The purpose is to obtain a protection ratio differential relay.

[Means for Solving the Problem] A ratio differential relay for protecting a transformer according to the present invention detects a ratio differential detection element for determining an internal / external accident of a transformer and an exciting inrush current at power-on. A detection element, a gate means for taking a logical product of the output of the ratio differential detection element and the output of the detection element, and a first time coordination timer provided on the output side of the ratio differential detection element, When a second time coordination timer provided on the output side of the gate means and an exciting rush current at power-on are detected, a relay is activated according to the time settings of the first and second time coordination timers. And means for controlling so as not to trip.

[Operation] In the present invention, the relay operation lock signal is substantially controlled by the ratio differential detection element, that is, the logical product of the output of the ratio differential detection element and the output of the second harmonic detection element is obtained. Therefore, do not lock unnecessary relays,
The speed at the time of an internal accident at the time of turning on the power is increased, and the time coordination of the two signals that operate with the excitation inrush current at the time of turning on the power is performed by the timer in the next stage to ensure lock cooperation and prevent malfunction of the relay. To do.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing an embodiment of the present invention. In the figure, (1) is a ratio differential detection element for determining an internal / external fault of the transformer, (2) is a second harmonic detection element for detecting an inrush current when the power is turned on, and (3) is a ratio difference. An AND circuit as gate means for taking a logical product of the output of the motion detecting element (1) and the output of the second harmonic detecting element (2), and (4) is provided on the output side of the ratio differential detecting element (1). Operation timer, (5) an operation timer provided on the output side of the AND circuit (3), (6) a recovery timer provided on the output side of the operation timer (4), and (7) an operation timer (5 ), A recovery timer provided on the output side, (8) is a recovery timer (6),
Inhibit circuit that receives the output of (7), (10) is the signal line that becomes'H 'signal when the ratio differential detection element (1) is operating, and becomes'L' signal when it is not operating, (11) is the second harmonic detection A signal line in which the element (2) is an “H” signal when it is in operation and an “L” signal when it is not in operation, (12) is an output signal line of the ratio differential detection element (1) and the second harmonic detection element (2), (13) is the output signal line of the operation timer (4), (1
4) is the output signal line of the operation timer (5), (15) is the output signal line of the recovery timer (6), (16) is the output signal line of the recovery timer (7), and (18) is the inhibit circuit (8). The trip signal of the relay can be obtained from the output signal line of. The operation timer (4) and the recovery timer (6) constitute a first time coordination timer, and the operation timer (5) and the recovery timer (7) are the second timer.
Configure a timer for time coordination of.

Next, the operation of the embodiment of the present invention shown in FIG. 1 will be described with reference to FIG. When the magnetizing inrush current at power-on flows into the relay, the ratio differential detection element (1) for judging internal / external accident operates because the same differential current as in internal accident flows, and the signal line (10) is L → It becomes H.
On the other hand, the second harmonic detecting element operating at the second harmonic content rate with respect to the fundamental wave also operates, and the signal line (11) goes from L to H. Here, FIG. 2 illustrates the case where the malfunction is most noticeable. In this case, the relay malfunctions, but the signal on the signal line (10) is obtained from the signal on the signal line (10) by using the operation timer (4) and the recovery timer (6).
The signal on the signal line (12), which is an AND output of the signals 0) and (11), is delayed from the signal line (15) and is faster than H → L, so that the trailing edge is delayed by the recovery timer (7) for a predetermined time. A signal is obtained on the signal line (16), which prevents the relay trip signal from being output to the signal line (17).

Further, if only the signal of the second harmonic detection element (2) that detects the inrush current of excitation, an unnecessary relay lock signal is output to the signal line (12), but the output of the ratio differential detection element (1) By taking the logical product of and with the AND circuit (3), an unnecessary relay lock signal is not output and the speed at the time of an internal accident at power-on can be increased.

In the above embodiment, the second harmonic of the magnetizing inrush current of the transformer has been described, but other harmonics can be used as long as the magnetizing inrush current and the internal accident can be distinguished. Further, the AND circuit (3) can be omitted if it is not necessary to speed up the internal accident at the time of turning on the power.

[Effects of the Invention] As described above, according to the present invention, a ratio differential detection element for determining an internal / external fault of a transformer, a detection element for detecting an exciting inrush current at power-on, and the above ratio differential are provided. Gate means for taking a logical product of the output of the detection element and the output of the detection element, and a first provided on the output side of the ratio differential detection element
Time cooperation timer, a second time cooperation timer provided on the output side of the gate means, and when the exciting rush current at power-on is detected, the first and second time cooperation timers Since the relay is controlled so as not to trip according to the time setting, the time until the ratio differential detection element determines the operation and outputs and the second harmonic detection element determines the operation and outputs. Irrespective of the time, the time setting of the first and second time coordination timers does not cause a malfunction and a highly accurate one can be obtained, and the ratio differential detection element and the second harmonic detection element can be obtained. By taking the logical product of both outputs, there is an effect that a ratio differential relay for transformer protection can be obtained which can speed up an internal accident at power-on.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a timing chart for explaining the operation of FIG. 1, and FIG. 3 is a circuit showing a conventional ratio differential relay for protecting a transformer. It is a block diagram. In the figure, (1) is the ratio differential detection element, and (2) is the second
A harmonic detection element, (3) is an AND circuit, (4) and (5) are operation timers, (6) and (7) are recovery timers, and (8) is an inhibit circuit. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

(57) [Claims] 1. A ratio differential detection element for determining an internal or external accident of a transformer, a detection element for detecting an exciting inrush current at power-on, an output of the ratio differential detection element and an output of the detection element. And a first time cooperation timer provided on the output side of the ratio differential detection element, and a second time cooperation timer provided on the output side of the gate means. A means for controlling the relay so as not to trip according to the time settings of the first and second time coordination timers when an exciting inrush current at power-on is detected. Protection ratio differential relay.