JPH0147094B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a voltage relay device that detects a fault occurring in a power system based on a voltage drop caused by a fault current.

A conventional device of this type is shown in FIG. In the figure, 1 is the bus bar to be protected, 2, 3
4 and 5 are current transformers that introduce grid current into the voltage relay device, and 6 is used to prevent damage to the voltage relay device due to high voltage. 7 is a non-linear resistance element provided for destruction prevention like the saturable reactor 6, 8 is a high impedance transformer that obtains a voltage drop due to fault current, and 9 is a voltage relay that detects overvoltage. , 10 is a power supply. In addition, in the figure, F ₁ ,
F ₂ indicates the point where the accident occurred.

Next, the operation will be explained. The secondary sides of the current transformers 4 and 5 of all the lines connected to the bus 1 are connected in parallel for each phase, and the sum of their outputs is introduced into the voltage relay 9. If an accident F ₁ occurs outside the busbar,
Since the fault current I flows from the power supply 10 through the bus 1 to point _F1 , the secondary currents of the current transformers 4 and 5 are generated in the opposite direction and circulate as indicated by the dotted arrow.
Therefore, the current transformer secondary voltage V ₁ does not become a very large voltage, and the voltage relay 9 does not operate. However, when accident _F2 occurs inside the busbar, busbar 1
There is no outflow current from the power supply 10, and only an inflow current I flows from the power supply 10 toward the inside of the bus bar 1. At this time, the current transformer 5 does not operate because there is no passing current, and the secondary current of the current transformer 4 at the inflow end is introduced into the voltage relay device as a fault current _I1 . In this case, since the impedance inside the voltage relay device is very large, the current transformer secondary voltage V ₁ suddenly becomes a high voltage, the voltage relay 9 operates, and the insulation breakers 2 and 3 are suddenly disconnected. .

However, when a bus internal fault _F2 occurs, the current supplied from the current transformer 4 becomes _I1 flowing through the nonlinear resistance element 7 and the transformer 8, and this fault current _I1 generates a voltage _V1 . However, the induced electromotive force that prevents the magnetic flux from changing due to the input current generated by the voltage V ₁ in the saturable reactor 6 stops working when the magnetic flux reaches the saturation magnetic flux, and the saturable reactor 6 becomes conductive. Therefore, the fault current supplied from the current transformer 4 is the input current of the saturable reactor 6.
The current I ₁ decreases, and _{the voltage V 1 decreases} accordingly. This state continues until the polarity of the input current waveform is reversed, and after the polarity is reversed, the same process is repeated until the polarity is reversed again. In other words, the voltage applied to the voltage relay 9 can be obtained only during the saturation time of the saturable reactor 6 or the current transformer, and there is no continuous operation input.
Even if an internal accident occurs, the voltage relay 9 operates instantaneously, and even if the internal accident continues, the voltage relay 9 sometimes returns from operation. Therefore, voltage relay 9
If the response characteristics of the device are poor, stable operation may not be possible even if an internal accident occurs.

Conventional voltage relay devices are configured to receive input through a circuit that uses saturation characteristics, so the saturation voltage for the voltage relay is not set in consideration of the saturation phenomenon of saturable reactors and current transformers. There was a drawback that it would not work reliably without it.

This invention was made for the purpose of eliminating the drawbacks of the conventional ones as described above, and by providing a second transformer that utilizes the current flowing through the saturable reactor, the current can be continued regardless of the setting of the saturation voltage. Provided is a voltage relay device that can obtain a controlled operation input.

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 2, 11 is 1 of the first transformer 8.
The second transformer, 12, connected in series with the saturable reactor 6 between its secondary terminals is a normally open contact that closes when the voltage relay 9 is activated.

Next, the operation of the embodiment will be explained. The device is the same as the conventional device until the busbar internal fault F ₂ occurs and the voltage relay 9 operates, but once the voltage relay 9 operates, the normally open contact 12 is closed and the voltage relay 9 is connected to the second transformer. The applied voltage can be obtained via 11. In other words, when the voltage V ₁ disappears due to the saturation phenomenon of the saturable reactor 6 or the current transformers 4 and 5, the second transformer 11 supplies an output to the voltage relay 9 due to the current I ₂ flowing through the saturable reactor 6. , the operating input is continuously applied to the voltage relay 9. Also, the second transformer 1
The secondary voltage of 1 is not applied because the normally open contact 12 is open unless the voltage relay 9 operates, so it is not affected by external faults _F1, etc., and furthermore, it is caused by the fault current _I1 caused by internal fault _F2 . It is assumed that the input impedance of the second transformer ₁₁ is sufficiently smaller than that of the saturable reactor 6 so that most of the voltage V 1 is applied to the saturable reactor 6 . Here, the operation when the accident _F1 occurs outside the busbar is the same as that of the conventional device.

In the above embodiment, the input to the second transformer 11 is only the current flowing through the saturable reactor 6, but it may be a combination of the current flowing through the saturable reactor and the current flowing through the nonlinear resistance element 7.

As described above, according to the present invention, when the voltage relay operates, the output of the second transformer connected in series with the saturable reactor is supplied to the voltage relay. This has the effect of providing a voltage relay device that can reliably obtain operational input at certain times.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a conventional voltage relay device installed in a power system, and FIG. 2 is a block diagram of an embodiment of the voltage relay device according to the present invention installed in a power system. In the figure, 6...saturable reactor, 7...
Nonlinear resistance element, 8...first transformer, 9...voltage relay, 10...power supply, 11...second transformer, 12...normally open contact. In addition, I ₁ in the figure is the fault current due to an accident in the protected area, and V ₁ is the fault current I ₁
The voltage drop I ₂ generated by is the load current of the saturable reactor 6 that flows when the voltage V ₁ reaches the saturation voltage. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] 1. A saturable reactor and a second transformer are connected in series between the primary side terminals of a first transformer that supplies input voltage to a voltage relay, and when the voltage relay operates, the second transformer A voltage relay device characterized in that the output of a transformer is supplied to the voltage relay.