JPH02168807A - Automatic switchgear provided with overcurrent opening preventer - Google Patents

Abstract

PURPOSE:To prevent automatic opening of a switchgear having no interruption capacity due to voltage drop by providing the power source for a control circuit from a bus through which shortcircuit current flows. CONSTITUTION:Upon occurrence of shortcircuit fault in a distribution line S, voltage between the terminals 5a, 5b drops to cause dorppage of the output from a rectifying circuit 4 and a relay 12 starts to turn OFF. At this time, current induced by the shortcircuit current flows through a bushing current transformer BDT to excite the relay 12 through a current transformer CT and a rectifier 19 so as to keep ON state of the relay 12 continuously, while simultaneously a throw-in coil 7 is excited through a rectifier 18 thus keeping ON state of a main electrode 2. In case of small shortcircuit current, small current is induced in the current transformer CT and the relay 12 is de-energized to close the switch 20, while current induced in the bushing current transformer BCT is shortcircuitted through the switch 20 to de-energize the throw-in coil 7 thus opening the main electrode 2.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a constantly excited voltageless opening type automatic switch installed in a power distribution line, and specifically relates to an automatic switch equipped with a device for preventing opening due to overcurrent. be.

[Prior Art] Conventionally, as shown in FIG. 3, an automatic switch 30 of a constantly energized voltageless open type is installed in each predetermined section of a power distribution line S. This automatic switch 30 includes a main electrode 31 installed in each phase U, V, and W of the distribution line S, and a closing coil 33 and a holding coil 32 that close and hold the main electrode 31. The power is supplied from the electric wire S through a pole transformer (not shown) and input terminals 34a and 34b of the rectifier circuit 34.

On the other hand, if a short circuit occurs in the distribution line S, the phase-to-phase voltage due to the short circuit decreases or becomes Ov. Therefore, if the connected phase of the current circuit 34 matches the fault phase, there is a risk that the automatic switch 30 will cut off the power supply and automatically open, and the automatic switch 30 will be affected by the short circuit current and will not have the breaking ability. Main electrode 31
It is necessary to prevent the opening operation. Therefore, the distribution line S
Each phase U.

Of V and W (J phase d-3 and W phase, bushing current transformers BCT are installed respectively. This bushing current transformer F3 CT generates an induced current due to short circuit current. While the short circuit current continues to flow (lJ), the induced current is rectified by Jζ in the rectifier circuit 34, and further the induced current is shunted by the resistor 35, and the closing coil 33 is excited via the diode 36. Therefore, an opening prevention device for preventing the main electrode 31 from opening has been proposed.

[Problems to be Solved by the Invention] However, due to the current capacity of the automatic switch 30, the reaction forces of the springs, buffers, etc. of the mechanical drawing part a'3 and the electrode part (not shown) are not constant, so the load on the closing coil 33 is different. resistance 35
Not only is there the problem of having to adjust the current using the resistor 35, but also the current adjustment using the resistor 35
Reliably securing the minimum holding current of the coil 33 is difficult for humans.

SUMMARY OF THE INVENTION An object of the present invention is to provide an overcurrent-induced opening prevention device (=J- automatic switch) that can cause a holding current to flow through the closing coil regardless of the load on the closing coil.

1. Means for Solving the Problems] In order to achieve the above object, the invention of the present application includes a power supply circuit, and a closing coil d5 and a holding coil that close and hold the door opening/closing part that is supplied with power from the power supply circuit. A first relay circuit connected in parallel to the closing coil of the drive circuit;
a first detection circuit that detects an overcurrent in the distribution line and is connected to the closing coil and energizes the closing coil when an overcurrent is detected; and a first detection circuit that detects a normal current value;
a second detection circuit that drives the first relay circuit; and a second detection circuit that is connected in parallel to the first detection circuit, and is configured to excite and drive the input coil of the first detection circuit under the control of the first relay circuit. The gist is that the system is equipped with a switching device that disables the system.

1 Effect 1 Therefore, when an overcurrent flows through the distribution line, no current signal is supplied to the drive circuit, but the first
The closing coil is energized by the detection signal of the detection circuit to keep the automatic switch from opening. Then, when the overcurrent becomes smaller and becomes lower than the normal current value, the detection signal of the first detection circuit becomes smaller accordingly. Part 1 = Me,
A switching device connected in parallel to the first detection circuit disables drive excitation based on the second detection output, demagnetizes the closing coil and the holding coil, and opens the automatic switch.

[Example] Hereinafter, an example embodying the present invention will be described based on the drawings.

FIG. 1 shows an internal connection diagram of an automatic switch 1 installed in each distribution line S section.

The automatic switch 1 of the always-energized voltageless open type is composed of a main electrode 2 connected to each phase U, V, and W of the distribution line S, a drive circuit 3, and a rectifier circuit 4 as a power supply circuit. Further, power is supplied to the rectifier circuit 4 from the distribution line S via an unillustrated ball transformer to input terminals 5a of the rectifier circuit 4,
5b. The drive circuit 3 includes a series circuit including a holding coil 6 and a closing coil 7.

Furthermore, a first relay circuit 8 is connected in parallel to the rectifier circuit 4 . This first relay circuit 8 is a diode
Consisting of resistors 11 and Y relay 12,
A diode 9, a resistor 11d5, and a Y relay 12 are connected in series in order from the positive potential side of the rectifier circuit 4, and a diode array 1 includes a plurality of diode arrays 1 connected in series.
0 /J< Connected in parallel to Y relay 12.

d3, the diode array 10 is designed to become conductive to protect the Y relay 12 when an overvoltage is applied to the Y relay 12.

A normally open switch 13 that opens and closes under the control of the Y relay 12, an X relay 14, and a microswitch 15 are connected in series and connected in parallel to the closing coil 7. A normally open switch 16 that opens and closes under the control of the X relay 14 connects the closing coil 7 and the switch 1 on the positive terminal side.
It is provided between the positive terminals of 3 and 3. Further, a diode 17 is connected between the positive terminal of the holding coil 6 and the positive terminal of this switch 16. Micro switch 15 is power distribution 4i! Each phase U of iIS.

It is configured to form a circuit when the main electrodes 2 of V and W are closed. Therefore, when the Y relay 12 is energized, the switch 13 is closed and the X relay 14 is energized. As a result, the switch 16 closes and the closing coil 7
The main electrode 2 is inserted by exciting the main electrode 2. Thereafter, the microswitch 15 is circuited to demagnetize the X relay 14. Therefore, the switch 16 is opened and the holding coil 6 is energized via the diode 17 to close and hold the main electrode 2.

A bushing current transformer BCT as a first detection circuit is attached to the U and W phases of the distribution line S, and these are connected in series via a rectifier circuit 18 to the closing coil 7 and a reverse bias voltage 1c. Connected to diode D.

A current transformer CT as a second detection circuit is attached to each of the bushing current transformers BCT, and this current transformer CT is connected to a rectifier circuit 19 and a resistor R. Further, the rectifier circuits 19 are connected in series, and are connected in parallel to the Y relay 12 and the diode 10 of the first relay circuit 8. Then, the current transformer CT selects the Y relay 1 based on the magnitude of the detection signal of the bushing current transformer BCT.
It is designed to drive and control 2.

Further, a switch 20 as a normally closed switch device for short-circuiting both ends of the bushing current transformer BCT and demagnetizing the closing coil 7 is provided between the rectifier circuit 19 of each bushing current transformer BCT and the current transformer C1. The switch 20 is opened and closed under drive control of the Y relay 12.

Next, the operation of the automatic switch opening prevention device configured as described above will be explained.

When the automatic switch 1 is in an open state, when power is supplied from a substation (not shown), the power is supplied from the distribution line S to the input terminals 5a, 5b of the rectifier circuit 4 via a pole mill lance (not shown). The rectifier circuit 4 rectifies the power supply and excites the Y relay 12 of the first relay circuit 8. This results in
Switch 13 is closed and switch 20 of bushing current transformer BCT is opened.

Since the microswitch 15 is closed by the switch 13 being closed, the X relay 14 is energized and the switch 16 is closed. As a result, the closing coil 7 of the drive circuit 3 is energized, and when the main contact 2 is closed, the microswitch 15 is opened, so that the X relay 14 is demagnetized. The switch 16 is then opened. As a result, diode 1
The holding coil 6 and the closing coil 7 are energized via the main electrode 7, and the closing state of the main electrode 2 is maintained.

If a short-circuit accident occurs in the distribution line S in this state and an overcurrent (short-circuit current between phases) flows, the voltage of the rectifier circuit 4 will drop when power is supplied from the phase corresponding to the short-circuit accident.
The automatic switch 1 normally tries to open, but the bushing current transformer BCT reacts to this overcurrent and generates an induced current. Therefore, the current transformer CT provided in the bushing current transformer BCT further generates an induced current by this induced current, and excites the Y relay 12 via the rectifier circuit 19. As a result, the switch 20 remains open and closed, so that the induced current in the bushing current transformer BCT excites the closing coil 7 through the rectifier circuit 18 and maintains the main electrode 2 in the closed state.

When the overcurrent flowing through the distribution line S is small, the induced current generated in the current transformer CT is small. Therefore, the current becomes lower than the minimum holding current of the Y relay 12, the Y relay 12 is demagnetized, and the switch 20 is closed. Therefore, the induced current in the bushing current transformer BCT is short-circuited by the switch 20. Then, since the closing coil 7 is demagnetized, the main electrode 2 is opened.

In this way, when an overcurrent flows in the distribution line S regardless of the load on the closing coil 7, the Y relay 12 is driven by the current transformer CT, and the bushing current transformer BCT is connected to the closing coil 7. Can induce current to flow.

1=10- Furthermore, there is no need to adjust the induced current to excite the closing coil 7, which facilitates manufacturing.

In this embodiment, the opening prevention device j6 of the automatic switch 1 may be configured as shown in FIG.

Incidentally, the same parts as those in the above embodiment are given the same reference numerals, and the description thereof will be omitted.

Similar to the first relay circuit 8, a second relay circuit 22 configured with a Z relay 21 is connected in parallel to the rectifier circuit 4 (), and a current transformer is provided in each of the bushing current transformers BCT. The CT may drive and control the Y relay 12 and the Z relay 21 individually.

Further, in this embodiment, the second detection circuit is provided with respect to the first detection circuit, but it is also possible to cover the distribution line S so that it is placed directly therein.

d5. This invention is not limited to the above-described embodiments, and can be arbitrarily modified without departing from the spirit of the invention.

[Effects of the Invention] As described in detail above, in d3 of the present invention, when an overcurrent flows through the distribution line regardless of the negative state of the input coil, the first relay circuit is driven by the second detection circuit. The detection signal of the first detection circuit can be outputted to the input coil.

As a result, not only can the closing coil be energized to maintain the closing state of the automatic switch, but also the detection signal of the first detection circuit can be output to the closing coil when the distribution line is in a steady state. 5, so there is no problem with the always-energized no-voltage open system of the automatic switch.

[Brief explanation of the drawing]

Figure 1 is the electrical circuit diagram of the automatic switch opening prevention device, Figure 2
The figure is an electric circuit diagram showing a separate opening prevention device for an automatic switch, and FIG. 3 is an electric circuit diagram of a conventional opening prevention device for an automatic switch. DESCRIPTION OF SYMBOLS 1... Automatic switch, 3... Drive circuit, 4... Rectifier circuit as a power supply circuit, 7... Closing coil, 8...
1st relay circuit, 20...Switch as a switch, BCT...Bushing current transformer as a first detection circuit, 0...Current transformer as a second detection circuit, S...
...Distribution line.

Claims (1)

[Scope of Claims] 1. A power supply circuit; and when power is supplied from the power supply circuit, an opening/closing unit is turned on;
In an automatic switch equipped with a closing coil to be held and a drive circuit including the holding coil, a first coil connected in parallel to the closing coil of the drive circuit;
a first detection circuit that detects an overcurrent in the distribution line and is connected to the closing coil and energizes the closing coil when an overcurrent is detected; a second detection circuit that drives the first relay circuit; and a second detection circuit that is connected in parallel to the first detection circuit, and disables the excitation drive for the closing coil of the first detection circuit by controlling the first relay circuit. An automatic switch with an opening prevention device due to overcurrent, characterized in that it is equipped with a switchgear that prevents opening due to overcurrent.