JP2993769B2 - Distribution line protection system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distribution line protection system for extinguishing an arc discharge generated in a system to protect a line.

[0002]

2. Description of the Related Art As shown in FIG. 1, a substation H supplies power to a three-phase distribution line 2 on which a circuit breaker 1 is installed.
On the secondary side of the circuit breaker 1, a detection unit such as a current transformer 3 or a grounding transformer 4 is provided, and the circuit breaker 1 is controlled by a protection relay 5 that detects a line fault by a detection signal.
The distribution line 2 is a normally closed line switch SW1-SW.
N, and the front of the track is configured to be connectable to a nearby distribution line (not shown).

[0003] However, the conventional distribution line 2 as described above.
If a short circuit accident occurs at the commercial frequency, about 12 cycles (60 Hz) from the occurrence of the line accident to the opening of the circuit breaker 1
System takes about 0.2 seconds). For this reason, if an arc discharge occurs in the line due to an accident current due to a lightning surge or the like, the line equipment may be considerably damaged before the circuit breaker 1 is opened.

[0004]

An object of the present invention is to provide a protection system for a distribution line which can extinguish an arc discharge in the distribution line to reduce damage to the line and suppress the opening of the circuit breaker to reduce the number of power failures. The purpose of this is to provide.

[0005]

In order to achieve the above object, the present invention provides a thyristor type in which a current detecting means is provided on a distribution line, and a branch line of the distribution line is turned off through a switching means for the line. After the switch is connected, it is determined that the signal level from the current detecting means has exceeded a set value, the thyristor switch is turned on, and the on state is maintained for at least 1.5 cycles of the system frequency. In addition, control for returning to the off state is performed again.

[0006]

When the fault current in the line is detected based on the level of the signal from the current detecting means, the thyristor-type switch in the off state shifts to the on state, and at least 1.5% of the system frequency.
After the cycle has elapsed, the switch returns to the off state, so overcurrent in the line flows to the branched line while the thyristor switch is on, and the return to the off state reduces the fault current flowing through the distribution line, resulting in arc discharge. Is extinguished and the track is protected. Further, since the thyristor switch is connected to the distribution line via the opening / closing means, it can be disconnected from the distribution line at any time, and inspection and repair can be easily performed.

[0007]

Embodiments of the present invention will be described below in detail with reference to the drawings. As shown in FIG. 1, current detection means 6 is provided for each phase of the distribution line 2, and its signal line 6a is connected to a determination circuit 8 provided in a thyristor device 7. As the current detecting means 6, a current transformer, an optical sensor for detecting a magnetic field, or the like is used. When an optical sensor is used, an optical fiber cable is used as the signal line 6a, and a means for mutually converting between electric / optical signals such as a light emitting diode (LED) and a photodiode (PD) is provided in the determination circuit 8. Provide.

The judgment circuit 8 is connected via a thyristor control circuit 9 to a thyristor-type switch 10 in an off-state, which is installed with a terminal short-circuited to a branch line 11 from the distribution line 2. The judging circuit 8 receives the signal from the current detecting means 6, judges the magnitude of the overcurrent in the distribution line 2 based on the intensity level, and when the signal exceeds the set level, the thyristor control circuit 9 The thyristor is configured to transmit a start signal.

The thyristor control circuit 9 is operated by a signal from the judgment circuit 8, and is configured to be able to input a control signal to the thyristor switch 10 during a predetermined cycle as shown in FIG. FIG. 2A shows the decay and extinction of the arc current during the transition of the thyristor-type switch 10 from the off state to the on state, and further to the return to the off state, where T ₁ is the arc current generated in the distribution line 2. Is the time from when the thyristor-type switch 10 is activated to when the thyristor-type switch 10 shifts from the off state to the on state. T2 is the time during which the thyristor-type switch 10 is turned on and the arc current in the distribution line ₂ is attenuated. In the present invention, the operation time T ₃ of the thyristor control circuit 9, that is, the thyristor-type switch 1
As shown in FIG. 2 (b), the control time for 0 is T ₃ = T ₂ + α.
Set to. The time T ₅ to pass through the thyristor switch 10 short-circuit current, like T ₅ as shown in FIG. 2 (b)
= A T ₃ + T _4. However T ₄ is less than 0.5 cycles.

The present invention as described above, the control time T ₃ of the thyristor switch 10 by the thyristor control circuit 9 1.
The thyristor device 7 is configured to set the cycle to 5 cycles or more, and to turn on the thyristor type switch 10 installed in the branch line 11 in the off state during this time. In the embodiment of FIG. 2, the operating time is about 1.5 cycles, in which case the arc current through the thyristor switch 10 is two cycles. Further, in the present invention, a normally open protective switch 12, which is a means for opening and closing the electric circuit, is provided on the branch line 11 on the primary side of the thyristor switch 10, and a control device 14, which is separately provided, is installed for controlling the switch. ing.

The protection switch 12 includes a closing coil (CC) 13
and a lock mechanism 13 comprising a trip coil (TC) 13b. The lock mechanism 13 is turned on and off by a control signal from the control device 14. Further, on the secondary side of the protection switch 12, a second current detecting means 15 including a current transformer or the like is provided, and a signal line 15a thereof is connected to the control device 14. Therefore, the electric path of the branch line 11 can be separated from the distribution line 2 by releasing the excitation of the lock mechanism 13 and opening the protection switch 12 in response to a signal from the second current detecting means 15.

Reference numeral 17 denotes a low-voltage line supplied from the distribution line 2 via the transformer 18, and supplies control power to the thyristor device 7 and the control device 14. The control device 14 can be configured to incorporate a power storage device (not shown), receive charging from the low voltage line 17, and display the open / closed state of the protection switch 12 by a lamp or the like. A lightning arrester 19 is provided on the branch line 11.

Next, FIG. 3 shows an example of mounting the apparatus of the present invention.
The distribution line 2 is an insulator 2 erected on the arm 21a of the utility pole 21.
It is supported and installed by No. 2. Branch line 11 is connector 2
3 and the arm 21
a one bushing 2 to the protective switch 12 suspended from
4, is drawn out of the other bushing 25, and is drawn into the thyristor device 7 suspended from the lower arm 21 b by the bushing 26.

Signal line 6a of current detecting means 6 of distribution line 2
Is pulled down along the utility pole 21 and is drawn into the thyristor device 7 from below. Case 12a of protection switch 12
The lock mechanism 13 and the lightning arrester 19 are housed therein. Further, in the protective switch 12, a second current detecting means 15 is provided around the above-mentioned drawer-side bushing 25, and a signal line 15a is connected to the control device 14. Below the thyristor device 7, a control device 1 for the protection switch 2 is provided.
4 is suspended from the lower arm 21c, the low-voltage branch line 17a is drawn in from below, and the connection line 16 is pulled up along the utility pole, and the upper protective switch 1 is mounted.
2 are connected.

The operation of the embodiment constructed as described above is as follows. First, when the current detecting means 6 detects an overcurrent generated in the distribution line 2, the determination circuit 8 of the thyristor device 7 determines that a short circuit accident has occurred in the branch line 11 because the intensity level of the detection signal has exceeded a set value. The thyristor control circuit 9 is operated.

The thyristor control circuit 9 inputs a control signal to the thyristor-type switch 10 for at least 1.5 cycles of the system frequency, and the thyristor-type switch 10 keeps the ON state and the arc flowing from the distribution line 2 to the branch line 11 The current is passed, and the control signal is returned to the ON state again by interruption. Therefore, the fault current in distribution line 2 is
Branch line 11 while thyristor switch 10 is on
In the distribution line 2, the fault current is attenuated, the arc discharge is extinguished, and the line is protected.

According to the present invention, the thyristor switch 10 is turned on as described above, and at least at the system frequency, the thyristor switch 10 is turned on.
After maintaining the ON state for 5 cycles, it returns to the OFF state. Table 1 shows the test results when the time during which the thyristor switch 10 is kept on is changed.
Shown in

[0018]

[Table 1]

As apparent from Table 1, when the thyristor control time was one cycle, the arc discharge was not extinguished and the electric wire was blown. At 1.5 to 5 cycles, the arc discharge was extinguished, and almost no damage to the wire was observed. On the other hand, the activation of the thyristor type switch 10 causes an instantaneous voltage drop in the line, but it was determined that there was no practically harmful effect in 1.5 to 5 cycles. 6
In the case of more than one cycle, the influence of the instantaneous voltage drop is large even if the arc discharge is extinguished, and the circuit breaker of the substation operates in more than 12 cycles, so the inventor has judged that it is practically inappropriate .

Further, when the arc discharge is extinguished in the distribution line 2 by the activation of the thyristor switch 10, the protection relay 5 remains set for a set time even if the detection units 3, 4 of the substation H detect an accident current when an accident occurs. Since the opening of the circuit breaker 1 is stopped until this time, the arc current is extinguished during that time, and the power failure of the distribution line 2 is avoided.

Further, in the embodiment, a normally closed protective switch 12 is installed on the branch line 11 on the primary side of the thyristor type switch 10 and a signal from a second current detecting means 15 provided on the secondary side of the switch is provided by this switch. Since the protection switch 12 can be opened, the thyristor type switch 1 depends on the switching frequency.
If 0 is degraded and remains on even after the control signal is terminated, the protection switch 12 is opened by detecting a no-voltage in the system due to the opening of the circuit breaker 1. When a leakage current flows through the thyristor-type switch 10 in the off state, the control device 14
Controls the lock mechanism 13 to open the protection switch 12. Since the thyristor device 7 is separated from the distribution line 2 in this manner, there is an advantage that the power supply to the system is not hindered, and that the thyristor device 7 can be inspected and repaired as needed to stably maintain the facility. .

[0022]

As described above, the present invention detects the overcurrent of the line, activates the thyristor at the branch point to extinguish the arc discharge of the line, thereby protecting the line of the system,
In addition, it is possible to avoid a power failure and to contribute to a stable power supply.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 2 is a graph showing an operation state of a thyristor.

FIG. 3 is a front view showing an example of a mounting column of the apparatus of the present invention.

[Explanation of symbols]

 2 Distribution line 6 Current detecting means 10 Thyristor type switch 11 Branch line 12 Protection switch as switching means for electric circuit

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-59-220019 (JP, A) JP-A-59-206917 (JP, A) JP-A-59-206916 (JP, A) 130440 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) H02H 7/26 H02H 3/32-3/52 H02H 7/12 H02H 17/725-17/08

Claims (1)

(57) [Claims] A current detecting means is provided in a distribution line, a thyristor-type switch in an off state is connected to a branch line of the distribution line via opening and closing means of the circuit, and a signal level from the current detecting means is set. The power distribution is characterized by determining that the value has been exceeded, shifting the thyristor-type switch to the ON state, maintaining the ON state for at least 1.5 cycles of the system frequency, and then returning to the OFF state again. Track protection system.