JPH04255420A - Protective system for distribution line - Google Patents

Abstract

PURPOSE:To provide a protective system for distribution line which can protect even a short circuit fault reliably, causes no trouble in the operation of system even upon breakdown of a sensor and in which external noise causes no erroneous function of a fault judging circuit. CONSTITUTION:A photo current sensor 4 for detecting fault current is mounted on a distribution line 2 and when a fault current is detected, a thyristor unit 3 functions to protect distribution line. The photo current sensor 4 is provided with an output regulating circuit for regulating the intensity of light so that the output signal keeps a reference level.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protection system for power distribution lines for protecting power distribution lines from fault currents caused by short circuits or short-to-ground faults.

0002

[Prior Art] Circuit breakers and circuit breaker OCRs (overcurrent relays) have traditionally been installed in the premises of distribution substations to protect the system in the event of a short-circuit accident or the like occurring on distribution lines. ing. However, since the OCR of this circuit breaker has a slow operating characteristic so that it operates after the OCR of the customer circuit breaker has operated, the distribution line may be disconnected due to fault current while this circuit breaker is operating, resulting in a long There was a problem in that it led to power outage accidents that lasted for hours. In addition, since current transformers were used as sensors for fault current detection, there is a possibility that the fault judgment circuit may malfunction due to external electrical noise, and the current transformer's insulation may deteriorate or break down, causing system problems. There were problems such as making it impossible to operate.

0003

[Problems to be Solved by the Invention] The present invention solves the conventional problems as described above, and even in the unlikely event that insulation breakdown occurs in the sensor, it does not hinder the operation of the system, and it is also possible to This system was developed to provide a protection system for power distribution lines that does not cause fault detection circuits to malfunction due to noise, and that can reliably protect power distribution lines from arcing caused by fault current in the event of an accident. It is.

0004

[Means for Solving the Problems] The present invention, which has been made to solve the above problems, provides a photocurrent sensor for fault current detection attached to a distribution line, and a photocurrent sensor for detecting a fault current that is installed on a distribution line. The photocurrent sensor consists of a thyristor device that is activated to protect the power distribution line, and a photoelectric converter that adjusts the intensity of the light beam input to the photocurrent sensor so that its output signal remains at a reference level. The invention is characterized in that it is provided by being coupled by. The present invention will be explained in more detail below with reference to illustrated embodiments.

[0005]

[Example] In Fig. 1, 1 is a circuit breaker for a distribution substation;
is the distribution line. In this embodiment, a thyristor device 3 is provided in parallel with the distribution line 2, and when a fault current is detected, the thyristor device 3 is turned on to forcibly short-circuit the distribution line 2 and reduce the system voltage. The arc is extinguished and the distribution line 2 is protected. However, it is also possible to insert a thyristor device 3, which is always on, in series with the distribution line 2 to interrupt the fault current and extinguish the arc.

In the present invention, a photocurrent sensor 4 is attached to the distribution line 2 as a sensor for detecting fault current. As shown in FIG. 2, this photocurrent sensor 4 has a Faraday element 6 inserted into the gap of an iron core 5 surrounding the power distribution line 2, and connects a light beam of constant intensity from a light source 7 of a photoelectric converter to an optical fiber cable. It can be modulated according to the current of the distribution line 2 through the power distribution line 2. Since alternating current is flowing through the power distribution line 2, the output of the photocurrent sensor 4 taken out to the light receiver 8 of the photoelectric converter contains an alternating current component as shown on the right side of FIG.

As shown in FIG. 3, the optical output of the photocurrent sensor 4 is converted into an electrical signal by a phototransistor, which is a receiver 8 of a photoelectric converter, through an optical fiber cable, and a DC component is cut by a coupling capacitor 9. Ru. Thereafter, the voltage is amplified by an amplifier 10, passed through a rectifier circuit 11 and a smoothing circuit 12, and then compared with a reference voltage in a comparison circuit 13 of an accident determination circuit. The comparison circuit 13 determines whether the output of the photocurrent sensor 4 exceeds the set value or not.
The next logic circuit 14 outputs a signal of "0" or "1".The next logic circuit 14 detects an accident when a current exceeding a set value is detected in two or more of the three phases U, V, and W of the three-phase AC. It is determined that this has occurred, and a trigger signal is sent to the thyristor device 3 described above to activate it.

On the other hand, the optical output of the photocurrent sensor 4, which is converted into an electrical signal by the photodetector 8, is compared with a reference voltage by a comparison circuit 15 of the photoelectric converter. Then, a signal is sent to the output adjustment circuit 16 so that the optical output of the photocurrent sensor 4 is always maintained at the reference level, and the intensity of the light beam sent from the light source 7 of the photoelectric converter to the photocurrent sensor 4 is adjusted. In other words, by applying feedback to the output adjustment circuit 16 of the photocurrent sensor 4, control is performed such that the optical output of the photocurrent sensor 4 is always kept constant.

[0009]

[Operation] In the power distribution line protection system of the present invention configured as described above, when the photocurrent sensor 4 attached to the power distribution line 2 detects a fault current, the logic circuit 14 of the fault determination circuit activates the thyristor device 3. A trigger signal is sent to the thyristor device 3 to operate the thyristor device 3 at high speed to short-circuit or cut off the fault current, extinguish the arc, and prevent the distribution line 2 from being damaged or blown out. Furthermore, as mentioned above, the photocurrent sensor 4 is equipped with a photoelectric converter that adjusts the intensity of the light beam input to the photocurrent sensor 4 so that its output signal maintains the reference level, so it can be used for many years. Even if the light source 7 begins to deteriorate due to the above, the photocurrent sensor 4 operates stably and can reliably detect the fault current.

Moreover, in the present invention, since the photocurrent sensor 4 is adopted as a sensor for fault current detection, there is no risk that the fault judgment circuit will malfunction due to the influence of external electrical noise, and its output signal can be Since the optical fiber cable is non-metallic and has excellent insulation, it is taken out to the photoelectric converter side, so even if dielectric breakdown of the photocurrent sensor 4 occurs, there will be no accident. , there is no risk of disrupting the operation of the power distribution system.

[0011]

Effects of the Invention As explained above, since the distribution line protection system of the present invention uses a photocurrent sensor as means for detecting fault current in the distribution line, even if dielectric breakdown of the sensor occurs, the system In addition, the accident determination circuit will not malfunction due to external noise, and the output of the photocurrent sensor can be stabilized to ensure reliable detection accuracy. Moreover, in the event of an accident, by operating the thyristor device at high speed,
It is possible to reliably protect the power distribution line from fault current. Therefore, the present invention eliminates the problems of the conventional technology and greatly contributes to the development of industry.

[Brief explanation of the drawing]

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

FIG. 2 is a block diagram showing a photocurrent sensor according to an embodiment.

FIG. 3 is a block diagram showing the configuration and operation of the photocurrent sensor, photoelectric converter, etc. of the embodiment.

[Explanation of symbols]

2　Power distribution line 3 Thyristor device 4 Photocurrent sensor 7 Light source of photoelectric converter 8 Photoelectric converter receiver 16 Output adjustment circuit

Claims (1)

[Claims] [Claim 1] This photocurrent sensor comprises a photocurrent sensor for fault current detection attached to a distribution line, and a thyristor device that operates when the photocurrent sensor detects a fault current to protect the distribution line. protection of a power distribution line, characterized in that the device is equipped with a photoelectric converter coupled by an optical fiber cable, which adjusts the intensity of the light beam input to the photocurrent sensor so that the output signal thereof remains at a reference level. system.