JP2558885B2 - Distribution line ground fault protection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a distribution line for disconnecting a distribution line from a bus of a distribution substation by a ground fault direction relay operated by a zero-phase current of the distribution line when a ground fault occurs. The present invention relates to a ground fault protection device.

[Conventional technology]

FIG. 2 is a block connection diagram showing a conventional distribution line ground fault protection device, in which 1 is a distribution transformer, 2 is a distribution substation busbar connected to this distribution transformer 1, and L ₁ , L
₂ , ... L _n is the distribution line connected to the bus 2 of the distribution substation, CB
₁ , CB ₂ , ... CB _n are circuit breakers connected between each distribution line L ₁ , L ₂ , ... L _n and bus 2 of the distribution substation, ZCT ₁ , ZCT ₂ , ... ZCT _n are zero In the phase current transformer, these detect the zero-phase current of each distribution line L ₁ , L ₂ , ... L _n , and the output is connected to the secondary side of each distribution line ground fault direction relay 67G ₁ , 67G It is designed to input ₂ ... 67G _n . The GPT is a grounding transformer connected to the power distribution bus 2, which includes a ground fault overvoltage relay 64 that operates by detecting a zero-phase voltage generated in the event of a ground fault, and the distribution lines L ₁ , L ₂ ...
The ground fault direction relay 67G ₁ , 67G ₂ , which selects the ground fault direction of L _n
… 67G _n is connected. AND ₁ , AND ₂ , ... AND _n are n AND gates AND, which are ground fault overvoltage relays 6
4 and operating signals Q corresponding to zero-phase voltage to be detected is, local fault direction relay 67G _1, 67G _2, ... operation signal P ₁ of 67G _n, P _2, ... ANDing the P _n. T ₁ , T ₂ , ... T _n are AND gates AND ₁ ,, AND ₂ , ...
Timer T that counts the output time (duration) of AND _n
Then, after a lapse of a predetermined time, a time-up signal, that is, a ground fault detection signal of each distribution line L ₁ , L ₂ , ... L _n is output. The ground fault detection signal is used for breaking the circuit breakers CB ₁ , CB ₂ , ... CB _n . S ₁ , S ₂ , ... S _n are between each distribution line L ₁ , L ₂ , ... L _n ,
A loop switch connected to each of these predetermined sections forms a loop circuit with the bus 2 of the distribution substation when the loop switch is closed. Each distribution line L ₁ , L ₂ , ... L _n is provided with a division switch (not shown) for each predetermined section.

Next, the operation will be described. First, each distribution line L ₁ , L ₂ ,…
When there is no abnormality in any of L _n , electric power is normally supplied to the load connected in each section. On the other hand, when a ground fault occurs at any one of the above-mentioned distribution lines L ₁ , L ₂ , ... L _n , for example, at the failure point F ₁ of the distribution line L ₂ , this failure point F ₁ , ground and zero-phase current transformer Zero-phase current I ₀₂ flows through ZCT ₂ . Therefore, the zero-phase secondary current flows through the ground fault direction relay 67G ₂ connected to the secondary side of the zero-phase current transformer ZCT ₂ , and the grounding transformer GPT
The zero-phase voltage is input via the and operates. On the other hand, at this time, the ground fault overvoltage relay 64 detects the zero-phase voltage generated at the time of an accident, and outputs the operation signal Q corresponding to this zero-phase voltage to the AND gate AND ₂ together with the operation signal P ₂ of the ground fault direction relay 67G _2. input. Therefore, the AND gate AND ₂ outputs the ground fault detection signal and opens the circuit breaker CB ₂ after a predetermined time. In addition, the protection operation for the ground fault caused in the other distribution lines L ₁ , L ₃ , ... L _n is performed in the same manner as above.

By the way, there may be a case where it is necessary to carry out the maintenance and inspection of each of the above-mentioned distribution lines L ₁ , L ₂ , ... L _n , for example, a distribution line between the breaker CB ₂ and the loop switch S _1. when the inspection of L ₂ opens the breaker CB ₂ closes the loop switch S _1, after opening of the circuit breaker CB _2, it continues breaker CB on various loads connected to the distribution line L ₂ Power can be supplied through ₁ .

[Problems to be Solved by the Invention]

Since the conventional distribution line ground fault protection device is configured as described above, when the loop switch S ₁ is closed in the above maintenance and inspection activities, the two distribution lines L ₁ , L ₂ A zero-phase circulating current due to unbalance of distribution line twisting flows in the loop circuit connecting the bus 2 of the distribution substation and the loop switch S ₁ as shown by the arrow. In this case, since zero-phase voltage is not normally generated, zero-phase current transformers ZCT ₁ and ZCT
Connected ground direction relay 67G _{2 1,} none of 67G ₂ malfunction not be.

However, during the period when the loop switch is closed,
If a ground fault occurs at fault point F ₂ on another distribution line L _n ,
Since a zero-phase voltage is generated in the grounding transformer GPT, this zero-phase voltage and the above-mentioned zero-phase circulating current cause any of the ground fault direction relays 67G ₁ and 67G ₂ having a phase characteristic as shown in FIG. Malfunctions and outputs the operation signal Q and P ₁ or P ₂ to the AND gate AND ₁ or AND ₂ . Therefore, the circuit breaker CB ₁ ,
Since CB ₂ is not a self-line accident, one of them was opened even though it was not necessary to open it, and the power supply capacity of the distribution line declined,
There was a problem that the service on the power supply was lowered.

The present invention has been made in view of the above-mentioned conventional circumstances, and a ground fault protection that protects a power distribution system by tripping a circuit breaker at the time of a ground fault by a ground fault direction relay operated by a zero-phase current. In the equipment, it is possible to automatically detect that the zero-phase current of each distribution line is based on the above loop circuit formation at the distribution line monitoring station such as the substation side, and to take necessary measures promptly. The purpose is to

[Means for solving the problem]

The distribution line ground fault protection device according to the present invention is provided with a zero-phase current detector corresponding to each of a plurality of distribution lines connected to the bus bar of the distribution substation through a breaker, respectively. In the case where the corresponding breaker is tripped by detecting the zero-phase current flowing through the corresponding distribution line and receiving the output of this zero-phase current detector to activate the ground fault direction relay at the time of a ground fault. By connecting a loop switch between the predetermined distribution lines of the wire, forming a loop circuit with the bus bar when closing this, and providing a sample hold circuit corresponding to each zero-phase current detector, the corresponding zero-phase The output of the current detector is sampled, the zero-phase current information obtained by this sampling is held, the held zero-phase current information is selected and output by the multiplexer, and based on this output result. The zero-phase current presence determining means,
The presence or absence of the relationship that the absolute value of the zero-phase current of each distribution line is the same and the phase of the zero-phase current is 180 ° is detected, and the detection result is readablely stored and stored in a loop circuit with a zero-phase circulating current. The name of the distribution line is notified using a notification means.

[Operation] The zero-phase current presence / absence determining means according to the present invention has the same absolute value of the zero-phase current and a phase of 180 ° based on the voltage conversion value of the zero-phase current for each distribution line output from the multiplexer. The presence / absence of the relation is detected, and the name of the distribution line having the loop circuit can be notified by the notification means.

Example of Invention

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, 67L is a zero-phase circulating current detection device provided at the substation side together with the distribution transformer 1 or the like, or at a so-called distribution line monitoring station such as a sales office, Tr ₁ , Tr ₂ , ... Tr _n are each Zero-phase current detector (hereinafter referred to as zero-phase current transformer) ZCT ₁ , ZCT ₂ , ...
The zero-phase current output from ZCT _{n is} output to each other-direction relay 67G ₁ , 67G ₂ ,
… Input transformer for converting to 67G _n input, R ₁ , R ₂ ,… R _n is a resistor for current / voltage conversion placed in parallel on the secondary side of the input transformers Tr ₁ , Tr ₂ and Tr ₃ , SH ₁ , SH ₂ , ... SH _n are sample and hold circuits, MPX is a multiplexer that selects and inputs each output of sample and hold circuits SH ₁ , SH ₂ , ... SH _n , A / D is digital output of multiplexer MPX Analog-to-digital converter for conversion, ROM is read-only memory for storing operation judgment program, RAM ₁ and RAM ₂ are random access memories for storing various input data, D / O is digital output circuit, CPU is zero phase A microprocessor as a current presence / absence determining means calculates the presence / absence of a loop circuit, the magnitude of zero-phase current, the number of times of loop circuit formation, the date and time of loop circuit formation, time, time zone, and the like according to the operation determination program, and the zero-phase. Due to ground fault current Or to estimate the malfunction of the ground fault direction relay.

Further, ST is an informing means provided in the parent station of the business office independent of the substation, and this informing means ST and the presence / absence data of the loop circuit are read from the random access memory RAM ₂ and the informing signal with the loop circuit is present. Notification circuit IN that outputs
When each distribution line _{L 1, L 2, ... L} n are provided corresponding to, alarm C ₁ such as a lamp or a buzzer for lighting by receiving the notification signal, C
₂ , ... C _n .

The other parts that are the same as those shown in FIG. 2 are designated by the same reference numerals, and the duplicate description thereof will be omitted.

Next, the operation will be described. First, each distribution line L ₁ , L ₂ ,…
In the case where all L _n are normal, or when a ground fault occurs with no loop circuit formed and the breakers CB ₁ , CB ₂ , ... CB _n of the distribution line affected by this fault open The operation is similar to the conventional one. On the other hand, the distribution line L _1, L _2, as described above, when carrying out the inspection of ... L _n only a section, the loop switch
Any of S ₁ , S ₂ , ..., S _n is closed to form the loop circuit as described above. For example, when the loop switch S ₁ is closed, a zero-phase circulating current flows in the loop circuit formed by the loop switch S ₁ , the distribution lines L ₁ and L ₂ and the distribution bus 2. On the other hand, the zero-phase currents ZCT ₁ and ZCT ₂ are supplied with zero-phase currents whose phases are different from each other by 180 ° and are input to the input transformers Tr ₁ and Tr ₂ and the ground fault direction relays 67G ₁ and 67G ₂ . The zero-phase current input to the input transformers Tr ₁ and Tr ₂ is the resistors R ₁ and R ₂
The voltage-converted zero-phase current information is sampled by the sample-hold circuits SH ₁ and SH ₂ at intervals of, for example, 30 ° and temporarily held, and then sequentially held by the multiplexer MPX. Taken out. The zero-phase current data extracted in this way is converted into digital data by the analog / digital converter A / D,
Each of these data is temporarily stored in the random access memory RAM ₁ . The microprocessor CPU also follows the zero-phase current I according to the program stored in the read-only memory ROM.
_The absolute value and phase of ₀₁ and I ₀₂ are calculated, and it is determined whether the absolute values are equal and the phase is 180 °, that is, whether there is a loop circuit. Is stored in random access memory RAM ₂ . It should be noted that, as the stored data, it is possible to store the on / off state of the circuit breaker, construction information, and the like, and the determination result is the distribution lines L ₁ , L ₂ , ... L _n forming the loop circuit. Each is input to the notification means ST via the digital output circuit D / O. In the notification means ST, a notification signal is output to an output line corresponding to a distribution line having a loop circuit in the notification circuit IN to operate any of the notification devices C ₁ , C ₂ , ... C _n such as a lamp or a buzzer. . Therefore, the parent office of the sales office can easily confirm that there is a loop circuit, check the loop wiring, change the loop wiring, and distribute the loop circuit side distribution lines L ₁ , L ₂ ,
It is possible to prevent the circuit breaker from being opened in any of L _n , and further to predict the malfunction of the ground fault direction relays 67G ₁ , 67G ₂ , ... 67G _n due to the zero-phase circulating current.

Incidentally, in the above-mentioned embodiment, the one that operates the buzzer or the lamp is shown as the notification means ST, but using a CRT display or the like, for example, a wording such as "generation of zero-phase circulating current between distribution lines L ₁ and L ₂ " May be displayed on the screen, and the same effect as that of the above-described embodiment can be obtained.

In addition, the random access memory RAM ₂ has zero phase current.
By storing the size of I _0, the distribution line of the accident, the date and time, this can be read out as necessary. Furthermore, in the zero-phase circulating current detection device 67L, along with the contents of the random access memories RAM ₁ and RAM ₂ ,
If the breaker is turned on and off, the classification switch is turned on and off, and construction information is stored and all of these contents can be monitored, the practicality will be further enhanced.

〔The invention's effect〕

As described above, according to the present invention, the zero-phase current detector is provided corresponding to each of the plurality of distribution lines connected to the busbars of the distribution substation through the circuit breakers, respectively. Detects the zero-phase current flowing through the wire, receives the output of this zero-phase current detector, and activates the ground fault direction relay at the time of a ground fault to trip the corresponding breaker. By connecting a loop switch between the specified distribution lines, forming a loop circuit with the above bus when closing it, and providing a sample hold circuit corresponding to each zero-phase current detector, the corresponding zero-phase current detection The output of the converter is sampled, the zero-phase current information obtained by this sampling is held, and the held zero-phase current information is selected and output by a multiplexer. The presence / absence determination means detects whether or not there is a relationship in which the absolute values of the zero-phase currents of the distribution lines are equal and the phase of the zero-phase currents is 180 °, and the detection results are stored in a readable manner and the detection results are stored. Since the notification means is used to notify, the name of the distribution line with the loop circuit can be clearly displayed, and an instruction to inspect the loop circuit (wiring) or change the wiring can be issued to extend the power outage range. In addition to the prevention, it is possible to predict a malfunction of the ground fault direction relay due to the zero-phase circulating current of the loop circuit in the case of a ground fault of another distribution line.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block connection diagram showing a distribution line ground fault protection device according to an embodiment of the present invention, FIG. 2 is a block connection diagram showing a conventional distribution line ground fault protection device, and FIG. The figure is a graph showing the phase characteristics of the ground fault direction relay. 2 is the bus of the distribution substation, CB ₁ , CB ₂ , ... CB _n are circuit breakers, L
₁ , L ₂ , ... L _n is a distribution line, 67G ₁ , 67G ₂ , ... 67G _n is a ground fault direction relay, ZCT ₁ , ZCT ₂ , ... ZCT _n is a zero phase current detector, S ₁ , S ₂ , ... S _n is a loop switch, R ₁ , R ₂ , ... R _n is a resistor, SH ₁ , SH ₂ , ... SH _n is a sample and hold circuit, MPX is a multiplexer, CPU is a zero-phase current presence / absence determining means (microprocessor) , ST is a notification means. In the drawings, the same reference numerals indicate the same or corresponding parts.

Front Page Continuation (72) Inventor Koichiro Oyabu 2-47 Shiobara, Minami-ku, Fukuoka City, Fukuoka Prefecture Kyushu Electric Power Co., Inc. Electric Power Laboratory (72) Inventor Toshinobu Ebisaka Wadazaki, Hyogo-ku, Kobe-shi, Hyogo 1-2, Machi Mitsubishi Electric Co., Ltd. Control Works (72) Inventor Keiji Isahaya 1-2-1, Wadazakicho, Hyogo-ku, Kobe Hyogo Prefecture Mitsubishi Electric Co., Ltd. (72) Inventor Akira Kaneda 1-2-1 Wadazaki-cho, Hyogo-ku, Kobe-shi, Hyogo Mitsubishi Electric Corporation Control Works (56) References JP-A-62-110432 (JP, A) JP-A-58-46832 (JP, A)

Claims (1)

(57) [Claims] 1. A plurality of distribution lines each connected to a bus of a distribution substation through a circuit breaker, and a zero-phase current flowing through each corresponding distribution line is detected. Zero-phase current detector, the output of this zero-phase current detector is supplied, ground fault direction relay that operates at the time of a ground fault and trips the corresponding breaker, and is connected between each distribution line,
A plurality of loop switches that form a loop circuit together with the bus of the distribution substation at the time of closing, and are provided corresponding to each of the zero-phase current detectors, sampling the output of the corresponding zero-phase current detector, A sample-hold circuit that holds the zero-phase current information obtained by this sampling, a multiplexer that selectively outputs the zero-phase current information held by each sample-hold circuit, and based on the output of this multiplexer, The absolute values of zero-phase current are equal,
A distribution line having zero-phase current presence / absence determining means for detecting the presence / absence of a relationship in which the phase of the zero-phase current is 180 °, and a zero-phase current as a detection output of the zero-phase current presence / absence determining means and a corresponding loop circuit. A distribution line ground fault protection device comprising: a memory for storing a name; and a notifying means for notifying a wiring name of the loop circuit read from the memory.