JP2602468B2 - Method and apparatus for preventing malfunction of ground fault overcurrent detector upon detection of ground fault in underground transmission line - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ground fault overcurrent detector for detecting a ground fault in an underground transmission line such as a power cable.
The present invention relates to an operation prevention method and an apparatus therefor.

[0002]

2. Description of the Related Art In order to quickly detect a failure point in an underground transmission line, an underground transmission line is detected by detecting a ground fault current flowing at the time of failure in each section of the underground transmission line divided into several sections. Detecting the failure of the system has been performed.

At present, as a means for detecting the electric current, a simple and inexpensive general detection method is to install current transformers at both ends of each section of the underground transmission line and to control the output of the current transformer. A current differential method has been put to practical use in which a current is sent by a feeder and a display line and a difference current between outputs of both current transformers is detected by a detector.

Further, as a method having high reliability and a large number of use results, in a large current region in which the current transformer is saturated and the characteristics are deteriorated, a suppressing force is applied to the operating force and the detector malfunctions. A pilot wire relay system having a ratio differential characteristic to prevent the occurrence of the above problem has been put into practical use, and is currently used in transmission lines of relatively high importance.

[0005]

However, the most simple and inexpensive current differential method for detecting a ground fault current in a high-resistance grounding system is an inexpensive current differential method, in which a large current such as at the time of out-of-phase ground fault has passed. In this case, a malfunction may occur. In other words, the reliability of the current differential method depends on the length of the display line and the characteristics of the current transformer, and particularly, the large current that occurs when out-of-phase ground faults over two circuits other than underground transmission lines are affected. When passing through the current transformer, the current transformer causes magnetic saturation, the output characteristics of both current transformers deteriorate, and a difference current is generated between both current transformers, and when this current exceeds the operating value of the detector, There was a disadvantage that the detector malfunctioned.

On the other hand, in the pilot wire relay system having high reliability, it is necessary to predict the difference current generation amount due to the characteristic difference between the two current transformers and set the suppression amount. When the primary rated current is small (especially several hundreds). In the case of region A), setting the suppression amount was difficult. When this pilot wire relay method is used for a high-resistance grounding system, the ground fault current is smaller than the short-circuit fault current. In many cases, two or more pairs (four cores) of wires are required, and the cost per line has been expensive. The total installation cost per line is about 5 to 10 times as high as that of the current differential system, and it is not economically possible to apply it to all underground transmission lines.

[0007]

SUMMARY OF THE INVENTION In view of the above situation, according to the present invention, current transformers are installed at both ends of each section of an underground transmission line, and outputs of both current transformers are sent to a detector section. Detects the difference current between the outputs of the two current transformers, and detects an overcurrent on the primary side of the transformer installed in the detector that receives the output from the two current transformers in order to detect a ground fault in the underground transmission line. A ground fault overcurrent detector and a contact point of an overcurrent detector that does not supply current to the ground fault overcurrent detector when the overcurrent detector operates, on the secondary side of the transformer. Activate an overcurrent detector to prevent the operation of the ground fault overcurrent detector when a large current passes due to an accident outside the middle power transmission line section. A method for preventing malfunction of a current detector, and disposing at each end of a predetermined section of an underground transmission line, Two current transformers that take in a ground fault current generated by a ground fault, a transformer arranged in a detector unit for detecting an output difference current sent from the two current transformers, and a transformer arranged on the primary side of the transformer. A current detector, a ground fault overcurrent detector disposed on the secondary side of the transformer, and a contact of an overcurrent detector that does not supply current to the ground fault overcurrent detector when the overcurrent detector operates. A feature is a malfunction prevention device of a ground fault overcurrent detector when a ground fault accident of an underground transmission line is detected.

[0008]

In the present invention, current transformers are installed at both ends of each section of the underground transmission line, the outputs of both current transformers are sent to the detector section, and the difference current between the outputs of both current transformers is detected. In addition to using the most inexpensive current differential method for detecting a ground fault as a basic principle, it is possible to detect a ground fault in an underground transmission line, and to prevent a malfunction that occurs when a large current passes, which is a drawback of this method.

That is, an overcurrent detector is disposed on the primary side of the transformer disposed in the detector section, and a contact of the overcurrent detector and a ground fault overcurrent detector are disposed on the secondary side of the transformer. By doing so, when a large current passes due to an accident outside the underground transmission line section, the overcurrent detector and its contacts are activated to prevent the operation of the ground fault overcurrent detector, thereby preventing malfunction. .

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the illustrated embodiment. In FIG., A, B is the underground transmission lines as an example the transmission mode by two lines, CT ₁ to CT ₆ disposed in underground transmission lines A, both ends of each section of B (3 phase feeding electric wires) a primary through-type current transformer which is, usually no current flows, the transmission line a, when the ground fault occurs in a part of the B, the current on the secondary side of the current transformer CT ₁ to CT ₆ Is flowing. Incidentally, the rated primary current of the primary through-type current transformer CT ₁ to CT ₆ is a larger value than the value of the maximum ground fault current.

On the primary through type current transformers CT _{4 to} CT ₆ ,
Tap Through disposed to the communication line C the Okuryou device portion D having a transformer TT ₂ is adapted to transmit to the detector unit E of the primary through-type current transformer CT ₁ to CT ₃ side. The feeder unit D and the detector unit E do not require a special external power supply, and the ground fault current operates each unit as a power supply.

[0012] In the detector unit E is ground fault current is input over-current detector via (overcurrent detection relay) OCR ₁ ~OCR ₃ to the tap transformer TT _1, tapped transformer TT
The output current of ₁ is input to the differential transformer DT together with the output current of the meter unit D. This again, the order Okuryou device unit output current from D is inputted to a reverse phase, the primary through-type current transformer CT ₁ to CT ₃ side and the primary through-type current transformer CT ₄ to CT ₆ side If there is a current difference between the differential transformer DT, an output current will be generated in the differential transformer DT. If this output current is equal to or greater than the ground fault current set value (for example, 2 A), the ground fault current detector (ground fault current detection relay) OCGR operates, the output contact G closes, and the failure indicator 30F operates.

On the secondary side of the differential transformer DT, contacts of overcurrent detectors OCR _{1 to} OCR ₃ are arranged in parallel.
When said overcurrent detector OCR ₁ ~OCR ₃ is actuated, the contact is actuated, the operation of ground fault current detector OCGR is prevented. Incidentally, the over-current detector OCR ₁ ~OC
Since the operation of the R ₃ is set so as to operate at least twice the value of the rated secondary output current of the primary through-type current transformer CT ₁ to CT _3, so as not to work with a value of approximately ground fault current Has become.

[0014] Therefore, when a ground fault in the underground transmission lines (position of F ₁₎ occurs, the ground fault current i ₁ flows, the output current is generated in the primary through-type current transformer CT ₁ to CT ₃ , the output current to the primary through-type current transformer CT ₄ to CT ₆ does not occur, only the output current from the tapped transformer TT ₁ is inputted to the differential transformer DT, caused the output current of the differential transformer DT ground The current detector OCGR and the failure indicator 30F operate to display a ground fault of the underground transmission line. In this case, the overcurrent detector OCR ₁ ~OCR ₃ because it does not work with a value of approximately a ground fault current, the overcurrent detector OC
Does not operate in the ground fault current detector OCGR by contact of R ₁ ~OCR ₃ is locked.

Next, a failure outside the underground transmission line (F ₂
When the position of the) occurs, the flow ground fault current i _2, respectively output current is generated in the primary through-type current transformer CT ₁ to CT _6. This output current passes through the respective tap transformers TT ₁ and TT ₂ and is connected to the primary side of the differential transformer DT so as to flow in opposite phase. Does not occur, and the ground fault current detector OCGR, the output contact G, and the fault indicator 30F do not operate.

Next, when the hetero-phase ground fault (the position of the F ₃₎ occurs, a large current i ₃ flows equivalent to short-circuit current region, the primary side of the primary through-type current transformer CT ₁ to CT ₆ , A large current flows. The primary feedthrough type current transformers CT _{1 to} CT ₆ cause magnetic saturation and often cause an error in the output current, and a difference current occurs in the secondary output current of the differential transformer DT,
The ground fault current detector OCGR may malfunction. In this case, since the overcurrent detector OCR ₁ ~OCR ₃ operates, and short-circuited by operation of the contact of the overcurrent detector OCR ₁ ~OCR ₃ At the same time, preventing the malfunction of the ground fault current detector OCGR it can. Here, the overcurrent detector OC
Before R ₁ ~OCR ₃ is operated, ground fault current detector OCG
Overcurrent detectors OCR _{1 to} OCR ₃ so that R does not operate
Are timed so that they operate in less than half the operating time of the ground fault current detector OCGR.

Further, when the phase short fault (position of F ₄₎ occurs also through the i ₄ becomes large short circuit current primary through type current transformer CT ₁ to CT _6, primary through type current transformer CT the output error of ₁ to CT _6, the difference current is generated in the output of the differential transformer DT, but would cause malfunction of the ground fault current detector OCGR, this case overcurrent detector OCR
_{1 to} OCR ₃ are activated, the input of the ground fault current detector OCGR is short-circuited, and the ground fault current detector OCGR and the fault display 30F
Does not malfunction.

In the above description, an example in which the illustrated current transformer is used as the current transformer has been described. However, a zero-phase current transformer can also be used. Further, the secondary side of the tapped transformer TT _1, if it is connected to the output current from the detector unit E and the output current from the Okuryou device portion D are opposite phases, the differential transformer DT is omitted It is also possible.

Among the underground transmission line failures, short-circuit failures are very unlikely to occur, so all occurrences of short-circuit failures are treated as failures outside the underground transmission line, Regarding detection, section detection by the current differential method is not required. In the large current region where the current differential detector malfunctions, all overcurrent detectors are activated and if the operation of the current differential detector is locked, this method as a whole,
A highly reliable detector that can reliably detect only a ground fault current flowing when a ground fault occurs in an underground transmission line.

[0020]

As is apparent from the above description, according to the present invention, each current transformer is installed at both ends of each section of the underground transmission line, and the outputs of both current transformers are detected by the detector section. To detect the difference current between the outputs of both current transformers. Malfunction during passage can be prevented, and it can be installed at a total cost of about twice as much as the conventional current differential method and about 1/3 to 1/5 as compared with the pilot wire relay method. Thus, it is possible to obtain an excellent operational effect in practical use.

[Brief description of the drawings]

Ground fault detection Tokinio of underground transmission lines according to the invention, FIG
1 is a block diagram showing an embodiment of a device for preventing a malfunction of a ground fault overcurrent detector according to the present invention.

[Explanation of symbols]

A, B underground transmission lines C communication lines D Okuryou unit section E detector portion CT ₁ to CT ₆ primary through type current transformer OCR ₁ ~OCR ₃ overcurrent detector TT _1, TT _2-tapped transformer DT differential transformer OCGR Ground fault current detector 30F Fault indicator G output contact

Claims (2)

(57) [Claims] 1. A current transformer is installed at both ends of each section of an underground power transmission line, outputs of both current transformers are sent to a detector section, and a difference current between outputs of both current transformers is detected. To detect a ground fault in an underground transmission line, an overcurrent detector is placed on the primary side of the transformer installed in the detector that receives output from both current transformers, and a ground fault is detected on the secondary side of the transformer. A current detector and a contact point of an overcurrent detector that does not flow a current to the ground fault overcurrent detector when the overcurrent detector operates are arranged, and a large current has passed in an accident outside the underground transmission line section. A method for preventing a malfunction of a ground fault overcurrent detector upon detection of a ground fault accident of an underground transmission line, wherein the operation of the ground fault overcurrent detector is sometimes prevented by operating the overcurrent detector. 2. Two current transformers arranged at both ends of each underground transmission line for each predetermined section to take in a ground fault current generated by a ground fault in the transmission line, and an output transmitted from both current transformers. A transformer disposed in a detector for detecting a difference current, an overcurrent detector disposed on a primary side of the transformer, a ground fault overcurrent detector disposed on a secondary side of the transformer, and the overcurrent detector operate. And a contact point of an overcurrent detector that does not allow a current to flow to the ground fault overcurrent detector when the ground fault has occurred.