JP3591240B2 - Distribution line protection device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a distribution line protection device in a power distribution system that distributes extra high voltage or high voltage power via a distributed transformer.
[0002]
[Prior art]
FIG. 3 is a single-line connection diagram showing a conventional power distribution system that steps down from a voltage of 6.6 kV to a low voltage of 210 V and distributes power. In the figure, reference numeral 1 denotes a first power supply line connected to a substation (not shown), 1A and 1B denote circuit breakers for opening and closing the circuit of the first power supply line 1, and 2 denotes a branch from the first power supply line. 2A is a protection circuit breaker provided at a branch from the first power supply line 1, and 3 is a current flowing through the second power supply line 2. 4 is an overcurrent relay that monitors the presence or absence of an abnormality based on the output from the current transformer 3 and sends an open signal to the protection circuit breaker 2A when an abnormality occurs. 4 is a protection circuit breaker. An instrument transformer for transforming the current flowing through the feeder line into which the power line 2 is inserted and outputting the transformed current to the relay 3, a distribution line 6 connected to the secondary side of the transformer 5, and a feeder 7 for opening and closing the distribution line It is a circuit breaker.
[0003]
In FIG. 3, the transformer 5 is usually 100 kVA, the primary current is about 9 A, and the secondary current is about 270 A. In the system of three transformers 5 shown in FIG. 3, since about 26 A flows through the current transformer 3 for the instrument, the current transformer 3 has a current transformation ratio (input to output ratio) of about 50/5. Is used.
[0004]
[Problems to be solved by the invention]
In a conventional power distribution system using a voltage of 6.6 kV, the current flowing through the second power supply line is relatively large, and can be easily detected by the current transformer 3 for the instrument. It has become necessary to use an extra high voltage of, for example, 22 kV as the power supply voltage, and then reduce the voltage to a low voltage of 210 V or the like for power distribution. In this case, when the capacity of the transformer 5 is as small as about 100 kVA, the current flowing through the second power supply line is 10 A or less, and the current of the normal current transformer 3 greatly deviates from the rated value of the current transformer. There is a problem that the accuracy is greatly reduced. There are two types of current transformers 3 for the instrument, a through type and a winding type. The through type usually has a primary current of several hundred amperes, and a small current flowing through the feeder line on the primary side of the transformer as described above. Since the overcurrent with respect to the current cannot be accurately detected, the protection circuit breaker cannot be operated by the relay. Although the detection accuracy is improved to some extent when the winding is used, there is a problem that the outer dimensions are increased and the cost is increased.
[0005]
The present invention has been made in order to solve the above-described problems, and has focused on the fact that the current on the secondary side is large even if the current on the power supply line on the primary side of the transformer is small. It is an object of the present invention to obtain a distribution line protection device that can accurately detect an overcurrent flowing through a power supply line by detecting a current on a power supply line.
[0006]
[Means for Solving the Problems]
The protection device for a distribution line according to the present invention is provided with a current detection means on the secondary side of a transformer, takes in this detection signal to a protection relay, and when an abnormality occurs, the protection relay opens the protection circuit breaker. is there.
[0007]
In addition, a protection circuit breaker is provided between the second power supply line and the primary side of the transformer, and a current detection means is provided on the secondary side of the transformer, and this detection signal is taken into the protection relay. Opens the protective circuit breaker.
[0008]
Further, a through current transformer for an instrument is used as the current detecting means.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiment 1 FIG.
FIG. 1 shows a distribution line protection device according to a first embodiment of the present invention, and is a single-line connection diagram showing a power distribution system that distributes power by stepping down from a voltage of 22 kV to a low voltage of 210 V. In the figure, reference numeral 1 denotes a first power supply line connected to a substation (not shown), 1A and 1B denote circuit breakers for opening and closing the circuit of the first power supply line 1, and 2 denotes a branch from the first power supply line. Power supply line for supplying a plurality of transformers 5 in parallel to the primary side in a parallel state, 2A is a protective circuit breaker provided at a branch from the first power supply line 1, 5 is a transformer, 6 Is a distribution line connected to the secondary side of the transformer 5, 7 is a feeder circuit breaker that opens and closes the distribution line, 8 is a current transformer for measuring the current flowing through the distribution line 6, and 9 is a transformer for the instrument. This is an overcurrent relay that monitors the presence or absence of an abnormality based on the output from the current distributor 8 and sends an open signal to the protection circuit breaker 2A when an abnormality occurs.
[0010]
In FIG. 1, the transformer 5 is usually 100 kVA, the primary current is about 2 A, and the secondary current is about 270 A. In the system of three transformers 5 shown in FIG. 1, about 270 A flows through the current transformer 8 for the instrument, so that the current transformer 8 has a current transformation ratio (input to output ratio) of about 300/5. to use the through-type current transformer 8. With such a configuration, it is possible to use near the rated value of the current transformer 8, together with the accuracy of the current detection of the distribution line 6 can be greatly improved, configuration is relatively inexpensive feedthrough simple current transformer 8 Can be used.
[0011]
Embodiment 2 FIG.
FIG. 2 shows a distribution line protection device according to a second embodiment of the present invention, which is a single-line connection diagram showing a power distribution system that distributes power by reducing the voltage from 22 kV to a low voltage of 210 V similarly to the first embodiment. is there. In the figure, reference numeral 1 denotes a first power supply line connected to a substation (not shown), 1A and 1B denote circuit breakers for opening and closing the circuit of the first power supply line 1, and 2 denotes protection from the first power supply line. Circuit breaker 2A (first circuit breaker) A second power supply line that branches and is provided to supply a plurality of transformers 5 in parallel to the primary side, and 2B is located between second power supply line 2 and transformer 5 5 is a transformer, 6 is a distribution line connected to the secondary side of the transformer 5, 7 is a feeder circuit breaker for opening and closing the distribution line, 8 Is a current transformer for measuring the current flowing through the distribution line 6, and 9 is an overcurrent for monitoring the presence or absence of an abnormality based on an output from the current transformer 8 for the instrument and sending an open signal to the protection circuit breaker 2B in the event of an abnormality. It is a relay.
[0012]
In FIG. 2, the transformer 5 is usually 100 kVA, the primary current is about 2 A (ampere), and the secondary current is about 270 A (ampere). In the three-transformer 5 system shown in FIG. 2 , approximately 270 A flows through the current transformer 8 for the instrument, so that the current transformer 8 has a current transformation ratio (input to output ratio) of about 300/5. to use the through-type current transformer 8. With such a configuration, it is possible to use near the rated value of the current transformer 8, together with the accuracy of the current detection of the distribution line 6 can be greatly improved, configuration is relatively inexpensive feedthrough simple current transformer 8 Can be used. Further, since the protection circuit breaker 2B is provided between the second power supply line and the transformer 5, when the distance between the transformers 5 is large, the protection circuit breaker 2A and the protection relay 9 are connected as in the first embodiment. It is possible to eliminate signal lines connecting between the power supply lines and to reliably protect each distribution line 6 .
[0013]
In the above description, an example in which the voltage of 22 kV is stepped down to 210 V has been described. However, the present invention is not limited to the above example, and it is not necessary to obtain the required detection accuracy on the primary side due to a large transformer ratio of the transformer 5. For example, the primary side and the secondary side may be any of special high pressure, high pressure and low pressure.
[0014]
Although the transformer 5 has been described with an example of about 100 kVA which is most commonly used, the transformer 5 is not particularly limited to this value, and may have a larger capacity or a smaller capacity. It may be.
[0015]
In addition, although examples of the current transformers of the wound type and the through type have been shown as the current detecting means, a sensor such as a magneto-optical sensor or an optical fiber may be used in addition to the principle of electromagnetic coupling.
[0016]
【The invention's effect】
As described above, according to the present invention, a plurality of transformer primary sides are connected in parallel from a first power supply line via a circuit breaker to a second power supply line to supply power, and the plurality of transformers are connected to each other. A protection relay is provided for monitoring an abnormality of the distribution line based on a signal from a current detection means attached to the distribution line drawn from the secondary side and sending an open signal to the circuit breaker in the event of an abnormality. Since the output units are connected in parallel and the breaker is opened when any of the protective relays outputs an open signal, it is possible to accurately detect the current even when using a transformer having a high transformation ratio. In addition, since only one circuit breaker is required for a plurality of distribution lines, an economical device can be obtained.
[Brief description of the drawings]
FIG. 1 is a single-line diagram of a distribution line showing a configuration of a first embodiment of the present invention.
FIG. 2 is a single-line diagram of a distribution line showing a configuration of a second embodiment of the present invention.
FIG. 3 is a single-line diagram of a conventional distribution line.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 1st power supply line 2 2nd power supply line 2A Protection circuit breaker 2B Protection circuit breaker 5 Transformer 6 Distribution line 8 Instrument current transformer 9 Overcurrent relay

Claims (1)

A second power supply line, which is supplied from the first power supply line via the circuit breaker and connects the primary sides of the plurality of transformers in parallel to supply power, and a distribution line drawn from the secondary side of each of the plurality of transformers. Electric wires, current detection means attached to each of the distribution lines, and monitors the distribution line for abnormalities based on signals from the current detection means installed for each of the distribution lines, and in the event of an abnormality, an open signal to the breaker. And a protection relay for transmitting an open signal, wherein an output section of the protection relay is connected in parallel, and the breaker is opened when any of the protection relays outputs an opening signal .

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