JPH09233680A - Power failure detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power failure detector which can specify the cause of power failure and which can make a proper operation and control of a private power generating facility. SOLUTION: In a power receiving facility provided with a private power generator wherein the voltage of a three-phase commercial power supply is transformed by PT2 which has a first and a second fuse 3, 4 and then is input into a protective relay circuit, single-phase undervoltage relays 1RS, 1ST, 1TR are installed between each two phases out of three phases at the secondary side of the PT2. The outputs of the three undervoltage relays are input into an AND circuit 11 and an OR circuit 12. Then, the output of the AND circuit 11 is an inhibit input of an inhibit circuit 13 and the output of the OR circuit 12 is the other input of the inhibit circuit 13. When all the three undervoltage relays 1RS, 1ST, 1TR operate, it is determined that there is a power failure and then a switching control signal is sent to a private power generator. When either one of the three undervoltage relays 1RS, 1ST, 1TR operates, it is determined that fuse melts and then an alarm signal to tell the accident is generated under the condition that a power failure detection should be conducted with priority.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power failure detection device which is installed in a customer equipped with a private power generation facility and whose detection output is used for starting a generator, controlling load selection, and the like.

[0002]

2. Description of the Related Art When a power outage occurs on the power transmission side (commercial power supply side), a consumer uses a transformer (P
T) 2 has a single-phase AC undervoltage relay (UVR) 1 provided on the secondary side to detect a power failure, disconnect the load, and start the private generator. A primary fuse (PF) 3 is connected to the primary side of PT2, a secondary fuse (F) 4 is connected to the secondary side, and a PT terminal (PTT) 5 is attached to the protective relay circuit side of the secondary fuse 4. Is provided.

[0003]

When the power failure detection circuit is composed of one single-phase undervoltage relay as described above, not only the power failure due to the accident on the power transmission side, which is the original purpose of detection, but also P
Since the single-phase undervoltage relay 1 operates even if the primary or secondary fuses 3 and 4 of T2 are blown or the connection is defective, unnecessary operation control of the private power generation equipment is started.

Therefore, an object of the present invention is to solve the above problems, to provide a power failure detecting device capable of identifying the cause of a power failure and performing appropriate operation control of a private power generation facility.

[0005]

DISCLOSURE OF THE INVENTION The present invention relates to a private generator which transforms the voltage of a commercial power source of three-phase AC with an instrument transformer having primary and secondary fuses and uses it as an input of a protective relay circuit. In the provided power receiving equipment, it is determined that there is a power failure when all three single-phase AC undervoltage relays and three single-phase AC undervoltage relays installed between the three phases on the input side of the protective relay circuit are in operation. Generates a control signal to switch to the power supply by the private power generation equipment, and when any one of the three single-phase AC undervoltage relays is operating, the power failure detection is determined as a priority condition to determine that the fuse has blown, and an alarm signal to that effect. It is characterized by having a voltage loss cause identification circuit that generates a voltage loss.When the fuse is blown, the operation control of the private power generation equipment such as disconnection of the load and start of the generator is not started, and it is possible to appropriately It can be operated power generation equipment.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of the present invention. In the figure, 1RS is a single-phase AC undervoltage relay provided between the R and S phases, 1ST is a single-phase AC undervoltage relay provided between the S and T phases, and 1TR is a single-phase AC undervoltage relay provided between the T and R phases. 2 is an instrument transformer (PT), 3 is PT
Primary fuses 4 are PT secondary fuses.

That is, the voltage of the commercial power supply for three-phase alternating current is
Single-phase AC between each phase of the input side of the protective relay circuit (secondary side of the transformer 2 for meters) when the voltage is transformed by the transformer 2 for meters which has the secondary fuses 3 and 4 and used as the input of the protective relay circuit. Undervoltage relays 1RS, 1ST, 1TR are provided.

The outputs of the three single-phase AC undervoltage relays 1RS, 1ST, 1TR are ORed with the AND circuit 11.
The output of the AND circuit 11 is input to the inhibit terminal of the inhibit circuit 13, and the OR circuit 12 is used as the input of the circuit 12.
The output of is used as the input of the other input terminal. AND circuit 1
When the condition 1 is satisfied, it is determined that there is a power failure (power failure due to a power transmission side accident), and the control signal generation unit 14 generates an operation control signal for the private power generation facility (a control signal for starting the private power generator and disconnecting the load), When the condition of the OR circuit 12 is satisfied, a power failure detection (condition of the AND circuit 11 is satisfied) is used as a priority condition to determine that the fuse is blown (blown fuse, defective connection), and the warning signal generation unit 15 generates a fuse blown warning signal. I have to. That is, a voltage loss cause identifying circuit is configured to determine the cause of the voltage loss on the secondary side of PT2.

Next, the operation will be described. In case of power failure due to power transmission side accident, three single-phase AC undervoltage relays 1
RS, 1ST, 1TR all operate, the condition of the AND circuit 11 is satisfied, and the control signal generation unit 14 generates an operation control signal for the private power generation facility (a control signal for starting the private power generator and disconnecting the load). . At this time, the output of the inhibit circuit 13 is at "L" level. Therefore, the warning operation of blown fuse is not performed.

When the power transmission side is normal and one of the primary or secondary fuses 3 or 4 of PT2 is blown, only the single-phase AC undervoltage relay associated with the blown fuse phase is activated. Therefore, even if the condition of the OR circuit 12 is satisfied, the condition of the AND circuit 11 is not satisfied, the output of the inhibit circuit 13 becomes the “H” level, and the alarm signal generation unit 15
A fuse blown alarm signal is generated from.

[0011]

As described above, according to the present invention, three single-phase AC undervoltage relays are provided, and the cause of the voltage loss is determined by the combination of the outputs. It becomes possible to accurately identify whether or not the voltage is lost due to the fuse blown on the protection circuit side. As a result, the operation control of the private power generation equipment, such as the disconnection of the load and the start of the private power generator, can be appropriately performed only during a power failure due to a power transmission side accident. Moreover, the abnormality can be promptly known by the fuse blow alarm.

[Brief description of drawings]

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

FIG. 2 is a connection diagram showing a configuration of a conventional example.

[Explanation of symbols]

1RS ... Single-phase AC undervoltage relay between R and S phases 1ST ... Single-phase AC undervoltage relay between S and T phases 1TR ... Single-phase AC undervoltage relay between T and R phases 2 ... PT 3 ... PT Primary fuse 4 ... PT2 Next fuse 11 ... AND circuit 12 ... OR circuit 13 ... Inhibit circuit 14 ... Private power generation facility operation control signal (power failure detection signal) generator 15 ... Fuse blown alarm signal (fuse blown detection signal) generator

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Claims (1)

[Claims] 1. A protective relay in a power receiving facility equipped with a private generator, which transforms a voltage of a commercial power supply of a three-phase alternating current with an instrument transformer having primary and secondary fuses to be used as an input of a protective relay circuit. 3 provided between each of the 3 phases on the input side of the circuit
Single-phase AC undervoltage relay and all three single-phase AC undervoltage relays are judged to have a power failure during all operations, and a switching control signal for power supply by the private power generation equipment is generated to generate three single-phase AC A power failure detection device comprising a voltage loss cause identification circuit that determines a fuse failure as a priority condition when any one of the AC undervoltage relays is operating and determines that a fuse has blown, and generates an alarm signal to that effect.