JPH06141471A - Underpower relaying device - Google Patents

Abstract

PURPOSE:To prevent the inessential trip of a system circuit breaker by a method wherein, when a purchased electric power value is an underpower settling value or lower, it is judged to be underpower on the power purchase side and the system circuit breaker is tripped. CONSTITUTION:When a purchased power supply 1 and a non-utility generation 2 are in a parallel operation state, the secondary-side voltage PT1 of a potential transformer 11 and a secondary-side load currents CT11 to CT1n, CT21 to CT2n of instrument current transformers 13 to 16 are input to an underpower relaying device 12, and load electric power is detected. When the load electric power is 0 or higher, purchased-supply electric power is detected by an electric current CT1 and the voltage PT1 on the secondary side of the instrument current transformer 10 a the potential transformer 11. When the purchased- supply electric power is an underpower settling value of lower, it is judged to be underpower on the power purchase side, and a trip signal is output to a system-splitting-point circuit breaker CB2 after a definite time. Thereby, it is possible to prevent an inessential trip due to the detection of underpower.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power shortage relay device for detecting an unwarned power failure on the power company side.

[0002]

2. Description of the Related Art FIG. 3 shows a case where a power shortage relay device is applied.
The conventional electric power system diagram will be described. In the figure, 1 is a power purchase power source to which power is supplied from an electric power company, 2 is private power generation, and 3, 4 and 5 are circuit breakers CB which are grid separation points.
1, CB2, CB3, 6, 7, 8, 9 are load system breakers, 10 is an instrument current transformer, 11 is an instrument transformer, 12
Is a power shortage relay device.

Electric power from the purchased power supply 1 is supplied to the respective loads via the system isolation breakers CB1 and CB2 and the breakers 6, 7, 8 and 9. In addition, the electric power of the private power generation 2 is divided into the system breakers CB3, CB2 and the circuit breakers 6, 7,
It is supplied to each load via 8 and 9.

The shortage power relay device 12 is connected to the secondary sides of the instrument current transformer 10 and the instrument transformer 11 provided on the side of the purchased power supply system, and is supplied from these secondary sides. The electric power supplied from the power purchase power source 1 of the electric power company is detected by the electric current CT1 and the voltage PT1, and when the detected electric power is less than a certain value, it is determined that the electric power is insufficient and the system breakers CB1, CB2. Trip CB3. However, when the power shortage is detected, it is effective only when the power purchase power source 1 and the private power generation 2 are operating in parallel, and the self-generated power is generated by tripping the system breakers CB1, CB2, CB3 when the power shortage is detected. Prevents overload operation.

Next, the operation of the power shortage relay 12 will be described with reference to FIG.
This will be described with reference to the flowchart in FIG. When a start command is issued, in the first step 201, it is confirmed that the power purchase power source 1 and the private power generation 2 are operating in parallel.
It is detected by B2 and CB3, and in the second step 202, it is determined whether or not the parallel operation is performed. When the parallel operation is performed, in the next third step 203, the instrument current transformer 10 and the instrument transformer 11 are detected. Calculate the purchased power supply from the secondary side current CT1 and voltage PT1 and compare with the power shortage setting value,
In the fourth step 204, it is determined whether or not it is less than or equal to the settling value, and if it is less than or equal to the settling value, it is determined that there is insufficient power on the power purchase side, and after a certain period of time, in the fifth step 205, a trip signal is sent to the system isolation point breaker CB2. Is being output.

[0006]

As described above, in the prior art, as shown in the flow chart of FIG. 4, if the purchased power source and the private power generation are operated in parallel, the state before the load is operated or the private power generation alone is performed. From the state, when the power purchase power supply is added in parallel and parallel operation is performed, the purchased power is not supplied until the load of private power generation is shifted to a certain amount or the load of the feeder connected to the bus increases. Since the power is not supplied, the power shortage is detected, which causes a problem of tripping the system isolation point breaker.

The present invention has been made to solve the above problems, and its purpose is to prevent unnecessary trips due to insufficient power detection before load operation during parallel operation of power systems or at the time of shifting to parallel operation. It is to provide a power shortage relay device.

[0008]

In order to achieve the above-mentioned object, the present invention is a power system having private power generation that operates in parallel with purchased power at all times, and the purchased power is lost due to a warning power failure on the side of the power company. In the power shortage relay device that detects an accident, a detection unit that detects that the purchased power and the in-house power generation are operating in parallel, and the power shortage based on the detection results of the purchased power and the load power in the parallel operation state. By providing means for enabling the detection circuit, it is possible to prevent an unnecessary trip of the system breaker due to the operation of the insufficient power relay before the load operation during the parallel operation of the power systems.

[0009]

According to the present invention, during parallel operation of power systems to which a power shortage relay is applied, unnecessary trips due to insufficient power detection before load operation or when shifting to parallel operation can be prevented.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of an electric power system to which a power shortage relay device of the present invention is applied. The difference from the configuration of FIG. 3 described above is that the current transformers 13, 14, 1 for instruments provided in the load system are different.
Load current detected on the secondary side of 5, 16 (CT11, CT
1n, CT21-CT2n) is only input to the power shortage relay device 12, and other configurations are the same. Therefore, the same parts are denoted by the same reference numerals and the description thereof will be omitted. .

Next, the operation of this embodiment will be described with reference to the flowchart of FIG. When the start command is issued, in the first step 101, it is detected by the system breakers CB1, CB2, CB3 that the power purchase power source 1 and the private power generation 2 are operating in parallel. It is determined whether or not it is the parallel operation state, and the process ends. However, in the parallel operation state, the following third step 1
The voltage PT1 on the secondary side of the transformer 11 for meters and the load currents CT11, CT1n, CT21 ... C detected on the secondary sides of the current transformers 13, 14, 15, 16 provided on the load system at 03.
T2n is input to the power shortage relay device 12 to detect the load power, and in the fourth step 104, it is determined whether the load power is 0 or not. If the load power is not 0, the process returns to the third step 103. If the load power is 0 or more, in the fifth step 105, the purchased power supply is detected by the current CT1 and the voltage PT1 on the secondary side of the instrument current transformer 10 and the instrument transformer 11, and the next sixth step. At 106, it is compared whether or not the purchased power is equal to or more than the power shortage settling value.
Return to step 105. If the purchased power is equal to or more than the power shortage setting value, the power shortage detection circuit is set in the seventh step 107. In this set state, in the eighth step 108, the purchased electric power value and the insufficient power settling value are compared, and in the ninth step 109, it is determined whether or not the settling value is less than or equal to the settling value. When it is less than or equal to the set value, it is determined that there is insufficient power on the power purchase side, and after a certain period of time, a trip signal is output to the system separation point breaker CB2 in the tenth step 110, and the process ends.

As described above, the flow chart of this embodiment is different from the conventional flow chart of FIG.
1-CT1n or CT21-CT2n has a function of detecting load electric power and a function of detecting that the detected electric power is equal to or more than the insufficient electric power settling value at the time of detecting the purchased electric power. The motion detection is configured to be effective when the system is operated in parallel and the load is operated (the state in which there is a flow of purchased power and load power).

Therefore, the unnecessary trip of the system breaker can be prevented by the operation of the power shortage relay device before the operation of the load or before the load transfer of the private power generation.

[0014]

As described above, according to the present invention,
In parallel operation of power systems to which the insufficient power relay device is applied, it is possible to prevent unnecessary trips due to insufficient power detection before load operation or when shifting to parallel operation.

[Brief description of drawings]

FIG. 1 is a power system diagram using a power shortage relay device according to the present invention.

FIG. 2 is a flowchart for explaining the operation of FIG.

FIG. 3 is a power system diagram using a conventional power shortage relay device.

4 is a flowchart for explaining the operation of FIG.

[Explanation of symbols]

1 ... Purchased power source, 2 ... Private power generation, 3, 4, 5 ... System breaker, 6, 7, 8, 9 ... Load side breaker, 10, 13,
14, 15, 16 ... Current transformer for instrument, 11 ... Transformer for instrument, 12 ... Power shortage relay device.

Claims (1)

[Claims] 1. A power shortage relay device for detecting an accident in which power purchased is lost due to a warning power failure on the side of a power company in a power system having private power generation that operates in parallel with power purchased at all times. A power system that includes a detection unit that detects that electric power and private power generation are operating in parallel, and a unit that activates a power shortage detection circuit based on the detection results of purchased power and load power in the parallel operation state. A power shortage relay device that prevents unnecessary trips of the system breaker due to the operation of the power shortage relay before the load operation during parallel operation.