JPH0458715A - Protective relay device for system interconnection - Google Patents

Abstract

PURPOSE:To make the title relay device to not to be operated by a transverse flow at the time of system interconnection and surely operate when reverse power of a value higher than the transverse flow is generated by calculating the transverse flow from the voltage difference between both systems and the impedance at the time of system interconnection and raising the operational level of a reverse power detecting relay by the amount corresponding to the value of the transverse flow until a prescribed period of time has elapsed from the system interconnection. CONSTITUTION:The voltage difference calculating means 281 of an arithmetic sequence unit 28 calculates the voltage difference V between both systems. A system impedance calculating means 282 calculates the impedances of the systems on the basis of opened/closed state signals from auxiliary contacts 7a, 8a, and 9a, A transverse flow calculating means 284 calculates a transverse flow generated when both systems are interconnected. An operational level calculating means 285 calculates the operational levels of reverse power detecting relays 21, 22, and 23 so as to raise their operational levels by amounts corresponding to the value of the transverse flow. An operational level setting and outputting means 286 outputs operational level setting signals 29, 30, and to the relays 21, 22, and 23. After a prescribed period of time has elapsed, the operational levels of the relays 21, 22, and 23 are returned to their steady-state values.

Description

[Detailed Description of the Invention] [Purpose of the Invention (Industrial Application Field) The present invention provides a protection relay for grid connection that protects a commercial power receiving system, a private power generation system, or a power system configured to be interconnectable to the grid. The present invention relates to a protection relay device for grid connection, and more particularly to a protection relay device for grid connection that can reliably prevent malfunctions caused by cross currents flowing during grid connection.

(Prior Art) FIG. 5 is a diagram showing an example of the configuration of a spot network power receiving system equipped with this type of conventional protection relay device for grid connection.

In FIG. 5, the commercial power supply (not shown) includes network transformers 1, 2, 3, fuses 4, 5°6, protector breaker 7. ．． A bus bar 10 is connected via 8.9 to form a commercial power receiving system. In addition, private generator 1
1 is connected to a bus bar 13 via a generator breaker 12, thereby configuring a private power generation system. Furthermore, the bus bar 10 of the commercial power receiving system and the bus bar 13 of the private power generation system are configured to be interconnectable by a bus bar connection breaker 14 .

On the other hand, each commercial power receiving system has a potential transformer (P
T) 15, 16, 17, instrument current transformer (CT) 18, 1
9, 20, and reverse power detection relays 21, 22, and 23 are provided. and instrument transformers 15, 16.1
The system voltage detected at 7 and the instrument current transformer 18
, 19.20 is input to the reverse power detection relay 21 22.23, and when it is detected that the magnitude of the reverse power generated in the grid is greater than the preset operating level, the reverse power is detected. Power detection relays 21.22.23 operate to cut off protector breaker 7.8.9.

By the way, in a spot network power receiving system equipped with such a conventional protection relay device for grid connection, the system of network transformers 1, 2.3 and the private generator 11
When connecting the two systems to the grid by turning on the bus breaker 14, a cross current flows between the two systems due to the phase difference and voltage difference between the two systems, and this causes the reverse power detection relay to There was a problem that 21, 22, and 23 malfunctioned.

Therefore, in order to solve this problem, it has recently been proposed to provide a timer in the output stage of the reverse voltage detection relays 21, 22, and 23, so that the relays are kept on standby for the time from when they are interconnected to the grid until the cross current attenuates. It has been done. However, in such a method, the reverse power detection relays 21 and 22
．． : Since a timer is provided at the +3 output stage, there is a problem that protection will be delayed if reverse power actually occurs in the grid.

(Problems to be Solved by the Invention) As described above, in the conventional protection relay device for grid connection, the device may malfunction due to cross current flowing between both grids during grid connection, or reverse power may be generated in the grid. There was a problem in that protection would be delayed in the event of an occurrence.

The object of the present invention is to provide an extremely reliable system that does not operate due to cross current flowing between both systems when interconnected to the grid, and that operates reliably to protect the grid when reverse power of a value greater than the cross current occurs. An object of the present invention is to provide a protection relay device for grid connection.

[Configuration of the Invention (Means for Solving the Problem) In order to achieve the above object, the present invention provides a protection relay device for a power system that is configured to allow grid connection between a commercial power receiving system and a private power generation system. A reverse power detection relay that is installed in a commercial power receiving system and operates when it detects that the magnitude of the reverse power generated in the power receiving system is higher than the operating level, and the voltage value and level of input voltage from both systems. Voltage difference calculation means that calculates the voltage difference between both systems from the phase difference, determines the system status based on the switch status signal of the commercial power receiving system,
Grid impedance calculation means that calculates the impedance at the time of grid connection according to the grid state, and when a grid connection operation signal is input, the voltage difference calculated by the voltage difference calculation means and the grid impedance calculation means are calculated. The cross current calculation means calculates the cross current at the time of grid connection based on the impedance at the time of grid connection, and the operation level of the reverse power detection relay is increased by the amount equivalent to the cross current value calculated by the cross current calculation means. An operation level calculation means 1 that calculates an operation level, for a corresponding reverse power detection relay based on a switch status signal of a commercial power receiving system, from the time of connection to the grid until a predetermined time elapses, the operation level calculation means 1 calculates the operation level. and an arithmetic and control device having an operation level setting output means for outputting an operation level setting signal calculated by the calculation method.

(Function) Therefore, in the grid connection protective relay device of the present invention, when a grid connection operation signal is input, the cross current between grids that occurs during grid connection is calculated, and the reverse power detection relay is An operating value setting signal is output to the reverse power detection relay to raise the operating level to a level at which the cross current value does not operate until a predetermined time has elapsed since the grid connection. Later, an operation level setting signal is output to the reverse power detection relay so that the operation level is again in the steady state at the time of interconnection. The operating level of the reverse power detection relay changes in response to this operating value setting signal. Therefore, until a predetermined period of time has elapsed since grid connection, the operation level of the reverse power detection relay is raised to a level that does not operate at the cross current value, so that even if cross current flows between both grids during grid connection, This prevents the reverse power detection relay from malfunctioning.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing an example of the configuration of a spot network power receiving system including a protection relay device for grid connection according to the present invention. In FIG. 1, the same elements as those in FIG. 5 are given the same reference numerals and their explanations are omitted, and only the different parts will be described here.

That is, in this embodiment, in addition to the diagram shown in FIG.
6, and the auxiliary contact 7a of the protector breaker 7, 8°9,
ga, 9a4, a grid connection operation signal contact 27, and an arithmetic and control unit 28.

Here, the potential transformer 24 is connected to the network transformer 1,
The voltage of the system 2.3, that is, the voltage of the bus 10, is detected and input to the arithmetic and control unit 28. Further, the instrument transformer 25 detects the voltage of the system of the private generator 11, that is, the voltage of the bus bar 13, and inputs the detected voltage to the arithmetic and control device 28. Further, the impedance input switch 26 inputs the impedance values of both systems to the calculation control device 2.
8.

On the other hand, the auxiliary contacts 7a, ga, and 9a are for inputting open/close state signals of the protector circuit breaker 7, 8.9 to the arithmetic and control unit 28. In addition, the grid connection operation signal contact 27 is
A grid connection operation signal is input to the arithmetic and control unit 28. Furthermore, the arithmetic and control unit 28 predicts and calculates the cross current between the systems that occurs during grid connection based on the voltages of both systems, the impedance values of both systems, switching state signals, and grid connection operation signals from each of the above-mentioned elements. , Reverse power detection relay 21゜22
．． The operation level setting signals 29, 30, 31 for setting the operation levels of the reverse power detection relays 21, 22 .
23.

FIG. 2 is a block diagram showing a detailed configuration example of the arithmetic and control unit 28 in FIG. 1. This arithmetic and control device 28 is
As shown in FIG. 2, it is composed of voltage difference calculation means 281, storage means 282, system impedance calculation means 283, cross current calculation means 284, operation level calculation means 285, and operation level setting output means 286. ing.

Here, the voltage difference calculation means 281 calculates the voltage difference between the potential transformer 24.
The voltage difference between the two systems is calculated from the voltage value of the input voltage and the phase difference thereof.

Further, the storage means 282 is for inputting and storing the impedance values of both systems from the impedance input switch 26.

Furthermore, the system impedance calculation means 283 determines the system state based on the open/close state signals from the auxiliary contacts 7a, 8a, and 9a, and calculates the system impedance according to the system state.

On the other hand, the cross current calculation means 284 calculates the
When the grid connection operation signal from 7 is input manually, the system This is used to calculate cross-flow during interconnection. Further, the operation level calculation means 285 calculates the operation level so as to increase the operation level of the reverse power detection relays 21, 22, 23 by an amount equivalent to the cross flow value calculated by the cross flow calculation means 284. Further, the operation level setting output means 286 includes an auxiliary contact 7a.

For the corresponding reverse power detection relay based on the open/close status signals from 8a and 9a, until a predetermined period of time has elapsed from the time of grid connection (until the cross current generated by grid connection is attenuated)
During this period, the operation level setting signal 29°30.31 calculated by the operation level calculation means 285 is output.

Next, the operation of the grid interconnection protection relay device of this embodiment configured as described above will be explained using FIG. 3 and FIG. 4.

In FIG. 1, the arithmetic and control unit 28 includes the voltage from the potential transformer 24, 25 and the impedance input switch 2.
Impedance values of both systems from 6, auxiliary contacts 7a, 8
Open/close state signals from a and 9a are respectively input.

First, the voltage difference calculating means 281 calculates the voltage input from the potential transformers 24 and 25, that is, the network transformer 1,
The voltage difference ΔV between the two systems is calculated from the voltage value Vl of the voltage input of the system 2.3, the voltage value V2 of the voltage input of the system of the private generator unit 1, and the phase difference thereof. FIG. 3 is a diagram showing the vector diagram. Here, Vl-V2-V
Then, ΔV is expressed by the following formula.

ΔV-2V 5in (Δθ/2) --------(
1) Next, the system impedance calculation means 283 determines the system state based on the open/close state signals from the auxiliary contacts 7a, 8a, and 9a, and determines the system state according to the system state based on the individual system impedance stored in the storage means 282. Calculation is performed to calculate the impedance of the system according to the system state.

For example, in FIG. 1, protector circuit breaker 7.8.
The impedance map of the system when all three 9s are in the on state is as shown in FIG. 4(a), and the impedance Z3 of the system at this time is expressed by the following equation.

Z 3-XR+ (XT/3) + XG --
(2) Similarly, the impedance map of the system when two of the protector circuit breakers 7, 8, and 9 are in the closed state is as shown in No. 4C(b), and the impedance of the system at this time Z2 is expressed by the following formula.

Z2 =XR+(XT/2) 10Xc --(3)
Next, when the grid connection operation signal from the grid connection operation signal contact point 27 is inputted to the crossflow calculation means 284, the crossflow I that occurs when both systems are interconnected is calculated.

is calculated based on equations (1), (2), and (3).

For example, if the cross flow when all three protector circuit breakers 7, 8, and 9 are in the closed state is IF5, then IF5 is calculated by the following equation.

IF5-ΔV/Z.

-2V 5in (Δθ/2)/(XR+(XT/3
)+XG l ・・・・・・
(4) Similarly, if IF5 is the cross flow when two of the protector circuit breakers 7.89 are in the closed state, then
IF5 is calculated by the following formula.

Next, the operation level calculation means 285 calculates that the reverse power detection relays 21 and 2 are
The operation level is calculated such that the operation level of the reverse power detection relays 21, 22, and 23 is increased by an amount equivalent to the cross-current value calculated by the cross-current value calculated by the cross-current calculation means 284.

For example, when all three protector circuit breakers 7, 8.9 are in the closed state, the arithmetic and control unit 28 calculates the cross flow IP3 using equation (4), and sets it to a setting level that does not operate at this IF5. , reverse power detection relay 21,
The operating level for 22.23 is calculated.

Next, in the operation level setting output means 286, the auxiliary contacts 7a, 8a,
Operation level setting signal 29.30 calculated by the operation level calculation means 285 for the corresponding reverse power detection relay 21, 22, 23 based on the open/close state signal from 9a.
．． 31 is output. Then, after a predetermined period of time has elapsed, an operation level setting signal 29 is sent to the corresponding reverse power detection relay 21, 22, 23 so as to return to the setting level of the reverse power detection relay 21, 22, 23 in the steady state after the cross current has attenuated. ，
30.31 is output.

As a result, the operation level of the reverse power detection relays 21, 22, and 23 changes in response to the operation level setting signal, and the system is protected at an operation level that corresponds to the status of the system.

As described above, the grid-connected protection relay device of this embodiment applies to the network transformers 1, 2, and 3 of the commercial power receiving system.
Reverse power detection relay 21゜22.23 is installed in the system of network transformers 1 and 2.3 and operates when it detects that the magnitude of reverse power generated in the system is equal to or higher than the operating level. Input the voltage from the voltage transformer 24 that detects the voltage and the voltage transformer 25 that detects the voltage of the system of the private generator 11, and calculate the voltage difference between the two systems from the voltage value of the input voltage and the phase difference. Voltage difference calculating means 281 for calculating the voltage difference, and storage means 28 for manually inputting and storing the impedance values of both systems from the impedance input switch 26.
2. Auxiliary contact 7a.

A grid impedance calculation means 283 that determines the grid state based on the open/closed state signals from 3a and 9a and calculates the impedance of the grid according to the grid state, receives the grid connection operation signal from the grid connection operation signal contact 27. Then, the cross current calculation means calculates the cross current at the time of grid connection based on the voltage difference calculated by the voltage difference calculation means 281 and the impedance at the time of grid connection calculated by the grid impedance calculation means 283. 284, reverse power detection relay 21, 22, 23 by the amount equivalent to the cross current value calculated by the cross current calculation means 284
The operation level calculation means 285 calculates the operation level so as to raise the operation level of the corresponding reverse power detection relay based on the open/close status signals from the auxiliary contacts 7a, 8a, and 9a, when a predetermined period of time has elapsed since grid connection. (until the cross current generated by grid connection is attenuated), the operation level setting signal 2 calculated by the operation level calculation means 285
Operation level setting output means 28 that outputs 9, 30, and 31.
6, and an arithmetic and control unit 28 having 6.

1. During a predetermined period of time from grid connection until the cross current attenuates, the operating levels of the reverse power detection relays 21, 22, 23 are temporarily raised to a level that does not operate at the cross current value, and then When the time elapses, the operation level of the reverse power detection relays 21, 22, 23 is returned to the original steady operation level, so they will not operate even if a cross current flows between both systems during grid connection, and if the cross current exceeds the cross current, it will not operate. It is possible to operate reliably when reverse power occurs, and it is possible to realize highly reliable grid connection protection depending on the grid situation.

In the above embodiment, the case where there are three network transformer systems, which are commercial power receiving systems, is described.
The present invention is not limited to this, and the present invention can be similarly applied to cases where there are two or more network transformer systems.

〔Effect of the invention〕

As explained above, according to the present invention, it does not operate due to cross current flowing between both systems during grid connection, but operates reliably to protect the grid when reverse power of a value greater than the cross current occurs. A highly reliable protection relay device for grid connection can be provided.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a spot network power receiving system equipped with a grid-connected protection relay device according to the present invention, and FIG. 2 is a block diagram showing a detailed configuration example of an arithmetic and control device in the same embodiment. Figure 3 is a diagram showing the voltage vector and phase difference voltage difference of both systems, Figure 4 is a diagram showing the impedance map of the system depending on the system status, and Figure 5 is a diagram showing the system equipped with a conventional grid-connected protection relay device. FIG. 2 is a configuration diagram showing a spot network power receiving system. 1.2.3...Network transformer, 4,5.6...
Fuse, 7, 8.9...Protector breaker, 7a
, 8a, 9a... Auxiliary contact of protector breaker 7, 8°9, 10.13... Bus bar, 11... Private generator, 12... Breaker for generator, 14... Bus bar Connection breaker, 15, 16.17...Instrument transformer, 18
．． 19.20...Instrument current transformer, 21.22゜23.
... Reverse power detection relay 24.25 ... Instrument transformer, 26 ... Impedance input switch, 27 ...
Grid connection operation signal contact, 28... Arithmetic control device, 29
．． 30.31...operation level setting signal, 281...
Voltage difference calculation means, 282... Storage means, 283...
System impedance calculation means, 284...Cross current calculation means, 285...Operation level calculation means, 286...Operation level setting output means.

Claims (1)

[Claims] In a protection relay device for a power system configured to allow a commercial power receiving system and a private power generation system to be interconnected, the protection relay device is provided in the commercial power receiving system to prevent reverse power generated in the power receiving system. a reverse power detection relay that operates when it detects that the magnitude is equal to or higher than the operating level; a voltage difference calculation means that calculates a voltage difference between the two systems from the voltage values of the input voltages from the two systems and their phase difference; A system impedance calculation means that determines the system state based on the switch status signal of the power receiving system and calculates the impedance at the time of grid connection according to the system state, and when the grid connection operation signal is input, the voltage difference calculation means a cross current calculation means for calculating a cross current at the time of grid connection based on the voltage difference calculated by the means and the impedance at the time of grid connection calculated by the grid impedance calculation means; calculated by the cross current calculation means; an operation level calculating means for calculating an operation level of the reverse power detection relay so as to raise the operation level of the reverse power detection relay by an amount equivalent to the cross current value, On the other hand, the arithmetic and control device includes an operation level setting output means for outputting an operation level setting signal calculated by the operation level calculation means until a predetermined time elapses from the time of interconnection to the grid. A protective relay device for grid connection featuring features.