JPH0444493B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a protective relay device for a power system, and more particularly to a shared multi-line ground fault protection relay whose setting value can be arbitrarily varied depending on the operational status of the power system. Figure 1 shows a 3-terminal system with high-resistance grounded shared multi-line circuits, where 1 is the power supply system, 2 is the high-resistance grounding resistor, 3 and 4 are partially shared lines, and L is the This is a shared section. Also SA, SB and
Each SC is an electric station. In a high-resistance grounding system like the one shown in Figure 1, the current flowing in the upper system generates a zero-sequence circulating current,
When a line ground fault occurs, it leads to misjudgment between the internal direction (internal fault) and the external direction (external fault). That is, the first
In the system shown in the figure, when two lines are used together, the upper system
When a 6500A load is connected, a circulating current of 267A flows, and a zero-phase input of 434A enters the ground fault line selection relay. In a normal high resistance grounding system, 100~
There are many 400A grounded systems, but in such systems, the circulating current is larger than the ground fault current, making it impossible to determine the failure in the event of a single-wire ground fault. In addition, there is a relay that uses a variation width to counter such circulating current, that is, a method in which the circulating current in a steady state is memorized in advance, and the fault current is determined by subtracting the previously stored circulating current from the circulating current in an abnormal state. However, this cannot be used in advance or disconnection or in a 3-terminal system, and cannot be used in re-closing. In addition, the setting value of the protective relay device was set to a constant value regardless of the operating status of the system. ,in this case,
For example, in the shared multiline three-terminal system shown in Figure 1, F
If the SB terminal trips due to a one-wire ground fault at a point, a large circulating current will flow to the relays at the SA and SC terminals, as shown in the table below, which may cause the relays to make false judgments.

[Table] Change in ground fault line selection relay input zero-phase circulation current)
According to the table, in this system, for example, the circulating current
If you take double the margin, it will be 15.4A x at the SA and SC ends.
2 = 30.8A or more, but with this setting value, it may not be possible to detect an incomplete ground fault at the intermediate point. The present invention has been made in view of the above points, and an object of the present invention is to provide a digital relay that is placed on a power transmission line of a power system and protects the power transmission line using a digital quantity, in which the state of the system can be determined by the voltage at its own end. A device for changing the setting value of a protective relay, comprising a judgment means for recognizing the state of the system by obtaining information from the current or the voltage and current at the other end, and a setting value changing means for changing the setting value based on the judgment. It is an object of the present invention to provide a protective relay device which can thereby prevent malfunctions and improve detection sensitivity. The shared multi-line ground fault protection relay of the present invention will be described below with reference to FIGS. 2 to 4. FIG. 2 shows a schematic configuration of the earth fault protection relay of the present invention, where 100 is a system condition determination unit that determines system voltage and current information, 200 is a set value change unit that changes the set value of the protection relay, and 300 is a set value change unit that changes the set value of the protection relay. This is the protection relay section. The system condition determination unit 100 determines the operating state of the system based on the information on the voltage V and current I at its own end, passes the determination signal to the protection relay unit 300, and issues a command to the setting value change unit 200 if necessary. issue. Thereby, the set value changing unit 200 changes the set value of the protection relay unit 300. The protection relay section 300 makes a protection judgment using the changed setting value, and if it judges that there is an internal accident, it outputs a disconnection trip signal. FIG. 3 shows a shared multi-line ground fault protection relay according to an embodiment of the present invention. Line 3, 3a, 3
b, 3c, line 4, 4a, 4b, 4c are 66KV
~154KV high-resistance grounding system transmission line (hereinafter referred to as the guided system), b and c indicate the phase sequence, and lines 6, 6a,
Reference numerals 6b and 6c are busbars of phases a, b, and c of the high-resistance grounding power transmission line. 7 is a T-branch load of the power transmission lines 3a to 3c. 37a-37c and 47a-47c
are current transformers, 3a, 3b, 3c and 4a, 4
A current detection section 8 is formed by differential circuit connection through line difference current detectors 50a to 50c for each phase of a, b, and c of the lines b and 4c. I _ath , I _bth ,
I _cth is the circulating current of each phase of a, b, and c that circulates from line 3 to line 4 due to the induction of power flow in the induction system shown in FIG. 1A. Let S _A be the electric appliance station on the bus 6 side of the guided system, and S _B be the one on the opposite side. The neutral points of S _A and S _B are grounded to the earth through neutral point grounding resistors R _NA and R _NB , respectively. 9 is a bridge and disconnection section where the bridge and disconnectors 9a to 9f are connected as shown in the figure; 10 is a first data conversion section that converts the amount of electricity _S1 from the current detector 8, that is, each phase of a, b, and c; The line difference currents I _as , I _bs , and I _CS are sampled at regular intervals and AD converted. Reference numeral 11 denotes a voltage and current detection unit, which includes a zero-phase voltage detection transformer 12, a voltage detection transformer 13, and a zero-phase current transformer 14 installed on the buses 6a to 6c. Reference numeral 15 denotes a second data converter, which inputs the detection signal _S2 of the first voltage detector 12, that is, the zero-phase voltage _V0 , and samples _V0 at a constant cycle in synchronization with the first data converter. and perform AD conversion. 16 is a filter section and is the output of the first data conversion section 10.
By inputting the digital quantities _S3 of I _as , I _bs , and I _cs , I _as −aI _bs and I _bs − are obtained from the line difference currents of the two phases, respectively.
The arithmetic processing aI _cs , I _cs −aI _as (where a=εj2/3π) is performed to remove the positive phase component. Reference numeral 17 denotes a calculation section for calculating the zero-phase circulating current, and is a comparison/judgment section that performs calculations using the output _S4 of the filter section 16 as input. The first data conversion section 10, the filter section 16, and the comparison/judgment section 17
0 is configured. Reference numeral 200 denotes a set value changing unit that changes the set value based on the output S ₅ of the comparison/determination unit 17 of the system condition determination unit 100 . 19 is a third data conversion section, and a zero-phase current transformer 14
The detection signal S ₇ , that is, the zero-phase current I ₀ is A/D converted. 20 is a zero-sequence current detection section that receives the digital signal _S8 of the zero-sequence current _I0 and detects the zero-sequence current.
21 is a fourth data converter that converts the voltage detection signal _S11 detected by the second voltage detector 13 into a digital quantity. Reference numeral 22 denotes a ground fault phase determination section which receives digital data _S12 from the fourth data conversion section 21 and performs calculations. Reference numeral 400 denotes a ground fault line selection section, which includes a setting signal S ₆ of the setting value changing section 200, a detection signal S ₉ of the zero-sequence current detection section 20, a judgment signal S ₉ of the ground fault phase judgment section 22, and a second data conversion section. The zero-phase voltage signal _S14 from 14 is input, and these are calculated to select the ground fault line. The ground fault line selection unit 400 outputs a ground fault line trip signal _S15 , and uses this signal to protect the high resistance grounding power transmission line of the ground fault line from a ground fault. In the ground fault protection relay with the above configuration, as an example, the circulating current of each phase and the a
The distribution of the ground fault current flowing in the phase lines 3a and 4a and the load current flowing in the lines 3 and 4 is shown in FIG. Here, the circulating currents in each phase of a, b, and c circulating from line 3 to line 4 are Iath, Ibth, and Icth, and the load current flowing in each phase of a, b, and c in line 3 and line 4 is I ^3/a , I ^3/b , I ^3/c and I ^4/a , I ^4/b , respectively
I ^4/c . Further, the ground fault current flowing through the a-phase of line 3 is I ^3/F , and the ground fault current flowing through the a-phase of line 4 is I ^4/F . In FIG. 3, only the guided system is shown, and the ground fault protection relay according to the present invention is installed at an electrical station S _A. When the induced system has a T-branch load 7 as shown, the load currents I ^3/a , I ^3/b , I ^3/c of line 3 and the load currents I 4 ^/a , I ^4/ of line 4 are The corresponding phase currents for ^b and I ^4/c differ in magnitude. In order to calculate the zero-sequence circulating current Ioth at the time of a ground fault according to the ground fault phase, it is necessary to determine the constants Ra, Rb, and Rc in advance. These constants are determined by the setting value changing section 200 as shown in FIG. That is, the current information is input to the system condition determination unit 100.
When S ₁ is input, the output S ₆ of the setting value changing section 200
setting value is changed. Circulating current Ioth, Iath,
Ibth and Icth are proportional to the power flow I of the induction system. Line difference current Ias of phases a, b, and c when the system is healthy,
Ibs, Ics are Ias=I ^3/a −I ^4/a +2Iath Ibs=I ^3/b −I ^4/b +2Ibth Ics=I ^3/c −I ^4/c +2Icth ...(1), and this Ias, Ibs and Ics are detected by the current detector 8 and converted into digital quantities by the first data converter 10. The converted digital amount is subjected to the following calculation in the filter section 16 to remove the positive phase component. Ibc=Ibc-aIcs Ica=Ics-aIas Iad=Ias-aIbs ...(2) The fourth data converter 19 converts the phase voltage detected by the voltage detector 13 into a digital quantity to determine the ground fault phase. It outputs to section 22. The ground fault phase determination section 22 compares the input phase voltage with a predetermined setting value, and outputs a signal _S13 to the calculation section 18 when determining a ground fault. On the other hand, the system condition determining section 100 determines the operating state of the system based on the current information at its own end, and notifies the set value changing section 200 of the determination signal _S5 . The set value changing section 200 selects a constant corresponding to the system operation state from a constant table stored in advance and outputs it to the ground fault line selection section 400. Assuming that the a-phase has a ground fault, the output Ibs-aIcs of the filter unit 16 at the time of the a-phase ground fault becomes the value of the healthy phase circulating current 2 (Ibth-aIcth). The ground fault line selection section 400 multiplies the value Ra selected by the integer constant change section 200 by the output Ibs-aIcs of the filter section 15 to obtain twice the zero-sequence circulating current. When the system is healthy, the signals S ₄ are correct zero-phase circulating currents and are equal, but when the induced system is ground faulted, the line difference current of the ground fault phase includes a current component due to the ground fault. Therefore, ground fault detection can be performed by calculating the output _S4 of the filter section 16 and the selected constant. For example, Ra(Ibs−aIcs)=Rb(Ics−aIas)
...(3) holds true when the system is healthy, but does not hold true when there is a ground fault for the reasons mentioned above. The comparison determination unit 17 of the system condition determination unit 100 performs S ₄
Ground fault detection is performed by comparing two arbitrary calculated values and a constant. Similarly, in the case of a b-phase ground fault, the zero-sequence circulating current is obtained by multiplying Ica=(Ics-aIas) by the selected constant Rb and output to the setting value changing section 200. The ground fault line selection unit 300 is for compensating the zero-sequence circulating current that causes relay malfunction. A ground fault line selection unit that calculates a canceled value of the zero sequence current by subtracting the calculated value of the zero sequence current at the time of a fault, and outputs it to the ground fault line selection unit 300, which is a ground fault line selection relay or a ground fault direction relay. 400 is a zero-sequence current that hardly includes a zero-sequence circulating current component and a zero-sequence voltage V ₀ converted into a digital quantity by the second data converter 15.
It correctly determines faults within the section and faults outside the section, and activates the sheath disconnector 9a of the sheath break section 9 by the trip signal _S15 .
Trip 9b, 9c or 9d, 9e, 9f. The system status that should be determined for the zero-sequence circulating current is whether the zero-sequence circulating current is large. To detect this, for example, the zero-sequence circulating current must be determined by determining the circulating current component that flows through the difference current between lines of each phase. It can be detected by determining the magnitude of the amount obtained by removing the positive phase component from the line difference current of two healthy phases. In the relay device shown in FIG. 4, the output of the first data converter 10 and the output of the third data converter 19 may be used as inputs of the filter unit 16, and the input of the ground fault phase determination unit 22 may be used as inputs of the filter unit 16. The output of the third data detection section 19 may be used as the output. If the circulating current flowing through each phase is large, malfunctions due to the circulating current can be prevented by increasing the set value. Furthermore, if the circulating current is small, by lowering the set value, malfunctions can be prevented and detection sensitivity can be increased. It goes without saying that there are other ways to determine the system status, such as the direction of the current, changes in the current, and breakage conditions. Furthermore, although a configuration has been shown in which the system conditions are determined based only on the information on the own end, more accurate determination can be made by obtaining information on the other end. Various transmission methods such as optical fiber, pilot wire, and microwave can be used to obtain this information, but it is sufficient to transmit only the break conditions. FIG. 4 shows an example of a processing flow when the principle of the present invention is realized by a microcomputer, and describes the main processing. In Figure 4, block B ₂ is the 1st, 2nd, 3rd
and 4 corresponds to the data converter and zero-phase current detection unit, and the voltages E _a , E b , E c of each phase of a, _b , and _c ,
The zero-sequence voltage V ₀ and the zero-sequence current I ₀ measured by the voltage transformer 12 and the current transformer 14 are sampled and held at regular intervals and subjected to AD conversion processing. Block _B3 corresponds to the filter section 16, and Ias,
Among the inter-line difference currents of each phase of Ibs and Ics, the positive phase component is removed from the two-phase inter-line difference currents. Here, a, b
Iab, Ibc, and Ica are obtained by removing the positive phase component from the phase, b, c, c, and a phase line difference currents. Block _B4 corresponds to the comparison/judgment section 17, which inputs the output _S4 of the filter section 16 and judges the system condition from the zero-phase circulating current. Block _B5 corresponds to the set value changing section 200, and selects a tap value based on the judgment result of the comparison judgment section 17. Blocks B ₆ , B ₇ and B ₈ are ground fault line selection section 4
00, and the ground fault phase is determined in block _B6 based on E _a , E _b , and E _c . In block B ₇ the zero-sequence voltage V ₀
A protection calculation is performed using the and zero-sequence current _I0 , and a failure determination is made based on the selected tap value. In block _B8 , it is determined whether or not it is an internal accident based on the determination result. If it is determined that there is an internal accident, a trip signal is output, and if it is not an internal accident, the process returns to block _B1 and the above-mentioned calculation process is repeated. As explained above, in the present invention, in a relay device that protects high-resistance grounded multicircuits installed together with a high-voltage power transmission line in digital quantities, the status of the system can be expressed as voltage information or current information on one end, or on the other end. By changing the set value of the protection relay by a system condition determining means that recognizes based on the information, and a set value changing means that changes the set value based on the determination,
This is designed to prevent malfunctions and increase detection sensitivity. Therefore, according to the present invention, it is possible to use an appropriate setting value for the circulating current that changes due to one end of the system stopping or a preceding interruption, etc., and it is possible to use an appropriate setting value for the circulating current that changes due to one end of the system stopping or a preceding interruption, etc., and to avoid increasing the setting value more than necessary to increase the detection sensitivity. By reliably determining a failure and eliminating the failure, a stable supply of electric power can be achieved.

[Brief explanation of drawings]

Fig. 1 is a shared multi-line model system diagram, Fig. 2 is a block diagram showing the principle of the ground fault protection relay according to the present invention, and Fig. 3 is an embodiment of the shared multi-line ground fault protection relay according to the present invention. , FIG. 4 is a processing flow diagram when the principle of the present invention is realized by a microcomputer. 1...Power supply system, 2...Grounding resistance, 3a~3
c, 4a~4c...High resistance grounding system power transmission line, 5A~
5C...Bus bar of ultra-high voltage transmission line, 6a to 6c...
High resistance grounding system power transmission line busbar, 37a to 37c, 4
7a-47c...Current transformer, 50a-50c...
... Line difference current detector of guided system, 7 ... T branch load, 8 ... Current detection section, 9 ... Sheath section, 1
0...First data converter, 11...Voltage detection unit, 12...Zero-phase voltage transformer, 13... Phase voltage transformer, 14... Zero-phase current transformer, 15... Second data Converter, 16... Filter unit, 17... Comparison/judgment unit, 19... Third data converter, 20... Zero-phase current detection unit, 21... Fourth data conversion unit, 2
2...Ground fault phase determination unit, 100...System condition determination unit, 200...Setting value changing unit, 400...Ground fault line selection unit.

Claims (1)

[Claims] 1. Detects each phase voltage, zero-sequence current, and zero-sequence voltage of a high-resistance grounded shared multi-circuit system, samples them at regular intervals, converts them to digital signals, and uses these digital signals to determine the power transmission system. A protective relay device configured to perform protection calculations includes: a line-to-line difference current detection section installed in the power transmission system; an analog-to-digital conversion section for converting the signal detected by the detection section from analog to digital; A system condition determination unit that determines the operating state of the power transmission system based on the value obtained by removing the positive phase component from the healthy two-phase current output from the conversion unit; a set value changing means for changing the set value by using a set value, and a zero-sequence circulating current calculation means for calculating a zero-sequence circulating current by multiplying the amount by which the positive phase component has been removed;
a ground fault phase determination unit that determines a ground fault phase by calculating the output of a voltage detection means that detects the voltage of the power transmission system;
The set value output of the set value changing means, the output of the zero-sequence current detection section, the output of the ground fault phase determination section, and the value of the zero-sequence voltage are input, and a ground fault line is selected by calculating based on these. 1. A shared multi-line ground fault protection relay device comprising ground fault line selection means for emitting a trip signal according to the ground fault line selection means.