JPS6338932B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power system protective relay system, and more particularly to a protective relay system for detecting a load on a power system.

Figure 1 shows a typical power transmission system, which includes multiple power sources E _A , E _B , disconnector CB, and transmission line 1.
connected via. 2 is a protective relay device that measures the impedance Z _F up to the fault point and issues a shingle break command 3 to the shingle breaker CB when a fault F occurs in this power system. i and a voltage v from the voltage transformer PT are input.

As a relay 2 that protects the power transmission line system 1,
For example, a distance relay having a quadrilateral characteristic on the resistance R-reactance jX line as shown in FIG. 2 is used.

The upper limit of this quadrilateral characteristic is the distance measurement element SX, the right and left limits are the load detection elements R1 and RB1, respectively, and the lower limit is the direction element D to prevent malfunctions in the case of close-end accidents behind the protective relay installation point. It consists of When the protective relay device 2 is configured digitally, specifically, as shown in FIG. Determine the impedance Z _f to the accident point F in Figure 2, and calculate the distance measurement element 2.
1. Right and left load sensing elements 22 and 23;
The power transmission line system is protected by the output of the AND circuit 31 with the direction determining element 24 and the overcurrent detecting element 25.

Although quadrilateral relays have been described here, blinder relays are also used in combination with Morw relays, which have circular characteristics.In short, they are used to distinguish between the load point on Figure 2 and the fault point position F. There is.

In this way, by combining the blinder element with other elements, the system drawn on the impedance map as shown in FIG. 2 can be protected without waste. Furthermore, even in the event of an accident caused by resistance such as arc resistance or tower resistance, this characteristic can improve the accident detection ability by making R1 and RB1 in FIG. 2 a horizontally elongated quadrilateral characteristic.

However, even a relay having such a beneficial quadrilateral characteristic has the following disadvantages in a double-end power supply system. That is, FIG. 4a is an equivalent circuit diagram showing such a case. In the figure, E _{A and} E _B are the back power supply voltage at both ends of the system, Z _A and Z _B are the back impedance, Z is the line impedance, Z _FA and Z _FB
is the line impedance from the relay installation points A and B to the fault point F, R _F is the fault point resistance, _A , _B
is the fault current flowing from each of the back power sources E _A and E _B to the fault point F. The input voltage _A and current _A of the relay at point A can be obtained from the equivalent circuit shown in FIG. 4b as follows. First, _S , _R and _C are _S = (Z _C + Z _R ) E _A − Z _C E _B / Z _C (Z _S + Z _R ) + Z _S Z _R (1) _R = (Z _C + Z _S ) E _B − Z _C E _A ／Z _C (Z _S ＋Z _R )＋Z _S Z _R (2) _C ＝Z _R E _A ＋Z _S E _B ／Z _C (Z _S ＋Z _R )＋Z _S Z _R (3) However, Z _C ＝R _F ＋Z _FA ＋Z _FB ／2Z (4) Z _S ＝Z _A ＋Z _FA ／2 (5) Z _R ＝Z _B ＋Z _FB ／2 (6) Therefore, _A ＝E _A −Z _{A S} (7) _A = _A −R _{F F} /Z _FA (8) From equations (1) to (8), the impedance seen by the relay is
_ZRY is expressed by the following formula.

Z _RY = _A / _A = Z _FA /1-R _F (Z _R E _A +Z _S E _B ) / {ZFA/
2 (Zc + Z _R ) + ZcZ _R }E _A +Z _A ZcE _B (9) As is clear from equation (9), the impedance Z _RY handled by the relay is the fault point resistance R _F and the power supply at both ends E _A
It can be seen that it is greatly influenced by and E _B.

Now, when we consider the change components Z _FA , R _F , E _A , and E _B in equation (9), first of all, Z _FA represents the distance to the failure point, and on O-O' in Fig. 2, Change. Next, R _F is the arc resistance, and this increase/decrease is expressed as a change in the horizontal axis direction in Figure 2. These Z _FA ,
Since R _F is appropriately determined when defining the protection area, even if Z _FA and R _F fluctuate, this will not cause malfunction as a protection relay. On the other hand, E _A and E _B are essentially changes in the tidal current, and even if other fluctuation factors are fixed, the larger the tidal current is, the closer to the origin O they will be. As a result, blind relay R1
Even if you set it optimally, there is a possibility of malfunction depending on the current.

Figure 5 is an example in which the setting of the blinder element is narrowed to a ₁ because the position at this time is F ₁ , assuming that the power flow is large as shown by the solid line c ₁ , and the actual power flow is When the dashed line c ₂ becomes smaller, the same accident appears to be at point F ₂ , so
This is an example where the blade is cut by the blinder and malfunctions.

In Fig. 6, on the contrary, the power flow is assumed to be small as shown by the solid line c ₂ , and since the position at this time is F ₂ ,
This is an example in which the setting of the blinder element is widened as indicated by _a2 , and when the actual power flow increases as indicated by the broken line _c1 , the same accident appears at point _F1 . As a result,
It is easy to detect external accidents that should not be maintained, which can easily result in malfunctions.

As described above, conventional load detection relays with fixed set values have the disadvantage that they may malfunction or malfunction when an accident involving resistance occurs in a system that has power supplies at both ends.

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, it is an object of the present invention to provide a protective relay that obtains good characteristics by effectively utilizing constant power flow information.

The present invention provides, as a means for solving the above-mentioned disadvantages,
Good characteristics are obtained by varying the setting of the blinder element based on constant power flow information.

FIG. 7 is a characteristic diagram for explaining the protective relay system according to the present invention. In the figure, a ₁ and b ₁ are conventional quadrilateral characteristics, and c and d are impedances equivalent to the power flow. In this Fig. 7, as the power flow changes sequentially from c ₁ and d ₁ to c ₂ and d ₂ to c ₃ and d ₃ , the right and left limits of the characteristic diagram are changed from a ₁ and b ₁ to a ₂ and b ₂ , and then a ₃ and b ₃ every moment.

FIG. 8 is an embodiment shown in a flowchart, and in order to realize the distance relay method, steps 100 to 107 may be repeatedly executed at fixed time intervals determined by the sampling period. The part 200 is a function added by the present invention. First, the basic part will be explained. The part 200 is the instantaneous value v, i of voltage and current.
Incorporate. Next, at 102, the blind relay characteristic equation (〓Z〓 ₀ −V〓) is calculated based on i and v.
Execute 〓>0. Here, by adjusting the phase between the current vector V and the voltage vector V, the slope of the straight line R1 in FIG. 2 is determined. Also, Z〓 ₀ =
R ₀ +jX ₀ is an impedance representing the position of the intersection when a straight line perpendicular to R1 is drawn from the origin O, and by making this variable, the straight line R1 moves left and right as shown in FIG. In step 103, it is determined whether the operation is necessary, in step 104, it is confirmed that the operating state continues, and in step 105, a blinder output is provided. 106 is a sequence processing part; 101
In conjunction with the operation results of other elements obtained in step 107, it is confirmed that the accident is within the protection range, and a shunt command is issued in step 107. Block 200 surrounded by dashed lines is part of the present invention. This is executed when the determination unit 103 determines that there is no accident.

First, the impedance Z〓 _L corresponding to the power flow
(vector quantity) and compares the real part R _L with a preset value R _LO to calculate the difference between 401 and 4.
Flow 05 or flows 301 to 305 are executed.

For example, if R _L is greater than R _LO , then αR _LO (α>1)
When the larger condition continues, the predetermined
If the maximum value R _LONax of R _LO is not reached, βR _LO (βα) is newly set as the set value of R _LO , and γZ _SO (γα) is newly set as the set value of the quantity Z _SO indicating the right limit.

On the other hand, if R _L is smaller than R _LO , if the state continues to be smaller than 1/αR _LO (α>1), the predetermined
If the minimum value R _LOnio of R _LO is not reached, 1/βR _LO (βα) is newly set as the setting value of R _LO , and 1/γZ _SO (γα) is newly set as the setting value of the quantity Z _SO indicating the right limit. be done.

Particularly according to an embodiment of the present invention, when the power flow is large, that is, when _{c 1 and d 1 in} FIG. , that is, c ₃ and d ₃ in FIG.
In this case, make the characteristic diagram wider like a ₃ and b ₃ . Therefore, unauthorized operations can be prevented.

In the above embodiment, the new set value is the original set value multiplied and divided by a constant, but it goes without saying that even if the constant is added or subtracted, the same effect as in the embodiment can be achieved.

Further, the implementation location may be after 102 or after 106 and 007. Alternatively, they may be provided separately.

Furthermore, although the explanation up to now has been based on a digital circuit, the same effects as in the embodiments can be obtained using an analog circuit.

As described above, according to the protective relay system of the present invention, even in the event of an accident involving resistance in a system that has power supplies at both ends, the load detection sensitivity can be made variable in accordance with fluctuations in power flow, thereby eliminating the need for conventional fixed settings. It does not malfunction like protective relays do, or malfunctions when it should be working.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the relationship between the transmission line system and protective relays, Figure 2 is a diagram showing the characteristics of the protection method, Figure 3 is a diagram showing the components of the protection relay system, Figure 4 A,
B is an equivalent circuit in the event of an accident with resistance in a system with power supplies at both ends; Figures 5 and 6 are diagrams showing the relationship between changes in system impedance due to changes in power flow and quadrilateral characteristics of relays; Figure 7 is It is a characteristic diagram for explaining the protective relay system according to the present invention,
FIG. 8 shows the flow according to the present invention. CB...Shipping breaker, v...Voltage, i...Current, F...Fault point, Z _f ...Line impedance to fault point,
SX...distance measurement element, D...direction determination element, R1...
Load detection element, RB1...Load detection element, 1...Power transmission line, 2...Protective relay device, 3...Trip output, E _A
...Back power supply of A end, E _B ...Back power supply of B end, PT...
Voltage transformer, CT...Current transformer.

Claims (1)

[Claims] 1 Distinguish between accidents inside and outside the protection area of the power system according to the operating status of protection elements having multiple directions, and at least one of the protection elements has a blinder element for distinguishing between the accident position and the load position. The protective relay system includes means for calculating an impedance corresponding to the power flow of the power system, and according to the magnitude of the output by the calculation means,
A protective relay system characterized by variable protection range of the blinder element.