JP2000166082A - Short-circuit directional relay - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve trouble detection precision by changing operating characteristics by inputting a setting from the outside, converting a secondary analog value into a digital data for determining a phase difference between power system current and power system voltage, and attaining optimum operation measurement in response to characteristic values of a power system and conditions in the event of a short-circuit trouble. SOLUTION: In a short-circuit directional relay 4 detecting a short-circuit trouble on a transmission line 3, the direction indicated in a short-circuit trouble detected section 8 is taken as a short-circuit trouble direction. If a short-circuit trouble is detected at a trouble position 9, it is regarded as a short-circuit trouble in the short-circuit trouble detected section 8 according to a phase difference between voltage inputted through a voltage transformer 6 and current inputted through a current transformer 5 and the magnitude of input current, so that a protective output is conducted for a breaker 7. If a short-circuit trouble is detected at a fault position 10, it is regarded as a trouble outside the short- circuit trouble detected section 8 according to a phase difference between voltage and current and the magnitude of input current, so that no protective output is conducted. It is thus possible to improve trouble detection precision.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a short circuit directional relay for detecting a short circuit accident on a power system.

[0002]

2. Description of the Related Art FIG. 6 shows a configuration diagram of a power system when a conventional short-circuit direction relay is used. A transmission line 3 connecting the three-phase AC power supply 1 into which the circuit breaker 7 is turned on and another three-phase AC power supply 2
Short-circuit relay (67Q) 4 for detecting short circuit accidents
, The direction indicated by the short-circuit fault detection section 8 is defined as the short-circuit fault detection direction of the short-circuit direction relay 4.

In this situation, when a short-circuit fault occurs at fault point 9, the phase difference between the voltage input via the instrument transformer 6 on the system and the current input via the current transformer 5, The short-circuit direction relay 4 determines that a short-circuit fault has occurred in the short-circuit fault detection section 8 based on the magnitude of the input current and outputs a protection output to the circuit breaker 7.

On the other hand, with respect to a short circuit accident occurring at an accident point 10 on a line connecting the three-phase AC power supply 1 and the circuit breaker 7,
Depending on the phase difference between the voltage input via the instrument transformer 6 on the system and the current input via the current transformer 5 and the magnitude of the input current, the short-circuit directional relay 4 is connected to the short-circuit fault detection section. It is determined that a short-circuit accident has occurred outside of the circuit 8, and no protection output is performed.

FIG. 7 shows the operating characteristics of a conventional short-circuit direction relay which is connected by a 90-degree current with respect to the line voltage.
In the figure, the operation of the short-circuit direction relay is determined by the phase difference and magnitude of the current with respect to the voltage, and the angle φ
Indicates the maximum sensitivity angle of the short-circuit direction relay, and indicates that the sensitivity drops even if the phase of the short-circuit current, which is delayed by the line impedance angle θf at the time of short-circuiting, advances or delays from this φ. Is is the minimum operating current setting value (variable setting value), and φ is the maximum sensitivity angle (fixed value) of the relay.

[0006]

FIG. 8 shows the relationship between the phase current vector when a short-circuit accident actually occurs and the operating characteristics of a conventional short-circuit direction relay. Assuming that the maximum sensitivity angle of the short-circuit directional relay is φ and the current operation setting value is θf, the impedance angle at the time of an accident in the event of a short-circuit accident is θf, θf is the resistance R and reactance of the closed circuit from the directional short-circuit relay to the fault point. X and the arc resistance at the short-circuit point are determined. However, since R and X have different values for each transmission line, and short-circuit resistances such as arc resistance also have different values depending on the accident occurrence situation, θf Is not always constant. Therefore, the impedance angle θf at the time of the accident and the maximum sensitivity angle φ of the short-circuit direction relay do not always coincide with each other, and an error proportional to the difference (φ−θf) occurs when the accident is detected.

For this reason, when a short circuit fault occurs, the direction of the short circuit coincides with the detection direction, and the magnitude of the fault current If is equal to the set value Is.
In spite of the case of being larger than that, the situation where the short-circuit direction relay did not operate occurred.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide a short-circuit directional relay capable of automatically setting a maximum sensitivity angle suitable for a detected impedance angle when a power system accident occurs. Is to provide.

[0009]

In order to solve the above-mentioned object, a first aspect of the present invention is a short-circuit direction relay for detecting occurrence of a short-circuit accident in a power system from two elements, a direction element and an overcurrent element. In, through an operation characteristic setting means for changing the operation characteristics by an external setting input, and through a current transformer and an instrument transformer provided on the power system, the secondary analog amount is converted into digital data, A phase difference measuring unit that measures a phase difference between the power system current and the power system voltage based on a calculation result of the data; and an automatic setting unit that automatically sets an operation characteristic using the result. The present invention is characterized in that it is possible to make an accident detection determination by setting an optimum operation characteristic according to an accident occurrence situation.

According to the first aspect, the maximum sensitivity angle, which is one of the factors for determining the operation characteristics, is variably set, and the maximum sensitivity angle adapted to the system is set by an external input and detected when an accident occurs. Since the automatic setting of the maximum sensitivity angle suitable for the impedance angle is possible, the accident detection accuracy is improved.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of a power system to which a short-circuit direction relay according to the present invention is applied, which is the same as that of the conventional FIG. 6 described above. .

In the figure, in a short-circuit directional relay 4 for detecting a short-circuit fault on a transmission line 3 connecting a three-phase AC power supply 1 with a breaker 7 turned on and another three-phase AC power supply 2, a short-circuit fault detection section The direction indicated by 8 is the short-circuit direction detection direction of the short-circuit direction relay 4.

In this situation, when a short circuit fault occurs at fault point 9, the phase difference between the voltage input via the instrument transformer 6 on the system and the current input via the current transformer 5, Based on the input current and the magnitude of the input current, the short-circuit direction relay 4 determines that a short-circuit fault has occurred in the short-circuit fault detection section 8, and outputs a protection output to the circuit breaker 7.

On the other hand, with respect to a short circuit accident occurring at an accident point 10 on a line connecting the three-phase AC power supply 1 and the circuit breaker 7,
Depending on the phase difference between the voltage input through the instrument transformer 6 on the system and the current input through the current transformer 5 and the magnitude of the input current, the short-circuit directional relay 4 is connected to the short-circuit fault detection section 8. Judging that a short circuit accident has occurred outside, and does not perform protection output.

Next, the internal structure of the short-circuit direction relay of the present invention will be described with reference to FIG. Short-circuit direction relay 4 of the present invention
Are an input conversion module 11, an analog / digital conversion module 12, an external settling module 13, an operation module 14, a trip output module 15, an external interface module 16, an accident detection module 17, a display LCD module 18, a storage module 19, and a data bus. 20.

The ratio X / R of the reactance X and the resistance R of the system impedance to which the short-circuit direction relay 4 is applied.
, The minimum operating current setting value Is, the advancing connection angle of the short-circuit direction relay, the change rate setting value μ of current data that triggers a change in operating characteristics, the maximum sensitivity angle return time T, and the maximum sensitivity angle variable width ±. δ is input to the external settling module 13. While this data is stored in the storage module 19, the operation module 14 calculates the maximum sensitivity angle φs suitable for the power system to be protected based on this data, determines the operating characteristics of the short-circuit direction relay, and determines the result. It is stored in the accident detection module 17 and the storage module 19.

On the other hand, the phase current I and the inter-phase voltage V flowing into the short-circuit direction relay 4 through the current transformer 5 and the instrument transformer 6 on the system are input to the input conversion module 11 and the analog / digital conversion module 12. After the data processing, it is led to the data bus 20. This data is stored in the storage module 19 and sent to the accident detection module 17.

The fault detection module 17 compares the determined operating characteristics with data on the phase current I and the inter-phase voltage V to determine whether a fault has occurred. When an accident is detected, the data is immediately transmitted to the trip output module 15 via the data bus 20.

The module 15 also monitors the rate of change of the input current data I. The rate of change of the current data I (the amount of change per unit time) ΔI Exceeds the set value μ input in advance, the arithmetic module 14 immediately calculates the current impedance angle φs ′ using the latest current data I and voltage data V, and the value is (φs−δ). ) ≤
If it is within the range of φs ′ ≦ (φs + δ), φ
Reset a new operating characteristic with s' as the maximum sensitivity angle.
The reset operation characteristics are stored in the storage module 20, and are immediately transferred to the accident detection module 17,
Accident detection determination is performed using the reset operation characteristics. When an accident is detected, the data is transferred to the data bus 20.
Is immediately transmitted to the trip output module 15. If no accident is detected, the operation characteristic returns to the initial operation characteristic with a set time limit of the maximum sensitivity angle return time T.

The trip output module 15 that has received the accident detection data from the accident detection module 17 performs a protection output to the outside. In the external I / F module 16,
Analog values such as various set values, calculated values, and currents can be output to the outside in response to a request input, and the display LCD module 18 can display those data on the LCD.

FIG. 3 and FIG. 4 show operating characteristics when the short-circuit direction relay according to the present invention is connected by a 90-degree lead current.
Figure 3 shows the ratio of the reactance and the resistance of the transmission line, X / R.
Is a diagram illustrating an operation characteristic determined from the maximum sensitivity angle φs set based on the above and the minimum operation current setting value Is. When a complete short-circuit accident occurs on the transmission line, the impedance angle θf matches the maximum sensitivity angle φs, and it is possible to always perform accident discrimination with the maximum sensitivity.

FIG. 4 shows the operating characteristics after the maximum sensitivity angle is changed to φs ′ by increasing the change rate ΔI of the input current. When the arc resistance at the short-circuit point is large,
A short-circuit accident that cannot be detected by the operation characteristics set by the maximum sensitivity angle φs and the minimum operation current set value Is can be detected by changing the maximum sensitivity angle to φs ′.

Actually, since the operation time is required to change the operation characteristic of FIG. 3 to the operation characteristic of FIG. 4, the protection output is delayed by that time. However, if the short-circuit current If is sufficiently large, the fault detection / protection output can be performed instantaneously without changing the operation characteristics.
In addition, the short-circuit current that cannot be detected unless the operating characteristics are changed is relatively small compared to the complete short-circuit current. By determining the set value Is, it is possible to exclude the influence of the delay in the calculation time.

FIG. 5 is a flowchart of the operation of the short-circuit direction relay according to the present invention. First, considering the protection coordination with other protection relays existing in the power system and the characteristics of the transmission line to be protected by the short-circuit direction relay, the reactance X and the resistance of the system line impedance are considered for the short-circuit direction relay. The ratio X / R of the minute R, the minimum operating current setting value Is, the leading connection angle of the directional short-circuit relay, the change rate setting value μ of the current data that triggers a change in the operating characteristics, the maximum sensitivity angle return time T, the maximum sensitivity angle variable The width ± δ is input (step S1). The short-circuit direction relay calculates / sets the maximum sensitivity angle φs optimal for the system to be protected from the input lead connection angle and X / R ratio (step S2), and further sets the operation characteristics (step S3).

After the above initial settings are completed, the analog /
Based on the input current I / voltage V data that has been subjected to the digital conversion processing (step S4), detection of a fault in the power system is started (step S5). When the short-circuit direction relay detects a short-circuit accident on the system, protection output is instantaneously performed (step S6). If no short-circuit fault is detected, the change rate ΔI of the input current is compared with the current change rate set value μ (step S7). When ΔI <μ, the process returns to the current / voltage input phase (step S4). When ΔI ≧ μ, it is considered that some kind of instantaneous change has occurred in the system regardless of the occurrence of an accident. Therefore, the maximum sensitivity angle is recalculated based on the latest input current / voltage data and set as φs'. (Step S8),
If (φs−δ) ≦ φs ′ ≦ (φs + δ) is satisfied (step S9), the operating characteristics are temporarily changed using φs (step 10). Thereafter, a short-circuit fault detection is attempted again (step S11), and if a fault is detected, protection output is performed (step S6). If no fault is detected, the elapsed time from the point of resetting the maximum sensitivity angle is the maximum sensitivity return time. It is determined whether the set value T has been reached (step 12), and an accident detection is attempted until the set value T is reached. If an accident has not been detected even after the maximum sensitivity angle return time has elapsed, the maximum sensitivity angle and the operating characteristics are returned to the settings before the change (step S13), and the routine after the short-circuit accident detection phase (step S5) is repeated.

[0026]

As described above, the present invention (Claim 1)
According to the above, according to the conventional short-circuit direction relay, it is possible to detect a short-circuit fault that could not be detected even though a short-circuit current larger than the operating current setting value flows, thereby improving the fault detection sensitivity. It has an excellent effect that it becomes possible.

[Brief description of the drawings]

FIG. 1 is a system diagram of a power system to which a short-circuit direction relay according to the present invention is applied.

FIG. 2 is an internal configuration diagram of a short-circuit direction relay of the present invention.

FIG. 3 is an operation characteristic diagram determined from a maximum sensitivity angle and a minimum operation current setting value of the short-circuit direction relay of the present invention.

FIG. 4 is an operational characteristic diagram after changing the maximum sensitivity angle of the short-circuit direction relay of the present invention.

FIG. 5 is an operation flowchart of the short-circuit direction relay of the present invention.

FIG. 6 is a system diagram of a power system to which a conventional short-circuit direction relay is applied.

FIG. 7 is an operation characteristic diagram of a conventional short-circuit direction relay connected by a current advanced by 90 degrees with respect to a line voltage.

FIG. 8 is an operation characteristic diagram of a conventional short-circuit direction relay when a short-circuit accident occurs.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Three-phase alternating current power supply A, 2 ... Three-phase alternating current power supply B, 3 ... Transmission line, 4 ... Short-circuit direction relay by this invention, 5 ... Current transformer, 6
… Instrument transformer, 7… circuit breaker, 8… short circuit accident detection section,
9: Accident point, 10: Accident point, 11: Input conversion module, 12: Analog / digital conversion module, 13
... External setting module, 14 ... Calculation module, 15 ...
Trip output module, 16: external interface module, 17: accident detection module, 18: display L
CD module, 19: storage module, 20: data bus, | Is |: absolute value of minimum operating current, | If |: absolute value of fault current, φs: maximum sensitivity angle (initial setting value), φ
s ′: maximum sensitivity angle (reset value), θf: impedance angle at the time of accident occurrence.

Claims (1)

[Claims] 1. A short-circuit direction relay for detecting the occurrence of a short-circuit accident on a power system from two elements, a direction element and an overcurrent element, wherein: an operation characteristic setting means for changing operation characteristics by an external setting input; The secondary analog amount is converted into digital data via a current transformer and an instrument transformer provided on the system, and the phase difference between the power system current and the power system voltage is measured based on the calculation result of the data. By providing a phase difference measuring means and an automatic setting means for automatically setting an operating characteristic using the result, by setting an optimal operating characteristic according to a characteristic value of a power system and an occurrence situation of a short circuit accident,
A short-circuit directional relay characterized in that an accident detection judgment can be made.