JPH049014B2 - - Google Patents

Description

[Detailed description of the invention] [Technical field of the invention]

The present invention relates to a protective relay device (hereinafter abbreviated as relay) for protecting an electric power system.

[Prior art]

A conventional device of this type is shown in FIG. The figure shows a simulated system diagram of the power system, where 1 indicates the back power source at the a end and 2 indicates the back power source at the b end.
Reference numerals 3 and 4 indicate busbars at the a-end and b-end, respectively, 5 a transformer that introduces voltage to the relay 8, and 7 a power transmission line. Next, the operation will be explained. The electrical angle of the data after sampling the voltage introduced from the transformer 5 to the relay 6 at a predetermined sampling frequency is
Data separated by 90° from each voltage V(t), V(t-90°)
Perform the following arithmetic processing as V ² (t) + V ² (t-90°) ...(1) Now, if voltage V(t) = Vsinωt, then voltage V(t-
90°) is multiplied by Vsin(ωt−90°). These above
Substituting into equation (1), V ² sin ² ωt + V ² sin ² (ωt−90°) = V ² sin ² ωt + V ² (−cosωt) ² = V ² (sin ² ωt + cos ² ωt) = V ² , and the voltage The square value of the magnitude of is obtained. This square value is compared with a preset set value, and when it is smaller than the set value, an electrical command is output. As mentioned above, the conventional protective relay system used only the voltage at the relay installation point for calculation processing, so the second
As shown in the figure, if the power system fault point (center point of loss of synchronization) There were drawbacks such as being unable to use it.

[Summary of the invention]

This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and it supplies a correction value to the voltage at the relay installation point based on the current at the relay installation point and the preset impedance of the transmission line,
The determination processing section calculates the average voltage by inputting the voltage of the other end and the voltage of the own end obtained as a result, calculates the minimum voltage from each of the above voltages, and calculates the rate of change of this minimum voltage. The purpose of this invention is to provide a protective relay device that accurately improves the sensitivity of the relay.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. In Fig. 3, which shows a simulated power system diagram, 1 and 2 are the back power sources at the a and b ends, respectively, and 3 and 4 are
are the busbars at the a and b ends, 5 and 6 are the currents in the relay 8,
Shows current transformers and transformers that introduce voltage. FIG. 6 is a configuration diagram showing the signal processing circuit of the relay 8, in which 81 is a voltage calculation processing section that calculates the voltage at the other end, 82 is an average voltage processing section that calculates the average voltage of the own end and the other end, 83 is a minimum voltage calculation section that calculates the minimum voltage, and 84 is a voltage change rate calculation section. Reference numeral 86 denotes a determination processing section composed of a minimum voltage calculation section 83 and a voltage change rate calculation section 84. The voltage calculation processing unit 81 inputs the bus voltage V ₃ and the line current I, and calculates an output voltage (corrected voltage amount) as the voltage at the other end (V ₃ −IZl). In order to calculate the average voltage of the own end and the opposite end, the average voltage processing section 82 inputs the output voltage V ₄ and the bus voltage V ₃ and outputs the average value voltage Vh. The minimum voltage calculation unit 83 performs a process of selecting the minimum voltage among the voltages V ₃ , V ₄ , and Vh. The voltage change rate calculating section 84 receives the input from the minimum voltage calculating section 83, compares it with a set value, and sends out the operating output of the relay. Next, the operation of the present invention will be explained with reference to the vector diagrams of FIGS. 4 and 5. Now, when the back power source 1 and the back power source 2 are out of synchronization and the phase difference angle becomes 90 degrees apart, the vector diagram shown in FIG. 4 will be obtained. However, the center point of step-out is between ends a and b. The voltages V ₁ , V ₂ , V ₃ , and V ₄ shown in FIG.
These are voltage vectors of the back power source 1, back power source 2, bus bar 3, and bus bar 4 shown in the figure. Current I is a current flowing from bus bar 3 to bus bar 4, and Zl is a preset power transmission line impedance. Transmission line 7 is almost L
, the current I is the voltage as shown in Figure 4.
Orthogonal to the vector connecting V ₁ and voltage V ₂ . As is clear from the figure, in order to obtain the voltage of the bus 4 at the bus 3, it is preferable to calculate the relationship between the voltage V ₃ , the transmission line impedance Zl, and the current I. Further, the average voltage is calculated as (V ₃ +V ₄ )×1/2=Vh, and the voltage change rate is calculated using the smallest voltage among the voltages V ₃ , V ₄ , and Vh. As shown in Fig. 4, when the center point of step-out is between busbars 3 and 4, the average voltage Vh is the minimum,
It is clear that if the magnitude of the average voltage Vh is calculated and a command is issued when it is smaller than a set value, the sensitivity will be higher than when the voltage _V3 or the voltage _V4 is used. Next, as shown in the vector diagram of FIG. 5, when the center point of step-out is outside the b end, voltage V ₄ becomes the minimum, and high sensitivity can be obtained by using voltage V ₄ .

【Effect of the invention】

As described above, according to the present invention, the protection calculation is performed using the minimum voltage among the self-end voltage, the voltage at the farthest end of the protection interval, and the voltage at the intermediate point, so that a protection connection with high reliability and high sensitivity can be achieved. This has the effect of providing electrical equipment.

[Brief explanation of drawings]

Figure 1 is a simulated power system diagram, Figure 2 is the voltage distribution diagram of Figure 1, Figure 3 is a simulated power system diagram explaining the present invention, Figures 4 and 5. is a vector diagram of the present invention, and FIG. 6 is a configuration diagram showing signal processing of the relay. 1, 2... Back power supply, 3, 4... Bus bar at end a, b end, 5, 6... Current transformer, transformer, 8... Relay, 81... Voltage calculation processing unit, 82... Average Voltage processing section, 83... Minimum voltage calculation section, 84... Voltage change rate calculation section, 86... Judgment processing section.

Claims (1)

[Claims] 1. The voltage and current output from the transformer that introduces the voltage and the current transformer that introduces the current at the relay installation point, and the preset impedance of the transmission line that connects the own end and the other end, a voltage calculation processing section that calculates the voltage of the transformer, and an average voltage processing section that calculates the average voltage of the own end and the opposite end by inputting the voltage output from the transformer and the voltage output from the voltage calculation processing section. and a minimum voltage calculation unit that inputs the voltage output from the transformer, the voltage output from the voltage calculation processing unit, and the average voltage output from the average voltage processing unit, and selects and processes the minimum voltage. A protective relay device comprising: a voltage change rate calculation unit that calculates the rate of change of the voltage output from the minimum voltage calculation unit, and sends out an operating output of the relay by comparing it with a set value; and a determination processing unit.