JPS59149720A - Dc line protecting device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a DC power transmission line protection device that can reliably and effectively protect a DC power transmission line from high-voltage side ground faults.

Conventional protection methods include Fi (1) a method that detects and protects voltage changes in DC transmission lines, and (2) a method that protects by detecting voltage drops in DC transmission lines using an insufficient screw link. there were. However, in this type of system, voltage change dvμ or voltage i4 drop in the DC transmission line can occur due to failures other than failures in the DC transmission line, so there is a high possibility that operation A will occur, and the availability rate of the DC transmission system will decrease. This may cause a decrease in the temperature.

Therefore, recently, a current differential method has been used to detect a fault by utilizing the difference between the converter side current and the inverter side current at the time of a DC transmission line fault. FIG. 1 shows a conventional DC M# protection device. In the figure, (1) a forward converter (hereinafter referred to as a converter), (2) an inverse converter (hereinafter referred to as an inverter), (
11) and (21) are DC reactors installed to smooth the DC current and suppress sudden increases in fault current, and (12) and (22) convert it into minute electrical noise proportional to the current flowing in the DC line. DC CT, (101)
, (202) is a signal transmission device that uses the electrical quantity of the DC CT manually and transmits a waveform, and (201) and (102) receive a signal from the signal transmission device and convert the signal into a waveform signal. signal conversion device, (103), (203)
manually inputs the current signals from the signal converters (102), (201) and the DC CTs (12), (22), and outputs a failure detection signal (no) if the deviation of the current value exceeds a certain value. Differential relay, (105), (205)
is an adder, (104) and (204) are DC transmission lines (1
00) shows a constant current suppressing device that controls the direct current flowing through the circuit to a constant value.

Next, the operation will be explained.

When a ground fault (Fl) occurs in the DC transmission line (100), as shown in Fig. 2, the converter side current RFIC increases, but the constant current F&IJ +4 device (xo4) tvm('
pvc J: ! l) By controlling the firing angle of the near hearter (z), the current value 1rsf before the occurrence of the accident is restored. On the other hand, the electrician INV on the inverter side caused an accident F'.
1 Before occurrence/''i Since the direct current end (not shown in Figure 1) is controlled by a constant voltage control device that keeps the pressure constant, the constant current control on the impark (2) side does not function at all.

Therefore, before accident B'1 occurred, the current value flowing through the DC line (100) was
), so the current value is the same on the converter side, inverter, and meter. Simultaneously with the occurrence of accident E11, the DC voltage drops significantly, so the constant voltage control device on the inverter side ceases to function, and the constant spiral flow control device begins to function. Since the polarity of the DC voltage on the same inverter (2) side is reversed, once the inverter 11111 current IINV
decreases to a current value of rsf-1 due to the DC current control of the constant current side device (203).

The signal transmission devices (101) and (202) and the signal conversion devices t (201) and (102) transmit the current waveforms at both ends to each other, and convert the current waveform signal at one end and the current waveform at the other end into a differential relay (103). ) and (203), a differential output F is obtained at each end, and the DC transmission line fault F1 can be detected.

It is usually called the 4-hour r/'i current margin and is set to about 10% of the rated DC' current, and the signal transmission device (10
1), (202), signal conversion device (201), (102
), DC CT (12), (22), and constant current side a1
41 device (104), (204), differential relay (103), (203) REC-IN'
Determine the differential output F under the condition of /+im5%.

Since the conventional protection device is configured as described above, the differential relays (103), (203) and the signal 8 transmission device (
101), (202), direct code conversion device (201),
(102) etc. requires a high degree of seeding, which has the disadvantage that the equipment becomes expensive.

This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and when an accident occurs, the current value on the inverter side is reduced and the difference between the converter side DC current voltage REC and the inverter side DC current voltage INV is increased. The purpose of this invention is to provide a protection device that can detect DC line faults without using high-precision equipment.

An embodiment of the present invention will be described below with reference to the drawings. Third
In the figure, the same reference numerals as in Figure 1 indicate the same or equivalent parts. 13) is a DC F T that converts DC voltage into a certain minute amount of electricity, (111) is an adder, and (112) is a switch S. N, (106) is a current margin correction command value circuit that detects that the DC voltage has decreased from Vd and outputs a DC current margin correction amount; (1100) a current margin setting device that determines the t/i current current margin setting; (110)
O is a current command value setting circuit that sets the current command direct weight raf.Next, the operation will be explained.

The DC voltage value signal output from the DC p'r (13) is manually input to the current margin correction command value circuit (106).

In the current margin correction command value circuit, the input DC' voltage is Vd! as shown in FIG. All settings device ([111
) is detected and the current margin output value is set as Δt2. Therefore, before the DC line accident F1 occurs, a value of about 1096 of the rated DC current is output. After the accident F1 occurs, the DC voltage decreases significantly, so that the current margin command value Q and jx', which is larger than the IPU, are output from the current margin command value circuit. The output signal is sent via a switching SW (112) to a current command value circuit (110) to the constant current side circuit of the converter operating as an inverter.
) is subtracted by the adder (111) from the current command direct weight ref, so the current value on the inverter side is
-7I', which is significantly smaller.

Assuming that the converter (2) is on the inverter side, the current on the converter side is DC c T (12), transmission device (10
1), the signal is manually input to the differential relay (203) via the signal converter (201), and the impark zero current
Cut the difference from f-Δwork 1. Here, Δl can be arbitrarily set using the current yardage command 1-direction circuit (106), so it can be set arbitrarily according to the accuracy of the signal transmission device (101), ID quality device (201), differential relay (203), etc. By setting Δl, #
It becomes possible to detect failures in the DC line from a moment onwards.

As described above, according to the present invention, since the current margin is increased when the DC voltage decreases below a certain value, there is an effect that a highly accurate device is not required and the device is inexpensive.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a conventional DC transmission line protection device, FIG. 2 is a diagram showing a DC current waveform at the time of an accident, FIG. 3 is a diagram explaining an embodiment of the present invention, and FIG. This is a temporal diagram of the figure. (1)...Forward converter, (2)...Inverse converter, (11
), (21)...DC reactor, (12), (
22)...DC CT, (101), (202)
...Signal transmission device, (201), (102)...Signal g replacement box, (103), (203)...Differential relay, (111), (105), (205)...Addition Adder, ((107), (207)--Adder, (10
4), (204) --- Constant current 'aU # device, (1
12)=-switching sw, (100)...DC transmission line,
(13)...Direct l51f, P'T, (106)
...Current margin correction command value circuit formula Rihito Kuzu
No store - Figure 1

Claims (1)

[Claims] In a DC power transmission system in which a Junga converter that converts alternating current to direct current, an inverse converter that converts direct current to alternating current, and the image quality converter are connected by a direct current line, a direct current converter installed at both ends of a direct current transmission line. A transmission device that transmits the output of the direct current transformer of its own terminal to the first terminal, and the difference between the output of the DC current transformer of its own terminal and the output of the DC current transformer of the other terminal via the transmission device. In the protection device for DC transmission lines,
It consists of a current margin command value circuit that increases the current margin on the condition that the 'magnetic pressure signal of the DC voltage detector that detects DC heavy pressure is below a certain set value, and is a converter for direct current transmission failure. A DC line protection device characterized by acting to increase the difference between the side DC current and the inverter side DC current.