JPS5851730A - Protecting device for dc transmission line - 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 line protection device for protecting the DC power line from ground faults.

As shown in Figure 1, the DC power transmission system consists of AC power sources (1),
Transformer (2), forward converter (3), inverse converter (4), DC reactor (S), forward converter (3) and inverse converter (4)
It consists of power transmission lines (6a), (6b), and (6c) connecting the two, and one end of the power transmission line (a) and the power transmission line (6b) is grounded. In such a DC power transmission system, a current differential method is a common method for protecting lines when a ground fault occurs in a power transmission line.

In this method, as shown in FIG. 2, when a ground fault (7) occurs on a power transmission line (6a), the fault current flows to the fault point, so a difference occurs between the currents flowing at both ends of the power transmission line.

The conventional method is to protect power transmission lines by detecting this difference. This operation uses DC transformers (hereinafter referred to as DCCT) (8) placed at both ends of the transmission line to extract the current from the transmission line and transfer the current value to the transmission line (hereinafter referred to as DCCT) (8).
9), and when the difference between the currents at each end is detected by the detectors (10a and 10b) and the difference is larger than a predetermined value, it is regarded as an accident and the transmission line is protected.

Since the conventional method uses a transmission line, it is necessary to correct the transmission delay arc time in the transmission line in order to take the difference between the currents at both ends. Furthermore, when a failure occurs in the transmission line, it becomes impossible to transmit the current value at both ends, making it impossible to protect the power transmission line.

The present invention was made to eliminate the above-mentioned drawbacks of the conventional power transmission line, and protects the power transmission line by monitoring the balance state of the current flowing through the transmission line without using a transmission line.

An embodiment of the present invention will be described below. ◎0)#i converter in the DC power transmission system shown in FIG.

(4) is an inverse converter, (5) is a DC reactor for smoothing DC current* (aa) (sb) (6c) is a power transmission line connecting the forward converter side and the inverse converter side. (8) is a DCCT installed at the end of a power transmission line, and it outputs the current of the power transmission line. (11) is a detector that detects accidents from these currents. This invention has the above configuration.

In the DC transmission system shown in Figure 3, the transmission line (gm) (llb)
The current flowing through (6c) should not cause an accident in the system hllK#i
It is balanced and the sum of the currents is zero. However, the positive direction is defined as the direction in which the current flows into the Mukaiguhiro DC transmission line and neutral wire. However, a ground fault occurred in power transmission #i (6a) ()
) occurs, the current flowing through the transmission line (6a) is shunted to the ground at the ground fault point, so the current flowing through the transmission lines (6b) (6c) decreases, and the currents flowing through each transmission line become unbalanced. This invention takes advantage of the above, and to realize it, the current flowing in each power transmission is calculated by DCCT (81 and 9), and these currents are added by a detector (1), and the result is determined. The detector (Jl) is configured as shown in Figure 4.The detector (Jl) is configured as shown in Figure 4. 12a), (12b), and (12c) are the currents flowing through each transmission line, and these are added together using a wheel adder, and the result is compared with the determined value 04 using a comparator. In the above example, the power transmission line is (6a)e (6b)e (
6c) However, the protection method of the present invention, which is comprised of 6c), is difficult to apply in the same way even when the power transmission line is comprised only of (shaft) * (sb). In this case, the fault point (ma) of the output current of the forward converter (3)
Since KJJI is generated, there is a difference between the current of neutral AI (6b) and the output current of layer transformation a (j), and this difference is measured by the detector (I).
t).

At this time, the input current of the detector (river) is (Ha) e (l
zb) only.

According to this invention, there is no need to transmit the current to the other end of the power transmission line, so there is no need for a special transmission device, and the power transmission line can be protected by the current only at its own end, which can be affected by problems such as troubles in the transmission line. It is possible to provide highly reliable protection without being affected.

[Brief explanation of drawings]

Figure 1 is a DC power transmission system diagram, Figure 5 is a diagram explaining an example of a conventional protection device, Figure 5aaa is a diagram explaining details of this invention, and Volume 4 is a diagram showing the configuration of a detector of this invention. be. In the figure, (1) is AC power supply % (re is transformer 5 (s)
Fi forward converter, (4) is inverse converter, (S) is DC reactor, (6a) I ('b) * (6c) is transmission line, (Ma) company ground fault point, (81 company DC transformation (9) is the transmission line, and the four-wire detector s (12 m). (lzb) and (tzc) are the currents flowing through each transmission line,
The ring is an adder, the ring is a comparator, and the ring is a judgment result. Note that the same reference numerals in the figures indicate the same or corresponding parts. Agent Makoto Kazuno - Figure 1 Figure 2 Figure 3 Figure 1 Continued from page 1 Applicant Mitsubishi Electric Corporation 2-2-3 Marunouchi, Chiyoda-ku, Tokyo

Claims (1)

[Claims] (1) A first DC transformer that derives the output DC current of a forward converter that converts AC power into DC power and sends it to the DC transmission line, and an inverse converter provided at the receiving end of the DC transmission line. The outputs of the first and second DC transformers are compared with the second DC transformer that derives the DC current of the neutral line from the power source to the forward converter, and the outputs of the first and second DC transformers are compared, and the outputs of the first and second DC transformers are compared. Protection device for DC transmission line equipped with a detector for detecting balance (2) Two circuits of DC transmission line are provided, and a corresponding forward transformer, inverse transformer, and first DC transformer are provided on two sides. is,
2. The DC power transmission line protection device according to claim 1, wherein a common neutral wire is used.