JPS5851722A - 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 protection device for DC transmission lines in a DC transmission system.

Conventionally, there was a device shown in No. 1Ii$ as a type of device. The DC transmission system consists of (1) forward converter, (!) inverse converter, (
3) DC reactor, (4) DC transmission line). (5) is a DC voltage detector (referred to as DCFT) that extracts the DC transmission voltage, and this output goes into a differential circuit (6), where its output passes through a (7 Lebel detector) and is used as an accident detection/output signal (8). Become.

Next, the operation will be explained. By inputting the output of the DCFT into a differentiating circuit, an output proportional to the rate of change of the power line voltage can be obtained. Further, the level detection circuit detects whether the value is above a certain value and outputs an accident detection signal if it is above the certain value.

When there is an accident (9a) on a DC transmission line, the voltage on the transmission line changes rapidly, and when there is an accident (9b) at a converter station, it changes slowly at the resonant frequency determined by the DC reactor μ, the transmission line capacity, etc.

Therefore, when the power transmission line voltage changes suddenly, the output of the differentiating circuit increases and the level detection circuit operates to issue an accident detection signal.

Conventional devices using differentiating circuits detect an accident as long as there is a sudden change in voltage, regardless of the magnitude of the transmission line voltage. In other words, even if the voltage does not drop sufficiently and drops slightly rapidly, it may be considered an accident. DO again
There were drawbacks such as an accident being detected even when noise was added to the PT output.

The present invention was developed to eliminate the above-mentioned drawbacks, and it is an object of the present invention to provide a power transmission line protection device that is composed of a level detection circuit and a delay circuit without using a differentiating circuit.

An embodiment of the present invention will be described below with reference to the drawings.

In the DC transmission system shown in Figure 2, (1) is a forward converter, (
2) shows the inverter, (3) shows the DC reactor, and (4) shows the DC transmission line connecting these. (5) is a direct current voltage detector (DCFT) that outputs a voltage proportional to the voltage of the direct transmission line.
), the output of the j7DCFT is led to a first low voltage detector (tea) (referred to as tyvt) and a second low voltage detector (10b) (referred to as UVI). The UVI output was delayed by the o1J delay circuit. It enters the inhibit circuit (2) as a signal.

This inhibit circuit (2) performs an AND operation on UV2 and the output of the delay circuit (8) to produce an accident detection signal.

The output of the DCFT goes into two low voltage detectors;
Comparing the detection levels of the two low voltage detectors UVI and UVII, UVI is higher. Therefore, when the transmission line voltage decreases, UVI operates first, followed by U'V2. Also, the delay circuit is activated by the operation of tf'V1 and outputs an output after a certain period of time (inhibit)ttl1wt.
Lock the Q-bottle and do not emit any signal indicating the malfunction of my skewer.

That is, an accident detection signal is issued when UV2 operates within a certain time determined by the operator delay circuit of tJVl.

When a line fault (9a) occurs, the line voltage changes rapidly as shown in FIG. 8, so UVI and U'V2 almost simultaneously detect low voltage and issue a fault detection signal. When an accident (9b) occurs in the Maku conversion station, the line voltage changes slowly as shown in Figure 4, and there is a difference in the operating times of UVI and UV2.
If this difference is longer than the delay time determined by the delay circuit, no accident detection signal will be generated.

The above embodiment describes up to the accident detection signal, but this accident detection signal is used in combination with other signals.
bFor example, it may be assumed that a power transmission line accident occurs only when there is no external rate signal (3) in FIG. (to) is an inhibit circuit. The external fault signal (to) may include signals such as commutation failure and bypass bear, in addition to faults on the alternating current side and faults on the converter side.

As described above, according to the present invention, high-speed detection is possible because it is configured with simple circuits such as level detection and delay diagram circuits without using a differentiating circuit or the like. Furthermore, since accidents are detected using only information from one end, no transmission equipment is required.

[Brief explanation of the drawing]

Figure 1 is a diagram showing an example of the conventional device ``OG4'' configuration, Figure 2
The figure shows an embodiment of the power transmission line protection device according to the present invention, Figure 8 shows the signals of various parts when the power line voltage suddenly changes, and Figure 4 shows the signal when the power line voltage changes gradually. It is a figure which shows the signal of each part of. In the figure, (1) is a forward transformer, (2) is an inverse transformer, (
3) is DC react! , (4) is a DC transmission line, (6) is a DC voltage detector, (6) is a differentiation circuit, (7) is a level detection circuit, (8) is an accident detection signal, (9aM transmission line accident%
(9b) is an accident inside the converter station, (lea) is the first low voltage detector, (lob) is the second low voltage detector, 01J is the delay circuit, (2) is the inhibit circuit, (to) is an external accident In the signal, (b) is the power transmission line voltage, (to) is the output of the first low voltage detector, (to) is the output of the second low voltage detector, and αη is the output of the delay circuit. Note that the same reference numerals in the figures indicate the same or corresponding parts. Agent Shin Kuzuno - (2 others) Figure 1 Figure 2 Figure 3 (“41゛45\-1111

Claims (1)

[Claims] a first low voltage detector that detects that the voltage derived from the DC power transmission line is below a first set value; and a timer circuit that outputs an output when the first low voltage detector continues for a predetermined period of time. , an eighth low voltage detector that detects that the voltage derived from the DC power line is equal to or lower than a second set value (lower than the first set value); and a circuit for detecting an accident in the DC transmission line based on the fact that the timer circuit outputs no output.