JPS5970129A - Ground-fault accident detector for dc transmitting neutral 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 device for detecting a ground fault in a DC transmission line, or a ground fault occurring on the neutral line of a DC transmission line operated in bipolar operation.

This type of device forms part of a protection device for DC transmission lines, and a conventional device is shown in FIG. In the figure, 1N is a power transmission line that transmits positive polarity current, 1G is a neutral wire, 1N is a power transmission line that transmits negative polarity current, 2a, 2b
are connected to each end of the power transmission line 1P,
d is connected to each end of the power transmission line 1N or an axle, 3a is an AC/DC converter connected between the reactor 2a and the neutral wire 1G, and 3b is an AC/DC converter connected between the axle 2b and the neutral wire 1G.
3c is the reactor 2b and neutral IfiA
3d is an AC/DC converter connected between reactor 2d and neutral #i1G; 4 is an AC/DC converter connected between reactor 2d and neutral #i1G;
a is a setting device that generates a command current signal for setting the current value in the power transmission lines IP, IN&C; 4b is a setting device that generates a bias signal for setting the bias current value to be added to the DC of the power transmission lines IP, IN; 5a and 5b are adders that add the command current signal and the bias signal with the polarities shown in the figure; 6 is an adder 5a that adds the bias signal of the setter 4b;
Contacts 5a and 5b leading to the adders 5a and 5b generate firing pulses for constant current control of the AC/DC converters 3a, 3b based on the output signals of the adders 5a, 5b.

3b, 7a and 7b are DC current transformers provided at each end of the neutral wire 1G, 8a and 3b have a predetermined delay time, and the output of the DC current transformer 7a is used as an input signal. Delay circuits 9a and 9b are delay circuits 8a.

8b and the output signals of transmission devices 10a and 10b, which will be described next, are input, and when an abnormality is detected by comparison, a differential protection relay operates to protect the power transmission lines IP and IN, 1
0a and 10b are transmission devices that transmit the output of the DC current transformers 7a+7b for comparison with the current value at the other end. One end of the neutral wire 1G is grounded.

Next, the operation will be explained. The specified current value to be applied to the power transmission lines tp and iN is set in the setting device 4a, and the additional pressure neutral wire 1G
In order to facilitate the detection of ground faults occurring on the
is closed in a timely manner, and the bias signal of the setter 4b is inputted to the adders 5a, 5bK through the contact 6 with the polarity shown. For this reason, the adder 5a.

The outputs of 5b have unequal values and are sent to the control circuit 5a.

The ignition pulse inputted to 6b and controlled thereby controls the AC/DC converters 3a and 3b. AC/DC converter 3a, 3
b sends DC power to power transmission [I P , I N via reactor 2a+20 in accordance with the ignition pulse. This DC power is transferred to the AC/DC converter 3c at the other end of the power transmission lines IP and IN.
, 3d to AC power, which is supplied to a load (not shown). Power transmission @IP.

Since the DC current flowing through 1N has opposite polarity, the neutral wire 1G
The current flowing above is for the time being of both parties, and the DC current transformer 7
a, 7b, the current is input to differential protection relays 9a, 9b via delay circuits 8a, 8b, and is input to differential protection relay 9 on the other side via transmission devices 10b, 10a.
It is also input to b and 9a. In this way, the differential protection relays 9a, 9b compare the currents detected at both ends of the neutral wire 1G, and if the difference between them is greater than or equal to the bias set by the setting device 4b, then Activates the protection operation output.

On the other hand, during the period when the contact 6 is not closed, the adders 5a and 5
Since the outputs of the AC/DC converters 3a and 3b are balanced, the outputs of the AC/DC converters 3a and 3b are balanced, and the current flowing through the neutral wire 1G becomes substantially zero.

The conventional detection device has the above configuration,
Requires complex and noise-sensitive transmission equipment;
Furthermore, since the power transmission system cannot be kept in an unbalanced state for a long period of time, the timing control, that is, the synchronization control required to compare the current values detected at both ends of the neutral line, is also complicated.

This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and the voltage on the transmission side of the power transmission line is detected by a DC transformer, and this voltage and the voltage flowing through the grounding point of the neutral wire are It is an object of the present invention to provide an accident detection device for a DC power transmission line whose configuration can be simplified by using an IC that uses the state of current as a logical condition for accident detection.

Hereinafter, FIG. 2 showing an embodiment of the present invention will be described. In FIG. 2, the same symbols as in FIG. 1 indicate the same parts, and 11a and 11b are power transmission! i:J! IP.

1N DC transformer installed on the power transmission side, 12 is the neutral wire 1
The DC current transformers 13a and 13b for detecting the current flowing through the ground point of G serve as detectors that respond to a predetermined input voltage or lower, and detect the voltage output from the DC transformers 11a and 11b. The DC undervoltage relay (hereinafter referred to as "relay") 13c serves as a detector that responds when the input voltage exceeds a predetermined input voltage. 14 is an AND gate that performs an AND operation between the inverted logic of the outputs of the relays 13a and 13b and the output of the relay 13c to obtain an accident detection signal.

Next, the operation will be explained with reference to the time charts shown in FIGS. 3 and 4. As explained in Fig. 1, contact 6
is closed between times t1 and t2, the power transmission lines IP and IN become unbalanced, and an unbalanced current equivalent to twice the bias set in the setting device 4b flows through the neutral wire 1G (Fig. 3a).
, b). However, since it is above, the relay 13c does not respond. Therefore, the AND gate 14 is not opened and no accident detection signal is output (FIG. 3d).

On the other hand, when a ground fault shown in Figure 2 occurs in the neutral wire 1G, the current in the neutral wire 1G (the fourth
Figure C) is shunted, and the current 1 exceeding a predetermined value flows through the DC current transformer 12.
1 12 (l□ is the current due to the power transmission line 1P (Fig. 4a),
12, a current due to the power transmission i1N (FIG. 4b)) flows, so the relay 13c responds. However, the transmission line IP, I
Since the voltage of N does not drop below the predetermined value, relay 13a
, 13b does not respond. Therefore, the AND gate 14 is opened and an accident detection signal is output (FIG. 4d).

When a ground fault occurs on the power transmission line 1P or 1N, the output voltage of the DC transformer 11a or 11b drops below a predetermined value, so the relay 13a or 13b responds and the AND gate 14 is inhibited, preventing the accident. No detection signal is output.

In the above embodiment, a bias current was added to the current of the power transmission line with both positive and negative poles in order to detect a ground fault, but the same effect can be obtained even if the bias current is added to either one or both at different times. be effective.

As described above, according to the present invention, a ground fault in the neutral wire is detected from the logical condition based on the voltage state of the power transmission line on the power transmission side and the current state of the grounding point of the neutral wire. This has the effect of simplifying the process and increasing reliability.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a conventional □ detection device, Fig. 2 is a block diagram of a detection device according to an embodiment of the present invention, and Figs. 3 and 4 are timing charts of the operation of the detection device shown in Fig. 2. It is. IN, IP...power transmission line, 1G...neutral line, 3a~3
d... AC/DC converter, 4a, 4b... Setting device, 5a,
5b...Adder, 6a, 6b--Control circuit, 11a
, 11b... DC transformer, 13a to 13c... Relay, 14... AND gate. Note that the same reference numerals in Figure 5 indicate the same parts. Agent: Makoto Kuzuno (1 person) ”O +f) Exposure procedure amendment group (spontaneous) Mr. Commissioner of the Japan Patent Office 1, Indication of case, Patent Application No. 181020/1982 2
Name of the invention: Device for detecting ground faults in neutral wires for direct current power transmission 3; Relationship with the person making the amendment Patent applicant address: Tokyo Tech: (Marunouchi-11, 111-ku, Chiyo, Miyako)
12-3CJ Name (601) Mitsubishi Electric Corporation Representative Hitoshi Katayama 4, Agent address Marunouchi 2J-r, Chiyo Il1-ku, Tokyo:
No. 12 3) Shi. 5. Detailed explanation of the invention in the specification subject to amendment
” he corrected. (In the 21st specification, page 2, line 10, ``Reactor 2bj'' is corrected to ``Reactor 2eJ.''

Claims (1)

[Claims] Direct current that detects a ground fault in the neutral wire by determining the level of the current flowing in the neutral wire of the power transmission line when a bias current is added to the transmission current of the positive and negative polarity transmission tIi 131 A ground fault detection device for a power transmission neutral line, comprising: a first detection circuit that responds when the current through the grounding point of the neutral line exceeds a predetermined value; and the positive and negative power transmission lines. The second and third detection circuits that respond when the voltage detected on the power transmission side of A ground fault detection device for a neutral line for direct current power transmission, comprising a logic circuit that outputs a signal indicating the occurrence of a line ground fault.