JPS5970118A - Protecting relay unit 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 protective relay device that protects a DC transmission line from accidents according to currents detected from both ends of the DC transmission line.

Conventionally, there has been a device of this type as shown in FIG.

The AC system 1a is a three-phase full-wave bridge converter (REC) 2
a, a DC reactor 3a, a DC transmission line 4 to be protected, a DC reactor 3b, and a converter with the same configuration as the converter 2a (
INV) 2b to the AC system 1b, forming a DC power transmission system. A return wire 6 is connected between the converters 2a and 26, and the return wire 5 on the converter 2a side is grounded. converter 2
a.

2b and the return line 5 is a direct current transformer 6a in order to detect the current flowing through it.

6b is provided, and its output voltage is controlled by a control device 7a.

7b. The control devices 7a and 7b also receive addition signals from adders 8a and 8b as control inputs, which will be described below, and transmit the control signals to the converter 2 according to these inputs.
a, 2bK supply. Setting devices ga and gb are connected to DC power line 4
The reference signal ΔI that sets the current margin of the switch IQ
A and 10b are input to adders 8a and 8bK with negative polarity. The setting device 11 includes a reference signal Iref serving as a current command value for the DC current of the DC power transmission line 4, a switch 10a,
It outputs a switch signal for opening and closing tOb.

The reference signal Iref of the setter [11 is directly inputted with positive polarity to the adder 8b, and also inputted with positive polarity to the adder 8a via the transmission devices 12a and 12b. Transmission device 12a, 1
2b transmits a switch signal from the setting device 11 to the switch 10a. The transmission devices 13a and 13b are DC transformers 1
The DC current signals detected at both ends of the DC power transmission line 40 are transmitted to each other via the protective relays 15a and 15b.
b. The protective relays 15a, 15b are connected to their own ends, that is, the signals of the DC/AC transformers 14a, 14b, and the transmission device 1.
3a, 13b to the other end, that is, the DC transformer 1
4b and 14a, and then a cutoff signal Ka for protecting the DC transmission line 4 from an accident by the operation described.
, Kb is a so-called differential protection relay.

Explain the operation. FIG. 2 is a graph showing the voltage versus current characteristics of the converters 2a, 2b. Ed indicates the DC voltage of the DC transmission line 4, Id indicates the DC current of the DC transmission line 4, and N indicates the operating point of the DC current IN and the DC voltage Va at normal i. That is,
In normal times, the DC voltage V is applied via the DC transmission line 4 and the return line 5.
A DC current IN flows, and the DC power transmission system is stable with the intersection N as the operating point.

However, when a ground fault F occurs as shown in Fig. 1, the operating point shifts to Fa and Fb shown in Fig. 2, and flows through the DC current transformers 14a and 14b to A2 in Fig. 3. Direct currents IN and IR shown flow. DC current IN.

The IR is input as a signal to protective relays 15a and 15b via DC transformers 14a and 14b. The protective relays 15a and 15b output cutoff signals Ka and Kb when the conditions expressed by the following equations are satisfied for a predetermined period of time.

IA −IB≧＠ΔI・・・・・・・・・・・・
・(1) Here, K is a constant, and K・△■ is shown in Figure 3 (
) has the value shown. In this case, a ground fault may occur as shown in Figure 3 (
Equation (1) is satisfied from time t1 shown in c), and)
Since this continues for a predetermined period of time as shown in (e), the protective relays 15a and 15b output cutoff signals Ka and Kb from time t2 as shown in (e).

FIG. 4 is a graph showing the ratio characteristics of the device shown in FIG. The shaded area in the figure indicates the operating range, and b is IB (=I
A - △ engineering), C is the operating characteristic at steady state, d is IB (=IA
) are shown respectively.

Normally, K・△■ has a small value compared to IN and IRK, and △■ is the DC current IR when the reference signal Iref of the setting device 11 is set to a value near the rated value.

It is about 10% of INK. When the constant K is set to about 0.5, K·ΔI needs to be set to about 5% of the rated current. Such settings are extremely sensitive to errors in each part of the device.

A conventional protective relay device is configured as described above.
Errors in various parts of the equipment, such as starting and stopping power transmission, can easily result in K.
Since ΔI reached a value exceeding the accident judgment level, there was a drawback that malfunctions were likely to occur.

This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and it uses a judgment method to detect the occurrence of an accident when the current command value for a DC transmission line rarely changes or when the power flow is reversed. To provide a protective relay device for a DC power transmission line that can increase operational reliability without reducing sensitivity to accidents since the occurrence of an accident is determined by adding a suppression term to the conditions. The purpose is to

An embodiment of the present invention will be described below with reference to the drawings. Fifth
The figure is a block diagram of the protective relay device according to the present invention.
The same reference numerals as in the figures indicate the same or equivalent parts. The detection circuits 16a and 18b are the output terminals of the setting device 11 and the transmission device 1.
At the output terminal of 2b, the current setting value, that is, the reference signal Ire
This circuit makes the output signal high when it detects that f is equal to or greater than a predetermined value. Detection circuits 17a and 17b are output terminals of setting device 11.

This circuit makes the output signal high when it detects a change in power flow, that is, a switch signal is outputted at the output end of the transmission device 12b, and when a predetermined value or more is detected. Detection circuits 16a, 17a, 16b, 17Lz7
) Output signals are inputted to protective relays 15b, 15a via ORG) 18a, 18b.

Next, the operation will be explained. Setting device 110 reference signal I
The value of ref changes at startup, stop, when the current command value is changed by a command staff, and at the time of operation of the constant power control device 1 frequency control device (not shown). When it is detected that this change is equal to or greater than a predetermined value, the detection circuits 16a, 1
The output signal of 6b becomes high, and 18a, 1
It is input to protective relays 15a and 15b via 8b.

In response to this, the protective relays 15a and 15b perform the following determination.

IA −IB≧Kl・ΔI+η・K2 ・・・・・・
(2) However, η is "1" when the output signals of the detection circuits 17a and 17b are high, and is "0" when the output signals are low. K2 is a constant, and η·K2 is a suppression term. In this case, since η=1, the determination condition is stricter than the equation (1) of the conventional device where η=0.

FIG. 6 is a graph showing the ratio characteristics of the device shown in FIG. a indicates the operating characteristic when the current command value is changed or when the power flow is reversed, b indicates IB (=IA-ΔI), C indicates the operating characteristic during steady state, and d indicates In (=IA). The difference between the operating characteristics a and C depends on the presence or absence of the suppression term η·K2.

In addition, if a converter arm short circuit, ground fault, commutation failure, etc. occurs as a failure other than the DC transmission line 4, the voltage of the DC transmission line 4 will drop, so in such a case, the The operation of the device of the present invention can be locked by the responsive output of the ground fault detection device, the arm short circuit failure detection device, or the commutation failure detection device, and erroneous output can be prevented.

In addition, in the above embodiment, the determination formula is 1ΔI+η・K2
However, even if the equation (2) is modified to (K1+η·K2)·ΔI, etc., the same effect as in the above embodiment can be obtained.

As described above, according to the present invention, a suppression term is added to the judgment conditions so that the judgment conditions for detecting the occurrence of an accident become stricter when there is a change in the current command value or when the power flow is reversed. This has the effect of increasing operational reliability without reducing sensitivity to accidents.

[Brief explanation of the drawings] Fig. 1 is a block diagram of a conventional protective relay device, Fig. 2 is a graph of the operating characteristics of the converter shown in Fig. 1, and Fig. 3 is a graph of the protective relay shown in Fig. 1. 4 is a graph of the operating characteristics of the protective relay device shown in FIG. 1; FIG. 5 is a block diagram of the protective relay device according to an embodiment of the present invention;
FIG. 6 is a graph showing the operating characteristics of the protective relay device shown in FIG. la, 1b... AC system, 2a, 2b... converter, 4... DC transmission line, 7a, 7b... control device,
8a, 8b...control device, ga, gb...
Setting device, 12a, 12b, 13a, 13b
--...Transmission device, 15a, 15b...Maintenance relay,
16a, tab, 17a, 17b-detection device, 1Ba, 18b...OR gate. Note that the same reference numerals in the figures indicate the same or equivalent parts. Agent Nobu Kuzuno - (and 1 other person) 4th cause No. B) ■8 Procedural amendment (voluntary) Commissioner of the Japan Patent Office 1, Indication of case Patent application No. 181012/1989 2, Issue 1171 (7) people '4 Protection relay device for DC transmission lines 3, Person making the amendment 5, Details of the detailed description of the invention in the specification subject to amendment 6, Contents of the amendment (1) Page 4, line 5 of the specification, In the 7th line, [DC electric current V
aJ is corrected to ``DC voltage VdJ.'' (2) On page 4, line 13 to line 14 of the specification, ``DC currents IN and IR flow. [DC currents IA and IR flow. DC current IA. "Ill," he corrected. (3) Page 5, line 7 of the specification, page 8, lines 2 to 3
The line says [1g(=IA-ΔI)J.
A-ΔI”. (4) [I
R(=IA) J is corrected as IR=IAJ. (5) On page 5, line 9 of the specification, [js, Ia J] is corrected to [IA, IB J.

Claims (1)

[Claims] Outputs a logical detection signal when the current command value signal supplied as a control input to the AC/DC or orthogonal conversion converter installed at the own end and the opposite end of the DC transmission line exceeds a predetermined reference level. a first detection circuit that outputs a logical detection signal when a power flow change signal supplied as a control input to the converter exceeds a predetermined reference level;
and a logic circuit for ORing the detection signals of the first and second detection circuits in correspondence with the own end and the opposite end, respectively, and one logic circuit of the own end and the opposite end. The output signal and the DC current value detected from the own end are input, and the circuit is set based on a predetermined logic so that when the output signal of the logic circuit is energized, an accident in the DC transmission line is detected. A protection relay device for a DC power transmission line, comprising a protection relay that sets a high determination level, determines the level of the DC current value based on the determination level, and generates a protection operation signal for the DC power transmission line.