JPS62250816A - Current differential relay 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] [Field of Industrial Application] The present invention relates to a current differential relay device that detects an abnormality in a power system by comparing current values sampled simultaneously at remote locations and performs a predetermined operation. More specifically, the present invention proposes a current differential relay device that has an enhanced ability to detect errors in signals being transmitted.

[Prior art]

2. Description of the Related Art A current differential relay device is known that measures current at two remote points on a power transmission line and compares the current to check whether there is an abnormality in the power transmission system.

Japanese Patent Publication No. 57-9292 shows an example of such a device. This will be explained below based on FIG.

Electrical stations A and B, such as substations, are connected to the power transmission line l via their respective busbars 4.4. The power transmission line 1 is equipped with a terminal breaker 2.2 for disconnecting between electric stations A and B, and the W of the power transmission line 1 is connected between the terminal breaker 2.2 and the connection part of the bus 4.4.
Current change to detect the first current! 13°3 is provided.

The current transformer 3 of the electric station A outputs a secondary current corresponding to the current IA flowing through that part, and this output current is converted by the input converter 5 into an electrical signal IA2 of a level passed to the subsequent circuit, This electrical signal IA2 is given to a sampling circuit 6 and sampled at a constant cycle, further converted into a PCH digital signal by an A/D (analog/digital) conversion circuit 7, modulated by Tsushin ff13, and then sent to the communication line. 15, and is transmitted to the communication device 13 of electric station B.

The electrical signal IA2 is also input to a transmission delay delay circuit 12 which delays it by the time required for communication between the electrical stations A and 8.
Here, it is output as a delayed electric signal IAI (its current value information is the same as IA2), and is input to the relay determination section 14.

Electrical station B is also equipped with a device similar to that described above, and the communication device 13 is connected to electric station A via a communication line 15.
Electrical signal IB2 transmitted to (current transformation at electric station B!
A signal corresponding to the current IB flowing through the s3 installation part) is received by the communication device 13 of electric station A, demodulated, and then sent to D.
/A Provided to the (digital/analog) conversion circuit 9. The analog output of the D/A conversion circuit 9 is sent to the reception filter 8.
The high frequency associated with D/A conversion is removed by the relay determination unit 1.
0 Electrical signal IB received by communication device 13 given to 4
2 is also input to the error detection circuit 11, where data error detection such as level drop detection, parity check, and cyclic code check of the transmitted digital signal is performed.
If a data error is detected, the lock signal generation circuit 10
and sends a lock signal to the relay determination unit 14 to prohibit its output.

On the electric station B side, the above-mentioned receiving side circuit also has a similar configuration. This current differential relay device is provided with a sampling synchronization control circuit (not shown) so that the sampling circuits 6.6 of both electric stations perform sampling at the same time. Therefore, the relay determination unit 14.14 is the electric station A at the same time.

The instantaneous value of the current at B IAI, In2 or IBI, I
A2 will be input.

Note that IBI transmits the electric signal IB2 to the transmission delay compensation circuit 12.
This is an electrical signal delayed by .

The relay determination unit 14 compares the instantaneous values of both currents, and based on the magnitude and phase relationship, determines the protection zone, that is, the electrical station A-
It is determined whether the fault is an outside-section fault due to the gap fault between B, and if it is determined that there is a fault, a break control output is issued to each of the terminal breakers 2 and 2 to remove the fault.

Although there are factors that cause data errors in the communication line 15 due to disturbances, etc., if a data error is detected in the error detection circuit 11, a lock signal is generated and the relay determination unit 1
4, that is, the output that should trip the terminal breaker 2.2, is prohibited.

In the conventional current differential relay device as described above, error detection such as a parity check is performed using the signal itself transmitted from another electric station. Therefore, even if an error is detected, it cannot be determined that the transmitted information has been disturbed in the communication line; for example, the A/D conversion circuit 7 may be defective. Therefore, if the output of the relay determining section 14 is locked based on the result of such error detection, the original protective function cannot be achieved, and there is a possibility that the failure will spread.

FIG. 7 shows a conventional device that enables comprehensive error detection including the A/D conversion circuit 7. In the figure, 16 is a constant voltage generation circuit, and its output voltage E is measured by a sampling circuit 6.
The signal is sent together with the output to the A/D conversion circuit 7, where it is converted into a digital signal and transmitted as before. The signal transmitted in this manner is converted into an analog signal by a D/A conversion circuit 9 on the receiving side so that only the instantaneous current value is output, and is input to the relay determination section 14 via the reception filter 8. On the other hand, the received signal is also input to the voltage detection circuit 17, which detects whether the received voltage data is the output voltage E of the constant voltage generation circuit 16,
If this is not E, a predetermined output is given to the relay determining section 14 and the output is locked.

[Problem that the invention seeks to solve]

In the conventional device described above, the output voltage of the constant voltage generating circuit 16 fluctuates due to aging and temperature changes in its components, so the voltage detecting circuit 17 may erroneously issue a lock signal. In order to avoid malfunctions, it is necessary to increase the detection margin in the voltage detection circuit 17, which causes problems such as an unavoidable decrease in detection sensitivity.

The present invention was made to solve these problems, and it transmits the instantaneous value and effective value of AC voltage together with the instantaneous current value, and uses this AC voltage information to detect only disturbances in the communication line. It is an object of the present invention to provide a current differential relay device that can perform reliable circuit protection.

[Means for solving problems]

Current differential j! according to the present invention ! The electrical device includes means for sampling an alternating current voltage and means for calculating an effective value of the alternating voltage, and also calculates the effective value of the alternating voltage from the alternating voltage sampling value of the signal transmitted from the other end. means for comparing the calculated AC voltage effective value with the transmitted AC voltage effective value, and a relay determination unit that prohibits relay output if a substantial discrepancy is found in the comparison results. be.

[Effect]

While determining the presence or absence of a failure by comparing the instantaneous value of the il current transmitted from the other end with the instantaneous current value detected at the own end,
The AC voltage effective value is calculated using the transmitted AC voltage sampling value. This calculated effective value is compared with the transmitted AC voltage effective value. If there is a data error due to a disturbance in the communication line, there is virtually no possibility that the two effective values will match. Therefore, if a mismatch between the two effective values is detected, it is assumed that there is a disturbance in the communication line and the process is continued. Locks the power judgment unit output. On the other hand, if both effective values match, there is no possibility of data errors due to disturbances in the communication line, so the output of the relay determination unit based on the instantaneous current values of both electric stations is not locked.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on drawings showing embodiments thereof.

FIG. 1 is a block diagram of a current differential relay device according to the present invention. Electrical stations A and B are connected to the power transmission line 1 via respective busbars 4.4, and the power transmission line 1 is equipped with a terminal breaker 2.2 for disconnecting electric stations A and B. vessel 2,2
A current transformer 3.3 for detecting the current of the power transmission line 1 is provided between the connection point of the busbars 4 and 4.

Current transformation at electric station A! 53 outputs a secondary current corresponding to the current IA flowing through that part, and this output current is converted into an electrical signal rA2 at a level passed to the subsequent circuit at the input conversion N5, and this electrical signal IA2 is sent to the sampling circuit 6. given to. 18 is an AC power supply, the voltage of which is given to the sampling circuit 6 and the effective value calculation circuit 19. The sampling circuit 6 samples the re-input at a constant cycle,
The sampled value is converted into a PCH digital signal by an A/D (analog/digital) conversion circuit 7 and provided to a synthesis circuit 20. The effective value calculation circuit 16 calculates the effective value VAI? of the AC voltage using a method described later. Calculate. The calculated effective value VAR is input to the synthesis circuit 2o, and the instantaneous current value IA2, the sampling value of the AC voltage, and the effective value V
The IIR is combined in an appropriate format and input to the communication device 13, where it is modulated and transmitted to the communication device 13 of electric station B via the communication line 15. Such a configuration is the same on the electric station B side, and the instantaneous current value IB2 of the current In detected by the current transformer 3 and the sampled value and effective value of the AC voltage are transmitted to the communication device 13 to the electric station. The composition is as follows.

FIG. 2 is an explanatory diagram of the effective value calculation method. The instantaneous value of the AC voltage is sampled every 30 degrees of electrical angle, and the time series data is expressed as v(tl, v(t-1), V(t-2)).

v (t-3)..., then the effective value V is the current sampling value V([) and the three previous sampling value v(t-
3), v=7 (v(tl)2+(v(t-3))2) can be obtained.

The electrical signal IA2 is also input to a transmission delay delay circuit 12 which delays it by the time required for communication between the electrical stations A and 8.
Here, it is output as a delayed electrical signal IAI (its current value information is the same as !^2), and is input to the relay determining section 14.

From electric station B, the instantaneous value I of the detected current IB of the current transformation s3
The communication device 13 to which B2, the sampling value of the voltage of the AC power source 18, and the effective value VOR are transmitted receives and demodulates the received signals, and sends the demodulated signal to the D/A conversion circuit 9. It is given to the effective value calculation circuit 21 and the effective value extraction circuit 22.

The D/A conversion circuit 9 converts only the instantaneous value TB2 into an analog signal and supplies this to the relay determination section 14 via the reception filter 8.

The effective value calculation circuit 21 calculates the effective value VBRI from the voltage sampling value using a method similar to that described above, and provides this to the error detection circuit 23. The effective value extraction circuit 22 extracts only the effective value VOR from the received signal and supplies it to the error detection circuit 23. The error detection circuit 23 compares the input VOR and VBRI, and if they match, it does not output anything, and if they do not match, it outputs the relay determination unit 14.
A predetermined output is emitted to.

The relay determination unit 14 uses the input instantaneous value IA1. Based on the magnitude 9 phase relationship of IO2, the protection zone, that is, the electrical station A-
It is determined whether the fault is within the section B or outside the section, and if it is determined that there is a fault within the section, a cutoff control output is issued to each terminal cutoff s2゜2 to remove the fault, but the error detection circuit 23
If the output is generated, it is assumed that there is a disturbance in the communication line 15 and the output is prohibited.

The receiving circuit on the electric station B side has the same configuration, and I
BI is a current instantaneous value signal obtained by delaying IO2 in the transmission delay compensation circuit 12, and VARI is calculated by the effective value calculation circuit 21 of electric station B based on the sampled value of the AC voltage transmitted from electric station A. This is the effective value.

Although not shown, a sampling period control circuit is provided for synchronizing the sampling period of the sampling circuits 6.6 of both electrical stations. Further, the present invention does not preclude the use of a conventional error detection circuit that performs a parity check.

FIG. 3.4 is a block diagram showing an example of the configuration of the error detection circuit 23 and the relay determination section 14. 141 in Figure 3
is a differential calculation circuit using IAI and 1B2 as two-man power, and the differential output thereof is inputted to the level detection 1143 via the zero control circuit 142. If there is no output from the error detection circuit 23, the differential output is directly input to the level detection circuit 143, where it is compared with a predetermined dark value, and if it exceeds the threshold value, it is determined that there is an abnormality in the power transmission line l, and the terminal circuit breaker 2, 2 The level detection circuit 143 outputs an output to operate the circuit. 1!4 detection circuit 23 output is zero control circuit 1
42, and the error detection circuit 23 is a two-man power VB.
When a mismatch between R and VBRI is detected and output, the zero control circuit 142 outputs zero regardless of the differential output of the differential calculation circuit 141, and as a result, the level detection 5143 detects the circuit breaker 2.
2 does not output the signal that should operate it.

In the example shown in FIG. 4, a difference calculation circuit is used as the error detection circuit 23 instead of a comparator as described above.

That is, this error detection circuit detects the digital effective value signal VBR.
, VBRI and converts it into an analog value, and this analog output VBR2 is input to a three-person differential calculation circuit 145. The differential arithmetic circuit 145 has the current IAI, 182 inputted in addition to this input,
The analog output BR2 is used to suppress the differential output between IAl and IO2. Such a differential calculation circuit 14
5 output is input to the level detector 143, compared with the same threshold value as before, and outputs an operation control signal for the circuit breaker 2.2. In this example, the output of the error detection circuit 23 is 2 VBR, VBR
When the difference VBR2 of I becomes large, the output of the differential arithmetic circuit 145 is made small, and as a result, the operational output of the circuit breakers 2, 2 is prohibited.

FIG. 5 shows an instrument voltage transformer (PT) 2 that detects the voltage of the power transmission line 1 in place of the AC power supply 18 in the embodiment shown in FIG.
5 is used, and is input to the sampling circuit 6 and the effective value calculation circuit 19 directly or via an input transformation circuit (not shown) for level adjustment. This embodiment has the advantage of not requiring a special AC power source.

Note that in the above embodiment, the effective value calculation circuit 21, effective value extraction circuit 22, etc. are described as being constituted by separate circuits, but it is also possible to have the digital signal processing part performed by a microprocessor. Of course.

〔effect〕

In the case of the device of the present invention as described above, data errors are detected by comparing the AC voltage effective value calculated based on the AC voltage sampling value transmitted from the other end with the AC voltage effective value also transmitted from the other end. Since the detection is carried out, it is possible to reliably detect when the transmitted signal is affected by disturbances in the communication line, and therefore, it is possible to prevent the circuit breaker from accidentally locking when it should be operated due to a fault in the current circuit, causing serious damage. This eliminates the possibility of causing malfunctions.

[Brief explanation of drawings]

Fig. 1 is a block diagram of the device of the present invention, Fig. 2 is an explanatory diagram of the effective value calculation method, Figs. 3 and 4 are block diagrams showing the configuration of the error detection circuit and relay judgment section, and Fig. 5 is A block diagram showing an embodiment, FIG. 6.7 is a block diagram of a conventional device. 1... Power transmission line 2... Terminal breaker 3... Current transformer 4... Bus bar 6... Sampling circuit 13...
Communication device 14...Relay determination unit 15...Communication line
Engineering 8...AC power supply 19.21...Effective value calculation circuit
20... Synthesis circuit 22... Effective value extraction circuit 23
...Error detection circuit The same reference numerals in the figures indicate the same or corresponding parts. Patent Applicant Mitsubishi Electric Corporation Agent Patent Attorney Masuo Oiwa and 2 others V2 = V
2(t) + V2(t-3) 2nd sword

Claims (1)

[Claims] 1. Convert instantaneous current values sampled synchronously at multiple current detection ends of the power system into digital signals and transmit them to the other end, and compare the transmitted instantaneous current values at the other end with the In a current differential relay device that compares the current instantaneous value at the end and detects an abnormality in the power system based on the comparison result and operates in a specified manner,
means for sampling a predetermined AC voltage in synchronization with the sampling; means for calculating the effective value of the AC voltage; and means for transmitting the instantaneous current value, the AC voltage sampling value, and the AC voltage effective value to the other end. , means for calculating an AC voltage effective value based on the AC voltage sampling value transmitted from the other end, and comparing the AC voltage effective value calculated by the means with the AC voltage effective value transmitted from the other end. 1. A current differential relay device comprising: error detection means for detecting a substantial discrepancy between the two effective values; and a relay determination section for prohibiting the predetermined operation when the error detection means detects a substantial discrepancy between the two effective values. 2. The relay determination section includes a differential arithmetic circuit that inputs the instantaneous current values of the own end and the other end, and an error detection means that sets the output of the differential arithmetic circuit to zero when the error detection means detects a substantial mismatch between the two effective values. 2. A current differential relay device according to claim 1, comprising means for: 3. The relay determination unit includes a differential calculation circuit that inputs instantaneous current values at one end and the other end, a determination circuit that determines whether there is an abnormality in the power system based on the output of the differential calculation circuit, and error detection means. Claim 1, further comprising a circuit that prohibits output from the determination circuit when a substantial discrepancy between the two effective values is detected.
The current differential relay device described in . 4. The current differential relay device according to claim 1 or 2, wherein the AC voltage is a voltage obtained based on the power system.