JPH09288141A - Sampling method for control system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sampling method in which the sampling operation of respective terminal processors arranged so as to be distributed is synchronized surely. SOLUTION: A sampling method is provided with a reception circuit 31 which receives time information to be transmitted, by radio waves, to respective terminal processors, with a frequency-signal generation circuit 32, with a PLL circuit 33, with a radio-wave monitoring circuit 34 and with a sample-and-hold circuit 35. When the radio waves are not received, the radio-wave monitoring circuit 34 is operated. By its operation, the sample-and-hold circuit 35 holds the input of a voltage-controlled oscillator 33c at the PLL circuit 33.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to sampling of a control system provided with a plurality of terminal processing devices distributed in a wide range and one central processing device for monitoring each of these terminal processing devices from a distance. Regarding the method.

[0002]

2. Description of the Related Art FIG. 2 shows a control system of this type.
The basic configuration of a fault locator for a transmission line is shown, where 1 is a transmission line, 2 and 3 are circuit breakers, and 4 is a C installed on the side of the circuit breaker 2.
T, 5 are PTs installed on the circuit breaker 2 side, 6 are CTs installed on the circuit breaker 3 side, 7 are PTs installed on the circuit breaker 3 side,
8 is a terminal processing device for monitoring CT4, PT5, etc., 9 is a terminal processing device for monitoring CT6, PT7, etc., 10 is a central processing device, 11 is between the terminal processing device 8 and the central processing device 10. Is a data transmission line, and 12 is a data transmission line between the terminal processing unit 9 and the central processing unit 10.

The fault point locator shown in FIG. 2 has a central processing unit 1 for detecting an accident such as a ground fault at a point A shown in the section between the circuit breaker 2 and the circuit breaker 3 which is a monitored section.
0 is the sampled voltage value of PT5, PT7 as an electric quantity via the terminal processing device 8 and the terminal processing device 9, C
The sampled current values and the like of T4 and CT6 are collected, and the point of the accident is specified by these collected sample values.

In order to locate the above-mentioned failure point, it is necessary that the sampling periods and sampling times of the terminal processing device 8 and the terminal processing device 9 are synchronized. For this reason, conventionally, as shown in FIG. The sampling method was in place. That is, in FIG. 3, the terminal processing device 8
Each of the terminal processing device 9 and the terminal processing device 9 receives the time information transmitted by radio waves from the illustrated artificial satellite or the like.
1 and a sampling signal generation circuit 22 that generates a sampling signal based on the received time information, and samples the electric quantity.

[0005]

According to the above-described conventional control system sampling method, when a flying object such as an airplane intervenes in the radio wave path between the artificial satellite and any of the receiving circuits 21, the radio wave As a result, the signal cannot be received, and as a result, the sampling signal generation circuit 22 does not output the sampling signal, and if the accident as described above occurs at this time, it may be difficult to identify the point of this accident.

An object of the present invention is to provide a sampling method for a control system which solves the above problems.

[0007]

The first invention comprises a plurality of terminal processing devices distributed over a wide range and one central processing device for monitoring each of these terminal processing devices from a distance. In the control system, each of the terminal processing devices samples the amount of electricity to be monitored, which is grasped at each predetermined sampling cycle, and the central processing unit performs arithmetic processing based on these sample values, and the arithmetic processing result is obtained. According to the sampling method of the control system necessary for protecting and controlling each of the monitoring targets, each of the terminal processing devices receives time information transmitted by radio waves and a frequency signal based on the received time information. And a phase-locked loop (PLL) circuit configured to generate the frequency signal by using a phase comparator, a loop filter, and a voltage controlled oscillator. Input to the phase comparator, sample the electric quantity based on the output of the voltage controlled oscillator, and detect the period when the time information is not received and hold the value of the output of the loop filter immediately before the detection. Then, the held value is input to the voltage controlled oscillator.

In a second aspect based on the first aspect, the time information transmitted by the radio wave is time information based on a global positioning system (GPS). According to the present invention, normally, the sampling signal synchronized with the time information is output by the PLL circuit, and the value immediately before the detection of the output of the loop filter of the PLL circuit is held during the period when the time information is not received. By inputting the held value to the voltage controlled oscillator of the PLL circuit and outputting the sampling signal, the sampling signal can be output in a substantially synchronized manner even during the above period without interruption of the sampling signal.

[0009]

1 is a circuit configuration diagram of a terminal device showing an embodiment of the present invention. Each terminal processing device has a receiving circuit 31 for receiving time information from a GPS satellite shown in the drawing, A frequency signal generation circuit 32 that generates a frequency signal based on time information, a PLL circuit 33 that includes a phase comparator 33a, a loop filter 33b, and a voltage controlled oscillator 33c, and a radio wave that detects a period in which the time information is not received. The monitoring circuit 34 and the sample hold circuit 35 that operates by the output of the radio wave monitoring circuit 34 are provided.

In FIG. 1, the illustrated switch of the sample and hold circuit 35 is normally in a closed state, and the receiving circuit 31 and the frequency signal generating circuit 32 allow the GPS satellite 1
A frequency signal having a cycle of 1 second synchronized with the time information issued every second is output. In the PLL circuit 33, the frequency signal is compared with the sampling signal output from the voltage controlled oscillator 33c by the phase comparator 33a. , The phase-compared waveform is smoothed by the loop filter 33b, and the voltage-controlled oscillator 33
c.

According to the sampling method of the control system of the present invention, when a flying object such as an airplane intervenes in the radio wave path between the GPS satellite and one of the receiving circuits 31, the radio wave cannot be received. For example, when the radio wave monitoring circuit 34 for monitoring the level of the received radio wave detects it, the illustrated switch of the sample hold circuit 35 is released,
The output of the sample hold circuit 35 is the loop filter 33.
The value of the output of b immediately before the detection is held, and the held value is input to the voltage controlled oscillator 33c to output the sampling signal.

In the circuit configuration shown in FIG. 1, by inserting a frequency divider (frequency division ratio: N) in the feedback path between the output of the voltage controlled oscillator 33c and the phase comparison circuit 33a, 1 second Synchronized with the time information issued every time (1 /
It is also possible to output a sampling signal of N) second cycle.

[0013]

According to the present invention, normally, the sampling signal synchronized with the time information is output by the PLL circuit, and during the period when the time information is not received, the value of the output of the loop filter of the PLL circuit immediately before the detection. Is held and the held value is input to the voltage controlled oscillator of the PLL circuit to output the sampling signal, so that the sampling signal is not interrupted and the substantially synchronized sampling signal can be output even in the above period. Therefore, for example, as a failure point locating device, it becomes possible to always specify the point of the accident.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration example of this type of control system.

FIG. 3 is a circuit configuration diagram showing a conventional example.

[Explanation of symbols]

 1 Transmission Line 2,3 Circuit Breaker 4,6 CT 5,7 PT 8,9 Terminal Processing Unit 10 Central Processing Unit 11,12 Data Transmission Line 21 Reception Circuit 22 Sampling Signal Generation Circuit 31 Reception Circuit 32 Frequency Signal Generation Circuit 33 PLL Circuit 33a Phase comparator 33b Loop filter 33c Voltage controlled oscillator 34 Radio wave monitoring circuit 35 Sample and hold circuit

Claims (2)

[Claims] 1. A control system comprising a plurality of terminal processing devices distributed in a wide range and a central processing unit for monitoring each of these terminal processing devices from a distance. Each sampled the amount of electricity to be monitored, which is controlled by each predetermined sampling period, and the central processing unit performs arithmetic processing based on these sample values,
In the sampling method of the control system necessary for protecting and controlling each of the monitored objects based on the result of the arithmetic processing, each of the terminal processing devices receives time information transmitted by radio waves, and the received time information Based on a phase-locked loop (PL) composed of a phase comparator, a loop filter and a voltage controlled oscillator.
L) is input to the phase comparator of the circuit, samples the electric quantity based on the output of the voltage controlled oscillator, and detects the period when the time information is not received, and detects the output of the loop filter immediately before the detection. Holds the value of
A sampling method for a control system, wherein the held value is input to the voltage controlled oscillator. 2. The sampling method for the control system according to claim 1, wherein the time information transmitted by the radio wave is time information by a global positioning system (GPS). .