AU634557B2

AU634557B2 - Distribution line monitoring system

Info

Publication number: AU634557B2
Application number: AU58661/90A
Authority: AU
Inventors: Masaaki Kano; Toshihito Kunieda; Akimichi Okimoto
Original assignee: NGK Insulators Ltd
Current assignee: NGK Insulators Ltd
Priority date: 1989-07-04
Filing date: 1990-07-03
Publication date: 1993-02-25
Anticipated expiration: 2010-07-03
Also published as: KR930010687B1; AU5866190A; KR910003893A; JPH0340722A

Description

AUSTRA IA 635 PATENTS ACT 1952 Form COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE Short Title: Int. Cl: Application Number: Lodged: Complete Specification-Lodged: Accepted: Lapsed: Published: 0a Priority: Related Art: TO BE COMPLETED BY APPLICANT Name of Applicant: NGK INSULATORS, LTD.

Address of Applicant: 2-56, SUDA-CHO, MIZUHO-KU, o NAGOYA CITY,

JAPAN

Actual Inventor: Address for Service: GRIFFITH HACK CO., 601 St. Kilda Road, Melbourne, Victoria 3004, Australia.

Complete Specification for the invention entitled: DISTRIBUTION LINE MONITORING SYSTEM.

The following statement is a full description of this invention including the best method of performing it known to me:- L i

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DISTRIBUTION LINE MONITORING SYSTEM BACKGROUND OF THE INVENTION Field of the Invention The present invention relates generally to an electrical distribution line monitoring system that permits a master 0 0o station to monitor remote terminal units that control discrete portions of the distribution line. More particularly, a monitoring system is disclosed that maintains communication with operational remote terminal units even upon the occurrence of a control line or remote terminal failure.

Related Art Conventionally, loop type electrical distribution lines for supplying electrical power from a substation to users is segmented by a plurality of line switches. Remote terminal units are provided in association with these switches. A master station is loop-connected in series to the remote terminal units by optical communication lines, not electric signal lines. This provides stable communication with less noise therebetween. The master station sequentially communicates with the remote terminal units to supervise the status of the line in each section, and opens the switch for any section in which a distribution failure has occurred to isolate the failed section from the orderly sections.

However, conventional line monitoring systems have several drawbacks. Specifically, if the optical communication lines are damaged or cut, or if the optical signals deteriorate for any reason (as for example due to a disabled signal input or a poor connection), then the master station can neither monitor nor control all of the remote terminal units connected thereto.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a distribution line monitoring system which, upon occurrence of a failure in the optical communication lines or a particular remote terminal unit, can maintain communication with all the unaffected remote terminal units.

According to the present invention there is provided an electrical distribution line monitoring system comprising a master station and a plurality of remote terminal units for controlling discrete sections of the electrical distribution line, the master station and remote terminals being connected in series by each of a pair of looped optical communication lines that normally transmit optical signals in opposite directions, each remote terminal unit including: a photo-electric communication device coupled to both of the optical communications lines, such that each optical communication line is optically coupled to an associated light emitting diode for outputting an optical signal to the photoelectric communication device of an adjoining remote terminal unit based on a first electric signal, and, a photodiode for converting an optical signal from an adjoining remote terminal unit into a second electric signal and outputting said second electric signal to its associated light emitting diode; a pair of comparators for detecting an optical signal transmission failure, each comparator being associated with a particular photodiode to monitor the level of the optical signals converted by the associated photodiode and outputting -2-

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a fault detection signal when the monitored signal falls below a predetermined threshold level; a pair of relay circuits for opening respective normally closed contacts on a side of each comparator opposite its corresponding photo diode to switch the communication path of the electric signal outputted by one of the photodiodes from the light emitting diode associated with one of the optical communication lines to the light emitting diode associated with the other of the optical communication lines to reverse a transmission path of the optical signals in accordance with the reception of the fault detection signal from the comparators; a line switch for segmenting the electrical distribution line into ones of said discrete sections; a switch actuator means connected to the line switch for selectively opening and closing the line switch; a detector associated with a line section for detecting a malfunction in that line section; and, a controller connected to said photo-electric communication device, for driving the switch actuator means, in accordance with a status signal outputted by the detector.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a diagram illustrating a distribution line and a .system of monitoring the same according to the present invention.

V Fig. 2 is a block circuit diagram showing the electric structure of a master station.

3 It err¢ tr Fig. 3 is a block circuit diagram showing the electric structure of remote terminal units.

Fig. 4 is an electric circuit diagram illustrating photoelectric communication devices provided in the respective remote terminal units.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of a distribution line monitoring system of this invention will now be described referring to o, o c the accompanying drawings.

0 0.

o o 10 Fig. 1 illustrates an example of a loop type electrical distribution system which is monitored by a master station 1.

-o An electrical distribution line 2, which is supplied with power from a substation H, is connected with line switches SSI to SSn and remote terminal units (hereinafter referred to as RTUs K1 to Kn. The line switches SS1 to SSn segment the S° 0% distribution line 2, and enable or disabled these line sections. The RTUs Ki to Kn control the switching of the line switches SS1 to SSn, respectively, and collect line information. The RTUs K1 to Kn are connected in series to the master station 1 by a pair of optical communication lines 3 and 4 via photo-electric communication devices.

Referring to Fig. 1, one of the communication lines, 3 constitutes a counterclockwise transmission path from the master station 1, while the other optical communication line 4 constitutes a clockwise path from the master station 1. Both communication lines 3 and 4 are looped to return to the master station 1.

As shown in Fig. 2, the master station 1 includes a photoelectric communication device 5, a central processing units (CPU) 6, a random access memory (RAM) 7, and a read only memory (ROM) 8. Control and operation programs are stored in "0 the ROM 8. The CPU 6 performs an operation on various types of input signals according to the programs in ROM 8, and o a accumulated data or renewed data as the result of the operation is temporarily stored in the RAM 7. Using a data frame that classifies these pieces of data according to the functions, the CPU 6 can communicate with the RTUs KI to Kn by way of the photo-electric communication device 5 to identify each RTU signal.

As illustrated in Fig. 3, RTUs Ki to Kn each include a switch actuator 9, a line fault detector 10, a controller 11, and a photo-electric communication device 12. The switch actuators 9 open and close the line switches SS1 to SSn. The detector includes an optical sensor to detect a phase current, a phase voltage or a zero-phase component of the distribution line 2.

The controller 11 performs an operation on command signals as well as sensor signals which are associated with the actuator 9 and the detector 10. The communication device 12 communicates with the master station 1 by way of the communication lines 3 and 4, and relays a command signal from the master station 1 or a response signal to the master station 1 to the controller 11.

Fig. 4 illustrates the communication devices 12 of the respective RTUs KI to Kn. In Fig. 4, of the RTUs K1 to Kn, only RTUs K9 to K11 are shown. Each communication device 12 includes photodiodes PD1 and PD2 which convert an optical signal to an electric signal, and light emitting diodes LED1 and LED2 which convert an electric signal to an optical signal. The photodiodes PD1 and the light emitting diode LED1 are connected to the counterclockwise communication line 3, while the photodiode PD2 and light emitting diode LED2 are connected to the clockwise communication line 4.

The photodiode PD1 is connected to the controller 11 via an optical signal detector 13, which includes a comparator for electrically measuring a level of the light signal input to the photodiode PD1 from the communication line 3, and a normally closed contact 14b of an input switch 14. The light emitting LED1 is likewise connected to the controller 11 via a normally closed contact 15b of an output switch The photodiode PD2 is connected to the light emitting LED2 via an optical signal detector 16, which includes a comparator for electrically measuring a level of the light signal input from the communication line 4 to the photodiode PD2, and a normally closed contact 17. The output terminal of a normally open contact 15a of the output switch 15 is connected between the light emitting diode LED2 and the contact 17. The output terminal of a normally open contact 14a of the switch 14 is connected between the detector 16 and the contact 17.

The detector 13 is connected to an input contact switching device 18 comprising a relay circuit. When the detector 13 can not detect a sign input from the communication line 3, or when the level of the input signal dose not reach a predetermined level, the detector 13 outputs a low reception-level signal to the switching device 18. In response to this signal, the switching device 18 energizes/deenergizes the contact 14a, 14b as well as contact 17 so as to operate to selectively perform the opening/closing of the contact 14a, 14b and the contacts 17.

Likewise, the signal detector 16 is connected to an output contact switching device 19 comprising a relay circuit. When the detector 16 can not detect a signal input from the communication line 4, or when the level of the input signal dos not reach a predetermined level, the detector 16 outputs a low reception-level signal to the switching device 19. In response to this signal, the switching device 19 operates to 7 selectively execute the opening/closing of the contact and contact 17.

The switching device 18 and the switching device 19 are connected to the controller 11, so that the operation signal from the switching devices 18 and 19 are input to the controller 11.

The action of the distribution line monitoring system with the above structure will now be described. To begin with, a

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description will be given regarding the case where the optical '0 communication lines 3 and 4 function properly.

o n In each of RTUs K9 to K11 shown in Fig.4, the optical signal from the counterclockwise communication line 3 is input to the 0000 n photodiode PD1 where it is converted into an electric signal.

The electric signal is sent to the controller 11 via the 1 0 0 5 contact 14b. At this time, the detector 13 does not output the operation signal to the switching device 18.

0 0 The controller 11 outputs the command signal to the switch actuator 9 for each of the line switches SS9 to SS11 in accordance with the control signal from the master station 1, and outputs the response signal to the master station 1 after performing an operation upon the input data from the detector These signals are supplied through the contact 15b to the light emitting diode LED1 where they are converted into optical signals. The optical signals travel counterclockwise through the communication line 3.

The optical signal from the clockwise communication line 4 is transmitted to the photodiode PD2, which in turn converts it into an electric signal. This electric signal is sent via the contact 17 to the light emitting diode LED2 where it is converted into an optical signal. The optical signal travels S clockwise through the communication line 4. In this 0 embodiment, the signal from the clockwise communication line 00 0 "i0O 4 only passes through the communication device 12 and is not S" input to the controller 11.

0 0 A description will now be given regarding the case where, for example, faults occur in both communication lines 3 and 4 at f ill the same point between the RTUs K9 and In the RTUs K1 to K9, the signal input from the clockwicommunication line 4 to the photodiode PD2 is inhibited or Lg level decreases. This drives the detector 16 to output the low reception level signal to the switching device 19. As a result, the switching device 19 closes the normally open contact 15a and opens the normally closed contact 15b, and opens the normally closed contact 17 to inhibit the signal input to the light emitting diode LED2.

In the RTUs K1 to K9, the signal from the counterclockwise communication line 3 is input to the cu -roller 11 by way of the photodiode PD1 and the contact 14b as in the case of the proper function. The signal from the controller 11 is therefore sent to the light emitting diode LED2 through the contact 15a, which has been closed, and the output signal from each of the RTUs Ka to K9 is reversed and the signal travels clockwise through the communication line 4.

In the RTUs K10 to Kn, the input signal from the coloo counterclockwise communication line 3 to the photodiode PD1 is disabled or its level decreases. This driver the detector 0 o o 13, and the low reception level signal is sent to the o switching device 18. Then, the switching device 18 closes the contact 14a instead of the contact 14b, and opens the contacts o 17, thereby disabling the signal input to the light emitting 5 diode LED2.

00 The signal from the clockwise communication line 4 is output via the closed contact 14a to the controller 11 from photodiode PD2, as in the case of the proper function. As a result, the signal from the controller 11 is output by way of the contact 15b to the light emitting diode LED1. As the signal input to the RTUs K10 to Kn is reversed and the signal travel counterclockwise through the communication line 3.

As should be obvious from the foregoing description, when a fault occurs, a signal input from the clockwise communication line 4 to the photodiode PD2 is disabled in the communication device 12 of RTUs KI to K9, respectively. The RTUs send the optical signals counterclockwise through the communication line 3. At this time switching between the contacts permits the output signal to travel clockwise through the communication line 4. In the communication devices 12 of the RTUs K10 to Kn, as a signal input from the counterclockwise communication line 3 to the photodiode PD1 is inhibited, o u o 0 switching of the contacts is carried out so that the signal o 10 is sent clockwise over the communication line 4, and the output signal is carried counterclockwise over the communication line 3.

-ao Accordingly, the master station 1 temporarily stops communicating with those RTUs except for the adjacent RTUs K1 000 and Kn. The master station 1 can restore communication with all the RTUs by permitting the K1 and Kn, which are still 00 communication with the master station 1, to sequentially issue a control command to operate the input switch 14 or their Soutput switch 15 to enable all the contacts in the communication devices 12 of all the RTUs K1 to Kn.

In this case, a signal is input from the countercloc.wise communication line 3 in each of the RTUs K1 to K9, and is reversed in the RTU K9 so that the signal now travels through clockwise communication line 4.

11 In the RTUs K10 to Kn, a signal from the clockwise communication line 4 is reversed in the RTU K10 so as to travel through the counterclockwise communication line 3.

A description will now be given regarding the action in the case where only one of the communication lines 3 and 4 fails between the RTUs K9 and When only the communication line 3 fails, the detector 13 and the switching device 18 in the RTU K10 operate to switch the t connection of the input switch 14, and open the contact 17, thus disabling a signal supply to the communication line 4.

0 be In the RTU K9, the detector 16 and the switching device 19 operate to switch the connection of the output switch 15 and o open the contact 17. This disables a signal supply to the communication line 4.

"0 0 o 0 11'5 That is, this is the same as in the case of both communication lines 3 and 4 failing.

When only the communication line 4 fails, the detector 16 and the switching device 19 in the RTU K9 operate to switch the connection of the input switch 14, and open the contact 17, thus disabling a signal supply to the communication line 4.

In the RTU K10, the detector 13 and the switching device 18 operate to switch the connection of the input switch 145 and open the contact 17 to thereby disable a signal input to the 12 communication line 3. This is also the same as in the case of both communication lines 3 and 4 failing.

As explained above, the distribution line monitoring system of this invention employs a means which discriminates the levels of inputs from two optical communication lines that transmit signals in opposite directions. If the communication lines 3, 4 are cut or provide poor connections in the 0 0 transmission paths, the flow of signals on both sides of the failing section are reversed to continue the communication 'U1i between a master station an the operational remote terminal 0 o 0°n units.

0 0o 0a00 0 00

Claims

1. An electrical distribution line monitoring system comprising a master station and a plurality of remote terminal units for controlling discrete sections of the electrical distribution line, the master station and remote terminals being connected in series by each of a pair of looped optical communication lines that normally transmit optical signals in opposite directions, each remote terminal unit including: a photo-electric communication device coupled to both of the optical communications lines, such that each optical communication line is optically coupled to an associated light emitting diode for outputting an optical signal to the photo- electric communication device of an adjoining remote terminal unit based on a first electric signal, and, a photodiode for converting an optical signal from an adjoining remote terminal unit into a second electric signal and outputting said second electric signal to its associated light emitting diode; a pair of comparators for detecting an optical signal transmission failure, each comparator being associated with a particular photodiode to monitor the level of the optical signals converted by the associated photodiode and outputting a fault detection signal when the monitored signal falls below a predetermined threshold level; a pair of relay circuits for opening respective normally closed contacts on a side of each comparator opposite its corresponding photo diode to switch the communication path of the electric signal outputted by one of the photodiodes from the light emitting diode associated with one of the optical communication lines to the light emitting diode associated with the other of the optical communication lines to reverse a transmission path of the optical signals in accordance with the reception of the fault detection signal from the comparators; a line switch for segmenting the electrical distribution line into ones of said discrete sections; a switch actuator means connected to the line switch for selectively opening and closing the line switch; 14 I~ rrcl-drrur~s~iiu a detector associated with a line section for detecting a malfunction in that line section; and, a controller connected to said photo-electric communication device, for driving the switch actuator means, in accordance with a status signal outputted by the detector.

2. An electrical distribution line monitoring system according to claim 1, substantially as herein described with reference to and as illustrated in the accompanying drawings. Dated this 4th day of December, 1992. NGK INSULATORS, LTD By Its Patent Attorneys: GRIFFITH HACK CO. Fellows Institute of Patent Attorneys of Australia 0o f