AU604412B2 - Supervising system for distribution lines - Google Patents

Description

It COMMONWEALTH OF AUSTRAIA PATENTS ACT 1952 COMPLE SPECIPICATION 0 441 i

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1 NAME ADDRESS OF APPLICANT: NGK Insulators, Ltd.

2-56, Suda-Cho, Mizuho-Ku, Nagoya City Aichi Prefecture Japan NAME(S) OF INVENTOR(S): Hiromi NAGASAKA Akimichi OKIMOTO Yoshitaka ITO ADDRESS FOR SERVICE: DAVIES COLLISON Patent Attorneys 1 Little Collins Street, Melbourne, 3000.

This document contains the amendments made under Section 49 and is correct foi [priniing.

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COMPLETE SPECIFICATION FOR THE INVENTION ENTITLED: Supervising system for distribution lines The following statement is a full description of this invention, including the best method of performing it known to me/us:- The present invention relates to a supervising system for electric power distribution lines.

In the conventional manner of supervision and control for a network of such power distribution lines belonging to one service office, it has been customary handled in general directly by the service office as a sole unit.

Namely, as can be seen from Fig. 5 showing S briefly a conventional system, a signal or communication network 4 is provided in parallel to a distribution line Snetwork 1, and by using this communication network 4 I a service station 5 is connected to a plurality of /veans sub-stations or slave stations 3 having functions to ji detectAearth condition of the distribution lines or tc I 15 energize to open or close the respective switches 2 provided along with the distribution lines. A hostcomputer 6 provided in the service station 5 receives data from each of the slave stations 3 through a communication equipment 7, and based on the received data the host-computer 6 controls the opening or closing I" of the switches 2 through the respective slave stations 3. This is so called a single processor -2- A 3

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i:: i 1 jt b i dt~r:, ii i 1 2 3 4 6 7 8 9 11 12 13 14 15 16 17 18 S 19 20 21 22 23 24 't 25 26 27 28 29 t il 30 31 32 33 34 36 38 ^-LV 38 In the duplex system, the ability to control distribution line network 1 is doubled compared with single processor system. If we assume the fault rate Y computer is the fault rate Y of each computer in single processor system and in the duplex system is same, being However, the overall fault rate Z for distribution line network is; Zs a for the single processor system and Zd a for the duplex system.

For instance, if we assume; a 0.05 system. In this system, since the operation of each of the switches 2 in the whole distribution line network 1 is controlled by a single host computer 6, the host computer 6 requires very large capacity.

When the supervision of a distribution line network 1 extending over a very wide area is effected by a single host computer 6, it may be necessary to arrange a duplex system further including a large size back-up computer having the same processing capacity as the host computer 6 to back-up the host computer 6 ir the event of its failure for any reason.

the the per the the each 44 5-4

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the following result may be expected.

Zs a 0.05 5.0 x 10-2 Zd a 2 0.052 2.5 x 10 3 Namely, in the duplex system the fault rate is much smaller than in the single processor system.

In the duplex system, 2 sets of very expensive computers are used and moreover since'the construction of the connection networks between the two large capacity computers is very costly, the construction cost may exceed more than double that of the single processor system and it has a disadvantage therefore in the extraordinarily large initial cost.

The object of the present invention is to solve aforementioned problems or mitigate at least part of them and to obtain a stable supervising system for a distribution 900724.eldspe.006.31462.SPE,3 4 1 line network at a relatively low cost in which the overall 2 fault rate can be decreased.

3 According to the present invention there is provided a 4 supervising system for a distribution line network comprising distribution lines, there being slave stations 6 having actuator means for actuating distribution equipment 7 provided in each of the distribution lines, said slave 8 stations having detecting means for detecting trouble in 9 respective distribution lines of the network, and there being provided a communication network for providing 11 connection between supervising computing means, and the 12 slave stations, wherein detected data detected by the 13 detecting means of each slave station is input to the 14 computing means and the computing means identifies the distribution equipment to be controlled for actuation based o 16 on the detected data and the relevant distribution equipment 17 is actuated under its control through the actuator means of 9 18 the respective slave station; said supervising system being 19 characterized in that the distribution line network is sub- @9 4t divided into a plural number of small distribution line 21 networks, said communication network being sub-divided into 22 a plurality of small communication networks and a computer 23 being provided for each one of said small communication 24 networks to supervise a respective one of the small 4, 25 distribution line networks, each of said computers being 26 given a processing facility for at least two small rrii 27 distribution line networks, and for backing up at least one 28 of the other of said computers, the computers being arranged 29 to supervise each other through a communication network connecting the computers.

31 Each computer normally supervises the small 32 distribution line network allotted thereto through a 33 communication network connecting the computer and the slave 34 stations and actuates distribution line equipment provided in the distribution line, when a faulty condition is 36 detected, so that an optimum power supply is continuously R I 37 kept in the small distribution line network supervised by ,z 38 900724. eldspe.006 31462. SPE. 4 5I 1 that computer.

2 Each computer has the processing capacity for the 3 supervision of at least two small distribution line networks 4 and a group of computers are so arranged that they can always supervise each other through a communication network 6 between the computers. Accordingly, if any one of a group 7 of computers becomes unable to supervise the small 8 distribution line network allotted thereto for some reason, 9 another computer or other computers having the capacity for that processing facility will take charge for the small 11 distribution line network concerned. Accordingly, the 12 computers of a group act to mutually back up any other 13 computer oE the group in order that the supervision system 14 for a distribution line network belonging to a particular o o 15 supervision station will not cause trouble or interruption.

o 16 Figs. 1 to 3 show one practical embodiment of the 17 present invention, in which; rrom 18 Fig. 1 is a simplified diagram for showing a ro~ofo S° 19 supervising station and a distribution line network under.

o 20 its supervision, 21 Fig. 2 is a block diagram for showing schematically the 22 construccion of a master station, and 23 Fig. 3 is a block diagram for showing the construction ItW 24 of a slave station, Fig. 4 is an explanatory diagram for explaining a data S26 communication system between a master station and slave I 27 stations, and 28 Fig 5 is a schematic- diagram for showing a 29 distribution line supervising equipment and a distribution 30 line network under its supervision, which had been explained 31 in the above.

32 Embodiments of the invention will now be explained in 33 more detail, by way of example only, with reference to the 34 accompanying drawings.

Fig. 1 shows a simplified diagram of a supervising 36 station W and a distribution line network N under its 37 supervision. The distribution line network N is fed the vN 38 900724,eldspe.006,31462.SPE,5 6 1 power from a substation S and comprises a plurality of 2 switches 11 as the distribution equipment for electricity.

3 This distribution line network N is subdivided into 4 small 4 distribution networks nl to n4.

There are 4 small communication networks or master to 6 slave transmission paths ml to m4 provided in parallel to 7 the respective small distribution networks nl to n4.

8 Furthermore, each of the master to slave transmission paths 9 ml to m4 comprises a plurality of slave stations 12 of a remote supervision and control system. Thus a slave station 11 12 is provided for each of the switches 11.

12 Master to slave transmission path ml is connected to a 13 master station P1 of the remote supervision and control 14 system. The master station P1 can effect mutual or both way data communication between the slave stations 12 connected 16 to the same transmission path ml. Likewise, for each other 17 master to slave transmission path m2 to m4, respective 18 master stations P2 to P4 are provided and these master 19 stations P2 to P4 can effect mutual data communication between the slave stations 12 connected to the respective 21 transmission paths m2 to m4.

22 The master stations P1 to P4 are mutually connected by 23 an inter-master transmission path k and also connected to 24 respective micro-computers Cl to C4, which will be explained 25 hereinafter. Thus the master stations P1 to P4 can 26 communicate with each other through the inter-master r 27 transmission path k.

28 Each master station P1 to P4 is connected to a 29 'respective distribution line controlling processor or microcomputer C1 to C4. Each micro-computer C1 to C4 has a 31 processing facility for supervision and control of two small 32 distribution line networks.

33 Accordingly, if the distribution line network N is 34 subdivided into 4 sections as shown in Fig. 1, the supervising station W is formed of 4 master stations P1 to 36 P4, 4 micro-computers Cl to C4 and an inter-master i 37 transmission path k.

38 900724.eldspe.006.31462.SPE.6 '1 7 1 2 3 4 6 7 8 9 11 12 13 14 S 15 S: o16 17 18 19 S o 20 21 22 23 24 26 27 S28 29 .o 30 31 32 33 34 36 37 38 0U ot'r o In the above embodiment, an optical communication system can be employed for the master to slave transmission path ml to m4 and for the inter-master station transmission path k.

A construction of each of said slave stations 12 will be explained by referring to Fig. 3.

Fig. 3 shows a block diagram of one slave station 12 as provided in the small distribution line network nl. This station 12 comprises a signal or communication device 31, controller 32, a sensor group 33 for detecting current and voltage in the distribution line and an actuator 34 providing the actuator means.

The communication device 31 has a bi-directional conversion function between optical communication signals and electrical signals and is connected to the master to slave transmission path ml.

The controller 32 includes a central processor unit CPU, a read only memory ROM, and a random access memory RAM and receives a detecting signal fed from.the. sensor group 33. The current, the voltage and the phase of the distribution line are calculated by the controller 32 which communicates the condition of the distribution line, at respective locations of the distribution line, to the master station P1 to which the slave station belongs through the communication device 31. The controller 32 receives the controlling data sent from the master station P1 through the communication device 31 and, based on said controlling data, acts to control the switch 11 to open or close by means of said actuator 34.

Detailed construction of each of the master stations P1 to P4 will be explained hereinafter by referring to Fig. 2.

Since all the master stations P1 to P4 have almost the same construction, only the master station P1 will be explained for the sake of simplicity.

As can be seen from Fig. 2, the master station P1 is formed of 5 units, of which each unit comprises a communication device 21, a communication controlling portion 900724.eldspe.006.31462.SPE.7 8

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1 r; tra: r,: 1 2 3 4 6 7 8 9 i0 11 12 13 14 ,E 15 t 1 16 17 18 19 21 22 23 24 26 27 28 29 30 31 32 33 34 36 37 22, and a dual-port RAM 23 (hereinafter referred to as a

"DPR").

One out of the 5 units will communicate between a micro-computer Cl belouiging to the master station P1 with other master stations P2 to P4 through their respective micro-computers C2 to C4, by means of inter-master transmission path k, to transfer or to receive data and the data is temporarily stored in the DPR 23. Another one of the 5 units will exchange data between each slave station 12 on the master to slave transmission path ml corresponding to the respective micro-computer Cl. The further 3 units are provided for the exchange of data between each slave station 12 on the master to slave transmission lines m2 to m4 for back-up purposes.

The communication devices 21 have a mutual conversion function between optical communication signals and electrical signals and are connected to the respective transmission paths ml to m4.

Each dual-port RAM, i.e..DPR.23, is a random', acbess memory RAM, being able to respond both to the micro-computer Cl and to the respective communication controlling portions 22 simultaneously for their access.

Each communication controlling portion 22 comprises a CPU, a ROM and a RAM, and receives communication information mainly from the slave stations sent via the transmission paths ml to m4 allotted thereto and from the inter-master path k. The received information is written into the DPR 23 and. sent to micro-computer Cl, being reconstructed therein as controlling information for the respective slave stations. Thus the communication controlling portion 22 acts as a repeater controlling station between the microcomputer Cl and respective one of the transmission paths ml to m4 or k allotted thereto.

The function of the supervising system having the aforementioned construction will be explained hereinafter.

For simplifying the explanation only the functions of the master station P1 shown in Fig. 2 and the micro-computer Cl f.

900724.eldspe.006,31462.SPE.8 9 1 will be explained.

2 In the supervising system for distribution lines shown 3 in Fig. 1, normally the micro-computer Cl supervises only 4 the small distribution line network nl. In this case, a unit originating a controlling instruction is only one unit 6 among the 4 units of the master station P1 connected to the 7 master to the slave transmission paths ml to m4. This unit 8 receives an instruction from the micro-computer Cl which is 9 in charge of communication to the master to slave transmission path ml. The other 3 units are in a stand-by 11 condition, awaiting instruction from the micro-computer Cl.

12 The unit which is in charge of communication by way of 13 inter-master communication path k is always functioning to 14 interchange information with other micro-computers C2 to C4.

15 The unit of the master station P1 which is connected to 16 the master to slave transmission line ml receives respective 17 slave station data transmitted from the various slave o 18 stations 12 through the communication device 21 as 19 communication information in the form of a-series of data p4 9.

a4 20 groups or data frames FD as shown in Fig. 4. The 21 communication controlling portion 22 writes-in these data 22 frames FD into the DPR 23.

23 As shown in Fig. 4, the slave station data forming each *24 data frame FD consists of slave station identification data 25 FD1, controlling data FD2 for controlling a switch 11, and 26 detected data FD3 for detecting the condition of the switch 27 11 and of the sensor group 33.

28 When the micro-computer Cl identifies writing-in or 29 input of data to DPR 23 connected to the master to slave j 2 30 transmission path ml from the communication controlling 31 portion 22, an access to this DPR 23 is established 32 immediately and the detected data related to the various 33 slave stations 12 are read out therefrom and an operation 34 for finding an optimum condition of opening and closing of the various switches 12 in the relevant small distribution 36 line network nl is carried out. The micro-computer Cl uses 37 the result of this operation as a control instruction and 4 38 900724.eldspe.00631462.SPE.9

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1- 10 1 re-writes a relevant data frame written in the DPR 23 2 connected to the relevant master to slave transmission path.

3 This means that among the data for slave stations 12 under 4 control, the controlling data FD2 of a data frame FD is rewritten.

6 The data frame of which the controlling data FD2 has 7 been re-written is sent to the master to slave transmission 8 path ml by the communication controlling portion 22 through 9 the communication device 21 and then transferred to each of the slave stations. Each slave station reads-out its own 11 slave station data from the transferred data frame, and 12 controls the opening or closing of switches 11 according to 13 the content of the controlling data FD2. The condition of 14 the distribution line is then re-written-in as new detected a° 15 data FD3 by transmitting it into the data frame FD.

16 On the other hand, in the inter-master transmission 17 path k, information related to the various master stations 18 P1 to P4, that is the load allocation of the small 19 distribution line networks nl to z14 by the respective one of 20 the master stations P1 to P4, and the condition of load of 21 each of the micro-computers, etc., is transmitted as a 22 series data group or data frame.

23 The unit of the master station P1 which is connected to 7 24 the inter-master transmission path k memorizes the information relating to the master stations P1 to P4 when it 26 is received as a data frame into the RAM of the 27 communication controlling portion 22, and writes into the 28 DPR 23 information concerning the micro-computers where it 29 is not directly connected into the DPR 23. Then this information in the DPR 23 is transmitted on the inter-master 31 transmission path k together with the information written 32 into DPR 23 by the associated micro-computer Cl. In this 33 way, a data frame flowing through the inter-master 34 transmission path k is refreshed at each time of its passing through each one of the master stations P1 to P4.

36 The micro-computer Cl reads-out the DPR 23 of the unit 37 of the master station P1 which is connected to the inter- TZ 38 900724,eldpe.00631462.SPE.10 11 1 master transmission path k and identifies the condition of 2 the other micro-computers C2 to C4. It also notifies its 3 own condition to the other micro-computers C2 to C4 by 4 writing-in to this DPR 23.

The micro-computer Cl always supervises the load 6 condition, occurrence of troubles and etc. of the other 7 micro-computers C2 to C4 based on the dai-, lowing through 8 the inter master transmission path k. When a problem or the 9 like in one of the other micro-computers C2 to C4 is found, and when the micro-computer Cl is supervising only one small 11 distribution line network allotted thereto so that it is 12 lightly loaded, this micro-computer Cl takes over the 13 supervision of a small distribution line network n2 (for 14 instance) which had been under supervision by the microcomputer, for instance micro-computer C2, which is now in 16 trouble condition or had been in a heavy load condition, and t 17 also notifies the increase of its own load to the other 18 micro-computers C2 to C4 due to taking charge of this 19 supervision.

Furthermore, this micro-computer Cl acts to write-in 21 into the DPR 23 of a unit, which unit had been in stand-by 22 condition in the master station P1 and will now take charge 23 of the small distribution line network n2, to notify this 24 unit of the fact of becoming a source of transmission of t" 25 instruction to said master to slave transmission path m2.

26 This unit then receives the relevant controlling data 27 FD2 for writing-in to its DPR 23, together with all the 28 individual data transferred from all of the slave stations 29 belonging to the master to slave transmission path m2 t A* 30 including or comprising the detected data FD3. By this 31 manner, the supervision of the small distribution line 32 network n2 is commenced.

33 The units in stand-by condition, being not the 34 transmitting source of instruction, write-in the detected date FD3 of each received data frame FD to their respective 36 DPR 23 so that each unit always refreshes the data relating 7 37 to the condition of the slave stations of the small _7 38 900724.eldspe.006.31462.SPE.11 r.I 2

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12 1 2 3 4 6 7 8 9 11 12 13 14 0 15 16 0oo 17 18 0 OB 19 BO 0' D 20 21 22 23 0 24 25 26 27 28 29 31 32 33 34 36 37 I t 38 I 1 H 1 distribution line networks (in this case n3 and n4) and transmits received data frames FD to the master to slave transmission path m3, or m4.

Further, the micro-computer Cl modifies the information stored in the DPR 23 of the unit connected to each of the transmission paths ml to m4 to effect CRT display or the like and by this it supplies information concerning the power supply controlling condition of the distribution line network N to the supervisor of a supervising station under his supervision and also automatically effects trouble recovering of the small distribution line network or service interruption for repair work, etc.

In a supervising system according to an embodiment of the present invention having the abovementioned construction, modification of the system such as capacity increase and the like can be obtained by only altering the repeating location so that the system has great capacity for expansion and flexibility.

Each micro-computer is just responsible for of the distribution line network being supervised so that the software can be made of relatively small capacity and thus the productivity of the software becomes high and the maintenance thereof is also easier.

The micro-computers Cl to C4 supervise each other so that not only the reliability of the overall system can be increased but the system can be constructed at lower cost than the aforementioned single processor system or the duplex system due to the fact of dividing the distribution line network into an optimum number. This'point will be explained hereinafter by referring to some practical embodiments.

First of all the increase of overall system reliability will be explained in a comparison with the conventional systems.

If we assume the capacity of a computer which is required to supervise a whole distribution line network system as P and the number of small distribution line 900724.eldspe.006,31462.SPE,12 It -13 1 networks into which a system is divided as M, since each 2 micro-computer has to supervise two small distribution line 3 networks, the capacity of each micro-computer can be 4 expressed as: 2P/M 6 Further, if we assume the failure rate Y for the system 7 with respect to each small distribution line network is a; 8 the failure rate Yc of one micro-computer C is expressed as: 9 2a/M When number i of micro-computer(s) are failed out of M 11 micro-computers, the probability pl of failure for i micro- 12 computers and the probability p2 for the other micro- 13 computers functioning normally can be expressed as: 14 p1 (2a/M) 1 S' 15 p 2 (l-2a/M M i 16 Since each micro-computer has function to supervise two TI t 17 small distribution line networks, even when up to half the 18 number of micro-computers are in trouble, the system S19 operatibn can be maintained perfectly. Therefore, the failure rate of the overall system of this embodiment Zm can 21 be evaluated as follows.

22 M i M-l S23 Zm MCi (2a/M) (l-2a/M) (2i M)/M 24 i =M 12 26 The following table 1 shows a result of calculation for 27 the failure rate of the system of the present invention and 28 that of conventional systems, when we assume (a=0.05).

29 A 31 32 33 34 36

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4 37 A %r7 38 900725.eldspe.00631462.SPE. 13 14 il 1 2 3 4 6 7 8 9 11 12 13 14 15 16 17 •4I "18 19 21 22 23 4 K 24 St L *1s 25 26 4a t 27 28 29 S 30 31 32 33 34 36 3 7"37 38 eA',I Table Comparison for failure Division Systems number M Failure rate Single processor system 1 Zs=5.0x10-2 Duplex system 1 Zd=2.5x10-3 2 Zm=2.5x10- 3 4 Zm=3.1x10-5 System according to the 8 Zm=4.2x10- 9 present invention 10 Zm=4.1xlO-U 16 Zm=2.0x10-17 20 Zm=7.9x10- 2 2 It can be noted from the above table-i that the failure rate Zm will show a remarkable decrease according to the increase of the division number M in the system of the invention.

Secondly, the economy of the system construction cost will be explained by referring to conventional systems.

When we consider the capacity of a computer p (the unit is MIPS), it has been proposed that the cost f(p) per one computer is given as follows: f(p) 50.37 x p 2 .03 (The unit is expressed in one million Japanese Yen) Using this proposal and assuming the computer capacity as p for supervising and controlling the overall distribution line network N, and furthermore assuming as mentioned before, that the division number of the distribution line network is M and that the construction cost of an inter-master communication device per computer is g, the overall construction cost Q of the supervising station will be given in the following manner.

Namely, the constril tion cost Qs for a single processor system is: Qs f(p) The construction cost Qd for a duplex system is: Qd 2'f(p) 2'g 900724,eldspe.006.31462.SPE.14 rate of each system 15 1 The construction cost Qm of the abovementioned system 2 of the embodiment of the present invention is: 3 Qm M'f(2p/M) M-g 4 If we assume 1,000 slave stations are provided in the distribution line network n and the computer capacity for 6 supervising and controlling the network as: 7 p S (MIPS) 8 and also, 9 g 100 (unit 10 thousand Japanese yen), the result of calculation for each system will be given by table-2.

11 As can be seen from the table-2, if the division number 12 M is selected to be a value 8 to 20 in the system of the 13 present embodiment, the system of the invention can be 14 constructed much cheaper than both the single processor system and the duplex system. Therefore, it can be said 16 that the system of the present invention has an excellent 17 advantage in view of economy as well.

18 19 Table-2 Comparison for the construction cost 21 of overall supervising system 22 23 24 26 27 28 29 31 32 33 34 36 37 A A ,7 38 Construction Systems Division cost of the number M system Q (million yen) Single processor system 1 Qs 41 Duplex system 1 Qd 84 2 Qm 84 4 Qm 44 System of the present 8 Qm 28 invention 10 Qm 26 16 Qm 26 20 Qm 28 The present invention is not to be limited to the abovementioned embodiment only and the following 9 00 724.eldspe.006.31462.SPE.15

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r 16 09 .P 4 O 49 go 64 0 §Os 0rl 0@ $4 04 4. 4.

1 2 3 4 6 7 8 9 11 12 13 14 15 16 17 18 19 20 o 20 21 22 23 24 26 27 28 29 31 32 33 34 36 -8 modifications for instance may be considered.

In the above embodiments, 3 units were added for backing up 3 small distribution line networks m2 to m4. But only 1 unit may be added for this purpose. The data communication system can be modified for each case to a different extent without departing from the scope of the present invention.

According to the distribution line supervising system of embodiments of the present invention, a distribution line network supervised by one supervising station is subdivided into a plurality of small distribution line networks and these networks are supervised by a number of computers each having the processing facility of supervising at least two small distribution line networks, and moreover these computers are supervised mutually so that a partial system failure will not cause service trouble for the supervising system of the whole distribution line network. Accordingly, the probability of occurrence of failure leading to trouble in the supervision system of the distribution line network can be remarkably decreased compared with the conventional distribution line supervising systems. Thus the system can afford a great advantage for the stable operation.

Also due to the fact that a number of computers are supervising the distribution line network by dividing it, system enlargement in terms of the computers or the small distribution line networks can be done easily so that the capacity for expansion is large and thus the flexibility for system modification can be excellent. Since the process facility of one computer need not be very large, as it is in the conventional systems, the overall system can be constructed at lower initial cost than the conventional systems by suitably selecting the division number M of the network. Thus the system can have economic merit in low construction cost.

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Claims (2)

11. 12 13 14 15 16 17 18 19 21 22 23 24 V 26 27 28 29 (130 31 32 33 34 36 37 '38 1. A supervising system for a distribution line network comprising distribution lines, there being slave sta--.ions having actuator means for actuating distribution equipment provided in each of the distribution lines, said slave -L±ons having detecting means for detecting trouble in respective distribution lines of the network and there being provided a communication network for providing connection between supervising computing means, and the slave stations, wherein detected data detected by the detecting means of each slave station is input to the computing means and the computing means identifies the distribution equipment to be controlled for actuation based on the detected data and the relevant distribution equipment is actuated under its control through the actuator means of the respective slave station; said supervising system being characterised in that the distribution line network is sub-divided into a plural number of small distribution line networks, said communication network being sub-diided into a plurality of small communication networks and a computer being provided for each one of said small communication networks to supervise a respective one of the small distribution line networks, each of said computers being given a processing facility for at least two small distribution line networks, and for backing up at least one of the other of said computers, the computers being arranged to supervise each other through a communication network connecting the computers. 2. A supervising system for distribution lines as claimed in claim 1, wherein the distribution line network is sub- divided into 4 small communication networks. 3. A supervising system for distribution lines as claimed in either one of the preceding claims, wherein the communication paths comprise optical communication lines. 9007 24,eldspe. 006. 314 62. SFE.17 7 i j LI I 18 4. A supervision system for distribution lines substantially as hereinbefore described with reference to the accompanying drawings. 7 8 9 11 12 13 14 16 17 18 19 21 22 23 24 26 27 28 29 31 32 33 34 36 37 38 f:M DATED this 14th day of July, 1990. NGK Insulators, LTD. By its Patent Attorneys DAVIES COLLISON

900724.eldspe.006.31462.SPE.18