GB2198001A

GB2198001A - Fault section locating apparatus

Info

Publication number: GB2198001A
Application number: GB08726268A
Authority: GB
Inventors: Minoru Nakahata; Nobuyuki Orito
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 1986-11-12
Filing date: 1987-11-10
Publication date: 1988-06-02
Anticipated expiration: 2007-11-10
Also published as: KR880006815A; DE3738493A1; DE3738493C2; GB8726268D0; GB2198001B

Description

4 1 FAULT SECTION FINDING APPARATUS 219.8001

Background of the Invention:

This invention relates to the finding of the fault section of a ring-like distribution network in which groups of loads are connected in the shape of a ring to supply electric power as in an urban distribution system or an interior distribution system.

Heretofore, an apparatus for the purpose specified above has combined ground directional relays endowed with a direction detecting function and a zero-phasesequence voltage detector, zero-phase-sequence current transformers, etc., in power protective relays and has discriminated whether a fault"section lies on the superior sid e or inferior side of the zero-phase-sequence current transformer.

More specifically, referring to Fig. 1, numeral 1 indicates a highvoltage transformer on an incoming side, numeral 2 a circuit breaker for protection on the incoming-side, numeral 3 a bus on a feeder side, symbols 4a - 4g circuit breakers for protection on the feeder side, symbols 5a 5g transformers on a load side, symbols 6a - 6g zero-phase- sequence current transformers for detecting a ground current, symbols 7a - 7g ground directional relays, and numeral 8 a zero-phase-sequence voltage detector. The zero-phase-sequence current transformers 2 6a - 6g and the ground directional relays 7a - 7g are respectively connected in one-to-one correspondence, and the zero-phase-sequence voltage detector 8 is connected in parallel with all the ground directional relays 7a - 7g. When a ground fault occurs in the system in which the various devices are connected in this manner, the ground current is detected by the zero-phase-sequence current transformers 6a - 6g, and the shift of the phase of a voltage attributed to the grounding is detected by the zero-phase-sequence voltage detector 8.

The ground current and the shift of the voltage phase are used for deciding whether the part of the occurrence of the grounding is on the power source side or the load side with respect to the corresponding one of the zero-phase-sequence current transformers 6a - 6g. In case of the load side, the corresponding one of the circuit breakers 4a - 4g is actuated to break a load side circuit. In case of the power source side, for example, the bus 3, the superior circuit breaker 2 is actuated by a ground directional relay 9 so as to break the whole circuitry.

Since the fault section finding apparatus in the prior art is constructed and operated as described above, the two factors of a zero-phase-sequence current and a zero-phase-sequence voltace must be handled. T11h,is

3 has led to the problem that the apparatus becomes expensive. Summary of the Invention:

This invention has been made in order to eliminate the problem mentioned above, and has for its object to inexpensively construct an apparatus which can find, not only a ground fault, but also a short-circuit fault.

A fault section finding apparatus according to this invention dispenses with a zero-phase-sequence voltage detector, and comprises indicators Cacb including a coil which.is -excted by the secondary current of a current transformer or a zero-phase-sequence current transformer, and a contact which is operated by the. excitation of the coili the indicator performing an indicating operation in accordance with the operation of the contact.

With the fault section finding apparatus of this invention, the indicator is actuated by the contact of quick operation on the basis of an abnormal current detected by the current transformer or the zero-phasesequence current transformer. Brief Description of the Drawings:

Fig. 1 is a circuit diagram of a fault section finding apparatus in a prior art;

Fig. 2 is a circuit diagram showing an embodiment of a fault section finding apparatus according to the 4 present invention; Fig. 3 is a circuit diagram showing an embodiment of a fault indicator in the embodiment shown in Fig. 2; and Fig. 4 is a circuit diagram showing another embodiment of the fault indicator.

Throughout the drawings, the same symbols indicate identical or equivalent portions. Description of the Preferred Embodiments:

Now, an embodiment of this invention will be described with reference to Figs. 2 and 3.

In Fig. 2, numerals 1 - 3, 5 and 6 designate the same portions as those of the prior-art apparatus illustrated in Fig. 1, and they shall be omitted from the description. Referring to Fig. 3, numeral 10 denotes a fault indicator which includes therein coils 12X and 12Y respectively connected to current transformers 11X and 11Y, and a coil 13 connected to the zero-phase-sequence current transformer 6. The fault indicator 10 also includes a contact 14, for example, a reed switch which is operated by the excitation of the coil 12X, 12Y or 13. This contact 14 is connected in series of the coil 15 of the indicator and is also connected in series with an external supply voltage across terminals P and N.

Connected in parallel with the contact 14 is a self holding contact 16 which is driven by the coil 15, so that when the coil 15 of the indicator is excited-, the contact 16 is closed to self-hold this circuit. In addition, another contact for indication 17 is operated by.the excitation of the coil 15 of the indicator, whereby a fault occurrence signal is sent out. The fault indicators 10 thus constructed are arranged in a ring-like distribution network as showff in Fig. 2.

More specifically, switch units 21a - 21g are disposed at the respective load points of the distribution network.

Each of these switch units has the corresponding two of ring switches 18a, 19 - 18g, 19g connected in series with the bus 3g and has the corresponding one of branch switches 20a - 20g connected in a manner to be T-branched from between the two of the ring switches 18a, 19a - 18g, 19g. The load side transformers Sa - 5g are respectively connected to the branch switches 20a - 20g. On the sides of the respective ring switches 19a 19g, there are provided the current transformers 11Xa, 11Xg and 11Ya llYg and the zero-phase-sequence current transformers 6a - 6g, the outputs of which are respectively connected to the fault indicators 10a - 10g. In the ring-like distribution network thus constructed, usually the load side transformers 5a - 5g are fed with electric power 6 under the state where any of the ring switches 18a, 19a - 18g, 19g is open, that is, the ring is separated. By way of example, as illustrated in Fig. 2, the ring switches 19d and 18e are open. When, in such an arrangement, the fault of short-circuiting, grounding or the like occurs on the ring network, namely, the bus 3 or on the sides of the load side transformers 5a - 5g, the fault indicators lying from the incoming side protecting breaker 2 to a fault point operate when overcurrents greater than a predetermined value flow therethrough, so that the occurrence of the fault and the position there of are determined accordance with the presence and number of the fault indicators having operated. On the basis of this result, the fault section is disconnected. Each fault indicator 10 is reset by the turn-off operation of the reset switch 22 based on, for example, a remote control as illustrated in Fig. 3. In this regard, when the reset switch 22 is operated by an automatic reset scheme based on a timer or the like, the fault indicator 10 can be automatically reset to make ready for the occurrence of the next fault, in a fixed time after the indication of the occurrence of the fault.

Although the embodiment has combined the current transformers for two phases and the zero-phase-sequence current transformer, current transformers for three 7 phases can be employed, and the current transformers may be installed on either side of the ring switches 18, 19.

Next, Fig. 4 is a circuit diagram which shows another embodiment of the fault indicator well suited for application to the present invention, and in which portions corresponding to those of the foregoing embodiment in Fig. 3 are assigned the same symbols.

Numeral 39 designates a limiting resistor which is connected in series with voltage dividing resistors 40 and 41, and these elements are connected across the terminals P and N of a control voltage source through first contact, namely, contact 37. Numeral 42 designates capacitor which constitutes a delay circuit, and which is connected in parallel with the voltage dividing resistors 40 and 41. A Zener diode 43 is connected at one end thereof to the node between the voltage dividing resistors 40 and 41, and is connected at the other end thereof to the base of a transistor 44. An auxiliary relay 45 is connected to the collector of the transistor 44, the emitter of which is connected to the side of the terminal N of the control voltage source.

The end of the auxiliary relay 45 remote from the transistor 44 is connected to the side of the terminal P of the control voltage source through a diode 68.

y 8 Numeral 69 designates a capacitor which is connected in parallel with the circuit of the auxiliary relay 45.

Elements 46 thru 52 form a circuit arrangement similar to the foregoing, which is connected with a second contact, namely, contact 38. That is, the element 46 is a limiting resistor, the elements 47 and 48 are voltage dividing resistors, the element 49 is a capacitor, the element 50 is a Zener diode, the element 51 is a transistor, and the element 52 is an auxiliary relay.

Numerals 28 and 29 denote electromagneticallyholding flag indicators, which are respectively provided with setting coils 28S, 2RS and resetting coils 28R, 29R.

The setting coil. 28S has a latch relay 53 connected in parallel therewith, and has one end thereof connected to the side of the terminal N of the control voltage source. Besides, this setting coil is connected at the other end thereof in series with a normally-open contact 54 and a normally-closed contact 55 operating upon the energization of the auxiliary relay 45 and a normallyclosed contact 56 operating upon the energization of the latch relay 53. The end of the normally-closed contact 56 remote from the setting coil 28S is connected to the terminal P of the control voltage source through a limiting resistor 57 and a diode 58.

One end off a capacitor 59 is connected between 9 7 the normally-open contact 54 and the normally-closed contact 55, while the other end thereof is connected to the side of the terminal N of the control voltage source.

The setting coil 29S has a latch relay 60 connected in parallel therewith. Likewise to the above, a normallyopen contact 61 and a normally-closed contact 62 adapted to be operated by the auxiliary relay 52 and a normallyclosed contact 63 adapted to be operated by the latch relay 60 are connected in series with the setting coil 29S and are connected to the limiting resistor 57.

One end of a capacitor 64 is connected between the normally-open contact 61 and the normally-closed contact 62, while the other end thereof is connected to the side of the terminal N of the control voltage source.

Diodes 65 and 66 are respectively connected to the resetting coils 28R and 29R, and the ends thereof remote from these coils are connected to the limiting resistor 57 through the normally-open contact 67 of a resetting relay 94.

The capacitor 69 is normally charged, and it supplies electrical energy to the fault indicator in a case where the control source voltage has been lost.

The resetting coils 70 and 71 of the respective latch relays 53 and 60 are connected in parallel with each other, together with a diode 72. The parallel circuit is connected to the normally-open contact 74 of the resetting relay 94 through a capacitor 73, and is then connected across the terminals P and N of the control voltage source. The resetting coil 70 is provided within the latch relay 53, and the resetting coil 71 within the latch relay 60.

Normally-open contacts 75 and 76 are contacts which are respectively operated by the latch relays 53 and 60, and are conne"cted in parallel with e.ach other. One end of the parallel circuit is connected to the limiting resistor 57, and this parallel circuit is connected at the other end in series with a diode 77, a Zener diode 78. a charging resistor 79 and a capacitor 80 and is then connected to the side of the terminal N of the control voltage source.

Numeral 81 designates a voltage dividing resistor, which is connected in parallel with the capacitor 80.

A discharging resistor 82 is connected in parallel with the capacitor 73 and the latch relays 70, 71. Shown at numeral 83 is a capacitor, one end of which is connected between the limiting resistor 57 and the contacts 56, 63, 67, 75, 76 and the other end of which is connected to the terminal N of the control voltage source.

1 1 11 9 Numeral 84 indicates a Zener diode, one end of which is connected between the charging resistor 79 and the capacitor 80 and the other end of which has transistors 85 and 86 connected thereto in Darlington connection, the emitter of the transistor 86 being connected to the terminal N of the control voltage source. The collector of the transistor 85 is connected to the terminal P of the control voltage source. The collector of the transistor 86 has the resetting relay 94 connected thereto and is then connected to the terminal P of the control voltage source thrQugh a series circuit consisting of normally-closed contacts 88 and 89 which are respectively operated by the auxiliary relays 45 and 52.

Numerals 90 and 91 represent contacts for signals, which are operated by the latch relay 53 and of which the contact 90 is normally open and the contact 91 is normally closed. Numerals 92 and 93 represent contacts for signals, which are operated by the latch relay 60 and of which the contact 92 is normally open and the contact 93 is normally closed.

When, in the fault indicator thus constructed, the short-circuiting detection coil 12X or 12Y or the grounding detection coil 13, namely, means for detecting the abnormality of a circuit current is excited by the current transformer 11X or 11Y or the zero-phase-sequence current transformer 12 6, the rormally-open contact 37 or the normally-open contact 38 is operated in accordance with a detection current greater than a predetermined value, and the capacitor 42 or 49 is charged.

When the division voltage of the voltage dividing resistors 40, 41 or 47, 48 exceeds the breakdown voltage of the Zener diode 43 or 50 owing to the charging of the capacitor 42 or 49, the transistor 44 or 51 is turned 11 on" to energize the auxiliary relay 45 or 52. Owing to the energization of the auxiliary relay 45 or 52, the normally-open contact 54 or 61 and normally-closed contact 55 or 62 corresponding thereto are operated, and energy stored in the capacitor 59 or 64 is discharged to the setting coil 28S or 29S of the flag indicator 28 or 29 and the latch relay 53 or 60 so as to excite the coil and energize the relay. When the latch relay 53 or 60 is energized, the normally-closed contact 56 or 63 corresponding thereto is operated so as to discharge all the charges of the capacitor 59 or 64 to the flag indicator 28 or 29 and the latch relay 53 or 60. In addition, owing to the operation of the normally-open contact 75 or 76 of the latch relay 53 or 60, charges stored in the capacitor 83 are charged into the capacitor 80 through the diode 77, Zener diode 78 and charging resistor 79.

13 7 -7 On this occasion, when the control source voltage is not lost, a charging current to the capacitor 80 flows also from the terminal P of the voltage source. However, even when the source voltage is lost, the charging is performed according to a predetermined charging characteristic by the capacitor 83. When the charges of the capacitor 80 exceed the breakdown voltage of the Zener diode 84, the transistors 85 and 86 are turned "on" through this Zener diode 84, and the resetting relay 94 is energized in the state in which the control power source is not lost.

When the fault is continuing at this time, the normallyclosed contact 88 or'89 of the auxiliary relay 45 or 52 is operating, and hence, the resetting relay 94 stands by without being energized.

When the resetting relay 94 is energized, the normallyopen contacts 67 and 74 thereof are operated to excite the resetting coils 28R and 29R of the respective flag indicators 28 and 29 and the resetting coils 70 and 71 of the latch relays 53 and 60, whereby the corresponding indications and contacts are restored into the original states so as to make ready for the detection of the next fault.

The operation signals are externally sent by the contacts 90, 91 or 92, 93 of the corresponding latch 14 relay 53 or 60. In a monitoring center, the signals of the contacts 90 - 93 are gathered and are used together with other signals so as to monitor the statuses of a large number of devices and control switches in an electric system.

In the embodiment, the Zener diodes 43, 50, the transistors 44, 51, the auxiliary relays 45, 52, the latch relays 53, 60, and the contacts operated in cooperation with these relays 45, 52, 53, 60 have been explained as the individual members, but they can be considered as drive means for driving the flag indicators 28 and 29.

In addition, the current transformers 11X, 11Y, the zero-phase-sequence current transformer 6, and the short-circuiting detection coils 12X, 12Y and grounding detection coil 13 respectively connected with these current transformers can be collectively considered as the means for detecting the abnormality of the circuit current.

Although the embodiment has mentioned the example utilizing the resistors and the capacitors, effects similar to those of the above embodiment are achieved even when output signals from a microcomputer or the like are utilized.

As described above, according to the embodiment 1 of Fig. 4, an input portion is equipped with a delay circuit, so that the erroneous operations of the input portion attributed to surge and noise are prevented, and a fault indicator of high precision is provided. Another effect is that, since an automatically-resetting timer circuit is built in, the fault indicator is automatically reset in a predetermined time internal which was previously set, so that.the automatic monitoring of a system is facilitated.

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Claims

1. A fault section finding apparatus having an A.C. power feeding bus which is laid in the shape of a ring, and unit switches which are disposed at respective load points of the bus; said each unit switch comprising:

(a) a pair of switch means inserted in series with said bus, and branch switch means branched in the shape of the letter T from a node of the pair of switches for supplying power to a load; (b) means for detecting any abnormality of a circuit current, said means including current transformers which are inserted in said bus so as to detect shortcircuit currents, and a zero-phase-sequence current transformer which is inserted in said bus so as to detect a ground current; (c) a fault indicator which indicates a fault by drive means operating in response to a detecting operation of the detection means; and (d) means for sending out a signal expressive of the occurrence of a fault in response to an indicating operation of said fault indicator; whereby a fault section of said power feeding bus is found on the basis of the presence of the operations of the fault indicators of said unit switches at said 17 respective load points.

2. A fault section finding apparatus as defined in Claim 1, wherein said drive means is provided with means for self-holding the operation.

3. A fault section finding apparatus as defined in Claim 1, wherein an input portion of said drive means includes a delay circuit which starts the operation of said drive means after a predetermined time internal in response to the detecting operation of said detection means.

4. A fault section finding apparatus as defined in Claim 3, wherein said delay circuit includes a contact which is closed in response to the detecting operation of said detection means, a capacitor which is connected to a control voltage source through said contact, voltage dividing resistors which are connected in parallel with said capacitor. a transistor whose base circuit is connected to said voltage dividing resistors, and relay means connected to said control voltage source through said transistor, said fault indicator being operated by energization of said relay means.

5. A fault section finding apparatus as defined in Claim 1, wherein said drive means is provided with means for resetting the operation of said fault indicator after a predetermined time interval from the operation thereof.

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6. A fault section finding apparatus, substantially as herein described with reference to figures 2 and 3, or figure 4, of the accompanying drawings.