US 3895369 A
In a supervisory system for detecting abnormal conditions, existing AC electric power supply lines are utilized and a plurality of resonance elements controlled by abnormal condition detectors are connected across the supply lines. High frequency currents of variable frequency are transmitted to the resonance elements over the supply lines and the high frequency current passed through the resonance elements are received by a receiver which is controlled such that it operates only in the regions about the zero points of the AC voltage wave so as to improve the S/N ratio.
Claims available in
Description (OCR text may contain errors)
United States Patent [191 Ono et a1.
[ SUPERVISORY SYSTEM FOR ABNORMAL CONDITIONS  Inventors: Toshiharu Ono, 211,Takara-Cho,
Chuo-ku; Akira Tazaki, 2-38-8, Hanegi, Setagaya-ku, both of, Tokyo, Japan  Filed: Dec. 26, 1973 21 Appl. No.: 427,712
 Foreign Application Priority Data Dec. 27, 1972 Japan 47-2844  US. Cl. 340/310 R; 340/171  Int. Cl. G08b 21/00  Field of Search 340/213 R, 310 R, 310 P,
340/170, 73, 216, 416,163, 207,151,171, 177 VA, 147 SY; 324/73  References Cited UNITED STATES PATENTS 3,550,090 12/1970 Baker et al. 340/408 3,559,176 1/1971 Baker et a1. 340/163 July 15, 1975 3,689,886 9/1972 Durkee 340/163 3,806,876 4/1974 Kniel et a1 340/310 R 3,818,466 6/1974 Honda 340/216 OTHER PUBLICATIONS IBM Technical Disclosure, Receiver Synchronizing Circuit, Vol. 7, No. 12, May 1965.
Primary Examiner-Thomas B. Habecker Attorney, Agent, or FirmCharles W. I-Ielzer  ABSTRACT In a supervisory system for detecting abnormal conditions, existing AC electric power supply lines are utilized and a plurality of resonance elements controlled by abnormal condition detectors are connected across the supply lines. High frequency currents of variable frequency are transmitted to the resonance elements over the supply lines and the high frequency current passed through the resonance elements are received by a receiver which is controlled such that it operates only in the regions about the zero points of the AC voltage wave so as to improve the S/N ratio.
12 Claims, 13 Drawing Figures SHEET PATEHTEDJUL 15 m PATENTEDJUL 15 ms SHEET PATENTEDJUL 15 ms SHEET if mwcv mmtim 1 5 SHEET SUPERVISORY SYSTEM FOR ABNORMAL CONDITIONS BACKGROUND OF THE INVENTION This invention relates to an environmental security supervising system capable of supervising at high reliabilities from a control center, threats to environmental security such as firehazards, robberies, public hazards, leakage of electricity and interruptions of electric supply, etc., as well as abnormal conditions of remotely located machines and apparatus by utilizing existing electric distribution lines or indoor distribution lines of commercial frequency.
In a prior art system of supervising such threats environmental security as firehazard or the like, upon ocurrence of an abnormal condition a detector responsive thereto operates to short circuit signal lines, thereby transmitting an alarm signal to the receiver at the control center. Accordingly, where a number of detectors are connected to the signal lines and when one of the detectors operates, it is difficult to correctly locate the position where such abnormal condition occurs. Installation of such signal lines requires large expense and in an existing building, it is difficult to install such signal lines. For the purpose of discriminating a number of detectors, active elements such as transistors have been installed on the transmitter side but such active elements require sources of operating powers.
Where the signal lines utilize existing electric power lines or distribution lines, the noise current and surge waves travelling on the power lines not only damage transistors but also cause erroneous informations. Such system requires expensive maintenance of the terminal transmitters and, moreover, is required to operate satisfactorily even when the supply of the power is interrupted. Accordingly, such system is not reliable and uneconomical.
SUMMARY OF THE INVENTION It is an object of this invention to provide an improved inexpensive supervisory system capable of correctly detecting the location where an abnormal condition occurs.
Another object of this invention is to provide an improved supervisory system for detecting abnormal conditions at many locations by utilizing existing AC power supply lines without being affected by the noises and surge waves prevailing on the supply lines.
Still another object of this invention is to provide an improved supervisory system which is capable of detecting remotely located abnormal conditions by using terminal elements composed of passive elements and hence does not require any local power source.
A further object of this invention is to provide a new supervisory system for abnormal conditions wherein resonance elements are connected to AC power lines through an improved filter manifesting a high impedance to the frequency of the AC power line and a low impedance to the high frequency current utilized for detection.
According to this invention these and further objects can be accomplished by providing a supervisory system for detecting abnormal conditions affecting environmental security comprising electric power supply lines connected to a source of alternating current, high frequency oscillator means for transmitting high frequency currents of variable frequency over the power supply lines, a plurality of resonance elements having different resonance frequencies and connected across the power supply lines, a plurality of detectors responsive to abnormal conditions affecting environmental security, the detectors being associated with respective resonance elements so as to vary their resonance impedances in accordance with the abnormal conditions, a receiver connected to the power supply lines for receiving the high frequency currents after flowing through the resonance elements, means for causing the receiver to be operative only in the regions about the zero points of the AC voltage of the source and display means responsive to the output of the receiver for selectively displaying the abnormal conditions.
As will be described in detail later the novel supervisory system can supervise not only abnormal conditions of electrical apparatus, but also detect the change of state, for example ON and OFF states of a circuit breaker, or melting of a safety fuse, firehazard and smoke in buildings so that it is intended to cover all of them by the term abnormal condition."
BRIEF DESCRIPTION OF THE DRAWINGS Further objects and advantages of the invention can be more fully understood from the following detailed description taken in conjunction with the accompanying drawings in which:
FIG. 1 shows a connection diagram, partly in block form, of a supervisory system embodying the invention;
FIGS. 2 and 3 are waveforms useful to explain the operation of the supervisory system shown in FIG. 1;
FIG. 4 shows a connection diagram, partly in block form, of one embodiment of the invention;
FIG. 5 shows a connection diagram of a modified embodiment;
FIG. 6 shows a connection diagram of a resonance element in the form of an electromechanical type passive element and a coupling filter;
FIG. 7 shows a connection diagram of a resonance element and an abnormal condition detector;
FIG. 8 shows a connection diagram of a coupling filter;
FIG. 9 shows the detail of the electromechanical type passive element;
FIG. 10 shows an equivalent circuit of the electromechanical type passive element;
FIG. 11 is a plot showing the characteristics of the coupling filter and the resonance element;
FIG. 12 is a perspective view of fluorescent lamps and their supporting base incorporated with a resonance element and an abnormal condition detector utilized in this invention; and
FIG. 13 shows a perspective view of a casing, partly broken away, containing a resonance element and a detector.
DESCRIPTION OF THE PREFERRED EMBODIMENTS The environmental security supervising system illustrated in FIG. 1 comprises conventional, normally available power lines PL and PL connected across a source of alternating current 10 of a commercial frequency, a plurality of resonance elements L C R L C R Ln, Cn, Rn resonating to frequencies f f fn respectively and connected across the power lines. Switches 8,, S Sn operated by detectors Vs, are provided for short circuiting the resistance elements R,, R Rn of the respective resonance circuit elements in response to abnormal conditions. A variable frequency oscillator V, is connected across the power lines in the control center. The current I, supplied by the oscillator V; and passed through respective resonance elements is applied to a display device DIS through a current transformer CT connected in series with power line PL Thus, it is possible to supervise the states of various detectors Vs according to the resonance current characteristics as shown in FIG. 2. More particularly, the oscillator V; operates at one of a plurality of frequencies f,, f fn and it is assumed now that the oscillator V; is operating at a frequency f,. Under these conditions, the current supplied to the display device DIS varies from a low value shown by dotted lines when switch S, is open to a peak value when switch S, is closed. Accordingly, it is possible to determine whether an abnormal condition presents or not at a position for which frequency f, is assigned. The noise in conventional household distribution power supply lines caused by incandescent lamps, motors and household appliances connected thereto generally has a frequency of to 100 KHz and a level more than dBm, especially at the peak value of the supply voltage waveform exceeding 0 dBm. Actual measurement shows that the distribution of the noise is concentrated near the maximum amplitude of the voltage wave having a commercial frequency and that the noise is small near the zero value of the voltage wave. The impedance of the power lines is less than I50 ohms in the frequency range described above and decreases with frequency. Moreover the value of the line impedance is not stable. It is essential to correctly know these characteristics affecting noise, otherwise it is impossible to correctly display the state of remote locations by the current I, passing through the resonance elements installed at such locations.
For the effective operation of the supervisory system, in accordance with this invention, the operation of the receiver is automatically controlled in synchronism with the zero points of the AC voltage wave of the power line in accordance with the noise characteristic thereof so as to improve the S/N (signal to noise) ratio. More particularly, the receiver is controlled by a zero volt detector ZVS to act only in the shaded intervals RE around the zero points of the AC voltage wave as shown in FIG. 3. Thus, the receiver is made insensitive during remaining intervals.
Another feature of this invention lies in that the series resonance impedance of the resonance elements is decreased to a value less than a fraction of the line impedance when an abnormal condition occurs.
FIG. 4 shows one embodiment of the novel supervisory system which comprises a hybrid transformer 22 connected across the power lines PL, and PL and a high frequency oscillator 21 operating at variable frequencies, the output therefore being sent to the power lines through the hybrid transformer 22 as shown by solid line arrows. A plurality of resonance elements including resonators 27, 28 and 29 and information input switches or abnormal condition detectors 27s, 28s and 29s are connected across the power lines.
The high frequency current supplied by the oscillator 21 is supplied to a filter 23 of the receiver after passing through respective resonance elements and the hybrid transformer 22 as shown by dotted line arrows. Then, the received signal is applied to combined demodulator and subtracters 26 and 26 through channel filters 24 and 24 and amplifiers 25 and 25', and the outputs from the combined demodulator and subtracters 26 and 26' are displayed by display units S, and S of the display device 20. The oscillator 21 operates at the frequencies corresponding to those of the resonance elements 27, 28 and 29 connected across the power lines. The output of the oscillator 21 is transmitted over the power lines through the hybrid transformer 22 however the resonance elements manifest large losses due to their resistance components. The hybrid transformer HYB is in the form of a special three winding transformer or a phase inversion type transformer manifesting a relatively small loss for the received current in the direction of the dotted line arrows and functioning as a buffer between transmission and reception. The combined demodulator and subtracter, for example 26, produces the difference between the normal level of the received signal AFB obtained through the channel filter 23 associated therewith and the variation obtained by subtracting the loss caused by the resonance elements, that is the attenuation in the amplitude level of the output voltage from the hybrid transformer HYB, to obtain a stable output. At the same time, in the same manner as has been described in connection with FIG. 3, the time division reception control is performed in synchronism with the zero points of the AC voltage wave effected by zero voltage detector ZVS to improve the S/N ratio, and a timing output of the oscillator 21 is supplied to the combined demodulator and subtracter 26 through a circuit FFB which gives a preference to the display of the frequency in question at each zero point of the power supply frequency so that whether the display is caused by the fault of the transmitter or receiver, or by the noise is determined firstly, and then a display of the abnormal condition corresponding to that frequency is made. Thus, the zero point reception at high S/N ratio can be performed under a timing t,, I as shown in FIG. 2 in accordance with the transmission of the specified high frequencies from the oscillator 21 as the various high frequencies are continuously generated by controlling the oscillator means. In this example, the resonance element 28 includes two resonators for obtaining more accurate response to the ON and OFF caused by two frequencies.
In a modified embodiment shown in FIG. 5, there are provided a plurality of high frequency osciallators 31A, 31B 31Z respectively assigned with predetermined frequencies and the outputs from these oscillators are applied in regular sequence to one input terminal S of a high speed modulation switch 32 comprising bridge connected diodes, the other terminal N being connected to the receiver. The main terminal P of the modulation switch 32 is connected to the power line PL and the switch is keyed at a high speed by the output from a pulse oscillator 33 which is connected to an input terminal C of the modulation switch. More particularly, during an interval the outputs from the oscillators are applied to the power line PL as shown by a solid line arrow, while in the subsequent interval the high frequency current returned from the power line flows in the direction of a dotted line arrow, that is from point P to point N. This cycle of operation is repeated. The receiver comprises channel filters 34A, 34B 342 and combined amplifier and demodulators 35A, 35B 352 and the outputs of the demodulators are supplied to respective display units SA, SB S2 of the display device 30. Information input switches or abnormal condition detectors 36A, 36B 362 and resonance elements 37A, 37B 372 are connected to the power line PL.
In operation, the outputs from oscillators 31A, operation, 31B 312 are applied in regular sequence to resonance elements 378 and 372 where switches 36B and 36Z associated therewith are closed but not supplied to the resonance element 37A because the switch 36A associated therewith is open, as shown in FIG. 5. However, during the next interval since the power line is connected with the receiver through the modulation switch 32, the currents flowing through the resonance elements 378 and 372 are displayed by the display units SB and SZ. Although the zero voltage detector ZVS is not shown in FIG. 5, the noise suppression operation of the receiver is similar to that described in connection with FIG. 4.
FIGS. 6 through 11 show the detail of a resonance element. Thus, FIG. 6 shows a connection diagram of a resonance circuit in which filter 40 connected between power lines PL, and PL and resonance element 41 is illustrated as a constant-K filter which is connected with the resonance element 41 through an isolation transformer T. Preferably, the resonance element 41 for series resonance comprises an electromechanical type passive element capable of providing the capacitance and inductance shown in FIG. 1 as well as a large Q and having a wide frequency response. Such electromechanical type passive element may take the form of -a ceramic resonator made of quartz or titanium oxide.
The invention contemplates unique coordination between the high frequency characteristic and the low frequency characteristic and a DC component for the purpose of saving power and minimizing influence of hysteresis of the ceramic resonator. In the construction shown in FIG. 7, ceramic resonator 47 is connected in series with control element 46 comprising a resistor R which is shunted by a reed switch 49 operated by an abnormal condition detector 48. When the reed switch 49 is open, the impedance Z against the output of high frequency oscillator V f as viewed from the input terminals 5 and 6 of the resonance element 41 is reduced to that under a short circuited condition by the series resonance impedance of the ceramic resonator 47. When the reed switch 49 is closed by the detector 48 the resonance element 41 will manifest a short circuited impedance of only few ohms at the frequency of the oscillator. This means that the resonance element 41 resonates to the high frequency output of the oscillator V Since the power line PL are energized by a source of alternating current, in addition to the normal high AC voltage asymmetrical, DC components, higher harmonic waves and surge waves are also present on the power lines. For this reason, polarized elements such as electrostrictive resonator described above not only undergo severe aging but also their capability is lost due to an abnormal voltage wave. Accordingly, it is necessary to incorporate a coupling capacitor C so as to render the AC voltage to become negligibly small or to manifest a high impedance, as shown in FIG. 8. The coupling filter 40 and the resonance element 41 are constructed to satisfy the features of FIGS. 7 and 8 so that the short circuited impedance manifested by the resonance element 47 shown in FIG. 7 can appearon By separating real and imaginary parts of this equation and by putting nv m j nv we obtain where K represents a constant.
In equation (1) by putting R 0,
Thus, the frequency at which the impedance becomes zero is shown by X,=0, X +Z X =O Substituting equations (4) and (5) in an equations f f 2 This means that the value of the short circuited impedance becomes a minimum at frequencies f and f The short circuited impedance Zs is shown by a dotted line curve in FIG. 11. The impedance of the resonance element 41 is shown by a solid line curve 47 which means that the characteristic of the series resonance can be effectively manifested through the characteristic of the coupling filter 40.
FIG. 9 shows the construction of the electromechanical type passive element of the resonance element 41 and FIG. 10 shows an equivalent circuit of the electromechanical type passive element.
In FIG. 9, the passive element is depicted as a converter TD and its terminal impedance as M00. As is well known in the art, a electromechanical passive element can be shown by an equivalent circuit comprising a capacitor s representing its stiffness, a reactor m representing its mass near the resonance frequency, and a resistor r which are connected in series as shown in FIG. 10. These constants are determined depending upon the position of the passive element, and the force acting upon the passive element corresponds to the current flowing through the series circuit. The vibration mode is determined by the equivalent circuit consisting of serially connected elements m, s and r.
Accordingly, the frequency at which the series impedance of the elements m, s and r becomes a minimum is the resonance frequency. According to this invention, the input impedance Z may be interlocked with another information source so as to use it as a mechanical terminal resistor which displaces mechanically the vibrator.
FIGS. 12 and 13 show a perspective view of still another modification of this invention wherein an abnormal condition detector Vs and a resonance element 51 are incorporated into an electric apparatus, for example a fluorescent lamp. As shown a casing 52 containing a detector Vs and a resonance element 51 is attached to one socket of a fluorescent lamp LP mounted on a ceiling.
By mounting the detector at a position suitable to be subjected to the heat of the lamp and to the flow of heated air or smoke the detector can detect at a high sensitivity the abnormal condition. Moreover, this construction simplifies the mounting of the detector and the resonance element. This construction can also be applied to an emergency lamp, a bracket for supporting an incandescent lamp, and various types of household appliances.
The novel supervisory system can also be used to detect the abnormal condition of the area in which distribution lines are installed.
As is well known in the art, it has been difficult to supervise at the control center such informations as the OFF and ON states of section switches connected in a three wire distribution system the melting of a fuse attached to a pole transformer, and the breakage of the line.
The novel supervisory system can meet such requirements. For example, by constructing the detector such that an electrical unbalance is caused by such troubles or change of state it is possible to send a signal for operating a display device or a relay adapted to operate a circuit breaker.
As described herein above, according to this invention a plurality of resonance elements resonating at different frequencies are associated with respective abnormal condition detectors it is possible to readily determine at the control center the location of trouble as well as the magnitude of the hazard thereby facilitating a proper control and command for suppressing the hazard. Moreover, as the existing distribution lines are utilized it is not necessary to install independent signal lines and since the resonance elements are composed of only passive elements it is not necessary to use any local source of power.
What is claimed is:
l. A supervisory system for detecting abnormal conditions affecting environmental security comprising electric power supply lines connected to a source of alternating current, high frequency oscillator means for transmitting high frequency currents of variable frequency over said power supply lines, a plurality of resonance elements having different resonance frequencies and connected across said power supply lines, a plurality of detectors responsive to the abnormal conditions affecting environmental security, said detectors being associated with respective resonance elements so as to vary their resonance impedances in accordance with said abnormal conditions, a receiver connected to said power supply lines for receiving said high frequency currents after flowing through said resonance elements, means for causing said receiver to be operative only in the regions about the zero points of the AC voltage of said source, and display means responsive to the output of said receiver for selectively displaying said abnormal conditions.
2. The supervisory system according to claim 1 wherein said high frequency oscillator means produces a continuously variable high frequency.
3. The supervisory system according to claim 1 wherein said high frequency oscillator means comprises a plurality of separate oscillators operating at different frequencies.
4. The supervisory system according to claim 1 further including a hybrid three winding transformer having one of the windings thereof connected across said power supply lines, a second winding connected across the output from said high frequency oscillator means and a third winding connected across the input of said receiver.
5. The supervisory system according to claim 1 wherein each resonance element comprises a series res onance circuit and a resistor connected in series therewith, and said detector is connected in parallel with said resistor for short circuiting the same in response to said abnormal condition.
6. The supervisory system according to claim 1 wherein said resonance element comprises an electromechanical type passive element and a resistor connected in series therewith and said detector is connected in parallel with said resistor for short circuiting said resistor in response to said abnormal condition.
7. The supervisory system according to claim 1 wherein said detector and said resonance element are incorporated into an electric apparatus which has been loaded at the terminal of said electric power supply mes.
8. The supervisory system according to claim 1 wherein said receiver includes a combined demodulator and subtractor which is controlled by a zero point detector connected to said source for detecting the zero point of the voltage wave of said source.
9. The supervisory system according to claim 7 wherein said combined demodulator and subtractor is controlled by a timing output of said high frequency oscillator means so that said display means preferentially displays the abnormal condition sensed by a detector and a resonance element which is tuned to a particular frequency at which said high frequency oscillator means 15 operating.
10. The supervisory system according to claim 1 wherein a high speed modulation switch controlled by a pulse and comprised by bridge connected diodes is interposed between said high frequency oscillator means, said power supply means and said receiver so as to connect said power supply lines alternately to said high frequency oscillator means and said receiver.
11. The supervisory system according to claim 1 wherein said resonance element is connected to said power supply lines through a filter which manifests a high impedance against the frequency of said source and a low impedance against the frequency at which said high frequency oscillator means operates.
12. The supervisory system according to claim 10 wherein said filter is connected to said power supply lines through a coupling capacitor which blocks the flow of a DC component.