JPH0423488B2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Technical Field This invention provides a water leakage alarm that detects water leakage within electrical equipment used underwater or within a conductor that supplies power to the electrical equipment from above the water and issues an alarm to the outside. Regarding circuits.

(b) Background of the Invention When water leaks in electrical equipment used underwater or in conductors that supply power to the electrical equipment from above water,
Electrical leakage may occur to underwater workers using electrical equipment, but electrical leakage to workers while working underwater is relatively low-power and can lead to paralysis or, in the worst case, death to the worker.

(c) Purpose of the Invention The purpose of the present invention was made in view of the above-mentioned circumstances, and it automatically prevents water from leaking inside electrical equipment or power supply conductors (cables) when it becomes dangerous. It is an object of the present invention to provide a water leakage alarm circuit capable of warning the outside about the state of water and ensuring the safety of underwater workers.

(d) Structure of the Invention This invention covers the outside of the insulation coating of a power supply conductor that supplies electric power from the water to electrical equipment used underwater with another conductor, and connects one end of this conductor to the case of the underwater electrical equipment. The other end is connected to the midpoint potential of the power line with high impedance on the power supply side above the water, and an absolute value amplification circuit that amplifies the potential of the conductor to an absolute value, and the amplified output is a constant value. When water leaks occur, a potential difference is created between the power supply conductor and another conductor covering the outside of its insulation coating, and the potential difference is expressed as an absolute value. It is designed to issue an alarm when the amplified value reaches a certain level.

(e) Embodiment FIG. 1 is a circuit diagram of a water leak alarm circuit according to an embodiment of the present invention.

In the figure, 1 is a case of underwater electrical equipment. Usually no power lines are directly connected. Reference numeral 2 denotes electrical elements such as an electrical circuit and a motor arranged inside the case. 3a and 3b are power supply conductors for supplying power to the electric element 2 from above the water, and are connected to a positive power line 4a and a negative power line 4b, respectively, of an alarm circuit placed above the water. A cable 5 covers the outside of the insulating coating (not shown) of the power supply conductors 3a and 3b, and is made of a conductor and has one end connected to the case 1. Reference numeral 6 denotes an inlet for the cable to the underwater electrical equipment, and is subjected to some kind of watertight treatment by known means.

In alarm circuits located above water, power line 4
Resistors R5 and R6 of the same value are connected in series between a and 4b to form a midpoint potential point M. Note that the resistors R5 and R6 are constructed with low resistance, and a relatively large current flows through their series circuit, so that the potential at the midpoint potential part M point is always E/2 without being affected by the operating state of other circuits. I try to maintain an intermediate potential between the two. The other end of cable 5, point S, has high resistance R1
It is connected to the above-mentioned point M via , and is also connected to the input side of the absolute value amplification circuit C1. The absolute value amplifier circuit C1 includes resistors R2, R3, R4, diodes D1, D2, D3, D4, and an operational amplifier.
It consists of OP and amplifies the absolute value of the positive or negative signal input to resistor R2.

The output of the absolute value amplification circuit C1 is connected to the input side of the alarm lamp lighting circuit C2. The alarm lamp lighting circuit C2 includes a Zener diode ZD that conducts when the output voltage of the operational amplifier OP exceeds a certain voltage, a lamp drive transistor TR that turns on when the Zener diode ZD conducts, and a lamp that lights when this transistor TR turns on. It is composed of P.

With the above configuration, cable 5 can now be used for underwater electrical equipment.
Assuming that there is no water ingress and there is no current leakage, the S point and the positive and negative input terminals of the operational amplifier OP are connected to M.
The potential is the same as that at the point, and the diodes D1 and D2 become non-conductive. Therefore, the transistor TR of the alarm lamp lighting circuit C2 remains off, and the lamp P does not light up. However, if underwater electrical equipment or cables are flooded and the power supply conductor 3a connected to the positive power line 4a is electrically connected to the cable 5 through a low resistance material such as seawater, The S point has a higher potential than the M point. Therefore, a current flows through the resistor R2, the diode D2, and the resistor R3, and the potential at the positive input terminal of the operational amplifier OP rises. Therefore, the potential at the output terminal of the operational amplifier OP also rises, and when that potential exceeds the Zener potential of the Zener diode ZD, the transistor
TR turns on and lamp P lights up. Furthermore, when the power supply conductor 3b connected to the negative power line 4b is electrically connected to the cable 5 due to flooding, the potential at point S becomes lower than point M, and resistor R3, diode D1, and resistor R2 A current flows and the potential at the output terminal of the operational amplifier OP rises. In this case as well, when the increased voltage exceeds the Zener voltage, the lamp P lights up. zener diode
The Zener voltage of the ZD is set to a level that allows conduction when the output voltage of the operational amplifier OP rises to a level that poses a risk of electric shock to underwater workers due to water immersion. In other words, if water intrudes into underwater electrical equipment or cables and a current leakage occurs from the power supply conductor 3a or 3b side to the extent of causing an electric shock to an underwater worker, the lamp P will be turned on in the underwater alarm circuit. .

Considering the risk of electric shock, it is desirable to supply power to underwater electrical equipment with a low-voltage power supply, but if it is unavoidable to use a high-voltage DC power supply, use resistors with large allowable power, and As shown in Figure 2, resistors R8 and R9 and Zener diode ZD2 are added to protect the operational amplifier OP. If the power supplied to the power lines 4a, 4b is AC, diodes D5, D6 and a capacitor C are added as shown in FIG.

(f) Effects of the Invention As described above, according to the present invention, it is possible to detect a dangerous situation when a leakage occurs due to water intrusion in underwater electrical equipment or the power supply conductor that supplies power to the electrical equipment from above the water. Automatic warnings are issued to ensure safety during underwater work. In addition, on the underwater side, it is only necessary to provide another conductor to cover the outside of the insulation coating of the power supply conductor.
Reliability can be increased, and the circuit configuration can be combined with an absolute value amplification circuit, an alarm circuit, and other simple circuits, making it smaller and lighter.
It also has the advantage of being low cost.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a water leak alarm circuit according to an embodiment of the present invention, and FIGS. 2 and 3 are diagrams showing other circuit examples of a part of the water leak alarm circuit. 3a, 3b...Power supply conductor, 5...Cable (another conductor), C1...Absolute value amplification circuit, C2...
Alarm lamp lighting circuit.

Claims (1)

[Claims] 1. Cover the outside of the insulation coating of the power supply conductor that supplies power to electrical equipment used underwater from above the water with another conductor, connect one end of this conductor to the case of the underwater electrical equipment, and connect the other end to the case above the water. An absolute value amplification circuit that connects to the midpoint potential of the power line with high impedance on the power supply side and amplifies the absolute value of the potential of the conductor, and an alarm circuit that issues an alarm when the amplified output exceeds a certain value. A water leakage alarm circuit for equipment used underwater, characterized by comprising: