KR101360137B1 - Safety jumper equipment - Google Patents

Abstract

The present invention provides a safety jumper device including a safety jumper device A and a safety jumper device B. The safety jumper device A is internally mounted with a main control circuit, a fuse, a switch, and a power source; runs a high-voltage detection and alarm function, a high-voltage protection function, and a test switch-off function; is externally mounted with a polarized indicating lamp, an AC high-voltage indicating lamp, a high-voltage indicating lamp, a test ready indicating lamp, a test switch, and a power switch; and has a contact tip at the tip end. The safety jumper device B is joined to the safety jumper device A using a cable; is internally mounted with a fuse; has an alarm function; is externally mounted with a polarized indicating lamp and an AC high-voltage indicating lamp; and has a contact tip at the tip end.

Description

Safety Jumper Equipment

The present invention is to connect the alarm generating contact point in the security field alarm test of power equipment and industrial facilities, alarm test work of power plants and power stations, large capacity consumer power equipment, industrial equipment, or other electrical and electronic logic signal It relates to a safety jumper that can ensure the safety of workers and equipment in the work of the jumper wire during the test to deliver the.

Currently, power plants (hydropower, thermal power, nuclear power, combined cycle, etc.), power stations, and industrial facilities stop alarms and prevent circuits from spreading and spreading accidents by quickly and safely stopping the relevant facilities as well as all related facilities. In order to periodically test and verify the integrity of the circuit, an alarm test is conducted to check whether an alarm occurs by artificially connecting the circuit using jumper wires.

This conventional alarm test method uses simple jumper wires (short wires for connecting circuits) to connect circuits, but if an operator accidentally connects another circuit with a jumper wire, an accident occurs. In other words, when the power circuit is connected with a jumper wire, a short circuit occurs, causing an electric shock and burn of the worker and damage to the equipment. In addition, if the protection circuit is connected with a jumper wire, power equipment and other industrial equipment such as a generator transformer in operation are stopped at an unexpected time, and in the case of power equipment, the grid voltage and frequency may fluctuate, and the possibility of expanding to limited power transmission if severe. In addition, there is a problem that serious damage occurs in various other industrial facilities.

Therefore, the present invention has been made to solve the above-mentioned conventional problems, the operation of connecting the alarm generating contact during the security field alarm test of power equipment and industrial equipment, power plants and power stations, power equipment of large capacity customers, industrial equipment, etc. Its purpose is to provide a safety jumper to ensure the safety of operators and equipment in the operation of jumper wires during the alarm test operation of the test or the test that transmits signals to other electrical and electronic logic.

That is, the present invention, in order to prevent damage caused by emergency stop of power equipment and industrial equipment and safety accident of the operator during the alarm test, the current of several currents required for the alarm test flows and several A current required for the protection circuit operation. Thousands of amperage generated in the event of short circuit and power supply circuit can be suppressed to several tens of thousands or less to prevent accidents, and limit the current to prevent equipment and human accidents from occurring when contacting AC and DC power circuits. In case of anticipated behavior (i.e. contact with high voltage circuit such as power circuit and protection circuit, in case of contacting while pressing test switch first and ignoring high voltage alarm and cutoff function), prevent accident It is intended to provide a safety jumper that turns on a warning light when only one side of the jumper wire is in contact with the AC voltage.

In order to achieve the above object, the safety jumper according to the present invention includes a main control circuit, a fuse, a switch, and a power supply, and performs a high voltage detection and alarm generation function, a high voltage breaking function, and a test switch blocking function. A safety jumper A having a polarity indicator, an AC high voltage indicator, a high voltage indicator, a test ready indicator, a test switch, and a power switch, each having a contact tip installed at its tip; The safety jumper A is fixedly connected to each other by a cable, and includes a fuse and an alarm generating function, and includes a safety jumper B having a polarity indicator and an AC high voltage indicator on its exterior and a contact tip installed at its tip. Characterized in that configured.

On the other hand, the safety jumper according to the present invention, the extension of the safety jumper A and the tip of the safety jumper A, the extension line A having a polarity indicator and a test switch on its exterior and a contact tip is installed on its tip; The safety jumper B and the tip of the safety jumper B is detachably coupled to each other, and has a polarity indicator on its appearance and is further provided with an extension line B is installed on the tip, wherein the extension line A and the extension line B is It is used when the safety jumper A and the safety jumper B is connected to a circuit where it is difficult to access, or when the safety jumper A and the safety jumper B is short and cannot be connected.

Here, the safety jumper A operates even when the power switch is turned off, and when the tip of the safety jumper A is brought into contact with an AC power line (power terminal), the high current indicator flashes to drive by detecting a charging current. An AC high voltage alarm circuit for simultaneously lighting the polarity indicators when the voltage is higher; When the control power of the safety jumper A is low, the function of the high voltage detection circuit is stopped, thereby preventing the connection of the test circuit to protect the safety jumper, the equipment and the operator, and while pressing the test switch, alarm the tip of the safety jumper A. A power supply and an interlock circuit that protects the safety jumper, the equipment, and the operator by preventing an overcurrent from flowing in the alarm circuit alarm generation current setting resistance when the terminal contacts a terminal exceeding a circuit voltage; Rectifies AC and DC voltages and sends them to the high voltage detection circuit, cuts off the test circuit when there is a high voltage alarm, protects the equipment and workers, and bypasses the high voltage detection circuit with the test switch when there is no high voltage alarm to flow an alarm-current. Rectification / test blocking / test circuits; A high voltage sensing circuit configured to sense a voltage exceeding a set voltage of the AC high voltage warning circuit; A high voltage alarm generation and blocking circuit for generating an alarm and interrupting a test circuit when the high voltage signal is detected by the high voltage detection circuit; It is preferable to incorporate a polarity display circuit which lights the polarity indicators according to the polarity of the terminals with which the tip of the safety jumper A is in contact.

In addition, the safety jumper B operates even when the power switch is turned off, and when the tip of the safety jumper B is brought into contact with an AC power line (power supply terminal), the safety current is sensed and driven to flash the AC high voltage indicator. An AC high voltage alarm circuit for simultaneously lighting the polarity indicators when the voltage is higher; An alarm circuit alarm generation current setting resistor which is provided at a connection portion of the safety jumper A and sets a magnitude of a resistance so that a minimum current required for the AC high voltage alarm circuit flows; It is preferable that a polarity display circuit is built in which the polarity indicators are lighted according to the polarity of the terminal with which the tip of the safety jumper B is in contact.

In addition, the extension line A has a polarity display circuit for distinguishing and lighting the polarity indicators according to the polarity of the terminal with which the tip of the extension line A is in contact. The extension line B is preferably interlocked with the power supply and the interlock circuit of the base A. The extension line B preferably includes a polarity display circuit which lights the polarity indicators according to the polarity of the terminal with which the tip of the extension line B is in contact.

According to the present invention configured as described above, the current of several currents required for the alarm test flows, and the several A currents necessary for the protection circuit operation and the thousands of A currents generated when the power supply circuit is short-circuited are suppressed to several tens or less. To prevent accidents, limit the current so that equipment and human accidents do not occur when contacting AC and DC power circuits, and contact high voltage circuits such as power circuits and protection circuits when equipment and human accidents are expected. In case of contacting while pressing the test switch first, ignoring the high voltage alarm and interruption function), cut off the test circuit to prevent accidents, and if only one side of the jumper wire comes into contact with AC voltage, the warning lamp turns on. It is possible to prevent damage caused by emergency stop of facilities and industrial facilities and to prevent safety accidents of workers.

1 is an external configuration diagram of a safety jumper according to the present invention.
2 is a circuit diagram of a safety jumper according to the present invention.
3 is a view showing the operation of the safety jumper according to the present invention and the LED lighting state, Figure 3a is a view showing the operation of the safety jumper according to the contact position and the LED lighting state of the present invention in normal operation; 3B is a view showing whether the safety jumper of the present invention when the polarity is changed when the normal operation and LED lighting state, Figure 3c is a view showing the operation of each situation and LED lighting state when the control power abnormal state. FIG. 3D is a view illustrating whether the LED is turned on or not depending on the situation when the terminal is in contact with the terminal block while pressing the test switch first.
4 is a view for explaining a problem when using a conventional general jumper wire.
5 is a view for explaining the advantages when using the safety jumper according to the present invention.

Hereinafter, a safety jumper according to the present invention will be described in detail with reference to the accompanying drawings.

1 is an external configuration diagram of a safety jumper according to the present invention.

As shown in the figure, the safety jumper according to the present invention is composed of an extension line A (10), a safety jumper A (20), a safety jumper B (30) and an extension line (B 40). Here, the safety jumper A (20) and the safety jumper B (30) is fixed to each other by a cable, the safety jumper A (20) and the extension line A (10) is detachably coupled to each other, the safety jumper The base B 30 and the extension line B 40 are also detachably coupled to each other.

The safety jumper A 20 has a main control circuit, a fuse, a switch, and a power supply, and performs a high voltage detection and alarm generation function, a high voltage blocking function, a test switch blocking function, and a polarity indicator (LED1, LED2), An AC high voltage indicator LED7, a high voltage indicator LED5, a test ready indicator LED6, a test switch T23, and a power switch 22 are provided.

The safety jumper B 30 includes a fuse, an alarm circuit, and a current regulating resistor, and has polarity indicators LED3 and LED4 and an AC high voltage indicator LED8.

The extension line A 10 and the extension line B 40 are used to connect a circuit in a place where the safety jumper A 20 and the safety jumper B 30 are difficult to access, or the safety jumper A 20. Used when safety jumper B (30) is too short to connect. The extension line A 10 includes polarity indicators LED9 and LED10 and a test switch 11, and the extension line B 40 includes polarity indicators LED11 and LED12.

The use method of the safety jumper of this invention comprised in this way is demonstrated.

Turn on the power switch 22 installed in the safety jumper A (20) and press the tip (21) of the safety jumper A (20) to check whether the test ready indicator (LED6) is lit.

In addition, when the tip 21 of the safety jumper A 20 is pressed while the power switch 22 of the safety jumper A 20 is turned on and the test switch 23 is operated, the test ready indicator (LED6) ) Does not light up. At this time, when the test ready indicator (LED6) lights up, the jumper interlock circuit is abnormal, so check the interlock circuit of the safety jumper A (20).

In addition, when the extension line A 10 is used, the tip 11 of the extension line A 10 is turned on while the power switch 22 of the safety jumper A 20 is turned on and the test switch 12 of the extension line A 10 is operated. When () is pressed, check that the test ready indicator (LED6) does not light up. At this time, when the test ready indicator (LED6) lights up, the jumper interlock circuit is abnormal, so check the interlock circuit of the safety jumper A (20).

In addition, the tip 31 of the safety jumper B (30) in contact with the alarm generating terminal to check whether the AC high voltage indicator LED8 is blinking. At this time, if the AC high voltage indicator LED8 blinks, the related terminal is an AC high voltage circuit, and the tip 31 of the safety jumper 30 in contact is immediately separated from the terminal block and the related circuit is examined.

Meanwhile, if the AC high voltage indicator LED8 of the safety jumper B 30 does not blink, the tip 21 of the safety jumper A 20 also contacts the terminal, and then the AC high voltage indicator LED7 blinks. Check that the high voltage indicator (LED5) is on and the buzzer sounds.

At this time, if the indicators (LED7, LED5) is flashing or not lit, press the test switch 23 to generate an alarm, and check the alarm circuit for abnormality.

Here, the jumper in which the red indicators (LED1, LED3) are lit is + polarity, and the safety jumper in which the blue indicators (LED2, LED4) are lit is-polarity, and the red and safety jumper is on the safety jumper A (20). It is normal when the blue light on the B 30 or the opposite color light on. On the other hand, if the red and blue lights on each safety jumper are turned on at the same time, examine the circuit of the equipment.

On the other hand, if the safety test space is narrow and the safety jumper A (20) is not available to use the extension line A (10) connected, if necessary, the extension line B (40) is also used to connect.

2 is a circuit diagram of a safety jumper according to the present invention.

In the figure, reference numeral 1 denotes an AC high voltage alarm circuit 1, which is provided in safety jumpers A and B 20 and 30, respectively, and operates even when there is no internal battery or the power switch 22 is turned off. When the tip 21 of safety jumper A (20) D is contacted with AC power line (power terminal), it is a circuit to sense and drive the charging current and the indicators (LED7, LED8) blink and if the voltage is higher, (LED1, LED2; LED3, LED4) also light up at the same time.

Reference numeral 2 denotes a power supply and an interlock circuit, which is provided in the safety jumper A 20, and the safety jumper A 20 and the extension line are combined even when the safety jumper A 20 and the extension line A 10 are coupled. When the function of the high voltage detection circuit 4 is stopped because the control power supply of the safety jumper A 20 is low because the control power supply of the safety jumper A 20 is stopped, the relay RR is turned off to disconnect the test circuit. To protect safety jumpers, equipment and workers. In addition, the power supply and interlock circuit 2 contacts the tip 21 of the safety jumper A 20 to a terminal exceeding the alarm circuit voltage while the test switch is pressed, that is, the high voltage sensing circuit 4 operates. All test circuits are configured to protect the safety jumpers, equipment and operators by preventing overcurrent from flowing through the alarm circuit alarm generating current setting resistor (R1) (6). In addition, the power supply and interlock circuit (2) is designed so that the alarm generating current setting resistor (R1) (6) and other components have no problem in the short voltage contact in the low voltage circuit, but overheating may occur or the LED and fuse may be burned out for a long time. This is an additional safety device to protect workers, equipment and safety jumpers.

In addition, reference numeral 3 denotes a rectification / test cutoff / test circuit, which is provided in the safety jumper A 20, rectifies AC and DC voltages, and sends them to the high voltage detection circuit 4, when there is a high voltage alarm. To protect equipment and workers, and bypass high voltage detection circuit (4) with a test switch when there is no high-pressure alarm to flow the alarm generation current.

In addition, reference numeral 4 denotes a high voltage sensing circuit, which is provided in the safety jumper A 20 and senses a voltage exceeding the set voltage of the AC high voltage warning circuit 1.

In addition, reference numeral 5 denotes a high voltage alarm generation and blocking circuit, which is provided in the safety jumper A 20. When the high voltage detection circuit 4 detects a high voltage signal, the signal is converted into a digital signal to generate an alarm. The test circuit is interrupted by driving a relay.

In addition, reference numeral 6 denotes an alarm circuit alarm generation current setting resistor, which is provided at the connection portion of the safety jumpers A and B (20, 30), so that the minimum current required for the AC high voltage alarm circuit 1 flows. Set the size.

Reference numeral 7 denotes a polarity display circuit, which is provided on the safety jumpers A and B (20 and 30) and the extension lines A and B (10 and 40), respectively. ) Or the extension line A, B (10, 40) to indicate the polarity of the circuit voltage contacted, the + pole is lit red indicators (LED1, LED3, LED9, LED11), the-pole is blue indicator (LED2) , LED4, LED10, LED12 are turned on, and in case of AC voltage, the red and blue indicators (LED1, LED2; LED3, LED4; LED9, LED10; LED11, LED12) are turned on at the same time.

Reference numeral 8 denotes a protective fuse and is provided on the safety jumpers A and B (20 and 30) and the extension lines A and B (10 and 40), respectively.

3 is a view showing whether the operation of the safety jumper according to the present invention and the LED lighting state.

Figure 3a is a view showing the operation of the safety jumper according to the contact position and the LED lighting state of the present invention in normal operation, when the safety jumper is connected to the alarm terminal, the equipment trip terminal or the AC high voltage terminal, When only the tip 21 of the A (20) is connected to the terminal block, when only the tip 31 of the safety jumper B (30) is connected to the terminal block, and the tip of the safety jumper A, B (20, 30) LEDs that light up when both (21, 31) are connected to the terminal block, when the tip (21) of the safety jumper A (20) is connected to the terminal block, and then pressed, and when the test switch is pressed. A diagram showing the state of the test operation and whether or not the operation.

3B is a view showing whether the safety jumper of the present invention when the polarity is changed and the LED lighting state in normal operation, when the safety jumper is connected to an alarm terminal, a facility trip terminal or an AC high voltage terminal, When only the tip 21 of the machine A 20 is connected to the terminal block, when only the tip 31 of the safety jumper B 30 is connected to the terminal block, and the safety jumper A, B (20, 30) Indicator lamps that light up when both tips 21 and 31 are connected to the terminal block, when the tip 21 of the safety jumper A 20 is connected to the terminal block, and then pressed, and when the test switch is pressed. ) Is a diagram showing the state of and the test contact operation.

FIG. 3C is a view illustrating operation of each situation and LED lighting state when the control power supply is abnormal. When the safety jumper is connected to an alarm terminal, a facility trip terminal, or an AC high voltage terminal, FIG. When only the tip 21 is connected to the terminal block, when only the tip 31 of the safety jumper B 30 is connected to the terminal block, and the tips 21 and 31 of the safety jumpers A and B (20 and 30). The status and test contacts of the LEDs that light up when the terminals are connected to the terminal block, when the tip 21 of the safety jumper A 20 is connected to the terminal block, and when the test switch is pressed. It is a figure which shows operation | movement.

Figure 3d is a diagram showing the operation of each situation and the LED lighting state when contacting the terminal block while pressing the test switch first, when the safety jumper is connected to the alarm terminal, the equipment trip terminal or the AC high voltage terminal, When only the tip 21 of the A (20) is connected to the terminal block, when only the tip 31 of the safety jumper B (30) is connected to the terminal block, and the tip of the safety jumper A, B (20, 30) It is a figure which shows the state of the indicator LED which lights each, and whether test contact operation | movement is connected, when both (21, 31) are connected to a terminal block.

Next, with reference to FIG. 4, the problem at the time of using the conventional general jumper wire is demonstrated.

First, when the alarm generating terminal is connected with a jumper wire (A1 in FIG. 4), a normal operation of generating an alarm in the field control panel and the monitoring panel is performed (A2 in FIG. 4).

In addition, when the emergency stop terminal is connected with a jumper wire (B1 in FIG. 4), a lockout relay based on a transformer protection relay operates (B2 in FIG. 4), and the breaker is disconnected by a breaker open (trip) signal generated from the lockout relay. Open (B3 of FIG. 4), the breaker is open, the power transmission is impossible even if the generator and transformer is not abnormal (B4 of FIG. 4).

In addition, when the power terminal is connected with a jumper wire (C1 in FIG. 4), the jumper wire burns out at the moment of connecting the jumper wire, causing a three-phase short-circuit accident (large current accident), and a human injury occurs due to electric shock and burns. The control panel power failure (C2 in FIG. 4) occurs due to the transformer field control panel burnout and AC 480 power off, and the transformer temperature rises due to the transformer cooling fan and oil pump motor power off (C3 in FIG. 4), and protects the transformer from overheating. In order to do this, the output must be artificially lowered.

Next, with reference to Figure 5 will be described the advantages of using the safety jumper according to the present invention.

First, when the emergency stop terminal is connected to the safety jumper (D1 of FIG. 5), the high-pressure warning light is turned on, an alarm sound is generated, and the internal OVR (OverVoltage Relay) of the safety jumper A 20 is excited ( D2 of FIG. 5). At this time, even if the test switch is ignored and the test switch is pressed, the OVR contact blocks the circuit. In addition, in order for the lockout relay to operate, several A currents must flow, but only 10 mA or less current flows (D3 in FIG. 5). In addition, the breaker is kept in the input state, and the generator output can be transmitted to the grid.

In addition, when the 480V power terminal is connected with the safety jumper (E1 in FIG. 5), the AC high-pressure warning light is turned on in the safety jumper (safety jumper A or B) connected first, and when the remaining jumper is hardened, The warning lamp is on, the high voltage warning lamp is on, the alarm sound is generated and the OVR excitation inside the safety jumper A is generated. At this time, even if the test switch is pressed and the test switch is ignored, the contact of the OVR cuts off the circuit, and the current is limited to several tens of kΩ or less by the internal resistances R1, R2, R3 and ZD1 (TVS) of the jumper. The process of the furnace is blocked and no problems are caused to the installation.

As described above, according to the present invention, the current of several currents necessary for the alarm test flows, and the current of several As necessary for the protection circuit operation and the thousands of A currents generated when the power supply circuit is short-circuited is suppressed to several tens or less. To prevent accidents, limit the current so that equipment and human accidents do not occur when contacting AC and DC power circuits, and contact high voltage circuits such as power circuits and protection circuits when equipment and human accidents are expected. In case of contacting while pressing the test switch first, ignoring the high voltage alarm and interruption function), cut off the test circuit to prevent accidents, and if only one side of the jumper wire comes into contact with AC voltage, the warning lamp turns on. It is possible to prevent damage caused by emergency stop of facilities and industrial facilities and to prevent safety accidents of workers.

Therefore, by using the safety jumper according to the present invention, it is possible to prevent the uninterrupted power equipment during the alarm test of power plants, such as nuclear power, thermal power, hydropower, etc. It is possible to prevent the power failure caused by the power failure, to prevent the uninterrupted operation of the equipment even in the alarm test of the industrial equipment, and to prevent the loss of equipment and human accidents caused by the jumper of the high voltage circuit.

The present invention is not limited to the above-described specific embodiments, and various modifications and changes may be made without departing from the gist of the present invention. It will be obvious that such modifications and variations are included in the appended claims.

1: AC high voltage alarm circuit 2: power supply and interlock circuit
3: Rectification / test cutoff / test circuit 4: High voltage detection circuit
5: High voltage alarm generation and breaking circuit 6: Alarm circuit Alarm generation current setting resistance
7: polarity display circuit 8: protective fuse
10: extension line A 11: tip of extension line A
12: test switch of extension wire A 20: safety jumper A
21: Tip of the safety jumper A 22: power switch
23: test switch of safety jumper A 30: safety jumper B
31: Tip of safety jumper B 40: Extension line B
41: tip of extension line B

Claims (5)

Built-in main circuit, fuse, switch and power supply, performs high voltage detection and alarm function, high voltage cut off function and test switch cut off function, and the polarity indicator, AC high voltage indicator, high voltage indicator, test preparation A safety jumper A having a completion indicator, a test switch, and a power switch and a contact tip installed at its tip;
The safety jumper A is fixedly connected to each other by a cable, and includes a fuse and an alarm generating function, and includes a safety jumper B having a polarity indicator and an AC high voltage indicator on its exterior and a contact tip installed at its tip. Safety jumper, characterized in that configured. The method of claim 1,
An extension line A configured to be detachably coupled with the tip of the safety jumper A, and having a polarity indicator light and a test switch on an exterior thereof, and a contact tip installed at a tip thereof;
The safety jumper B is configured to be detachably coupled with each other, and further includes an extension line B having a polarity indicator on its appearance and a contact tip installed at its tip.
The extension line A and the extension line B are used for connecting a circuit in a place where the safety jumper A and the safety jumper B are difficult to access, or when the safety jumper A and the safety jumper B are short and cannot be connected. Safety jumper characterized in that. 3. The method of claim 2,
The safety jumper A operates even when the power switch is turned off, and when the tip of the safety jumper A is brought into contact with an AC power line (power terminal), it senses and operates the charging current to drive the AC high voltage indicator flashing. An AC high voltage alarm circuit for simultaneously turning on the polarity indicator if higher than this;
When the control power of the safety jumper A is low, the function of the high voltage detection circuit is stopped, thereby preventing the connection of the test circuit to protect the safety jumper, the equipment and the operator, and while pressing the test switch, alarm the tip of the safety jumper A. A power supply and an interlock circuit that protects the safety jumper, the equipment, and the operator by preventing an overcurrent from flowing in the alarm circuit alarm generation current setting resistance when the terminal contacts a terminal exceeding the circuit voltage;
Rectifies AC and DC voltages and sends them to the high voltage detection circuit, cuts off the test circuit when there is a high voltage alarm, protects the equipment and workers, and bypasses the high voltage detection circuit with the test switch when there is no high voltage alarm to flow an alarm-current. Rectification / test blocking / test circuits;
A high voltage sensing circuit configured to sense a voltage exceeding a set voltage of the AC high voltage warning circuit;
A high voltage alarm generation and blocking circuit for generating an alarm and interrupting a test circuit when the high voltage signal is detected by the high voltage detection circuit;
A safety jumper comprising a polarity display circuit for distinguishing and lighting the polarity indicator according to the polarity of the terminal with which the tip of the safety jumper A is in contact. The method of claim 3,
The safety jumper B operates even when the power switch is turned off, and when the tip of the safety jumper B is brought into contact with an AC power line (power terminal), it senses and operates the charging current to drive the AC high voltage indicator flashing. An AC high voltage alarm circuit for simultaneously turning on the polarity indicator if higher than this;
An alarm circuit alarm generation current setting resistor which is provided at a connection portion of the safety jumper A and sets a magnitude of a resistance so that a minimum current required for the AC high voltage alarm circuit flows;
A safety jumper comprising a polarity display circuit for classifying the polarity indicators according to the polarity of the terminals with which the tip of the safety jumper B is in contact. 5. The method of claim 4,
The extension line A has a polarity display circuit for distinguishing and lighting the polarity indicators according to the polarity of the terminal with which the tip of the extension line A is in contact. It is interlocked with power supply and interlock circuit of A,
The extension line B is a safety jumper, characterized in that the built-in polarity display circuit for distinguishing and lighting the polarity indicator according to the polarity of the terminal contacted by the tip of the extension line B.

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