阅读说明：本技术 一种避雷器智能检测模块及适配的避雷器氧化锌结构 (Arrester zinc oxide structure of arrester intellectual detection system module and adaptation ) 是由 李泉龙 李云龙 王健 谷甜甜 张再益 樊玉泊 于 2020-12-24 设计创作，主要内容包括：本发明基于一种避雷器智能检测模块及其适配的避雷器氧化锌组件,避雷器包括绝缘壳体,设置在绝缘壳体内的由若干个氧化锌片组成的避雷器氧化锌组件,所述避雷器氧化锌组件承接高压电线的端部为顶部,跟金属横担接触的端部为底部,其特征在于：所述智能检测模块包括电流互感器,对电流互感器中检测到的信号进行采集的信号采集单元,数据处理单元以及中央控制处理单元,所述避雷器氧化锌组件中最靠近底部的一个氧化锌片与上一个氧化锌片之间引出一根导线,并且该导线穿过电流互感器后接到接地壳体上,当避雷器受到雷击时,中央控制处理单元进行相应雷击次数的记录,当避雷器未受到雷击时,进行泄漏电流的监测与记录。(The invention relates to an intelligent detection module of a lightning arrester and a lightning arrester zinc oxide assembly adapted to the intelligent detection module, wherein the lightning arrester comprises an insulating shell and the lightning arrester zinc oxide assembly which is arranged in the insulating shell and consists of a plurality of zinc oxide sheets, the end part of the lightning arrester zinc oxide assembly, which is used for bearing a high-voltage wire, is the top, and the end part, which is contacted with a metal cross arm, is the bottom, and the intelligent detection module is characterized in that: the intelligent detection module comprises a current transformer, a signal acquisition unit, a data processing unit and a central control processing unit, wherein the signal acquisition unit acquires signals detected in the current transformer, a wire is led out between a zinc oxide sheet closest to the bottom and a last zinc oxide sheet in a zinc oxide component of the lightning arrester, the wire penetrates through the current transformer and then is connected to the grounding shell, when the lightning arrester is struck by lightning, the central control processing unit records the number of times of corresponding lightning, and when the lightning arrester is not struck by lightning, the monitoring and the recording of leakage current are carried out.)

1. The utility model provides an arrester zinc oxide subassembly of arrester intellectual detection system module and adaptation, the arrester includes insulating housing, and the ground connection casing sets up the arrester zinc oxide subassembly of constituteing by a plurality of zinc oxide piece in insulating housing, the tip that high tension line was accepted to arrester zinc oxide subassembly is the top, is bottom, its characterized in that with the tip of metal cross arm contact: the intelligent detection module comprises a current transformer, a signal acquisition unit for acquiring signals detected in the current transformer, a data processing unit and a central control processing unit, wherein a lead is led out between a zinc oxide sheet closest to the bottom and a previous zinc oxide sheet in a zinc oxide assembly of the lightning arrester and is connected to the grounding shell after passing through the current transformer, the lead and the zinc oxide sheet closest to the bottom form a parallel connection line, when the lightning arrester is struck by lightning, the zinc oxide assembly is instantly conducted and flows to the shell to be grounded, at the moment, the lead is shunted to a smaller current, the current transformer senses current signals on the lead, the current signals pass through the signal acquisition unit and the data processing unit, the result is transmitted to the central control processing unit for recording the corresponding lightning stroke times, and when the lightning arrester is not struck by lightning, the zinc oxide is in a completely insulated state, when leakage current occurs, the current flows from the top to the bottom of the zinc oxide, and the current transformer senses current signals on the wires and transmits the current signals to the central control processing unit to monitor and record the leakage current after the current signals pass through the signal acquisition unit and the data processing unit.

2. The intelligent lightning arrester detection module and the adapted zinc oxide arrester component, according to claim 1, is characterized in that: the utility model discloses a lightning arrester intelligent detection module, including being used for judging whether take place the first current transformer of thunderbolt and be used for detecting leakage current's second current transformer, lightning arrester intelligent detection module still judges processing circuit and leakage current detection circuitry including the thunderbolt, the thunderbolt is judged processing circuit and is included first current transformer, sampling resistor, RC filter circuit and high accuracy comparator, and when taking place the thunderbolt, the electric current that first current transformer sensed is through sampling resistor, and at the RC filter circuit that passes through, filters PCB own circuit clutter, and the processing through high accuracy comparator is compared the voltage value of gathering with the voltage value of settlement, and the central control processing unit in central control processing unit and the dormancy awakens up is sent to the corresponding level of output, and central control processing unit judges for the thunderbolt and take notes thunderbolt action number of times.

3. The intelligent lightning arrester detection module and the adapted zinc oxide arrester component, according to claim 2, is characterized in that: the leakage current detection circuit comprises a second current transformer, a sampling resistor, an RC filter circuit and a high-precision sampling chip, the second current transformer senses leakage current on the zinc oxide component, the leakage current passes through the RC filter circuit and the sampling resistor to form voltage input to the high-precision sampling chip, the acquired voltage value is stored in a register of the second current transformer through the high-precision sampling chip, and when the central control processing unit inquires, the current value acquired by the high-precision sampling chip is sent to the central control processing unit.

4. The intelligent lightning arrester detection module and the adapted zinc oxide arrester component, according to claim 3, is characterized in that: the lightning arrester intelligent detection module still includes zinc oxide temperature detect unit, zinc oxide temperature detect unit includes the platinum resistance, on measuring circuit and the signal processing circuit, the platinum resistance is pasted in a zinc oxide piece surface that is closest to the bottom, and platinum resistance both ends pin connects to on the measuring circuit, will transmit the level information through platinum resistance both sides to the signal processing circuit on through the measuring circuit, carries out the conversion of analog quantity and transmits to central control processing unit with the level information on the signal processing circuit.

5. The intelligent lightning arrester detection module and the adapted zinc oxide lightning arrester assembly thereof according to claim 1 or 4, wherein: the lightning arrester intelligent detection module supplies power the central control processing unit still includes residual capacity measurement system and power supply system, the central control processing unit specifically is master control chip, power supply system includes 3.7 volt lithium cell, residual capacity measurement system is including setting up the signal acquisition pin on master control chip, the lithium cell steps down to reference voltage 2.5V through TL431A, reference voltage loads on master control chip ADC1_ IN1 pin, be used for AD collection, AD gathers reference voltage and corresponds a code rate value, gather a code rate value that instantaneous voltage corresponds again, according to resolution ratio and reference voltage, back-derive instantaneous voltage, compare with full electric voltage again, thereby obtain residual capacity, the lithium cell steps up 3.7V's power supply through the chip that steps up and stabilizes to 5V, and supply power to high accuracy collection chip BL 6526B.

6. The intelligent lightning arrester detection module and the adapted zinc oxide arrester component, according to claim 5, is characterized in that: the main control chip and the server background are correspondingly communicated through a narrow-band Internet of things technology (NBIoT wireless communication technology).

7. The arrester zinc oxide component adapted to the arrester intelligent detection module of claim 1, wherein: a metal sheet which is in good physical contact with the position is arranged between the zinc oxide sheet closest to the bottom of the lightning arrester zinc oxide component and the last zinc oxide sheet, a lead is led out from the edge side of the metal sheet, penetrates through the current transformer and is connected to the grounding shell, and the lead and the zinc oxide sheet closest to the bottom form a parallel connection method.

Technical Field

The invention relates to a lightning arrester manufacturing technology, in particular to an intelligent lightning arrester which can simultaneously detect leakage current of a zinc oxide lightning arrester, lightning stroke times of the zinc oxide lightning arrester, temperature of zinc oxide and insulativity of power supply electric quantity.

Background

There are two types of arrester monitoring products on the market: the first type of arrester insulation monitoring product principle is that leakage current and resistive current of adopting the fundamental wave method to measure the zinc oxide arrester judge the insulating nature of arrester, power supply adopts outside DC24V, communication mode adopts RS485 to be connected to accuse ware in the communication, accuse ware rethread ethernet in the communication reaches the cloud platform, the cloud platform carries out the insulating nature analysis of arrester again, this type of product has mechanical type pointer display zinc oxide arrester leakage current size, but local naked eye watches. The measurement principle adopted by the second type of arrester insulation monitoring product is the same as that of the first type, the lightning arrester insulation monitoring product is purely mechanical, external DC24V power supply is needed, leakage current data can be read only by naked eyes, and manual regular inspection and data copying are needed. The first type of arrester insulation monitoring product is large in size and high in cost, and the arrester monitoring product is directly connected in series to a ground wire according to the measuring principle, so that the lightning arrester monitoring product is easily damaged due to great potential safety hazards in lightning stroke. The device is inconvenient to install, can only be installed on a telegraph pole with a ground wire to monitor the insulativity of a small part of zinc oxide arresters, cannot comprehensively measure the insulativity of each arrester, and can only be installed on a power supply station and the like due to the problems of power supply and data transmission. The second type of arrester insulation monitoring product has the same defects of the first type of arrester monitoring product, can not upload data remotely, and needs manual time and fixed point data copying. The product only measures the leakage current of the zinc oxide lightning arrester, does not measure lightning stroke and record the number of times of lightning stroke, does not measure the temperature of the zinc oxide, and cannot measure the number of times of lightning stroke and the leakage current only by using one device.

Disclosure of Invention

In order to solve the technical problem, the lightning arrester comprises an insulating shell, a grounding shell and a lightning arrester zinc oxide assembly which is arranged in the insulating shell and consists of a plurality of zinc oxide sheets, wherein the end part of the lightning arrester zinc oxide assembly for bearing a high-voltage wire is the top, the end part of the lightning arrester zinc oxide assembly which is contacted with a metal cross arm is the bottom, the intelligent detection module comprises a current transformer, a signal acquisition unit for acquiring signals detected in the current transformer, a data processing unit and a central control processing unit, a lead is led out between one zinc oxide sheet which is closest to the bottom and the last zinc oxide sheet in the lightning arrester zinc assembly, the lead passes through the current transformer and then is connected to the grounding shell, the lead and the zinc oxide sheet which is closest to the bottom form a parallel connection method, when the lightning arrester is struck, the zinc oxide assembly is instantly conducted, when current reaches the last zinc oxide sheet at the bottom, most of current flows to the shell body through the last zinc oxide runoff and is grounded, the parallel connection wire shunts less current, the current transformer senses the current signal on the wire and passes through the signal acquisition unit and the data processing unit, and signal transmission is carried out to the central control processing unit, the central control unit carries out lightning stroke judgment and the record of lightning stroke frequency, when the lightning arrester is not struck by lightning, the zinc oxide is in an insulation state, when leakage current occurs, the current flows from the top of the zinc oxide to the last zinc oxide at the bottom, the last zinc oxide is in an insulation state, the leakage current can only flow into the grounded shell from the parallel connection wire, the current transformer senses the current signal on the wire and passes through the signal acquisition unit and the data processing unit, and the monitoring and the record of the leakage current are carried out for the central control processing unit.

After having adopted above-mentioned structure, because the main functional unit of arrester lies in the zinc oxide part, the key feature of zinc oxide lies in when not being in the thunderbolt condition, and the zinc oxide subassembly is insulating state, even connect under the high-voltage line, can not lead to the fact any influence to the normal switch-on of high-voltage line yet, when being struck by lightning, the zinc oxide subassembly can switch on in the twinkling of an eye to switch on ground to strike by lightning high pressure. The structure of the zinc oxide component is composed of a plurality of zinc oxides, lightning strike voltage is respectively punctured from top to bottom, and the closer to the bottom, the larger the resistance value of the zinc oxide component is. Therefore, a wire is skillfully connected in parallel with the zinc oxide at the bottom, under the condition of no lightning stroke, the zinc oxide cannot be broken down due to the characteristics of the zinc oxide, the high voltage of 10kV, 35kV or other grades of power transmission and transformation, the resistance of the zinc oxide is infinite, the leakage current is 0mA, when the insulativity of the zinc oxide is reduced, the resistance value of the zinc oxide is reduced, the high voltage loaded at the top end of the zinc oxide arrester has weak leakage current relatively, the leakage current flows to the zinc oxide at the bottom end, the leakage current flows into the ground along the direction of the parallel wire, the current transformer used at the moment can sense the leakage current on the parallel wire, under the condition of the lightning stroke, the lightning stroke voltage exceeds the cut-off threshold value of the zinc oxide due to the characteristics of the zinc oxide, the zinc oxide is broken down, and the resistance of the zinc oxide is changed from infinite to be close to 0, the zinc oxide becomes similar wire, when the lightning stroke current runoff reaches the bottom of zinc oxide, the bottom all is the wire this moment, and the lightning stroke current shunts, and the most current runoff zinc oxide reaches the ground, and the current runoff of several amperes connects the wire in parallel, and at this moment, through central control processing unit and corresponding conversion algorithm, can distinguish the lightning stroke and record the number of times of lightning stroke and measure the leakage current of zinc oxide arrester.

As a further improvement of the invention, the current transformer comprises a first current transformer for judging whether the lightning strike occurs or not and a second current transformer for detecting leakage current, the intelligent lightning arrester detection module also comprises a lightning stroke judgment processing circuit and a leakage current detection circuit, the lightning stroke judging and processing circuit comprises a first current transformer, a sampling resistor, an RC filter circuit and a high-precision comparator, when a lightning stroke occurs, the current sensed by the first current transformer passes through the sampling resistor, the circuit noise of the PCB is filtered through the RC filter circuit, the high-precision comparator compares the collected voltage value with the set voltage value through a series of processing, corresponding levels are output and sent to the central control processing unit, the central control processing unit in dormancy is awakened, and the central control processing unit judges the lightning stroke and records the lightning stroke action times. The leakage current detection circuit comprises a second current transformer, a sampling resistor, an RC filter circuit and a high-precision sampling chip, the second current transformer senses leakage current on the zinc oxide component, the leakage current passes through the RC filter circuit and the sampling resistor to form voltage input to the high-precision sampling chip, the acquired current value is stored in a register of the second current transformer through the high-precision sampling chip, and when the central control processing unit inquires, the acquired current value is sent to the central control processing unit through the high-precision sampling chip.

After having adopted above-mentioned structure, through setting up the different current sensor of two precisions, come to take notes leakage current and thunderbolt number of times respectively, the high accuracy comparator produces the low level with nanosecond level time, and central control processing unit in the reuse program control dormancy can the very big degree reduce the consumption of arrester intellectual detection system module to the response time is very short, can be accurate note thunderbolt number of times. The high-precision sampling chip stores the acquired current value into a register of the high-precision sampling chip through signal processing, data acquisition and software algorithm. When the main control chip inquires, the high-precision sampling chip sends the acquired current value to the central control processing unit through the SPI/UART port. And the central control processing unit obtains the current value of the high-precision sampling chip.

As a further improvement of the present invention, the intelligent lightning arrester detection module further includes a zinc oxide temperature detection unit, the zinc oxide temperature detection unit includes a platinum resistor, a measurement circuit and a signal processing circuit, the platinum resistor is attached to an outer surface of a zinc oxide sheet closest to the bottom, pins at two ends of the platinum resistor are connected to the measurement circuit, level information passing through two sides of the platinum resistor is transmitted to the signal processing circuit through the measurement circuit, and the signal processing circuit converts the level information into analog quantity and transmits the analog quantity to the central control processing unit.

After the structure is adopted, the temperature of the zinc oxide sheet can be well measured by utilizing the characteristic of the platinum resistor.

The central control processing unit for supplying power to the intelligent lightning arrester detection module is further improved by the invention and also comprises a residual electric quantity measuring system and a power supply system, the central control processing unit is a main control chip, the power supply system comprises a 3.7-volt lithium battery, the residual capacity measuring system comprises a signal acquisition pin arranged on a main control chip, a lithium battery is subjected to voltage reduction to reference voltage of 2.5V through TL431A, the reference voltage is loaded on an ADC1_ IN1 pin of the main control chip, is used for AD acquisition, the AD acquisition reference voltage corresponds to a code rate value, the acquisition instantaneous voltage corresponds to a code rate value, according to the resolution and the reference voltage, the instantaneous voltage is reversely deduced, and then the instantaneous voltage is compared with the full-power voltage, so that the residual power is obtained, the lithium battery boosts the 3.7V power supply to be stabilized to 5V through the boost chip, and the high-precision acquisition chip BL6526B is powered. The main control chip and the server background are communicated correspondingly through the NBIoT wireless communication technology.

After the structure is adopted, the residual electric quantity of the battery electric quantity can be accurately calculated by adopting the algorithm. Due to the fact that the low-power NBIoT wireless communication technology is adopted, the main control chip enters the standby mode, low power consumption, low cost and small size are achieved, and collected data can be directly uploaded to the cloud platform. The lithium battery is directly powered without an intermediate communication device or an external power supply, so that the product volume is reduced, the installation is convenient, and the data generation is convenient.

As a further improvement of the invention, a metal sheet which is in good physical contact with the position is arranged between the zinc oxide sheet closest to the bottom of the zinc oxide component of the lightning arrester and the last zinc oxide sheet, a lead is led out from the edge side of the metal sheet, passes through the current transformer and is connected to the grounding shell, and the lead and the zinc oxide sheet closest to the bottom form a parallel connection line.

Drawings

Fig. 1 is a sectional assembled view of a lightning arrester;

FIG. 2 is a schematic diagram illustrating the measurement principles and methods of the present invention;

FIG. 3 is a circuit diagram showing the detection of lightning stroke times of the zinc oxide arrester of the intelligent detection module according to the invention;

fig. 4 is a circuit diagram of the leakage current detection circuit of the zinc oxide arrester of the intelligent detection module.

Detailed Description

Insulating housing 1, arrester zinc oxide subassembly 2, top 21, bottom 22, intellectual detection system module 3, sheetmetal 4, current transformer 5.

As shown in fig. 1-4, the lightning arrester includes an insulating housing 1, a grounding housing, a lightning arrester zinc oxide assembly 2 composed of a plurality of zinc oxide sheets and disposed in the insulating housing 1, the end of the lightning arrester zinc oxide assembly 2 receiving the high voltage electric wire is a top 21, the end contacting with the metal cross arm is a bottom 22, the intelligent detection module 3 includes a current transformer 5, a signal acquisition unit for acquiring the signal detected in the current transformer 5, a data processing unit and a central control processing unit, a lead is led out between the zinc oxide sheet closest to the bottom and the last zinc oxide sheet in the lightning arrester zinc oxide assembly, and the lead passes through the current transformer and then is connected to the grounding housing, the lead forms a parallel connection with the zinc oxide sheet closest to the bottom, when the lightning arrester is struck, the zinc oxide assembly is instantly conducted, and runoff to shell body ground connection, at this moment, the wire shunts less electric current, current transformer senses the current signal on the wire and behind signal acquisition unit and data processing unit, and transmit the result and carry out the record of corresponding thunderbolt number of times for central control processing unit, when the arrester is not struck by lightning, zinc oxide is complete insulating state, when leakage current appears, the top runoff to the bottom of zinc oxide is followed to the electric current, current transformer senses the current signal on the wire and behind signal acquisition unit and data processing unit, thereby transmit central control processing unit and carry out leakage current's monitoring and record. Because the main functional unit of arrester lies in the zinc oxide part, zinc oxide's key feature lies in when not under the thunderbolt condition, and the zinc oxide subassembly is insulating state, even connect under the high-voltage line, can not lead to the fact any influence to the normal conduction of high-voltage line yet, when being struck by lightning, the zinc oxide subassembly can switch on in the twinkling of an eye to switch on ground to the high pressure of being struck by lightning. The structure of the zinc oxide component is composed of a plurality of zinc oxides, lightning strike voltage is respectively punctured from top to bottom, and the closer to the bottom, the larger the resistance value of the zinc oxide component is. Therefore, after the current sensor is connected in parallel, under the condition of no lightning stroke, the zinc oxide cannot be broken down by the transmission and transformation high voltage of 10kV or 35kV due to the characteristics of the zinc oxide, the resistance of the zinc oxide is infinite, the leakage current is 0mA, when the insulativity of the zinc oxide is reduced, the resistance value of the zinc oxide is reduced, the high voltage loaded on the top end of the zinc oxide arrester has weak leakage current relatively, when the leakage current flows to the zinc oxide at the bottom end, the leakage current flows into the ground along the direction of the parallel conductor, the current transformer used at the moment can sense the leakage current on the parallel conductor, under the condition of the lightning stroke, due to the characteristics of the zinc oxide, the lightning stroke voltage exceeds the cut-off threshold value of the zinc oxide to break down the zinc oxide, at the moment, the resistance of the zinc oxide is changed from infinite to be close to 0 ohm, the zinc oxide is changed into a similar conductor, at the moment, the bottom ends are all leads, lightning current is shunted, most of current runoff zinc oxide flows to the ground, the current runoff of a few amperes is connected with the leads in parallel, and at the moment, through the central control processing unit and a corresponding conversion algorithm, the leakage current or the runoff current passing through during lightning stroke can be calculated.

The lightning arrester intelligent detection module comprises a lightning arrester intelligent detection module, a lightning arrester intelligent detection module and a central control processing unit, wherein the lightning arrester intelligent detection module comprises a first current transformer used for judging whether lightning strikes and a second current transformer used for detecting leakage current, the lightning arrester intelligent detection module further comprises a lightning strike judgment processing circuit and a leakage current detection circuit, the lightning strike judgment processing circuit comprises the first current transformer, a sampling resistor, an RC filter circuit and a high-precision comparator, when lightning strikes occur, current sensed by the first current transformer passes through the sampling resistor, the current passes through the RC filter circuit, circuit noise waves of a PCB are filtered, the high-precision comparator carries out a series of processing to compare the acquired voltage value with a set voltage value, the corresponding level is output to the central control processing unit, the central control processing unit wakes up the dormant central control processing unit, and the central control processing unit judges the lightning strikes and records the. The leakage current detection circuit comprises a second current transformer, a sampling resistor, an RC filter circuit and a high-precision sampling chip, the second current transformer senses leakage current on the zinc oxide component, the leakage current passes through the RC filter circuit and the sampling resistor to form voltage input to the high-precision sampling chip, the acquired current value is stored in a register of the second current transformer through the high-precision sampling chip, and when the central control processing unit inquires, the acquired current value is sent to the central control processing unit through the high-precision sampling chip. Through setting up the different current sensor of two precisions, come record leakage current and thunderbolt number of times respectively, the high accuracy comparator produces the low level with nanosecond level time, and central control processing unit in the reuse program control dormancy, the reduction arrester intellectual detection system module's that can the very big degree consumption to response time is extremely short, can be accurate note the thunderbolt number of times. The high-precision sampling chip stores the acquired current value into a register of the high-precision sampling chip through signal processing, data acquisition and software algorithm. When the main control chip inquires, the high-precision sampling chip sends the acquired current value to the central control processing unit through the SPI/UART port.

The lightning arrester intelligent detection module still includes zinc oxide temperature detect unit, zinc oxide temperature detect unit includes the platinum resistance, on measuring circuit and the signal processing circuit, the platinum resistance is pasted in a zinc oxide piece surface that is closest to the bottom, and platinum resistance both ends pin connects to on the measuring circuit, will transmit the level information through platinum resistance both sides to the signal processing circuit on through the measuring circuit, carries out the conversion of analog quantity and transmits to central control processing unit with the level information on the signal processing circuit. By utilizing the characteristic of platinum resistance, the temperature of the zinc oxide sheet can be well measured.

The lightning arrester intelligent detection module supplies power the central control processing unit still includes residual capacity measurement system and power supply system, the central control processing unit specifically is master control chip, power supply system includes 3.7 volt lithium cell, residual capacity measurement system is including setting up the signal acquisition pin on master control chip, the lithium cell steps down to reference voltage 2.5V through TL431A, reference voltage loads on master control chip ADC1_ IN1 pin, be used for AD collection, AD gathers reference voltage and corresponds a code rate value, gather a code rate value that instantaneous voltage corresponds again, according to resolution ratio and reference voltage, back-derive instantaneous voltage, compare with full electric voltage again, thereby obtain residual capacity, the lithium cell steps up 3.7V's power supply through the chip that steps up and stabilizes to 5V, and supply power to high accuracy collection chip BL 6526B. The main control chip and the server background are communicated correspondingly through the NBIoT wireless communication technology. The residual capacity of the battery capacity can be accurately calculated by adopting the algorithm. Due to the fact that the low-power NBIoT wireless communication technology is adopted, the main control chip enters the standby mode, low power consumption, low cost and small size are achieved, and collected data can be directly uploaded to the cloud platform. The lithium battery is directly powered without an intermediate communication device or an external power supply, so that the product volume is reduced, the installation is convenient, and the data generation is convenient.

A metal sheet 4 which is in good physical contact with the position is arranged between the zinc oxide sheet closest to the bottom of the lightning arrester zinc oxide component and the last zinc oxide sheet, a lead is led out of the edge of the metal sheet 4, penetrates through the current transformer and is connected to the grounding shell, and the lead and the zinc oxide sheet closest to the bottom form a parallel connection line.