A Portable Relay Protection Tester and a Multiplexing and Demultiplexing Communication System

Abstract

A portable relay protection tester and a multiplexing and demultiplexing communication system belong to the technical field of electrical relay protection interfaces. The problem to be solved is how to design a portable relay protection tester with interface multiplexing, so as to effectively reduce the number of physical interfaces, reduce the volume of the tester, and improve the portability of the tester. The portable relay protection tester designed by the technical solution of the present invention places RS485 and Ethernet signals on the RJ45 interface uniformly, effectively reducing the number of physical interfaces to reduce the volume of the tester and improve the portability of the tester; the signal multiplexing and demultiplexing method adopted by the multiplexing and demultiplexing signal communication system ensures that Ethernet communication and RS485 communication do not interfere with each other and work properly at the same time; it solves the problem that in the prior art, increasing the number of interfaces of the relay protection tester leads to an overly large volume of the relay protection tester, resulting in inconvenient use.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrical relay protection interfaces, and particularly relates to a portable relay protection tester and a multiplexing and demultiplexing communication system. Background Art

[0002] Relay protection tests in power systems generally have multiple interfaces, such as analog voltage and current interfaces, input / output interfaces, optical Ethernet interfaces, electrical Ethernet interfaces, RS485, and RS232 interfaces. These numerous interfaces make the tester too bulky and not conducive to on-site portable use. Therefore, some relay protection tests can only reduce the interfaces or increase the volume of the tester. Reducing the interfaces limits the versatility of the tester, while increasing the volume reduces the portability of the tester.

[0003] In the prior art, the patent application for invention "A Portable Digital Relay Protection Tester" with the publication number CN105425077A and the publication date of March 23, 2016, discloses a portable digital relay protection tester, which includes a central processing unit, a timing unit, an optical input / output unit, and a battery charging unit; the timing unit and the optical input / output unit are respectively connected to the central processing unit; the timing unit, the optical input / output unit, and the central processing unit are all connected to the battery charging unit; the central processing unit is also connected to an Ethernet and a Wifi module; the timing unit is used to correct the absolute time of the test instrument; the optical input / output unit is used to convert the analog signals to be tested into digital signals.

[0004] The above technical solution is provided with a wireless interface and an internal power supply, making it more convenient to use; it can achieve waveform recording analysis and can test the time characteristics of the process layer. However, the above technical solution does not solve the problem that the increase in the number of interfaces of the relay protection tester leads to an overly large volume of the relay protection tester and thus inconvenient use. Summary of the Invention

[0005] The purpose of the present invention is to design a portable relay protection tester with interface multiplexing, thereby effectively reducing the number of physical interfaces, reducing the volume of the tester, and improving the portability of the tester.

[0006] The present invention solves the above technical problems through the following technical solutions:

[0007] A portable relay protection tester includes a CPU module, an Ethernet PHY chip, an Ethernet transformer, an RS485 transceiver, and an RJ45 socket. The input end of the Ethernet PHY chip is connected to the CPU module, the output end of the Ethernet PHY chip is connected to the primary side of the Ethernet transformer, and the secondary side of the Ethernet transformer is connected to the RJ45 socket. The first differential receiving end A, the second differential receiving end B, the first differential sending end Y, and the second differential sending end Z of the RS485 transceiver are respectively connected to the secondary side of the Ethernet transformer, and the receiving channel TTL signal end RO, the sending control end RE, and the transmitting channel TTL signal end DI of the RS485 transceiver are respectively connected to the CPU module.

[0008] As a further improvement of the technical solution of the present invention, the sending control end RE is used to control the output signal. When the RS485 transceiver needs to output, the sending control end RE is controlled by the CPU module to be low. When the RS485 transceiver needs to receive, the sending control end RE is controlled by the CPU module to be high. When the RS485 transceiver outputs, the DI signal sent by the CPU module is input from the transmitting channel TTL signal end DI and then converted into a differential signal, which is output through the first differential sending channel formed by the first differential sending end Y and the second differential sending end Z. When the DI signal is at a high level, the first differential sending end Y is at a logical high and the second differential sending end Z is at a logical low to form a differential output mode. When the DI signal is at a logical low, the first differential sending end Y is at a logical low and the second differential sending end Z is at a logical high to form a differential output mode. When the first differential receiving end A is at a logical low and the second differential receiving end B is at a logical high, the receiving channel TTL signal end RO outputs a low-level RO signal to the CPU module. When the first differential receiving end A is at a logical high and the second differential receiving end B is at a logical low, the receiving channel TTL signal end RO outputs a high-level RO signal to the CPU module.

[0009] As a further improvement of the technical solution of the present invention, the Ethernet transformer includes a first sub-transformer and a second sub-transformer. The primary winding of the first sub-transformer is connected to the MII_TX interface of the CPU module through the Ethernet PHY chip. The primary winding of the second sub-transformer is connected to the MII_RX interface of the CPU module through the Ethernet PHY chip.

[0010] As a further improvement of the technical solution of the present invention, the primary winding of the first sub-transformer includes a first primary wire head TRD0+, a second primary wire head TRD0-, and a first primary intermediate tap COM0; the primary winding of the second sub-transformer includes a third primary wire head TRD1+, a fourth primary wire head TRD1-, and a second primary intermediate tap COM1; the first primary wire head TRD0+, the second primary wire head TRD0-, and the first primary intermediate tap COM0 are respectively connected to the Ethernet PHY chip; the third primary wire head TRD1+, the fourth primary wire head TRD1-, and the second primary intermediate tap COM1 are respectively connected to the Ethernet PHY chip.

[0011] As a further improvement of the technical solution of the present invention, it further includes a resistor R1, a resistor R2, and a capacitor C1. The secondary winding of the first sub-transformer includes a first secondary wire head TP0+, a second secondary wire head TP0-, and a first secondary intermediate tap TC0; the secondary winding of the second sub-transformer includes a third secondary wire head TP1+, a fourth secondary wire head TP1-, and a second secondary intermediate tap TC1; the first secondary intermediate tap TC0 is respectively connected to the second differential receiving end B, the second differential sending end Z, and one end of the resistor R1, and the second secondary intermediate tap TC1 is respectively connected to the first differential receiving end A, the first differential sending end Y, and one end of the resistor R2. The other ends of the resistor R1 and the resistor R2 are connected and then connected to electrical ground through the capacitor C1.

[0012] As a further improvement of the technical solution of the present invention, the first secondary wire head TP0+, the second secondary wire head TP0-, the third secondary wire head TP1+, and the fourth secondary wire head TP1- are respectively connected to the PIN1-TP0+ pin, PIN2-TP0- pin, PIN3-TP1+ pin, and PIN6-TP1- pin of the RJ45 socket, and are electrically connected to the PIN5-TP2- pin of the RJ45 socket, and the PIN4-TP2+ pin of the RJ45 socket is left unconnected.

[0013] As a further improvement of the technical solution of the present invention, it further includes an RS232 transceiver. The TTL signal end TTL_OUT of the RS232 sending channel and the TTL signal end TTL_IN of the RS232 receiving channel of the RS232 transceiver are respectively connected to the CPU module; the serial signal end RS232_OUT of the sending channel and the serial signal end RS232_IN of the receiving channel of the RS232 transceiver are respectively connected to the PIN7-TP3+ pin and PIN8-TP3- pin of the RJ45 socket.

[0014] A multiplexing and demultiplexing communication system includes two portable relay protection testers as described in any one of claims 1-7 and an Ethernet cable. The two portable relay protection testers are a first portable relay protection tester and a second portable relay protection tester respectively, and the first portable relay protection tester and the second portable relay protection tester are connected by the Ethernet cable.

[0015] As a further improvement of the technical solution of the present invention, the Ethernet cable includes a first cable, a second cable, a third cable, a fourth cable, a fifth cable, a sixth cable, a seventh cable, and an eighth cable. Among them, the first cable and the second cable form a first twisted pair, the third cable and the sixth cable form a second twisted pair, the fourth cable and the fifth cable form a third twisted pair, and the seventh cable and the eighth cable form a fourth twisted pair.

[0016] As a further improvement of the technical solution of the present invention, the first pin PIN1-TP0+ of the RJ45 socket of the first portable relay protection tester is connected to the first pin PIN1-TP0+ of the RJ45 socket of the second portable relay protection tester through the first cable; the second pin PIN2-TP0- of the RJ45 socket of the first portable relay protection tester is connected to the second pin PIN2-TP0- of the RJ45 socket of the second portable relay protection tester through the second cable; the third pin PIN3-TP1+ of the RJ45 socket of the first portable relay protection tester is connected to the third pin PIN3-TP1+ of the RJ45 socket of the second portable relay protection tester through the third cable; the fourth pin PIN4-TP2+ of the RJ45 socket of the first portable relay protection tester is connected to the fourth pin PIN4-TP2+ of the RJ45 socket of the second portable relay protection tester through the fourth cable; the fifth pin PIN5-TP2- of the RJ45 socket of the first portable relay protection tester is connected to the fifth pin PIN5-TP2- of the RJ45 socket of the second portable relay protection tester through the fifth cable; the sixth pin PIN6-TP1- of the RJ45 socket of the first portable relay protection tester is connected to the sixth pin PIN6-TP1- of the RJ45 socket of the second portable relay protection tester through the sixth cable; the seventh pin PIN7-TP3+ of the RJ45 socket of the first portable relay protection tester is connected to the eighth pin PIN8-TP3- of the RJ45 socket of the second portable relay protection tester through the seventh cable; the eighth pin PIN8-TP3- of the RJ45 socket of the first portable relay protection tester is connected to the seventh pin PIN7-TP3+ of the RJ45 socket of the second portable relay protection tester through the eighth cable.

[0017] As a further improvement of the technical solution of the present invention, when an Ethernet connection is adopted between the first secondary wire heads TP0+ and TP0- of the first portable relay protection tester and the first secondary wire heads TP0+ and TP0- of the second portable relay protection tester, the multiplexing and demultiplexing methods are as follows:

[0018] Step 1, the CPU module of the first portable relay protection tester sends Ethernet data to the Ethernet PHY chip. The Ethernet PHY chip converts the Ethernet data into a first Ethernet differential voltage signal Vtr0_a and transmits it to the first primary wire head TRD0+ and the second primary wire head TRD0- of the first sub-transformer. The first Ethernet differential voltage signal Vtr0_a is converted into a first Ethernet differential transmission signal by the first sub-transformer in a 1:1 amplitude manner and output through the first secondary wire head TP0+ and the second secondary wire head TP0- of the first sub-transformer. Define the voltage value of the first secondary wire head TP0+ minus the second secondary wire head TP0- as Vtp0_a;

[0019] Step 2, the first secondary wire head TP0+ and the second secondary wire head TP0- of the first portable relay protection tester are equivalent to a voltage source Ve1_a and a voltage source Ve2_a. The voltage of the voltage source Ve1_a is the voltage of the first secondary wire head TP0+ minus the voltage of the first secondary center tap TC0; the voltage of the voltage source Ve2_a is the voltage of the first secondary center tap TC0 minus the voltage of the second secondary wire head TP0-. Due to the winding characteristics of the Ethernet transformer, the amplitudes of Ve1_a and Ve2_a are equal and the polarities are the same; the voltage Vtp0_a between the first secondary wire head TP0+ and the second secondary wire head TP0- is expressed as:

[0020] Vtp0_a = Ve1_a + Ve2_a (1)

[0021] Step 3, the first differential sending end Y and the second differential sending end Z of the RS485 transceiver of the first portable relay protection tester are equivalent to a voltage source RS1 and a voltage source RS2, and the voltages of the voltage source RS1 and the voltage source RS2 are Vrs1_a and Vrs2_a respectively;

[0022] Step 4, the voltage Vrs1_a of the first differential sending end Y of the first portable relay protection tester is multiplexed to the first secondary center tap TC0. Then, the voltages Vtp0+_a of the first secondary wire head TP0+ and Vtp0-_a of the second secondary wire head TP0- of the relay protection test A are respectively:

[0023] Vtp0+_a = Ve1_a + Vrs1_a (2)

[0024] Vtp0-_a = Vrs1_a - Ve2_a (3)

[0025] Step 5: The first Ethernet differential transmission signal of the first portable relay protection tester is transmitted to the first secondary wire head TP0+ and the second secondary wire head TP0- of the second portable relay protection tester through the first secondary wire head TP0+ and the second secondary wire head TP0-. And the second differential transmitter Z of the second portable relay protection tester is also driven to the first secondary center tap TC0 on the side of the second portable relay protection tester. The RS485 receiving side is in a high-impedance state, and its voltage value is ignored;

[0026] Step 6: The voltage of the first secondary wire head TP0+ of the second portable relay protection tester is Vtp0+_b, and this voltage is equal to the voltage Vtp0+_a of the first secondary wire head TP0+ of the first portable relay protection tester; the voltage of the second secondary wire head TP0- of the second portable relay protection tester is Vtp0-_b, and this voltage is equal to the voltage Vtp0-_a of the second secondary wire head TP0- of the first portable relay protection tester, that is:

[0027] Vtp0+_b = Vtp0+_a (4)

[0028] Vtp0-_b = Vtp0-_a (5)

[0029] Step 7: The voltage Vtp0_b of the voltage obtained by subtracting the voltage Vtp0-_b of the second secondary wire head TP0- from the voltage Vtp0+_b of the first secondary wire head TP0+ of the second portable relay protection tester is:

[0030] Vtp0_b = Vtp0+_b - Vtp0-_b (6)

[0031] According to the above formulas (2), (3), (4), and (5), Vtp0_b is:

[0032] Vtp0_b = (Ve1_a + Vrs1_a) - (Vrs1_a - Ve2_a) = Ve1_a + Ve2_a = Vtp0_a (7).

[0033] As a further improvement of the technical solution of the present invention, when the first portable relay protection tester and the second portable relay protection tester are connected by an RS485 interface, the multiplexing and demultiplexing methods are as follows:

[0034] Step a, the CPU module of relay protection tester A generates RS485 data and sends it to the TTL signal terminal DI of the RS485 transmission channel, where it is converted into an RS485 differential transmission signal and transmitted to the first differential transmission terminal Y and the second differential transmission terminal Z. The first differential transmission terminal Y is equivalent to a voltage source RS1, and the second differential transmission terminal Z is equivalent to a voltage source RS2. The voltages of the voltage sources RS1 and RS2 are Vrs1 and Vrs2 respectively, and the differential output voltage is Vrs_a, and Vrs_a = Vrs1 - Vrs2; Vrs1 and Vrs are respectively output to the first secondary center tap TC0 and the second secondary center tap TC1 of relay protection tester A;

[0035] Step b, applying the voltage Vrs1 to the first secondary center tap TC0 of relay protection tester A, then the voltages Vtp0+_a of the first secondary wire head TP0+ and Vtp0-_a of the second secondary wire head TP0- are respectively:

[0036] Vtp0+_a = Ve1_a + Vrs1_a (8)

[0037] Vtp0-_a = Vrs1_a - Ve2_a (9)

[0038] Step c, the voltages Vtp0+_a of the first secondary wire head TP0+ and Vtp0-_a of the second secondary wire head TP0- of relay protection tester A are respectively transmitted to the first secondary wire head TP0+ and the second secondary wire head TP0- of relay protection tester B through the first twisted pair. The voltage Vtc0_b of the first secondary center tap TC0 of relay protection tester B is:

[0039] Vtc0_b = (Vtp0+_a + Vtp0-_a) / 2 = (Ve1_a + Vrs1_a + Vrs1_a - Ve2_a) / 2 (10)

[0040] Since the amplitudes of Ve1_a and Ve2_a are equal and the polarities are the same, the voltage Vtc0_b of the first secondary center tap TC0 of relay protection tester B is:

[0041] Vtc0_b = (Vrs1_a + Vrs1_a) / 2 = Vrs1_a (11)

[0042] Step d, similarly, the voltage of the second secondary center tap TC1 of relay protection tester B is Vtc1_b = Vrs2_a;

[0043] Step e, the receiving end voltage Vab_b of the RS485 transceiver of relay protection tester B is:

[0044] Vab_b = Vtc0_b - Vtc1_b = Vrs1_a - Vrs2_a = Vrs_a (12).

[0045] The advantages of the present invention are as follows:

[0046] In the portable relay protection tester designed according to the technical solution of the present invention, RS485, RS232, and Ethernet signals are uniformly placed on the RJ45 interface, effectively reducing the number of physical interfaces to reduce the volume of the tester and improve the portability of the tester; the signal multiplexing and demultiplexing method adopted by the multiplexing and demultiplexing signal communication system ensures that the three communication modes of Ethernet communication, RS485 communication, and RS232 communication do not interfere with each other and work properly at the same time; it solves the problem in the prior art that increasing the number of interfaces of the relay protection tester leads to an overly large volume of the relay protection tester, resulting in inconvenient use. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 is the hardware connection diagram of the portable relay protection tester of the present invention;

[0048] Figure 2 is the schematic structural diagram of the multiplexing and demultiplexing communication system of the present invention;

[0049] Figure 3 is the equivalent circuit of the relay protection tester using Ethernet connection before;

[0050] Figure 4 is the equivalent circuit of the relay protection tester using RS485 connection before;

[0051] Figure 5 is the equivalent circuit of the relay protection tester connected to other devices using RS485. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0052] For the convenience of those of ordinary skill in the art to understand and implement the present invention, the present invention will be further described in detail below in conjunction with embodiments. It should be understood that the embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0053] 1. The hardware connection structure of the portable relay protection tester of the present invention

[0054] As shown in Figure 1 , a portable relay protection tester includes a CPU module, an Ethernet PHY chip, an RS485 transceiver, an RS232 transceiver, an RJ45 socket, a resistor R1, a resistor R2, and a capacitor C1.

[0055] The CPU module described above is the starting end or the final end of the data source for Ethernet communication, RS485 communication, and RS232 communication. The CPU module is connected to the Ethernet PHY chip using the MII_TX / MII_RX interface, and the Ethernet PHY chip is connected to one side of the Ethernet transformer (TRD0+ / COM0 / TRD0-, TRD1+ / COM1 / TRD1-) through PCB traces.

[0056] The CPU module described above can be an ARM CPU, an X86 CPU, or other devices such as an FPGA. The RS485 interface can be used as a transceiver for time synchronization signals such as IRIG-B / PPS or other communication physical layers.

[0057] The Ethernet transformer includes two independent sub-transformers, namely the first sub-transformer and the second sub-transformer. Each sub-transformer includes a primary winding and a secondary winding. The side connected to the Ethernet PHY chip is the primary winding, and the other side is the secondary winding.

[0058] The primary winding of the first sub-transformer includes a first primary wire head TRD0+, a second primary wire head TRD0-, and a first primary center tap COM0; the primary winding of the second sub-transformer includes a third primary wire head TRD1+, a fourth primary wire head TRD1-, and a second primary center tap COM1; the secondary winding of the first sub-transformer includes a first secondary wire head TP0+, a second secondary wire head TP0-, and a first secondary center tap TC0; the secondary winding of the second sub-transformer includes a third secondary wire head TP1+, a fourth secondary wire head TP1-, and a second secondary center tap TC1.

[0059] The RS485 transceiver includes: a first differential receiving end A, a second differential receiving end B, an RS485 receiving channel TTL signal end RO, a transmit control end RE, an RS485 transmitting channel TTL signal end DI, a first differential transmitting end Y, and a second differential transmitting end Z.

[0060] The first original edge wire head TRD0+, the second original edge wire head TRD0-, and the first original edge middle tap COM0 are respectively connected to the Ethernet PHY chip. The third original edge wire head TRD1+, the fourth original edge wire head TRD1-, and the second original edge middle tap COM1 are respectively connected to the Ethernet PHY chip. The first secondary edge wire head TP0+ and the second secondary edge wire head TP0- are respectively connected to the first pin PIN1-TP0+ and the second pin PIN2-TP0-. The third secondary edge wire head TP1+ and the fourth secondary edge wire head TP1- are respectively connected to the third pin PIN3-TP1+ and the sixth pin PIN6-TP1-. The first secondary edge middle tap TC0 is respectively connected to the second differential receiving end B, the second differential sending end Z, and one end of the resistor R1. The second secondary edge middle tap TC1 is respectively connected to the first differential receiving end A, the first differential sending end Y, and one end of the resistor R2. The other ends of the resistor R1 and the resistor R2 are both connected to the electrical ground through the capacitor C1.

[0061] The RS485 receiving channel TTL signal terminal RO, the transmission control terminal RE, and the RS485 transmitting channel TTL signal terminal DI are respectively connected to the CPU module.

[0062] The RS232 transceiver includes: the RS232 transmitting channel TTL signal terminal TTL_OUT, the transmitting channel serial signal terminal RS232_OUT, the RS232 receiving channel TTL signal terminal TTL_IN, and the receiving channel serial signal terminal RS232_IN.

[0063] The RS232 transmitting channel TTL signal terminal TTL_OUT and the RS232 receiving channel TTL signal terminal TTL_IN are respectively connected to the CPU module. The transmitting channel serial signal terminal RS232_OUT and the receiving channel serial signal terminal RS232_IN are respectively connected to the seventh pin PIN7-TP3+ and the eighth pin PIN8-TP3-.

[0064] The RJ45 socket includes: the first pin PIN1-TP0+, the second pin PIN2-TP0-, the third pin PIN3-TP1+, the fourth pin PIN4-TP2+, the fifth pin PIN5-TP2-, the sixth pin PIN6-TP1-, the seventh pin PIN7-TP3+, and the eighth pin PIN8-TP3-. The fifth pin PIN5-TP2- is connected to the electrical ground. The fourth pin PIN4-TP2+ is left unconnected.

[0065] 2. Functions of each control port of the portable relay protection tester of the present invention

[0066] Such as Figure 1As shown in the figure, the transmission control terminal RE is used to control the output signal. When the RS485 transceiver needs to output, the transmission control terminal RE is controlled by the CPU module to be low. When the RS485 transceiver needs to receive, the transmission control terminal RE is controlled by the CPU module to be high. When the RS485 transceiver outputs, the DI signal sent by the CPU module is input from the transmitting channel TTL signal terminal DI and then converted into a differential signal, which is output through the first differential transmission channel composed of the first differential transmitting terminal Y and the second differential transmitting terminal Z. When the DI signal is at a high level, the first differential transmitting terminal Y is at a logical high level and the second differential transmitting terminal Z is at a logical low level to form a differential output mode. When the DI signal is at a logical low level, the first differential transmitting terminal Y is at a logical low level and the second differential transmitting terminal Z is at a logical high level to form a differential output mode. When the first differential receiving terminal A is at a logical low level and the second differential receiving terminal B is at a logical high level, the receiving channel TTL signal terminal RO outputs a low-level RO signal to the CPU module. When the first differential receiving terminal A is at a logical high level and the second differential receiving terminal B is at a logical low level, the receiving channel TTL signal terminal RO outputs a high-level RO signal to the CPU module.

[0067] 3. Use two portable relay protection testers of the present invention to build a multiplexing and demultiplexing communication system

[0068] As Figure 2 shown in the figure, the two portable relay protection testers of the present invention are respectively: relay protection tester A and relay protection tester B, which are connected by an Ethernet cable.

[0069] The Ethernet cable includes a first cable, a second cable, a third cable, a fourth cable, a fifth cable, a sixth cable, a seventh cable, and an eighth cable. Among them, the first cable and the second cable form a first twisted pair, the third cable and the sixth cable form a second twisted pair, the fourth cable and the fifth cable form a third twisted pair, and the seventh cable and the eighth cable form a fourth twisted pair.

[0070] The connection between relay protection tester A and relay protection tester B is as follows:

[0071] The first pin PIN1-TP0+ of the RJ45 socket of relay protection tester A is connected to the first pin PIN1-TP0+ of the RJ45 socket of relay protection tester B through the first cable;

[0072] The second pin PIN2-TP0- of the RJ45 socket of relay protection tester A is connected to the second pin PIN2-TP0- of the RJ45 socket of relay protection tester B through the second cable;

[0073] The third pin PIN3-TP1+ of the RJ45 socket of relay protection tester A is connected to the third pin PIN3-TP1+ of the RJ45 socket of relay protection tester B through the third cable;

[0074] The fourth pin PIN4-TP2+ of the RJ45 socket of relay protection tester A is connected to the fourth pin PIN4-TP2+ of the RJ45 socket of relay protection tester B through the fourth cable;

[0075] The fifth pin PIN5-TP2- of the RJ45 socket of relay protection tester A is connected to the fifth pin PIN5-TP2- of the RJ45 socket of relay protection tester B through the fifth cable;

[0076] The sixth pin PIN6-TP1- of the RJ45 socket of relay protection tester A is connected to the sixth pin PIN6-TP1- of the RJ45 socket of relay protection tester B through the sixth cable;

[0077] The seventh pin PIN7-TP3+ of the RJ45 socket of relay protection tester A is connected to the eighth pin PIN8-TP3- of the RJ45 socket of relay protection tester B through the seventh cable;

[0078] The eighth pin PIN8-TP3- of the RJ45 socket of relay protection tester A is connected to the seventh pin PIN7-TP3+ of the RJ45 socket of relay protection tester B through the eighth cable.

[0079] 4. Use a multiplexing and demultiplexing communication system to process Ethernet data

[0080] As Figure 3 shown, it is the equivalent circuit of the Ethernet connection between relay protection tester A and relay protection tester B. The method for processing Ethernet data is as follows:

[0081] 4.1. Relay protection tester A sends Ethernet data, and relay protection tester B demultiplexes Ethernet data

[0082] 4.1.1. The method for signal multiplexing and demultiplexing of the Ethernet communication link between the first secondary wire head TP0+ and the second secondary wire head TP0- of relay protection tester A and the first secondary wire head TP0+ and the second secondary wire head TP0- of relay protection tester B is as follows:

[0083] Step 1: The CPU module of the first portable relay protection tester sends Ethernet data to the Ethernet PHY chip. The Ethernet PHY chip converts the Ethernet data into a first Ethernet differential voltage signal Vtr0_a and transmits it to the first primary wire head TRD0+ and the second primary wire head TRD0- of the first sub-transformer. The first sub-transformer converts the first Ethernet differential voltage signal Vtr0_a into a first Ethernet differential transmission signal in a 1:1 amplitude ratio and outputs it through the first secondary wire head TP0+ and the second secondary wire head TP0- of the first sub-transformer. Define the voltage value of the first secondary wire head TP0+ minus the second secondary wire head TP0- as Vtp0_a;

[0084] Step 2: Equivalent the first secondary wire head TP0+ and the second secondary wire head TP0- of the first portable relay protection tester to a voltage source Ve1_a and a voltage source Ve2_a. The voltage of the voltage source Ve1_a is the voltage of the first secondary wire head TP0+ minus the voltage of the first secondary center tap TC0; the voltage of the voltage source Ve2_a is the voltage of the first secondary center tap TC0 minus the voltage of the second secondary wire head TP0-. Due to the winding characteristics of the Ethernet transformer, Ve1_a and Ve2_a have equal amplitudes and the same polarities; the voltage Vtp0_a between the first secondary wire head TP0+ and the second secondary wire head TP0- is expressed as:

[0085] Vtp0_a = Ve1_a + Ve2_a (1)

[0086] Step 3: Equivalent the first differential transmitter Y and the second differential transmitter Z of the RS485 transceiver of the first portable relay protection tester to a voltage source RS1 and a voltage source RS2. The voltages of the voltage source RS1 and the voltage source RS2 are Vrs1_a and Vrs2_a respectively;

[0087] Step 4: Compound the voltage Vrs1_a of the first differential transmitter Y of the first portable relay protection tester to the first secondary center tap TC0. Then the voltages Vtp0+_a of the first secondary wire head TP0+ and Vtp0-_a of the second secondary wire head TP0- of the relay protection test A are respectively:

[0088] Vtp0+_a = Ve1_a + Vrs1_a (2)

[0089] Vtp0-_a = Vrs1_a - Ve2_a (3)

[0090] Step 5: The first Ethernet differential transmission signal of the first portable relay protection tester is transmitted to the first sub-line head TP0+ and the second sub-line head TP0- of the second portable relay protection tester through the first sub-line head TP0+ and the second sub-line head TP0-. Moreover, the second differential transmitter Z of the second portable relay protection tester is also driven to the first sub-side center tap TC0 on the side of the second portable relay protection tester. The RS485 receiving side is in a high impedance state, and its voltage value is ignored.

[0091] Step 6: The voltage of the first sub-line head TP0+ of the second portable relay protection tester is Vtp0+_b, which is equal to the voltage Vtp0+_a of the first sub-line head TP0+ of the first portable relay protection tester; the voltage of the second sub-line head TP0- of the second portable relay protection tester is Vtp0-_b, which is equal to the voltage Vtp0-_a of the second sub-line head TP0- of the first portable relay protection tester, that is:

[0092] Vtp0+_b = Vtp0+_a (4)

[0093] Vtp0-_b = Vtp0-_a (5)

[0094] Step 7: The voltage Vtp0_b obtained by subtracting the voltage Vtp0-_b of the second sub-line head TP0- from the voltage Vtp0+_b of the first sub-line head TP0+ of the second portable relay protection tester is:

[0095] Vtp0_b = Vtp0+_b - Vtp0-_b (6)

[0096] According to the above formulas (2), (3), (4), and (5), Vtp0_b is:

[0097] Vtp0_b = (Ve1_a + Vrs1_a) - (Vrs1_a - Ve2_a) = Ve1_a + Ve2_a = Vtp0_a (7)

[0098] 4.1.2 The method of signal multiplexing and demultiplexing for the Ethernet communication link between the third sub-line head TP1+ and the fourth sub-line head TP1- of relay protection tester A and the third sub-line head TP1+ and the fourth sub-line head TP1- of relay protection tester B is the same as the method in section 4.1.1.

[0099] 4.2 Relay protection tester B sends Ethernet data, and relay protection tester A demultiplexes Ethernet data

[0100] The method of signal multiplexing and demultiplexing for the Ethernet communication link from relay protection tester B to relay protection tester A is the same as the method in section 4.1.

[0101] When the relay protection tester communicates with other Ethernet devices, such as power Ethernet, its circuit signal characteristics are similar to those when two relay protection testers are connected, which will not be elaborated here.

[0102] 5. Processing RS485 data using a multiplexing and demultiplexing communication system

[0103] As Figure 4 shown, it is the equivalent circuit of the relay protection tester A and the relay protection tester B connected through the RS485 interface. The processing method for RS485 data is as follows:

[0104] 5.1. The relay protection tester A sends RS485 data and the relay protection tester B demultiplexes the RS485 data

[0105] Step a, the CPU module of the relay protection tester A generates RS485 data and sends it to the TTL signal end DI of the RS485 transmission channel, which is converted into an RS485 differential transmission signal and transmitted to the first differential sending end Y and the second differential sending end Z. The first differential sending end Y is equivalent to the voltage source RS1, and the second differential sending end Z is equivalent to the voltage source RS2. The voltages of the voltage sources RS1 and RS2 are Vrs1 and Vrs2 respectively, and the differential output voltage is Vrs_a, and Vrs_a = Vrs1 - Vrs2; Vrs1 and Vrs are respectively output to the first secondary center tap TC0 and the second secondary center tap TC1 of the relay protection tester A;

[0106] Step b, applying the voltage Vrs1 to the first secondary center tap TC0 of the relay protection tester A, then the voltages Vtp0+_a of the first secondary wire head TP0+ and Vtp0-_a of the second secondary wire head TP0- are respectively:

[0107] Vtp0+_a = Ve1_a + Vrs1_a (8)

[0108] Vtp0-_a = Vrs1_a - Ve2_a (9)

[0109] Step c, the voltages Vtp0+_a of the first secondary wire head TP0+ and Vtp0-_a of the second secondary wire head TP0- of the relay protection tester A are respectively transmitted to the first secondary wire head TP0+ and the second secondary wire head TP0- of the relay protection tester B through the first twisted pair. The voltage Vtc0_b of the first secondary center tap TC0 of the relay protection tester B is:

[0110] Vtc0_b = (Vtp0+_a + Vtp0-_a) / 2 = (Ve1_a + Vrs1_a + Vrs1_a - Ve2_a) / 2 (10)

[0111] Since the amplitudes of Ve1_a and Ve2_a are equal and their polarities are the same, the voltage Vtc0_b at the center tap TC0 of the first secondary side of relay protection tester B is:

[0112] Vtc0_b = (Vrs1_a + Vrs1_a) / 2 = Vrs1_a (11)

[0113] Step d. Similarly, the voltage at the center tap TC1 of the second secondary side of relay protection tester B is Vtc1_b = Vrs2_a;

[0114] Step e. The receiving-end voltage Vab_b of the RS485 transceiver of relay protection tester B is:

[0115] Vab_b = Vtc0_b - Vtc1_b = Vrs1_a - Vrs2_a = Vrs_a (12)

[0116] 5.2. Relay protection tester B sends RS485 data, and relay protection tester A demultiplexes RS485 data

[0117] The RS485 receiver on the side of relay protection tester B demultiplexes the RS485 transmission signal from the opposite side, and the method is the same as that in part 5.1.

[0118] As Figure 5 shown, when the relay protection tester is connected to other RS485 interface devices, such as an isolated RS485 communication interface, its circuit signal characteristics are similar to those when two relay protection testers are connected, and will not be elaborated here.

[0119] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A portable relay protection tester, characterized in that, It includes a CPU module, an Ethernet PHY chip, an Ethernet transformer, an RS485 transceiver, an RJ45 socket, a resistor R1, a resistor R2, and a capacitor C1; the input end of the Ethernet PHY chip is connected to the CPU module, the output end of the Ethernet PHY chip is connected to the primary side of the Ethernet transformer, and the secondary side of the Ethernet transformer is connected to the RJ45 socket; the first differential receiving end A, the second differential receiving end B, the first differential sending end Y, and the second differential sending end Z of the RS485 transceiver are respectively connected to the secondary side of the Ethernet transformer, and the receiving channel TTL signal end RO, the sending control end RE, and the transmitting channel TTL signal end DI of the RS485 transceiver are respectively connected to the CPU module; The Ethernet transformer includes a first sub-transformer and a second sub-transformer; the primary winding of the first sub-transformer is connected to the MII_TX interface of the CPU module through the Ethernet PHY chip; the primary winding of the second sub-transformer is connected to the MII_RX interface of the CPU module through the Ethernet PHY chip; The secondary winding of the first sub-transformer includes a first secondary wire head TP0+, a second secondary wire head TP0-, and a first secondary center tap TC0; the secondary winding of the second sub-transformer includes a third secondary wire head TP1+, a fourth secondary wire head TP1-, and a second secondary center tap TC1; the first secondary center tap TC0 is respectively connected to the second differential receiving end B, the second differential sending end Z, and one end of the resistor R1, the second secondary center tap TC1 is respectively connected to the first differential receiving end A, the first differential sending end Y, and one end of the resistor R2, and the other ends of the resistor R1 and the resistor R2 are connected and then grounded through the capacitor C1.

2. The portable relay protection tester according to claim 1, wherein The sending control end RE is used to control the output signal. When the RS485 transceiver needs to output, the sending control end RE is controlled by the CPU module to be low. When the RS485 transceiver needs to receive, the sending control end RE is controlled by the CPU module to be high; when the RS485 transceiver outputs, the DI signal sent by the CPU module is input from the transmitting channel TTL signal end DI and then converted into a differential signal, and is output through the first differential sending channel composed of the first differential sending end Y and the second differential sending end Z. When the DI signal is high, the first differential sending end Y is logic high and the second differential sending end Z is logic low to form a differential output mode. When the DI signal is logic low, the first differential sending end Y is logic low and the second differential sending end Z is logic high to form a differential output mode; when the first differential receiving end A is logic low and the second differential receiving end B is logic high, the receiving channel TTL signal end RO outputs a low-level RO signal to the CPU module; When the first differential receiving end A is logic high and the second differential receiving end B is logic low, the receiving channel TTL signal end RO outputs a high-level RO signal to the CPU module.

3. The portable relay protection tester according to claim 1, characterized in that, The primary winding of the first sub-transformer includes a first primary wire head TRD0+, a second primary wire head TRD0-, and a first primary center tap COM0; the primary winding of the second sub-transformer includes a third primary wire head TRD1+, a fourth primary wire head TRD1-, and a second primary center tap COM1; the first primary wire head TRD0+, the second primary wire head TRD0-, and the first primary center tap COM0 are respectively connected to the Ethernet PHY chip; the third primary wire head TRD1+, the fourth primary wire head TRD1-, and the second primary center tap COM1 are respectively connected to the Ethernet PHY chip.

4. The portable relay protection tester according to claim 1, wherein The first secondary wire head TP0+, the second secondary wire head TP0-, the third secondary wire head TP1+, and the fourth secondary wire head TP1- are respectively connected to the PIN1-TP0+ pin, PIN2-TP0- pin, PIN3-TP1+ pin, and PIN6-TP1- pin of the RJ45 socket, and are electrically connected to the PIN5-TP2- pin of the RJ45 socket, and the PIN4-TP2+ pin of the RJ45 socket is left unconnected.

5. The portable relay protection tester according to claim 1, wherein It further includes an RS232 transceiver. The TTL signal end TTL_OUT of the RS232 transmission channel and the TTL signal end TTL_IN of the RS232 reception channel of the RS232 transceiver are respectively connected to the CPU module; the serial signal end RS232_OUT of the transmission channel and the serial signal end RS232_IN of the reception channel of the RS232 transceiver are respectively connected to the PIN7-TP3+ pin and PIN8-TP3- pin of the RJ45 socket.

6. A multiplexing and demultiplexing communication system, characterized in that, It includes two portable relay protection testers as described in any one of claims 1-5 and an Ethernet cable. The two portable relay protection testers are respectively a first portable relay protection tester and a second portable relay protection tester, and the first portable relay protection tester and the second portable relay protection tester are connected through the Ethernet cable.

7. The multiplexing and demultiplexing communication system according to claim 6, wherein The Ethernet cable includes a first cable, a second cable, a third cable, a fourth cable, a fifth cable, a sixth cable, a seventh cable, and an eighth cable. Among them, the first cable and the second cable form a first twisted pair, the third cable and the sixth cable form a second twisted pair, the fourth cable and the fifth cable form a third twisted pair, and the seventh cable and the eighth cable form a fourth twisted pair.

8. The multiplexing and demultiplexing communication system according to claim 7, characterized in that, The first pin PIN1-TP0+ of the RJ45 socket of the first portable relay protection tester is connected to the first pin PIN1-TP0+ of the RJ45 socket of the second portable relay protection tester through the first cable; the second pin PIN2-TP0- of the RJ45 socket of the first portable relay protection tester is connected to the second pin PIN2-TP0- of the RJ45 socket of the second portable relay protection tester through the second cable; the third pin PIN3-TP1+ of the RJ45 socket of the first portable relay protection tester is connected to the third pin PIN3-TP1+ of the RJ45 socket of the second portable relay protection tester through the third cable; the fourth pin PIN4-TP2+ of the RJ45 socket of the first portable relay protection tester is connected to the fourth pin PIN4-TP2+ of the RJ45 socket of the second portable relay protection tester through the fourth cable; the fifth pin PIN5-TP2- of the RJ45 socket of the first portable relay protection tester is connected to the fifth pin PIN5-TP2- of the RJ45 socket of the second portable relay protection tester through the fifth cable; the sixth pin PIN6-TP1- of the RJ45 socket of the first portable relay protection tester is connected to the sixth pin PIN6-TP1- of the RJ45 socket of the second portable relay protection tester through the sixth cable; the seventh pin PIN7-TP3+ of the RJ45 socket of the first portable relay protection tester is connected to the eighth pin PIN8-TP3- of the RJ45 socket of the second portable relay protection tester through the seventh cable; the eighth pin PIN8-TP3- of the RJ45 socket of the first portable relay protection tester is connected to the seventh pin PIN7-TP3+ of the RJ45 socket of the second portable relay protection tester through the eighth cable.

9. The multiplexing and demultiplexing communication system according to claim 6, characterized in that, When an Ethernet connection is adopted between the first secondary wire head TP0+ and the second secondary wire head TP0- of the first portable relay protection tester and the first secondary wire head TP0+ and the second secondary wire head TP0- of the second portable relay protection tester, the multiplexing and demultiplexing method is as follows: Step 1, the CPU module of the first portable relay protection tester sends the Ethernet data to the Ethernet PHY chip, and the Ethernet PHY chip converts the Ethernet data into a first Ethernet differential voltage signal Vtr0_a and transmits it to the first primary wire head TRD0+ and the second primary wire head TRD0- of the first sub-transformer. The first sub-transformer converts the first Ethernet differential voltage signal Vtr0_a into a first Ethernet differential transmission signal in a 1:1 amplitude manner and outputs it through the first secondary wire head TP0+ and the second secondary wire head TP0- of the first sub-transformer. Define the voltage value of the first secondary wire head TP0+ minus the second secondary wire head TP0- as Vtp0_a; Step 2: Equivalent the first secondary wire head TP0+ and the second secondary wire head TP0- of the first portable relay protection tester to voltage sources Ve1_a and Ve2_a. The voltage of voltage source Ve1_a is the voltage of the first secondary wire head TP0+ minus the voltage of the first secondary center tap TC0; the voltage of voltage source Ve2_a is the voltage of the first secondary center tap TC0 minus the voltage of the second secondary wire head TP0-. Due to the winding characteristics of the Ethernet transformer, the amplitudes of Ve1_a and Ve2_a are equal and the polarities are the same. The voltage Vtp0_a between the first secondary wire head TP0+ and the second secondary wire head TP0- is expressed as: Vtp0_a = Ve1_a + Ve2_a (1) Step 3: Equivalent the first differential sending end Y and the second differential sending end Z of the RS485 transceiver of the first portable relay protection tester to voltage sources RS1 and RS2, and the voltages of voltage sources RS1 and RS2 are Vrs1_a and Vrs2_a respectively; Step 4: Compound the voltage Vrs1_a of the first differential sending end Y of the first portable relay protection tester to the first secondary center tap TC0. Then the voltages Vtp0+_a of the first secondary wire head TP0+ and Vtp0-_a of the second secondary wire head TP0- of the relay protection test A are respectively: Vtp0+_a=Ve1_a + Vrs1_a (2) Vtp0-_a=Vrs1_a - Ve2_a (3) Step 5: The first Ethernet differential transmission signal of the first portable relay protection tester is transmitted to the first secondary wire head TP0+ and the second secondary wire head TP0- of the second portable relay protection tester through the first secondary wire head TP0+ and the second secondary wire head TP0-. And the second differential sending end Z of the second portable relay protection tester is also driven to the first secondary center tap TC0 on the side of the second portable relay protection tester. The RS485 receiving side is in a high-impedance state and its voltage value is ignored; Step 6: The voltage of the first secondary wire head TP0+ of the second portable relay protection tester is Vtp0+_b, which is equal to the voltage Vtp0+_a of the first secondary wire head TP0+ of the first portable relay protection tester; the voltage of the second secondary wire head TP0- of the second portable relay protection tester is Vtp0-_b, which is equal to the voltage Vtp0-_a of the second secondary wire head TP0- of the first portable relay protection tester, that is: Vtp0+_b = Vtp0+_a (4) Vtp0-_b = Vtp0-_a (5) Step 7: The voltage Vtp0_b of the voltage obtained by subtracting the voltage Vtp0-_b of the second secondary wire head TP0- from the voltage Vtp0+_b of the first secondary wire head TP0+ of the second portable relay protection tester is: Vtp0_b = Vtp0+_b - Vtp0-_b (6) According to the above formulas (2), (3), (4), and (5), Vtp0_b is: Vtp0_b = (Ve1_a + Vrs1_a)-(Vrs1_a - Ve2_a)= Ve1_a + Ve2_a = Vtp0_a (7).

10. The multiplexing and demultiplexing communication system according to claim 6, characterized in that, When the first portable relay protection tester and the second portable relay protection tester are connected by an RS485 interface, the multiplexing and demultiplexing methods are as follows: Step a, the CPU module of relay protection tester A generates RS485 data and sends it to the TTL signal terminal DI of the RS485 transmission channel, which is converted into an RS485 differential transmission signal and transmitted to the first differential transmission terminal Y and the second differential transmission terminal Z. The first differential transmission terminal Y is equivalent to the voltage source RS1, and the second differential transmission terminal Z is equivalent to the voltage source RS2. The voltages of the voltage sources RS1 and RS2 are Vrs1 and Vrs2 respectively, and the differential output voltage is Vrs_a, and Vrs_a = Vrs1 - Vrs2; Vrs1 and Vrs are respectively output to the first secondary center tap TC0 and the second secondary center tap TC1 of relay protection tester A; Step b, apply the voltage Vrs1 to the first secondary center tap TC0 of relay protection tester A, then the voltages Vtp0+_a of the first secondary wire head TP0+ and Vtp0-_a of the second secondary wire head TP0- are respectively: Vtp0+_a=Ve1_a + Vrs1_a (8) Vtp0-_a=Vrs1_a - Ve2_a (9) Step c, the voltages Vtp0+_a of the first secondary wire head TP0+ and Vtp0-_a of the second secondary wire head TP0- of relay protection tester A are respectively transmitted to the first secondary wire head TP0+ and the second secondary wire head TP0- of relay protection tester B through the first twisted pair. The voltage Vtc0_b of the first secondary center tap TC0 of relay protection tester B is: Vtc0_b=(Vtp0+_a + Vtp0-_a) / 2 = (Ve1_a + Vrs1_a + Vrs1_a - Ve2_a) / 2 (10) Since the amplitudes of Ve1_a and Ve2_a are equal and the polarities are the same, the voltage Vtc0_b of the first secondary center tap TC0 of relay protection tester B is: Vtc0_b=(Vrs1_a + Vrs1_a) / 2 = Vrs1_a (11) Step d, similarly, the voltage of the second secondary center tap TC1 of relay protection tester B is Vtc1_b=Vrs2_a; Step e, the receiving end voltage Vab_b of the RS485 transceiver of relay protection tester B is: Vab_b=Vtc0_b - Vtc1_b =Vrs1_a - Vrs2_a = Vrs_a (12).

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