220v electric fire monitoring detector and its alarm method

Abstract

A 220V electrical fire monitoring detector and its alarm method, comprising: a residual current sensor obtains the vector sum of the fire line current and the zero line current of the power supply system as the residual current, a voltage measurement module obtains the voltage difference of the fire line and the zero line of the power supply system, a signal processing module calculates the fundamental wave and harmonic of the residual current and the voltage difference, a wiring detection module obtains the ground admittance of the fundamental wave and the harmonic according to the calculation result of the signal processing module, if the difference of the real parts of the ground admittance of the fundamental wave and the harmonic is zero, it is determined that the electrical equipment is normally wired, and the ground insulation resistance is calculated under the condition of no wrong wiring; if the difference of the real parts of the ground admittance of the fundamental wave and the harmonic is greater than zero, it is determined that the electrical equipment exists wrong wiring, and the ground insulation resistance is calculated under the condition of wrong wiring; the alarm module alarms after the adjusted delay time when the ground insulation resistance is lower than the threshold value. The application solves the false alarm problem caused by the capacitive component of the residual current and the wrong wiring of the electrical fire monitoring detector.

Description

Technical Field

[0001] This invention belongs to the field of electrical fire monitoring technology, specifically relating to a 220V electrical fire monitoring detector and its alarm method. Background Technology

[0002] To prevent electrical fires, residual current type electrical fire monitoring detectors are commonly installed on low-voltage 220V lines. When the residual current reaches or exceeds the alarm set value, the residual current type electrical fire monitoring detector will issue an alarm signal after a delay, which can prevent electrical fires caused by prolonged leakage current to ground.

[0003] The residual current type electrical fire monitoring detector mainly consists of a residual current sensor and a signal processing module. The residual current sensor (CT) takes the vector sum of the instantaneous values ​​of the live wire current and the neutral wire current. Under normal operating conditions and without leakage current in the protected circuit, the residual current i... r The residual current i is zero when the insulation resistance of the protected circuit decreases and leakage to ground occurs. r It is no longer zero. When the residual current i r When the alarm threshold is exceeded, the residual current device (RCD) will activate and trigger an alarm after a set delay time. However, residual current-type electrical fire monitoring detectors installed on-site frequently trigger false alarms, such as due to incorrect wiring causing the measured residual current to include load current. Under normal wiring conditions, the residual current i r Leakage current to ground i including insulation resistance R and ground capacitance current i C Two parts. In cases of incorrect wiring, such as mixed neutral and ground connections or mixed neutral wire connections, the measured residual current i... r The residual current includes not only the current from ground resistance and capacitance, but also a portion of the load current. Since the residual current is in the milliampere range, while the load current is in the ampere range, the load current is much larger than the residual current. According to GB14287.2-2014 "Electrical Fire Monitoring System Part 2: Residual Current Type Electrical Fire Monitoring Detector," the alarm value of an electrical fire detector should be set between 20mA and 1000mA. Therefore, incorrect wiring often leads to false alarms. Capacitive current can also cause false alarms. In fact, the protected circuit, including lines and electrical equipment, has not only ground insulation resistance but also ground distributed capacitance. Therefore, the residual current includes resistive residual current generated by ground insulation resistance and capacitive residual current generated by ground distributed capacitance. Of these, the resistive residual current, that is, the resistive residual current generated by ground insulation damage or degradation, is what truly causes electrical fires. The contribution of capacitive residual current to electrical fires is very small. However, when the capacitive residual current is large, it can also cause false alarms.

[0004] In existing technologies, most residual current-based electrical fire monitoring detectors activate based on whether the measured residual current reaches an alarm setpoint. They cannot distinguish between resistive and capacitive components in the residual current, often leading to frequent false alarms due to excessive capacitive residual current. However, some single-phase 220V residual current-based electrical fire monitoring detectors can calculate the phase angle between voltage and residual current. Based on this phase angle, they can separate and calculate the resistive residual current component, thereby obtaining the resistive leakage current within the residual current. Insulation resistance calculations based on the resistive leakage current and the distribution line voltage can prevent false alarms caused by excessive capacitive residual current. However, the problem of false alarms caused by incorrect wiring remains unresolved. In single-phase 220V circuits, especially in 220V building power supply systems, the phenomenon of incorrectly connecting the neutral wire of electrical equipment to the PE line (i.e., a mixed neutral-to-ground connection) does not affect the normal operation of the equipment, making this phenomenon very common. Furthermore, connecting the neutral wire of one circuit to the neutral wire of another circuit also does not affect the normal operation of the equipment, so mixed neutral wire connections are also prevalent. This has led to frequent false alarms from existing residual current type electrical fire monitoring detectors, seriously affecting their effectiveness. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a 220V electrical fire monitoring detector and its alarm method, which solves the problems of capacitive components of residual current and false alarms caused by incorrect wiring of the electrical fire monitoring detector.

[0006] The present invention adopts the following technical solution.

[0007] This invention proposes a 220V electrical fire monitoring detector, which is connected to the power supply system along with the electrical equipment. The electrical fire monitoring detector includes: a residual current sensor, a voltage measurement module, a signal processing module, a wiring detection module, and an alarm module.

[0008] The residual current sensor acquires the vector sum of the live wire current and the neutral wire current of the power supply system as the residual current and sends it to the signal processing module.

[0009] The voltage measurement module acquires the voltage difference between the live wire and the neutral wire of the power supply system and sends it to the signal processing module;

[0010] The signal processing module calculates the fundamental and harmonic phasors of the residual current, calculates the fundamental and harmonic phasors of the voltage difference, and sends the calculation results to the wiring detection module.

[0011] The wiring detection module calculates the ground admittance of the fundamental and harmonic waves based on the calculation results of the signal processing module. If the difference between the real parts of the ground admittance of the fundamental and harmonic waves is zero, it is determined that all electrical equipment in the power supply system is properly wired, and the ground insulation resistance of the power supply system is calculated based on the condition of no incorrect wiring. If the difference between the real parts of the ground admittance of the fundamental and harmonic waves is greater than zero, it is determined that there is incorrect wiring in the electrical equipment in the power supply system, and the ground insulation resistance of the power supply system is calculated based on the condition of incorrect wiring.

[0012] The alarm module is used to trigger an alarm after a set delay when the insulation resistance to ground is lower than a threshold value.

[0013] Preferably, incorrect wiring of electrical equipment includes: incorrect neutral wire connection.

[0014] Preferably, the wiring detection module includes: a ground admittance calculation unit, a misconnection judgment unit, and a ground insulation resistance calculation unit; wherein,

[0015] The ground admittance calculation unit calculates the ground admittance of the fundamental wave and the ground admittance of the harmonic wave based on the fundamental phasor and harmonic phasor of the residual current and voltage difference input from the signal processing module.

[0016] The incorrect wiring judgment unit determines that if the difference between the real parts of the fundamental and harmonic admittances to ground is zero, the electrical equipment in the power supply system is correctly wired; if the difference between the real parts of the fundamental and harmonic admittances to ground is greater than zero, the electrical equipment in the power supply system is incorrectly wired.

[0017] The ground insulation resistance calculation unit uses the reciprocal of the real part of the fundamental wave's ground admittance as the ground insulation resistance when all electrical equipment is properly wired. When there are incorrect wiring issues, the ratio of the difference between the normalized imaginary part of the harmonic ground admittance and the imaginary part of the fundamental wave's ground admittance to the difference between the real parts of the fundamental and harmonic ground admittances is used as the coefficient corresponding to the incorrect wiring condition. The ground insulation resistance is calculated using the coefficient corresponding to the incorrect wiring condition, the harmonic order, and the real part of the fundamental wave's ground admittance.

[0018] This invention also proposes an alarm method for a 220V electrical fire monitoring detector, comprising:

[0019] Step 1: The residual current sensor obtains the vector sum of the live wire current and the neutral wire current of the power supply system as the residual current, and the voltage measurement module obtains the voltage difference between the live wire and the neutral wire of the power supply system.

[0020] Step 2: Calculate the fundamental phasor and harmonic phasor of the voltage based on the FFT method, and calculate the fundamental phasor and harmonic phasor of the residual current.

[0021] Step 3: Calculate the ground admittance of the fundamental and harmonic waves using the fundamental and harmonic phasors of the voltage and the residual current.

[0022] Step 4: Calculate the difference between the real parts of the fundamental and harmonic admittances to ground;

[0023] Step 5: If the difference between the real parts of the fundamental and harmonic admittances to ground is zero, calculate the insulation resistance to ground of the power supply system under the condition of no incorrect wiring; if the difference between the real parts of the fundamental and harmonic admittances to ground is greater than zero, calculate the insulation resistance to ground of the power supply system under the condition of incorrect wiring.

[0024] Step 6, if the insulation resistance to ground is lower than the threshold value R set Then the electrical fire monitoring detector will activate after the set delay time.

[0025] Preferably, the harmonic is the third harmonic.

[0026] Preferably, the fundamental admittance to ground is calculated using the following formula. :

[0027]

[0028] In the formula,

[0029] and These are the fundamental phasors of the residual current and voltage, respectively.

[0030] B re.1 B im.1 These are the real and imaginary parts of the fundamental admittance to the ground, respectively.

[0031] Preferably, the harmonic admittance to ground is calculated using the following formula. :

[0032]

[0033] In the formula,

[0034] and These are the harmonic phasors of the residual current and voltage, respectively.

[0035] B re.h B im.h These are the real and imaginary parts of the harmonic admittance to ground, respectively.

[0036] Preferably, the difference between the real parts of the fundamental and harmonic admittances to ground is zero, then the insulation resistance to ground is calculated using the following formula:

[0037]

[0038] In the formula, R is the insulation resistance to ground.

[0039] Preferably, if the difference between the real parts of the fundamental and harmonic admittances to ground is greater than zero, then the ground insulation resistance is calculated using the following formula:

[0040]

[0041]

[0042] In the formula,

[0043] R is the insulation resistance to ground.

[0044] h is the harmonic order.

[0045] x is the coefficient corresponding to the condition of incorrect wiring.

[0046] Preferably, the threshold value R is calculated using the following relationship: set :

[0047]

[0048] In the formula,

[0049] U is the voltage difference between the live wire and the neutral wire.

[0050] I r.set The residual current alarm value for the electrical fire detector is greater than or equal to 20mA and less than or equal to 1000mA.

[0051] The beneficial effects of this invention are that, compared with the prior art, it uses the difference between the real parts of the ground admittance of the fundamental and harmonic waves of the residual current and voltage difference to determine whether there is a wiring error in the electrical equipment in the power supply system. It also calculates the ground insulation resistance of the power supply system according to the specific conditions of no wiring error or wiring error. This not only can timely detection of wiring errors, but also improves the alarm reliability of the 220V electrical fire monitoring detector, effectively solving the problem of frequent false alarms, and has good practical value.

[0052] The method for identifying incorrect wiring and the method for calculating the insulation resistance to ground under conditions of incorrect wiring proposed in this invention are simple, feasible, and easy to implement in engineering. Attached Figure Description

[0053] Figure 1 This is a schematic diagram of the normal wiring of a single-phase 220V electrical fire monitoring detector in an embodiment of the present invention;

[0054] Figure 2 This is a schematic diagram of a single-phase 220V electrical fire monitoring detector with neutral-to-ground mixed connection in an embodiment of the present invention;

[0055] Figure 3This is a schematic diagram of the neutral wire misconnection of a single-phase 220V electrical fire monitoring detector in an embodiment of the present invention. Detailed Implementation

[0056] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this invention. The embodiments described in this application are merely some embodiments of this invention, and not all embodiments. Based on the spirit of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this invention.

[0057] This invention proposes a 220V electrical fire monitoring detector, which is connected to the power supply system along with the electrical equipment. The electrical fire monitoring detector includes: a residual current sensor, a voltage measurement module, a signal processing module, a wiring detection module, and an alarm module.

[0058] The residual current sensor acquires the vector sum of the live wire current and the neutral wire current of the power supply system as the residual current and sends it to the signal processing module.

[0059] The voltage measurement module acquires the voltage difference between the live wire and the neutral wire of the power supply system and sends it to the signal processing module;

[0060] The signal processing module calculates the fundamental and harmonic phasors of the residual current, calculates the fundamental and harmonic phasors of the voltage difference, and sends the calculation results to the wiring detection module.

[0061] The wiring detection module calculates the ground admittance of the fundamental and harmonic waves based on the calculation results of the signal processing module. If the difference between the real parts of the ground admittance of the fundamental and harmonic waves is zero, it is determined that all electrical equipment in the power supply system is properly wired, and the ground insulation resistance of the power supply system is calculated based on the condition of no incorrect wiring. If the difference between the real parts of the ground admittance of the fundamental and harmonic waves is greater than zero, it is determined that there is incorrect wiring in the electrical equipment in the power supply system, and the ground insulation resistance of the power supply system is calculated based on the condition of incorrect wiring.

[0062] The alarm module is used to trigger an alarm after a set delay when the insulation resistance to ground is lower than a threshold value.

[0063] Specifically, incorrect wiring of electrical equipment includes, but is not limited to, incorrect neutral wire wiring.

[0064] In a non-limiting preferred embodiment, the neutral wire of the electrical equipment is connected to the ground wire, i.e., the PE wire, which is the wire that grounds the equipment casing, causing a neutral wire wiring error; for example, the neutral wire of this circuit should pass through the residual current transformer of this circuit, but it is connected to the residual current transformer of the adjacent circuit and flows back to the system, which also causes a neutral wire wiring error.

[0065] In existing technology, the normal wiring of a 220V residual current type electrical fire monitoring detector is as follows: Figure 1 As shown, both the live wire and the neutral wire pass through the residual current transformer in this circuit. Under normal wiring conditions, the residual current i r As shown below:

[0066] i r =i L +i N =(i R +i C +i fh1 +i fh2 )-(i fh1 +i fh2 ) = i R +i C (1)

[0067] In the formula,

[0068] i L i N These are the live wire current and the neutral wire current, respectively.

[0069] i R i C These are the leakage current to ground and the capacitance current to ground, respectively.

[0070] i fh1 i fh2 These are the first load current and the second load current, respectively.

[0071] Figure 1 in,i RC For i R and i C The current and R and C are the resistance to ground and capacitance to ground, respectively. fh1 R fh2 L1 and L2 are the first and second load resistors, respectively, and L1 and L2 are the first and second load inductors, respectively. u is the voltage.

[0072] In cases of incorrect wiring, such as mixing neutral and ground wires (N wire and PE wire), where the neutral wire should be connected to the PE wire, the PE wire is incorrectly connected instead. Figure 2 As shown, we have:

[0073] i r =i L +i N =(i R +i C +i fh1 +i fh2 )+(-i fh1 ) = i R +i C+i fh2 (2)

[0074] As can be seen from equation (2), in the case of mixed ground connection, the measured residual current includes not only the current of ground resistance and ground capacitance, but also a portion of the load current.

[0075] Another common type of incorrect wiring is mixed neutral wire connection, where the neutral wire of this circuit is connected to another circuit, or the return current from another circuit is connected to the neutral wire of this circuit. Figure 3 As shown.

[0076] according to Figure 3 The residual current of loop 1 is as follows:

[0077] i r =i L +i N =(i R +i C +i L1_fh1 +i L1_fh2 )+(-i L1_fh1 ) = i R +i C +i L1_fh2 (3)

[0078] The residual current in loop 2 is as follows:

[0079]

[0080] As can be seen from equations (3) and (4), in the case of mixed neutral wire connection, the measured residual current includes not only the current of the resistance to ground and the current of the capacitance to ground, but also a part of the load current.

[0081] Specifically, the wiring detection module includes: a ground admittance calculation unit, a misconnection judgment unit, and a ground insulation resistance calculation unit; wherein...

[0082] The ground admittance calculation unit calculates the ground admittance of the fundamental wave and the ground admittance of the harmonic wave based on the fundamental phasor and harmonic phasor of the residual current and voltage difference input from the signal processing module.

[0083] The incorrect wiring judgment unit determines that if the difference between the real parts of the fundamental and harmonic admittances to ground is zero, the electrical equipment in the power supply system is correctly wired; if the difference between the real parts of the fundamental and harmonic admittances to ground is greater than zero, the electrical equipment in the power supply system is incorrectly wired.

[0084] The ground insulation resistance calculation unit uses the reciprocal of the real part of the fundamental wave's ground admittance as the ground insulation resistance when all electrical equipment is properly wired. When there are incorrect wiring issues, the ratio of the difference between the normalized imaginary part of the harmonic ground admittance and the imaginary part of the fundamental wave's ground admittance to the difference between the real parts of the fundamental and harmonic ground admittances is used as the coefficient corresponding to the incorrect wiring condition. The ground insulation resistance is calculated using the coefficient corresponding to the incorrect wiring condition, the harmonic order, and the real part of the fundamental wave's ground admittance.

[0085] This invention also proposes an alarm method for a 220V electrical fire monitoring detector, comprising:

[0086] Step 1: The residual current sensor obtains the vector sum of the live wire current and the neutral wire current of the power supply system as the residual current, and the voltage measurement module obtains the voltage difference between the live wire and the neutral wire of the power supply system.

[0087] Step 2: Calculate the fundamental phasor and harmonic phasor of the voltage based on the FFT method, and calculate the fundamental phasor and harmonic phasor of the residual current.

[0088] Specifically, the calculated phasors include, but are not limited to, amplitude, phase, real part, and imaginary part.

[0089] In a non-limiting preferred embodiment, the harmonic is the third harmonic.

[0090] Step 3: Calculate the ground admittance of the fundamental and harmonic waves using the fundamental and harmonic phasors of the voltage and the residual current.

[0091] Specifically, step 3 includes:

[0092] Step 3.1, calculate the fundamental wave admittance to ground using the following formula.

[0093]

[0094] In the formula, and B represents the fundamental phasor of the residual current and voltage, respectively. re.1 B im.1 These are the real and imaginary parts of the fundamental admittance to the ground, respectively.

[0095] Step 3.2, calculate the harmonic admittance to ground using the following formula. :

[0096]

[0097] In the formula, and The harmonic phasors of the residual current and voltage, respectively, B re.h B im.hThese are the real and imaginary parts of the h-th harmonic's admittance to ground, respectively.

[0098] Step 4: Calculate the difference between the real parts of the ground admittance of the fundamental and harmonic waves.

[0099] Step 5: If the difference between the real parts of the fundamental and harmonic admittances to ground is zero, calculate the insulation resistance to ground of the power supply system under the condition of no incorrect wiring; if the difference between the real parts of the fundamental and harmonic admittances to ground is greater than zero, calculate the insulation resistance to ground of the power supply system under the condition of incorrect wiring.

[0100] Specifically, if the difference between the real parts of the fundamental and harmonic admittances to ground is zero, then the insulation resistance to ground is calculated using the following formula:

[0101]

[0102] In the formula, R is the insulation resistance to ground.

[0103] If the difference between the real parts of the fundamental and harmonic admittances to ground is greater than zero, then the ground insulation resistance can be calculated using the following formula:

[0104]

[0105]

[0106] In the formula,

[0107] R is the insulation resistance to ground.

[0108] h is the harmonic order.

[0109] x is the coefficient corresponding to the condition of incorrect wiring.

[0110] Preferably, the threshold value R is calculated using the following relationship: set :

[0111]

[0112] In the formula,

[0113] U is the voltage difference between the live wire and the neutral wire.

[0114] I r.set The residual current alarm value of the electrical fire detector is specified in GB 14287.2-2014 "Electrical Fire Monitoring System Part 2: Residual Current Type Electrical Fire Monitoring Detector". The alarm value of the electrical fire detector is greater than or equal to 20mA and less than or equal to 1000mA.

[0115] This disclosure can be a system, method, and / or computer program product. A computer program product may include a computer-readable storage medium having computer-readable program instructions loaded thereon for causing a processor to implement various aspects of this disclosure.

[0116] Computer-readable storage media can be tangible devices capable of holding and storing instructions for use by an instruction execution device. Computer-readable storage media can be, for example—but not limited to—electrical storage devices, magnetic storage devices, optical storage devices, electromagnetic storage devices, semiconductor storage devices, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of computer-readable storage media include: portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static random access memory (SRAM), portable compact disc read-only memory (CD-ROM), digital multifunction disc (DVD), memory sticks, floppy disks, mechanical encoding devices, such as punch cards or recessed protrusions storing instructions thereon, and any suitable combination of the foregoing. The computer-readable storage media used herein are not to be construed as transient signals themselves, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through waveguides or other transmission media (e.g., light pulses through fiber optic cables), or electrical signals transmitted through wires.

[0117] The computer-readable program instructions described herein can be downloaded from computer-readable storage media to various computing / processing devices, or downloaded via a network, such as the Internet, local area network, wide area network, and / or wireless network, to an external computer or external storage device. The network may include copper transmission cables, fiber optic transmission, wireless transmission, routers, firewalls, switches, gateway computers, and / or edge servers. A network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards them to the computer-readable storage media in the respective computing / processing device.

[0118] Computer program instructions used to perform the operations of this disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, status setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Smalltalk, C++, etc., and conventional procedural programming languages ​​such as the "C" language or similar programming languages. The computer-readable program instructions may execute entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving a remote computer, the remote computer may be connected to the user's computer via any type of network—including a local area network (LAN) or a wide area network (WAN)—or may be connected to an external computer (e.g., via the Internet using an Internet service provider). In some embodiments, electronic circuitry, such as programmable logic circuitry, field-programmable gate arrays (FPGAs), or programmable logic arrays (PLAs), is personalized by utilizing the status information of the computer-readable program instructions to implement various aspects of this disclosure.

[0119] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A 220V electrical fire monitoring detector, wherein the electrical fire monitoring detector is connected to the power supply system together with the electrical equipment, and the electrical fire monitoring detector includes: The system comprises a residual current sensor, a voltage measurement module, a signal processing module, a wiring detection module, and an alarm module; characterized in that... The residual current sensor acquires the vector sum of the live wire current and the neutral wire current of the power supply system as the residual current and sends it to the signal processing module. The voltage measurement module acquires the voltage difference between the live wire and the neutral wire of the power supply system and sends it to the signal processing module; The signal processing module calculates the fundamental and harmonic phasors of the residual current, calculates the fundamental and harmonic phasors of the voltage difference, and sends the calculation results to the wiring detection module. The wiring detection module calculates the ground admittance of the fundamental and harmonic waves based on the calculation results of the signal processing module. If the difference between the real parts of the ground admittance of the fundamental and harmonic waves is zero, it is determined that all electrical equipment in the power supply system is properly wired, and the ground insulation resistance of the power supply system is calculated based on the condition of no incorrect wiring. If the difference between the real parts of the ground admittance of the fundamental and harmonic waves is greater than zero, it is determined that there is incorrect wiring in the electrical equipment in the power supply system, and the ground insulation resistance of the power supply system is calculated based on the condition of incorrect wiring. The alarm module is used to trigger an alarm after a set delay when the insulation resistance to ground is lower than a threshold value.

2. The 220V electrical fire monitoring detector according to claim 1, characterized in that, Incorrect wiring of electrical equipment includes: incorrect neutral wire connection.

3. The 220V electrical fire monitoring detector according to claim 1, characterized in that, The wiring detection module includes: a ground admittance calculation unit, a miswiring judgment unit, and a ground insulation resistance calculation unit; among which, The ground admittance calculation unit calculates the ground admittance of the fundamental wave and the ground admittance of the harmonic wave based on the fundamental phasor and harmonic phasor of the residual current and voltage difference input from the signal processing module. The incorrect wiring judgment unit determines that if the difference between the real parts of the fundamental and harmonic admittances to ground is zero, the electrical equipment in the power supply system is correctly wired; if the difference between the real parts of the fundamental and harmonic admittances to ground is greater than zero, the electrical equipment in the power supply system is incorrectly wired. The ground insulation resistance calculation unit uses the reciprocal of the real part of the fundamental wave's ground admittance as the ground insulation resistance when all electrical equipment is properly wired. When there are incorrect wiring issues, the ratio of the difference between the normalized imaginary part of the harmonic ground admittance and the imaginary part of the fundamental wave's ground admittance to the difference between the real parts of the fundamental and harmonic ground admittances is used as the coefficient corresponding to the incorrect wiring condition. The ground insulation resistance is calculated using the coefficient corresponding to the incorrect wiring condition, the harmonic order, and the real part of the fundamental wave's ground admittance.

4. An alarm method for a 220V electrical fire monitoring detector, applicable to the 220V electrical fire monitoring detector according to any one of claims 1 to 3, characterized in that, The alarm method includes: Step 1: The residual current sensor obtains the vector sum of the live wire current and the neutral wire current of the power supply system as the residual current, and the voltage measurement module obtains the voltage difference between the live wire and the neutral wire of the power supply system. Step 2: Calculate the fundamental phasor and harmonic phasor of the voltage based on the FFT method, and calculate the fundamental phasor and harmonic phasor of the residual current. Step 3: Calculate the ground admittance of the fundamental and harmonic waves using the fundamental and harmonic phasors of the voltage and the residual current. Step 4: Calculate the difference between the real parts of the fundamental and harmonic admittances to ground; Step 5: If the difference between the real parts of the fundamental and harmonic admittances to ground is zero, calculate the insulation resistance to ground of the power supply system under the condition of no incorrect wiring; if the difference between the real parts of the fundamental and harmonic admittances to ground is greater than zero, calculate the insulation resistance to ground of the power supply system under the condition of incorrect wiring. Step 6, if the insulation resistance to ground is lower than the threshold value R set Then the electrical fire monitoring detector will activate after the set delay time.

5. The alarm method for the 220V electrical fire monitoring detector according to claim 4, characterized in that, The third harmonic is taken as the harmonic.

6. The alarm method for the 220V electrical fire monitoring detector according to claim 5, characterized in that, The fundamental admittance to ground is calculated using the following formula. In the formula, and These are the fundamental phasors of the residual current and voltage, respectively. B re.1 B im.1 These are the real and imaginary parts of the fundamental admittance to the ground, respectively.

7. The alarm method for the 220V electrical fire monitoring detector according to claim 6, characterized in that, The harmonic admittance to ground is calculated using the following formula. In the formula, and These are the harmonic phasors of the residual current and voltage, respectively. B re.h B im.h These are the real and imaginary parts of the harmonic admittance to ground, respectively.

8. The alarm method for the 220V electrical fire monitoring detector according to claim 6, characterized in that, If the difference between the real parts of the fundamental and harmonic admittances to ground is zero, then the insulation resistance to ground can be calculated using the following formula: In the formula, R is the insulation resistance to ground.

9. The alarm method of the 220V electrical fire monitoring detector according to claim 7, characterized in that, If the difference between the real parts of the fundamental and harmonic admittances to ground is greater than zero, then the ground insulation resistance can be calculated using the following formula: In the formula, R is the insulation resistance to ground. h is the harmonic order. x is the coefficient corresponding to the condition of incorrect wiring.

10. The alarm method for the 220V electrical fire monitoring detector according to claim 4, characterized in that, The threshold value R is calculated using the following formula. set : In the formula, U is the voltage difference between the live wire and the neutral wire. I r.set The residual current alarm value for the electrical fire detector is greater than or equal to 20mA and less than or equal to 1000mA.

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