Non-contact online temperature measurement monitoring method for high-voltage switch cabinet

Abstract

The invention provides a non-contact online temperature measurement monitoring method for a high-voltage switch cabinet, and relates to the technical field of electrical safety. Comprising the following four steps: S1, signal acquisition: acquiring the temperature of a high-voltage switch device and the environment temperature by adopting an RFID sensor, acquiring the outgoing current by adopting a current sensor, and acquiring a temperature signal and a current signal by a reader-writer; s2, signal transmission: transmitting the signal parameters obtained by the reader-writer to a protocol conversion device through an RS485 bus, wherein the protocol conversion device is in communication connection with an auxiliary control system comprising a controller; s3, calculating parameters: calculating and comparing the obtained current signal and temperature signal by the controller; and S4, command execution: the controller sends out a signal after calculation and comparison, so that a current compensator compensates current or a temperature compensation device compensates temperature or an alarm system of the auxiliary control system gives a temperature alarm. The method is accurate in temperature measurement, clear in mathematical mechanism for judging the temperature abnormity, capable of effectively judging the reason of the temperature abnormity in time and capable of automatically recovering and removing part of abnormity.

Description

Technical Field

[0001] The invention relates to the technical field of electrical safety, and specifically discloses a non-contact online temperature measurement and monitoring method for a high-voltage switch cabinet. Background Art

[0002] There are three main factors that cause heating of the switchgear in the high-voltage switchgear:

[0003] 1. Resistance effect: The Joule heating effect caused by current passing through a conductor. When the resistance of the conductor increases, the current passing through the conductor will generate more heat, causing the conductor to heat up, especially the overlap of the conductor or the contact of the switch.

[0004] 2. Environmental factors: Ambient temperature and ventilation conditions have a significant impact on conductor heating. The higher the ambient temperature, the easier it is for the conductor to heat up. Poor ventilation conditions will also aggravate the heating of the conductor.

[0005] 3. Overload problem: When a conductor is overloaded, that is, the current flowing through the conductor exceeds its design capacity or rated current, the flow speed of electrons inside the conductor increases, and the frequency of collisions between electrons and conductor atoms increases, causing the conductor to generate more heat.

[0006] Continuous temperature rise or heating of the switchgear conductor will bring about the following series of problems:

[0007] 1. The high-voltage switchgear is a closed space, so if the conductor heats up for a long time, the ambient temperature in the closed space will become higher. In the long run, the mechanical strength of the metal material will decrease and the insulation material will age, endangering the safe operation of the electrical equipment;

[0008] 2. High temperature may cause poor contact or damage of electrical components, which may lead to circuit short circuit accidents, resulting in power outages and affecting power supply reliability. At the same time, it may also affect other auxiliary equipment and affect the stability of the entire power supply and distribution system;

[0009] 3. Excessive temperature inside the high-voltage switch cabinet may cause electrical accidents such as electric shock, explosion, fire, etc. It may also burn people and release toxic gases, posing a threat to the personal safety of workers.

[0010] Through extensive searches, in order to effectively monitor the internal temperature of the high-voltage switchgear in real time to solve the above problems, the existing technology includes but is not limited to the following methods for innovation and improvement:

[0011] 1. Choice of temperature measurement method: Traditional temperature measurement methods include temperature indicator tag method, infrared temperature measurement method, optical fiber temperature measurement method, CT temperature measurement method, etc., but these temperature measurement methods have obvious shortcomings and are no longer favored by the market. The more mainstream method is surface acoustic wave temperature measurement, which is a wireless passive temperature measurement method. For example, the author Li Chao's journal paper "Research on Passive Wireless Temperature Online Monitoring System of Switch Cabinet", the author Su Yuanbin's journal paper "Research on Passive Wireless Temperature Monitoring System of High-voltage Switch Cabinet", and the author Guo Yuan's master's thesis "Research on Key Technologies of Passive Wireless Temperature Measurement of Power High-voltage Switch Cabinet" all adopted this temperature measurement method; but this method also has obvious defects, that is, it is greatly affected by the ambient temperature and there are certain problems with the measurement accuracy.

[0012] 2. Detect the cabinet surface temperature: In the authorized invention patent "A temperature detection method and system based on the temperature field distribution of high-voltage switch cabinet (authorization number: CN110793647B)", the partial least squares regression method is used to accurately estimate the temperature of each room inside the switch cabinet based on the temperature field distribution of the outer surface of the switch cabinet, the ambient temperature and humidity, the load current and other influencing factors. Similarly, in the authorized invention patent "A method for judging the fault type by the change of the surface temperature of the high-voltage switch cabinet (authorization number: CN111121971B)", the cabinet surface temperature data of the high-voltage switch cabinet is obtained based on the infrared temperature measurement equipment, and the temperature inside the switch cabinet is monitored in combination with the algorithm.

[0013] 3. Optimize the temperature monitoring prediction algorithm: Establish a temperature prediction model in the authorized invention patent "High-voltage switchgear temperature monitoring system and monitoring method (authorization number: CN110726494B)", and use the traditional gray prediction algorithm to improve the accuracy of temperature monitoring and reduce the false alarm rate.

[0014] Although the prior art provides some effective methods for measuring and detecting the temperature in high-voltage switch cabinets, and contributes to the development of this technology, the inventors believe that there are still two deficiencies that deserve to be explored and improved:

[0015] 1. The prior art does not integrate the surface temperature of the switch device in the switch cabinet with the conductor current and the ambient temperature through mathematical mechanisms. Therefore, when the temperature of the high-voltage switch device is detected, the detected temperature can only represent the temperature value of the surface of the high-voltage switch device, and the real influencing factors behind the temperature change cannot be obtained, so no specific implementation solution can be given.

[0016] 2. In the prior art, when a temperature anomaly is detected, an alarm is triggered, which in turn guides the on-site engineer to check and repair the system. However, in fact, some temperature anomalies caused by certain reasons can be automatically recovered through some strategies, and the prior art does not provide a self-recovery method based on temperature monitoring. Therefore, the prior art solution cannot reduce the workload of on-site engineers, and the monitoring and processing efficiency is low, wasting human resources.

[0017] Based on the above analysis, combined with the on-site work experience of the inventor's team and detailed discussion of research results, this application proposes a non-contact online temperature measurement and monitoring method for high-voltage switchgear. Summary of the invention

[0018] In order to solve the above problems that the type of temperature anomaly in the high-voltage switch cabinet cannot be accurately and effectively judged and repaired, and there is no mathematical theoretical basis for reference if there is no temperature anomaly, the technical solution provided by the non-contact online temperature measurement and monitoring method of the high-voltage switch cabinet of the present invention is as follows:

[0019] The online temperature measurement and monitoring method comprises the following steps:

[0020] S1. Signal collection: Use RFID sensor to collect the temperature of high-voltage switchgear and ambient temperature. At the same time, use current sensor to obtain outgoing line current, and reader / writer to obtain temperature signal and current signal;

[0021] S2. Transmitting signals: The signal parameters obtained by the reader are transmitted to the protocol conversion device through the RS485 bus, and the protocol conversion device is connected to the auxiliary control system including the controller;

[0022] S3. Calculation parameters: The controller calculates and compares the acquired current signal and temperature signal;

[0023] S4. Execute command: After calculation and comparison by the controller, a signal is sent to let the current compensator compensate the current, or let the temperature compensation device compensate the temperature, or let the alarm system of the auxiliary control system issue a temperature alarm.

[0024] Furthermore, the RFID sensor includes a thermistor, a transceiver antenna, an AC / DC circuit, a demodulation circuit, a logic control circuit, a memory and a modulation circuit; the reader includes a transceiver antenna, a frequency generator, a phase-locked loop, a modulation circuit, a microprocessor, a memory, a demodulation circuit and a peripheral interface.

[0025] Furthermore, there are two groups of RFID sensors in the same high-voltage switch cabinet, one group of 12, which are installed on the high-voltage switch device, including the busbar points in the three phases, the upper contact arm points of the circuit breaker, the lower contact arm points of the circuit breaker and the outgoing line points, and the other group of 2, which are installed on both sides of the inner wall of the high-voltage switch cabinet.

[0026] Furthermore, the temperature rise calculation formula of the high-voltage switchgear in the high-voltage switch cabinet is as follows:

[0027] (2) Let the heat generated by the conductor be Q1 and the heat dissipated be Q2. According to Joule’s law and Newton’s law of cooling, we have

[0028]

[0029] In the above formula, I n is the rated phase current, R is the resistance, ρ is the resistivity, α is the resistance temperature coefficient, τ0 is the ambient temperature in the high-voltage switch cabinet, L is the conductor length, S is the conductor cross-sectional area; K is the comprehensive heat dissipation coefficient, A is the surface area of ​​the conductor, T is the temperature generated by the conductor radiation at the rated phase current, t is the time, and M is the circumference of the conductor cross section;

[0030] (2) When thermal equilibrium is reached, that is, Q1 = Q2, the temperature generated by conductor radiation at rated phase current is

[0031]

[0032] (3) When the phase current changes and / or the ambient temperature changes, the temperature rise expression can be obtained as

[0033]

[0034] In the above formula, ΔT is the temperature rise, I s is the load phase current at a certain moment, and τ1 is the ambient temperature inside the high-voltage switch cabinet at a certain moment.

[0035] Furthermore, the criterion for executing the command in step S4 is:

[0036] (1) When the phase currents and temperature rises of the three corresponding temperature measurement points are the same, there is no action;

[0037] (2) When the three-phase currents are different, the compensation current command is executed. When the compensation is completed, that is, the three-phase currents are the same, if the temperature rises of the three corresponding temperature measuring points are the same, the process ends. When the temperature rises of the corresponding temperature measuring points are different, the temperature alarm command is executed.

[0038] Furthermore, the criterion for executing the command in step S4 is:

[0039] (1) When the temperatures of the four temperature measuring points of the same phase are normal, there is no action;

[0040] (2) When the temperature rise of one of the four temperature measuring points in the same phase is significantly higher than that of the other three temperature measuring points, the temperature alarm command is executed.

[0041] Furthermore, the criterion for executing the command in step S4 also includes:

[0042] When the ambient temperature in the high-voltage cabinet is higher than the threshold, if the temperature rise of all temperature measuring points does not exceed the threshold, the compensation temperature command is executed to cool down; if the temperature rise of one of the temperature measuring points exceeds the threshold, the temperature alarm command is executed.

[0043] Further, the temperature compensation device includes an exhaust fan installed in the high-voltage switch cabinet and an air conditioning system installed in the power distribution room;

[0044] The temperature compensation steps are: increase the exhaust fan power until the ambient temperature is lower than the threshold. If the ambient temperature cannot be lower than the threshold, increase the air conditioning system power until the ambient temperature is lower than the threshold. If the ambient temperature still cannot be lower than the threshold, execute the temperature alarm command.

[0045] Furthermore, the temperature alarm information of the alarm system is displayed on the central control room display screen or the engineer's mobile phone screen.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] 1. The present invention provides a non-contact online temperature measurement and monitoring method for high-voltage switch cabinets, which derives the mathematical mechanism and relationship between the temperature rise of the high-voltage switch device, the load phase current and the ambient temperature inside the high-voltage switch cabinet, and provides a theoretical basis for accurate and efficient judgment of temperature anomalies in temperature monitoring of high-voltage switch cabinets.

[0048] 2. The present invention provides a non-contact online temperature measurement and monitoring method for a high-voltage switch cabinet. The high-voltage switch device combines the relationship between temperature rise, load phase current and the ambient temperature inside the high-voltage switch cabinet, compares the temperature relationship between the three corresponding temperature measurement points in the three phases, and judges whether the temperature rise is caused by three-phase imbalance or overload when there is current. If so, the current is compensated. If the three-phase current is balanced and the temperature rise exists, the temperature alarm instruction is executed. At the same time, the temperature rise changes of the four temperature measurement points of the same phase busbar point, the upper contact arm point of the circuit breaker, the lower contact arm point of the circuit breaker and the outlet point can also be compared. If there is an abnormal temperature rise point, the alarm instruction is executed. In addition, the two criteria can be combined to judge the cause of the abnormal temperature rise. It can be seen that the logic of judging temperature anomalies in this application is clear and clear, not only can it judge temperature anomalies more efficiently and accurately and alarm, but also for the temperature that can be restored to normal by self-repair, there is no need to alarm and notify engineers for maintenance, which greatly improves the efficiency of work monitoring and maintenance.

[0049] 3. The present invention provides a non-contact online temperature measurement and monitoring method for high-voltage switch cabinets, which also combines the ambient temperature as the basis for judging the abnormal temperature of the high-voltage switch device. The entire substation is centered on the temperature monitoring of the high-voltage switch device. When the temperature of the high-voltage switch device changes significantly due to changes in the ambient temperature, the exhaust volume of the high-voltage switch cabinet exhaust fan or the power of the indoor air-conditioning system can be automatically changed to reduce the natural temperature of the environment and eliminate the abnormal temperature of the high-voltage switch device. It can be seen that the ambient temperature control of the present application is adjusted around the temperature of the high-voltage switch device, and adopts the "first principle" thinking, which greatly satisfies and solves the source problem of substation safety.

[0050] 4. The present invention provides a non-contact online temperature measurement and monitoring method for a high-voltage switch cabinet. Data collection is performed based on an RFID sensor, which is a non-contact wireless passive sensor. Its electric energy is provided by the radio frequency signal of a reader / writer. It has strong adaptability to the environment and has the characteristics of small measurement error, easy installation, and long service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 It is a schematic diagram of the communication structure of the present invention. DETAILED DESCRIPTION

[0052] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0053] A non-contact online temperature measurement and monitoring method for a high-voltage switch cabinet comprises the following four steps:

[0054] S1. Collecting signals: RFID sensors are used to collect the temperature of the high-voltage switch device and the ambient temperature. At the same time, current sensors are used to obtain the outgoing line current (load phase current), and readers and writers obtain temperature signals and current signals. RFID sensors are non-contact wireless passive temperature detection sensors, also known as RFID tags. Each RFID sensor has an independent and unique address, with a temperature measurement accuracy of ±1°C and a temperature resolution of 0.1°C.

[0055] S2. Transmit signal: The signal parameters acquired by the reader are transmitted to the protocol conversion device through the RS485 bus, and the protocol conversion device is communicated with the auxiliary control system including the controller.

[0056] S3. Calculation parameters: The controller calculates and compares the acquired current signal and temperature signal.

[0057] S4. Execute command: After calculation and comparison by the controller, a signal is sent to let the current compensator compensate the current, or let the temperature compensation device compensate the temperature, or let the alarm system of the auxiliary control system issue a temperature alarm.

[0058] The preferred solution is that the RFID sensor includes a thermistor, a transceiver antenna, an AC / DC circuit, a demodulation circuit, a logic control circuit, a memory and a modulation circuit; the reader includes a transceiver antenna, a frequency generator, a phase-locked loop, a modulation circuit, a microprocessor, a memory, a demodulation circuit and a peripheral interface.

[0059] The preferred solution is that there are two groups of RFID sensors in the same high-voltage switch cabinet, one group of 12 sensors are installed on the high-voltage switch device, including the busbar points in the three phases, the upper contact arm points of the circuit breaker, the lower contact arm points of the circuit breaker and the outgoing line points, and the other group of 2 sensors are installed on both sides of the inner wall of the high-voltage switch cabinet.

[0060] The preferred solution is that the temperature rise calculation formula of the high-voltage switchgear in the high-voltage switch cabinet is as follows:

[0061] (1) Let the heat generated by the conductor be Q1 and the heat dissipated be Q2. According to Joule’s law and Newton’s law of cooling, we have

[0062]

[0063] In the above formula, I n is the rated phase current, R is the resistance, ρ is the resistivity, α is the resistance temperature coefficient, τ0 is the ambient temperature inside the high-voltage switch cabinet (the ambient temperature is initially the same as the surface temperature of the high-voltage switchgear), L is the conductor length, S is the conductor cross-sectional area; K is the comprehensive heat dissipation coefficient, A is the surface area of ​​the conductor, T is the temperature generated by the conductor radiation at the rated phase current, t is the time, and M is the circumference of the conductor cross-section.

[0064] (2) When thermal equilibrium is reached, that is, Q1 = Q2, the temperature generated by conductor radiation at rated phase current is

[0065]

[0066] (3) When the phase current changes and / or the ambient temperature changes, the temperature rise expression can be obtained as

[0067]

[0068] In the above formula, ΔT is the temperature rise, I sis the load phase current at a certain moment, and τ1 is the ambient temperature in the high-voltage switch cabinet at a certain moment. As long as the ambient temperature is constant and the load is running at the rated current, there is no temperature rise under normal circumstances in principle. In engineering practice, the load current and ambient temperature must be dynamic, so the temperature rise will definitely change. However, as long as it changes within a reasonable range, it will not cause a temperature alarm. The corresponding command will only be executed when the temperature rise is abnormal and unreasonable.

[0069] In the preferred embodiment, the criterion for executing the command in step S4 is:

[0070] (1) When the phase currents and temperature rises of the three corresponding temperature measurement points (such as the three outgoing line temperature measurement points in the three phases) are the same, there is no action;

[0071] (2) When the three-phase currents are different, the compensation current command is executed. When the compensation is completed, that is, the three-phase currents are the same, if the temperature rises of the three corresponding temperature measuring points are the same, the process ends. When the temperature rises of the corresponding temperature measuring points are different, the temperature alarm command is executed.

[0072] In the preferred embodiment, the criterion for executing the command in step S4 is:

[0073] (1) When the temperatures of the four temperature measuring points of the same phase are normal, there is no action;

[0074] (2) When the temperature rise of one of the four temperature measuring points in the same phase is significantly higher than that of the other three temperature measuring points, the temperature alarm command is executed.

[0075] In a preferred embodiment, the criterion for executing the command in step S4 further includes:

[0076] When the ambient temperature in the high-voltage cabinet is higher than the threshold (ambient temperature threshold), if the temperature rise of all temperature measuring points does not exceed the threshold (temperature rise threshold), the compensation temperature command is executed to cool down; if the temperature rise of one of the temperature measuring points exceeds the threshold, the temperature alarm command is executed.

[0077] The standards for the temperature and temperature rise threshold of internal devices of high-voltage switchgear in my country are shown in the table below.

[0078]

[0079] Preferably, the temperature compensation device includes an exhaust fan installed in the high-voltage switch cabinet and an air conditioning system installed in the power distribution room;

[0080] The temperature compensation steps are: increase the exhaust fan power in the high-voltage switch cabinet until the ambient temperature is lower than the threshold (ambient temperature threshold); if the ambient temperature cannot be lower than the threshold, increase the air conditioning system power until the ambient temperature is lower than the threshold; if the ambient temperature still cannot be lower than the threshold, execute the temperature alarm command.

[0081] The preferred solution is that the temperature alarm information of the alarm system is displayed on the central control room display screen or the engineer's mobile phone screen.

[0082] The preferred embodiment of the present invention comprises a plurality of high-voltage switch cabinets, the temperature and current signals in each switch cabinet communicate with a reader / writer, and each reader / writer communicates with a protocol conversion device, thereby forming temperature detection and monitoring of the overall high-voltage switch cabinet of the substation to ensure the safety of the substation.

[0083] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A non-contact online temperature measurement and monitoring method for a high-voltage switch cabinet, characterized in that: It includes the following four steps: S1. Signal collection: Use RFID sensor to collect the temperature of high-voltage switchgear and ambient temperature. At the same time, use current sensor to obtain outgoing line current, and reader / writer to obtain temperature signal and current signal; S2. Transmitting signals: The signal parameters obtained by the reader are transmitted to the protocol conversion device through the RS485 bus, and the protocol conversion device is connected to the auxiliary control system including the controller; S3. Calculation parameters: The controller calculates and compares the acquired current signal and temperature signal; S4. Execute command: After calculation and comparison by the controller, a signal is sent to let the current compensator compensate the current, or let the temperature compensation device compensate the temperature, or let the alarm system of the auxiliary control system issue a temperature alarm.

2. The non-contact online temperature measurement and monitoring method for high-voltage switch cabinet according to claim 1 is characterized in that: The RFID sensor includes a thermistor, a transceiver antenna, an AC / DC circuit, a demodulation circuit, a logic control circuit, a memory and a modulation circuit; the reader includes a transceiver antenna, a frequency generator, a phase-locked loop, a modulation circuit, a microprocessor, a memory, a demodulation circuit and a peripheral interface.

3. The non-contact online temperature measurement and monitoring method for high-voltage switch cabinet according to claim 1 is characterized in that: There are two groups of RFID sensors in the same high-voltage switch cabinet. One group has 12 sensors, which are installed on the high-voltage switch device, including the busbar points, upper contact arm points, lower contact arm points and outgoing line points of the three-phase circuit breaker. The other group has 2 sensors, which are installed on both sides of the inner wall of the high-voltage switch cabinet.

4. The non-contact online temperature measurement and monitoring method for high-voltage switch cabinet according to claim 3 is characterized in that: The temperature rise calculation formula of the high-voltage switchgear in the high-voltage switch cabinet is as follows: (1) Let the heat generated by the conductor be Q1 and the heat dissipated be Q2. According to Joule’s law and Newton’s law of cooling, we have In the above formula, I n is the rated phase current, R is the resistance, ρ is the resistivity, α is the resistance temperature coefficient, τ0 is the ambient temperature in the high-voltage switch cabinet, L is the conductor length, S is the conductor cross-sectional area; K is the comprehensive heat dissipation coefficient, A is the surface area of ​​the conductor, T is the temperature generated by the conductor radiation at the rated phase current, t is the time, and M is the circumference of the conductor cross section; (2) When thermal equilibrium is reached, that is, Q1 = Q2, the temperature generated by conductor radiation at rated phase current is (3) When the phase current changes and / or the ambient temperature changes, the temperature rise expression can be obtained as In the above formula, ΔT is the temperature rise, I s is the load phase current at a certain moment, and τ1 is the ambient temperature inside the high-voltage switch cabinet at a certain moment.

5. The non-contact online temperature measurement and monitoring method for high-voltage switch cabinet according to claim 4 is characterized in that: The criterion for executing the command in step S4 is: (1) When the phase currents and temperature rises of the three corresponding temperature measurement points are the same, there is no action; (2) When the three-phase currents are different, the compensation current command is executed. When the compensation is completed, that is, the three-phase currents are the same, if the temperature rises of the three corresponding temperature measuring points are the same, the process ends. When the temperature rises of the corresponding temperature measuring points are different, the temperature alarm command is executed.

6. The non-contact online temperature measurement and monitoring method for high-voltage switch cabinet according to claim 4 is characterized in that: The criterion for executing the command in step S4 is: (1) When the temperatures of the four temperature measuring points of the same phase are normal, there is no action; (2) When the temperature rise of one of the four temperature measuring points in the same phase is significantly higher than that of the other three temperature measuring points, the temperature alarm command is executed.

7. The non-contact online temperature measurement and monitoring method for a high-voltage switch cabinet according to any one of claims 5 or 6, characterized in that: The criterion for executing the command in step S4 also includes: When the ambient temperature in the high-voltage cabinet is higher than the threshold, if the temperature rise of all temperature measuring points does not exceed the threshold, the compensation temperature command is executed to cool down; if the temperature rise of one of the temperature measuring points exceeds the threshold, the temperature alarm command is executed.

8. The non-contact online temperature measurement and monitoring method for high-voltage switch cabinet according to claim 7 is characterized in that: The temperature compensation device includes an exhaust fan installed in the high-voltage switch cabinet and an air conditioning system installed in the power distribution room; The temperature compensation steps are: increase the exhaust fan power until the ambient temperature is lower than the threshold. If the ambient temperature cannot be lower than the threshold, increase the air conditioning system power until the ambient temperature is lower than the threshold. If the ambient temperature still cannot be lower than the threshold, execute the temperature alarm command.

9. The non-contact online temperature measurement and monitoring method for high-voltage switch cabinet according to claim 1 is characterized in that: The temperature alarm information of the alarm system is displayed on the central control room display screen or the engineer’s mobile phone screen.

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