Related Info

What is the principle of air conditioning and refrigeration Forecast This year's full-sealed piston compressor will decline Brief introduction Principle and advantages and disadvantages of refrigeration piston compressor Characteristics of rolling rotor compressor Characteristics of scroll compressor

Hematemesis! Detailed explanation of the most comprehensive knowledge of relay protection

Hematemesis! Detailed explanation of the most comprehensive knowledge of relay protection When the power components in the power system (such as generators, lines, etc.) or the power system itself fails and endangers the safe operation of the power system, it can promptly send a warning signal to the operating staff, or directly issue a trip command to the controlled circuit breaker. An automated measure and equipment developed to end these events. The complete set of equipment for realizing this kind of automatic measure is generally called relay protection device. In this special issue, we will introduce the basic principles, basic requirements, basic tasks, classification, common fault analysis and treatment of relay protection in detail. 1. Basic principles The relay protection device must have the function of correctly distinguishing whether the protected element is in a normal operating state or has a fault, a fault in the protection zone or a fault outside the zone. To achieve this function, the protection device needs to be constructed based on the characteristics of the changes in electrical physical quantities before and after the failure of the power system. After the power system fails, the main characteristics of power frequency electrical quantity changes are: 1) Increased current When the short circuit occurs, the current between the electrical equipment and the transmission line between the fault point and the power supply will increase from the load current to greatly exceed the load current. 2) Voltage drop When the phase-to-phase short-circuit and ground-to-ground short-circuit faults occur, the phase-to-phase voltage or phase voltage value of each point of the system drops, and the closer to the short-circuit point, the lower the voltage. 3) The phase angle between current and voltage changes During normal operation, the phase angle between current and voltage is the power factor angle of the load, which is generally about 20°. When the three-phase is short-circuited, the phase angle between current and voltage is determined by the impedance angle of the line, which is generally 60°~ 85°, and when protecting the three-phase short circuit in the reverse direction, the phase angle between current and voltage is 180°+(60°～85°). 4) Measurement impedance changes The measurement impedance is the ratio of the voltage and current at the measurement point (protection installation). During normal operation, the measured impedance is the load impedance; when the metal is short-circuited, the measured impedance changes to the line impedance, the measured impedance decreases significantly after the fault, and the impedance angle increases. When an asymmetric short circuit occurs, a phase sequence component occurs, such as a negative sequence current and a negative sequence voltage component when a two-phase and single-phase ground short circuit occurs; when a single phase is grounded, a negative sequence and zero sequence current and voltage components occur. These components do not appear during normal operation. The use of changes in electrical quantities in the event of a short-circuit fault can constitute relay protection of various principles. In addition, in addition to the above-mentioned protection of power frequency electrical quantities, there are also protections of non-power frequency electrical quantities, such as gas protection. 2. Basic requirements In order to complete its task, the relay protection device must technically meet the four basic requirements of selectivity, snap action, sensitivity and reliability. For the relay protection that acts on the relay trip, four basic requirements should be met at the same time, and for the relay protection device that acts on the signal and only reflects abnormal operating conditions, some of these four basic requirements can be reduced. 1. Selectivity Selectivity means that when a device or line in the power system is short-circuited, its relay protection only removes the faulty device or line from the power system. When the protection of the faulty device or line or the circuit breaker refuses to operate, the phase The protection of the adjacent equipment or line will remove the fault. 2. Quickness Quick action means that the relay protection device should be able to remove the fault as soon as possible, to reduce the time for the equipment and users to run at high current and low voltage, reduce the damage of the equipment, and improve the stability of the system in parallel operation. Generally, the faults that must be quickly removed are: 1) Make the bus voltage of the power plant or important users lower than the effective value (generally 0.7 times the rated voltage). 2) Internal failure of large-capacity generators, transformers and motors. 3) The cross section of the medium and low voltage lines is too small. In order to avoid overheating, the fault of delay removal is not allowed. 4) Failures that may endanger personal safety and cause strong interference to the communication system. The fault removal time includes the protection device and the circuit breaker action time, the action time of the general fast protection is 0.04s ~ 0.08s, the fastest can reach 0.01s ~ 0.04s, the trip time of the general circuit breaker is 0.06s ~ 0.15s, the most Fast can reach 0.02s ~ 0.06s. For relay protection devices that respond to abnormal operating conditions, quick action is generally not required, but signals should be sent with delay in accordance with selective conditions. 3. Sensitivity Sensitivity refers to the response capability of the protection device when a short-circuit fault or abnormal operation occurs within the protected range of the electrical equipment or line. The sensitivity of the protection device is measured by the sensitivity coefficient. Relay protection that can meet the sensitivity requirements. When a fault occurs within the specified range, regardless of the position of the short-circuit point and the type of short-circuit, and whether the short-circuit point has a transition resistance, it can respond to the action correctly, that is, the requirement is not only in the maximum operation of the system Under the mode, the three-phase short circuit can operate reliably, and in the minimum operating mode of the system, it can also operate reliably when the two-phase or single-phase short circuit fault passes through a large transition resistance. Maximum operating mode of the system: When the end of the protected line is short-circuited, the equivalent impedance of the system is the smallest, and the short-circuit current through the protection device is the maximum operating mode. The minimum operating mode of the system: In the case of the same short-circuit fault, the equivalent impedance of the system is the largest, and the short-circuit current through the protection device is the smallest operating mode. 4. Reliability Reliability, including safety and reliability, is the most fundamental requirement for relay protection. 1) Security It is required that the relay protection does not operate reliably when it is not needed, that is, it does not malfunction. 2) Reliability The relay protection is required to operate reliably when a fault that should be operated occurs within the specified protection range, that is, it does not refuse to operate. The malfunction and refusal of relay protection will bring serious harm to the power system. Even for the same power components, with the development of the power grid, the impact of the protection against erroneous operation and refusal will also change. The above four basic requirements are the basis for designing, configuring and maintaining relay protection, and the basis for analyzing and evaluating relay protection. These four basic requirements are interrelated, but there are often contradictions. Therefore, in actual work, it is necessary to dialectically unify according to the structure of the power grid and the nature of users. 3. Basic tasks The basic tasks of power system relay protection are: 1. Automatically, quickly and selectively remove the faulty components from the power system, so as to prevent the faulty components from being further damaged, and ensure that other fault-free parts quickly resume normal operation. 2. Respond to the abnormal operating status of electrical components, and act on the signal according to the conditions of operation and maintenance (if there is no regular staff on duty), so that the staff on duty can deal with it in time, or the device can automatically adjust, or continue to operate Electrical equipment that caused damage or developed into an accident is removed. At this time, it is generally not required to protect the rapid action, but a certain delay is prescribed according to the degree of damage to the power system and its components, so as to avoid unnecessary operation and interference caused by temporary operation fluctuations caused by misoperation. 3. The relay protection device can also cooperate with other automation devices in the power system. When conditions permit, take predetermined measures to shorten the power outage time of the accident and restore the power supply as soon as possible, thereby improving the reliability of the power system operation. 4. Classification Relay protection can be classified in the following 4 ways: 1. Classification according to the protected object There are power line protection and main equipment protection (such as generator, transformer, bus, reactor, capacitor, etc.). 2. Classification by protection function There is short-circuit fault protection and abnormal operation protection. The former can be divided into main protection, backup protection and auxiliary protection; the latter can be divided into overload protection, loss-of-magnetism protection, out-of-step protection, low-frequency protection, non-full-phase operation protection, etc. 3. According to the signal quantity of protection device for comparison and arithmetic processing There are analog protection and digital protection, all electromechanical, rectification, transistor and integrated circuit (operational amplifier) protection devices, which directly reflect the continuous analog quantity of the input signal, are all analog protection; using a microprocessor and The protection devices of microcomputers, they reflect the discrete digital quantity after the analog quantity is sampled and analog-to-digital converted. This is digital protection. 4. Classification according to the protection action principle There are over current protection, low voltage protection, over voltage protection, power direction protection, distance protection, differential protection, longitudinal protection, gas protection, etc. V. Abnormal When it is found that there are abnormalities or defects in the operation of the relay protection, in addition to strengthening monitoring, the protection can cause misoperation and the exit pressure plate is returned, and then contact the relay personnel to deal with. If there are any of the following abnormal conditions, all should exit in time: 1. Mother differential protection When the signals of “bus difference AC disconnection" and “bus difference DC voltage disappear" are issued; when the unbalanced current of the bus difference is not zero; the bus-connected switch without a dedicated bypass bus line is in line operation and the recovery operation is resumed. 2. High frequency protection When the DC power supply disappears; when the regular channel test parameters do not meet the requirements; when the device failure or abnormal channel signal cannot be reset; during the operation of the next-generation line switch. 3. Distance protection When the used PT is out of operation or the three-phase voltage circuit is disconnected; under normal circumstances, the magnetizing current is too large and too small; when the load current exceeds the corresponding period of the protection allowable current. 4. Microcomputer protection The total alarm light is on, and when one of the four protection (high frequency, distance, zero sequence, total weight) alarm lights is on, the corresponding protection is exited; if two CPUs fail, all protection of the device should be exited; all signal lights of the alarm plug-in are not on, If the power indicator is off, it means that the DC disappears. The exit pressure plate should be exited and restored after the DC power is restored; the general alarm light and call light are on, and the CPU × ERR signal is printed. If the CPU is normal, it means that the communication circuit between the protection and the interface CPU If it is abnormal, exit the processing of the CPU inspection switch. If the signal cannot be restored, it means that the CPU has a fatal defect. You should exit the protection exit platen and disconnect the inspection switch processing. 5. Gas protection When adding oil, filtering oil or changing silicone during transformer operation; when submersible pumps or oil coolers (radiators) are put into operation after oil draining and maintenance; when it is necessary to open the venting valve or oil drain plug of the respiratory system or clean the moisture absorber; loaded When someone works on the oil circuit of the regulator. 6. Common failure analysis of relay protection 1. Saturation fault of current mutual inductance The influence of current transformer saturation on power system relay protection is very large. As the terminal load of the power distribution system continues to increase, if a short circuit occurs, the short circuit current will be large. If the system is short-circuited near the terminal equipment area, the current may reach or approach 100 times or more of the current transformer's single rated current. Under normal short-circuit conditions, the larger the current transformer error is, the greater the primary short-circuit current multiplier increases. When the current quick-break protection reduces the sensitivity, it may prevent the action. When the line is short-circuited, the current of the current transformer is saturated, and the secondary current induced again is small or close to zero, which will also cause the timing overcurrent protection device to fail to deploy. When the overcurrent protection of the outlet line of the power distribution system refuses to act and the inlet line protection of the power distribution station is activated, the entire power distribution system will be powered off. 2. Improper selection of switch protection equipment The selection of switch protection equipment is a very important task. Most of the current power distribution has established switch stations in areas with high load density, that is, the power transmission mode of the substation-switch station-distribution transformer. In switch stations that do not implement relay protection automation, we should use load switches or relay device systems combined with them as switch protection devices. Seven, relay protection fault treatment methods and measures 1. Common relay protection fault handling methods 1) Replacement method Use the intact components to replace the components that are determined to be faulty to judge their good or bad, which can quickly narrow the fault search range; 2) Reference method By comparing the relevant technical parameters of normal equipment and abnormal equipment, find the fault point of abnormal equipment. This method is mainly used to check the fault of wiring error, and the test value is quite different from the expected value during the fixed value verification process. When the secondary wiring cannot be properly restored after the transformation and equipment replacement, refer to the wiring of similar equipment. And during the relay setting verification, if it is found that the test value of a certain relay is far away from the setting value, at this time, it is not easy to make a judgment and judge that the relay has bad characteristics. The scale value on the relay should be adjusted. The same meter can be used to measure other similar relays of the same circuit for comparison; 3) Short circuit method Short circuit a section or part of the circuit with a short wire to determine whether the fault exists in the short wire range or elsewhere, so as to determine the fault range. This method is mainly used in the failure of the electromagnetic lock, the open circuit of the current circuit, the switching relay does not operate, and the control of the changeover switch is intact. 2. Measures to ensure the normal operation of the relay protection Reasonable staffing, so that staff scheduling and assistance can be carried out smoothly, clear staff work goals, to ensure the normal operation of power; perfect rules and regulations, according to the characteristics of relay protection, improve and perfect the rules and regulations of the operation and management of protection devices, relay protection equipment Account management, operation and maintenance, accident analysis, periodic verification, defect handling and other files should gradually adopt computer management tracking and inspection, strict assessment, and rewards and punishments; the implementation of state monitoring methods for secondary equipment is easy for comprehensive automated substations. Electrical protection status monitoring.

Recent related posts

Hematemesis! Detailed explanation of the most comprehensive knowledge of relay protection

06/14/2020

Hematemesis! Detailed explanation of the most comprehensive knowledge of relay protection

Hematemesis! Detailed explanation of the most comprehensive knowledge of relay protection When the power components in the power system (such as generators, lines, etc.) or the power system itself fails and endangers the safe operation of the power syste器2䀀ￜ皥䖒皦즠Ʋ煔क़㲈Ʋ䌁皦ᮔǅ༬皧煞क़Ѐ呄ᠾ鹨់༹皧ࠄ00령ꐱ댁珵뛐珵Љ䕄ྦ뤂ᐱ뚜珵ᴴᏩ呄ᠾ퍘ᒥ鹨់ᩄꋔྦ瑉浥巠皱㙲皦抐皱巠皱੨皦柘皱ￜ皥ب巠皱㙲皦忈皱੨皦柘皱즠Ʋǜ勁皦즠ƲبǜV /펔B䌁皦 ᮔǅ'鱤ǆၜ먢䇨珵呈ᠾ뤂ᐱ⿇⬿먲僧ᐱ㥲ᐲ�僬㣢ᐲᠾ랖僧Ѻ識�僬㣢ᐲ臆S㥲ᐲᬄğ識

Characteristics of scroll compressor

06/14/2020

Characteristics of scroll compressor

(1) High efficiency: 90～98%. The suction, compression, and exhaust processes of the scroll compressor are continuous and unidirectional, and the harmful overheating of the suction gas is small; the pressure difference between the adjacent working chamb器2䀀ￜ皥䖒皦즠Ʋ嫜ི㲈Ʋ䌁皦ᮔǅ༬皧嫦ིЀ呄ᠾ鹨់༹皧ࠄ00령ꐱ댁珵뛐珵Љ䕄ྦ뤂ᐱ뚜珵ᴴᏩ呄ᠾ퍘ᒥ鹨់ᩄꋔྦ瑉浥巠皱㙲皦抐皱巠皱੨皦柘皱ￜ皥ب巠皱㙲皦忈皱੨皦柘皱즠Ʋǜ勁皦즠ƲبǜV /펔B䌁皦 ᮔǅ'鱤ǆၜ먢䇨珵呈ᠾ뤂ᐱ⿇⬿먲僧ᐱ㥲ᐲ�僬㣢ᐲᠾ랖僧Ղ識�僬㣢ᐲ臆S㥲ᐲᬄğ識理艏S杴識杴㥲ᐲ

Characteristics of rolling rotor compressor

06/14/2020

Characteristics of rolling rotor compressor

Characteristics of rolling rotor compressor (1) Rolling rotor rotary compressor is a commonly used compressor for room air conditioners (2) Compared with the reciprocating piston compressor, it has the following characteristics:

Brief introduction Principle and advantages and disadvantages of refrigeration piston compressor

06/14/2020

Brief introduction Principle and advantages and disadvantages of refrigeration piston compressor

Brief introduction Principle and advantages and disadvantages of refrigeration piston compressor Principle: Rely on the reciprocating motion of the piston to compress the gas in the cylinder. Usually through the crank connecting rod mechanism, the rotary器2䀀ￜ皥䖒皦즠Ʋ嫜ི㲈Ʋ䌁皦ᮔǅ༬皧嫦ིЀ呄ᠾ鹨់༹皧ࠄ00령ꐱ댁珵뛐珵Љ䕄ྦ뤂ᐱ뚜珵ᴴᏩ呄ᠾ퍘ᒥ鹨់ᩄꋔྦ瑉浥巠皱㙲皦抐皱巠皱੨皦柘皱ￜ皥ب巠皱㙲皦忈皱੨皦柘皱즠Ʋǜ勁皦즠Ʋبǜ

Forecast This year's full-sealed piston compressor will decline

06/14/2020

Forecast This year's full-sealed piston compressor will decline

According to industry online statistics, the production of fully-sealed piston compressors in the first quarter of 2020 was 34.928 million units, down 20.5% year-on-year, and sales were 37.424 million units, down 15.2% year-on-year. As of the end of March器2䀀ￜ皥䖒皦즠Ʋ煔क़㲈Ʋ䌁皦ᮔǅ༬

What is the principle of air conditioning and refrigeration

06/14/2020

What is the principle of air conditioning and refrigeration

With the rapid development of the times, all walks of life are constantly changing. Air-conditioning refrigeration is also not mature from the past, to the current high-tech refrigeration technology, every research and development has great technical cont器2䀀ￜ皥䖒皦즠Ʋ嫜ི㲈Ʋ䌁皦ᮔǅ༬皧嫦ིЀ呄ᠾ鹨់༹皧ࠄ00령ꐱ댁珵뛐珵Љ䕄ྦ뤂ᐱ뚜珵ᴴᏩ呄ᠾ퍘ᒥ鹨់ᩄꋔྦ瑉浥巠皱㙲皦抐皱巠皱੨皦柘皱ￜ皥ب巠皱㙲皦忈皱੨皦柘皱즠Ʋǜ勁皦즠ƲبǜV /펔B䌁皦 ᮔǅ'鱤ǆၜ먢䇨珵呈ᠾ뤂ᐱ⿇⬿먲僧ᐱ㥲ᐲ�僬㣢ᐲᠾ랖僧ֈ識�僬㣢ᐲ臆S㥲ᐲᬄğ識理艏S杴識杴㥲ᐲ

Top 10 common faults in maintenance and debugging of refrigeration systems

06/14/2020

Top 10 common faults in maintenance and debugging of refrigeration systems

What is the effect of pressure and temperature on the refrigeration system Refrigeration system performance testing involves many aspects, of which pressure and temperature are two points that cannot be bypassed. Today we will take a look at the pressure器2䀀ￜ皥䖒皦즠Ʋ煔क़㲈Ʋ䌁皦

What is the effect of pressure and temperature on the refrigeration system

06/14/2020

What is the effect of pressure and temperature on the refrigeration system

What is the effect of pressure and temperature on the refrigeration system Refrigeration system performance testing involves many aspects, of which pressure and temperature are two points that cannot be bypassed. Today we will take a look at the pressure器2䀀ￜ皥䖒皦즠Ʋ嫜ི㲈Ʋ䌁皦

What is the principle of the refrigerator What are the types of refrigerators 【Introduction】

06/14/2020

What is the principle of the refrigerator What are the types of refrigerators 【Introduction】

What is the principle of the refrigerator What are the types of refrigerators 【Introduction】 You may feel strange when it comes to refrigerators. In fact, refrigerators are very common in our lives. A refrigerator is a machine that transfers the heat of 器2䀀ￜ皥䖒皦즠Ʋ煔क़㲈Ʋ䌁皦ᮔǅ༬皧煞क़Ѐ呄ᠾ鹨់༹皧ࠄ00령ꐱ댁珵뛐珵Љ䕄ྦ뤂ᐱ뚜珵ᴴᏩ呄ᠾ퍘ᒥ鹨់ᩄꋔྦ瑉浥巠皱㙲皦抐皱巠皱੨皦柘皱ￜ皥ب巠皱㙲皦忈皱੨皦柘皱즠Ʋǜ勁皦즠ƲبǜV /펔B䌁皦 ᮔǅ'鱤ǆၜ먢䇨珵呈ᠾ뤂ᐱ⿇⬿먲僧ᐱ

Compressor related industry information: in June, more than 30 countries in the world further expanded the scope of unsealing.

06/14/2020

Compressor related industry information: in June, more than 30 countries in the world further expanded the scope of unsealing.

Compressor related industry information: in June, more than 30 countries in the world further expanded the scope of unsealing. After the most difficult period of global multi-national blockade, with the passage of time, many countries have begun to "unse器2䀀ￜ皥䖒皦즠Ʋ嫜ི㲈Ʋ䌁皦ᮔǅ༬皧嫦ིЀ呄ᠾ鹨់༹皧ࠄ00령ꐱ댁珵뛐珵Љ䕄ྦ뤂ᐱ뚜珵ᴴᏩ呄ᠾ퍘ᒥ鹨់ᩄꋔྦ瑉浥巠皱㙲皦抐皱

Customers frequently viewed

New In stock for sale, IWAYA DENKI Water Pump 25CJT0752

IWAYA DENKI Water Pump 25CJT0752

US$2307.69

New In stock for sale, Panasonic Servo Motor MHMF022L1V2M

Panasonic Servo Motor MHMF022L1V2M

US$653.85

New In stock for sale, Honeywell Solenoid Valve VE4025B1045

Honeywell Solenoid Valve VE4025B1045

US$334.62

New In stock for sale, ROTEN Mechanical Seal 8E5K-22-X

ROTEN Mechanical Seal 8E5K-22-X

US$384.62

New In stock for sale, ANSON Vane Pump IVPQ21-25-2-F-R-11CC-10

ANSON Vane Pump IVPQ21-25-2-F-R-11CC-10

Contact Us

New In stock for sale, Ebmpapst Fan DV5214/2NU-805

Ebmpapst Fan DV5214/2NU-805

US$131.72

New In stock for sale, NEW-ERA Air Cylinder EHPE-20C

NEW-ERA Air Cylinder EHPE-20C

US$201.92

New In stock for sale, Ebmpapst Fan 6078 ES

Ebmpapst Fan 6078 ES

Contact Us

New In stock for sale, AirTAC AirPneumatic Cylinder SCJ80X400-50SStandardPneumatic Cylinder(Adjustable stroke type)

AirTAC AirPneumatic Cylinder SCJ80X400-50SStandardPneumatic Cylinder(Adjustable stroke type)

US$130.00

New In stock for sale, Daikin Solenoid Valve KSO-G02-3DC-30-EN

Daikin Solenoid Valve KSO-G02-3DC-30-EN

Contact Us

New In stock for sale, Lenze VFD Frequency Converter ESV371N02YXC

Lenze VFD Frequency Converter ESV371N02YXC

US$2516.20

New In stock for sale, Yokogawa PLC F3RZ81-0N

Yokogawa PLC F3RZ81-0N

Contact Us

New In stock for sale, Copeland Compressor RST45C1E-IAV-199

Copeland Compressor RST45C1E-IAV-199

Contact Us

New In stock for sale, Sanyo Denki Servo Motor P20B10200HCS00

Sanyo Denki Servo Motor P20B10200HCS00

US$3333.53

Welcome to O&Kmarts

Is there anything we can help?

Email us
Feedback

© eCommerce. 2017-2025. All Rights Reserved

Press and drag the mouse to start taking a screenshot