Global one-stop procurement platform for industrial spare parts.
support01@okmarts.com service@okmarts.com hydraulic@okmarts.com
Display the website inEN
EN
translate to EN
EN
translate to ES
ES
translate to العربية
العربية
All
Mitsubishi
Mitsubishi
Tecumseh
Tecumseh
Copeland
Copeland
Danfoss
Danfoss
Sanyo Denki
Sanyo Denki
Rexroth
Rexroth
All Brands
All Brands
    • a
    • b
    • c
    • d
    • e
    • f
    • g
    • h
    • i
    • j
    • k
    • l
    • m
    • n
    • o
    • p
    • q
    • r
    • s
    • t
    • u
    • v
    • w
    • x
    • y
    • z
    • 3
    • 7

    Relay protection concept and basic requirements

    Relay protection concept and basic requirements Before introducing relay protection, first introduce several working states of the power system (1) Normal working state It means that all the equality and inequality constraints of the power system are satisfied, indicating that the power system meets the load's demand for electrical energy with sufficient electrical power. All live equipment operates within the safe working limit and can provide qualified electrical energy. (2) Abnormal state Some conditions are not met, such as system oscillations. (3) Failure status Short circuit in the system Relay protection is an important measure to detect faults or abnormal conditions that occur in the power system, thereby issuing an alarm signal, or directly isolating and removing the fault part. Fundamental: 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) The current increases. 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) The voltage drops. 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) The 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 is also protection of non-power frequency electrical quantities, such as gas protection 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) Quick action 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 line conductors 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 ability of the protective device to respond to short-circuit faults or abnormal operating conditions within the protected range of electrical equipment or lines. 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; Minimum operating mode of the system: Under the same short-circuit fault condition, the equivalent impedance of the system is the largest, and the short-circuit current through the protection device is the minimum operating mode. The sensitivity of the protection device is measured by the sensitivity coefficient. 4) Reliability Reliability, including safety and reliability, is the most fundamental requirement for relay protection. Safety: It is required that the relay protection does not operate reliably when it is not needed, that is, no misoperation occurs. Reliability: The relay protection is required to operate reliably when a fault that should be operated within the prescribed protection range, that is, not to 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 protection against misoperation and rejection will 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. Common protection: Traditional protection 1. Current protection. (110kv and below) 2. Distance protection. (110kv system) 3. Differential protection. (Transformer, system above 110VK) 4. Longitudinal protection. (System above 220KV) 5. Gas protection. (Transformer non-electricity protection) 6. Zero sequence current protection

    Recent related posts

    Relay protection concept and basic requirements

    06/14/2020

    Relay protection concept and basic requirements

    Before introducing relay protection, first introduce several working states of the power system (1) Normal working state It means that all the equality and inequality constraints of the power system are satisfied, indicating that the power system me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

    Refrigeration compressor motor burnout detection and maintenance methods, quickly collect it!

    06/14/2020

    Refrigeration compressor motor burnout detection and maintenance methods, quickly collect it!

    Refrigeration compressor motor burnout detection and maintenance methods, quickly collect it! What are the methods of detection and maintenance of refrigeration compressor motor burnout? Do your friends know? Let's get to know more with the coldest bacte器2䀀

    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

    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, Rockwell A-B Sensor 802PR-XBAR1-08

    Rockwell A-B Sensor 802PR-XBAR1-08
    US$653.20
    New In stock for sale, CKD Solenoid Valve 4GD310R-C10-E0-3

    CKD Solenoid Valve 4GD310R-C10-E0-3
    US$115.38
    New In stock for sale, Beckhoff Terminal Box Module IP1002-B200

    Beckhoff Terminal Box Module IP1002-B200
    US$626.92
    New In stock for sale, AirTAC Air Cylinder MAC50X175S

    AirTAC Air Cylinder MAC50X175S
    US$112.31
    New In stock for sale, SMC Proportional Valve ITV1030-04F2N3

    SMC Proportional Valve ITV1030-04F2N3
    Contact Us
    New In stock for sale, YORK Air Conditioner YVOH440VNEE

    YORK Air Conditioner YVOH440VNEE
    US$1923.08
    New In stock for sale, Bristol Compressor H82J42BABC

    Bristol Compressor H82J42BABC
    US$774.65
    New In stock for sale, Copeland Compressor ZH125KCE-TFR-568

    Copeland Compressor ZH125KCE-TFR-568
    Contact Us
    New In stock for sale, ATOS Solenoid Valve SDKE-1631/2 10S

    ATOS Solenoid Valve SDKE-1631/2 10S
    Contact Us
    New In stock for sale, Ding Zing Oil Seal UN65*80*9

    Ding Zing Oil Seal UN65*80*9
    US$3.85

    • Welcome to O&Kmarts

      Is there anything we can help?

      Email us
    © eCommerce. 2017-2025. All Rights Reserved
    Press and drag the mouse to start taking a screenshot