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常用保护和继电器的功能代号IEEE及美国标准ANSIC37.2-1970代号保护英文2 计时器(延时起动或闭合) timer12 过速控制装置over speed13 同步速控制器synchronous speed14 低速控制装置low speed17 旁路或放电开关discharge switch21 距离保护distance21P 相间距离phase distance21N 接地距离ground distance23 温度控制装置temperature24 过励磁保护Volts/Hertz25 检同期装置synchronism－check27 低电压继电器undervoltage30 保护动作指示annunciator32 功率方向元件directional power33 位置开关switch position37 低电流或低功率保护low current/power relay40 失磁保护loss-of-field41 灭磁开关field circuit breaker 43 重合器reclosure cutout switch46 逆相序保护(负序过流) I22 t Neg-Seq Overcurrent47 负序电压保护Neg-Seq voltage49 热保护thermal49M 电动机热保护induction motor thermal 49T 变压器热保护transformer motor thermal 50 电流速断保护instantaneous overcurrent50P 过流保护phase overcurrent50N 零序过流保护neutral overcurrent50G 漏电流保护residual overcurrent50BF 失灵保护Circuit Breaker Failure51 反时限过流保护time overcurrent52 交流断路器AC circuit breaker52CC 合闸线圈circuit breaker closing coil 52TC 跳闸线圈circuit breaker trip coil 55 功率因数继电器power coefficient57 短路或接地保护short circuit/earthing relay59 过电压保护over voltage60 电压或电流平衡保护unbalance current/voltage62 延时继电器time delay63 压力开关pressure switch64 接地检测继电器grounding detection64G 发电机100%定子接地保护100%stator ground67 方向过流保护AC directional overcurrent67N 接地方向过流ground directional overcurrent67P 方向过流phase directional overcurrent67Q 负序方向过流Neg-Seq Dir.Overcurrent 68闭锁blocking振荡闭锁power swing blocking 70 可变电阻rheostat72 直流断路器DC circuit breaker74 告警alarm76 直流过流DC overcurrent78 失步保护loss synchronous79 重合闸reclosing81 频率保护frequency82 直流重合闸继电器DC reclosing85 载波信号或导引线信号carrier or pilot wire receiver relay86 保护闭锁lockout87 差动保护differential87G 发电机差动保护generator differential 87T 变压器差动保护transformer differential 87B 母线差动保护bus bar differential 87V 电压差动voltage differential 89 隔离刀闸line switch91 方向性电压继电器Directional voltage relay92 电压和功率方向继电器Directional voltage/power relay94 跳闸trip101 断路器控制接点circuit breaker control switch101C 断路器合闸close 101T 断路器跳闸trip欢迎您的下载，资料仅供参考！致力为企业和个人提供合同协议，策划案计划书，学习资料等等打造全网一站式需求。
《继电保护功能代码》1 out of2 system ==> 二取一系统1, master element ==> 主要元件，是指控制开关等元件。
它直接地或间接地通过保护继电器、延时继电器等中间元件，使设备投入或撤出运行。
注：本编号通常用于手动操作的元件，若某一电气或机务元件无其它功能编号可表示则也可使用本编号。
10, unit sequence switch ==> 单元顺序开关用于变换顺序，使各个单元从多元设备中投入或撤出工作。
11, multifunction device ==> 多功能元件。
可完成3 个或以上比较重要的功能，而这些功能只能由多个功能元件组合完成。
该元件所有能完成的功能应在图纸、元件功能定义清单或继电器整定单中说明。
注：如果元件仅具有2 个功能，则以这两个功能的编号表示。
12, overspeed device ==> 超速元件通常是直接连接的速度开关，当电机超速时动作。
13, synchronous-speed device ==> 同步速度元件，如离心速度开关、差频继电器、电压继电器、欠电源继电器、或任何形式的元件在接近电机的同步转速时工作。
14, underspeed device ==> 欠速元件，当电机转速降到低于给定值时动作。
15, speed or frequency matching device ==> 速度或频率匹配元件，其功能是调整和保持一台电机或一个系统的速度或频率，使之与另一台电机或系统的速度或频率相等或接近。
16, not used ==> 备用17, shunting or discharge switch ==> 分路或放电开关，用于接通或断开除电阻器外的任何器件，如电机的磁场绕组、电枢绕组、电容器和电抗器的分路。
(本类器件不包括那些在电机起动过程中，有可能被用来作为分路用的器件6 以及类似器件，同时也不包括切换电阻器用的器件)18, accelerating or decelerating device ==> 加速或减速元件，用来合闸使电机引起增速或减速的回路。
ANSI代码保护功能49 过负荷保护Theramal Relay50 电流速断保护 Instantanous Overcurrent Relay50N 中性点速断保护Ground Overcurrent Relay50G 接地速断保护 Ground Overcurrent Relay50S 限时电流速断保护 Time-Overcurrent Relay51 定时限过电流保护Time-Overcurrent Relay51G 反时限过电流保护Ground-Time Overcurrent51N 定时限接地保护Under Restricted Overcurrent Fault Relay50LR 转子堵转保护 Stalled Rotor Protection67P 方向过电流保护AC Directional Overcurrent Relay67N 接地方向过电流保护 Ground Directional Overcurrent Relay67Q 负序方向过电流保护Negtive-Sequency Driectional Overcurrent Relay59 过电压速断保护 Instantanous Overvoltage Relay27 低电压速断保护 Instantanous Voltage Relay27P 低电压保护Under Voltage Relay46 不平衡负载保护 Phase Blance Current Relay32 功率方向保护 Diretional Power Relay25 同步Synchronism Check81 频率Frequency Relay74 报警继电器 Alarm Relay68 联锁 Locking Relay78 失步Out-Of-Step Pretective Relay AST 备自投 Standby Power Auto SwitchT 温度保护 Temperature Protection21 距离保护Distance Relay87 差动保护Differential Protective Relay。
如果是初次接触外方提供的图纸，你可能会被图纸上的各种元件编号搞得不知所云，其实这些编号是有标准的，无论是TOSHIBA还是GE设计的图纸，同样的一个元器件，其编号是不变的，如87就是代表差动继电器，51就是代表过流继电器。
这些编号是依据IEEE用于自动化操作设备的编号标准来编制的，并编入美国C37－2－1970标准中，这种编号系统已用于各种接线图、手册和说明书中。
参照右边的表格，你可以很容易地查到每个编号所代表的元件和功能，让你轻松成为读图高手！。
ANSI 代码保护功能49 过负荷保护50 电流速断保护50N 中性点速断保护50G 接地速断保护50S 限时电流速断保护51定时限过电流保护51G 反时限过电流保护51N 定时限接地保护Relay50LR 转子堵转保护67P 方向过电流保护Relay67N 接地方向过电流保护Relay67Q 负序方向过电流保护Overcurrent RelayTheramal RelayInstantanous Overcurrent RelayGround Overcurrent RelayGround Overcurrent RelayTime-Overcurrent RelayTime-Overcurrent RelayGround- Time OvercurrentUnder Restricted Overcurrent FaultStalled Rotor ProtectionAC Directional OvercurrentGround Directional OvercurrentNegtive-Sequency Driectional59 过电压速断保护27 低电压速断保护27P 低电压保护46 不平衡负载保护32 功率方向保护25 同步81 频率74 报警继电器Instantanous Overvoltage RelayInstantanous Voltage RelayUnder Voltage Relay Phase Blance Current Relay Diretional Power RelaySynchronism CheckFrequency RelayAlarm Relay68 联锁Locking Relay78 失步Out-Of-Step Pretective Relay AST 备自投Standby Power Auto SwitchT 温度保护Temperature Protection21 距离保护Distance RelayDifferential Protective Relay87 差动保护。
A N S I代码保护功能49过负荷保护T h e r a m a l R e l a y50电流速断保护I n s t a n t a n o u s O v e r c u r r e n t R e l a y50N中性点速断保护G r o u n d O v e r c u r r e n t R e l a y50G接地速断保护G r o u n d O v e r c u r r e n t Re l a y50S限时电流速断保护T i m e-O v e r c u r r e n t R e l a y51定时限过电流保护T i m e-Ove r c u r r e n t Re l ay51G反时限过电流保护G r o u n d-T i m e O v e r c u r r e n t51N 定时限接地保护Under Restricted Overcurrent Fault Relay50LR 转子堵转保护 Stalled Rotor Protection67P 方向过电流保护AC Directional Overcurrent Relay 67N 接地方向过电流保护 Ground Directional Overcurrent Relay67Q 负序方向过电流保护Negtive-Sequency Driectional O v e r c u r r e n t R e l a y59过电压速断保护I n s t a nt a no u s Ove r vo l t ag e Re l ay 27 低电压速断保护 Instantanous Voltage Relay 27P 低电压保护U nd e r Vo l t ag e Re l ay 46不平衡负载保护P h a s e B l a n c e C u r r e n t Re l ay32功率方向保护D i r e t i o n a l P o w e r R e l a y 25同步S y n c h r o n i s m C h e c k 81频率F r e q u e n c y R e l a y 74报警继电器A l a r m R e l a y 68联锁L o c k i n g R e l a y78 失步Out-Of-Step Pretective RelayA S T备自投S t a n d b y P o w e r A u t o S w i t c h T温度保护Te m p e r a t u r e P r o t e c t i o n 21距离保护D i s t a n c e R e l a y87差动保护D i f f e r e n t i a l P r o t e c t i v e R e l a y。
The ANSI Standard Device Numbers[1] [2] [3] denote what features a protective device supports (such as a relay or circuit breaker). These types of devices protect electrical systems and components from damage when an unwanted event occurs, such as an electrical fault.[edit] List of Device Numbers1 - Master Element2 - Time Delay Starting or Closing Relay3 - Checking or Interlocking Relay4 - Master Contactor5 - Stopping Device6 - Starting Circuit Breaker7 - Anode Circuit Breaker8 - Control Power Disconnecting Device9 - Reversing Device10 - Unit Sequence Switch11 - Reserved for future application12 - Overspeed Device13 - Synchronous-speed Device14 - Underspeed Device15 - Speed - or Frequency, Matching Device16 - Reserved for future application17 - Shunting or Discharge Switch18 - Accelerating or Decelerating Device19 - Starting to Running Transition Contactor20 - Electrically Operated Valve21 - Distance Relay22 - Equalizer Circuit Breaker23 - Temperature Control Device24 - Over-Excitation Relay25 - Synchronizing or Synchronism-Check Device26 - Apparatus Thermal Device27 - Undervoltage Relay28 - Flame Detector29 - Isolating Contactor30 - Annunciator Relay31 - Separate Excitation Device32 - Directional Power Relay33 - Position Switch34 - Master Sequence Device35 - Brush-Operating or Slip-Ring Short-Circuiting, Device36 - Polarity or Polarizing Voltage Devices37 - Undercurrent or Underpower Relay38 - Bearing Protective Device39 - Mechanical Conduction Monitor40 - Field Relay41 - Field Circuit Breaker42 - Running Circuit Breaker43 - Manual Transfer or Selector Device44 - Unit Sequence Starting Relay45 - Atmospheric Condition Monitor46 - Reverse-phase or Phase-Balance Current Relay47 - Phase-Sequence Voltage Relay48 - Incomplete Sequence Relay49 - Machine or Transformer, Thermal Relay50 - Instantaneous Overcurrent or Rate of Rise, Relay51 - AC Time Overcurrent Relay52 - AC Circuit Breaker53 - Exciter or DC Generator Relay54 - High-Speed DC Circuit Breaker55 - Power Factor Relay56 - Field Application Relay57 - Short-Circuiting or Grounding (Earthing) Device58 - Rectification Failure Relay59 - Overvoltage Relay60 - Voltage or Current Balance Relay61 - Machine Split Phase Current Balance62 - Time-Delay Stopping or Opening Relay63 - Pressure Switch64 - Ground (Earth) Detector Relay65 - Governor66 - Notching or Jogging Device67 - AC Directional Overcurrent Relay68 - Blocking Relay69 - Permissive Control Device70 - Rheostat71 - Level Switch72 - DC Circuit Breaker73 - Load-Resistor Contactor74 - Alarm Relay75 - Position Changing Mechanism76 - DC Overcurrent Relay77 - Pulse Transmitter78 - Phase-Angle Measuring or Out-of-Step Protective Relay79 - AC Reclosing Relay80 - Flow Switch81 - Frequency Relay82 - DC Reclosing Relay83 - Automatic Selective Control or Transfer Relay84 - Operating Mechanism85 - Carrier or Pilot-Wire Receiver Relay86 - Lockout Relay87 - Differential Protective Relay88 - Auxiliary Motor or Motor Generator89 - Line Switch90 - Regulating Device91 - Voltage Directional Relay92 - Voltage and Power Directional Relay93 - Field Changing Contactor94 - Tripping or Trip-Free Relay95 - Reluctance Torque Synchrocheck96 - Autoloading Relay97 - For specific applications where other numbers are not suitable98 - For specific applications where other numbers are not suitable99 - For specific applications where other numbers are not suitableNote 1: A suffix letter may be used with the device number; for example, suffix N is used if the device is connected to a Neutral wire (example: 59N in Siemens Relay is used for protection against Neutral Displacement); and suffixes X,Y,Z are used for auxiliary devices. Similarly, the "G" suffix denotes a "ground", hence a "51G" being a time overcurrent ground relay[4].Note 2: A suffix number may also be used with a device number: numbers are used to distinguish multiple "same" devices in the same equipment such as 51-1, 51-2.Note 3: Device numbers may be combined if the device provides multiple functions, such as the instantaneous/time-delay AC over current relay denoted as 50/51Note 4: For function descriptions, refer to IEEE standards reference library or American Standards C37. For understanding and learning application of these devices, many technical reference books have been published and are are available. These device numbers and their application are typically in the domain of electrical engineers, specifically power generation, transmission or distribution system engineers in regards to safely controlling and protecting users and equipment2 Time-Delay Starting Or Closing Relay8 Control Power Disconnecting Device12 Over-Speed Protection21 Distance Relay24 Over-Excitation (V/Hz)25 Synchronizing Or Synchronism Check Device26 Machine Field Overtemperature27 Undervoltage Device27 Machine Field Undervoltage Device27TN Third Harmonic Neutral Undervoltage30 Annunciator Relay, Multifunction Relays32 Directional Power Device37 Undercurrent Device,37 Machine Field Undercurrent Device38 Bearing Overtemperature40 Loss Of Field Or Excitation Device (Impedance)40Q Loss Of Field Or Excitation Device (Reactive Power)46 Reverse-Phase Or Phase-Balance Current Relay47 Phase-Sequence Voltage Relay48 Incomplete Sequence49 Stator Overtemperature49 Thermal Image Relay50/27 Inadvertent Generator Energization50 Instantaneous Overcurrent Or Rate-Of-Rise Relay51 AC Time Overcurrent Relay50/51 Instantaneous And Time Overcurrent Relay50/51(+) Overcurrent Relay51V Voltage Restraint Overcurrent Device50BF Breaker Failure Relay55 Power Factor Relay56 Field Application Device59 Overvoltage Relay59N Neutral Overvoltage Device60 Voltage Or Current Balance Relay61 Machine Split Phase Current Balance64 Ground Detector Relay64TN 100% Stator Ground Device66 Starts Per Hours67 AC Directional Overcurrent Relay67_2 Negative Sequence Directional Overcurrent68 Blocking Relay69 Circuit Breaker Supervision And Control Device74 Alarm Relay Multifunction Relays76 DC Overcurrent Relay78 Phase Angle MeasuringOr Out-Of-Step Protective Relay79 AC Reclosing Relay81 Frequency Relay81R Rate of Change of Frequency84 Transformer Tap Changer Control Device85 Carrier Or Pilot-Wire Receiver Relay86 Lockout Relay87 Differential Protective Relay87L Line Current Differential Relay L9087T Transformer Differential System87S Machine Stator Differential Protection System 87G Ground Differential or Restricted Ground Fault 87(+) Differential Relay94 Tripping Or Trip-Free Relay Multifunction Relays95 Reluctance Torque Synchrocheck SPM96 Autoloading Relay。
ANSI代码保护功能49 过负荷保护Theramal Relay50 电流速断保护 Instantanous Overcurrent Relay50N 中性点速断保护Ground Overcurrent Relay50G 接地速断保护 Ground Overcurrent Relay50S 限时电流速断保护 Time-Overcurrent Relay51 定时限过电流保护Time-Overcurrent Relay51G 反时限过电流保护Ground-Time Overcurrent51N 定时限接地保护Under Restricted Overcurrent Fault Relay50LR 转子堵转保护 Stalled Rotor Protection67P 方向过电流保护AC Directional Overcurrent Relay67N 接地方向过电流保护 Ground Directional Overcurrent Relay67Q 负序方向过电流保护Negtive-Sequency Driectional Overcurrent Relay 59 过电压速断保护 Instantanous Overvoltage Relay27 低电压速断保护 Instantanous Voltage Relay27P 低电压保护Under Voltage Relay46 不平衡负载保护 Phase Blance Current Relay32 功率方向保护 Diretional Power Relay25 同步Synchronism Check81 频率Frequency Relay74 报警继电器 Alarm Relay68 联锁 Locking Relay78 失步Out-Of-Step Pretective RelayAST 备自投 Standby Power Auto Switch T 温度保护 Temperature Protection 21 距离保护Distance Relay87 差动保护Differential Protective Relay。
ANSI代码保护功能49 过负荷保护 Theramal Relay50 电流速断保护Instantanous Overcurrent Relay50N 中性点速断保护Ground Overcurrent Relay50G 接地速断保护Ground Overcurrent Relay50S 限时电流速断保护Time-Overcurrent Relay51 定时限过电流保护 Time-Overcurrent Relay51G 反时限过电流保护 Ground-Time Overcurrent51N 定时限接地保护 Under Restricted Overcurrent Fault Relay50LR 转子堵转保护Stalled RotorProtection67P 方向过电流保护AC Directional Overcurrent Relay67N 接地方向过电流保护Ground Directional Overcurrent Relay67Q 负序方向过电流保护 Negtive-Sequency Driectional Overcurrent Relay59 过电压速断保护Instantanous Overvoltage Relay27 低电压速断保护Instantanous Voltage Relay27P 低电压保护 Under Voltage Relay46 不平衡负载保护Phase Blance Current Relay32 功率方向保护Diretional Power Relay25 同步 Synchronism Check81 频率 Frequency Relay74 报警继电器Alarm Relay68 联锁Locking Relay78 失步 Out-Of-St ep Pretective RelayAST 备自投Standby Power Auto SwitchT 温度保护Temperature Protection21 距离保护 Distance Relay87 差动保护Differential Protective Relay。
ANSI标准继电保护代码继电保护系统是一种用来检测和保护电力系统设备和电路的自动化系统。
为了确保各种设备和系统能够相互协调和配合，需要一种统一的标准。
ANSI（美国国家标准学会）标准继电保护代码应运而生，它提供了一套规范和指导，确保各种继电保护设备在不同的电力系统中的互操作性。
一、介绍ANSI标准继电保护代码是由美国国家标准学会制定并推广的，它为电力系统中的继电保护装置提供了通用的、跨厂家的标准。
这套代码的目的是使不同厂家的设备能够正常协同工作，提高电力系统的可靠性和安全性。
二、应用ANSI标准继电保护代码广泛应用于电力系统中的各种继电保护设备和装置。
无论是发电厂、变电站还是配电系统，都需要遵循ANSI标准来保证设备之间的兼容性和互操作性。
1. 发电厂发电厂作为电力系统的起点，需要进行继电保护以防止过载、短路等故障。
根据ANSI标准，发电厂所使用的继电保护设备需要满足相应的技术要求和设备功能。
2. 变电站在电力输送过程中，需要经过变电站进行电压的变换和相应的保护。
ANSI标准规定了变电站所使用的继电保护设备的参数范围、功能要求等。
3. 配电系统配电系统是将电力输送到用户终端的最后一环，因此继电保护在这一环节尤为重要。
根据ANSI标准，配电系统中的各个节点需要使用符合标准的继电保护装置来确保电力的安全运输。
三、优点ANSI标准继电保护代码的应用具有以下优点：1. 互操作性：不同厂家的继电保护设备符合ANSI标准，能够正常协同工作，降低了设备之间的兼容性问题。
2. 可靠性：ANSI标准规定了继电保护设备的技术要求和功能要求，确保了系统的可靠性和稳定性。
3. 统一性：ANSI标准提供了一套统一的规范，使得各种继电保护设备都按照相同的标准进行设计和制造。
四、总结继电保护是电力系统中不可或缺的一部分，而ANSI标准继电保护代码则为各种继电保护设备的应用提供了统一的标准。
它确保了继电保护设备的兼容性和互操作性，提升了电力系统的安全性和可靠性。
ANSI Device NumbersFrom Wikipedia, the free encyclopediaJump to: navigation, searchThe ANSI Standard Device Numbers[1] [2] [3] denote what features a protective device supports (such as a relay or circuit breaker). These types of devices protect electrical systems and components from damage when an unwanted event occurs, such as an electrical fault.[edit] List of Device Numbers1 - Master Element2 - Time Delay Starting or Closing Relay3 - Checking or Interlocking Relay4 - Master Contactor5 - Stopping Device6 - Starting Circuit Breaker7 - Anode Circuit Breaker8 - Control Power Disconnecting Device9 - Reversing Device10 - Unit Sequence Switch11 - Reserved for future application12 - Overspeed Device13 - Synchronous-speed Device14 - Underspeed Device15 - Speed - or Frequency, Matching Device16 - Reserved for future application17 - Shunting or Discharge Switch18 - Accelerating or Decelerating Device19 - Starting to Running Transition Contactor20 - Electrically Operated Valve21 - Distance Relay22 - Equalizer Circuit Breaker23 - Temperature Control Device24 - Over-Excitation Relay25 - Synchronizing or Synchronism-Check Device26 - Apparatus Thermal Device27 - Undervoltage Relay28 - Flame Detector29 - Isolating Contactor30 - Annunciator Relay31 - Separate Excitation Device32 - Directional Power Relay33 - Position Switch34 - Master Sequence Device35 - Brush-Operating or Slip-Ring Short-Circuiting, Device36 - Polarity or Polarizing Voltage Devices37 - Undercurrent or Underpower Relay38 - Bearing Protective Device39 - Mechanical Conduction Monitor40 - Field Relay41 - Field Circuit Breaker42 - Running Circuit Breaker43 - Manual Transfer or Selector Device44 - Unit Sequence Starting Relay45 - Atmospheric Condition Monitor46 - Reverse-phase or Phase-Balance Current Relay47 - Phase-Sequence Voltage Relay48 - Incomplete Sequence Relay49 - Machine or Transformer, Thermal Relay50 - Instantaneous Overcurrent or Rate of Rise, Relay51 - AC Time Overcurrent Relay52 - AC Circuit Breaker53 - Exciter or DC Generator Relay54 - High-Speed DC Circuit Breaker55 - Power Factor Relay56 - Field Application Relay57 - Short-Circuiting or Grounding (Earthing) Device58 - Rectification Failure Relay59 - Overvoltage Relay60 - Voltage or Current Balance Relay61 - Machine Split Phase Current Balance62 - Time-Delay Stopping or Opening Relay63 - Pressure Switch64 - Ground (Earth) Detector Relay65 - Governor66 - Notching or Jogging Device67 - AC Directional Overcurrent Relay68 - Blocking Relay69 - Permissive Control Device70 - Rheostat71 - Level Switch72 - DC Circuit Breaker73 - Load-Resistor Contactor74 - Alarm Relay75 - Position Changing Mechanism76 - DC Overcurrent Relay77 - Pulse Transmitter78 - Phase-Angle Measuring or Out-of-Step Protective Relay79 - AC Reclosing Relay80 - Flow Switch81 - Frequency Relay82 - DC Reclosing Relay83 - Automatic Selective Control or Transfer Relay84 - Operating Mechanism85 - Carrier or Pilot-Wire Receiver Relay86 - Lockout Relay87 - Differential Protective Relay88 - Auxiliary Motor or Motor Generator89 - Line Switch90 - Regulating Device91 - Voltage Directional Relay92 - Voltage and Power Directional Relay93 - Field Changing Contactor94 - Tripping or Trip-Free Relay95 - Reluctance Torque Synchrocheck96 - Autoloading Relay97 - For specific applications where other numbers are not suitable98 - For specific applications where other numbers are not suitable99 - For specific applications where other numbers are not suitableNote 1: A suffix letter may be used with the device number; for example, suffix N is used if the device is connected to a Neutral wire (example: 59N in Siemens Relay is used for protection against Neutral Displacement); and suffixes X,Y,Z are used for auxiliary devices. Similarly, the "G" suffix denotes a "ground", hence a "51G" being a time overcurrent ground relay[4].Note 2: A suffix number may also be used with a device number: numbers are used to distinguish multiple "same" devices in the same equipment such as 51-1, 51-2.Note 3: Device numbers may be combined if the device provides multiple functions, such as the instantaneous/time-delay AC over current relay denoted as 50/51Note 4: For function descriptions, refer to IEEE standards reference library or American Standards C37. For understanding and learning application of these devices, many technical reference books have been published and are are available. These device numbers and their application are typically in the domain of electrical engineers, specifically power generation, transmission or distribution system engineers in regards to safely controlling and protecting users and equipment。
