• 21/21N = Distance Relay Phase &  Ground
  • 21BU = Backup Distance Relay
  • 25 = Synchronizing Check Relay
  • 27 = Under Voltage
  • 32 = Reverse Power
  • 33Q = Transformer Oil Level
  • 40 = Loss of Excitation.
  • 46 = Negative Phase Sequence Protection
  • 48 = Locked Rotor
  • 49 = Overload
  • 49W = Transformer Winding Temp
  • 49Q = Transformer Oil Temp
  • 50ARC = Instantaneous Overcurrent relay for Arc Protection System
  • 51G = Ground Fault Relay
  • 50/50N = Instantaneous Overcurrent Phase & Ground
  • 51/51N = IDMT. Overcurrent Phase & Ground
  • 59 = Over Voltage
  • 59N = Zero Sequence Overvoltage
  • 63D = Transformer Pressure Relief Device
  • 63TC = Transformer OLTC Protection Relay
  • 67/67N = Directional Overcurrent Relay / Directional Ground Overcurrent
  • 68 = Voltage Relay Block Closing Circuit While De-Energize
  • 79 = Auto Reclose Relay
  • 80T = Transformer Buchholz
  • 81 = Under Frequency Relay
  • 86 = Lockout Function
  • 87B = Bus Differential Relay
  • 87L = Line Current Differential Relay
  • 87T = Transformer Differential Protection Relay
  • 87REF = Differential Restricted Earth Fault Relay
  • 90 = Voltage Regulating Relay
  • 95B = CT Supervision Relay for 87B
  • BF = Circuit Breaker Failure Relay
  • Q = Power Factor Controller
  • DPM = Digital Power Meter
  • DIM = Distributed I/O Module (for CSCS Control)
  • ODF = Optical Distribution frames.
  • SCADA = Supervisory Control and Data acquisition.
  • SA = Substation Automation
  • SAS = Substation Automation System
  • SCMS = Substation Control and Monitoring System
  • SCPS = Substation Control and Protection System
  • PLC = Programmable Logic Control (Device Part) or Power Line Carrier (Telecom Part)
  • RMU = Ring Main Unit.
  • RCC = Remote Control Cubicle / Regional Control Center (SCADA)
  • LCC = Local Control Cubicle
  • NCC = National Control Center
  • BNCC = Backup National Control Center

  • AISC = American Institute of Steel Construction
  • ASCE = American Society of Civil Engineers
  • ANSI = American National Standards Institute
  • ASME = American Society of Mechanical Engineers
  • ASTM = American Society for Testing and Materials
  • AWS = American Welding Society
  • IEEE = Institute of Electrical and Electronics Engineers
  • NEMA = National Electrical Manufacturers Association
  • NFPA = National Fire Protection Association
  • TIS = Thai Industrial Standards
  • EIT = Engineering Institute of Thailand
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