Selection of MCB |
|||
| MCB curve | Type of Load | Residential | Commercial |
| B curve | Resistive Loads | Incandescent lights | Incandescent lights |
| Geyser | Boilers | ||
| Heater | Heaters | ||
| Fan blower heaters | Oil radiator heaters | ||
| Slight Inductive Loads | Florescent Lights | Florescent lights | |
| Small motors (FHP) | High pressure mercury vapor lamps | ||
| C curve | Slight Inductive Loads | Fans & small pumps | Sodium vapor lamps |
| Window / Split ACs | |||
| Lights with ballasts | |||
| Microwave | |||
| Refrigerators | |||
| General household equipment | |||
| D curve | Inductive Loads | Water lifting pumps | Florescent lights |
| UPS | ID & FD fans | ||
| Small control transformers | |||
| Medium size motors | |||
| Refrigerators for commercial use | |||
Type of MCB |
|||||
| MCB Curve | Type of Load | Response | Tripping | Application | Uses |
| B curve | Resistive loads | MCBs react quickly to overloads | 3 To 5 times F.L current (0.04 To 13 Sec) | Domestic & Commercial applications | Suitable for incandescent lighting, socket-outlet, bulbs, heaters etc. Protection of DG sets (since DG sets have low short-circuit capacity) |
| C curve | Slightly inductive loads | MCBs react more slowly, | 5 To 10 times F.L current (0.04 To 5 Sec) | Commercial and Industrial applications
|
Highly Inductive loads such as motors, air conditioners, fluorescent lighting lights, fans & household electrical appliances. |
| D curve | Inductive loads | MCBs are slower | 10 To 20 times F.L current (0.04 To 3 Sec) | Commercial and Industrial applications
|
Very high inrush Inductive currents, Small transformers, welding machines. UPS, small motor & pumps, x-ray machines etc. Note, however, that MCBs with Type K characteristics may provide better protection in some applications of this type. |
| K curve | Inductive loads | MCBs are slower | 8 To 10 times F.L current (0.04 To 3 Sec) | Placing them between the traditional Type C and Type D breakers. In most cases, they allow improved cable protection to be provided in circuits that include motors, capacitors and transformers, where it would previously have been necessary to use Type D devices. This enhanced protection is achieved without increasing the risk of nuisance tripping. | |
Selection of RCCB |
||
| Type of RCCB | Sensitive | Application |
| Type AC | Sensitive to AC Currents Only | Suitable for most domestic and commercial applications. |
| Type A | Sensitive to AC Currents + Pulsating DC Currents (Produced by Rectifier, Thyristors) | Used where there are a lot of “electronic” loads, such as computer equipment or lighting systems with electronic ballasts. |
| Type B | Sensitive to AC Currents + Pulsating DC Currents+ Pure DC Currents | Use in photovoltaic (PV) solar energy installations because the PV panels produce a DC Output and some types of fault can result in the leakage of DC Currents to Earth. |
| Type B+ | Similar to Type B, but respond to ac leakage currents over a wider frequency range | Type B and Type B+ devices can be used wherever a Type AC or Type A device is specified, as they provide the same functionality as these types and more. |
TYPE of RCCB |
|||||
| TYPE | AC Current 50Hz | AC Current 50Hz To 1KHZ | Pulsating Current with DC Component | Multi Frequency Current Generated By 1Phase Inverter | Multi Frequency Current Generated By 3Phase Inverter |
| AC | √ | – | – | – | – |
| A | √ | – | √ | – | – |
| F | √ | – | √ | √ | – |
| B | √ | √ | √ | √ | √ |
| AS | √ | – | √ | – | – |
| BS | √ | √ | √ | √ | √ |
Sensitivity of RCCB |
|
| RCCBs | Application |
| 30 mA | personal protection domestic installation / direct contact |
| 100 mA | limited personal protection / indirect contact |
| 300 mA | building / fire protection |
MCB Enclosure Size |
|||
| MCB Rating (A) | Min. Enclosure Size | ||
| Height | Width | Depth | |
| 100A | 370mm | 216mm | 72mm |
| 125A | 310mm | 180mm | 83mm |
| 225A | 370mm | 217mm | 72mm |
| 250A | 380mm | 195mm | 83.5mm |
| 300A to 400A | 506mm | 381mm | 153mm |
| 600A to 800A | 520mm | 420mm | 200mm |
| 1000A to 1200A | 704mm | 554mm | 173mm |
| 1600A to 3000A | 1016mm | 608mm | 615mm |
Switch Gear Protection |
||||
| Switch Gear | Protection | Isolation | Control | |
| Over Load | Short Circuit | |||
| Fuse | YES | YES | NO | NO |
| Switch | NO | NO | YES | YES |
| Circuit Breaker | YES | YES | YES | YES |
| Contactor | NO | NO | NO | YES |
| Disconnector | NO | NO | YES | NO |
Type of Faults |
|||
| Types of Fault | Reason | Consequences | Protective Device to be used |
| Overload | When Equipment tries to run beyond its rated capacity, or there is a fault in the equipment E.g. When you keep a heater on without any water in it. | It can lead to reduction in life of equipment, Failure of insulation and hence damaging the equipment. | MCB / RCBO |
| Short Circuit | Insulation Failure, Shorting of the Phase to Phase or Phase and Neutral Wires. | High Inrush Current, causing permanent damage to equipment and may lead to a Fire. | MCB |
| Earth Fault | Short circuit between Phase and Earth Conductor. | Can result in Fire due to sparking. | RCBO / RCCB |
| Earth Leakage | Human Body Touching Live Wires. Insulation failure | RCBO / RCCB | |
| Over Voltage | Opening of Neutral Connection increase in Phase To Phase Voltage of 440V, Surge through Lighting or transients, Over voltage from Utility. | Damage to sensitive Electronic Equipment. | OV protection Device |
| Under Voltage | Drop in supply voltage, starting of heavy loads | Damage of Equipment, Flickering of Lights. | UV relays |
MCB Type (BS EN 60898-2) |
|||
| Trip Type | instantaneous Trip (< 0.1 s) |
Load Type | Typical Load |
| B | 3 to 5 In (AC) | Resistive | Heaters, showers, cookers, socket outlets. |
| 4 to 7 In (DC) | |||
| C | 5 to 10 In (AC) | Inductive | Motors, general lighting circuits, power supplies. |
| 7 to 15 In (DC) | |||
| D | 10 to 20 In | High Inductive | Transformers, motors, discharge lighting circuits, computers |
Relays for Transformer |
||||
| Capacity of Transformer | Relays on HV Side | Relays on LV Side | Common Relays | |
| Generator Transformer | 3 Nos Non-Directional O/L Relay | – – | Differential Relay or | |
| 1 no Non-Directional E/L Relay | Overall differential Relay | |||
| and/or standby E/F + REF Relay | Over flux Relay | |||
| Buchholz Relay | ||||
| OLTC Buchholz Relay | ||||
| PRV Relay | ||||
| OT Trip Relay | ||||
| WT Trip Relay | ||||
| 220 /6.6KV Station Transformer | 3 Nos Non-Directional O/L Relay | 3 Nos Non-Directional O/L Relay | Differential Relay | |
| 1 no Non-Directional E/L Relay | Over flux Relay | |||
| and/or standby E/F + REF Relay | Buchholz Relay | |||
| OLTC Buchholz Relay | ||||
| PRV Relay | ||||
| OT Trip Relay | ||||
| WT Trip Relay | ||||
| 132/33/11KV up to 8 MVA | 3 Nos O/L Relay | 2 Nos O/L Relays | Buchholz Relay | |
| 1 no E/L Relay | 1 no E/L Relay | OLTC Buchholz Relay | ||
| PRV Relay | ||||
| OT Trip Relay | ||||
| WT Trip Relay | ||||
| 132/33/11KV up to 8 MVA to 31.5 MVA | 3 Nos O/L Relay | 3 Nos O/L Relay | Differential Relay | |
| 1 no Directional E/L Relay | 1 no E/L Relay | Buchholz Relay | ||
| OLTC Buchholz Relay | ||||
| PRV Relay | ||||
| OT Trip Relay | ||||
| WT Trip Relay | ||||
| 132/33KV, 31.5 MVA & above | 3 Nos O/L Relay | 3 Nos O/L Relay | Differential Relay | |
| 1 no Directional E/L Relay | 1 no E/L Relay | Over flux Relay | ||
| Buchholz Relay | ||||
| OLTC Buchholz Relay | ||||
| PRV Relay | ||||
| OT Trip Relay | ||||
| WT Trip Relay | ||||
| 220/33 KV, 31.5MVA & 50MVA , 220/132KV, 100 MVA | 3 No O/L Relay | 3 Nos O/L Relay | Differential Relay | |
| 1 no Directional E/L Relay | 1 no Directional E/L Relay | Over flux Relay | ||
| Buchholz Relay | ||||
| OLTC Buchholz Relay | ||||
| PRV Relay | ||||
| OT Trip Relay | ||||
| WT Trip Relay | ||||
| 400/220KV 315MVA | 3 Nos Directional O/L Relay | 3 Nos Directional O/L Relay | Differential Relay | |
| 1 no Directional E/L relay. | 1 no Directional E/L relay. | Over flux Relay | ||
| Restricted E/F relay | Restricted E/F relay | Buchholz Relay | ||
| 3 Nos Directional O/L Relay for action | OLTC Buchholz Relay | |||
| PRV Relay | ||||
| OT Trip Relay | ||||
| WT Trip Relay | ||||
| Over Load (Alarm) Relay | ||||
Relays for Transmission & Distribution Lines Protection |
|
| Lines to be protected | Relays to be used |
| 400 KV Transmission Line | Main-I: Non switched or Numerical Distance Scheme |
| Main-II: Non switched or Numerical Distance Scheme | |
| 220 KV Transmission Line | Main-I : Non switched distance scheme (Fed from Bus PTs) |
| Main-II: Switched distance scheme (Fed from line CVTs) | |
| With a changeover facility from bus PT to line CVT and vice-versa. | |
| 132 KV Transmission Line | Main Protection : Switched distance scheme (fed from bus PT). |
| Backup Protection: 3 Nos. directional IDMT O/L Relays and | |
| 1 No. Directional IDMT E/L relay. | |
| 33 KV lines Transmission Line | Non-directional IDMT 3 O/L and 1 E/L relays. |
| 11 KV lines Transmission Line | Non-directional IDMT 2 O/L and 1 E/L relays. |
Selection Chart for 3Ph Induction Motor |
|||||||||||
| Motor Rating,415V,3Ph | Full Load Current (A) | CONTACTOR (A) | OVER LOAD RELAY (A) | BACK UP FUSE (A) | Cable Size | ||||||
| DOL Starter | STAR-DELTA Starter | ||||||||||
| HP | KW | DOL | STAR-DELTA | DOL | STAR-DELTA | Alu. | Cu. | Alu. | Cu. | ||
| 0.75 | 0.52 | 1.6 | 16 | 1.0 To 1.6 | 4 | 1.5 | 1.5 | ||||
| 1 | 0.75 | 2 | 16 | 1.6 To 2.5 | 6 | 1.5 | 1.5 | ||||
| 2 | 1.5 | 3.5 | 16 | 3.0 To 4.5 | 10 | 1.5 | 1.5 | ||||
| 3 | 2.2 | 5 | 16 | 4.5 To 7.0 | 10 | 1.5 | 1.5 | ||||
| 5 | 3.7 | 7.5 | 16 | 6.5 To 10 | 16 | 1.5 | 1.5 | ||||
| 7.5 | 5.5 | 11 | 16 | 16 | 10 To 15 | 4.5 To 7.0 | 16 | 2.5 | 1.5 | 2.5 | 1.5 |
| 10 | 7.5 | 14 | 16 | 16 | 13 To 20 | 6.5 To 10 | 20 | 2.5 | 2.5 | 2.5 | 2.5 |
| 12.5 | 9.3 | 18 | 25 | 16 | 13 To 20 | 10 To 15 | 25 | 4 | 2.5 | 4 | 2.5 |
| 15 | 11 | 21 | 25 | 16 | 15 To 22 | 13 To 20 | 25 | 6 | 4 | 6 | 4 |
| 20 | 15 | 28 | 32 | 18 | 24 To 30 | 13 To 20 | 32 | 10 | 6 | 10 | 6 |
| 25 | 18.5 | 35 | 40 | 25 | 25 To 30 | 15 To 22 | 50 | 16 | 10 | 16 | 10 |
| 30 | 22.5 | 40 | 50 | 25 | 32 To 50 | 24 To 30 | 50 | 16 | 16 | 16 | 16 |
| 35 | 26 | 47 | 70 | 32 | 32 To 50 | 25 To 30 | 63 | 25 | 16 | 25 | 16 |
| 50 | 37 | 66 | 70 | 40 | 57 To 70 | 32 To 50 | 80 | 35 | 25 | 35 | 25 |
| 60 | 45 | 80 | 95 | 50 | 70 To 105 | 32 To 50 | 100 | 50 | 35 | 50 | 35 |
| 75 | 55 | 100 | 125 | 70 | 100 To 150 | 40 To 57 | 100 | 70 | 50 | 70 | 50 |
| 90 | 67.5 | 120 | 140 | 70 | 100 To 150 | 57 To 70 | 160 | 95 | 70 | 95 | 70 |
| 100 | 75 | 135 | 140 | 95 | 100 To 150 | 70 To 105 | 160 | 95 | 70 | 95 | 70 |
| 125 | 90 | 165 | 125 | 70 To 105 | 160 | 150 | 95 | ||||
| 150 | 110 | 200 | 125 | 100 To 150 | 200 | 185 | 150 | ||||
MCB Selection Chart For Motor Protection |
||||||||
| Kw | HP | 1Phase 230V DOL Starting |
3Phase 400V DOL Starting |
3 Phase 400V Star Delta | ||||
| Full Load Current | MCB Selection | Full Load Current | MCB Selection | Full Load Current | MCB Selection | MCB Selection | ||
| 0.18 | 0.24 | 2.8 | 10 | 0.9 | 2 | — | — | — |
| 0.25 | 0.34 | 3.2 | 10 | 1.2 | 2 | — | — | — |
| 0.37 | 0.5 | 3.5 | 10 | 1.2 | 2 | — | — | — |
| 0.55 | 0.74 | 4.8 | 16 | 1.8 | 3 | — | — | — |
| 0.75 | 1.01 | 6.2 | 20 | 2 | 3 | — | — | — |
| 1.1 | 1.47 | 8.7 | 25 | 2.6 | 6 | — | — | — |
| 1.5 | 2.01 | 11.8 | 32 | 3.5 | 10 | — | — | — |
| 2.2 | 2.95 | 17.5 | 50 | 4.4 | 10 | — | — | — |
| 3 | 4.02 | 20 | 63 | 6.3 | 16 | 6.3 | 16 | 10 |
| 3.75 | 5.03 | 24 | 80 | 8.2 | 20 | 8.2 | 20 | 10 |
| 5.5 | 7.37 | 26 | 80 | 11.2 | 25 | 11.2 | 32 | 16 |
| 7.5 | 10.05 | 47 | 125 | 14.4 | 40 | 14.4 | 40 | 25 |
| 10 | 13.4 | — | — | 21 | 50 | 21 | 50 | 32 |
| 15 | 20.11 | — | — | 27 | 100 | 27 | 63 | 40 |
| 18.5 | 24.8 | — | — | 32 | 125 | 32 | — | 50 |
| 22 | 29.49 | — | — | 38 | 125 | 38 | — | 63 |
| 30 | 40.21 | — | — | 51 | 125 | 51 | — | 63 |
RELAY CODE (ANSI) |
|
| Code | Type of Relay |
| 1 | Master Element |
| 2 | Time-delay Starting or Closing Relay |
| 3 | Checking or Interlocking Relay |
| 4 | Master Contactor |
| 5 | Stopping Device |
| 6 | Starting Circuit Breaker |
| 7 | Rate of Change Relay |
| 8 | Control Power Disconnecting Device |
| 9 | Reversing Device |
| 10 | Unit Sequence Switch |
| 11 | Multifunction Device |
| 12 | Over speed protection |
| 13 | Synchronous-Speed Device |
| 14 | Under speed Device |
| 15 | Speed or Frequency Matching Device |
| 16 | Data Communications Device |
| 17 | Shunting or Discharge Switch |
| 18 | Accelerating or Decelerating Device |
| 19 | Starting-to-Running Transition Contactor |
| 20 | Electrically-Operated Valve |
| 21 | Distance protection Relay |
| 21G | Ground Distance |
| 21P | Phase Distance |
| 22 | Equalizer circuit breaker |
| 23 | Temperature control device |
| 24 | Volts per hertz relay |
| 25 | Synchronizing or synchronism-check device |
| 26 | Apparatus thermal device |
| 27 | Under voltage relay |
| 27P | Phase Under voltage |
| 27S | DC under voltage relay |
| 27TN | Third Harmonic Neutral Under voltage |
| 27TN/59N | 100% Stator Earth Fault |
| 27X | Auxiliary Under voltage |
| 27 AUX | Under voltage Auxiliary Input |
| 27/27X | Bus/Line Under voltage |
| 27/50 | Accidental Generator Energization |
| 28 | Flame Detector |
| 29 | Isolating Contactor |
| 30 | Annunciator Relay |
| 31 | Separate Excitation Device |
| 32 | Directional Power Relay |
| 32L | Low Forward Power |
| 32N | Watt metric Zero-Sequence Directional |
| 32P | Directional Power |
| 32R | Reverse Power |
| 33 | Position Switch |
| 34 | Master Sequence Device |
| 35 | Brush-Operating or Slip-ring Short Circuiting Device |
| 36 | Polarity or Polarizing Voltage Device |
| 37 | Undercurrent or Under power Relay |
| 37P | Under power |
| 38 | Bearing Protective Device / Bearing Rtd |
| 39 | Mechanical Condition Monitor |
| 40 | Field Relay / Loss of Excitation |
| 41 | Field Circuit Breaker |
| 42 | Running Circuit Breaker |
| 43 | Manual Transfer or Selector Device |
| 44 | Unit Sequence Starting Relay |
| 45 | Atmospheric Condition Monitor |
| 46 | Reverse-Phase or Phase Balance Current Relay or Stator Current Unbalance |
| 47 | Phase-Sequence or Phase Balance Voltage Relay |
| 48 | Incomplete Sequence Relay / Blocked Rotor |
| 49 | Machine or Transformer Thermal Relay / Thermal Overload |
| 49RTD | RTD Biased Thermal Overload |
| 50 | Instantaneous Overcurrent Relay |
| 50BF | Breaker Failure |
| 50DD | Current Disturbance Detector |
| 50EF | End Fault Protection |
| 50G | Ground Instantaneous Overcurrent |
| 50IG | Isolated Ground Instantaneous Overcurrent |
| 50LR | Acceleration Time |
| 50N | Neutral Instantaneous Overcurrent |
| 50NBF | Neutral Instantaneous Breaker Failure |
| 50P | Phase Instantaneous Overcurrent |
| 50SG | Sensitive Ground Instantaneous Overcurrent |
| 50SP | Split Phase Instantaneous Current |
| 50Q | Negative Sequence Instantaneous Overcurrent |
| 50/27 | Accidental Energization |
| 50/51 | Instantaneous / Time-delay Overcurrent relay |
| 50Ns/51Ns | Sensitive earth-fault protection |
| 50/74 | Ct Trouble |
| 50/87 | Instantaneous Differential |
| 51 | Phase Inverse Time Overcurrent IDMT (Time delay phase overcurrent ) |
| 51G | Ground Inverse Time Overcurrent |
| 51LR | AC inverse time overcurrent (locked rotor) protection relay |
| 51N | Neutral Inverse Time Overcurrent |
| 51P | Phase Time Overcurrent |
| 51R | Locked / Stalled Rotor |
| 51V | Voltage Restrained Time Overcurrent |
| 51Q | Negative Sequence Time Overcurrent |
| 52 | AC circuit breaker |
| 52a | AC circuit breaker position (contact open when circuit breaker open) |
| 52b | AC circuit breaker position (contact closed when circuit breaker open) |
| 53 | Exciter or Dc Generator Relay |
| 54 | Turning Gear Engaging Device |
| 55 | Power Factor Relay |
| 56 | Field Application Relay |
| 57 | Short-Circuiting or Grounding Device |
| 58 | Rectification Failure Relay |
| 59 | Overvoltage Relay |
| 59B | Bank Phase Overvoltage |
| 59P | Phase Overvoltage |
| 59N | Neutral Overvoltage |
| 59NU | Neutral Voltage Unbalance |
| 59P | Phase Overvoltage |
| 59X | Auxiliary Overvoltage |
| 59Q | Negative Sequence Overvoltage |
| 60 | Voltage or current balance relay |
| 60 | Voltage or Current Balance Relay |
| 60N | Neutral Current Unbalance |
| 60P | Phase Current Unbalance |
| 61 | Density Switch or Sensor |
| 62 | Time-Delay Stopping or Opening Relay |
| 63 | Pressure Switch Detector |
| 64 | Ground Protective Relay |
| 64F | Field Ground Protection |
| 64R | Rotor earth fault |
| 64REF | Restricted earth fault differential |
| 64S | Stator earth fault |
| 64S | Sub-harmonic Stator Ground Protection |
| 64TN | 100% Stator Ground |
| 65 | Governor |
| 66 | Notching or Jogging Device/Maximum Starting Rate/Starts Per Hour/Time Between Starts |
| 67 | AC Directional Overcurrent Relay |
| 67G | Ground Directional Overcurrent |
| 67N | Neutral Directional Overcurrent |
| 67Ns | Earth fault directional |
| 67P | Phase Directional Overcurrent |
| 67SG | Sensitive Ground Directional Overcurrent |
| 67Q | Negative Sequence Directional Overcurrent |
| 68 | Blocking Relay / Power Swing Blocking |
| 69 | Permissive Control Device |
| 70 | Rheostat |
| 71 | Liquid Switch |
| 72 | DC Circuit Breaker |
| 73 | Load-Resistor Contactor |
| 74 | Alarm Relay |
| 75 | Position Changing Mechanism |
| 76 | DC Overcurrent Relay |
| 77 | Telemetering Device |
| 78 | Phase Angle Measuring or Out-of-Step Protective Relay |
| 78V | Loss of Mains |
| 79 | AC Reclosing Relay / Auto Reclose |
| 80 | Liquid or Gas Flow Relay |
| 81 | Frequency Relay |
| 81O | Over Frequency |
| 81R | Rate-of-Change Frequency |
| 81U | Under Frequency |
| 82 | DC Reclosing Relay |
| 83 | Automatic Selective Control or Transfer Relay |
| 84 | Operating Mechanism |
| 85 | Pilot Communications, Carrier or Pilot-Wire Relay |
| 86 | Lock-Out Relay, Master Trip Relay |
| 87 | Differential Protective Relay |
| 87B | Bus Differential |
| 87G | Generator Differential |
| 87GT | Generator/Transformer Differential |
| 87L | Segregated Line Current Differential |
| 87LG | Ground Line Current Differential |
| 87M | Motor Differential |
| 87O | Overall Differential |
| 87PC | Phase Comparison |
| 87RGF | Restricted Ground Fault |
| 87S | Stator Differential |
| 87S | Percent Differential |
| 87T | Transformer Differential |
| 87V | Voltage Differential |
| 88 | Auxiliary Motor or Motor Generator |
| 89 | Line Switch |
| 90 | Regulating Device |
| 91 | Voltage Directional Relay |
| 92 | Voltage And Power Directional Relay |
| 93 | Field-Changing Contactor |
| 94 | Tripping or Trip-Free Relay |
| Abbreviation Code | |
| AFD | Arc Flash Detector |
| CLK | Clock or Timing Source |
| CLP | Cold Load Pickup |
| DDR | Dynamic Disturbance Recorder |
| DFR | Digital Fault Recorder |
| DME | Disturbance Monitor Equipment |
| ENV | Environmental data |
| HIZ | High Impedance Fault Detector |
| HMI | Human Machine Interface |
| HST | Historian |
| LGC | Scheme Logic |
| MET | Substation Metering |
| PDC | Phasor Data Concentrator |
| PMU | Phasor Measurement Unit |
| PQM | Power Quality Monitor |
| RIO | Remote Input/output Device |
| RTD | Resistance Temperature Detector |
| RTU | Remote Terminal Unit/Data Concentrator |
| SER | Sequence of Events Recorder |
| TCM | Trip Circuit Monitor |
| LRSS | Local/Remote selector switch |
| VTFF | Vt Fuse Fail |
|
Suffixes Description |
|
| _1 | Positive-Sequence |
| _2 | Negative-Sequence |
| A | Alarm, Auxiliary Power |
| AC | Alternating Current |
| AN | Anode |
| B | Bus, Battery, or Blower |
| BF | Breaker Failure |
| BK | Brake |
| BL | Block (Valve) |
| BP | Bypass |
| BT | Bus Tie |
| BU | Backup |
| C | Capacitor, Condenser, Compensator, Carrier Current, Case or Compressor |
| CA | Cathode |
| CH | Check (Valve) |
| D | Discharge (Valve) |
| DC | Direct Current |
| DCB | Directional Comparison Blocking |
| DCUB | Directional Comparison Unblocking |
| DD | Disturbance Detector |
| DUTT | Direct Under reaching Transfer Trip |
| E | Exciter |
| F | Feeder, Field, Filament, Filter, or Fan |
| G | Ground or Generator |
| GC | Ground Check |
| H | Heater or Housing |
| L | Line or Logic |
| M | Motor or Metering |
| MOC | Mechanism Operated Contact |
| N | Neutral or Network |
| O | Over |
| P | Phase or Pump |
| PC | Phase Comparison |
| POTT | Pott: Permissive Overreaching Transfer Trip |
| PUTT | Putt: Permissive Under reaching Transfer Trip |
| R | Reactor, Rectifier, or Room |
| S | Synchronizing, Secondary, Strainer, Sump, or Suction (Valve) |
| SOTF | Switch On To Fault |
| T | Transformer or Thyratron |
| TD | Time Delay |
| TDC | Time-Delay Closing Contact |
| TDDO | Time Delayed Relay Coil Drop-Out |
| TDO | Time-Delay Opening Contact |
| TDPU | Time Delayed Relay Coil Pickup |
| THD | Total Harmonic Distortion |
| TH | Transformer (High-Voltage Side) |
| TL | Transformer (Low-Voltage Side) |
| TM | Telemeter |
| TT | Transformer (Tertiary-Voltage Side) |
| U | Under or Unit |
| X | Auxiliary |
| Z | Impedance |
Harmonic Effects |
|||||
| Harmonic | R Phase | Y Phase | B Phase | Phase Rotation Sequence | Harmonic Effect |
| Rotation | Rotation | Rotation | |||
| Fundamental | 0° | 120° | 240° | R-Y-B | |
| 3th | 3×0°=0° | 3×120°=360°=0° | 3×240°=720°=0° | No Rotation (In Phase) | Adds Voltages or Currents in Neutral Wire causing Heating |
| 9th | 9×0°=0° | 9×120°=1080°=0° | 9×240°=2160°=0° | ||
| 15th | 15×0°=0° | 15×120°=1800°=0° | 15×240°=3600°=0° | ||
| 21th | 21×0°=0° | 21×120°=2520°=0° | 21×240°=5040°=0° | ||
| 5th | 5×0°=0° | 5×120°=600°=(600-720)=(-120°) | 5×240°=1200°=(1200-2400)=(-240°) | Rotate Against Fundamental (-) (B-Y-R) | Motor Torque Problems |
| 11th | 11×0°=0° | 11×120°=1320°=(1320-1400)=(-120°) | 11×240°=2640°=(2880-2640)=(-240°) | ||
| 17th | 17×0°=0° | 17×120°=2040°=(2040-2160)=(-120°) | 17×240°=4080°=(4320-4080)=(-240°) | ||
| 23th | 23×0°=0° | 23×120°=2760°=(2760-2880)=(-120°) | 23×240°=5520°=(5760-5520)=(-240°) | ||
| 7th | 7×0°=0° | 7×120°=840°=(840-720)=(+120°) | 7×240°=1680°=(1680-1440)=(+240°) | Rotate with Fundamental (+) (R-Y-B) | Excessive Heating Effect |
| 13th | 13×0°=0° | 13×120°=1560°=(1560-1440)=(+120°) | 13×240°=3120°=(3120-2880)=(+240°) | ||
| 19th | 19×0°=0° | 19×120°=2280°=(2280-2160)=(+120°) | 19×240°=4560°=(4560-4320)=(+240°) | ||
| 25th | 25×0°=0° | 25×120°=3000°=(3000-2880)=(+120°) | 25×240°=6000°=(6000-5760)=(+240°) | ||
November 16, 2018 at 10:52PM by Department of EEE, ADBU: https://ift.tt/2AyIRVT
