A short note from me today. I’d just like to wish you a very happy New Year on behalf of myself and everyone else at EEP. It’s been a long... Read more
The post Well engineers, it’s about time… Happy New Year! appeared first on EEP - Electrical Engineering Portal.
Directional protection is usually applied to distribution systems that contain multiple power sources, parallel circuits and rings/loops. For such systems it is absolutely necessary to have protection against fault currents... Read more
The post Directional protection relays applied to multiple power sources, parallel circuits and loops appeared first on EEP - Electrical Engineering Portal.
Once oil filling is completed, various pre‐commissioning checks and tests are performed to ensure the healthiness of the transformer (or reactor) prior to its energization. Various electrical tests must be... Read more
The post Transformer pre-commissioning tests and after-receipt checks you MUST perform appeared first on EEP - Electrical Engineering Portal.
|
Comparison of Different Type of Inverter |
|||
| Square Wave | Stepped Sine Wave | Pure Sine Wave | |
| Safety of Appliances | Less | Moderate | High |
| Life of Appliances | Less | Moderate | High |
| Battery Life | Less | Moderate | High |
| Noise Level | High | Moderate | Normal |
| Heat generation | High | Low | Normal |
| Suitability for appliances | No | Not recommended for prolonged use | Yes |
Advantage:
Disadvantage:
Application:
Advantage:
Disadvantage:
Application:
Advantage:
Disadvantage:
Application:
| Comparison of various types of Batteries | |||
| Flat Plate Batteries | Tubular Batteries | Maintenance Free Batteries | |
 |
 |
 |
|
| Cost | Low | High | High |
| Safety | Low | Low | High |
| Efficiency | Low | High | Medium |
| Maintenance | High | Medium | Low |
| Water toppings | High | Medium | Low |
| Releases harmful gases | Yes | Yes | No |
| Ventilation requirement | Yes | Yes | No |
| Scrap Value | High | High | Low |
| Weight | Low | High | Depend on the model. |
| Battery Life Span | Low ( 3 Yrs) | High( 5 Yrs) | Medium (3 to 4 Yrs) |
| Suitable | For Low power cut areas as their designed cycle life is low. | ||
Some of the failure problems associated with capacitor banks are already known, since they happen often. A few of the failures are traceable to the original source and sometimes that... Read more
The post 15 bad situations that may lead to catastrophic explosion of a capacitor bank appeared first on EEP - Electrical Engineering Portal.
The most common voltage sources for power system measurements and protections are either wound transformers (voltage transformers) or capacitive divider devices (capacitor voltage transformers or bushing potential devices). Some new... Read more
The post The Essentials Of Voltage Transformers (Advanced Theory and Practice) appeared first on EEP - Electrical Engineering Portal.
A circuit breaker is both a circuit-breaking device that can make, withstand and break currents whose intensity is at most equal to its rated current (In), and a protection device... Read more
The post The essence of LV circuit breakers – Releases, tripping curves, characteristics and limitation appeared first on EEP - Electrical Engineering Portal.
Connections of private substations to utilities are made more complicated with the addition of private-owned generation facilities. The choice of relays and their placement must be made to ensure adequate... Read more
The post Protection scheme for remote private substation with small generator appeared first on EEP - Electrical Engineering Portal.
The utility-consumer interconnection provides the path for power flow between supplier (utility) and user (consumer). The interconnection may comprise one or more circuits and is assumed to include voltage transformation.... Read more
The post Typical utility-consumer interconnection configurations appeared first on EEP - Electrical Engineering Portal.
Switchgear interlocking is installed to protect both the equipment and the operator from dangerous situations caused by incorrect equipment operation. It can be categorized as operational interlocking and safety, or... Read more
The post The logic behind switchgear interlocking systems in substations appeared first on EEP - Electrical Engineering Portal.
This technical article gives key points about the generator protection. To recover the generator from various kinds of faults, the generator protection scheme of the plant must be designed in such... Read more
The post Protection Of The Power System Heart – The Generator appeared first on EEP - Electrical Engineering Portal.
When the AC mains power supply is available.
When the AC mains power supply is not available.
Advantages:
Disadvantages:
Application:
Advantages:
Disadvantages:
Application:
Advantages:
Disadvantages:
Application:
If the voltage or current in a power circuit are too high to connect measuring instruments or relays directly, coupling is made through transformers. Such measuring transformers are required to... Read more
The post The Essentials Of Current Transformers In Power Circuits (Theory and Practice) appeared first on EEP - Electrical Engineering Portal.
Voltage transformers would have primaries that are either connected directly to the power system (VTs) or across a section of a capacitor string connected between phase and ground (coupling capacitor... Read more
The post Connection schematics of voltage transformers for protective applications appeared first on EEP - Electrical Engineering Portal.
The main purpose of an unbalance detection scheme is to remove a capacitor bank from the system in the event of a failure and fuse operation. This will prevent damaging... Read more
The post 10 unbalance detection schemes for removing failed capacitor bank from the system appeared first on EEP - Electrical Engineering Portal.
Gas insulated substations (GIS) use circuit breakers, disconnect switches and grounding switches, and have various means of indicating their position, either opened or closed, so the same as in AIS.... Read more
The post Main components of a Gas Insulated Substation (GIS) you should know about appeared first on EEP - Electrical Engineering Portal.
The installation of a dedicated substation to serve a plant actually involves an interface between the utility and the plant. Close coordination between utility and plant personnel is essential so... Read more
The post Coordinating study in protection of utility supply line, transformer & plant main bus/feeder appeared first on EEP - Electrical Engineering Portal.
Polarity is very important for the operation of transformers and protection equipment. A clear understanding of polarity is useful in understanding and analyzing of transformer connections and operation as well... Read more
The post What is polarity and why it’s important for transformers and protection relays appeared first on EEP - Electrical Engineering Portal.
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°) | ||