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Internship Report

  1. 1. Internship Training Report 132kv Grid Substation Kamalabad, P&I IESCO by Muhammad Usman Rafiq F-4068 A Report submitted to the Department of P&I, IESCO Islamabad in partial fulfillment of the requirements for the internship of one month for BACHELOR OF SCIENCE IN ELECTRICAL ENGINEERING P&I, IESCO Islamabad, 46000 Pakistan <August, 2016>
  2. 2. ii Copyright © 2014 by APCOMS All rights reserved. Reproduction in whole or in part in any form requires the prior written permission of Muhammad Usman Rafiq or designated representative.
  3. 3. DEDICATION Thanks to almighty Allah, who makes me, grows me and produces such abilities in me so I become able to produce such report. I want to dedicate “My Little Work” to my parents and teachers. Parents and teachers have a great role in my life. Both the personalities exert a lot of efforts on me which make me eligible for making this report.
  4. 4. C E R T I F I C A T E O F A P P R O V A L It is certified that the work of report titled “132K Internship Training Report 132kv Grid Substation Kamalabad, P&I IESCO” is carried out by Muhammad Usman Rafiq, Roll. No F-4068, under the supervision of IESCO, at Islamabad and Rawalpindi. It is fully adequate, in scope and in quality, as a report for the internship of one month. Supervisor: ------------------------
  5. 5. ACKNOWLEDGMENT IESCO has been the ideal training institute. Officials deputed are highly trained; their sage advices, insightful criticisms, and patient encouragement aided this report in innumerable ways. I would also like to thank trainers which steadfast support of this report was greatly needed and deeply appreciated.
  6. 6. DECLARATION We hereby declare that this project, neither as a whole nor as a part thereof has been copied from any source. It is further declared that we have developed this report entirely on the basis of our personal efforts under the sincere guidance of IESCO officials. ______________________ Muhammad Usman Rafiq
  7. 7. ABSTRACT Now a day’s everything is depending up on the power. So give the reliable supply to the consumers. In distribution systems one of the major parts is "SUBSTATIONS". An electrical substation is a subsidiary station of an electricity, Generation, Transmission and distribution systems where the voltage is transformed from high to low or reverse using the transformers .Electric power may flow through several substations between generating plant and consumer and may be changed in different voltage levels .the equipment used in substation are Transformer, Lightening arresters, isolator, bus bar, protective devices, Battery charger, earth switches, earth rods. So for of supply the regular maintenance and checking is necessary from that we conclude weather it is suitable or not for the desired operation.
  8. 8. TABLE OF CONTENTS Chapter 1 Introduction ....................................................................... 8 1.1 Substation .................................................................... 8 1.2 132Kv single-line grid substation diagram ............................... 9 1.2 Classification of substation ...................................................... 10 1.3 Function of substation ................................................. 11 Chapter 2 Equipment Used in a Sub Station …….................................. 12 2.1 Transformer ...................................................................... 12 Types of transformer 2.1.1 Power Transformer ............................................. 12 Parts of transformer 1. Conservative Tank .................................. 14 2. Tape Changer .......................... 15 3. Buchholz Relay .......................... 16 4. Silica Gel .......................... 17 2.1.2 Instrument transformer ........................ 19 Current transformer ........................ 19 Potential transformer ........................ 20 Unit Auxiliary transformer ........................ 21 Chapter 3 Circuit Breaker …………......................................................... 24 3.1 S F 6 g a s c i r c u i t b r e a k e r ........................... 24 Chapter 4 Bus Coupler ................................................... 27 4.1 Bus coupler ....................................... 27 Chapter 5
  9. 9. 11kv incoming and outgoing Panels ................................................. 29 5.1 11kv incoming Panels .............................................................. 29 5.2 11kv outgoing Panels .............................................................. 31 Chapter 6 Batteries and Batteries Charger ................................................. 32 6.1 Station Batteries System ................................................. 32 Chapter 7 Electrical Function Numbers ............................................. 36 7.1 Introduction ................................................. 36 7.2 List of device numbers and acronyms ........................................ 36 7.3 Suffixes and prefixes ........................................ 39
  10. 10. CHAPTER 1 Introduction: The present day electrical power system is a.c i.e. electric power is generated, transmitted and distributed in the form of Alternating current. The electric power is produce at the power station, which are located at favorable places. It is delivered to the consumer through a large network of transmission and distribution. At many place in the line of power system, it may be desirable and necessary to change some characteristic ( e.g. Voltage, ac to dc, frequency p.f. etc.) of electric supply. This is accomplished by suitable apparatus called sub-station for example, generation voltage (11kv or 6.6kv) at the power station is stepped up to high voltage (Say 220kv to 132kv) for transmission of electric power. Similarly near the consumer’s localities, the voltage may have to be stepped down to utilization level. This job is again accomplished by suitable apparatus called sub-stations. 1.1 Substation: An electrical substation is a subsidiary station of an electricity generation, transmission and distribution system where voltage is transformed high to low or the reverse using transformers. Electric power may flow through several substations between generation plant and consumer, and may be changed in voltage in several steps. The main equipment used in substation are transformers lighting arresters, Circuit breakers PLCC, isolators, bus bars, protective relays, Battery 8
  11. 11. charger, earth switches, earth rods. . 9
  12. 12. 1.2 Classification of substations: Classification of substations based on (1) Service requirements (2) Constructional features 1. According to service requirements: According to service requirements substations are classified into: i. Transformer Substations ii. Switching Substations iii. Power factor correction substations iv. Frequency changer substations v. Converting substations vi. Industrial substations 2. According to construction features: According to constructional features substations are classified as; i. Indoor substations ii. Outdoor substations iii. Underground substations iv. Pole mounted substations 10
  13. 13. 1.3 Functions of a Substation: 1 - Supply of required electrical power. 2 - Maximum possible coverage of the supply network. 3 - Maximum security of supply. 4 - Shortest possible fault-duration. 5 - Optimum efficiency of plants and the network. 6 - Supply of electrical power within targeted frequency limits, (49.5 Hz and50.5 Hz). 7 - Supply of electrical power within specified voltage limits. 8 - Supply of electrical energy to the consumers at the lowest cost. 11
  14. 14. Chapter 2 Equipment Used in a Sub-Station The equipment required for a transformer Sub-Station depends upon the type of Sub-Station, Service requirement and the degree of protection desired. TIF Sub-Station has the following major equipments. 2.1 Transformers: Transformer is a static machine, which transforms the potential of alternating current at same frequency. It means the transformer transforms the low voltage into high voltage & high voltage to low voltage at same frequency. It works on the principle of static induction principle. When the energy is transformed into a higher voltage, the transformer is called step up transformer but in case of other is known as step down transformer. TYPES OF TRANSFORMERS 2.1.1 Power Transformer: It is used for the transmission purpose at heavy load, high voltage greater than 33 KV & 100% efficiency. It also having a big in size as compare to distribution transformer, it used in generating station and Transmission substation at high insulation level. They can be of two types: Single Phase Transformers and Multi Phase Transformers. 12
  15. 15. 13
  16. 16. Nameplate: 14
  17. 17. Parts of power transformer: 15
  18. 18. i. Conservator Tank: This is a cylindrical tank mounted on supporting structure on the roof the transformer main tank. The main function of conservator tank of transformer is to provide adequate space for expansion of oil inside the transformer. Function of Conservator Tank of a Transformer: When transformer is loaded and when ambient temperature rises, the volume of oil inside transformer increases. A conservator tank of transformer provides adequate space to this expanded transformer oil. It also acts as a reservoir for transformer insulating oil. Construction of Conservator Tank: This is a cylindrical shaped oil container closed from both ends. One large inspection cover is provided on either side of the container to facilitate maintenance and cleaning inside of the conservator. Conservator pipe, i.e. pipe comes from main transformer tank, is projected inside the conservator from bottom portion. Head of the conservator pipe inside the conservator is provided with a cap. This pipe is projected as well as provided with a cap because this design prevents oil sludge and sediment to enter into main tank from conservator. Generally silica gel breather fixing pipe enters into the conservator from top. If it enters from bottom, it should be projected well above the level of oil inside the conservator. This arrangement ensures that oil does not enter the silica gel breather even at highest operating level. 16
  19. 19. Working of Conservator Tank: When volume of transformer insulating oil increases due to load and ambient temperature, the vacant space above the oil level inside the conservator is partially occupied by the expanded oil. Consequently, corresponding quantity of air of that space is pushed away through breather. On other hand, when load of transformer decreases, the transformer is switched off and when the ambient temperature decreases, the oil inside the transformer contracts. This causes outside air to enter in the conservator tank of transformer through silica gel breather. ii. Tape Changer: A tap changer is a connection point selection mechanism along a power transformer winding that allows a variable number of turns to be selected in discrete steps. A transformer with a variable turns ratio is produced, enabling stepped voltage regulation of the output. The tap selection may be made via an automatic or manual tap changer mechanism. 17
  20. 20. Voltage considerations: If only one tap changer is required, manually operated tap points are usually made on the high voltage (primary) or lower current winding of the transformer to minimize the current handling requirements of the contacts. However, a transformer may include a tap changer on each winding if there are advantages to do so. For example, in power distribution networks, a large step-down transformer may have an off- load tap changer on the primary winding and an on-load automatic tap changer on the secondary winding or windings. The high voltage tap is set to match long term system profile on the high voltage network (typically supply voltage averages) and is rarely changed. The low voltage tap may be requested to change positions multiple times each day, without interrupting the power delivery, to follow loading conditions on the low-voltage (secondary winding) network. To minimize the number of winding taps and thus reduce the physical size of a tap changing transformer, a 'reversing' tap changer winding may be used, which is a portion of the main winding able to be connected in its opposite direction (buck) and thus oppose the voltage. iii. Buchholz Relay: Buchholz relay in transformer is an oil container housed the connecting pipe from main tank to conservator tank. It has mainly two elements. The upper element consists of a float. The float is attached to a hinge in such a way that it can move up and down depending upon the oil level in the Buchholz relay Container. One mercury switch is fixed on the float. The alignment of mercury switch hence depends upon the position of the float. The lower element consists of a baffle plate and mercury switch. This plate is fitted on a hinge just in front of the inlet (main tank side) of Buchholz relay in transformer in such a way that when oil enters in the relay from that inlet in high pressure the alignment of the baffle plate along with the mercury switch attached to it, will change. 18
  21. 21. In addition to these main elements a Buchholz relay has gas release pockets on top. The electrical leads from both mercury switches are taken out through a molded terminal block. iv. Silica Gel Breather of Transformer: Whenever electrical power transformer is loaded, the temperature of the transformer insulating oil increases, consequently the volume of the oil is increased. As the volume of the oil is increased, the air above the oil level in conservator will come out. Again at low oil temperature; the volume of the oil is decreased, which causes the volume of the oil to be decreased which again causes air to enter into conservator tank. The natural air always consists of more or less moisture in it and this moisture can be mixed up with oil if it is allowed to enter into the transformer. The air moisture should be resisted during entering of the air into the transformer, because moisture is very harmful for transformer insulation. A silica gel breather is the most commonly used way of filtering air from moisture. Silica gel breather for transformer is connected with conservator tank by means of breathing pipe. 19
  22. 22. Construction of Silica Gel Breather: The silica gel breather of transformer is very simple in the aspect of design. It is nothing but a pot of silica gel through which, air passes during breathing of transformer. The silica gel is a very good absorber of moisture. Freshly regenerated gel is very efficient, it may dry down air to a dew point of below −40°C. A well maintained silica gel breather will generally operate with a dew point of −35°C as long as a large enough quantity of gel has been used. The picture shows a silica gel breather of transformer. Working Principle of Silica Gel Breather: Silica gel crystal has tremendous capacity of absorbing moisture. When air passes through these crystals in the breather; the moisture of the air is absorbed by them. Therefore, the air reaches to the conservator is quite dry, the dust particles in the air get trapped by the oil in the oil seal cup. The oil in the oil sealing cup acts as barrier between silica gel crystal and air when there is no flow of air through silica gel breather. The color of silica gel crystal is dark blue but, when it absorbs moisture; it becomes pink. When there is sufficient difference between the air inside the conservator and the outside air, the oil level in two components of the oil seal changes until the lower oil level just reaches the rim of the inverted cup, the air then moves from high pressure compartment to the low pressure compartment of the oil 20
  23. 23. seal. Both of these happen when the oil acts as core filter and removes the dust from the outside air. 2.1.2 Instrument Transformers: These transformers are used for the measurement purposes at that points where standard voltmeters and ammeters cannot be used. They are of two types: CURRENT TRANSFORMER: A current transformer (CT) is used for measurement of alternating electric currents. When current in a circuit is too high to apply directly to measuring instruments, a current transformer produces a reduced current accurately proportional to the current in the circuit, which can be conveniently connected to measuring and recording instruments. A current transformer isolates the measuring instruments from what may be very high voltage in the monitored circuit. Nameplate: 21
  24. 24. POTENTIAL OR VOLTAGE TRANSFORMER: Voltage transformers (VT) (also called potential transformers (PT)) are a parallel connected type of instrument transformer, used for metering and protection in high-voltage circuits or phase shift isolation. They are designed to present negligible load to the supply being measured and to have an accurate voltage ratio to enable accurate metering. A potential transformer may have several secondary windings on the same core as a primary winding, for use in different metering or protection circuits. Nameplate: 22
  25. 25. Unit Auxiliary Transformers (UAT) The Unit Auxiliary Transformer is the Power Transformer that provides power to the auxiliary equipment of a power generating station during its normal operation. This transformer is connected directly to the generator out- put by a tap-off of the isolated phase bus duct and thus becomes cheapest source of power to the generating station. It is generally a three-winding transformer i.e. one primary and two separate secondary windings. Primary winding of UAT is equal to the main generator voltage rating. The secondary windings can have same or different voltages i.e. generally 11KV and or 6.9KV as per plant layout. 23
  26. 26. 24
  27. 27. Chapter 3: Circuit Breaker: 3.1 Sf6 Circuit Breaker: In such breakers, sulphur hexafluoride gas (SF6) is used as the arc quenching medium. The sulphur hexafluoride gas (SF6) is an electronegative gas and has a strong tendency to absorb free electrons. The contacts of the breaker are opened in a high pressure flow of sulphur hexafluoride (SF6) gas and an arc is struck between them. The gas captures the conducting free electrons in the arc to form relatively immobile negative ions. This loss of conducting electrons in the arc quickly builds up enough insulation strength to extinguish the arc. The sulphur hexafluoride (SF6) circuit breakers have been found to be very effective for high power and high voltage service. Construction of SF6 Circuit Breaker: A sulphur hexafluoride (SF6) circuit breaker consists of fixed and moving contacts enclosed in a chamber. The chamber is called arc interruption chamber which contains the sulphur hexafluoride (SF6) gas. This chamber is connected to sulphur hexafluoride (SF6) gas reservoir. A 25
  28. 28. valve mechanism is there to permit the gas to the arc interruption chamber. When the contacts of breaker are opened, the valve mechanism permits a high pressure sulphur hexafluoride (SF6) gas from the reservoir to flow towards the arc interruption chamber. The fixed contact is a hollow cylindrical current carrying contact fitted with an arc horn. The moving contact is also a hollow cylinder with rectangular holes in the sides. The holes permit the sulphur hexafluoride gas (SF6) gas to let out through them after flowing along and across the arc. The tips of fixed contact, moving contact and arcing horn are coated with copper-tungsten arc resistant material. Since sulphur hexafluoride gas (SF6) gas is costly, it is reconditioned and reclaimed using suitable auxiliary system after each operation of breaker. Working of SF6 CB: In the closed position of the breaker, the contacts remain surrounded by sulphur hexafluoride gas (SF6) gas at a pressure of about 2.8 kg/cm2. When the breaker operates, the moving contact is pulled apart and an arc is struck between the contacts. The movement of the moving contact is synchronized with the opening of a valve which permits sulphur hexafluoride gas (SF6) gas at 14 kg/cm2 pressure from the reservoir to the arc interruption chamber. The high pressure flow of sulphur hexafluoride gas (SF6) rapidly absorbs the free electrons in the arc path to form immobile negative ions which 26
  29. 29. are ineffective as charge carriers. The result is that the medium between the contacts quickly builds up high dielectric strength and causes the extinction of the arc. After the breaker operation (i.e. after arc extinction), the valve is closed by the action of a set of springs. Advantages of SF6: Due, to the superior arc quenching properties of sulphur hexafluoride gas (SF6) gas, the sulphur hexafluoride gas (SF6) circuit breakers have many advantages over oil or air circuit breakers. Some of them are listed below Due to the superior arc quenching property of sulphur hexafluoride gas (SF6), such circuit breakers have very short arcing time. Since the dielectric strength of sulphur hexafluoride (SF6) gas is 2 to 3 times that operation due unlike of air, such breakers can interrupt much larger currents. The sulphur hexafluoride gas (SF6) circuit breaker gives noiseless operation due its closed gas circuit and no exhaust to atmosphere unlike the air blast circuit breaker. 27
  30. 30. Chapter 4: Bus Coupler 4.1 Bus Coupler: Bus coupler is a device which is used to couple one bus to the other without any interruption in power supply and without creating hazardous arcs. Bus coupler is a breaker used to couple two bus-bars in order to perform maintenance on other circuit breakers associated with that bus-bar. It is achieved with the help of a circuit breaker and isolators. 28
  31. 31. 29
  32. 32. Chapter 5: 11kv incoming and outgoing Panels 5.1 11kv incoming panel: Specifications: 11KV Incoming Panel for 20/26MVA power transformer with draw out type vacuumed circuit breaker, 2500A, 25KA, BIL 95KV, One minute power frequency withstand voltage 36KV, C.T. Ratio 1600:800/5/5A for metering and protection purpose having class 0.5 and 5P20 respectively, C.T. Ratio 1600:800/5A having protection class 5P20, P.T. 11000/110V AC, complete with over current and earth fault relay CDG61, Back up earth fault relay CDG21, DC supervision relay along with DC healthy lamp, 3 phase 4 wire energy meter for energy metering, moving iron type ampere meter, moving iron type power factor meter, Moving iron type volt meter with selector switch, On Off push button and indication lamps, DP and TP control MCB for AC & DC auxiliary voltage controls, Trip coil 110 V DC, Closing coil 110 V DC, Anti pumping feature, Spring charging motor 220 V AC, insulators and 99.9% pure tine coated copper bus bar arrangement covered with heat shrinkable tubing, Cable termination pads, Earthing ball arrangement for earthing kit, Explosion vents and Protection class IP3X 30
  33. 33. Nameplate: 31
  34. 34. 5.2 11kv outgoing panel: Specifications: 11KV Outgoing Panel with draw out type vacuumed circuit breaker, 630A, 25KA, BIL 95KV, One minute power frequency withstand voltage 36KV, C.T. Ratio 400:200/5/5A, complete with over current and earth fault relay CDG61, DC supervision relay along with DC healthy lamp, 3 phase 4 wire energy meter for energy metering, moving iron type ampere meter, moving iron type power factor meter, On Off push button and indication lamps, DP and TP control MCB for AC & DC auxiliary voltage controls, Trip coil 110 V DC, Closing coil 110 V DC, Anti pumping feature, Spring charging motor 220 V AC, insulators and 99.9% pure tine coated copper bus bar arrangement covered with heat shrinkable insulation tubing, Cable termination pads, Earthing ball arrangement for earthing kit, explosion vents and Protection class IP3X. 32
  35. 35. Nameplate: 33
  36. 36. Chapter 6 Batteries and Batteries Charger 6.1 Station Batteries System The purpose of station batteries system is to provide safe and liable power supply to all primary functions. The system is almost independent of all other power supply and ensures reliable execution of control functions. Dc batteries (110V) are installed in grid for protection, emergency power, alarm and indications. These batteries have their own battery charger. Under normal conditions, dc supplies are obtaining through AC to DC rectifier but in case of failure of AC supplies; DC are used to run the system. 34
  37. 37. Battery Nameplate: 35
  38. 38. Battery Charger Nameplate: 36
  39. 39. Chapter 7: Electrical Function Numbers 7.1 Introduction: In the design of electrical power systems, the ANSI standard device numbers (ANSI /IEEE Standard C37.2 Standard for Electrical Power System Device Function Numbers, Acronyms, and Contact Designations) identifies the features of a protective device 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. Device numbers are used to identify the functions of devices shown on a schematic diagram. Function descriptions are given in the standard. One physical device may correspond to one function number, for example "29 Isolating Switch", or a single physical device may have many function numbers associated with it, such as a numerical protective relay. Suffix and prefix letters may be added to further specify the purpose and function of a device. ANSI/IEEE C37.2-2008 is one of a continuing series of revisions of the standard, which originated in 1928. 7.2 List of device numbers and acronyms: 2 – Time delay Starting or Closing Relay 3 – Checking or Interlocking Relay 4 – Master Contactor 5 – Stopping 6 – Starting Circuit Breaker 7 – Rate of Change Relay 8 – Control Power Disconnecting Device 9 – Reversing Device 10 – Unit Sequence Switch 11 – Multi-function Device 12 – Overspeed Device 13 – Synchronous-speed Device 14 – Underspeed 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 Contractor 20 – Electrically Operated Valve 37
  40. 40. 21 – Distance Relay 22 – Equalizer Circuit Breaker 23 – Temperature Control Device 24 – Volts Per Hertz Relay 25 – Synchronizing or Synchronize-Check Device 26 – Apparatus Thermal Device 27 – Undervoltage Relay 27s - DC under voltage Relay 28 – Flame detector 29 – Isolating Contactor or Switch 30 – Annunciator Relay 31 – Separate Excitation 32 – Directional Power Relay or Reverse Power Relay 33 – Position Switch 34 – Master Sequence Device 35 – Brush-Operating or Slip-Ring Short-Circuiting Device 36 – Polarity or Polarizing Voltage Devices 37 – Undercurrent or Underpower Relay 38 – Bearing Protective Device 39 – Mechanical Condition Monitor 40 – Field (over/under excitation) Relay 41 – Field Circuit Breaker 42 – Running Circuit Breaker 43 – Manual Transfer or Selector Device 44 – Unit Sequence Starting Relay 45 – DC over voltage Relay 46 – Reverse-phase or Phase-Balance Current Relay 47 – Phase-Sequence or Phase-Balance Voltage Relay 48 – Incomplete Sequence Relay 49 – Machine or Transformer, Thermal Relay-OLR 50 – Instantaneous Overcurrent Relay 50G - Instantaneous Earth Over Current Relay (Neutral CT Method) 50N - Instantaneous Earth Over Current Relay (Residual Method) 50BF - Breaker failure 51 – AC Inverse Time Overcurrent Relay 51LR - AC Invers Time overcurrent (locked Roter) protection Relay 51G - AC Inverse Time Earth Overcurrent Relay (Neutral CT Method) 51N - AC Inverse Time Earth Overcurrent Relay (Residual Method) 52 – AC Circuit Breaker 52a - AC Circuit Breaker Position (Contact Open when Breaker Open) 52b - AC Circuit Breaker Position (Contact Closed when 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 60 – Voltage or Current Balance Relay. 61 – Density Switch or Sensor 62 – Time-Delay Stopping or Opening Relay 63 – Pressure Switch 64 – Ground Detector Relay 64R - Restricted earth fault 38
  41. 41. 64S - Stator earth fault 65 – Governor 66 – Notching or Jogging Device 67 – AC Directional Overcurrent Relay 67N- Directional Earth Fault relay 68 – Blocking Relay 69 – Permissive Control Device 70 – Rheostat 71 – Liquid Level 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 Relay or "Out-of-Step" Relay 79 – AC Reclosing Relay (Auto Reclosing) 80 – Flow Switch 81 – Frequency Relay 82 – DC Reclosing Relay 83 – Automatic Selective Control or Transfer Relay 84 – Operating Mechanism 85 – Communications,Carrier or Pilot-Wire Relay 86 – Lockout Relay/Master Trip 87 – Differential Protective Relay 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( trip circuit supervision Relay) 95 – For specific applications where other numbers are not suitable 96 – Busbar Trip Lockout relay 97 – For specific applications where other numbers are not suitable 98 – For specific applications where other numbers are not suitable 99 – For specific applications where other numbers are not suitable 150 – Earth Fault Indicator AFD – Arc Flash Detector CLK – Clock or Timing Source DDR – Dynamic Disturbance Recorder DFR – Digital Fault Recorder DME – Disturbance Monitor Equipment 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 RTU – Remote Terminal Unit/Data Concentrator SER – Sequence of Events Recorder 39
  42. 42. 7.3 Suffixes and prefixes: A suffix letter or number 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 a relay is used for protection against Neutral Displacement); and suffixes X, Y, Z are used for auxiliary devices. Similarly, the "G" suffix can denote a "ground"; hence a "51G" is a time overcurrent ground relay. The "G" suffix can also mean "generator", hence an "87G" is a Generator Differential Protective Relay while an "87T" is a Transformer Differential Protective Relay. "F" can denote "field" on a generator or "fuse", as in the protective fuse for a pickup transformer. Suffix numbers are used to distinguish multiple "same" devices in the same equipment such as 51-1, 51–2. Device numbers may be combined if the device provides multiple functions, such as the instantaneous/time-delay AC over current relay denoted as 50/51. For device 16, the suffix letters further define the device: the first suffix letter is 'S' for serial or 'E' for Ethernet. The subsequent letters are: 'C' security processing function (e.g. VPN, encryption), 'F' firewall or message filter, 'M' network managed function, 'R' rotor, and ‘S’ switch and 'T' telephone component. Thus a managed Ethernet switch would be 16ESM. 40