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Electrical engineering (EET301)
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(Autonomous) (ISO/IEC - 27001 - 2013 Certified)
WINTER – 2022 EXAMINATION Model Answer Subject Name: Electrical Substation Practices
22633: ESP
Important Instructions to examiners: 1) The answers should be examined by key words and not as word-to-word as given in the model answer scheme. 2) The model answer and the answer written by candidate may vary but the examiner may try to assess the understanding level of the candidate. 3) The language errors such as grammatical, spelling errors should not be given more Importance (Not applicable for subject English and Communication Skills). 4) While assessing figures, examiner may give credit for principal components indicated in the figure. The figures drawn by candidate and model answer may vary. The examiner may give credit for any equivalent figure drawn. 5) Credits may be given step wise for numerical problems. In some cases, the assumed constant values may vary and there may be some difference in the candidate’s answers and model answer. 6) In case of some questions credit may be given by judgement on part of examiner of relevant answer based on candidate’s understanding. 7) For programming language papers, credit may be given to any other program based on equivalent concept. 8) As per the policy decision of Maharashtra State Government, teaching in English/Marathi and Bilingual (English + Marathi) medium is introduced at first year of AICTE Diploma Programme from academic year 2021-2022. Hence if the students in first year (first and second semesters) write answers in Marathi or bilingual language (English +Marathi), the Examiner shall consider the same and assess the answer based on matching of concepts with model answer. Q. No.
Sub Q. Answer
Marking Scheme
- Attempt any FIVE: 10 Marks a) Compare indoor & outdoor substation on the basis of the following points: (i) Installation cost (ii) Lightning protection Ans: Sr. No. Particular Indoor Substation Outdoor Substation
i. Installation cost More Less
ii. Lightning protection
Not required as all the equipment are installed inside a close building
Required as all the equipment are installed outdoor
1 Mark each = 2 Marks
b) State the functions of three phase distribution transformer. Ans: Functions of three phase distribution transformer: It is a step down transformer. It transmits power to the secondary distribution circuit It reduces the voltage of the primary distribution circuit to a voltage level as per the consumer requirement.
1 Mark for each of any two = 2 Marks
c) Differentiate between 11 kV & 33 kV substation on the basis of (i) Location (ii) Application Ans: Sr. No. Particular 11 kV Substation 33 kV Substation i. Location Located at the end of primary distribution system and the start of secondary distribution system
Located at the end of secondary transmission system and the start of primary distribution system
1 Mark each = 2 Marks
(Autonomous) (ISO/IEC - 27001 - 2013 Certified)
WINTER – 2022 EXAMINATION Model Answer Subject Name: Electrical Substation Practices
22633: ESP
ii. Applications i) To receive power from primary distribution system and supply to consumer use. ii) To supply power to commercial complex and for residential use.
i) To receive power from secondary transmission system and supply to primary distribution system ii) To supply power to 11 kV feeder for commercial or industrial use. d) State the meaning of System Earthing. Ans: System Earthing: (i) In System earthing, the neutral of the system is directly connected to earth with the help of the low resistance GI wire. The system earthing is also called the Neutral earthing. (ii) Such type of earthing is mostly provided to the system which has star winding. For example, the neutral earthing is provided in the generator, transformer, motor etc.
2 Marks for correct answer
e) Justify the use of Earth Mat in 132 kV substation. Ans: Use of Earth Mat in 132 kV substation: (i) Primary requirement of earthing is to have a low earth resistance. Substation involves many earthings through individual electrodes, which will have fairly high resistance. (ii) If these individual electrodes are inter linked inside the soil, forming earth mat, it increases the area in contact with soil and creates number of parallel paths. (iii) Hence the value of the earth resistance using earth mat will be much lower than the individual value. So earth mat is used in 132 kV substation.
2 Marks for correct answer
f) List any two advantages of GIS substation. Ans: Advantages of GIS substation: (i) Space required is less i. 1/10th of conventional substation (ii) GIS are very safe & operating personnel are protected by the earthed metal enclosure. (iii) Most reliable compared to air insulated substation. (iv) Weight is very less due to aluminium enclosure used. (v) No pollution. (vi) Dielectric strength of SF 6 Gas is 3 times the dielectric strength of air. (vii) Time of erection is less as assembled parts are used.
1 Mark for each of any two advantages = 2 Marks
g) State the reason behind higher cost of GIS substation compared to ordinary conventional substation. Ans: Reason behind higher cost of GIS substation: (i) In the GIS system, all the live components are enclosed in a grounded metal enclosure, and then the whole system is housed in a chamber full of gas, which results in the increase in cost. (ii) Whole substation is assembled in closed constructed building, which increases the cost.
1 Mark for each of any two reasons = 2 Marks
(Autonomous) (ISO/IEC - 27001 - 2013 Certified)
WINTER – 2022 EXAMINATION Model Answer Subject Name: Electrical Substation Practices
22633: ESP
energy / power among feeders. ii) Bus-bars: A bus-bar in electrical power distribution refers to busbar formed by using line conductors or thick strips of copper or aluminium in control panel within the substation. iii) Circuit breakers (33 kV and 11 kV): It is a switching device used to interrupt / make not only the load current but also the much larger fault current, which may occur on a circuit. iv) Isolators or isolating switches (33 kV and 11 kV): These are mechanical switching devices capable of opening or closing a circuit:
- When a negligible current is to be interrupted / made or
- Only a small charging current is to be interrupted or
- When no significant voltage difference exists across the terminals of each pole. v) Earthing switches: Earthing switches are provided at various locations to facilitate maintenance. Main blades and earth blades are interlocked with both electrical and mechanical means. The earthing switch must be capable of withstanding short circuit current for short duration as applicable to the isolator. vi) Insulators: It provides adequate insulation for live parts, which is of prime importance for obvious reasons of reliability of supply, safety of personnel and equipment. vii) Power and control cables: Power and control cables of adequate current carrying capacity and voltage rating are provided at the substation. Power cables are used for 33kV,11 kV or LT system to carry load current. The control cables are required for operating and protection system connections. viii) Control panel: Control panels installed within the building which provide mounting for mimic bus, relays, meters, indicating instruments, indicating lights, control switches, test switches and other control devices. The panel contains compartments for incoming lines, outgoing lines, busbars with provision for sectionalizing, relays, measuring instruments, etc. ix) Lightning protection: Surge arrestors - Large over voltages that develop suddenly on electric transmission and distribution system are referred to as “surges” or “transients”. These are caused by lightning strikes or by circuit switching operations. Surge arrestor is a protective device for limiting surge voltages on equipment by discharging or bypassing surge current. The surge arrestor which responds to over-voltages without any time delay is installed for protection of 33 kV switchgear, transformers, associated equipment and 11 kV and 33 kV lines. x) Instrument transformers (CTs and PTs): The substations have current and voltage transformers designed to isolate electrically the high voltage primary circuit from the low voltage measurement and protection circuit and thus, provide a safe means of supply for indicating instruments, meters and relays. xi) Earthing arrangements: Earthing must be provided for - − safety of personnel, − prevention of and minimizing damage to equipment because of flow of heavy fault currents, and
1 Mark each for any four accessories with their function = 4 Marks
(Autonomous) (ISO/IEC - 27001 - 2013 Certified)
WINTER – 2022 EXAMINATION Model Answer Subject Name: Electrical Substation Practices
22633: ESP
− improved reliability of power supply. xii) Reactive compensation: It is always a good idea to ensure a power factor correction for transformers. When they are operating on low load (e. during the night) they absorb reactive power, which must be compensated to avoid unnecessary loadings and losses. xiii) DC supply arrangement: Station batteries supply energy to operate protection equipment such as breakers and other control, alarm and indicating equipment. The station batteries are a source for operating DC control system equipment during system disturbances and outages. During normal conditions the rectifier provides the required DC supply. However, to take care of rectifier failure, a storage battery of adequate capacity is provided to meet the DC requirements. xiv) Auxiliary supply transformer: An Auxiliary Supply Transformer of adequate capacity is required to be provided for internal use for lighting loads, battery charging, oil filtration plant, etc. The supply should be reliable. In a substation it is normally provided from a station transformer connected on 33 or 11 kV bus bar. xv) Fire-fighting system: In view of the presence of oil filled equipment in a substation, it is important that proper attention is given to isolation; limitation and extinguishing of fire so as to avoid damage to costly equipment and reduce chances of serious dislocation of power supply as well as ensure safety of personnel. d) Describe procedure to undertake safe preventive maintenance in 132 kV substation. Ans: Procedure to undertake safe preventive maintenance in 132 kV substation: i) Complete isolation, discharging and effective grounding of the concerned circuit/equipment before starting work. ii) Use of rubber gloves/gantlets, while operating switches/links and during discharging and grounding. iii) Obtaining proper permit to work before commencing work on any line/equipment. If the operator has to work himself, he should avail self-line clear recording all operations and then only work. Self-line clears should be limited to emergencies only. iv) Return of the “Permit to work” (by the same person who takes it) after ensuring that all equipment are free from men, material and ground. v) Authorization of persons by name to work on particular clause of line/equipment. An approved list Permit To Work (P.T.) on equipment should be issued or taken only by the persons who are directly in-charge of the lines or equipment concerned. Helpers should work under the guidance of higher category officials only, except in isolated stations, where selected men may be authorized by name, when necessary, and considered quite justified by the Executive Engineer on recommendation of the Assistant Engineer. vi) Efficient Supervision by a qualified and responsible person while carrying out works to adjacent energized circuits. vii) Use of “Safe for Work” boards on equipment declared safe for work. viii) Locking and hanging “men–on-line” boards on switches controlling circuits
½ Mark for each of any eight procedure points =4 Marks
(Autonomous) (ISO/IEC - 27001 - 2013 Certified)
WINTER – 2022 EXAMINATION Model Answer Subject Name: Electrical Substation Practices
22633: ESP
All of the reasons listed above lead back to one ultimate benefit of preventive maintenance: it saves money. Unplanned maintenance typically costs 3 to 9 times more than planned maintenance. OR
- Routine maintenance helps to prevent minor faults from developing into major breakdown.
- Routine maintenance helps to reduce breakdown period.
- Routine maintenance helps to keep the machine in good working condition by reducing wear and tear.
- Routine maintenance helps to provide greater safety & protection to the workers.
- Routine maintenance helps to use less standby equipment.
- Routine maintenance helps to increase life of equipment.
- Routine maintenance helps to avoid inconvenience caused due to equipment failure.
- Routine maintenance helps to increase productivity.
- Routine maintenance helps to determine the need for major & minor repairs.
- Routine maintenance helps to develop maintenance schedule at low cost.
c) Describe the procedure to perform voltage breakdown test on transformer oil. Ans: Voltage breakdown test on transformer oil:
Procedure: - The sample of oil is taken from near the top & bottom of the transformer. In this kit, there are two electrodes separated by small gap of 2 mm or 4mm between them. The cup (test cell) is filled with sample of oil to be tested up to about 1 cm above the electrodes. The cup top is covered with clean glass plate. Now slowly raise the voltage between the electrodes till breakdown of oil occurs or sparking starts between the electrodes. And note down voltage reading. Repeat the procedure by taking same sample of oil 3 to 6 times & Calculate average of all results to finalize the breakdown voltage of oil sample.
1 Mark for diagram
3 Marks for procedure
(Autonomous) (ISO/IEC - 27001 - 2013 Certified)
WINTER – 2022 EXAMINATION Model Answer Subject Name: Electrical Substation Practices
22633: ESP
d) State the meaning and functions of PLCC used in 132kV / 33 kV substation. Ans: PLCC: PLCC means Power Line Carrier Communication. It refers to a technique in which power transmission line is used as communication line for transferring communication / telephone signals from one substation to the other. Function of PLCC:
- Telecommunication & Telemonitoring: Power-line carrier communication (PLCC) is mainly used for tele-communication, and tele-monitoring between electrical substations through power lines at high voltages, such as 110 kV, 220 kV, 400 kV.
- Telephony: PLCC can be used for interconnecting private branch exchanges (PBXs) for voice messaging.
- Line Protection: For the purpose of carrier aided protection, PLCC channels use modulation schemes namely the Amplitude modulation (AM) for blocking schemes and Frequency Shift keying (FSK) for unblocking, permissive and direct-trip schemes.
- Telemetering: To monitor electrical quantities like voltage, current, power (kW, kVA, kVAR) etc. at remote locations.
1 Mark for meaning
3 Marks for any 3 functions (Diagram is optional)
4 Attempt any THREE: 12 Marks a) Describe any four important safety practices followed during breakdown maintenance in 11 kV substation. Ans: Important safety practices followed during breakdown maintenance in 11 kV substation: 1) Complete isolation, discharging and effective grounding of the concerned circuit/equipment carried out before starting maintenance work. 2) Use of rubber gloves/gantlets, while operating switches/links and during discharging and grounding. 3) Obtaining proper permit to work before commencing work on any line/equipment. 4) Return of the “Permit to work” (by the same person who takes it) after ensuring that all equipment are free from men, material and ground. 5) Authorization of persons by name to work on particular clause of
1 Mark for each of any four practices = 4 Marks
(Autonomous) (ISO/IEC - 27001 - 2013 Certified)
WINTER – 2022 EXAMINATION Model Answer Subject Name: Electrical Substation Practices
22633: ESP
break load current on isolator. Similarly, isolator should not be closed on load. However certain isolators are designed to change / discharge transformer (without load) and small length of overhead lines or cables. b) Determine the rating of LA, CT, PT and DO fuse for mounting of 500 kVA, 11 kV/0 kV plinth mounted substation. Ans: Rating of LA: Voltage rating = 1× 11×0 = 9 Power frequency spark over voltage = 1×9 = 14 Nominal discharge current = 5kA Rated voltage: 12 kV Continuous Operated voltage: 10kV Long duration discharge class 2 High current impulse withstand value 100KA Energy absorption capacity: 6KJ/KV (Fpr 3 sequential shot) Rating of CT: Normal system voltage (KV rms): 11 KV Highest system voltage (KV rms): 12 KV Frequency: 50Hz Impulse withstand voltage: 75 KV peak Insulation level: 12 Kv One minute power frequency dry withstand voltage: a) primary (KV r.m.): 28 KV b) secondary (KV r.m.): 03 KV Transformation ratio (CT Ratio): a) For Consumer Metering : 100/5 A, 50/5 A & 15/5 A b) For Feeder Metering: 200/5 A Rated output (VA burden): 10 VA Class of accuracy: 0 S Short time thermal current rating: 6 KA for one second for CT ratio 5/5 A & 15/ A, 18 KA for one second for CT Ratio 50/5 A & 100/5 A 18 KA for 3 seconds for CT ratio 200/5 A Rating of PT: Normal system voltage (KV rms): 11 KV Highest system voltage (KV rms): 12 KV Nos. of phases: Three Impulse withstand voltage (KVP): 95 One minute power frequency dry withstand voltage (on assembled CT-PT set) i) primary (KV r.m.): 28 ii) secondary (KV r.m.): Frequency: 50Hz Transformation ratio (PT Ratio): 11 KV/ 110V Rated output (VA burden): 30 VA per phase Class of accuracy: 0 S Temp. rise over max. ambient temp: Within limits of IS:3156/ Ratio error (Max.): Within limits of IS:3156/
1 Mark for minimum two ratings of each device = 4 Marks
(Autonomous) (ISO/IEC - 27001 - 2013 Certified)
WINTER – 2022 EXAMINATION Model Answer Subject Name: Electrical Substation Practices
22633: ESP
Rating of DO fuse: Type: Expulsion type drop out, outdoor type Mounting: Vertical Standard specification: IS 9385/ System voltage: 12/24 KV, 36KV Rated current: 100/200 A Insulation level: As per IS standard Fuse Carries: SRBP/ Fibre tube Operation: In service the fuse carrier is latched in OR Any other Equivalent c) Write the name of relevant fire-fighting equipment used in case of power transformer fire and justify its use. Ans: Relevant fire-fighting equipment used in case of power transformer fire:
- Deluge System: This system uses open spray heads attached to a piping system connected to a water supply through a valve that is opened by means of a detection system installed in the same area as the spray heads. When the valve opens, water flows into the piping system and discharges through all spray heads attached to the system. This type of system uses high volumes of water which may lead to other post fire clean up issues or contaminated runoff.
- Fixed Water Spray System: This system is similar to a deluge system; however, the water discharge points are designed to create a spray pattern unique to the particular area or equipment being protected. The water spray head locations and spray pattern are tailored to the asymmetrical shape of the equipment being protected. The added benefit of the equipment specific design is the control of fire spread through increased wetting of the equipment under the influence of the fire. Electrical transformers containing oil are commonly protected by fixed water spray systems.
- Water Mist System: This system is similar to the fixed water spray system with an added benefit of using significantly less water by employing special discharge heads creating water droplets called mist. A water mist system is generally defined by the droplet size created. Droplet sizes typically are less than 1000 microns and delivered by a high-pressure pump. The water droplets create a mist that allows a given volume of water to create a larger surface area exposed to the fire. Smaller droplets facilitate larger heat absorption to cool the fire.
- Pre-action Water Mist System: This system uses automatic sprinklers attached to a piping system containing air with a supplemental detection system installed in the same areas as the sprinklers. System activation may require both a signal from the detection system and the heat activation of a sprinkler. Pre-action systems are used to protect areas where the risk of false discharge or leakage must be kept to an absolute minimum. This system has recently seen increased occurrence of use in transformer fire suppression because of water conservation, greater immunity to false initiation and greater ability to control fire spread. (Or Any other equivalent)
Any one to be considered
1 Mark for name + 3 Marks for justification = 4 Marks
d) List any four important safety practices followed during routine maintenance of GIS substation.
(Autonomous) (ISO/IEC - 27001 - 2013 Certified)
WINTER – 2022 EXAMINATION Model Answer Subject Name: Electrical Substation Practices
22633: ESP
- Failure of protective relaying circuit causes faults to persist and ultimately fire.
- Unskilled persons employed for sensitive circuits cannot maintain it properly and so faults can be developed ultimately resulting fire. (OR Any other Equivalent) 5 Attempt any TWO: 12 Marks a) Describe the procedure to measure the insulation resistance of distribution transformer using neat labelled diagram. Ans: Procedure to measure Insulation Resistance of Distribution transformer:
- Do not disconnect the ground connection to the transformer tank and core. Make sure that the transformer tank and core are grounded.
- Disconnect all high-voltage, low-voltage, and neutral connections, lightning arresters, fan systems, meters, or any low-voltage control systems that are connected to the transformer winding.
- Before beginning the test, jumper together all high-voltage bushings, making sure that the jumpers are clear of all metal and grounded parts. Also jumper together all low-voltage and neutral bushings, making sure jumpers are clear of all metal and grounded parts.
- Use a mega-ohmmeter (megger) with a minimum scale of 20,000 MΩ.
- Resistance measurements are then made between each set of windings and ground. The windings that are to be measured must have their ground removed to measure their insulation resistance.
- Mega-ohmmeter reading should be maintained for 1 min. For three-winding transformers, the test should be made as follows:
- High to low, tertiary and ground (H-LTG), shown in Figure (a).
- Tertiary to high, low and ground (T-HLG).
- Low to high, tertiary and ground (L-HTG), shown in Figure (b).
- High, low and tertiary to the ground (HLT-G).
- High and tertiary to low and ground (HT-LG), shown in Figure (c).
- Low and tertiary to high and ground (LT-HG).
- High and low to tertiary and ground (HL-TG).
3 Marks for procedure + 3 Marks for diagram = 6 Marks
(Autonomous) (ISO/IEC - 27001 - 2013 Certified)
WINTER – 2022 EXAMINATION Model Answer Subject Name: Electrical Substation Practices
22633: ESP
b) Draw neat labelled single line diagram of 33kV substation and describe the functions of circuit breaker and isolator. Ans: Function of Circuit breaker: 1) A circuit breaker is a switching device built ruggedly to enable it to interrupt/ make not only the load current but also the much larger fault current, which may occur on a circuit. 2) A circuit breaker contains both fixed contacts and moving contacts. The purpose of circuit breakers is to eliminate a short-circuit that occurs on a line. 3) Circuit breakers are found at the arrivals and departures of all lines incident on a substation. 4) When the circuit breaker is closed these contacts are held together. The mode of action of all circuit breakers consists in the breaking of the fault current by the separation of the moving contacts away from the fixed ones. An arc is immediately established on separation of the contacts. Interruption of the current occurs after the arc at these contacts is extinguished and current becomes zero. Function of Isolator:
- Isolators are mechanical switching devices capable of opening or closing a circuit: − when a negligible current is broken or made, or − only a small charging current is to be interrupted, or − when no significant voltage difference exists across the terminals of each pole. 2) Isolators can carry current under normal conditions and short circuit currents for a specified time. In open position, the isolator should provide an isolating distance between the terminals. Single line diagram of 33kV substation:
(OR Any other equivalent single line diagram)
1½ Mark
1½ Mark
3 Marks for labeled diagram
(Autonomous) (ISO/IEC - 27001 - 2013 Certified)
WINTER – 2022 EXAMINATION Model Answer Subject Name: Electrical Substation Practices
22633: ESP
6 Attempt any TWO: 12 Marks a) Illustrate the procedure to carry out preventive maintenance of 33kV/11kV air break circuit breaker. Ans: Procedure to carry out Preventive Maintenance of 33kV/11kV Air Break Circuit Breaker: 1. Isolate properly the air break circuit breaker or take it from the circuit away. 2. Use a vacuum cleaner for thorough de-dusting (dry cloth can be used also). 3. Insulation: Remove and clean interphase barriers. Clean all insulating materials with vacuum and/or using cleaning agent. 4. Check control terminal blocks / wires for any damage or sparking or looseness. Use WD-40 cleaning agent for cleaning purpose. 5. Contacts: Ensure that all contacts are clean, smooth, and in proper alignment. 6. On silver contacts, discoloration is not usually harmful unless caused by insulating deposits. Clean silver contacts with alcohol or silver cleaner using non- abrasive cloths. 7. If possible, a contact resistance test should be performed to determine the quality of the contacts. Measure contact resistance of power terminals (under test mode). 8. Draw out contacts on the circuit breaker and the stationary contacts in the cubicle should be cleaned and inspected for overheating, alignment, and broken or weak springs. Coat contact surfaces with contact lubricant to ease mating. 9. Arc Interrupter: Clean all ceramic materials of loose dirt and examine for signs of moisture, make sure the assemblies are clean and dry. Examine for cracked or broken pieces. Dirt and arcing deposits may be removed by light sanding, do not use emery cloth or wire brushes which may leave conductive residue behind. Repair or replace as necessary. Examine arc chutes for dirt and/or dust accumulations and clean as necessary 10. Check air puffer for proper operation. 11. Operating Mechanism: Inspect for loose, broken, worn or missing parts (consult manufacturer’s schematics for required parts). Examine for excessive wear of moving parts. Observe that operating mechanisms function properly without binding, hanging, or without delayed action. 12. Ensure that spring pressures are maintained according to manufacturer’s specifications. 13. Manually close breaker to check for proper wipe, contact pressure, contact alignment, and to ensure that all contacts make at approximately the same time. 14. Auxiliary Devices: Inspect operating devices for proper operation and general condition. Ensure all indicating devices are fully functional and properly set. 15. Measure breaker closing time and opening time (it must match the original value) during preventive maintenance of breakers. 16. Check-up of all mechanical components.
1 Mark for each of any six steps = 6 Marks
b) Describe “Safety practices” followed during breakdown maintenance of 132kV substation. Ans: Safety practices to be followed during breakdown maintenance of 132kV substation:
(Autonomous) (ISO/IEC - 27001 - 2013 Certified)
WINTER – 2022 EXAMINATION Model Answer Subject Name: Electrical Substation Practices
22633: ESP
- Properly isolate the equipment under breakdown.
- Do the local earthing.
- No unsafe operation should be permitted.
- Interlocks should not be bye-passed unless it is very essential.
- Operation & maintenance staff should be authorized to work on the breakdown equipment.
- Operation & maintenance staff should be familiar with the station layout and operating limits of different equipment such as breakers, transformers, Isolators, CTs, PTs, etc. A person should be allowed to operate or take over the equipment only after he has acquired adequate knowledge of the equipment.
- Operations and maintenance manuals/manufacturers instructions for different equipment should be available and should be referred to before carrying breakdown maintenance.
- It is the responsibility of the supervisor to interpret correctly and explain safety rules and regulations to all the persons concerned and ensures that they thoroughly understand the same.
- Supervisor shall guard against the use of defective safety appliances, tools and materials.
- In case of any emergency, in which quick action is necessary in order to safeguard life or property, persons are authorized to take necessary action, which is thoroughly understood by them. Under no circumstances attempt shall be made to carry out operations which are not safe.
- All persons must use the standard protective equipment intended for the job.
- All protective equipment should be periodically tested.
- Metal ladders should not be used in switchyard.
- Adequate number of first aid and fire-fighting equipment shall be maintained.
- Every person should be familiar with fire-fighting and should know how to operate fire-fighting equipment, so that fire can be extinguished promptly minimizing damage.
- In the event of fire on electrical installation, the affected part shall be immediately switched-off and isolated from all the sources.
- First aid and artificial respiration chart should be exhibited.
- While working on the breaker, its operating mechanism should be de-energized such as discharging spring, release air pressure etc.
- Transformer should be discharged and grounded from all sides (windings). Neutral grounding of the transformer should not be treated as grounding.
- Current transformer secondaries should never be left open circuited.
- After disconnection of capacitor bank, it should be allowed to discharge through discharge PT for about 5 minutes. The bank should be grounded with hot stick before commencing the work.
- Apparatus, frame work and other non-current carrying metal parts associated with power system are to be effectively grounded.
1 Mark for each of any 6 practices = 6 Marks
c) Describe the importance of partial discharge monitoring system for the GIS substation. Ans: Importance of partial discharge monitoring system for the GIS substation:
22633
Course: Electrical engineering (EET301)
University: Rashtrasant Tukadoji Maharaj Nagpur University
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