EMTR AND AUTO TRANSFER
• What is meant by EMTR?
In case of normal supply failure to CL-III & CL-II the loads will be fed by the
alternative/standby sources. This changeover of supply is called Emergency
Transfer.
• How EMTR is initiated?
EMTR is initiated on sensing the CL-III & CL-II bus under voltage.
• What are the routes of EMTR?
CL-III bus under voltage. The DG’s will start. All the breakers connected to the
affected bus will trip. DG breaker will close on dead bus. Loads will be restored one
by one.
CL-II bus under voltage. The tie breaker of the affected bus will close.
• What does load-shedding mean?
When there is only one source to feed the two buses, the total loads can not be fed by
this single source. Hence some of the less important load will not be allowed to start
or it will be tripped if it is running.
• What does total load-shedding mean?
Even after the load shedding the is continue to deliver more than the rated power
sensed by overpower relay or running with under frequency sensed by the under
frequency relay the total load shedding will take place. In case of auxiliary
transformer is feeding the total load shedding will take place after 4 minutes.
• What does auto transfer mean?
If one of the sources is tripped on main protection its breaker will be tripped and the
tie-breaker will close. This transfer of supply from one source to other source is
called auto transfer. To restore the class IV whenever the UT or SUT is lost Auto
transfer is provided.
• Why auto transfer is prevented if the backup protection is operated?
The back up protection is supposed to operate in case of a bus fault. Hence the auto
transfer is prevented.
• What are the types Auto transfer scheme?
1. Fast transfer scheme to close the tie-breaker in less than 200 milli seconds. This
limits transient current and voltage dip in the bus and does quick acceleration of
the motors.
2. Slow transfer after 200 milli seconds.
• What are the conditions for Auto transfer scheme?
Backup protections are not allowed to initiate the Auto transfer. Because under
voltage may exist in the bus. Similarly protection in LV of the transformers are not
initiating the Auto transfer scheme. There are three metrics used in Auto transfer
scheme and 2/3 logic is adopted.
Conditions
1. Fault generator (86BG or 86A1).
2. Fault in UT.
3. Fault in GT.
4. Fault in 220 kV bus (SUT).
5. Fault in SUT (86M).
• What are the uses of EMTR scheme?
1. To restore class III when class IV supply fails.
2. To extend supply to class II when UPS fails.
3. In one DG condition to load restoration.
4. Sub sequent restoration of large motor loads.
• What are the sequences of motor load restoration in EMTR?
1. AHPPW –1001 - 4 Sec.
2. APWC – 1003 - 8 Sec.
3. APWC – 1004 - 12 Sec.
4. AHPPW –1002 - 16 Sec.
5. PPP – 1001 - 20 Sec.
6. MOD – 1002 - 24 Sec.
7. MOD – 1001 - 28 Sec.
8. Air Comp – 1002 - 32 Sec.
9. ABFP – 1006 - 36 Sec.
10. 7343 Exst Fan 1003 - 40 Sec.
11. ECCS PM 1001 - 44 Sec.
12. ECCS PM 1002 - 48 Sec.
• Why synchronizing scheme has been adopted? What are interlocks provided?
To check running and incoming buses, which are going to be interconnected are in
synchronism with each other.
Interlocks
1. Synch selector.
2. Only one breaker can operate at a time.
3. Master synch relay contact should available (bypass will bypass this synch
contact).
Bypass facility is provided to close the breaker on dead bus only.
• What are the settings provided in synchronizing scheme (SKE Relay)?
Voltage – V1- V2 = 10%
Frequency – t = 0.05 Sec (2.5 Hz)
% Slip – 0.45
Phase angle difference - 20°.
• What are the major losses in nuclear power generating system?
Condenser - 500 MW.
Moderator - 40 MW.
C/V and E/S system - 3.7 MW.
• Give the specification of DG and NGR of DG.
DG specification
Type HSPTL 12/653 synchronous generator.
KVA 2815
Volts 6600 V
Amps 246 A
Phase 3
Frequency 50 Hz
Insulation Class-F
PF 0.8
Duty S1
IC 01
IP 23
RPM 1000
Exciter 110 V, 3.2 A (Brush – less of permanent magnet, electronic
automatic voltage regulator)
Ambient temp 50°C
NGR specification
Resistance at 20°C 95.3Ω
Voltage 6.6 kV/√3
Insulation class 7.2 kV
Transient current 40 A / second.
Continuous rating 10 Amps.
• What is the operational requirement of DG’s?
1. Whenever class IV fails DG sets (2 + 1 standby) are started by EMTR and capable
of restoring class III loads within 30 Seconds. One example is given below.
Event Minutes Seconds Milli seconds Difference
Class IV fail 00 00 280 00:00:280
EMTR initiate 00 01 303 00:01:023
DG start (1, 2, 3) 00 01 336 00:00:033
Voltage, Speed reached 00 07 257 00:05:921
CB 351, 361, 370 Closed 00 07 491 00:00:234
Restoration will be done in 07 seconds and 491 milli seconds. After this to build up
power and frequency it takes about 1 minute 26 seconds and 852 milli seconds. Then
load restoration starts as per EMTR scheme.
2. DG’s are capable of paralleling with 6.6 kV class IV supplies.
3. DG’s are capable of paralleling with each other.
• What are the design criteria’s of DG’s?
1. 4000 starts and 4000 hrs run at full load for lifetime.
2. Operation at 45°C and high atmospheric condition.
3. Designed to run in earthquake and seismic condition.
4. Designed to start as per EMTR scheme and take load as per EMTR and load
shedding scheme in one-DG condition without drop in voltage or frequency 25%
and 5% respectively.
5. Designed for run in high speed and to build up voltage and speed within 10
seconds.
6. Designed to start and loading with external row water for cooling for 3 minutes.
7. Designed to start at normal and load condition temperature.
8. Designed to run at no load for 4 hrs in a 4 months with affecting the load and over
load.
9. Designed to supply power in one-DG condition.
10. Continuous supply is 2250 kW and can run at 2475 kW for 2 hrs in 24 hrs at 6.6
kV and 0.8 PF.
11. Designed to start and stop at 48 V DC supply and stop at 220 V DC in the case of
48 V DC is not available.
12. DG – 3 is physically separated for control and installed at adjacent unit. Because
in case of unit is not avail then for cooling water is available in other unit.
13. Monorail of 3 Ton is provided.
14. Provisions are made for filtered air and ventilation and combustion.
15. Co2 fire fighting system is provided for smoothening effect in case of fire.
16. Active process water from class III is provided.
• What are the auxiliaries required for DG?
1. Starting air system.
Components are compressor, air dryer, air receiver, solenoid valve for start
control, pneumatic starting air valve, air distributor and injection valve at each
cylinder.
This system operates at high pressure and also provided with soft start of 8-bar
pressure in testing of system periodically.
2. Lub oil system.
This is closed loop of having oil sump of capacity of 7 days at full load. This also
supplies oil to bearing lubrication, crankshaft, piston, and wiper.
This closed loop Circuit includes pre-lubricating circuit and normal lubricating
circuit. Pre- lubricating circuit is controlled by PLC, but at first commissioning
and overhauling pre-lub start immediately.
3. Water cooling system.
This is provided with closed loop fresh water for remove heat from lubricating oil
system, charge air cooler, engine components (cylinder lines, cylinder head etc).
Fresh water chemistry is controlled to avoid organic growth and corrosion. This
water is heated for normal operation to avoid thermal shock. This water is cooled
by active process water. One tank is provided to transfer fresh water to the
system. Before transferring fresh water chemical addition should be done.
4. Fuel oil system.
The engine driven fuel oil pump is flooded with fuel oil from the day tank by
gravity. Low-pressure fuel from fuel pump is supplied to individual injection
pump is injected to individual cylinders through injectors.
5. Combustion air and exhaust gas system.
The engine is supplied by compressed combustion air with the help of exhaust gas
driver Turbo – charger. Each bank cylinder is provided with a Turbo – charger.
Turbo – charger is provided with filters. The exhaust is passes through silencer.
6. Speed governing system.
Governer is hydraulic mechanical type. The governer is linked to the fuel racks.
The maximum work output of the UG – 8 governer is 8 lb – ft over the full 42°
travel. For full load 30°is sufficient and remaining for overloading.
Governer comprises
a. Speed droop setting.
b. Oil sight glass.
c. Load limiter
d. Compensation pointer and adjuster.
e. Local speed adjuster.
7. Two numbers of ventillation fans are provided in each DG building. One starts at
respective DG breaker close and other at >45°C. DG room is provided with 7
numbers of smoke detectors (ionized type) and 7 numbers of flame detectors
(photoelectric type).
8. Separate DG’s are having separate MCC for their auxiliaries power supply. For
DG – 1 auxiliaries MCC P1. For DG – 2 auxiliaries MCC Q1 and for DG – 3
MCC DG – 3 is provided.
9. Phase winding is provided with two RTD’s for hotspot measurement and bearing
provided with one RTD each.
10. LCP is provided one each for each DG.
• When DG’s start is not possible?
1. DG trip.
2. Turning gear engaged.
3. DG set stop push button pressed.
• What are stages of DG starting?
1. At start signal compressed air through solenoid valve passes over piston and
rotates the shaft.
2. At speed >60-rpm ignition starts.
3. Closing of excitation starts at >800-rpm.
4. At speed of > 900-rpm rated speed and rated voltage signal starts.
5. Closing of over speed is at >1150-rpm.
• What are the protections provided for DG?
1. Differential protection (87).
2. Over speed of engine.
3. Reverse power protection (in LOCA condition time delay).
4. Low lubricating oil pressure.
5. Cooling water temperature high.
6. 6.6 kV switchgear protections.
7. Excitation failure.
8. Emergency stops push button.
In LOCA condition 4 – 8 protections are not permitted to operate.
https://www.youtube.com/channel/UC4_D50vMu1wbQrPaLFYo6Eg https://www.youtube.com/channel/UC4_D50vMu1wbQrPaLFYo6Eg RRB JE, SSC AE/JE UPSSSC JE, SSC JE, CIVIL ENGINEERING MCQs, ELECTICAL ENGINEERING MCQs, preavious year quesion papers, dmrc, lmrc, drdo,rrb ntpc, ntpc, pgcil, dsssb, states board, GATE IES EE, ESE, ECE, ME, CE, IT & CS EXAM MATERIALS & OLD PAPERS Electrical Engineering https://t.me/pravendrarajpoot Daily news & current affairs in hindi & english fully updated Daily current affairs https://t.me/newsdailypkr Engineering Discussion group for your upcoming exams, you can ask your any query regarding your problem,👇👇👇 https://t.me/joinchat/JObxeA7n6S4qvnegrGhTgA PKR ELECTRICAL ENGINEERING I am sure this is the best place for you guys subscribe and get success IF YOU WANT TO JOIN ME ON TELEGRAM FOR PDF @newsdailypkr AE/JE EE, ESE, ECE, ME, CE, IT & CS EXAM MATERIALS & OLD PAPERS Electrical Engineering https://t.me/pravendrarajpoot facebook page:- Pravendra Kumar Rajpoot https://t.me/newsdailypkr https://chat.whatsapp.com/5AS7dNFTP4H4vVsiWsqHrT https://t.me/srk50 https://t.me/pravendrarajpoot https://t.me/joinchat/JObxeA7n6S4qvnegrGhTgA https://t.me/pravendrarajpoot Daily news & current affairs in hindi & english fully updated Daily current affairs https://t.me/newsdailypkr Engineering Discussion group for your upcoming exams, you can ask your any query regarding your problem,👇👇👇 https://t.me/joinchat/JObxeA7n6S4qvnegrGhTgA PKR ELECTRICAL ENGINEERING I am sure this is the best place for you guys subscribe and get success IF YOU WANT TO JOIN ME ON TELEGRAM FOR PDF @newsdailypkr AE/JE EE, ESE, ECE, ME, CE, IT & CS EXAM MATERIALS & OLD PAPERS Electrical Engineering https://t.me/pravendrarajpoot facebook page:- Pravendra Kumar Rajpoot https://t.me/newsdailypkr https://chat.whatsapp.com/5AS7dNFTP4H4vVsiWsqHrT https://t.me/srk50 https://t.me/pravendrarajpoot https://t.me/joinchat/JObxeA7n6S4qvnegrGhTgA
• What is meant by EMTR?
In case of normal supply failure to CL-III & CL-II the loads will be fed by the
alternative/standby sources. This changeover of supply is called Emergency
Transfer.
• How EMTR is initiated?
EMTR is initiated on sensing the CL-III & CL-II bus under voltage.
• What are the routes of EMTR?
CL-III bus under voltage. The DG’s will start. All the breakers connected to the
affected bus will trip. DG breaker will close on dead bus. Loads will be restored one
by one.
CL-II bus under voltage. The tie breaker of the affected bus will close.
• What does load-shedding mean?
When there is only one source to feed the two buses, the total loads can not be fed by
this single source. Hence some of the less important load will not be allowed to start
or it will be tripped if it is running.
• What does total load-shedding mean?
Even after the load shedding the is continue to deliver more than the rated power
sensed by overpower relay or running with under frequency sensed by the under
frequency relay the total load shedding will take place. In case of auxiliary
transformer is feeding the total load shedding will take place after 4 minutes.
• What does auto transfer mean?
If one of the sources is tripped on main protection its breaker will be tripped and the
tie-breaker will close. This transfer of supply from one source to other source is
called auto transfer. To restore the class IV whenever the UT or SUT is lost Auto
transfer is provided.
• Why auto transfer is prevented if the backup protection is operated?
The back up protection is supposed to operate in case of a bus fault. Hence the auto
transfer is prevented.
• What are the types Auto transfer scheme?
1. Fast transfer scheme to close the tie-breaker in less than 200 milli seconds. This
limits transient current and voltage dip in the bus and does quick acceleration of
the motors.
2. Slow transfer after 200 milli seconds.
• What are the conditions for Auto transfer scheme?
Backup protections are not allowed to initiate the Auto transfer. Because under
voltage may exist in the bus. Similarly protection in LV of the transformers are not
initiating the Auto transfer scheme. There are three metrics used in Auto transfer
scheme and 2/3 logic is adopted.
Conditions
1. Fault generator (86BG or 86A1).
2. Fault in UT.
3. Fault in GT.
4. Fault in 220 kV bus (SUT).
5. Fault in SUT (86M).
• What are the uses of EMTR scheme?
1. To restore class III when class IV supply fails.
2. To extend supply to class II when UPS fails.
3. In one DG condition to load restoration.
4. Sub sequent restoration of large motor loads.
• What are the sequences of motor load restoration in EMTR?
1. AHPPW –1001 - 4 Sec.
2. APWC – 1003 - 8 Sec.
3. APWC – 1004 - 12 Sec.
4. AHPPW –1002 - 16 Sec.
5. PPP – 1001 - 20 Sec.
6. MOD – 1002 - 24 Sec.
7. MOD – 1001 - 28 Sec.
8. Air Comp – 1002 - 32 Sec.
9. ABFP – 1006 - 36 Sec.
10. 7343 Exst Fan 1003 - 40 Sec.
11. ECCS PM 1001 - 44 Sec.
12. ECCS PM 1002 - 48 Sec.
• Why synchronizing scheme has been adopted? What are interlocks provided?
To check running and incoming buses, which are going to be interconnected are in
synchronism with each other.
Interlocks
1. Synch selector.
2. Only one breaker can operate at a time.
3. Master synch relay contact should available (bypass will bypass this synch
contact).
Bypass facility is provided to close the breaker on dead bus only.
• What are the settings provided in synchronizing scheme (SKE Relay)?
Voltage – V1- V2 = 10%
Frequency – t = 0.05 Sec (2.5 Hz)
% Slip – 0.45
Phase angle difference - 20°.
• What are the major losses in nuclear power generating system?
Condenser - 500 MW.
Moderator - 40 MW.
C/V and E/S system - 3.7 MW.
• Give the specification of DG and NGR of DG.
DG specification
Type HSPTL 12/653 synchronous generator.
KVA 2815
Volts 6600 V
Amps 246 A
Phase 3
Frequency 50 Hz
Insulation Class-F
PF 0.8
Duty S1
IC 01
IP 23
RPM 1000
Exciter 110 V, 3.2 A (Brush – less of permanent magnet, electronic
automatic voltage regulator)
Ambient temp 50°C
NGR specification
Resistance at 20°C 95.3Ω
Voltage 6.6 kV/√3
Insulation class 7.2 kV
Transient current 40 A / second.
Continuous rating 10 Amps.
• What is the operational requirement of DG’s?
1. Whenever class IV fails DG sets (2 + 1 standby) are started by EMTR and capable
of restoring class III loads within 30 Seconds. One example is given below.
Event Minutes Seconds Milli seconds Difference
Class IV fail 00 00 280 00:00:280
EMTR initiate 00 01 303 00:01:023
DG start (1, 2, 3) 00 01 336 00:00:033
Voltage, Speed reached 00 07 257 00:05:921
CB 351, 361, 370 Closed 00 07 491 00:00:234
Restoration will be done in 07 seconds and 491 milli seconds. After this to build up
power and frequency it takes about 1 minute 26 seconds and 852 milli seconds. Then
load restoration starts as per EMTR scheme.
2. DG’s are capable of paralleling with 6.6 kV class IV supplies.
3. DG’s are capable of paralleling with each other.
• What are the design criteria’s of DG’s?
1. 4000 starts and 4000 hrs run at full load for lifetime.
2. Operation at 45°C and high atmospheric condition.
3. Designed to run in earthquake and seismic condition.
4. Designed to start as per EMTR scheme and take load as per EMTR and load
shedding scheme in one-DG condition without drop in voltage or frequency 25%
and 5% respectively.
5. Designed for run in high speed and to build up voltage and speed within 10
seconds.
6. Designed to start and loading with external row water for cooling for 3 minutes.
7. Designed to start at normal and load condition temperature.
8. Designed to run at no load for 4 hrs in a 4 months with affecting the load and over
load.
9. Designed to supply power in one-DG condition.
10. Continuous supply is 2250 kW and can run at 2475 kW for 2 hrs in 24 hrs at 6.6
kV and 0.8 PF.
11. Designed to start and stop at 48 V DC supply and stop at 220 V DC in the case of
48 V DC is not available.
12. DG – 3 is physically separated for control and installed at adjacent unit. Because
in case of unit is not avail then for cooling water is available in other unit.
13. Monorail of 3 Ton is provided.
14. Provisions are made for filtered air and ventilation and combustion.
15. Co2 fire fighting system is provided for smoothening effect in case of fire.
16. Active process water from class III is provided.
• What are the auxiliaries required for DG?
1. Starting air system.
Components are compressor, air dryer, air receiver, solenoid valve for start
control, pneumatic starting air valve, air distributor and injection valve at each
cylinder.
This system operates at high pressure and also provided with soft start of 8-bar
pressure in testing of system periodically.
2. Lub oil system.
This is closed loop of having oil sump of capacity of 7 days at full load. This also
supplies oil to bearing lubrication, crankshaft, piston, and wiper.
This closed loop Circuit includes pre-lubricating circuit and normal lubricating
circuit. Pre- lubricating circuit is controlled by PLC, but at first commissioning
and overhauling pre-lub start immediately.
3. Water cooling system.
This is provided with closed loop fresh water for remove heat from lubricating oil
system, charge air cooler, engine components (cylinder lines, cylinder head etc).
Fresh water chemistry is controlled to avoid organic growth and corrosion. This
water is heated for normal operation to avoid thermal shock. This water is cooled
by active process water. One tank is provided to transfer fresh water to the
system. Before transferring fresh water chemical addition should be done.
4. Fuel oil system.
The engine driven fuel oil pump is flooded with fuel oil from the day tank by
gravity. Low-pressure fuel from fuel pump is supplied to individual injection
pump is injected to individual cylinders through injectors.
5. Combustion air and exhaust gas system.
The engine is supplied by compressed combustion air with the help of exhaust gas
driver Turbo – charger. Each bank cylinder is provided with a Turbo – charger.
Turbo – charger is provided with filters. The exhaust is passes through silencer.
6. Speed governing system.
Governer is hydraulic mechanical type. The governer is linked to the fuel racks.
The maximum work output of the UG – 8 governer is 8 lb – ft over the full 42°
travel. For full load 30°is sufficient and remaining for overloading.
Governer comprises
a. Speed droop setting.
b. Oil sight glass.
c. Load limiter
d. Compensation pointer and adjuster.
e. Local speed adjuster.
7. Two numbers of ventillation fans are provided in each DG building. One starts at
respective DG breaker close and other at >45°C. DG room is provided with 7
numbers of smoke detectors (ionized type) and 7 numbers of flame detectors
(photoelectric type).
8. Separate DG’s are having separate MCC for their auxiliaries power supply. For
DG – 1 auxiliaries MCC P1. For DG – 2 auxiliaries MCC Q1 and for DG – 3
MCC DG – 3 is provided.
9. Phase winding is provided with two RTD’s for hotspot measurement and bearing
provided with one RTD each.
10. LCP is provided one each for each DG.
• When DG’s start is not possible?
1. DG trip.
2. Turning gear engaged.
3. DG set stop push button pressed.
• What are stages of DG starting?
1. At start signal compressed air through solenoid valve passes over piston and
rotates the shaft.
2. At speed >60-rpm ignition starts.
3. Closing of excitation starts at >800-rpm.
4. At speed of > 900-rpm rated speed and rated voltage signal starts.
5. Closing of over speed is at >1150-rpm.
• What are the protections provided for DG?
1. Differential protection (87).
2. Over speed of engine.
3. Reverse power protection (in LOCA condition time delay).
4. Low lubricating oil pressure.
5. Cooling water temperature high.
6. 6.6 kV switchgear protections.
7. Excitation failure.
8. Emergency stops push button.
In LOCA condition 4 – 8 protections are not permitted to operate.
https://www.youtube.com/channel/UC4_D50vMu1wbQrPaLFYo6Eg https://www.youtube.com/channel/UC4_D50vMu1wbQrPaLFYo6Eg RRB JE, SSC AE/JE UPSSSC JE, SSC JE, CIVIL ENGINEERING MCQs, ELECTICAL ENGINEERING MCQs, preavious year quesion papers, dmrc, lmrc, drdo,rrb ntpc, ntpc, pgcil, dsssb, states board, GATE IES EE, ESE, ECE, ME, CE, IT & CS EXAM MATERIALS & OLD PAPERS Electrical Engineering https://t.me/pravendrarajpoot Daily news & current affairs in hindi & english fully updated Daily current affairs https://t.me/newsdailypkr Engineering Discussion group for your upcoming exams, you can ask your any query regarding your problem,👇👇👇 https://t.me/joinchat/JObxeA7n6S4qvnegrGhTgA PKR ELECTRICAL ENGINEERING I am sure this is the best place for you guys subscribe and get success IF YOU WANT TO JOIN ME ON TELEGRAM FOR PDF @newsdailypkr AE/JE EE, ESE, ECE, ME, CE, IT & CS EXAM MATERIALS & OLD PAPERS Electrical Engineering https://t.me/pravendrarajpoot facebook page:- Pravendra Kumar Rajpoot https://t.me/newsdailypkr https://chat.whatsapp.com/5AS7dNFTP4H4vVsiWsqHrT https://t.me/srk50 https://t.me/pravendrarajpoot https://t.me/joinchat/JObxeA7n6S4qvnegrGhTgA https://t.me/pravendrarajpoot Daily news & current affairs in hindi & english fully updated Daily current affairs https://t.me/newsdailypkr Engineering Discussion group for your upcoming exams, you can ask your any query regarding your problem,👇👇👇 https://t.me/joinchat/JObxeA7n6S4qvnegrGhTgA PKR ELECTRICAL ENGINEERING I am sure this is the best place for you guys subscribe and get success IF YOU WANT TO JOIN ME ON TELEGRAM FOR PDF @newsdailypkr AE/JE EE, ESE, ECE, ME, CE, IT & CS EXAM MATERIALS & OLD PAPERS Electrical Engineering https://t.me/pravendrarajpoot facebook page:- Pravendra Kumar Rajpoot https://t.me/newsdailypkr https://chat.whatsapp.com/5AS7dNFTP4H4vVsiWsqHrT https://t.me/srk50 https://t.me/pravendrarajpoot https://t.me/joinchat/JObxeA7n6S4qvnegrGhTgA
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