✔ Take line 2 out of service at time 0.1 Sec and enter it again at time 0.6 Sec.
8- How much is the output power of generator GEN at time 0.8 Sec?
MW + j MVAR
✔ Make a THREE PHASE fault at bus GEN such that it will be established at time 0.1 Sec and consequent will be removed at time 0.3 Sec automatically.
9- How much is the output active power of generator GEN at times 0.1 & 0.5 Sec?
At 0.1 Sec MW (exactly before fault) and at 0.5 Sec MW.
10- Refer to lecture notes and find the values requested:
✔ Repeat the above instruction as the fault will be cleared by breaking line 2.
11- How much is the output active power of generator GEN at times 0.1 & 0.5 Sec?
At 0.1 Sec MW (exactly before fault) and at 0.5 Sec MW.
12- Refer to lecture notes and find the values requested:
✔ Repeat the above instruction as the fault is at 20% from the beginning of line 2 and will be cleared by breaking line 2.
13- How much is the output active power of generator GEN at times 0.1 & 0.5 Sec?
At 0.1 Sec MW (exactly before fault) and at 0.5 Sec MW.
14- Refer to lecture notes and find the values requested:
✔ Repeat the above instruction as the load power is 400 MW + j400 MVAR.
15- How much is the output active power of generator GEN at times 0.1 & 0.5 Sec?
At 0.1 Sec MW (exactly before fault) and at 0.5 Sec MW.
16- Refer to lecture notes and find the values requested:
SECTION A-1
✔ This Section needs to be familiar with PASHA, skip the Section if the teacher ask to do so.
17- Does the generator remain stable? Check both angle in TRANSIENT STABILITY and frequency in FREQUENCY DYNAMICs.
Yes No
18- Has the angle not changed because it is using the GEN as reference machine?
Yes No
19- Put the value zero for reference machine busbar name (USE THE SYSTEM REFERENCE) and run TRANSIENT STABILITY, has the angle changed?
Yes No
20- Why doesn’t PASHA continue to the calculations?
Due to activating some protective devices.
Zero pivot occurred during BI-factorization at busbar.
Due to exceeding from the defined POLE SLIP limit.
Due to ill-conditioning of Y-bus consequent of some switching states.
✔ Bring LAB.NO05 A-1 out of the file again and simulate it in PASHA & answer the following QUESTIONS.
21- Why did the generator remain stable, at least until 5 Sec?
Because we have add some MW and MVAR.
Because we have add some MVAR.
Because the load model is impedance constant, and adding MVAR will cause the voltage decreases and the load will decrease.
Because the load model is constant power, and adding MVAR will cause the voltage increase and the load will decrease.
22- How much is the supplying power of the generator after a long run? Think why it is constant.
MW + j MVAR
✔ Bring LAB.NO05 A-1 out of the file again and simulate it in PASHA & answer the following QUESTIONS.
23- Why did the generator become unstable?
Because AVR regulated the voltage such that the load impedance has increased.
Because AVR regulated the voltage such that the load impedance has decreased.
Because AVR has an oscillatory action, causes the system go to unstable situation.
Because AVR has removed the damping effect on generator.
✔ Assign a 15 type GOVERNOR from database DB4 to the generator too.
24- Why did the generator become stable?
Because of the GOVERNOR action.
Because the interaction between AVR and GOVERNOR.
Both of the above.
None of the above.
✔ The above results show the vital rule of simulations in planning and operation of POWER NETWORKs.
SECTION A-2
✔ This Section needs to be familiar with PASHA, skip the Section if the teacher ask to do so.
25- How much is the motor starting time? If it is needed add the time of simulation.
Sec
26- How much is the starting current?
p.u
27- Why does the load torque vary with time?
Because it is defined as a Fan by specifying C in MOTOR DATA PAGE 2 as 1.0.
Because it is defined as a Reciprocating Pump by specifying C in MOTOR DATA PAGE 2 as 1.0.
Due to the high inertia constant of the motor.
Due to changing electrical power.
✔ Applying the mechanical power 6 MW on the motor.
28- How much is the motor starting time? Sec.
✔ Bring LAB.NO05-A-2 out of the file again.
29- How much is the motor starting time? If it is needed add the time of simulation.
Sec
30- How much is the starting current?
p.u
31- Set the transformer tap such that the best starting time and the minimum voltage dropping at generator bus will be geted
How much is this tap setting value? (Maximum of the motor tolerable voltage is 1.05 p.u) %
SECTION B
✔ Bring LAB.NO05-C out of the file and simulate it in POUYA and remember that the system base is 100 MVA.
✔ This shows a 1200 MW generators (equivalent of six 200MW generators represented as one generator producing about 1200 MW) connected to the infinite busbar (a large network) through three lines.
✔ ALWAYS USE THE LAST UPDATED POUYA and answer the following QUESTIONs
✔ Note: you need to get access to the controllers of the generator by pressing key T while mouse is find on upper part or lower part of the generator symbols.
32- Open the transformer between GENJ and GEN, How long it takes the turbine stops? Sec. Calculate the DAMPING FACTOR (D in note). pu.
33- Open lines between GEN and NET1 and GEN and NET3 somehow that only the middle line maintains between the generation station and the infinite busbar:
Power station settles down at a stable situation.
Power station frequency exceed 54 Hz and so over speed will act and shut downs the generation station.
Over frequency relay with that has the setting 52 Hz and 1 Second opens the unit transformer.
We will have a Black Out.
34- how long it takes the turbine stops. Sec.
✔ If you are required to plot the frequency of the generator terminal, put the cursor on related junction and press P to plot and select frequency.
✔ Note that "INHIBIT ALL THE RELAY ACTIONS at this run" is unchecked.
35- In the experience you have gained:
Over frequency relay opens the transformer.
Power station frequency goes above 52 Hz but the frequency relay does not operate because of its setting which is 1 Second.
Generator terminal frequency does not goes behind 52 Hz since it is connected to the grid.
Generator terminal frequency goes behind 52 Hz over 1 Second time but the over speed unexpectedly shut downs the generation station.
36- If this is an unstable situation we call it:
Transient instability.
Steady state instability.
Dynamic instability.
Both 1 and 2 are true.
37- Under voltage relay (that has a setting of 0.8 pu with time 10000 mSec and WATCH DOGS the terminal voltage of the generator):
Does not operate.
Operates before the over speed.
Operates because the field has been opened due to the plant shut down.
Operates because the terminal voltage can not be maintained by its AVR.
38- Over frequency relay (That has a setting of 52 Hz with time 1000 mSec and WATCH DOGS the terminal voltage of the generator):
Does not operate.
Operates after the over speed.
Operates because the frequency goes down.
Operates before overspeed because the frequency goes up.
39- Reset all the relays by pressing key S (remember that this also affect the reference governor values and put tthem to their original position) , why under voltage relay operates:
During the shut done AVR reference voltage has become near to zero.
Program error.
After the shut done the voltage is still low the AVR time constants must be brought up, if this is the case we usually bring the time constants up.
After the shut done the voltage is still low before resetting the relays we need to bring the reference up, if this is the case we usually bring the reference up.
40- Bring the AVR reference up, is it possible to connect the CB of the transformer (in actual operation of the network):
No because of excess voltage in the busbar GEN.
Yes it can be closed after synchronisation.
If a synchronize relay present we can always connect it.
Yes it can always be closed.
41- Bring the AVR reference up, is it possible to connect the CB of the transformer (with simulation program):
No because of excess voltage in the busbar GEN.
Yes it can be closed after synchronisation.
If a synchronize relay present we can always connect it.
Yes it can always be closed.
42- What action we need to do before closing the CB:
We need to bring down the voltage of GEN using AVR of the grid generators.
We need to bring down the voltage of GEN using the transformer tap setting.
We need to bring up the voltage of generator terminal to about 1.12 pu.
We need to close the line in outages.
43- I have succeeded to bring the generator in service by:
Closing the outage lines and bringing up the reference voltage, setting the transformer taps, and closing the CB always.
Closing the outage lines and bringing up the reference voltage, setting the transformer taps, and closing the CB sometimes.
Closing the outage lines, setting the transformer taps, and closing the CB always.
Closing the outage lines, setting the transformer taps, and closing the CB three times.
44- In the previous trials:
Always i succeeded to close the CB.
Some times i succeeded and sometimes a relay operates.
All trial were unsuccessful.
The generator can not be synchronized because the synchronous relay is not present.
45- In the previous trials:
I can bring the network to the original state by changing the GOVERNOR reference.
I can not bring the network to its original state.
Network will go to its original state after closing CB.
I need more control to bring the network to its original state.
SECTION C
✔ Bring the LARGE-SCALE typical network out of the file and remember that the system base is 100 MVA.
✔ Answer the same as above QUESTIONs brought below for power generation station in ASALOYEH.
✔ Note: you need to get access to the controllers of the generator by pressing key T while mouse is find on upper part or lower part of the generator symbols.
✔ Zoom on the generation station (press Z on FARS and then press Z on an area surrounding ASFBGEA), press V and enter 1.6 and select option apply in associated area.
✔ Now click on upper part of one of the generator symbols, these actions bring the generator turbine power to 160 MW.
46- Why the generators power output is not 160 MW.
Because of the generator loss.
Because of the AVR action error.
Because of the GOVERNOR action error.
Because of program error.
47- Open one of the unit transformer. How long it takes the turbine comes to half a speed? Sec. Calculate the DAMPING FACTOR (D in note). pu.
✔ Bring the network out of the file again and remember that the system base is 100 MVA then answer the following QUESTIONs.
48- Open the lines ASFBGEA to LAFBDDI and ASFBGEA to FAEHAGA somehow that only one line maintains between the generation station and the network:
Power station settles down at a stable situation.
Power station frequency exceed 54 Hz and so over speed will act and shut downs the generation station.
Over frequency relay with that has the setting 52 Hz and 1 Second opens the unit transformer.
We will have a BLACK OUT.
49- Select one of the below:
Excitation opened and short circuited through a resistor.
Excitation opened.
GOVERNOR mechanical power instantaneously dropped to zero.
GOVERNOR reference frequency instantaneously dropped to zero.
50- If this is an unstable situation we call it:
Transient instability.
Steady state instability.
Dynamic instability.
Both 1 and 2 are true.
51- Under voltage relay in this power station (that has a setting of 0.9 pu with time 6000 mSec and WATCH DOGS the terminal voltage of the generator and Note that the under voltage blocking unit has a setting of 0.7 pu.):
Does not operate.
Operates before the over speed.
Operates because the field has been opened due to the plant shut down.
Operates because the terminal voltage can not be maintained by its AVR.
52- Over frequency relay (That has a setting of 52 Hz with time 1000 mSec and WATCH DOGS the terminal voltage of the generator):
Does not operate.
Operates before the over speed.
Operates after the over speed because the frequency goes down.
Operates after the over speed because the frequency goes up.
53- Reset all the relays by pressing key S, why under voltage relay operates (Note that over speed did not reset and you should wait for damping of oscillations):
During the shut done AVR reference voltage has become zero.
Program error.
After the shut done the voltage is still low the AVR time constants must be brought up. if this is the case we usually bring the time constants up.
After the shut done the voltage is still low before resetting the relays we need to bring the reference up. if this is the case we usually bring the reference up.
54- Bring the AVR reference up, is it possible to connect the CB of the transformer (in actual operation of the network):
No because of excess voltage in the network 400 kV busbar.
Yes it can be closed after synchronisation.
If a synchronize relay present we can always connect it.
Yes it can always be closed.
55- Bring the AVR reference up, is it possible to connect the CB of the transformer (with simulation program):
No because of excess voltage in the busbar GEN.
Yes it can be closed after synchronisation.
If a synchronizer relay present we can always connect it.
Yes it can always be closed.
56- What action we need to do before closing the CB:
We need to bring down the voltage of GEN using AVR of the grid generators.
We need to bring down the voltage of GEN using the transformer tap setting.
we need to bring up the voltage of generator terminal to about 0.97 pu.
we need to close the line in outages.
57- I have succeeded to bring the generators in service by:
Closing the outage lines and bringing up the reference voltage, setting the transformer taps, and closing the CB always.
Closing the outage lines and bringing up the reference voltage, setting the transformer taps, and closing the CB sometimes.
Closing the outage lines, setting the transformer taps, and closing the CB always.
Closing the outage lines, setting the transformer taps, and closing the CB three times.
58- In the previous trials:
Always I succeeded to close the CB.
Some times I succeeded and sometimes a relay operates.
All trial were unsuccessful.
The generator can not be synchronized because the synchronous relay is not present.
59- In the previous trials:
I can bring the network to the original state by changing the GOVERNOR reference.
I can not bring the network to its original state.
Network will go to its original state after closing CB.
I need more control to bring the network to its original state.
✔ Press O and then press any click to start simulation as it is started from origin.
60- One other generation station will be disconnected, this is :
BOFBMMA.
SHBH1EB.
SHBH4EE.
No generator will be disconnected.
61- This is mainly because of:
Under voltage.
Over voltage.
Under frequency.
Over frequency.
62- Try again and this time try to prevent this generator to disconnect:
I have succeeded to prevent the generation station goes out by changing AVR.
I have succeeded to prevent the generation station goes out by changing GOVERNOR.
I have succeeded to prevent the generation station goes out by changing transformer taps.
It can not be prevented .
SECTION D
63- Teacher simulates and offer some contingencies in the network, he/she will raise some QUESTIONs, answer the teacher QUESTIONs in a separate sheet and pass it to the teacher.