A
Hi all,
<b>Background:</b> I hold a bachelor's degree in Mechanical Engineering and currently assigned as maintenance engineer (by a natural gas transmission company) of electric generators operating in Island mode. Also worked one year in a fertilizer plant.
<b>Information Regarding System:</b> We have caterpillar 3516A generators capacity 635KW, 1000 RPM, installed at our company remote stations which operate around the clock to provide continuous power to whole station. They operate in island mode and one generator at a time, so we are used to fight the hunting and frequency variation issues, but few months back at one station which also has small residential colony it was decided by management to connect it to generator supply. Colony require around 250KW power which is arrange by a separate department Colony Power House (CPH) from Utility Power, so final conclusion was to provide 80KW power to one portion of colony. The power lines to colony were already divided as 3 wires for 3 phases for normal load (Lighting Load) and 3 wires for 3 phases for Air Conditioners Load (Power Load), this arrangement existed because we have frequent power outages here and colony power house have small generators to provide lighting load to colony. Previously when Utility Power was available whole load was on utility power , both lighting and power load, but when utility power was out only lighting load was being supplied by stand by generator. But now the power to the Lighting Load is being supplied from the Caterpillar Gas Generator continuously and Power Load is on Utility Power which goes out with power outage by Utility company for few hours each day on random hours.
<b>Problem:</b> We are having voltage fluctuations from 10 volt to 30 volt (was more severe till power house people did some load balancing) , and this fluctuation is per 1 sec to 5 sec, and resulted so far my ups burning out and two other colony engineers refrigerators compressor burn out (and more I think which I am not aware).
So I set out to find the solution being that power was supplied from generator under my department, The Caterpillar 3516A has Terberg Control System (sorry don't have details about it, don't have documents at home) but it was installed in 2006 and has very good control over generator RPM. I went to the station and there was no fluctuation in generator RPM (3-4RPM can be ignored) and neither was voltage fluctuation(Both Phase to Phase and Phase to Neutral) so I came to our office near residential colony from where the Colony Power house took the connection and found there was no voltage fluctuation in the main bus there either and when I went to Colony Power house I found that there was no Phase to Phase Fluctuation but there was a high Phase to Neutral Fluctuation, when CPH (Colony Power House) personnel were informed they said they will look into it and did load balancing on phases as mentioned earlier this resulted in reduction of voltage range fluctuation i.e., from 30 to 40 volt down to 10 to 20 sometimes 30 volt now, but not reduced the problem with fluctuation frequency. (My frequent debates with CPH personnel resulted in my knowledge gain a lot since I am novice on the Electric Power Systems and one even joked what degree I have >_< ) So I went online and studied forums etc and all this knowledge resulted in me to following findings
1. The Neutral of the generator and Utility Power is tied to one cable (since there is only one neutral to colony)
2. Each Home is provided with one phase from Power Load for ACs and one phase from Lighting Load for normal use, but with one Neutral
3. There is 10 volt in Neutral Wire with reference to ground or Earth wire when there is no Utility Power and no fluctuation in voltage in either Neutral to Ground , Lighting Phase to Neutral or Lighting Phase to Ground
4. When Utility Power is supplied too, the Voltage in Neutral Wire Jump to 20 - 30 volt w.r.t ground, and it constantly fluctuates from 0 Volt to 30 Volt sometimes up to 40 when fluctuations are severe. There is around 5 Volts at Most in Power phase to Ground and around same with Lighting Phase to Ground.
5. The Voltage between Lighting Phase and Power Phase fluctuate from 0 Volt to 400 Volt per 1 sec to 3 sec, sometimes is faster and sometimes is slower and brief constant voltage at one random voltage for like few millisecond. (I use analog needle volt meter , pretty old but pretty robust)
6. There is no Voltage fluctuation or very little as compare to Lighting phase to Neutral. if the fluctuation range was 20-30 volt for Lighting phase to neutral for power phase it was 5-10volt and less fluctuation (little confusing because there was 10-20 volt fluctuation in neutral to ground)
7. The fluctuation persisted till Utility Power was online and when Utility power was out the Lighting Phase voltage were stable Phase to Neutral and Phase to Ground both
All these findings resulted in me reaching the conclusion that since generator and the Utility are not synchronized it results in out of phase angle whenever engine speed up or slows down to maintain its speed to maintain its RPM which result in current and thus voltage in neutral wire and since the angle varies with engine speed change so is the voltage in neutral as angle goes in and out of sync. When I represented these findings to colony power house personnel they rejected that it has anything to do with the Common Neutral Wire.
<b>Questions: </b>
1. Am I correct in assuming that it's the common neutral wire between generator and the Utility Power causing the problem ?
2. Since our company has long procedure for approvals and management sanctions for procurement it's not easy to get hands on to make generator synchronize with Utility (and an experienced person in power generation told me its pain to maintain it especially when Utility power is going out every few hours) , Our generator has a digital Synchronizer installed in its Panel, So is it possible to use a say 20KW transformer with breaker in transformer to utility lines and then to synchronize the generator with utility through that transformer with a simple reverse power circuit which will disconnect it when Utility goes out and not much load on generator (since transformer will limit it to 40KW jump) even it takes few mili seconds for reverse power circuit to detect it (Genset power is 635KW and its usually at 250KW at night and 450KW at day when offices are open) and generator can synchronize again automatically with remote command when Utility restores
3. Will Using a three Phase to Single Phase transformer on the Generator supply and then feeding it into colony supply on Lighting load wires result in reduce voltage fluctuation since I think it is due to Power and Lighting phases going out and in of sync and causing voltages in Neutral wire, assuming we use one phase wire from three wires for 3 phases as neutral along with original neutral wire to carry the current for the single phase system and the two wires from those 3 wires for phases to provide single phase, and assuming wires can handle such load
4. Just go the old fashion way, Switch both Lighting and Power Phases to the Utility Power and Switch Lighting load to Generator when Utility goes out, (not very interested because I live in Pakistan and we have sever power outage issues, brown outs every few hours for 2 to 4 hours)
I am really stuck in a bind as to find a solution without spending much money because it will take over a year to get sanction any solution requiring more than 1000Euro from management, Any Input regarding a mistake I am making in assuming why there is a fluctuation in system, I will really appreciate any help.
If you can point me to a thread of forum dealt with same issue , I will be thankful for it too.
Thank you for your time
<b>Background:</b> I hold a bachelor's degree in Mechanical Engineering and currently assigned as maintenance engineer (by a natural gas transmission company) of electric generators operating in Island mode. Also worked one year in a fertilizer plant.
<b>Information Regarding System:</b> We have caterpillar 3516A generators capacity 635KW, 1000 RPM, installed at our company remote stations which operate around the clock to provide continuous power to whole station. They operate in island mode and one generator at a time, so we are used to fight the hunting and frequency variation issues, but few months back at one station which also has small residential colony it was decided by management to connect it to generator supply. Colony require around 250KW power which is arrange by a separate department Colony Power House (CPH) from Utility Power, so final conclusion was to provide 80KW power to one portion of colony. The power lines to colony were already divided as 3 wires for 3 phases for normal load (Lighting Load) and 3 wires for 3 phases for Air Conditioners Load (Power Load), this arrangement existed because we have frequent power outages here and colony power house have small generators to provide lighting load to colony. Previously when Utility Power was available whole load was on utility power , both lighting and power load, but when utility power was out only lighting load was being supplied by stand by generator. But now the power to the Lighting Load is being supplied from the Caterpillar Gas Generator continuously and Power Load is on Utility Power which goes out with power outage by Utility company for few hours each day on random hours.
<b>Problem:</b> We are having voltage fluctuations from 10 volt to 30 volt (was more severe till power house people did some load balancing) , and this fluctuation is per 1 sec to 5 sec, and resulted so far my ups burning out and two other colony engineers refrigerators compressor burn out (and more I think which I am not aware).
So I set out to find the solution being that power was supplied from generator under my department, The Caterpillar 3516A has Terberg Control System (sorry don't have details about it, don't have documents at home) but it was installed in 2006 and has very good control over generator RPM. I went to the station and there was no fluctuation in generator RPM (3-4RPM can be ignored) and neither was voltage fluctuation(Both Phase to Phase and Phase to Neutral) so I came to our office near residential colony from where the Colony Power house took the connection and found there was no voltage fluctuation in the main bus there either and when I went to Colony Power house I found that there was no Phase to Phase Fluctuation but there was a high Phase to Neutral Fluctuation, when CPH (Colony Power House) personnel were informed they said they will look into it and did load balancing on phases as mentioned earlier this resulted in reduction of voltage range fluctuation i.e., from 30 to 40 volt down to 10 to 20 sometimes 30 volt now, but not reduced the problem with fluctuation frequency. (My frequent debates with CPH personnel resulted in my knowledge gain a lot since I am novice on the Electric Power Systems and one even joked what degree I have >_< ) So I went online and studied forums etc and all this knowledge resulted in me to following findings
1. The Neutral of the generator and Utility Power is tied to one cable (since there is only one neutral to colony)
2. Each Home is provided with one phase from Power Load for ACs and one phase from Lighting Load for normal use, but with one Neutral
3. There is 10 volt in Neutral Wire with reference to ground or Earth wire when there is no Utility Power and no fluctuation in voltage in either Neutral to Ground , Lighting Phase to Neutral or Lighting Phase to Ground
4. When Utility Power is supplied too, the Voltage in Neutral Wire Jump to 20 - 30 volt w.r.t ground, and it constantly fluctuates from 0 Volt to 30 Volt sometimes up to 40 when fluctuations are severe. There is around 5 Volts at Most in Power phase to Ground and around same with Lighting Phase to Ground.
5. The Voltage between Lighting Phase and Power Phase fluctuate from 0 Volt to 400 Volt per 1 sec to 3 sec, sometimes is faster and sometimes is slower and brief constant voltage at one random voltage for like few millisecond. (I use analog needle volt meter , pretty old but pretty robust)
6. There is no Voltage fluctuation or very little as compare to Lighting phase to Neutral. if the fluctuation range was 20-30 volt for Lighting phase to neutral for power phase it was 5-10volt and less fluctuation (little confusing because there was 10-20 volt fluctuation in neutral to ground)
7. The fluctuation persisted till Utility Power was online and when Utility power was out the Lighting Phase voltage were stable Phase to Neutral and Phase to Ground both
All these findings resulted in me reaching the conclusion that since generator and the Utility are not synchronized it results in out of phase angle whenever engine speed up or slows down to maintain its speed to maintain its RPM which result in current and thus voltage in neutral wire and since the angle varies with engine speed change so is the voltage in neutral as angle goes in and out of sync. When I represented these findings to colony power house personnel they rejected that it has anything to do with the Common Neutral Wire.
<b>Questions: </b>
1. Am I correct in assuming that it's the common neutral wire between generator and the Utility Power causing the problem ?
2. Since our company has long procedure for approvals and management sanctions for procurement it's not easy to get hands on to make generator synchronize with Utility (and an experienced person in power generation told me its pain to maintain it especially when Utility power is going out every few hours) , Our generator has a digital Synchronizer installed in its Panel, So is it possible to use a say 20KW transformer with breaker in transformer to utility lines and then to synchronize the generator with utility through that transformer with a simple reverse power circuit which will disconnect it when Utility goes out and not much load on generator (since transformer will limit it to 40KW jump) even it takes few mili seconds for reverse power circuit to detect it (Genset power is 635KW and its usually at 250KW at night and 450KW at day when offices are open) and generator can synchronize again automatically with remote command when Utility restores
3. Will Using a three Phase to Single Phase transformer on the Generator supply and then feeding it into colony supply on Lighting load wires result in reduce voltage fluctuation since I think it is due to Power and Lighting phases going out and in of sync and causing voltages in Neutral wire, assuming we use one phase wire from three wires for 3 phases as neutral along with original neutral wire to carry the current for the single phase system and the two wires from those 3 wires for phases to provide single phase, and assuming wires can handle such load
4. Just go the old fashion way, Switch both Lighting and Power Phases to the Utility Power and Switch Lighting load to Generator when Utility goes out, (not very interested because I live in Pakistan and we have sever power outage issues, brown outs every few hours for 2 to 4 hours)
I am really stuck in a bind as to find a solution without spending much money because it will take over a year to get sanction any solution requiring more than 1000Euro from management, Any Input regarding a mistake I am making in assuming why there is a fluctuation in system, I will really appreciate any help.
If you can point me to a thread of forum dealt with same issue , I will be thankful for it too.
Thank you for your time
