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ETU 25B keeps tripping on 3WL Air circuit breaker

Created by: michal07 at: 5/30/2011 4:25 AM (12 Replies)

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5/30/2011 4:25 AM	Rate (0)
michal07 Posts: 7 Rating: (0)	Hello, I'm looking for electrical schematic of energy transfomer (which is I think really voltage transfomer) installed on 3WL 1220-3CB34-5AM2 Air Circuit Breaker. ETU keeps tripping the breaker as soon as throu the breaker current starts to flow. Resistance of current transformers is 220ohm, which I confirm with new breaker is ok, so I assume that is not bad overload protection which is tripping the breaker. Short circuit is not the reason as well. Breaker supplies simoreg converter and from trace function, current starts to flow from 0A to around 200A (for nominal current of the DC motor 360A) after 100ms and then breaker is tripping. So it seems, like as soon as ETU is powered from current transformers is tripping the breaker and the reason can be energy transformers installed on each phase. Resistance of each energy transformer is 5ohm (same as new breaker), but voltage drop between VT's is less about 1V(when line is powered with 660V) from the breaker on the line which aren't tripping. Voltage drop is about 7V and for working units is about 8.5V. ETU 25B confirmed in other breaker is working fine. Any idea, what can be wrong? Is that ETU 25B has also unbalanced load or phase failure protection?
michal07 Posts: 7 Rating: (0)
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6/1/2011 7:20 AM	Rate (0)
PISCEAN 2010 Diamond Member Joined: 4/23/2010 Last visit: 11/14/2024 Posts: 8092 Rating: (878)	Hello, What class CTs are used in breaker? Do you have any idea? Are you getting any indication of breaker tripping? Please confirm.

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6/1/2011 8:11 AM	Rate (0)
michal07 Posts: 7 Rating: (0)	Hello, I don't have any idea what is the class of CT's. I can only tell that from each phase there are four wires coming out and from manual we can read, that two of them are CT's and two of them are energy transformer (can somebode confirm if its just different name for voltage transformer, or something else?) There is no indication on ETU during tripping, none of diodes lights up.
michal07 Posts: 7 Rating: (0)
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6/1/2011 9:12 AM	Rate (0)
PISCEAN 2010 Diamond Member Joined: 4/23/2010 Last visit: 11/14/2024 Posts: 8092 Rating: (878)	Does this breaker has undervolt or shunt release mechanisam? Can you provide detail wiring diagram?
	Last edited by: DEEPSTR2010 at: 6/1/2011 9:13 AM
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6/1/2011 9:50 AM	Rate (0)
michal07 Posts: 7 Rating: (0)	There is no shunt realese mechanism. It has undervoltage coil for tripping, but if red pin on ETU is out, it means that only thing what tripped the breaker is ETU activation. I can see also solenoid activited on ETU. To ETU is only connected to CT and energy transformer from the each phase, so if ETU has been checked on other unit, seems like only CT or ET are the reason of tripping. Diagram is simple. 3 pairs of CT's and 3 pairs of ET's connected directly to ETU. Nothing more is connected. ETU is supplied from the current flowing through CT's. Undervoltage coil is not the reason. Its energized at all times.
michal07 Posts: 7 Rating: (0)
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6/1/2011 11:11 AM	Rate (0)
PISCEAN 2010 Diamond Member Joined: 4/23/2010 Last visit: 11/14/2024 Posts: 8092 Rating: (878)	Have you checked the phase sequence of incoming as well as outgoing supply, CT & ET transformer? Can you check the operation of breaker on load by connecting some other load.

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6/1/2011 12:11 PM	Rate (0)
michal07 Posts: 7 Rating: (0)	Phase sequence is correct. There are 3 the same breakers on the one bus, which supply 6 motors in total (2 DC motors and each one has its own DC Simoreg Converter) Only one breaker is tripping, and I think its not due to load, because I've tried with one motor disconnected and then with other disconnected, same result. As I mentioned, I check the current on Drive Monitor. Its not overloaded, all 3 phases are detectable by the drive in right sequence. There is no possibility to connects other load. Anyway, how this CT's an ET' are interconnected? Can somebode give more details about ET's?
michal07 Posts: 7 Rating: (0)
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6/2/2011 11:23 AM	Rate (0)
PISCEAN 2010 Diamond Member Joined: 4/23/2010 Last visit: 11/14/2024 Posts: 8092 Rating: (878)	Hello, Have you checked the setting range Ir=Inx.... ( Selectable) Please check & confirm. Attached please see the 3WL ACB termination drg. It may help you. Attachment 3WL ACB termination drg.pdf (769 Downloads)
	Last edited by: DEEPSTR2010 at: 6/2/2011 1:07 PM
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6/3/2011 7:48 AM	Rate (0)
PISCEAN 2010 Diamond Member Joined: 4/23/2010 Last visit: 11/14/2024 Posts: 8092 Rating: (878)	Hello, Please check following link https://a248.e.akamai.net/cache.automation.siemens.com/dnl/TM/TM4Njg1AAAA_8912465_HB/Sentron_WL.html. On page 16 of Maintenance file you will find CT assly drg. Please check & confirm the proper connection of CT.

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6/3/2011 8:43 AM	Rate (0)
michal07 Posts: 7 Rating: (0)	Hello, I have complete manual with all dwgs, but the thing is that this drwgs. does not correspond to real connection. As You can see on the picture I attached: From the ETU 25B there are two X20 and X21 connectors and wires from this connectors are going directly to each phase to CT's and ET's. I can read in manual that X20 is connection for CT's and X21 for ET's. There is now way that some connections has been changed or polarization is swap. Everything was working and then suddenly tripped, without any external intervention. Question is how exactly CT's and ET's are interconnected inside and how to perform reliable check on this transformers? Seems to me, the problem is with transformers. Phase sequence is correct. There is no overload and no short circuit, no earth fault what so ever. So maybe CT's or ET's are not giving real value of the current due to its failure. But how to be sure? One way is to understand how they are interconnected and what is the princple for this transformers? Once again: If ETU is tripping, only reason is activation by CT's and ET's. Setting for ETU is OK, other ETU which works on other breaker with the same load is also tripping on this breaker. There is no overload, no short circuit, no earth fault. Resistance of CT's and ET's is exactly the same as working breaker. CT's and ET's are somehow interconnected together on the phase. Manula does not provide sufficient information. X8 terminals which are in manual described as terminals for ETU connection does not exist in my case at all. Regards Attachment IMG_20110603_071511.jpg (698 Downloads)
michal07 Posts: 7 Rating: (0)
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