Boiler fan trip

[SA07]

Good morning

Our power plant stopped following the trip of a boiler fan due to a disturbance on the utility grid.
The fan is controlled by a simocode, soft starter & bypass contactor.
In the past several times, our power plant has islanded following disturbance/fault on the utility grid.
After the trip, we have restarted the plant and everything is working well up to now. We have not replaced any equipment.
1) Can you plz check if our simocode settings are correct?
2) Is the wiring correct?
3) Is the setting of under voltage in the simocode correct?
4) What may be the cause of the trip?
5) Can we disable the under voltage setting in the simocode?
6) Can the last alarm in the simocode alarm list be the cause of the trip? (Trip level U<)
After the boiler fan has tripped, then boiler tripped, then turbine tripped and our line breaker also has opened. So our plant was in a black out.

Plz see attached word doc with all details.
Thanks
Regards

 

[RedSnake]

Can I assume that this is the same plant as the one with the "bad" relay -KA2, and that you came to the conclusion that the problem wasn't the relay?

BR A

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[SA07]

The trip due to relay KA2 was on Power Plant 2.
The trip due to boiler fan was on Power Plant 1.

These are 2 different stoppages.

 

[RRaghunath]

The fan has a soft starter and a bypass contactor that closes once the motor reaches rated speed. Contactor is non-latched type, supplied by the same AC bus and doesn't require separate U< protection to open (it will open on its own as the coil voltage drops.
Hence, my suggestion is to disable U< protection for this fan. U< protection is required only in the following cases:
* Circuit breaker controlled motor feeders
* Latched contactor controlled motor feeders.
* Non-latched contactor controlled motor feeders in case the contactor coil is supplied from DC UPS or AC UPS.
Aside, I wonder how the voltage stayed <75% for over 3s. Is there something to worry on the protection system of the faulty feeder in the first place (75% and s are from the Simocode protection setting list)

 

[SA07]

The control voltage 230 Vac was transferred from the panel supply to a UPS.

 

[SA07]

We did this because after disturbance of utility network, the plant tripped. After the transfer of control voltage 230 Vac to UPS, the plant tripped much less often.

 

[RedSnake]

Is it the External Fault 1 that is the problem or the Trip level U <

/A

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[SA07]

Time 1516.21.01.04 Trip Level U<
Time 1355.12.14.14 External fault 1

There is a large difference in time. Trip Level U< is related to last stoppage. But we are not sure whether this caused the motor to trip or after the power plant trip, there was a power black out and this produced the Trip Level U<.

External fault 1 means emergency stop push button near motor is pressed

 

[RedSnake]

External fault 1 means emergency stop push button (that was my conclusion also) near motor is pressed.
And was it pressed or was the alarm fault coming on it's own?

The inputs where the emergency stop is connected have a delay time 16 ms + 40 ms for AC power ca 56 ms.
You could have as much as 36+40 = 76 ms.
But if the emergency signal drops without actually being used, yo need to find the external fault for it.

I have not been able to find what the levels are for it to be a "1" or "0".
Have the DW1 or -SP4 it's own part number 3UF-...... ?
Is it 3UF7300-1AU00-0 ??

The measurements that where made, one was at the fan motor?

The other Earth fault on one phase on utility network 66 kV is that measuring point in the drawing you posted?
The earth fault must be after the measuring point.

And have you found the earth fault?

BR A

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[RedSnake]

One thing we have had problems with, not on this product but similar ones with longer fast contacts.
Is that the connection between the fast contact and the inside card becomes bad.
It might be a good idea to check it and maybe use some electrical cleaner, I would recommend one without oil in it to start with.

And we also have hade a lot of problem with some UPS:s that we have to avoid the PLC systems to go to stop during a power outages.
They actually tripp more often during production then we have power outages.
Not shore what brand/model you use but check the settings on it if it can be parameterizable.

Best Regards A

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[SA07]

There are 161 days ( about 5 1/2 months) difference between The event trip level U< and external fault 1

No one pressed emergency stop on site. This is usually done during maintenance.

The earth fault occurred in the utility station at about 30 km away.

We have redundant UPS which can switch automatically in case of internal fault in the UPS without tripping the plant.

We have replaced no component or equipment and have restarted the plant which is working well. We think the problem is related to the starter of the boiler fan may be a setting in the simocode or soft starter which causes a trip after a disturbance on the utility network.

 

[RRaghunath]

"there was a power black out and this produced the Trip Level U<" - this is unlikely. However, you can verify through test by switching off the power supply (keeping the control supply on) to see whether the relay gives U< trip output.
Generally speaking, relay is programmed to discriminate between sustained under voltage and loss of power supply.

 

[RedSnake]

Is there a reason why the time stamps are 1 minute apart, measuring 2:39:22 and larm event 14:38:22 ?
The fan tripped 1 minute before the short circuit.

BR A

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[SA07]

Not all time from various equipment are synchronised on site.
Recording for 66 kV earth fault is in SEL 387 relay
Alarm boiler trip is from boiler PLC.

 

[RedSnake]

I have problem with this measuring of the boiler pan fan.
If the fan hade tripped and it was connected with contactors and ordinary breakers.
The voltage had gone to 0 "zero" no sinus wave.
Even if the fan motor was free rolling and started to work as a generator.

And if the contacts on -KMG1 and -G1 was open and the only way for the current to flow back and forth was over the "diods" in -G1 the sinus wave would not have been so "perfect".
And if the "diods" where open the fan motor has not "tripped".
If -G1 has tripped the diods should be closed and the contacts open, and if -KGM1 also is open.
You would not be able to measure a sinus wave after that, on the boiler fan.

BR A

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[RedSnake]

I would also suggest that you synchronize the clocks, if you can't do it automatically, put it on a maintenance chart and do it as often as necessary.
It helps in situations like this.
Knowing what is the main event and what is secondary faults, is always a good start with tricky faults like this.

BR A

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[davidbeach]

You need something that can distribute the time signal, generally IRIG-B. Even without a reference clock every thing on site would at least have the same time. You can’t manually set device clocks accurately enough for things to align. Manual time alignment post event can be easy or it can be a true pain. Getting relative time right is a huge step, getting absolute time correct is a nice addition if you’re dealing with a single site. With multiple sites about the only way to get relative time right is to have absolute time right.

Had one event 5 years ago where it took days to align multiple event records that claimed to span 2 years into the actual span of less than 5 seconds. Part of it was there two very similar faults in the overall event; had to figure out which relay was seeing which fault at what point in the sequence. The newer event viewing software (example shown above) certainly makes it easier than it used to be.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

 

[RedSnake]

All Siemens CPU:s can be set with a time sync via CP434 CP334 if they are connected to the ethernet.
And if you have a server with clock sync avalibul, like Network Time Protocol (NTP) the same as for the computer.
Then at least all "Siemens" data will have the same time.

If it is possible with the SEL 387 relay I do not know, maybe that one will have to be set manually.

BR A

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[davidbeach]

That SEL relay does not have Ethernet, but does have a couple of options for supplying it with an IRIG signal.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

 

[SA07]

It seems we had 4 trips due to the same boiler fan since power plant since 2007 following similar disturbance on the grid.
Can we disable the undervoltage trip as a test?
There are other boiler fans which do not have this protection in their simocode.
We have undervoltage protection as follows:

66 kV line: 45 V (Secondary) 1.5s
alternator: -20 % UaN