Transformer Safety Switches

[shoon]

I work at a plant that has (2x) 4160v / 480v 1000kva oil filled transformers. The transformers are wired into schweitzer SEL-787 protection relays.
I noticed that there are winding heaters as well as pressure, liquid level, and liquid temp safety switches that were never tied into the protection relays. Are these considered to be optional safety features? Or did the engineer goof and forget to include them in the drawings?

I am thinking the low level and pressure switches are pretty important.. I mean I'm sure the protection relay would shut things down before things got too burnt up, but wouldn't it be too late at that point?

 

[mbrooke]

At 1000kva nearly all utility and many industrial transformers are protected via fuses and no differential protection. In fact I am slightly surprised this guy has this setup, but hey, nothing wrong and might be well worth it.


You do not have to include those protection features, but considering that someone went out of their way to include differential, wiring them in would be an added plus in protection. FWIW most large transformers (ie, over 15 MVA) that are protected via differential often have buckholotz, over temperature, ect wired into the relaying.

If you have the specs for those sensors, chances are its not to late to wire them in. SEL relays are very versatile and can be set to do just about anything you want to.

 

[mbrooke]

And oh- this unit is outdoors, right?

 

[shoon]

At 1000kva nearly all utility and many industrial transformers are protected via fuses and no differential protection. In fact I am slightly surprised this guy has this setup, but hey, nothing wrong and might be well worth it.


You do not have to include those protection features, but considering that someone went out of their way to include differential, wiring them in would be an added plus in protection. FWIW most large transformers (ie, over 15 MVA) that are protected via differential often have buckholotz, over temperature, ect wired into the relaying.

If you have the specs for those sensors, chances are its not to late to wire them in. SEL relays are very versatile and can be set to do just about anything you want to.

Thanks!

Yes, have all the specs. The drawing was tucked in the panel door, it's a pretty nice looking setup. I doubt they will spend a cent on anything extra so it will likely remain unused.
Any harm not using the winding heater?

And also yes, this is an outdoor Transformer with curb / containment around it.

We also have a 25kv to 4160 transformer rated at 12mva.. I'll have to double check to see if they tied the switches in on that guy too.

 

[mbrooke]

Thanks!

Yes, have all the specs. The drawing was tucked in the panel door, it's a pretty nice looking setup. I doubt they will spend a cent on anything extra so it will likely remain unused.
Any harm not using the winding heater?

And also yes, this is an outdoor Transformer with curb / containment around it.

We also have a 25kv to 4160 transformer rated at 12mva.. I'll have to double check to see if they tied the switches in on that guy too.

I doubt you would need the winding heaters if the transformer remains under load through out the year. Even then millions of padmounts across the country do well without winding heaters under all use and weather conditions.