4160V transformers and fuses

[steve66]

I am reviewing some 4160V distribution drawings. It shows 4160V fuses like "450E SS" or "200E SS" or "80E TL". I assume the "450E" means 450 amps, and the "SS" is the type of fuse?? But SS seems to be an automotive fuse, and TL seems to be a 120V plug fuse? Any ideas?

Also, the transformers all have the config. shown - delta or wye for both the primary and secondary. Some 4160V to 480V transformers show both a Wye and a Delta on the primary, and a Wye on the secondary??? Does this mean the transformer can be wired either way, or do some transformers actually have 3 sets of windings?

Steve

 

[jim dungar]

Re: 4160V transformers and fuses

Medium voltage fuse numbering is not like that of low voltage fuse, do not try to find any similarity.

For example you have a choice of current limiting or expulsion (also called boric acid)designs. You also have R-rated fuses for motors and E-rated fuses for feeders and power transformers. Finally you have different mounting methods (i.e. clip or bolt) and barrel sizes (i.e. D).

In your case the 450 says it is a base amperage of 450A. The E says it must melt in 600sec at 220-264%. So your fuse will hold 990-1188A for 10mins.

For more information try www.bussmann.com or www.ferrazshawmut.com or www.sandc.com.

 

[bob]

Re: 4160V transformers and fuses

Steve
It is commom to see high voltage transformers fused at about 200% of full load amps. The fuse should be based on the full load amps but also on the damage curve of the transformers. What size is the transformer?
Jim
correct me if this is incorrect.

 

[rcwilson]

Re: 4160V transformers and fuses

Wye-delta-wye transformers are common. The delta winding (sometimes called a tertiary winding) may not have any external bushings or terminals. Ito provides a path for zero sequence currents to flow to prevent a ground fault on the LV side from being seen as a ground fault on the HV system by the HV protection. It also has some benefits in limiting ferroresonance and other problems in the transformer.

We use the wye-delta-wye transformer to match phase angles of an existing system and a delta-wye transformer?s 30 degree phase shift would throw the phasing off. [For example, adding a 4.16kV ? 480 V transformer in a plant with 13.8kV distribution and exisitng delta-wye 4.16 kV and 480 V transformers. To keep the 480V in phase with the existing 480 V, we need a wye-wye or wye-delta-wye.]

Or your transformers may be capable of wye or delta connection on the HV side with windings rated for 2400V. Connect them wye for a 4.16 kV feed, connect delta for 2400V.

 

[steve66]

Re: 4160V transformers and fuses

Thanks for the replies.

Bob: I wasn't questioning the size of the fuses, just if I understood the notation. There are several transformers, and yes, a lot of the fuses seem to be sized at 150-250% of the transformer rating.

Steve

 

[templdl]

Re: 4160V transformers and fuses

Steve66,
Primary fusing of transfomers with medium voltage primaries are to protect the distribution system if the transformer fails. You want the system to coodinate should the transformer have an internal failure.
Now, what about transformer overload protection? How else would the transformer be overloaded but be the load placed on the secondary. The transformer would be protected by the secondary OCPD. In any event all fuse curves for all parts of the distribution system including that which is located on the sec. side of the transformer should be compared for coordination.