System for protection of dry type transformers

A system for transient over voltage protection of a three-phase, delta-connected transformer, the transformer including first, second and third windings, the system comprising:

• a first surge arrester having first and second ends;
• a second surge arrester having first and second ends;
• said first end of said first surge arrester electrically connected to a first end of the first winding, and the second end of the first surge arrester electrically connected to an intermediate location of the first winding;
• said first end of said second surge arrester electrically connected to a second end of the first winding, and the second end of the second surge arrester electrically connected to the intermediate location of the first winding;
• a third surge arrester having first and second ends;
• a fourth surge arrester having first and second ends;
• said first end of said third surge arrester electrically connected to a first end of the second winding, and the second end of the third surge arrester electrically connected to an intermediate location of the second winding;
• said first end of said fourth surge arrester electrically connected to a second end of the second winding, and the second end of the fourth surge arrester electrically connected to the intermediate location of the second winding;
• a fifth surge arrester having first and second ends;
• a sixth surge arrester having first and second ends;
• said first end of said fifth surge arrester electrically connected to a first end of the third winding, and the second end of the fifth surge arrester electrically connected to an intermediate location of the third winding;
• said first end of said sixth surge arrester electrically connected to a second end of the third winding, and the second end of the sixth surge arrester electrically connected to the intermediate location of the third winding;
• a seventh surge arrester electrically connected at a first end to a connection point between the first and second windings;
• an eighth surge arrester electrically connected at a first end to a connection point between the first and third windings;
• a ninth surge arrester electrically connected at a first end to a connection point between the second and third windings;
• second ends of said seventh, eighth and ninth surge arresters each electrically connected to ground;
• a first capacitor electrically connected in parallel with said seventh surge arrester;
• a second capacitor electrically connected in parallel with said eighth surge arrester;
• and
• a third capacitor electrically connected in parallel with said ninth surge arrester.

A system for transient over voltage protection of a three-phase, delta-connected transformer, the transformer including first, second and third windings, the system comprising:

• a first surge arrester having first and second ends;
• a second surge arrester having first and second ends;
• said first end of said first surge arrester electrically connected to a first end of the first winding, and the second end of the first surge arrester electrically connected to an intermediate location of the first winding;
• said first end of said second surge arrester electrically connected to a second end of the first winding, and the second end of the second surge arrester electrically connected to the intermediate location of the first winding;
• a third surge arrester having first and second ends;
• a fourth surge arrester having first and second ends;
• said first end of said third surge arrester electrically connected to a first end of the second winding, and the second end of the third surge arrester electrically connected to an intermediate location of the second winding;
• said first end of said fourth surge arrester electrically connected to a second end of the second winding, and the second end of the fourth surge arrester electrically connected to the intermediate location of the second winding;
• a fifth surge arrester having first and second ends;
• and
• a sixth surge arrester having first and second ends;
• said first end of said fifth surge arrester electrically connected to a first end of the third winding, and the second end of the fifth surge arrester electrically connected to an intermediate location of the third winding;
• said first end of said sixth surge arrester electrically connected to a second end of the third winding, and the second end of the sixth surge arrester electrically connected to the intermediate location of the third winding;
• said first surge arrestor comprises two series-connected surge arrestors (1-1) and (1-2);
• said second surge arrestor comprises two series-connected surge arrestors (2-1) and (2-2);
• said surge arrestor (1-1) has a first end electrically connected to the first end of the first winding and said surge arrestor (1-2) has a second end electrically connected to the intermediate location of the first winding;
• said surge arrestor (1-1) has a second end electrically connected to a first end of said surge arrestor (1-2) and to a location along the first winding between the first end and the intermediate location;
• said surge arrestor (2-2) has a second end electrically connected to the second end of the first winding and said surge arrestor (2-1) has a first end electrically connected to the intermediate location of the first winding;
• and
• said surge arrestor (2-1) has a second end electrically connected to a first end of said surge arrestor (2-2) and to a location along the first winding between the second end and the intermediate location.

A system for transient over voltage protection of a three-phase, Y-connected transformer, the transformer including first, second and third windings, the system comprising:

• a first surge arrester having first and second ends;
• a second surge arrester having first and second ends;
• said first end of said first surge arrester electrically connected to a first end of the first winding, and the second end of the first surge arrester electrically connected to an intermediate location of the first winding;
• said first end of said second surge arrester electrically connected to a second end of the first winding, and the second end of the second surge arrester electrically connected to the intermediate location of the first winding;
• a third surge arrester having first and second ends;
• a fourth surge arrester having first and second ends;
• said first end of said third surge arrester electrically connected to a first end of the second winding, and the second end of the third surge arrester electrically connected to an intermediate location of the second winding;
• said first end of said fourth surge arrester electrically connected to a second end of the second winding, and the second end of the fourth surge arrester electrically connected to the intermediate location of the second winding;
• a fifth surge arrester having first and second ends;
• and
• a sixth surge arrester having first and second ends;
• said first end of said fifth surge arrester electrically connected to a first end of the third winding, and the second end of the fifth surge arrester electrically connected to an intermediate location of the third winding;
• said first end of said sixth surge arrester electrically connected to a second end of the third winding, and the second end of the sixth surge arrester electrically connected to the intermediate location of the third winding;
• said first surge arrestor comprises two series-connected surge arrestors (1-1) and (1-2);
• said second surge arrestor comprises two series-connected surge arrestors (2-1) and (2-2);
• said surge arrestor (1-1) has a first end electrically connected to the first end of the first winding and said surge arrestor (1-2) has a second end electrically connected to the intermediate location of the first winding;
• said surge arrestor (1-1) has a second end electrically connected to a first end of said surge arrestor (1-2) and to a location along the first winding between the first end and the intermediate location;
• said surge arrestor (2-2) has a second end electrically connected to the second end of the first winding and said surge arrestor (2-1) has a first end electrically connected to the intermediate location of the first winding;
• and
• said surge arrestor (2-1) has a second end electrically connected to a first end of said surge arrestor (2-2) and to a location along the first winding between the second end and the intermediate location.

A system for transient over voltage protection of a three-phase transformer, the system comprising:

• a transformer including first, second and third windings, each of the first, second and third windings having winding terminals;
• a plurality of surge arresters divided into first, second and third groups, the first group of surge arresters connected across the first winding, the second group of surge arresters connected across the second winding, and the third group of surge arresters connected across the third winding;
• each surge arrester of the first group being connected to at least one intermediate location along the first winding, the winding terminals of the first winding being connected to different surge arresters of the first group;
• each surge arrester of the second group being connected to at least one intermediate location along the second winding, the winding terminals of the second winding being connected to different surge arresters of the second group;
• and
• each surge arrester of the third group being connected to at least one intermediate location along the third winding, the winding terminals of the third winding being connected to different surge arresters of the third group;
• and
• circuit breakers coupled to each phase of the transformer;
• wherein the plurality of surge arresters protect the transformer against multiple re-ignitions of the circuit breakers;
• wherein the connection of each surge arrester to the at least one intermediate location along the respective first winding, second winding, and third winding damps internal resonances of the first winding, second winding, and third winding.