Commutation circuit for an HVDC circuit breaker

Claim 2

An interrupter for interrupting a high voltage direct-current circuit which comprises a DC source having a pair of terminals, first and second electrical conductors, respectively, connected to said terminals, and a load connected across said conductors, comprising: a main circuit breaker connected in said first electrical conductor in series with said load and between a first one of said terminals and said load; and a normally-open commutating circuit connected across said main circuit breaker comprising: means for suppressing voltage surges connected across said main circuit breaker; a snubber capacitor connected across said main circuit breaker; a series combination including a commutation reactor and means for absorbing energy connected across said snubber capacitor; a series combination including a commutation capacitor and an initiation switch connected across said means for absorbing energy; and means for charging said commutation capacitor connected and maintaining said commutation capacitor precharged during normal closed contact operation of said main breaker.

Claim 3

The apparatus of claim 1 wherein said means for charging said commutation capacitor comprises a charging resistor connected to said commutation capacitor and to the second of said electrical conductors.

Claim 4

The apparatus of claim 1 wherein said means for suppressing voltage surges comprises a first nonlinear resistor, and said means for absorbing energy comprises a second nonlinear resistor.

Claim 5

The apparatus of claim 3 wherein said means for charging said commutation capacitor comprises a direct current high voltage power supply.

Claim 6

The apparatus of claim 4 further comprising an initiation switch which is open during normal closed operation of the main circuit breaker.

Claim 7

The apparatus of claim 5 wherein said DC source comprises a 400 KV source, and said snubber capacitor and said commutation capacitor each have a 640 KV rating.

Claim 8

A commutation circuit for a high voltage direct current circuit, wherein said high voltage direct current circuit comprises a DC source having a pair of terminals, first and second electrical conductors, respectively, connected to said terminals and a load connected across said conductors, and a main circuit breaker connected in said first conductor in series with said load and between a first one of said terminals and said load; said commutation circuit comprising: a first commutation reactor connected in series with said main circuit breaker; a snubber capacitor connected across said main circuit breaker; means for suppressing voltage surges connected across said main circuit breaker; means for absorbing energy of the circuit at main breaker opening connected across the series combination of said main circuit breaker and said commutation reactor; a series combination of an initiation switch and a commutation capacitor connected across said series combination of said main circuit breaker and said commutation reactor; and means to precharge said commutation capacitor from the circuit voltage.

Claim 9

A commutation circuit for a high voltage direct current circuit, wherein said high voltage direct current circuit comprises a DC source having a pair of terminals, first and second electrical conductors, respectively, connected to said terminals and a load connected across said conductors, and a main circuit breaker connected in said first conductor in series with said load and between a first one of said terminals and said load; said commutation circuit comprising: a first commutation reactor connected in series with said main circuit breaker; a snubber capacitor connected across said main circuit breaker; means for suppressing voltage surges connected across said main circuit breaker; means for absorbing energy of the circuit at main breaker opening connected across the series combination of said main circuit breaker and said commutation reactor; a series combination of an initiation switch and a commutation capacitor connected across said series combination of said main circuit breaker and said commutation reactor; and means to precharge said commutation capacitor from the circuit voltage.

Claim 10

The apparatus of claim 7 wherein said main circuit breaker comprises a vacuum interrupter.

Claim 11

The apparatus of claim 8 wherein said means for suppressing voltage surges comprises a first nonlinear resistor, and said means for absorbing energy comprises a second nonlinear resistor.

Claim 12

The apparatus of claim 9 wherein said first and said second nonlinear resistors each comprises a lightning arrestor comprising series parallel connections of zinc-oxide resistor elements.

Claim 13

The apparatus of claim 10 wherein said DC source comprises a 400 KV source, said snubber capacitor comprises a capacitor having a capacitance of from 100 to 1000 picofarods and having a 640 KV voltage rating, and said commutation capacitor comprises a capacitor having a capacitance of from 1.0 to 15.0 microfarads and having a 640 KV rating.

Claim 14

An interrupter for interrupting a high voltage direct current circuit which comprises a DC source having a pair of terminals, first and second electrical conductors, respectively, connected to said terminals, and a load connected across said conductors, comprising: a series combination of a main circuit breaker and a commutation reactor connected in one of said electrical conductors; a snubber capacitor connected across said main circuit breaker; means for suppressing voltage surges connected across said main circuit breaker; means for absorbing energy of the circuit at main breaker opening connected across the series combination of said main circuit breaker and said commutation reactor; a series combination of an initiation switch and a commutation capacitor connected across said series combination of said means for absorbing energy; and means for charging said commutation capacitor.

Claim 15

An interrupter for interrupting a high voltage direct current circuit which comprises a DC source having a pair of terminals, first and second electrical conductors, respectively, connected to said terminals, and a load connected across said conductors, comprising: a series combination of a main circuit breaker and a commutation reactor connected in one of said electrical conductors; a snubber capacitor connected across said main circuit breaker; means for suppressing voltage surges connected across said main circuit breaker; means for absorbing energy of the circuit at main breaker opening connected across the series combination of said main circuit breaker and said commutation reactor; a series combination of an initiation switch and a commutation capacitor connected across said series combination of said means for absorbing energy; and means for charging said commutation capacitor.

Claim 16

The apparatus of claim 12 wherein said main circuit breaker comprises a vacuum interrupter.

Claim 17

The apparatus of claim 13 wherein said means for suppressing voltage surges comprises a first nonlinear resistor, and said means for absorbing energy comprises a second nonlinear resistor.

Claim 18

The apparatus of claim 14 wherein said first and said second nonlinear resistors each comprises a lightning arrestor comprising series-parallel connections of zinc-oxide resistor elements.

Claim 19

The apparatus of claim 15 wherein said DC source comprises a 400 KV source, said snubber capacitor comprises a capacitor having a capacitance of from 100 to 1000 picofarads and having a 640 KV voltage rating, and said commutation capacitor comprises a capacitor having a capacitance of from 1.0 to 15.0 microfarads and having a 640 KV rating.

Claim 20

The apparatus of claim 16 wherein said means for charging said commutation capacitor comprises a direct current high voltage power supply.

Claim 21

The apparatus of claim 17 wherein said DC source comprises a 400 KV source, and said snubber capacitor and said commutation capacitor each have a 640 KV rating.

Claim 24

The method of claim 19 wherein said step of precharging said commutation capacitor comprises charging said commutation capacitor from a DC source separate from said high voltage direct current circuit; and said step of superimposing a commutation current on the current of said breaker comprises closing a normally open switch connecting said commutation capacitor to said main circuit breaker.