# US 8,739,396 B2 · Technique for limiting transmission of fault current

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- Number: US 8,739,396 B2
- Document ID: US8739396B2
- Status: Granted
- Kind: B2
- Application number: 13/161,068
- Filed: 2011-06-15
- Published: 2011-12-22
- Granted: 2014-06-03
- Earliest claimed: 2010-06-17
- Assignees: Varian Semiconductor Equipment Associates, Inc.
- Applicants: Paul J. Murphy
- Inventors: Paul J. Murphy
- Web page: https://patentgrep.com/patent/US8739396B2

## CPC

- H02H 9/02: responsive to excess current {(current limitation for voltage regulators G05F1/573; disconnection after limiting H02H3/025)}
- H02H 9/023: {Current limitation using superconducting elements}
- H10N 60/30: Devices switchable between superconducting and normal states
- Y02E 40/60: Superconducting electric elements or equipment; Power systems integrating superconducting elements or equipment
- Y10T 29/49002: Electrical device making
- Y10T 29/49014: Superconductor
- Y10T 29/49117: Conductor or circuit manufacturing
- H02H: EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS (indicating or signalling undesired working conditions G01R, e.g. G01R31/00, G08B; locating faults along lines G01R31/08; emergency protective devices H01H)
- H10N: ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

Several embodiments of a novel technique for limiting transmission of fault current are disclosed. Current power distribution systems typically have an impedance, or reactor, on the output of the network equipment to limit current in the case of a fault condition. A low resistance switch, which changes its resistance in the presence of high current, is connected in parallel with this reactor. Thus, in normal operation, the current from the power generator bypasses the reactor, thereby minimizing power loss. However, in the presence of a fault, the resistance of the switch increases, forcing the current to pass through the reactor, thereby limiting the fault current.

## Claims

### Claim 1

A method of providing a power distribution network, the network comprising a network equipment and a current limiting reactor, the method comprising:
coupling a current limiting switch to the current limiting reactor in a parallel circuit while the reactor is operational, wherein the power distribution network is without the current limiting switch prior to the coupling and wherein the coupling of the current limiting switch to the current limiting reactor is performed without removing the current limiting reactor from the network, wherein the current limiting switch comprises a fault current limiter.

### Claim 2 (depends on 1)

The method according to claim 1, wherein the fault current limiter comprises one of a superconducting fault current limiter and a semiconductor based fault current limiter.

### Claim 3 (depends on 1)

The method of claim 1, wherein the fault current limiter is a solid state fault current limiter, and wherein the solid state fault current limiter comprises one or more components selected from the group consisting of gate turn-off thyristors, integrated gate commutated thyristors and insulated gate bipolar transistors.

### Claim 4 (depends on 1)

The method of claim 1, wherein the power distribution network delivers power having a frequency and a period, and the current limiting switch detecting a fault within ¼ period of the output power.

### Claim 5 (depends on 1)

The method of claim 1, wherein said method reduces power loss during normal operation.

### Claim 6 (depends on 1)

The method of claim 1, wherein said method reduces voltage loss during normal operation.

### Claim 7 (depends on 1)

The method of claim 1, wherein said method reduces phase angle change during normal operation.

### Claim 8

A method of providing a power distribution network, the network comprising a network equipment and a current limiting reactor, the method comprising:
coupling a current limiting switch to the current limiting reactor in a parallel circuit while the reactor is operational, wherein the power distribution network is without the current limiting switch prior to the coupling and wherein the coupling of the current limiting switch to the current limiting reactor is performed without removing the current limiting reactor from the network, wherein the current limiting switch comprises a circuit breaker, wherein the circuit breaker contains a superconducting circuit.

### Claim 9 (depends on 8)

The method according to claim 8, wherein the circuit breaker contains a semiconductor based circuit.

### Claim 10

A method of providing a power distribution network, the network comprising a network equipment and a current limiting reactor, the method comprising:
coupling a current limiting switch to the current limiting reactor in a parallel circuit while the reactor is operational, wherein the power distribution network is without the current limiting switch prior to the coupling and wherein the coupling of the current limiting switch to the current limiting reactor is performed without removing the current limiting reactor from the network, wherein the fault current limiter is a solid state fault current limiter, and wherein the solid state fault current limiter comprises one or more components selected from the group consisting of gate turn-off thyristors, integrated gate commutated thyristors and insulated gate bipolar transistors.