Apparatus and method for servicing a distribution bus
First Claim
1. Apparatus for providing protection during servicing of a distribution bus powered from a main bus, the apparatus comprising:
- a circuit breaker having main contacts and adapted to be connected to the distribution bus; and
an earthing switch connected to the circuit breaker and adapted to be connected to the main bus and having a first condition in which the circuit breaker is connected to the main bus and a second condition in which the circuit breaker is connected to ground;
the circuit breaker including a protection circuit operative with the earthing switch in the second condition to open the main contacts only if current flows through the main contacts within a selected time period after the main contacts close.
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Accused Products
Abstract
Protection is provided for servicing a distribution bus by grounding the line side of a circuit breaker through which the distribution bus is fed and then closing the circuit breaker. The trip unit of the circuit breaker includes logic, in addition to the normal protection logic, which opens the circuit breaker main contacts without delay if current is detected upon closing of the grounded circuit breaker. However, if the grounded circuit breaker has been closed for a selected period of time and then current is detected, the distribution bus is kept at zero potential by not operating the breaker. A breaker auxiliary switch with a mechanical delay provides the indication of the selected time interval after closing the circuit breaker.
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Citations
9 Claims
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1. Apparatus for providing protection during servicing of a distribution bus powered from a main bus, the apparatus comprising:
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a circuit breaker having main contacts and adapted to be connected to the distribution bus; and
an earthing switch connected to the circuit breaker and adapted to be connected to the main bus and having a first condition in which the circuit breaker is connected to the main bus and a second condition in which the circuit breaker is connected to ground;
the circuit breaker including a protection circuit operative with the earthing switch in the second condition to open the main contacts only if current flows through the main contacts within a selected time period after the main contacts close. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method of providing protection for servicing a distribution bus connected to a main bus through main contacts of a circuit breaker, comprising:
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connecting the circuit breaker to ground rather than the main bus with the main contacts open;
closing the main contacts so that the distribution bus is connected to ground through the main contacts of the circuit breaker; and
opening the main contacts of the circuit breaker without delay when current flows through the main contacts within a selected time period after the closing of the main contacts. - View Dependent Claims (8, 9)
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Specification