Patent ID: 6349022
Filing Date: 2002-02-19
Classification: H02H

Abstract:
An electrical protection system which can be connected between an electrical power supply (2) and an electrical load (4) to form an operating circuit, the operating circuit having an on state and an off state and comprising a current carrying line and a return line (6), and which when so connected protects the circuit from overcurrents, the system having a normal operating condition and a fault condition, and comprising:a. a circuit interruption element (30,32,34,36), which, when the system is so connected and is in its normal operating condition, is connected in series between the power supply and the load so that an operating current passes through the circuit interruption element and the load (4), and which has i. a closed state (30,36,34), which permits the flow of a normal operating current between the power supply (2) and the load (4) when the system is in the normal operating condition, and ii. an open state (30,36,32), which permits the flow of substantially no operating current between the power supply and the load, when the system is in the fault condition; b. a sensor element (14), which, when the system is so connected and is in its normal operating condition, is connected in series with the circuit interruption element and the load so that the operating current passes through the circuit interruption element, the sensor element and the load, and which has i. a normal state, when the operating current in the system does not exceed the normal operating current by a predetermined amount; and ii. a fault state, when the operating current in the system exceeds the normal operating current by the predetermined amount; and c. a control element (8,12), which, when the system is so connected, is responsively coupled with the sensor element and is controllably coupled with the circuit interruption element (36), and has an electrical characteristic which i. is low impedance when the sensor element is in the normal state, ii. is high impedance when the sensor element has the fault state, and iii. remains at the high impedance until the system is reset to the normal operating condition; and d. reset means (16) coupled to the control means for resetting the system from the fault condition to the normal operating condition; the circuit interruption element (36) changing from its closed state to its open state, thereby causing the system to change from its normal operating condition to its fault condition and to remain in the fault condition, when the sensor element (14), has the fault state, until the reset means resets the system to the normal operating condition.