US 2013/0154660 A1 · SYSTEM AND METHOD FOR GROUND FAULT DETECTION AND FAULT TYPE EVALUATION

Abstract

The embodiments disclose a circuit for detecting and determining a type of ground fault in a security system. An operational amplifier (OA) having positive and negative inputs and an output may receive AC input signals having different frequencies, f1 and f2 at a positive input and provide an AC output signal at the output. An OA feedback loop may comprise a ground fault equivalent impedance connected at the OA negative input and a feedback resistor connected between the OA output and the OA negative input. A rectifier may convert the AC output signal to a DC signal and a filter to obtain a steady DC voltage from the rectified DC signal. A steady DC voltage for two different AC input signals may be obtained and converted to a relative voltage with respect to a constant input voltage amplitude. The relative voltages may be compared to detect and determine a type of ground fault condition.

Claims19

Dependent claims

A method of determining a type of ground fault condition in a circuit comprising:

applying a first and a second AC input signal having a first and a second frequency (f1 and f2) and a constant voltage level to a positive input of an operational amplifier (OA) to obtain a first and a second AC output signal;
applying a first and a second feedback signal to a negative input of the OA, the first and second feedback signals derived from the first and second AC output signals coupled to a ground path impedance;
rectifying the first and the second AC output signals to obtain first and second DC signals;
filtering the rectified first and second DC signals to obtain first and second steady DC voltages;
determining a first and a second relative voltage by subtracting the constant voltage level from the first and second steady DC voltages;
determining a ratio of the second relative voltage to the first relative voltage;
and
characterizing a type of ground fault according to the ratio.

5 more elements

Dependencies are inferred from the claim text.

System and method for ground fault detection and fault type evaluation

Life of this patent

System and method for ground fault detection and fault type evaluation

Life of this patent

Abstract

Claims19