Self-adjusting voltage filtering technique compensating for dynamic errors of capacitive voltage transformers
AssigneeGeneral Electric Company
InventorsBogdan Z. Kasztenny, William James Premerlani, Iulian Raducanu
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Abstract
A method of digitally correcting the raw output voltage from a Capacitive Voltage Transformer (CVT) with the intent to remove transient components impacting on transient accuracy of protection function. A typical CVT is represented using three parameters in the linear CVT model. A digital filter designed based on the three parameters and incorporating a dedicated mechanism to ensure numerical stability of the former. A method of self-adjusting the said filter based on system events and performed after the method has been deployed in the field and supplied from a specific CVT.
Claims22
A method of compensating a Capacitive Voltage Transformer (CVT) for transient errors, the method comprising:
- representing raw output voltage of a CVT by a series of digitally encoded samples;
- creating a digital filter, wherein a design for the digital filter is based upon an equivalent circuit diagram of the CVT;
- filtering the raw output voltage, wherein the raw output voltage is filtered using the digital filter;
- determining model parameters of the equivalent circuit diagram of the CVT, each model parameter being determined based on a relationship between at least two of a resistance, an inductance, and a capacitance of the equivalent circuit diagram of the CVT;
- and
- determining digital filter coefficients, the digital filter coefficients are determined in response to monitored system disturbances, each digital filter coefficient being determined based on a relationship between at least one of the model parameters and a fundamental frequency of the CVT.
An article of manufacture that includes a computer readable medium useable by a processor, the medium having stored thereon a sequence of instructions which, when executed by the processor, causes the processor to compensate a Capacitive Voltage Transformer (CVT) for transient errors, wherein the CVT transient error compensation is accomplished by:
- representing raw output voltage of a CVT by a series of digitally encoded samples;
- designing a digital filter, wherein a design for the digital filter is based upon an equivalent circuit diagram of the CVT;
- filtering the raw output voltage, wherein the raw output voltage is filtered using the digital filter;
- determining model parameters of the equivalent circuit diagram of the CVT, each model parameter being determined based on a relationship between at least two of a resistance, an inductance, and a capacitance of the equivalent circuit diagram of the CVT;
- and
- determining digital filter coefficients, the digital filter coefficients are determined in response to monitored system disturbances, each digital filter coefficient being determined based on a relationship between at least one of the model parameters and a fundamental frequency of the CVT.
A computer program product that includes a computer readable medium useable by a processor, the medium having stored thereon a sequence of instructions which, when executed by the processor, causes the processor to compensate a Capacitive Voltage Transformer (CVT) for transient errors, wherein the CVT transient error compensation is accomplished by:
- representing raw output voltage of a CVT by a series of digitally encoded samples;
- designing a digital filter, wherein a design for the digital filter is based upon an equivalent circuit diagram of the CVT;
- filtering the raw output voltage, wherein the raw output voltage is filtered using the digital filter;
- determining model parameters of the equivalent circuit diagram of the CVT, each model parameter being determined based on a relationship between at least two of a resistance, an inductance, and a capacitance of the equivalent circuit diagram of the CVT;
- and
- determining digital filter coefficients, the digital filter coefficients are determined in response to monitored system disturbances, each digital filter coefficient being determined based on a relationship between at least one of the model parameters and a fundamental frequency of the CVT.
Dependencies are inferred from the claim text.