Method of protecting power transmission lines and apparatus for realizing same

Claim 1

A method of protection of a power transmission line based on a comparison between an actual quantity of current at the beginning of the protected section of the power transmission line and a quantity of current of the protected section calculated when there are no faults in the protected section, comprising the steps of: (a) measuring current and voltage at the end of said protected section of said power transmission line; (b) separating respective symmetrical components from said current and voltage at the end of said protected section of said power transmission line; (c) multiplying said separated symmetrical component of said voltage by a first coefficient of an equivalent four-terminal network substituting for said protected section of said power transmission line in a no-damage condition; (d) multiplying said separated symmetrical component of said current by a second coefficient of said four-terminal network substituting for said protected section of said power transmission line in a no-damage condition to obtain a symmetrical voltage component proportional to said current at the end of said protected section; (e) adding said multiplied symmetrical component of said voltage to said symmetrical voltage component proportional to said current at the end of said protected section to obtain an equivalent voltage proportional to said current at said beginning of said protected section of said power transmission line calculated when there are no faults in said protected section; (f) separating a fundamental harmonic from said equivalent voltage; (g) measuring current at said beginning of said protected section and voltage proportional to said current at said beginning; (h) separating a respective symmetrical component from said current at said beginning; (i) separating a fundamental harmonic from said separated symmetrical component of said current at the beginning, said fundamental harmonic of the current being in proportion to the fundamental voltage harmonic proportional to the current at the beginning of the protected section; (j) adding said fundamental harmonic obtained from said equivalent voltage to said fundamental harmonic of said voltage proportional to said current at the beginning to obtain a difference of said fundamental harmonics; (k) amplifying said difference of fundamental harmonics, and (l) comparing said amplified difference between fundamental harmonics to said fundamental harmonic obtained from said separated symmetrical component of said current at the beginning of said protected section.

Claim 2

A method of protection of a power transmission line based on a comparison between an actual quantity of current at the beginning of the protected section of the power transmission line and a quantity of current of the protected section calculated when there are no faults in the protected section, comprising the steps of: (a) measuring current and voltage at the end of said protected section of said power transmission line; (b) separating respective symmetrical components from said current and voltage at the end of said protected section of said power transmission line; (c) multiplying said separated symmetrical component of said voltage by a first coefficient of an equivalent four-terminal network substituting for said protected section of said power transmission line in a no-damage condition; (d) multiplying said separated symmetrical component of said current by a second coefficient of said four-terminal network substituting for said protected section of said power transmission line in a no-damage condition to obtain a symmetrical voltage component proportional to said current at the end of said protected section; (e) adding said multiplied symmetrical component of said voltage to said symmetrical voltage component proportional to said current at the end of said protected section to obtain an equivalent voltage proportional to said current at said beginning of said protected section of said power transmission line calculated when there are no faults in said protected section; (f) separating a fundamental harmonic from said equivalent voltage; (g) measuring current at said beginning of said protected section and voltage proportional to said current at said beginning; (h) separating a respective symmetrical component from said current at said beginning; (i) separating a fundamental harmonic from said separated symmetrical component of said current at the beginning, said fundamental harmonic of the current being in proportion to the fundamental voltage harmonic proportional to the current at the beginning of the protected section; (j) adding said fundamental harmonic obtained from said equivalent voltage to said fundamental harmonic of said voltage proportional to said current at the beginning to obtain a difference of said fundamental harmonics; (k) amplifying said difference of fundamental harmonics, and (l) comparing said amplified difference between fundamental harmonics to said fundamental harmonic obtained from said separated symmetrical component of said current at the beginning of said protected section.

Claim 3

A method of protection of a power transmission line based on a comparison between an actual quantity of voltage at the beginning of the protected section of the power-transmission line and a quantity of voltage calculated when there are no faults in the protected section, comprising the steps of: (a) measuring current and voltage at the end of said protected section of said power transmission line; (b) separating respective symmetrical components of said current and voltage at said end of said protected section; (c) multiplying said separated symmetrical component of said voltage by a first coefficient of a four-terminal network substituting for said protected section at a no-damage condition; (d) multiplying said separated symmetrical component of said current by a second coefficient of the four-terminal network substituting for said protected section at a no-damage condition to obtain a symmetrical component of voltage proportional to said current at the end of said protected section; (e) adding said multiplied symmetrical component of said voltage to said multiplied symmetrical component of the voltage proportional to said current at the end of said protected section to obtain an equivalent voltage proportional to the voltage at said beginning of the line calculated when there are no faults in said protected section; (f) separating a fundamental harmonic from said equivalent voltage; (g) measuring voltage at the beginning of said protected section; (h) separating a respective symmetrical component from said voltage at said beginning of said protected section; (i) separating a fundamental harmonic from said separated symmetrical component of said voltage at said beginning of said protected section; (j) adding said fundamental harmonic of said voltage at said beginning of said protected section to said fundamental harmonic of said equivalent voltage to obtain the difference of said fundamental harmonics; (k) amplifying said difference of said fundamental harmonics; and (l) comparing said amplified difference of said fundamental harmonics to said fundamental harmonic obtained from said separated symmetrical component of said voltage at said beginning of said protected section.

Claim 4

A method of protection of a power transmission line based on a comparison between an actual quantity of voltage at the beginning of the protected section of the power-transmission line and a quantity of voltage calculated when there are no faults in the protected section, comprising the steps of: (a) measuring current and voltage at the end of said protected section of said power transmission line; (b) separating respective symmetrical components of said current and voltage at said end of said protected section; (c) multiplying said separated symmetrical component of said voltage by a first coefficient of a four-terminal network substituting for said protected section at a no-damage condition; (d) multiplying said separated symmetrical component of said current by a second coefficient of the four-terminal network substituting for said protected section at a no-damage condition to obtain a symmetrical component of voltage proportional to said current at the end of said protected section; (e) adding said multiplied symmetrical component of said voltage to said multiplied symmetrical component of the voltage proportional to said current at the end of said protected section to obtain an equivalent voltage proportional to the voltage at said beginning of the line calculated when there are no faults in said protected section; (f) separating a fundamental harmonic from said equivalent voltage; (g) measuring voltage at the beginning of said protected section; (h) separating a respective symmetrical component from said voltage at said beginning of said protected section; (i) separating a fundamental harmonic from said separated symmetrical component of said voltage at said beginning of said protected section; (j) adding said fundamental harmonic of said voltage at said beginning of said protected section to said fundamental harmonic of said equivalent voltage to obtain the difference of said fundamental harmonics; (k) amplifying said difference of said fundamental harmonics; and (l) comparing said amplified difference of said fundamental harmonics to said fundamental harmonic obtained from said separated symmetrical component of said voltage at said beginning of said protected section.

Claim 5

A method of protection of a power transmission line based on a comparison between actual quantities of voltage and current at the beginning of the protected section of the power transmission line and electrical quantities calculated when there are no faults in said protected section, comprising the steps of: (a) measuring current and voltage at the end of said protected section of said power transmission line; (b) separating respective symmetrical components from said current and voltage at said end of said protected section; (c) multiplying each of said separated symmetrical components of said current and voltage by two coefficients of an equivalent four-terminal network substituting for said protected section at a no-damage condition to obtain as a result two symmetrical components of said voltage at the end of said protected section and two symmetrical components of the voltage proportional to the current at the end of said protected section; (d) adding two multiplied separated symmetrical components of said voltage at the end of said protected section to said two symmetrical components of the voltage proportional to the current at the end of said protected section to obtain an equivalent voltage proportional to the sum of said voltage at said beginning and said voltage proportional to said current at said beginning calculated when there are no faults in said protected section; (e) separating a fundamental harmonic from said equivalent voltage; (f) measuring voltage and current at said beginning of said protected section; (g) separating respective symmetrical components from said current and voltage at said beginning of said protected section, the symmetrical current component being in conformity with the symmetrical component of voltage proportional to said current at the beginning of said protected section; (h) adding said respective symmetrical component of said voltage at said beginning to said symmetrical component of voltage proportional to said current at said beginning to obtain as a result a compensated voltage; (i) separating a fundamental harmonic from said compensated voltage; (j) adding said fundamental harmonic from said equivalent voltage to said fundamental harmonic from said compensated voltage to obtain as a result a difference of said fundamental harmonics; (k) amplifying said difference of said fundamental harmonics; and (l) comparing said amplifiedd difference of said fundamental harmonics to said fundamental harmonic of said compensated voltage.

Claim 6

A method of protection of a power transmission line based on a comparison between actual quantities of voltage and current at the beginning of the protected section of the power transmission line and electrical quantities calculated when there are no faults in said protected section, comprising the steps of: (a) measuring current and voltage at the end of said protected section of said power transmission line; (b) separating respective symmetrical components from said current and voltage at said end of said protected section; (c) multiplying each of said separated symmetrical components of said current and voltage by two coefficients of an equivalent four-terminal network substituting for said protected section at a no-damage condition to obtain as a result two symmetrical components of said voltage at the end of said protected section and two symmetrical components of the voltage proportional to the current at the end of said protected section; (d) adding two multiplied separated symmetrical components of said voltage at the end of said protected section to said two symmetrical components of the voltage proportional to the current at the end of said protected section to obtain an equivalent voltage proportional to the sum of said voltage at said beginning and said voltage proportional to said current at said beginning calculated when there are no faults in said protected section; (e) separating a fundamental harmonic from said equivalent voltage; (f) measuring voltage and current at said beginning of said protected section; (g) separating respective symmetrical components from said current and voltage at said beginning of said protected section, the symmetrical current component being in conformity with the symmetrical component of voltage proportional to said current at the beginning of said protected section; (h) adding said respective symmetrical component of said voltage at said beginning to said symmetrical component of voltage proportional to said current at said beginning to obtain as a result a compensated voltage; (i) separating a fundamental harmonic from said compensated voltage; (j) adding said fundamental harmonic from said equivalent voltage to said fundamental harmonic from said compensated voltage to obtain as a result a difference of said fundamental harmonics; (k) amplifying said difference of said fundamental harmonics; and (l) comparing said amplifiedd difference of said fundamental harmonics to said fundamental harmonic of said compensated voltage.

Claim 7

An apparatus for protection of a power transmission line with respect to current based on a comparison between an actual quantity of current at the beginning of the protected section of the power transmission line, transmitted along a communications channel by means of a data transmission unit and a data reception unit, and a quantity of current calculated when there are no faults in the protected section, comprising: (a) current measuring units, a first of said current measuring units being positioned at the end of said protected section of said power transmission line and a second of said current measuring units being positioned at the beginning of said protected section of said power transmission line; (b) a voltage measuring unit positioned at the end of said protected section of said transmission line; (c) three symmetrical components separation units transforming the three-phase system of said current and voltage into a single-phase system, a first and a second of said symmetrical components separation units being positioned at the end of said protected section, the first symmetrical components separation unit being connected to said voltage measuring unit and the second symmetrical components separation unit being connected to said first current measuring unit positioned at the end of said protected section, a third of said symmetrical components separation units being positioned at the beginning of said protected section and being connected to said second current measuring unit located at the beginning of said protected section; (d) symmetrical components multipliers, which multiply said separated symmetrical components by respective coefficients of an equivalent four-terminal network substituting for said protected section at a no-damage condition, said symmetrical components multipliers being positioned at the end of said protected section, and being connected respectively to said first and second symmetrical components separation units positioned at the end of said protected section, and being provided with a common output; (e) fundamental harmonic separation units, a first of said fundamental harmonic separation units being positioned at the end of said protected section and being connected to said common output of said symmetrical components multipliers, a second of said fundamental harmonic separation units being positioned at the beginning of said protected section and being connected to said third symmetrical components separation unit; (f) an adder for summation of said compared electrical quantities having a first and a second input and an output, said adder being positioned at the end of said protected section of said power transmission line, said first inputs of said adder being connected to said first fundamental harmonic separation unit located at the end of said protected section of said power transmission line; said second input of said adder being connected via said data reception unit, said communications channel and said data transmission unit to said second fundamental harominc separation unit positioned at the beginning of said protected section of said power transmission line; (g) an amplification unit connected to said output of said adder; (h) a comparator having a first and a second input and an output, said first input of said comparator being connected to said amplification unit, said second input of said comparator being connected to said second input of said adder; (i) an effector, which cuts off said protected section of said power transmission line in case it is damaged, connected to said output of said comparator.

Claim 8

An apparatus for protection of a power transmission line with respect to current based on a comparison between an actual quantity of current at the beginning of the protected section of the power transmission line, transmitted along a communications channel by means of a data transmission unit and a data reception unit, and a quantity of current calculated when there are no faults in the protected section, comprising: (a) current measuring units, a first of said current measuring units being positioned at the end of said protected section of said power transmission line and a second of said current measuring units being positioned at the beginning of said protected section of said power transmission line; (b) a voltage measuring unit positioned at the end of said protected section of said transmission line; (c) three symmetrical components separation units transforming the three-phase system of said current and voltage into a single-phase system, a first and a second of said symmetrical components separation units being positioned at the end of said protected section, the first symmetrical components separation unit being connected to said voltage measuring unit and the second symmetrical components separation unit being connected to said first current measuring unit positioned at the end of said protected section, a third of said symmetrical components separation units being positioned at the beginning of said protected section and being connected to said second current measuring unit located at the beginning of said protected section; (d) symmetrical components multipliers, which multiply said separated symmetrical components by respective coefficients of an equivalent four-terminal network substituting for said protected section at a no-damage condition, said symmetrical components multipliers being positioned at the end of said protected section, and being connected respectively to said first and second symmetrical components separation units positioned at the end of said protected section, and being provided with a common output; (e) fundamental harmonic separation units, a first of said fundamental harmonic separation units being positioned at the end of said protected section and being connected to said common output of said symmetrical components multipliers, a second of said fundamental harmonic separation units being positioned at the beginning of said protected section and being connected to said third symmetrical components separation unit; (f) an adder for summation of said compared electrical quantities having a first and a second input and an output, said adder being positioned at the end of said protected section of said power transmission line, said first inputs of said adder being connected to said first fundamental harmonic separation unit located at the end of said protected section of said power transmission line; said second input of said adder being connected via said data reception unit, said communications channel and said data transmission unit to said second fundamental harominc separation unit positioned at the beginning of said protected section of said power transmission line; (g) an amplification unit connected to said output of said adder; (h) a comparator having a first and a second input and an output, said first input of said comparator being connected to said amplification unit, said second input of said comparator being connected to said second input of said adder; (i) an effector, which cuts off said protected section of said power transmission line in case it is damaged, connected to said output of said comparator.

Claim 9

An apparatus for protection of a power transmission line with respect to voltage based on a comparison between an actual quantity of voltage at the beginning of the protected section of said power transmission line, transmitted along a communications channel by means of a data transmission unit and a data reception unit, and a quantity of voltage calculated when there are no faults in said protected section, comprising; (a) a current measuring unit positioned at the end of said protected section; (b) voltage measuring units, a first of said voltage measuring units being positioned at the end of said protected section of said power transmission line, a second of said voltage measuring units being positioned at the beginning of said protected section of said power transmission line; (c) three symmetrical components separation units which transform the three-phase system of said electrical quantities of current and voltage into a single-phase system, a first and a second of said symmetrical components separation units being positioned at the end of said protected section, the first of said symmetrical components separation units being connected to said current measuring unit and the second of said symmetrical components separation units being connected to said first voltage measuring unit positioned at the end of said protected section, a third of said symmetrical components separation unit being positioned at the beginning of said protected section and being connected to said second voltage measuring unit located at the beginning of said protected section; (d) symmetrical components multipliers which multiply said separated symmetrical components by respective coefficients of an equivalent four-terminal network substituting for said protected section at a no-damage condition, said symmetrical components multipliers being positioned at the end of said protected section, being connected respectively to said first and second symmetrical components separation units positioned at the end of said protected section, and being provided with a common output; (e) fundamental harmonic separation units, a first of said fundamental harmonic separation units being positioned at the end of said protected section and being connected to said common output of said symmetrical components multipliers, a second of said fundamental harmonic separation units being positioned at the beginning of said protected section and being connected to said third symmetrical components separation units; (f) an adder for summation of said compared electrical quantities having a first and a second input and an output, said adder being positioned at the end of said protected section, said first input of said adder being connected to said first fundamental harmonic separation unit located at the end of said protected section, said second input of said adder being connected via said data reception unit, said communications channel and said data transmission unit to said second fundamental harmonic separation unit located at the beginning of said protected section; (g) an amplification unit connected to said output of said adder; (h) a comparator having a first and a second input and an output, said first input of said comparator being connected to said amplification unit, said second input of said comparator being connected to said second input of said adder; and (i) an effector, which cuts off said protected section of said power transmission line if it is damaged, connected to said output of said comparator.

Claim 10

An apparatus for protection of a power transmission line with respect to voltage based on a comparison between an actual quantity of voltage at the beginning of the protected section of said power transmission line, transmitted along a communications channel by means of a data transmission unit and a data reception unit, and a quantity of voltage calculated when there are no faults in said protected section, comprising; (a) a current measuring unit positioned at the end of said protected section; (b) voltage measuring units, a first of said voltage measuring units being positioned at the end of said protected section of said power transmission line, a second of said voltage measuring units being positioned at the beginning of said protected section of said power transmission line; (c) three symmetrical components separation units which transform the three-phase system of said electrical quantities of current and voltage into a single-phase system, a first and a second of said symmetrical components separation units being positioned at the end of said protected section, the first of said symmetrical components separation units being connected to said current measuring unit and the second of said symmetrical components separation units being connected to said first voltage measuring unit positioned at the end of said protected section, a third of said symmetrical components separation unit being positioned at the beginning of said protected section and being connected to said second voltage measuring unit located at the beginning of said protected section; (d) symmetrical components multipliers which multiply said separated symmetrical components by respective coefficients of an equivalent four-terminal network substituting for said protected section at a no-damage condition, said symmetrical components multipliers being positioned at the end of said protected section, being connected respectively to said first and second symmetrical components separation units positioned at the end of said protected section, and being provided with a common output; (e) fundamental harmonic separation units, a first of said fundamental harmonic separation units being positioned at the end of said protected section and being connected to said common output of said symmetrical components multipliers, a second of said fundamental harmonic separation units being positioned at the beginning of said protected section and being connected to said third symmetrical components separation units; (f) an adder for summation of said compared electrical quantities having a first and a second input and an output, said adder being positioned at the end of said protected section, said first input of said adder being connected to said first fundamental harmonic separation unit located at the end of said protected section, said second input of said adder being connected via said data reception unit, said communications channel and said data transmission unit to said second fundamental harmonic separation unit located at the beginning of said protected section; (g) an amplification unit connected to said output of said adder; (h) a comparator having a first and a second input and an output, said first input of said comparator being connected to said amplification unit, said second input of said comparator being connected to said second input of said adder; and (i) an effector, which cuts off said protected section of said power transmission line if it is damaged, connected to said output of said comparator.

Claim 11

An apparatus for protection of a power transmission line with respect to current and voltage based on a comparison between actual quantities of voltage and current at the beginning of the protected section of the power transmission line, transmitted along a communications channel by means of data reception and transmission units, and quantities of voltage and current calculated when there are not faults in the protected section, which comprises: (a) current measuring units, a first of said current measuring units positioned at the end of said protected section of said power transmission line, a second of said current measuring units being positioned at the beginning of said protected section of said power transmission line; (b) voltage measuring units, a first of said voltage measuring units being positioned at the end of said protected section, a second of said voltage measuring units being positioned at the beginning of said protected section; (c) four symmetrical components separation units which transform the three-phase system of said electrical quantities of current and voltage into a single-phase system, a first and a second of said symmetrical components separation units being positioned at the end of said protected section of said power transmission line, said first symmetrical components separation unit being connected to said first voltage measuring unit, said second symmetrical components separation unit being connected to said first current measuring unit, a third and a fourth of said symmetrical components separation units being positioned at the beginning of said protected section and being connected respectively to said second current measuring unit and said second voltage measuring unit, said third and said fourth symmetrical components separation units being provided with a common output; (d) four symmetrical components multipliers which multiply said separated symmetrical components by respective coefficients of an equivalent four-terminal network substituting for said protected section at a no-damage condition, said symmetrical components multipliers being positioned at the end of said protected section, a first and a second of said symmetrical components multipliers are provided with a common output connected to said first symmetrical components separation unit located at the end of said protected section, the third and fourth of said four symmetrical components separation units are provided with a common output connected to said second symmetrical components separation unit located at the end of said protected section, said four symmetrical components multipliers being provided with a common output; (e) fundamental harmonic seperation units, a first of said fundamental harmonic separation units being positioned at the end of said protected section and being connected to said common output of said four symmetrical components multipliers, a second of said fundamental harmonic separation units being positioned at the beginning of said protected section and being connected to said common output of said third and fourth symmetrical components separation units; (f) an adder for summation of said compared electrical quantities having a first and a second input and an output, said adder being positioned at the end of said protected section, said first input of said adder being connected to said first fundamental harmonic separation unit located at the end of said protected section, said second input of said adder being connected via said data reception unit, said communications channel and said data transmission unit to said second fundamental harmonic separation unit located at the beginning of said protected section; (g) an amplification unit connected to said output of said adder; (h) a comparator having a first and a second input and an output, said first input of said comparator being connected to said amplification unit, said second input of said comparator being connected to said second input of said adder; and (i) an effector, which cuts off said protected section if it is damaged, connected to said output of said comparator.

Claim 12

An apparatus for protection of a power transmission line with respect to current and voltage based on a comparison between actual quantities of voltage and current at the beginning of the protected section of the power transmission line, transmitted along a communications channel by means of data reception and transmission units, and quantities of voltage and current calculated when there are not faults in the protected section, which comprises: (a) current measuring units, a first of said current measuring units positioned at the end of said protected section of said power transmission line, a second of said current measuring units being positioned at the beginning of said protected section of said power transmission line; (b) voltage measuring units, a first of said voltage measuring units being positioned at the end of said protected section, a second of said voltage measuring units being positioned at the beginning of said protected section; (c) four symmetrical components separation units which transform the three-phase system of said electrical quantities of current and voltage into a single-phase system, a first and a second of said symmetrical components separation units being positioned at the end of said protected section of said power transmission line, said first symmetrical components separation unit being connected to said first voltage measuring unit, said second symmetrical components separation unit being connected to said first current measuring unit, a third and a fourth of said symmetrical components separation units being positioned at the beginning of said protected section and being connected respectively to said second current measuring unit and said second voltage measuring unit, said third and said fourth symmetrical components separation units being provided with a common output; (d) four symmetrical components multipliers which multiply said separated symmetrical components by respective coefficients of an equivalent four-terminal network substituting for said protected section at a no-damage condition, said symmetrical components multipliers being positioned at the end of said protected section, a first and a second of said symmetrical components multipliers are provided with a common output connected to said first symmetrical components separation unit located at the end of said protected section, the third and fourth of said four symmetrical components separation units are provided with a common output connected to said second symmetrical components separation unit located at the end of said protected section, said four symmetrical components multipliers being provided with a common output; (e) fundamental harmonic seperation units, a first of said fundamental harmonic separation units being positioned at the end of said protected section and being connected to said common output of said four symmetrical components multipliers, a second of said fundamental harmonic separation units being positioned at the beginning of said protected section and being connected to said common output of said third and fourth symmetrical components separation units; (f) an adder for summation of said compared electrical quantities having a first and a second input and an output, said adder being positioned at the end of said protected section, said first input of said adder being connected to said first fundamental harmonic separation unit located at the end of said protected section, said second input of said adder being connected via said data reception unit, said communications channel and said data transmission unit to said second fundamental harmonic separation unit located at the beginning of said protected section; (g) an amplification unit connected to said output of said adder; (h) a comparator having a first and a second input and an output, said first input of said comparator being connected to said amplification unit, said second input of said comparator being connected to said second input of said adder; and (i) an effector, which cuts off said protected section if it is damaged, connected to said output of said comparator.