US5140492A
Expired / Lapsed
US
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Distance relay using a polarizing voltage
Assignee: Schweitzer Engineering Laboratories Inc
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Filing: 1990-04-11
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Granted: 1992-08-18
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Expires: 2010-04-11
Abstract
Abstract A distance relay for protection of power transmission lines, having a plurality of mho elements, each with a predetermined mho impedance characteristic. The relay has the capability of calculating a polarized reference voltage which remains constant through fluctuations in measured transmission line voltage. The difference voltage between the measured line voltage and the product of the measured line current and the mho element characteristic impedance is then compared against the polarized reference voltage in a product-type phase comparator to determine under-impedance conditions. If an under-impedance condition is present, the mho element produces a set output and a calculated "torque" value. The set outputs, if any, are then compared against a look-up table for fault type determination. If more than one set output is present, the magnitudes of the respective torque values are compared for fault type determination.
Inventors
- 👤 Edmund O. Schweitzer, III
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 20:39
CPC Classifications
H; H02; H02H; H02H3/00; H02H3/40; H02H3/402
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
111 words
A relay apparatus for protection of power transmission lines, comprising: at least one relay element having a selected impedance characteristic; means for measuring values of voltage and current for a selected transmission line; means using the measured voltage value to produce a polarized reference voltage; means determining a difference voltage between a measured voltage value and the product of the relay element impedance and a measured current value; and means comparing the difference voltage and the polarized reference voltage to produce an output which includes a signal indication of a possible fault on the transmission line and a magnitude associated therewith, wherein the magnitude provides further information concerning the possible fault.
Claim 2
Dependent Claim
111 words
A relay apparatus for protection of power transmission lines, comprising: at least one relay element having a selected impedance characteristic; means for measuring values of voltage and current for a selected transmission line; means using the measured voltage value to produce a polarized reference voltage; means determining a difference voltage between a measured voltage value and the product of the relay element impedance and a measured current value; and means comparing the difference voltage and the polarized reference voltage to produce an output which includes a signal indication of a possible fault on the transmission line and a magnitude associated therewith, wherein the magnitude provides further information concerning the possible fault.
Claim 3
Dependent Claim
34 words
An apparatus of claim 1, including means processing the output of said comparing means to determine a particular fault type and initiating action, if appropriate, of additional protective apparatus associated with the transmission line.
Claim 4
Dependent Claim
14 words
An apparatus of claim 2, wherein the additional protective equipment is a circuit breaker.
Claim 5
Dependent Claim
68 words
An apparatus of claim 2, wherein the relay apparatus includes a plurality of relay elements, each having an impedance characteristic, associated with selected zone portions of said transmission line, wherein said one relay element is associated with a zone portion most remote from the relay apparatus and wherein the additional protective apparatus is at least one relay element associated with a less remote zone portion of the line.
Claim 6
Dependent Claim
45 words
An apparatus of claim 4, wherein the relay elements are mho elements, and wherein the relay apparatus includes a first group of mho elements associated with said most remote zone portion and a second group of mho elements associated with the less remote zone portions.
Claim 7
Dependent Claim
17 words
An apparatus of claim 1, wherein the polarized reference value is determined from a positive sequence voltage.
Claim 8
Dependent Claim
58 words
An apparatus of claim 6, wherein the means for obtaining a polarized reference voltage includes means for sampling voltage and current values for the transmission line and calculating a positive sequence voltage VA1, for phase A, according to the following equation: VA1=1/3 [VA+(a-1)VB+(a 2 -1)VC], where a has a magnitude of one and an angle of 120 degrees.
Claim 9
Dependent Claim
40 words
An apparatus of claim 7 including means for filtering the positive sequence voltage VA1 and calculating the polarized reference voltage VA1M according to the following equation: VA1M=1/16(VA1 k )-15/16(VA1M k-2 ), wherein k is incremented in one quarter cycle steps.
Claim 10
Dependent Claim
120 words
An apparatus of claim 5, wherein the selected transmission line includes three phase lines A, B and C, and wherein the first group of mho elements includes one mho element for phase line A-to-ground, one mho element for phase line B-to-ground, one mho element for phase line C-to-ground, one mho element for phase line A to phase line B, one mho element for phase line B to phase line C and one mho element for phase line C to phase line A, and wherein there is more than one zone of protection, said first group of mho elements covering the most remote zone of protection, and said second group of mho elements being associated with the remaining zones of protection.
Claim 11
Dependent Claim
19 words
An apparatus of claim 5, wherein the output of the comparing means includes an output from each mho element.
Claim 12
Dependent Claim
42 words
An apparatus of claim 10, wherein said processing means includes means for comparing the magnitude values for each mho element having a signal indication output and providing a control output to the additional protective apparatus which is indicative of the fault type.
Claim 13
Independent Claim
103 words
A method for protection of power transmission lines using relay elements having selected impedance characteristics, comprising the steps of: measuring voltage and current values on the transmission line; calculating a polarized reference voltage using the measured voltage; determining a difference voltage between a measured voltage value and the product of the relay element impedance and a measured current value; and comparing the difference voltage and the polarized reference voltage to produce an output which includes a signal indication of a possible fault on the transmission line and a magnitude value associated therewith, wherein the magnitude value provides further information concerning the possible fault.
Claim 14
Independent Claim
103 words
A method for protection of power transmission lines using relay elements having selected impedance characteristics, comprising the steps of: measuring voltage and current values on the transmission line; calculating a polarized reference voltage using the measured voltage; determining a difference voltage between a measured voltage value and the product of the relay element impedance and a measured current value; and comparing the difference voltage and the polarized reference voltage to produce an output which includes a signal indication of a possible fault on the transmission line and a magnitude value associated therewith, wherein the magnitude value provides further information concerning the possible fault.
Claim 15
Dependent Claim
37 words
A method of claim 12, further including a step of processing said output to determine a particular fault type and thereafter a step of initiating action, if appropriate, of additional protective apparatus associated with the transmission line.
Claim 16
Dependent Claim
17 words
A method of claim 13, wherein the polarized reference voltage is calculated from a positive sequence voltage.
Claim 17
Dependent Claim
34 words
A method of claim 14, wherein the positive sequence voltage VA1 is calculated according to the following equation: VA1=1/3 [VA+(a-1)VB+(a 2 --1)VC], where a has a magnitude of one and angle of 110 degrees.
Claim 18
Dependent Claim
40 words
A method of claim 15, including the step of filtering the positive sequence voltage and calculating the polarized reference voltage VA1M according to the following equation: VA1M=1/16(VA1 k )-15/16(VA1M k-2 ), wherein k is incremented in one quarter cycle steps.
Claim 19
Dependent Claim
71 words
A method of claim 13, wherein the relay elements are mho elements which are associated with selected zone portions of said transmission line, a first plurality of the mho elements being associated with the most remote zone portion and a second plurality of mho elements being associated with remaining less wherein the initiating step includes the step of initiating action of a selected one of said second plurality of mho elements.
Claim 20
Dependent Claim
62 words
A method of claim 17, wherein the processing step includes a step of recognizing signal indications from the mho elements and a step of analyzing said signal indications against a look-up table to determine any initiating action, and the further step of comparing the magnitude values from the mho elements having signal indications if more than one to determine the initiating action.
Claim 21
Dependent Claim
29 words
A method of claim 18, wherein the initiating action is dependent upon the greatest magnitude value associated with the signal indications when more than one signal indication is present.
Claim 22
Dependent Claim
27 words
An apparatus of claim 1, wherein said comparing means including means for multiplying the difference voltage and the polarized reference voltage, said output being the product thereof.
Claim 23
Dependent Claim
29 words
A method of claim 12, wherein the step of comparing includes a step of multiplying the difference voltage and the polarized reference voltage, said output being the product thereof.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1995-08-18 | 1996-02-17 | 1996-08-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1999-08-18 | 2000-02-17 | 2000-08-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2003-08-18 | 2004-02-17 | 2004-08-18 | $7700.00 | Window Closed / Lapsed |