# US 11,451,044 B2 · Automated self testing of power grid transformer protection systems > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,451,044 B2 - Document ID: US11451044B2 - Status: Granted - Kind: B2 - Application number: 17/102,039 - Filed: 2020-11-23 - Published: 2021-05-27 - Granted: 2022-09-20 - Earliest claimed: 2019-11-22 - Assignees: TechHold, LLC - Applicants: TechHold, LLC - Inventors: Frederick R. Faxvog; Greg Fuchs; Wallace Jensen; David Anderson - Web page: https://patentgrep.com/patent/US11451044B2 ## CPC - H02H 3/05: with means for increasing reliability, e.g. redundancy arrangements {(for logic circuits H03K19/003)} - G01R 31/3333: {Apparatus, systems or circuits therefor} - H02H 1/0007: {concerning the detecting means (in general G01R or other subclasses of G01; reed switches H01H71/2445)} - H02H 3/17: by means of an auxiliary voltage injected into the installation to be protected {(using summation current transformers H02H3/33)} - H02H 3/20: responsive to excess voltage - H02H 5/005: {responsive to ionising radiation; Nuclear-radiation circumvention circuits (radiation detectors G01T; nuclear-explosion detection G21J5/00)} - H02H 7/04: for transformers - H02H 3/044: {Checking correct functioning of protective arrangements, e.g. by simulating a fault (for differential current circuit breakers H02H3/335)} - H02H: EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS (indicating or signalling undesired working conditions G01R, e.g. G01R31/00, G08B; locating faults along lines G01R31/08; emergency protective devices H01H) - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) ## Abstract Systems and method for automated self-testing of a protective device for a transformer are disclosed. One system includes a protection circuit electrically connected to a transformer neutral, the transformer electrically connected to a power grid, the protection circuit may include a DC blocking component, a switch assembly, and a spark gap assembly each positioned in parallel between the transformer neutral and ground, a switch assembly. The system may further include various testing circuits configured within the protection circuit and switches which when actuated inject a signal to test various components in the protective device. ## Claims ### Claim 1 A self-testing system for use within an electrical protection circuit comprising: the electrical protection circuit electrically connected between a neutral of a transformer and a ground, the transformer electrically connected to a power grid, wherein the electrical protection circuit includes a switch assembly; wherein the switch assembly includes a plurality of switches connected in series with a shunt resistor between the neutral and the ground, the shunt resistor being electrically connected adjacent the ground; a switch assembly test circuit comprising: a switch-testing voltage source in series with a current limiting resistor; a test actuation switch electrically connected between the switch-testing voltage source, and a location between the shunt resistor and the switch assembly, wherein, when the test actuation switch is closed, a test current is applied across the shunt resistor to test whether the switch assembly is actuated in response to a detected current flowing through the shunt resistor exceeding a predetermined threshold, the detected current being representative of potential damage to one of the transformer or a DC blocking circuit. ### Claim 2 (depends on 1) The self-testing system of claim 1, wherein: the electrical protection circuit further includes the DC blocking component connected in parallel with the switch assembly between the neutral and the ground; a source electrically connected in parallel with the DC blocking component, the source including a voltage source, a current measurement device configured to determine a current flowing through the DC blocking component, and a voltage measurement device configured to determine a voltage across the DC blocking component; and an additional test actuation switch electrically connected between the source and the DC blocking component, wherein, when the additional test actuation switch is closed, a test voltage is applied across the DC blocking component, and an impedance of the DC blocking component is measured and compared to an expected design value. ### Claim 3 (depends on 1) The self-testing system of claim 1, wherein: the electrical protection circuit further includes a spark gap assembly electrically connected in parallel with the assembly between the neutral and the ground; a transformer protection switch electrically connected between the transformer neutral and the electrical protection circuit; a high voltage source electrically connected in parallel with the spark gap assembly; an additional test actuation switch electrically connected between the high voltage source and the spark gap assembly, wherein, when the additional test actuation switch is closed, a test high voltage is injected across the spark gap assembly to determine a breakdown voltage of the spark gap assembly. ### Claim 4 A self-testing system for use within an electrical protection circuit comprising: the electrical protection circuit electrically connected between a neutral of a transformer and a ground, the transformer electrically connected to a power grid, wherein the electrical protection circuit includes a DC blocking component; a test voltage source electrically connected in parallel with the DC blocking component, the test voltage source including a voltage source, a current measurement device configured to determine a current flowing through the DC blocking component, and a voltage measurement device configured to determine a voltage across the DC blocking component; and a switch electrically connected between the test voltage source and the DC blocking component; wherein the self-test system has a testing mode in which the first switch is opened and the switch is closed to introduce a test voltage across the DC blocking component, and wherein an impedance of the DC blocking component is measured and compared to an expected design value in the testing mode. ### Claim 5 (depends on 4) The self-testing system of claim 4, wherein: the electrical protection circuit further includes: a spark gap assembly electrically connected in parallel with the DC blocking component between the neutral and the ground; and a second switch electrically connected between the transformer neutral and the DC blocking component, wherein the self-testing system further includes: a high voltage source; a third switch, wherein the high voltage source and the third switch are electrically connected in series with each other and in parallel with the spark gap assembly; wherein, when the third switch is closed and the second switch is opened, a test high voltage is injected across the spark gap assembly to determine a breakdown voltage of the spark gap assembly. ### Claim 6 (depends on 5) The self-testing system of claim 5, wherein the high voltage source is configured to increase the test high voltage from a predetermined level until an electrical arc is initiated across the spark gap assembly; wherein the voltage at which the electrical arc is initiated is compared to an expected threshold voltage by the self-testing system. ### Claim 7 (depends on 6) The self-testing system of claim 6, wherein, when the third switch is closed to inject the test high voltage across the spark gap assembly, a fourth switch is opened to isolate the spark gap from the transformer neutral and the DC blocking component. ### Claim 8 (depends on 6) The self-testing system of claim 6, wherein the self-testing system sends an alarm if the voltage at which the electrical arc is initiated is higher than the expected threshold voltage. ### Claim 9 (depends on 6) The self-testing system of claim 6, wherein the spark gap assembly includes a plurality of spark gaps in parallel to each other. ### Claim 10 (depends on 6) The self-testing system of claim 6, wherein the high voltage source applies a voltage of greater than 5 kilovolts across the spark gap assembly. ### Claim 11 (depends on 4) The self-testing system of claim 4, wherein the second switch comprises an automated motorized grounding switch. ### Claim 12 (depends on 4) The self-testing system of claim 4, wherein the DC blocking component is electrically connected in parallel with a switch assembly, and the electrical protection circuit has a protective mode in which the switch assembly is in an open position and a normal operating mode in which the switch assembly is in a closed position. ### Claim 13 (depends on 12) The self-testing system of claim 12, wherein the switch assembly includes a plurality of switches connected in series with a shunt resistor between the neutral and the ground, the shunt resistor being electrically connected adjacent the ground. ### Claim 14 (depends on 13) The self-testing system of claim 13, further comprising: a switch assembly test circuit comprising: a switch-testing voltage source; a test actuation switch electrically connected between the switch-testing voltage source, and a location between the shunt resistor and the switch assembly, wherein, when the test actuation switch is closed, a test current is applied across the shunt resistor to test whether the switch assembly is actuated in response to a detected current flowing through the shunt resistor exceeding a predetermined threshold representative of potential damage to one of the transformer or the DC blocking circuit. ### Claim 15 (depends on 14) The self-testing system of claim 14, wherein the predetermined threshold represents a simulated geomagnetic induced quasi-dc current (GIC) or electromagnetic pulse (EMP-E3) quasi-dc current. ### Claim 16 (depends on 15) The self-testing system of claim 15, wherein the self-testing system sends an alarm in response to failure of the switching assembly to actuate in response to the detected current. ### Claim 17 (depends on 4) The self-testing system of claim 4, wherein the DC blocking component comprises a resistor and a capacitor bank. ### Claim 18 A self-testing system for use within an electrical protection circuit comprising: the electrical protection circuit electrically connected between a neutral of a transformer and a ground, the transformer electrically connected to a power grid, wherein the electrical protection circuit includes a spark gap assembly; a first switch electrically connected between the transformer neutral and the spark gap assembly; a high voltage source; a second switch, wherein the high voltage source and the second switch are electrically connected in series with each other and in parallel with the spark gap assembly; wherein, when the second switch is closed and the first switch is opened, a test high voltage is injected across the spark gap assembly to determine a breakdown voltage of the spark gap assembly. ### Claim 19 (depends on 18) The self-testing system of claim 18, further comprising: a switch assembly test circuit comprising: a switch-testing voltage source; a test actuation switch electrically connected between the switch-testing voltage source, and a location between the shunt resistor and the switch assembly, wherein, when the test actuation switch is closed, a test current is applied across the shunt resistor to test whether the switch assembly is actuated in response to a detected current flowing through the shunt resistor exceeding a predetermined threshold representative of potential damage to one of the transformer or the DC blocking circuit. ### Claim 20 A method for testing an electrical protection circuit electrically connected to a transformer, the method comprising: opening an automated motorized or manual grounding switch connecting the electrical protective circuit to the transformer; closing a switch connecting a test circuit to a DC blocking component; generating a voltage across the DC blocking component; measuring an impedance of the DC blocking component; comparing the impedance measured to an expected design value of the DC blocking component. ### Claim 21 (depends on 20) The method of claim 20, further comprising; closing a second electronic switch connecting a second test circuit to a spark gap assembly; generating a high voltage across the spark gap assembly; determining a breakdown voltage of the spark gap assembly. ### Claim 22 (depends on 21) The method of claim 21, further comprising: closing a third electronic switch connecting a third test circuit to a shunt resistor; generating a test current to flow through the shunt resistor; detecting a voltage across the shunt resistor exceeding a predetermined threshold representative of potential damage to one of the transformer or the DC blocking circuit; opening a switch assembly in response to the detected voltage exceeding the predetermined threshold.