# US 6,774,803 B1 · Fault trip indicator and maintenance method for a circuit breaker > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 6,774,803 B1 - Document ID: US6774803B1 - Status: Granted - Kind: B1 - Application number: 10/160,644 - Filed: 2002-05-31 - Granted: 2004-08-10 - Earliest claimed: 2002-05-31 - Assignees: Ameren Corporation - Inventors: Randolph G. Tiffin - Web page: https://patentgrep.com/patent/US6774803B1 ## CPC - H01H 1/0015: {Means for testing or for inspecting contacts, e.g. wear indicator (measuring circuits G01R31/3274)} - H01H: ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES (contact cables H01B7/10; electrolytic self-interrupters H01G9/18; emergency protective circuit arrangements H02H; switching by electronic means without contact-making H03K17/00) ## Abstract A fault trip indicator for use with a circuit breaker connected to protect an electrical line comprises a current transformer coupled to the electrical line to produce a current signal which varies as a function of the current level in the electrical line. A threshold detector is coupled to the current transformer to produce a load signal when the threshold detector detects that the current signal exceeds a threshold value. A monitoring circuit is coupled to the protective circuit in the circuit breaker and the threshold detector to provide an indication of the occurrence of the protective circuit opening the circuit breaker while the threshold detector is producing the load signal. A fault trip indicator using passive circuitry, a battery powered threshold detector and binary load signals are also disclosed. A counter for counting the number of fault trips and a display for displaying the count are also disclosed, as are an auxiliary current transformer coupled to the main current transformer in the circuit breaker to provide the current signal. A method of performing maintenance on a circuit breaker is also disclosed. Other embodiments and features are also disclosed. ## Claims ### Claim 1 A fault trip indicator for use with a circuit breaker connected to protect an electrical line, the circuit breaker having a protective circuit for opening the circuit breaker during a heavy load condition on the electrical line, the protective circuit including a main current transformer for sensing a current level flowing through the electrical line, the fault trip indicator comprising: an auxiliary current transformer coupled to the main current transformer to produce a current signal which varies as a function of a current level produced by the main current transformer; a threshold detector coupled to the auxiliary current transformer to produce a load signal when the threshold detector detects that the current signal exceeds a threshold value; and a monitoring circuit coupled to the protective circuit and the threshold detector for providing an indication of the occurrence of the protective circuit opening the circuit breaker while the threshold detector is producing the load signal. ### Claim 2 (depends on 1) The fault trip indicator of claim 1 wherein the monitoring circuit comprises a counter for storing a count, wherein the counter increments the count in response to the occurrence of the protective circuit opening the circuit breaker while the threshold detector is producing the load signal. ### Claim 3 (depends on 2) The fault trip indicator of claim 2 further comprising a display coupled to the counter for displaying a number as a function of the count stored in the counter. ### Claim 4 (depends on 3) The fault trip indicator of claim 3 wherein the threshold value is a value which falls in a range from 5 amperes to 20 amperes. ### Claim 5 (depends on 1) The fault trip indicator of claim 1 wherein the monitoring circuit comprises a remote terminal unit coupled to the protective circuit, the threshold detector and a communication line; wherein the remote terminal unit produces a signal on the communication line each time the monitoring circuit provides an indication of the occurrence of the protective circuit opening the circuit breaker while the threshold detector is producing the load signal. ### Claim 6 (depends on 1) The fault trip indicator of claim 1 wherein the threshold value is a value which falls in a range from 5 amperes to 20 amperes. ### Claim 7 (depends on 1) The fault trip indicator of claim 1 wherein the threshold value is a value which falls in a range from 7.5 amperes to 15 amperes. ### Claim 8 (depends on 1) The fault trip indicator of claim 1 wherein the threshold value is a value which is at or above 10 amperes. ### Claim 9 (depends on 1) The fault trip indicator of claim 1 wherein the threshold detector comprises a passive circuit which consumes substantially no power at a time when the current signal does not exceed the threshold value. ### Claim 10 (depends on 1) The fault trip indicator of claim 1 wherein the electrical line further comprises a neutral line; and wherein the main current transformer is coupled to the neutral line. ### Claim 11 (depends on 1) The fault trip indicator of claim 1 wherein the electrical line further comprises a three phase line; and wherein: the fault trip indicator further comprises a plurality of auxiliary current transformers; a separate auxiliary current transformer is coupled to each of the separate phases; and the threshold detector is coupled to each of the separate auxiliary current transformers and produces the load signal when the threshold detector detects that a current signal produced by one of the separate auxiliary current transformers exceeds the threshold value. ### Claim 12 (depends on 1) The fault trip indicator of claim 1 wherein the current signal produced by the auxiliary current transformer has either a positive or a negative polarity; and wherein the threshold detector produces the load signal when the threshold detector detects that the positive or negative polarity current signal exceeds the threshold value. ### Claim 13 (depends on 1) The fault trip indicator of claim 1 wherein the threshold detector further comprises a reed relay which closes to produce the load signal. ### Claim 14 (depends on 1) The fault trip indicator of claim 1 wherein the threshold detector further comprises an opto-isolator which becomes conductive to produce the load signal. ### Claim 15 A fault trip indicator for use with a circuit breaker connected to protect an electrical line, the circuit breaker having a protective circuit for opening the circuit breaker during a heavy load condition on the electrical line, the fault trip indicator comprising: a current transformer coupled to the electrical line to produce a current signal which varies as a function of a current level flowing through the electrical line; a battery-powered threshold detector coupled to the current transformer to produce a load signal when the threshold detector detects that the current signal exceeds a threshold value; and a monitoring circuit coupled to the protective circuit and the threshold detector for providing an indication of the occurrence of the protective circuit opening the circuit breaker while the threshold detector is producing the load signal. ### Claim 16 (depends on 15) The fault trip indicator of claim 15 wherein the circuit breaker comprises a main current transformer coupled to the electrical line and wherein the current transformer comprises an auxiliary current transformer coupled to the main current transformer. ### Claim 17 (depends on 15) The fault trip indicator of claim 15 wherein the monitoring circuit comprises a counter for storing a count, wherein the counter increments the count in response to the occurrence of the protective circuit opening the circuit breaker while the threshold detector is producing the load signal. ### Claim 18 (depends on 17) The fault trip indicator of claim 17 further comprising a display coupled to the counter for displaying a number as a function of the count stored in the counter. ### Claim 19 (depends on 18) The fault trip indicator of claim 18 wherein the threshold value is a value which falls in a range from 5 amperes to 20 amperes. ### Claim 20 (depends on 15) The fault trip indicator of claim 15 wherein the threshold value is a value which falls in a range from 7.5 amperes to 15 amperes. ### Claim 21 A fault trip indicator for use with a circuit breaker connected to protect an electrical line, the circuit breaker having a protective circuit for opening the circuit breaker during a heavy load condition on the electrical line, the fault trip indicator comprising: a current transformer coupled to the electrical line to produce a current signal which varies as a function of a current level flowing through the electrical line; a threshold detector coupled to the current transformer to produce a binary load signal when the threshold detector detects that the current signal exceeds a threshold value; and a monitoring circuit coupled to the protective circuit and the threshold detector for providing an indication of the occurrence of the protective circuit opening the circuit breaker while the threshold detector is producing the binary load signal. ### Claim 22 (depends on 21) The fault trip indicator of claim 21 wherein the circuit breaker comprises a main current transformer coupled to the electrical line and wherein the current transformer comprises an auxiliary current transformer coupled to the main current transformer. ### Claim 23 (depends on 21) The fault trip indicator of claim 21 wherein the monitoring circuit comprises a counter for storing a count, wherein the counter increments the count in response to the occurrence of the protective circuit opening the circuit breaker while the threshold detector is producing the load signal. ### Claim 24 (depends on 23) The fault trip indicator of claim 23 further comprising a display coupled to the counter for displaying a number as a function of the count stored in the counter. ### Claim 25 (depends on 24) The fault trip indicator of claim 24 wherein the threshold value is a value which falls in a range from 5 amperes to 20 amperes. ### Claim 26 (depends on 21) The fault trip indicator of claim 21 wherein the threshold value is a value which falls in a range from 7.5 amperes to 15 amperes. ### Claim 27 A fault trip indicator for use with a circuit breaker connected to protect an electrical line, the circuit breaker having a protective circuit for opening the circuit breaker during a heavy load condition on the electrical line, the fault trip indicator comprising: a current transformer coupled to the electrical line to produce a current signal which varies as a function of a current level flowing through the electrical line; a passive threshold detector coupled to the current transformer to produce a load signal when the threshold detector detects that the current signal exceeds a threshold value; and an indicator coupled to the protective circuit and the threshold detector to provide an indication of the occurrence of the protective circuit opening the circuit breaker while the threshold detector is producing the load signal. ### Claim 28 A method of performing maintenance on a circuit breaker, the circuit breaker being connected to protect an electrical line and being of a type having a protective circuit for opening the circuit breaker during a heavy load condition on the electrical line, the method comprising: producing a current signal which varies as a function of a current level flowing through the electrical line; establishing a first threshold value; producing a binary load signal as a function of the current signal and the first threshold value; providing an indication of the occurrence of the protective circuit opening the circuit breaking while the binary load signal is being produced; establishing a second threshold value; and performing maintenance on the circuit breaker as a function of the indication and the second threshold value. ### Claim 29 (depends on 28) The method of claim 28 wherein the providing element further comprises: storing a count; and incrementing the stored count in response to the occurrence of the opening of the circuit breaker while the binary load signal is being produced; wherein the performing element further comprises performing maintenance on the circuit breaker as a function of the stored count and the second threshold value. ### Claim 30 A method of performing maintenance on a circuit breaker, the circuit breaker being connected to protect an electrical line and being of a type having a protective circuit for opening the circuit breaker during a heavy load condition on the electrical line, the method comprising: producing a current signal which varies as a function of a current level flowing through the electrical line; establishing a first threshold value; using battery power to produce a load signal as a function of the current signal and the first threshold value; providing an indication of the occurrence of the protective circuit opening the circuit breaking while the load signal is being produced; establishing a second threshold value; and performing maintenance on the circuit breaker as a function of the indication and the second threshold value. ### Claim 31 (depends on 30) The method of claim 30 wherein the providing element further comprises: storing a count; and incrementing the stored count in response to the occurrence of the opening of the circuit breaker while the load signal is being produced; wherein the performing element further comprises performing maintenance on the circuit breaker as a function of the stored count and the second threshold value.