Passive wireless sensors for prevention of arcing failures in protective circuits

Arc flash hazards are a major concern for electric power transmission and distribution systems worldwide, as are outages caused by equipment failure. The underlying causes of failure in the protective circuitry of electric power systems are generally either mechanical failure or insulation failure. Joints loosened through repeated temperature cycling in circuit breakers can lead to overheating and breakdown of insulation, causing arcing and, for certain insulators such as oil that form flammable gases, explosions. In substations, high voltage switchgear and oil insulated circuit breakers tend to fail more often than oil- immersed transformers, although the latter are also dangerous. Voltage transients leading to internal flashover above the oil can be caused by sparking at loose connections, badly made joints, fractured conductors, and potentially hot joints and connections. Shorts between conductors in transformer turns can also be problematic, though this type of fault can go undetected by standard protective circuits. All of the failure modes described above share one common feature – thermal excursions precede subsequent component failure. Thermal monitoring of connections to detect increases in component temperature beyond normal operating conditions would allow detection of incipient failures. Yet today arc flash protection equipment focuses on controlling the damage caused by the arc flash event, rather than trying to prevent it from occurring. There is no effective, affordable commercially available method to continuously monitor connections in electrical equipment to determine the status of the system. This project will establish the feasibility of producing low-cost solid-state wireless sensors that can be used to monitor the real-time temperature of medium voltage (MV) components that include switchgear, circuit breakers, and transformers (among others) to provide early warning of deteriorating conditions that, if left unchecked, could lead to arc flash damage. Analytics in a data aggregator will flag thermal excursions that may indicate deteriorating component conditions and provide appropriate alerts, enabling preventive maintenance prior to failure. Surface acoustic wave (SAW) temperature sensors operate without any batteries, using the energy contained in an RF signal to activate the sensor and reflect back sensor ID and measurements. Technical challenges to be addressed in Phase I include development of sensors, packaging and antenna configurations that are compatible with MV equipment, and development of sets of 12-20 (or more) sensors for simultaneous operation. Inclusion of other metrics (such as current) would enhance utility of the proposed sensors for equipment monitoring and control. Phase I will develop and test prototype sensors in enclosures relevant for MV grid components. Phase II would mature the technology to the level where product introduction shortly after Phase II completion is realistic. Arc flash hazards are a major concern for electric utilities and for all industries that involve the use and distribution of significant amounts of electricity, including the oil & gas industry and datacenters. Approximately 30,000 arc flash incidents occur annually (5-10 per day in the U.S. alone), resulting in thousands of burns and hospitalizations, numerous fatalities, and property damage worth millions of dollars. The proposed sensors will enable continuous condition monitoring in electric power distribution systems for a wide range of industries, enabling predictive maintenance to repair emerging problems before they turn into faults or generate arcs. Widespread use of such monitoring systems will enhance grid reliability, reduce equipment failures and outages, and significantly reduce the number of arc flash incidents, saving lives and avoiding substantial injuries and property damage.