{ "node": { "id": "term:rate-of-change-of-frequency", "type": "Term", "label": "Rate of change of frequency", "properties": { "id": "rate-of-change-of-frequency", "name": "Rate of change of frequency", "abbr": "RoCoF", "section": "topic-applications", "definition": "How fast grid frequency moves after a sudden imbalance such as a large generator tripping. Grids with less rotating inertia see steeper slopes; Great Britain has relaxed its loss-of-mains protection settings from 0.125 Hz/s to 0.5–1 Hz/s. Fast battery response and grid-forming inverters that emulate inertia help keep it within limits.", "formula": "RoCoF = df/dt", "unit": "Hz/s", "related": [ "frequency-regulation", "inverter", "stationary-storage", "islanding" ], "example": { "title": "Measure a frequency slope", "text": "If measured grid frequency falls from 50.0 Hz to 49.8 Hz over 0.5 s, the average RoCoF is −0.4 Hz/s. Reporting windows and filtering affect the observed value." }, "url": "https://lemonergy.com/learn/glossary/rate-of-change-of-frequency/", "mentions": [] } }, "edges": [ { "id": "edge:6836", "source": "term:rate-of-change-of-frequency", "target": "topic:topic-applications", "type": "belongsTo", "properties": { "sourceFile": "terms.json" } }, { "id": "edge:6837", "source": "term:rate-of-change-of-frequency", "target": "term:frequency-regulation", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:6838", "source": "term:rate-of-change-of-frequency", "target": "term:inverter", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:6839", "source": "term:rate-of-change-of-frequency", "target": "term:stationary-storage", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:6840", "source": "term:rate-of-change-of-frequency", "target": "term:islanding", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:6841", "source": "term:rate-of-change-of-frequency", "target": "visual:grid-frequency", "type": "illustratedBy", "properties": { "sourceFile": "visual-pages.json" } } ], "neighbors": [ { "id": "topic:topic-applications", "type": "Topic", "label": "Applications and market", "properties": { "id": "topic-applications", "name": "Applications and market", "lede": "Where batteries are used, and the terms used to buy, size and compare them.", "context": "Start with mission energy, peak power and operating conditions.", "example": "20 kWh total energy and a ten-second 100 kW peak constrain different design aspects.", "lesson_url": "https://lemonergy.com/learn/fundamentals/capacity-and-c-rate/", "lesson_label": "Open energy and power" } }, { "id": "term:frequency-regulation", "type": "Term", "label": "Frequency regulation", "properties": { "id": "frequency-regulation", "name": "Frequency regulation", "aka": [ "ancillary services", "frequency response" ], "section": "topic-applications", "definition": "Rapidly injecting or absorbing power to hold the grid frequency at 50 or 60 Hz, a service batteries do better than any generator because they respond in milliseconds. It cycles the battery shallowly but very often.", "related": [ "stationary-storage", "energy-arbitrage", "specific-power", "equivalent-full-cycle", "rate-of-change-of-frequency" ], "url": "https://lemonergy.com/learn/glossary/frequency-regulation/", "mentions": [] } }, { "id": "term:inverter", "type": "Term", "label": "Inverter", "properties": { "id": "inverter", "name": "Inverter", "aka": [ "power conversion system", "PCS" ], "section": "topic-pack", "definition": "The power electronics that turn the battery’s DC into AC for a motor or the grid, and back again for charging. In stationary storage it is called the power conversion system and its rating in kW or MW sets the system’s power independently of the battery’s energy.", "related": [ "pre-charge", "dc-dc-converter", "stationary-storage", "energy-management-system", "direct-current", "iec-62477-1" ], "url": "https://lemonergy.com/learn/glossary/inverter/", "mentions": [] } }, { "id": "term:stationary-storage", "type": "Term", "label": "Stationary storage", "properties": { "id": "stationary-storage", "name": "Stationary storage", "abbr": "BESS", "aka": [ "battery energy storage system", "ESS" ], "section": "topic-applications", "definition": "Batteries installed in a fixed place — a container at a solar farm, a cabinet in a home — to shift energy in time or support the grid. LFP cells dominate because cost per cycle and safety matter more than mass.", "related": [ "lfp", "energy-management-system", "inverter", "energy-arbitrage", "long-duration-storage", "ul-9540a" ], "url": "https://lemonergy.com/learn/glossary/stationary-storage/", "mentions": [] } }, { "id": "term:islanding", "type": "Term", "label": "Islanding", "properties": { "id": "islanding", "name": "Islanding", "aka": [ "island mode", "anti-islanding", "intentional islanding" ], "section": "topic-infrastructure", "definition": "Part of the network, such as a house with solar and a battery, staying energised while disconnected from the main grid. Intentional islanding, behind a transfer switch with a grid-forming inverter, provides backup power; unintentional islanding endangers line workers, so IEEE 1547 requires inverters to detect it and cease energising the grid within two seconds.", "related": [ "microgrid", "inverter", "smart-load-panel", "stationary-storage", "vehicle-to-everything" ], "url": "https://lemonergy.com/learn/glossary/islanding/", "mentions": [] } }, { "id": "visual:grid-frequency", "type": "Visual", "label": "RoCoF is the local frequency slope", "properties": { "title": "RoCoF is the local frequency slope", "summary": "A linear frequency segment has a constant rate of change.", "readout": "The selected slope is -0.5 Hz/s; after 2 s the authored frequency is 49 Hz.", "formula": "RoCoF = df/dt", "note": "A short illustrative line, not a power-system response or protection-setting recommendation.", "software": { "status": "reference", "label": "Reference concept", "body": "This explains frequency slope. Native Studio charging examples use average power boundaries and do not simulate grid frequency, inertia or protection behavior.", "href": "../chapter-1/" }, "html": "
Authored frequency excursion
Authored frequency excursionElapsed time (s) versus Grid frequency (Hz). f(t) = 50 + slope × t. Interpretation follows the graphs.480490.5501511.5522Elapsed time (s)Grid frequency (Hz)
f(t) = 50 + slope × t
" } } ] }