Field reference for grid scale battery storage technicians. 14 entries, taken from the StoreWatt app.
Reference notes from StoreWatt, the offline field toolkit for grid scale battery energy storage technicians. It works with no cell signal, because the sites do not have any.
Get StoreWatt on the App StoreEverything in this category describes equipment on the medium voltage side of the plant: relays, reclosers, transformers, and switchgear. All of it is qualified person, arc flash program, switching order, and lockout tagout territory. This reference exists so technicians can speak the protection language and gather the right information for the protection engineer, not so anyone opens MV gear.
No MV switching or access without qualification, a switching order, and the site arc flash program. Gather relay targets and event records through the HMI or the engineer.
Device 25 supervises closing a breaker across two live sources: voltage magnitude, angle, and slip must be inside limits. On BESS plants it guards the interconnection breaker and any point where the plant can be paralleled with the grid. A breaker that refuses to close after an outage often has a healthy 25 doing its job on mismatched sources.
Device 27 operates when voltage falls below a setting for a set time. At the interconnection it enforces ride through boundaries; inside the plant it protects motors and auxiliaries from brownout. Plantwide 27 operations with the same timestamp are grid events; a single unit's 27 alone is a measurement or connection issue on that unit.
Device 32 watches power direction. On storage plants direction reverses legitimately with charge and discharge, so 32 elements guarding transformers or interconnection points must be coordinated with storage operation in mind; badly set 32 protection trips a plant for doing its job. Document the intended power flow directions at every 32 element during commissioning.
Device 46 detects current unbalance, the signature of open phases, bad connections, and unbalanced faults. Rising negative sequence on a feeder that used to be clean is an early warning of a failing connection worth thermography before it becomes an outage.
Device 50 trips with no intentional delay above its pickup: the close in fault element. A 50 target after an event means a large fault current flowed near that relay, which narrows the physical search area immediately.
Device 51 trips on an inverse time curve: higher current, faster trip. Coordination between 51 curves is what makes only the nearest breaker open for a fault. A 51 target with a long time to trip suggests overload rather than a bolted fault.
Device 59 operates on high voltage. On storage sites, overvoltage events cluster around light load, capacitor switching, and reactive power misbehavior; a plant absorbing or producing the wrong reactive power can drive its own 59 operations at the POI.
Device 81 operates on frequency deviations, over (81O) or under (81U). Frequency is systemwide, so genuine 81 operations hit the whole plant with matching timestamps. IEEE 1547 ride through settings decide how long the plant hangs on before 81 elements act.
Device 86 latches after a serious protection operation and blocks reclosing until manually reset. It exists to force a human decision after faults that must not be retried, like differential or transformer faults. An 86 target means something upstream considered the event serious. Resetting an 86 without understanding what tripped it defeats its entire purpose.
Identify and clear the initiating protection operation with the protection engineer before any 86 reset.
Device 87 compares current entering and leaving a protected zone (transformer, bus, cable); a difference means an internal fault. Differential operations are high confidence indications of real damage inside the zone and almost always drive an 86 lockout. Do not re energize a zone after an 87 operation until the equipment has been inspected and tested.
Treat the protected zone as damaged until proven otherwise. Inspection and testing come before any re energization decision.
Schweitzer relays dominate North American plant protection. Field gold: the event report, a high resolution capture of every operation, and the sequential events recorder. Front panel targets identify which elements operated; the engineer pulls event records over serial or Ethernet. Technician role: record the targets and timestamps before anyone resets anything, and never change settings; settings are the protection engineer's stamped work.
Element names and target displays vary by relay model. The installed relay's instruction manual governs.
The other common relay families: GE Multilin (UR and 8 series) with strong motor and feeder lines, Siemens SIPROTEC widespread on European built plants, and Basler in generation and interconnection roles. All offer event records and oscillography like SEL, each with its own tooling. The universal rule holds across brands: capture targets and event data first, reset second, and leave settings to the protection engineer.
Reclosers on the collection or interconnection line try to clear transient faults by reclosing automatically; on a storage plant their reclose settings must respect the PCS anti islanding behavior. The main power transformer carries differential and sudden pressure protection whose operation is always serious. The revenue meter at the POI is the financial truth: when SCADA and the revenue meter disagree, settlements follow the meter, so meter communication failures are revenue events, not just data events.
Reference notes from StoreWatt, the offline field toolkit for grid scale battery energy storage technicians. It works with no cell signal, because the sites do not have any.
Get StoreWatt on the App StoreThese notes are a field aid, not a substitute for the governing codes, the stamped drawings, the authority having jurisdiction, or manufacturer manuals. Verify against the current documentation for your installed equipment.