Search results
Results From The WOW.Com Content Network
A residual-current device (RCD), residual-current circuit breaker (RCCB) or ground fault circuit interrupter (GFCI) [a] is an electrical safety device, more specifically a form of Earth-leakage circuit breaker, that interrupts an electrical circuit when the current passing through line and neutral conductors of a circuit is not equal (the term residual relating to the imbalance), therefore ...
A shunt-trip unit appears similar to a normal breaker and the moving actuators are ganged to a normal breaker mechanism to operate together in a similar way, but the shunt trip is a solenoid intended to be operated by an external constant-voltage signal, rather than a current, commonly the local mains voltage or DC. These are often used to cut ...
An asymmetric or unbalanced fault does not affect each of the phases equally. Common types of asymmetric fault, and their causes: line-to-line fault - a short circuit between lines, caused by ionization of air, or when lines come into physical contact, for example due to a broken insulator.
At two multiples of the rated current, the recloser's rapid trip curve can cause a trip (off circuit) in as little as 1.5 cycles (or 30 milliseconds). During those 1.5 cycles, other separate circuits can see voltage dips or blinks until the affected circuit opens to stop the fault current.
Another cause of nuisance tripping is due to accumulated or burden currents caused by items with lowered insulation resistance. This may occur due to older equipment, or equipment with heating elements, or even wiring in buildings in the tropics where prolonged damp and rain conditions can cause the insulation resistance to lower due to ...
In electrical engineering, a protective relay is a relay device designed to trip a circuit breaker when a fault is detected. [ 1 ] : 4 The first protective relays were electromagnetic devices, relying on coils operating on moving parts to provide detection of abnormal operating conditions such as over-current, overvoltage , reverse power flow ...
An automatic trip is an action performed by some system, usually a safety instrumented system, programmable logic controller, or distributed control system, to put an industrial process into a safe state. It is triggered by some parameter going into a pre-determined unsafe state.
The resulting force accelerates the moving part, thus increasing the energy available for tripping. With this interrupting principle it is possible, during high-current interruptions, to increase by about 30% the tripping energy delivered by the operating mechanism and to maintain the opening speed independently of the current.