The other is that an operator failed to switch on protective relays that would have limited any problem with the new equipment to the substation.
22.
Light and current based protection can be set up with dedicated arc-flash protective relays, or by using normal protective relays equipped with an add-on arc-flash option.
23.
Light and current based protection can be set up with dedicated arc-flash protective relays, or by using normal protective relays equipped with an add-on arc-flash option.
24.
While the operating quality of these devices, and especially of protective relays, is always critical, different strategies are considered for protecting the different parts of the system.
25.
Circuit breakers for large currents or high voltages are usually arranged with protective relay pilot devices to sense a fault condition and to operate the opening mechanism.
26.
For example, an overcurrent protective relay may have a AC to DC power supply for the input circuit, a level detector circuit and an RC time delay circuit.
27.
Digital protective relays and some PLCs now also include time-tagging to the nearest millisecond; SCADA systems that incorporate these devices provide SER functions without a dedicated SER device.
28.
These typically require a separate power source, such as a battery, although some high-voltage circuit breakers are self-contained with current transformers, protective relays, and an internal control power source.
29.
Automatic protective relays detect the high current and quickly act to disconnect the faulted line, and the load previously carried by the disconnected line is transferred to other lines.
30.
PEARL's standards for inspecting, testing and reconditioning electrical equipment, components and apparatus help ensure the reliable, safe operation of devices such as circuit breakers, transformers, switches, protective relays, and contactors.
