Basler Electric BE1-50 INSTANTANEOUS OVERCURRENT RELAY BE1-50-51B-107

BE1-46N Negative Sequence Overcurrent Relays are three-phase solid

state relays designed to provide protection for generators and motors

from unbalanced loading or power system faults. These relays protect

the machinery from damage when the protective scheme or other

equipment, external to the generator, fails to eliminate the unbalanced

condition.

BE1-46N Negative Sequence Overcurrent Relays accurately monitor the

magnitude and control the duration of the negative sequence current

component. These relays incorporate a time delay that replicates the

machinery heating and cooling characteristics.

An alarm element in the relays may be used to provide time to locate

and isolate the fault. Doing this avoids damage to the machinery, prevents

an undesired trip, and precludes a potentially prolonged outage of the

machinery.

BE1-46N relays are designed for use with any poly-phase generating

system having known (I2)2t limits between 1 and 99. Relays that operate

using phase currents to determine the negative sequence component are

phase rotation sensitive. BE1-46N relays are phase rotation sensitive.

Principles of Symmetrical Components

Principles of symmetrical components allow an unbalanced system to be

considered as three separate, balanced subsystems. These balanced

subsystems may then be analyzed as single phase quantities.

These quantities are the positive, negative, and zero sequence components

of current and voltage.

The positive sequence component of current (I1) represents the portion of

the total current which has normal phase rotation and produces no adverse

effect on the system. An ideally balanced system contains only positive

sequence phase currents and voltages.

The zero sequence component of current (I0) also has no adverse effect

on a three-phase, three-wire (no neutral connection) power system because

it produces no appreciable magnetic flux and causes no excessive heating

in the generator rotor or windings.

The negative sequence component of current (I2) produces a magnetic flux

in the stator that has the same rotational speed as the rotor flux, but in the

opposite direction. This causes the stator magnetic flux to rotate at twice

the system frequency and induce eddy currents into the rotor. These eddy

currents create excessive heat in the rotor iron and windings, and, if allowed

to persist, could result in severe damage to the system.

Generator and Bus Protection and Metering

Multifunction protection guards against overvoltage, undervoltage,

excessive forward and reverse power, underfrequency, and

overfrequency. Overcurrent, phase imbalance, loss of mains,

frequency rate-ofchange, phase differential, and neutral differential

protection are available as options. Each protection function has

an adjustable pickup and time delay setting.

Sixteen inverse time curves, in addition to user programmable

curves, enable the DGC-2020HD to offer overcurrent protection in

a variety of applications. Each protective element can be assigned

to protect the generator, bus 1. or bus 2 sensing inputs with settings

groups.

Metered generator and bus parameters include voltage, current,

frequency, vector shift, real power (watts), apparent power (VA),

and power factor (PF).