BE1-46N General Information
1-1
SECTION 1 • GENERAL INFORMATION
DESCRIPTION
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 (I
2
)
2
t 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 (I
1
) 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 (I
0
) 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 (I
2
) 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.
MODEL AND STYLE NUMBER
Electrical characteristics and operational features included in a specific relay are defined by a combination
of letters and numbers that constitute the device style number. The model number, BE1-46N, designates
the relay as a Basler Electric Class 100 Negative Sequence Overcurrent Relay. The style number together
with the model number describe the features and options in a particular device and appear on the front
panel, drawout cradle, and inside the case assembly.
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