Basler Electric BE1-47N NEGATIVE SEQUENCE VOLTAGE RELAY

The BE1-47N Voltage Phase Sequence Relay provides protection for rotating equipment

from the damaging effects of excessive negative sequence voltage resulting from phase

failure, phase unbalance and reversed phase sequence.

ADVANTAGES

• Responds to true negative sequence voltage component.

• Unaffected by frequency variations of ±5 Hz.

• Negative Sequence Voltage adjustment range of 2 - 32 percent.

• Optional Over and Undervoltage measuring elements.

• Low sensing and supply burdens.

• Instantaneous, Definite and Inverse time delay characteristics available for

each measuring element.

• Qualified to the requirements of

— IEEE C37.90.1-1989 and IEC 255 for surge withstand capability;

— IEC 255-5 for impulse.

• UL recognized per Standard 508. UL File #E97033.

• Gost R certified per the relevant standards of Gosstandart of Russia

• Five year warranty.

APPLICATION

PURPOSE

The BE1-47N is designed to protect three-phase ma

chines against damage caused by phase failure, reverse

phase sequence phase unbalance, undervoltage and

overvoltage.

The BE1-47N responds to the negative sequence voltage

which results from a fault or misconnection on a balanced

three-phase system.

The BE1-47N detects reverse phase connection of lines,

transformers, motors, generators, and synchronous con

densers and is often applied in automatic transfer schemes

to assure connection of proper phase rotation as well as

voltage conditions. The Negative Sequence Voltage Re

lay is recommended for all important buses supplying

motor loads. When used in motor protection, the relay will

provide protection by preventing start-up of the motor for

open phase or reverse phase conditions and by tripping

the motor off-line for phase unbalance, undervoltage or

overvoltage conditions.

Negative sequence voltage is the result of any unequal

phase condition. This can be due to unequal single-phase

loads on the system or unequal transformer impedances

between the phases. A 1% - 2% negative sequence level

can normally be expected in an industrial supply. Any

significant increase above this level is an indication of a

power service problem that could lead to serious plant

problems. The BE1-47N has the ability to detect negative

sequence voltage levels of this magnitude.

Undervoltage and voltage balance relays have tradition

ally been applied for the protection of induction motors

from operating with one phase open. These relays may

not reliably detect this condition due to the back emf of

the motor on the open phase. However, an induction

motor, with a starting current of 6 per unit, will generate

a negative sequence voltage of 16% if fully loaded when

a fuse blows. The negative sequence voltage will be

somewhat reduced if the motor is not fully loaded. The

sensitivity of the BE1-47N and its insensitivity to fre

quency will provide reliable protection for motors.

Motor losses and current unbalance increase with the

negative sequence voltage level. The increased loss,

due to negative sequence voltage, is not a function of

motor load but is independent. A machine operating

with 3.5% negative sequence voltage will have its stated

losses increased by 25%. A blown fuse on a power factor

correction capacitor bank can result in a negative se

quence voltage increase. The increase in motor losses

can be costly.

The BE1-47N should be applied to protect motor buses

from a open phase. It can also be applied to protect

critical individual motors, static and non-rotating loads

from the effects of negative sequence voltage.

A choice of time delay characteristics allows the relay to

respond in the desired manner for a wide variety of

transient and fault conditions.

The BE1-47N may also be used to provide over/

undervoltage protection. A separate time delay is uti

lized to prevent shutdown of equipment for minor volt

age dips and to permit sequential operation when the

relay is being used in a supervisory capacity.