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Operating Power

Three-phase ac is applied to the power isolation transformer to provide operating power to the regulated

power supply and the semiconverter power rectifier bridge.

When the generator is placed into operation, residual voltage will pass through the normally closed contacts

of K1. It is then rectified and applied to the generator field. When the generator output voltage builds up to

a sufficient value, K1 (connected across the output of the regulator power supply) energizes, and the

contacts open, removing the voltage build-up circuits. Thereafter, the power bridge output is established by

the gating pulses from the firing circuits. The minimum residual voltage required for build-up without flashing

is approximately 5% of nominal.

Flash and Overflash Protection (SSE 250 Series Only)

This circuit provides 125 Vdc to the generator field during start-up. When the generator output voltage rises

to 35% of nominal, the flashing voltage is removed and the static exciter regulator takes over. If the output

voltage does not build up in 25 seconds, the flashing voltage removed by the overflash protection circuitry.

Introduction

The Basler Electric Shunt-Static Exciter-Regulator (SSE) controls and regulates the generator output

voltage by controlling the generator field voltage. Standard features include underfrequency or volt/hertz

operation, manual control, and provisions for paralleling. The capabilities and parameters of each model

are detailed in Table 1-1. A power input transformer is supplied as a part of the SSE.

Options

The list of options described below contains some of the options that are available on all units and may be

on your unit.

• Failed rectifier detector

• Auto / manual nulling meter

• Manual tracking motor operated potentiometer

• Over / under excitation limiting

• AC shut-down contactor

• Field flashing contactor

• Paralleling current transformers

• VAR / power factor controller

• Primary fusing for power transformer when sold in cubicle

• Metering

• Potential transformer

• Cubicles

• MOC potentiometers

• Overexcitation protective relay

• Underexcitation protective relay

Model and Style Number

Electrical characteristics and operational features included in a specific relay

are defined by a combination of letters and numbers that make up the style

number. Model number BE1-46N designates the relay as a Basler Electric

Negative Sequence Overcurrent Relay. The model number, together with

the style number, describes the options included in a specific device and

appears on the front panel, draw-out cradle, and inside the case assembly.

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.

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.

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 (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.